U.S. Department of the Interior

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

OCS EIS/EA

BOEM 2016-049

Gulf of Mexico OCS 

Proposed Geological and Geophysical Activities

Western, Central, and Eastern Planning Areas

Draft Programmatic Environmental Impact Statement

Volume I: Chapters 1-8 

U.S. Department of the Interior

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

OCS EIS/EA

BOEM 2016-049

Gulf of Mexico OCS 

Proposed Geological and Geophysical Activities

Western, Central, and Eastern Planning Areas

Draft Programmatic Environmental Impact Statement

Volume I: Chapters 1-8 

Author

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

Prepared under

Contract No. GS-10F-0443M

and

Task Order No. M1PD00025

by

CSA Ocean Sciences Inc.

8502 SW Kansas Avenue

Stuart, Florida 34997

Published by 

New Orleans

September 2016 



v 

COVER SHEET

Programmatic Environmental Impact Statement 

for 

Gulf of Mexico OCS Proposed Geological and Geophysical Activities 

in the Gulf of Mexico

Draft (x) Final ( )

Type of Action: Administrative (x) Legislative ( )

Area of Potential Impact: Offshore Marine Environment and Coastal Counties of Texas, 

Louisiana, Mississippi, Alabama and Florida

Agency Headquarters’ Contact Region Contact

U.S. Department of the Interior

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

(GM 623E)

1201 Elmwood Park Boulevard

New Orleans, LA 70123-2394

Jill Lewandowski

U.S. Department of the Interior

Bureau of Ocean Energy Management

45600 Woodland Road (VAM-OEP) 

Sterling, VA 20166-9216 

703-787-1584

Gary Goeke

504-736-3233

ABSTRACT

This Draft Programmatic Environmental Impact Statement (EIS) covers the potential 

significant environmental effects of multiple geological and geophysical (G&G) activities on the Gulf 

of Mexico (GOM) Outer Continental Shelf (OCS) in the Western, Central, and Eastern Planning 

Areas (WPA, CPA, and EPA). It evaluates the types of G&G surveys and activities in the three 

program areas managed by the Bureau of Ocean Energy Management (BOEM): oil and gas; 

renewable energy; and marine minerals.

The proposed action is a major Federal action requiring an EIS. This document provides the 

following information in accordance with the National Environmental Policy Act (NEPA) and its 

implementing regulations, and it will be used in making decisions on the proposals. 

This Draft Programmatic EIS includes the purpose and background of the proposed action, 

identification of the alternatives, a scenario of the anticipated level of G&G activities in the program 

areas across the WPA, CPA, and EPA. A description of the factors and impacts caused by the 

proposed activities, a description of the affected environment, and an analysis of the potential 
vi

environmental impacts under routine and non-routine conditions for the proposed action and 

alternatives are analyzed. Activities and disturbances associated with the proposed action on 

biological, physical, and socioeconomic resources are considered in the analyses. The proposed 

mitigating measures and their potential effects are described. Also, the potential contributions to 

cumulative impacts resulting from activities associated with the proposed action are analyzed. 

It is important to note that this Draft Programmatic EIS was prepared using the best 

information that was publicly available at the time the document was prepared. Where relevant 

information on reasonably foreseeable significant adverse impacts is incomplete or unavailable, the 

need for the information was evaluated to determine if it was essential to a reasoned choice among 

the alternatives and, if so, was either acquired or in the event it was impossible or exorbitant to 

acquire the information, accepted scientific methodologies were applied in its place.

Additional copies of this Draft Programmatic EIS and the other referenced publications may 

be obtained from the Bureau of Ocean Energy Management, Gulf of Mexico OCS Region, Public 

Information Office (GM 335A), 1201 Elmwood Park Boulevard, New Orleans, Louisiana 

70123-2394, by telephone at 504-736-2519 or 1-800-200-GULF, or on the Internet at 

http://www.boem.gov/GOM-G-G-PEIS/ and http://www.boem.gov/nepaprocess/. 
Gulf of Mexico G&G Activities Programmatic EIS vii

EXECUTIVE SUMMARY

BACKGROUND

The Bureau of Ocean Energy Management (BOEM) is issuing this Programmatic 

Environmental Impact Statement (EIS) to describe and evaluate the potential environmental impacts 

related to geological and geophysical (G&G) survey activities in Federal and affected State waters of 

the Gulf of Mexico (GOM). The G&G surveys are conducted to provide data to inform business 

decisions about the development of oil and gas reserves, locate and evaluate marine mineral 

deposits, provide engineering data for developing renewable energy projects, identify geologic 

hazards and benthic habitats to avoid, and aid in the location and avoidance of archaeological sites. 

This Programmatic EIS evaluates G&G survey activities within program areas for which BOEM has 

oversight (i.e., oil and gas, renewable energy, and marine minerals) to investigate offshore oil, gas, 

methane hydrate resources, non-energy/marine mineral resources, and geologic hazards. The area 

in which G&G survey activities may occur are within the three GOM planning areas (i.e., the 

Western, Central, and Eastern Planning Areas [WPA, CPA, and EPA]).

This Programmatic EIS establishes a framework for BOEM to guide subsequent NEPA 

analyses of site-specific actions while identifying and analyzing appropriate mitigation measures to 

be used during future G&G activities on the Outer Continental Shelf (OCS) in support of oil and gas, 

renewable energy, and marine mineral resource programs. BOEM will address the impacts of future 

site-specific actions in subsequent National Environmental Policy Act (NEPA) evaluations (40 CFR § 

1502.20) using a tiering process based on this programmatic evaluation.

BOEM is the lead agency for this Programmatic EIS, with the Bureau of Safety and 

Environmental Enforcement (BSEE) and the National Oceanic and Atmospheric Administration 

(NOAA), National Marine Fisheries Service (NMFS) as cooperating agencies. BOEM is the lead 

Federal agency in providing guidelines for implementing oil and gas exploration and development, 

renewable energy, and marine minerals programs on the Gulf of Mexico OCS. BOEM and BSEE 

have a memorandum of agreement (MOA) stating that BSEE will serve as cooperating agency on 

Bureau of Ocean Energy Management NEPA documents, oversee any requisite environmental 

monitoring needs, and ensure that post-activity environmental compliance needs are met and 

documented. The NMFS is a cooperating agency for this Programmatic EIS because the scope of 

the proposed action and alternatives involve G&G survey activities that could impact living marine 

resources and because the NMFS is the lead Federal agency in managing and regulating marine 

mammals and sensitive marine species, including those listed or proposed for listing as threatened 

or endangered under the Marine Mammal Protection Act (MMPA) and the Endangered Species Act 

(ESA).

This summary provides an overview of the analysis of the proposed action and other 

alternatives that would allow BOEM to authorize G&G activities within the GOM where it has 

oversight. The details of the analysis conducted for each alternative and program area can be found 

in the main body of this Programmatic EIS. Additional supporting information can be found in the 

appendices. The main body of this Programmatic EIS contains the following chapters:
viii Executive Summary

• Chapter 1 (Introduction) describes the purpose, objectives, and scope of this

Programmatic EIS; describes the role of BOEM, BSEE, and cooperating 

agencies; provides background information; reviews the Deepwater Horizon

explosion, oil spill, and response; and explains the regulatory context of this

Programmatic EIS.

• Chapter 2 (Alternatives Including the Proposed Action) describes the seven 

alternatives evaluated (including the proposed action), the survey protocols and 

mitigation measures included in all of the alternatives, and issues to be analyzed; 

identifies alternatives not analyzed and mitigation measures not included; 

presents a comparison of impacts by alternative; discusses the implementation of 

adaptive management; and describes mitigation measures, monitoring, and 

effectiveness.

• Chapter 3 (G&G Activities and Proposed Action Scenario) describes the 

G&G activities included in each program area and the expected level of effort 

during the period covered by this Programmatic EIS (10-year period), identifies 

and describes the impact-producing factors (IPFs), and provides a cumulative 

activity scenario for impact analysis.

• Chapter 4 (Description of the Affected Resources and Impact Analysis)

describes the affected environment and analyzes the potential impacts of each 

alternative.

• Chapter 5 (Other NEPA Considerations) describes the unavoidable adverse 

impacts, irreversible and irretrievable commitment of resources, and the 

relationship between short-term uses and long-term productivity.

• Chapter 6 (Public Involvement and Agency Consultation and Coordination)

describes the consultation and coordination activities with Federal, State, and 

local agencies, federally recognized Indian Tribes, and other interested parties 

that occurred during the development of this Programmatic EIS.

• Chapter 7 (Literature Cited) describes the technical information on which the 

analyses within this Programmatic EIS is based.

• Chapter 8 (Preparers and Reviewers) describes the technical staff within 

BOEM, BSEE, NMFS, and the contractors responsible for the content of this 

Programmatic EIS.

AREA OF INTEREST

The area evaluated (Area of Interest, or AOI) includes the OCS waters of the GOM and the 

waters above the OCS that are within the Bureau of Ocean Energy Management’s GOM planning 

areas (i.e., the WPA, CPA, and EPA). The AOI also includes the coastal waters of Texas, 

Louisiana, Mississippi, Alabama, and Florida, extending from the coastline (outside of estuaries) 

seaward 3 nautical miles (nmi) (3.5 miles [mi]; 5.6 kilometers [km]) (Louisiana, Mississippi, and 
Gulf of Mexico G&G Activities Programmatic EIS ix

Alabama) or 9 nmi (10.6 mi; 16.7 km) (Texas and Florida) to the limit of State jurisdiction 

(Figure ES-1).

Figure ES-1. Area of Interest for the Proposed Action.

To support the impact analysis, this Programmatic EIS includes resources that are found in 

or migrate through the AOI and adjacent areas and that may be affected by the proposed action. 

The AOI inner boundary follows the shoreline along most of the U.S. coast, extending across the 

mouths of estuaries and bays. State waters are not within BOEM’s jurisdiction; the U.S. Army Corps 

of Engineers (USACE) permits G&G activities in State waters. The USACE also has jurisdiction 

over such activities, including OCS seafloor structures, in State and Federal waters. Despite limits 

to its regulatory authority, BOEM is addressing adjacent State waters in this Programmatic EIS 

because

(1) the NMFS has jurisdiction and MMPA permitting authority in Federal and State 

waters, and requires an assessment of the potential impacts to the human 

environment;

(2) the acoustic energy introduced into the environment during G&G activities in 

Federal waters could affect resources in State waters; and

(3) G&G activities could include interrelated and connected activities in Federal and 

State waters that would be considered connected actions. 
x Executive Summary

TYPES OF G&G ACTIVITIES ANALYZED

A variety of G&G techniques, most of which use sound in some way, are used to 

characterize the shallow and deep structure of the OCS, including the shelf, slope, and deepwater 

ocean environment. The G&G surveys are conducted to (1) obtain data for hydrocarbon and mineral 

exploration and production; (2) aid in siting of oil and gas structures and facilities, renewable energy 

structures and facilities, and pipelines; (3) locate and monitor the use of potential sand and gravel 

resources for development; (4) identify possible seafloor or shallow-depth geologic hazards; and 

(5) locate potential archaeological resources and benthic habitats that should be avoided.

A variety of G&G techniques are used to characterize the shallow and deep structure of the 

shelf, slope, and deepwater ocean environments. In general, the activities include the following:

• types of deep-penetration seismic airgun surveys used almost exclusively for oil 

and gas exploration and development;

• other types of surveys and sampling activities used only in support of oil and gas 

exploration and development, including electromagnetic surveys, geological test 

wells, and various remote-sensing methods; 

• non-airgun high-resolution geophysical (HRG) surveys used in all three program 

areas to detect and monitor geohazards, archaeological resources, and certain 

types of benthic communities; and

• geological and geotechnical bottom sampling used in all three program areas to 

assess the suitability of seafloor sediments for supporting structures (e.g., 

platforms, pipelines, cables, renewable energy facilities such as wind turbines) or 

to evaluate the quantity and quality of sand for beach nourishment and coastal 

restoration projects.

The G&G activities in support of renewable energy development would consist mainly of 

HRG and geotechnical surveys in Federal and State waters less than 40 meters (m) (131 feet [ft]) 

deep. The G&G activities in support of marine mineral uses (e.g., sand and gravel mining) would 

consist mainly of HRG and geotechnical surveys in Federal and State waters less than 30 m (98 ft) 

deep. The G&G activities beyond the outer boundary of the planning areas have not been 

determined but could include geophysical surveys in support of the U.S. Extended Continental Shelf 

Project.

Deep-penetration seismic surveys are conducted almost exclusively in support of oil and gas 

exploration and development, and would be conducted in all three planning areas. For these 

surveys, vessels tow an airgun or an array of airguns that emit acoustic energy pulses through the 

overlying water then into the seafloor over long durations and over large areas. Thus, these surveys 

are one of the most extensive G&G activities that would be conducted and are one of the potentially 

impactful activities analyzed in this Programmatic EIS.
Gulf of Mexico G&G Activities Programmatic EIS xi

ALTERNATIVES

Seven alternatives (A through G) are analyzed in this Programmatic EIS. 

• Alternative A – Pre-Settlement (June 2013) Alternative: BOEM would 

continue to permit/authorize at the current projected activity levels with 

implementation of standard mitigation measures applied to G&G activities 

through lease stipulations, issued permits and authorizations as conditions of 

approvals (COAs), Notices to Lessees and Operators (NTLs), and/or best 

management practices in place prior to the June 2013 settlement agreement.

• Alternative B – Settlement Agreement Alternative: BOEM would continue to 

permit or authorize G&G activities through the use of site-specific NEPA 

evaluations, lease stipulations, NTLs, best management practices, and COAs 

with the addition of mitigation measures from the Settlement Agreement for Civil 

Action No. 2:10-cv-01882 dated June 25, 2013, and the Stipulation to Amend 

Settlement Agreement dated February 8, 2016. 

• Alternative C – Alternative A Plus Additional Mitigation Measures: BOEM 

would continue to authorize G&G activities that would include the mitigation 

measures, monitoring, reporting, survey protocols, and guidance that are 

included in Alternative A, as well as additional mitigation and temporal measures 

for survey protocols for seismic airgun and non-airgun HRG surveys.

• Alternative D – Alternative C Plus Marine Mammal Shutdowns: BOEM 

would authorize G&G activities and would include all of Alternatives A and C 

mitigation measures with the addition of shutdowns of airgun and HRG survey 

sound sources for all marine mammals within an exclusion zone excepting bowriding dolphins.

• Alternative E – Alternative C at Reduced Activity Levels: BOEM would 

authorize a reduced level of G&G activity for seismic airgun surveys under two 

options: Alternatives E1 and E2.

− Alternative E1 includes a 10 percent reduction in deep-seismic, multi-client 

activities.

− Alternative E2 includes a 25 percent reduction in deep-seismic, multi-client 

activities.

Under both Alternative E options, all Alternative C mitigation measures would be 

followed.

• Alternative F – Alternative C Plus Area Closures: BOEM would continue to 

permit G&G activities and require that operators comply with Alternative C 

mitigation requirements with the addition of area closures to provide additional

protection for certain cetaceans and other resources. The four closure areas are 
xii Executive Summary

a Central Planning Closure Area, an Eastern Planning Closure Area, the Dry 

Tortugas Closure Area, and the Flower Gardens Closure Area.

• Alternative G – No New Activity Alternative: BOEM would cease issuing 

permits for new G&G surveys and would not approve new G&G surveys 

proposed under exploration or development plans. However, G&G activities 

previously authorized under an existing permit or lease would proceed, but they 

would not be renewed or reauthorized and, thus, would eventually be phased 

out. The second part of Alternative G is the NMFS No Action Alternative. For 

the NMFS, denial of MMPA authorizations constitutes the NMFS No Action 

Alternative, which is consistent with the NMFS statutory obligation under the 

MMPA to grant or deny applications to authorize incidental take and to prescribe 

mitigation, monitoring, and reporting with any authorizations.

MITIGATION MEASURES

All G&G activities permitted under the alternatives would need to comply with existing laws 

and regulations. The alternatives are designed to minimize impacts to resources by avoiding the 

resource or by modification to the design of proposed G&G activities. In addition, during the MMPA 

authorization process, the NMFS may require additions or alterations to mitigation measures to 

minimize or avoid impacts to marine mammals. The mitigation measures that would be required 

under each alternative are given in Table ES-1. 
Gulf of Mexico G&G Activities Programmatic EIS xiii

Table ES-1 Applicability of Mitigation Measures to G&G Surveys by Alternative (indicates which mitigation measure is applicable to an 

alternative)

Survey Type Mitigation Measures Survey 

Protocol

Seasonal Restrictions 

and Closures

Vessel Strike AvoidanceMarine Debris GuidanceAvoidance of Sensitive Benthic Communities Avoidance of Historic and Prehistoric Sites Shallow Hazards GuidanceNMS Guidance Military CoordinationAncillary Activity GuidanceImplement PSO ProgramImplement Expanded PSO ProgramMinimum Separation DistanceReduced Level of ActivityUse of PAM Strongly EncouragedUse of PAM RequiredSeismic Airgun Survey ProtocolNon-Airgun HRG Survey ProtocolCoastal Waters Seasonal RestrictionAreas of Concern within the EPA8

Closure Areas: 

CP, EP, Dry Tortugas, Flower Gardens

Seismic Airgun Surveys A-G A-G A-G A-G1 A-G1 A-G A-G A-G A,G B-F2 

D3 B E A,G B-F4 C-F5 A-G -- B6 C-F7 B F 

HRG Non-airgun Surveys 

with Frequencies >200 kHz A-G A-G A-G A-G1 A-G1 A-G A-G -- -- -- -- -- -- -- -- -- -- -- --

HRG Non-airgun Surveys 

with Frequencies ≤200 kHz A-G A-G A-G A-G1 A-G1 A-G A-G -- C-F -- -- -- -- -- -- C-F -- -- F 

Other G&G Surveys A-G A-G A-G A-G1 A-G1 A-G A-G -- -- -- -- -- -- -- -- -- -- -- --

CP = Central Planning Closure Area; EP = Eastern Planning Closure Area; EPA = Eastern Planning Area; ft = feet; HRG = high-resolution geophysical; 

kHz = kilohertz; m = meters; NMS = National Marine Sanctuary; PAM = passive acoustic monitoring; PSO = protected species observer. 1 Avoidance of historic and prehistoric sites and sensitive benthic communities applies only to surveys that involve seafloor-disturbing activities. Seismic airgun 

surveys and non-airgun HRG surveys that do not disturb the seafloor are not required to avoid these sites or features. Non-airgun HRG surveys and most 

seismic airgun surveys (except those in which cables or sensors are placed in or on the seafloor) do not disturb the seafloor. 2 Expanded to include manatees and all water depths. 3 Expanded to include all water depths and all shutdown for all marine mammals with the exception of bow-riding dolphins (i.e., bottlenose, Fraser’s, Clymene’s, 

rough-toothed, striped, spinner, Atlantic spotted, pantropical, and Risso’s). 4 During periods of reduced visibility for surveys in waters deeper than 100 m (328 ft). 5 PAM required for all airgun surveys at all times in the Mississippi Canyon and De Soto Canyon lease blocks. 6 Applies to Federal coastal waters shoreward of the 20-m (66-ft) isobaths between January 1 and April 30. 7 Applies to all coastal waters shoreward of the 20-m (66-ft) isobaths between February 1 and May 31. 8 Does not apply to currently leased blocks, any portion of the area encompassed by EPA Lease Sale 226, or neighboring blocks adjacent to permitted survey 

areas but within an otherwise off-limit area.
xiv Executive Summary

ISSUES

Issues are the principal effects that should be rigorously evaluated in an EIS. Issues, which 

refers to specific environmental resources and activities, are identified during scoping. The analysis 

conducted in an EIS identifies the change from present conditions for each issue resulting from the 

relevant actions related to the proposed action. The issues identified for analysis in this 

Programmatic EIS are listed below: 

• impacts of underwater noise on marine mammals, sea turtles, fishes, marine and 

coastal birds, benthic communities, Marine Protected Areas (MPAs), commercial 

and recreational fishing (fish catch), and other marine life; 

• impacts of vessel traffic (risk of ship strikes) on marine mammals, sea turtles, 

marine and coastal birds, and Sargassum communities; 

• impacts of vessel traffic on commercial and recreational fishing, shipping, and 

other marine uses; 

• impacts of aircraft traffic and noise on marine mammals, sea turtles, marine and 

coastal birds, and other marine uses; 

• impacts of entanglement from marine equipment on marine mammals, sea 

turtles, archaeological resources, fishes, and other marine life; 

• impacts of stand-off distances on commercial and recreational fishing, shipping, 

recreational resources, and other marine uses; 

• impacts of vessel discharges on Sargassum communities; 

• impacts of trash and debris on benthic communities, marine mammals, sea 

turtles, marine and coastal birds, endangered or threatened fish species, benthic 

communities, MPAs, and Sargassum communities; 

• impacts of seafloor-disturbing activities on sensitive benthic communities, 

including coral and hard/live bottom communities and chemosynthetic 

communities; 

• impacts of seafloor-disturbing activities on Essential Fish Habitat (EFH), Habitat 

Areas of Particular Concern (HAPCs), MPAs, and archaeological resources, 

including historic shipwrecks and prehistoric archaeological sites; 

• impacts of geological test well discharges on EFH, benthic communities, MPAs, 

and archaeological resources; and

• impacts of accidental spills on benthic communities, marine mammals, sea 

turtles, marine and coastal birds, fishes and EFH, benthic communities, 

Sargassum communities, commercial and recreational fishing, archaeological 

resources, MPAs, and other marine uses.
Gulf of Mexico G&G Activities Programmatic EIS xv

Resource Areas and Impact Significance Criteria

Baseline environmental characterization and impact analysis for each alternative were 

conducted for 12 resource areas:

• marine mammals;

• sea turtles; 

• fisheries resources and EFH; 

• benthic communities;

• marine and coastal birds;

• MPAs;

• Sargassum communities;

• commercial fisheries;

• recreational fisheries;

• archaeological resources; 

• other marine uses; and

• human resources and land use.

Impact significance criteria were applied to each resource area based on four parameters: 

detectability (i.e., measurable or detectable impact); duration (i.e., short term, long term); spatial 

extent (i.e., localized, extensive); and severity (i.e., severe, less than severe). The resulting impact 

significance criteria were broadly defined as

• Nominal: Little or no measurable/detectable impact;

• Minor: Impacts are detectable, short term, extensive or localized, but less than 

severe; 

• Moderate: Impacts are detectable, short term, extensive, and severe; or impacts 

are detectable, short term or long lasting, localized, and severe; or impacts are 

detectable, long lasting, extensive or localized, but less than severe; and

• Major: Impacts are detectable, long lasting, extensive, and severe.

Resource-specific significance criteria were developed on a resource-specific basis to 

determine the appropriate impact level for each IPF.
xvi Executive Summary

Impact-Producing Factors

The IPFs are G&G activities that, based on their potential to affect the environment, require a 

thorough analysis in this Programmatic EIS. The IPF candidates were screened and those selected 

for inclusion are as follows (Table ES-2): 

• active acoustic sound sources;

• vessel and equipment noise;

• vessel traffic;

• aircraft traffic and noise;

• stand-off distances;

• vessel discharges;

• trash and debris; 

• seafloor disturbance;

• geological test well discharges;

• entanglement; and

• accidental fuel spills.

Cumulative Impacts

Cumulative effects refer to the impact on the environment that results from the incremental 

impact of an action when added to other past, present, and reasonably foreseeable future actions. 

Cumulative impacts can result from individually minor but collectively significant actions taking place 

over a period of time. An analysis was conducted to identify non-G&G activities with IPFs similar to 

those in G&G activities that should be considered for inclusion in a cumulative activities scenario. 

The resultant screening analysis identified the potentially significant cumulative effects issues 

associated with the proposed action and defined the assessment goals and the resultant cumulative 

scenario, including activities classified under three major topical areas or components. The three 

major topical areas (components) are the OCS Program, Oil and Gas Activities in State Waters, and 

Other Major Factors Influencing the AOI.
Gulf of Mexico G&G Activities Programmatic EIS xvii

Table ES-2 Preliminary Screening of Potential Impacts (Leopold Matrix) (Shaded resources were eliminated from detailed analysis due to limited 

anticipated impacts associated with G&G activities.) 

Resource

Active Acoustic Sound Sources

Vessel and Equipment Noise

Vessel Traffic

Aircraft Traffic and Noise

Stand-Off Distances

Vessel Discharges

Trash and Debris

Seafloor Disturbance

Drilling Discharges

Entanglement

Accidental Fuel Spill

Marine Mammals + + + + - - + - - + +

Sea Turtles + + + + - - + - - + +

Fisheries Resources and Essential Fish Habitat + + - - - - + + + + +

Benthic Communities + - - - - - + + + - +

Marine and Coastal Birds + + + + - - + - - - +

Marine Protected Areas + - - - - - + + + - +

Sargassum and Associated Communities - - + - - + + - - - +

Commercial Fisheries + - + - + - - + - + +

Recreational Fisheries + - + - + - - - - - +

Archaeological Resources - - - - - - - + + + +

Other Marine Uses - - + + + - - + - +

Human Resources and Land Use1 - - - - - - - - - - -

Recreational Resources and Tourism - - - - - - - - - - -

Air Quality - - + + - - - - - - -

Water Quality - - - - - + + - + - +

Geography and Geology - - - - - - - + - - -

Physical Oceanography - - - - - - - - - - -

Coastal Barrier Island Beaches, Seagrass, and Wetlands - - - - - - - - - - -

G&G = geophysical and geological

Key: + indicates a potential impact; - indicates no impact expected.

1 The IPFs do not apply to this resource; however, resource subcomponents have potential impacts from some alternatives.
xviii Executive Summary

OCS Program: The OCS Program includes activities associated with oil and gas exploration 

and development, decommissioning, renewable energy development, and marine minerals use. The 

IPFs associated with OCS Program activities that coincide with the proposed action include vessel 

and equipment noise (including explosives use [decommissioning]), vessel traffic (support vessel 

traffic), aircraft traffic and noise, stand-off distance, vessel discharges, seafloor disturbance, 

geological test well discharges, and accidental fuel spills. All G&G survey activities associated with 

the OCS Program are included in the proposed action; therefore, G&G activities are not included in 

the cumulative analysis but instead are addressed in the proposed action impact analysis.

Oil and Gas Activities in State Waters: The Oil and Gas Activities in State Waters Program 

includes activities associated with oil and gas exploration and development and decommissioning. It 

is recognized that the types of activities described for OCS Program activities would be the same as 

the Oil and Gas Activities in State Waters Program and would have the same IPFs. However, oil 

and gas activities in State waters would include the G&G surveys permitted by other agencies. 

Therefore, the IPFs that coincide with G&G activities include active acoustic sound sources, vessel 

and equipment noise, vessel traffic (support vessel traffic), aircraft traffic and noise, stand-off 

distance, trash and debris, seafloor disturbance, geological test well discharges, entanglement, and 

accidental fuel spills.

Other Major Factors Influencing the AOI: The other major factors influencing the AOI 

program include activities associated with deepwater ports; commercial and recreational fishing; 

shipping and marine transportation; ocean dredged material disposal site (ODMDS); existing, 

planned, and new cable infrastructure; military activities; scientific research; maintenance dredging 

of Federal channels; coastal restoration programs; Mississippi River hydromodification; extreme 

climatic events; climate change and sea-level rise; and natural oil seeps. The IPFs associated with 

activities associated with other major factors influencing the AOI that coincide with the proposed 

action include active acoustic sound sources, vessel and equipment noise, vessel traffic, aircraft 

traffic and noise, stand-off distance, vessel discharges, trash and debris, seafloor disturbance, 

entanglement, and accidental fuel spills.

IMPACT CONCLUSIONS BY RESOURCE FOR ALTERNATIVES A THROUGH G 

The analysis conducted in this Programmatic EIS identifies the change from present 

conditions for issues (principal effects identified for analysis) resulting from the relevant actions 

related to the proposed action. Baseline environmental characterization and impact analysis for 

seven alternatives (A through G) were conducted for the 12 resource areas listed previously 

considering the IPFs (G&G activities with the potential to affect the environment of the AOI). The 

levels of impacts determined by resource and applicable IPF across the seven alternatives are 

presented in Table 2.10-1. The analysis of impacts for resource areas under Alternatives A 

through G are discussed in detail in Chapter 4. The differences in impacts between those identified 

under Alternative A and those identified for Alternatives B through G are discussed by resource and 

the relevant IPF. The IPFs and impact significance criteria applied during the impact assessment 
Gulf of Mexico G&G Activities Programmatic EIS xix

remained the same for all alternatives for each resource. The conclusions of impact assessment for 

alternatives are presented below.

Impact Conclusions for Marine Mammals

In the northern GOM, there are 21 species of marine mammals (whales, dolphins, and 

manatees) likely to occur within the AOI (Table 4.2-1 and Appendix E). All marine mammal species 

within U.S. waters are protected under the MMPA and, if listed, receive additional protection under 

the ESA.

The exposure of marine mammals from G&G activities using active acoustic sources such as 

airguns and HRG surveys using non-airgun acoustic sources that emit sound at frequencies 

<200 kHz was estimated using mathematical models. The characteristics of G&G sound sources 

and the propagation of sound away from the sources was modeled. The exposure of each species 

of marine mammal was estimated by the amount of sound received by animats, simulated marine 

mammals, in the area within the AOI affected by a sound source. The consequences of exposure to 

G&G sound was estimated by comparing the amount of sound received by animats with thresholds 

specified by NMFS and Southall et al. (2007) for Level A harassment and by NMFS and Wood et al. 

(2012) for Level B harassment (Appendix D). Impact analysis used the upper limit of potential 

exposures provided in modeled exposure estimates and considered potential responses by marine 

mammals, as well as and the potential effects of mitigation measures on species-specific estimated 

levels of Level A and Level B harassment.

Alternative A – Pre-Settlement (June 2013) Alternative: Under Alternative A, standard 

mitigation measures would be applied to G&G activities through lease stipulations, issued permits, 

and authorizations as Conditions of Approvals, Notices to Lessees, and best management practices 

(Table ES-1). Resource-specific impact significance criteria and IPFs applied during impact analysis 

under Alternative A are described in Chapter 4.1.2 and shown in Table ES-2, respectively.

Based on the analysis conducted, the effects of G&G deep-penetration airgun seismic 

survey activity noise are expected to be moderate because impacts on marine mammals are 

expected to be extensive but not severe with no lethal impacts. The effects of noise from shallowpenetration HRG airgun surveys on marine mammals are expected to be minor, neither extensive 

nor severe. Estimates of incidental exposure of marine mammals within the AOI using the source 

characteristics of a single airgun typical of shallow-penetration surveys were low or zero with no 

lethal impacts predicted. Noise from non-airgun HRG active acoustic sound sources was predicted 

to impact very few marine mammals over the 10 years of the program with limited behavioral 

harassment, cause a small number of permanent threshold shift (PTS) physical injuries, and have no 

lethal impacts. Consequently, the impacts of noise from non-airgun HRG survey activities on marine 

mammals in the AOI are expected to be minor. 

The proposed additional vessel traffic linked to Alternative A is not expected to significantly 

increase existing vessel traffic within the AOI. Combined with assumed familiarity of marine 
xx Executive Summary

mammals with vessel traffic and the underwater noise they make, the impacts of project-related 

vessel and equipment noise under Alternative A are expected to be nominal to minor. Similarly, 

project-related vessel traffic is expected to be a minor addition to existing vessel traffic. Strike by a 

project vessel of a marine mammal would be unlikely, but if it did occur, it could result in a mortality. 

Therefore, overall impacts from vessel traffic under Alternative A are expected to be nominal to 

moderate. Use of aircraft under Alternative A would be very limited and would potentially result in 

short-duration exposure of marine mammals to noise, whether located at the surface or underwater, 

as well as physical (visual) sighting of aircraft. Impacts are expected to be slight or not measurable, 

limited to behavioral disruption, and therefore nominal. 

Marine debris may be accidentally lost from vessels involved in G&G activities even though 

the handling of debris is a managed and highly regulated activity. Marine mammals may ingest or, 

more likely, become entangled in debris. Because it is unlikely that significant amounts of debris will 

be lost from vessels involved in G&G activities under Alternative A, the impacts of ingestion and 

entanglement of marine mammals in debris are expected to be nominal. Marine mammals may 

become entangled in lines involved with the placement of various types of G&G equipment, such as 

anchors and acoustic pingers. Because of this possibility, guidance has been developed for the use 

of G&G equipment that poses entanglement risk. Because of management of activities where 

entanglement is a risk, combined with the limited scope and spatial extent of such activities under 

Alternative A, the impacts of entanglement on marine mammals are expected to be nominal. 

The likelihood of a fuel spill during G&G activities is considered remote. If fuel should be 

accidentally spilled, the potential impact on marine mammals will depend on when and where the 

spill occurs and various environmental conditions that would affect the rapidity with which the spilled 

fuel weathers. Under the accidental spill scenario, potential impacts to marine mammals are 

expected to be nominal to minor, depending on the numbers of animals exposed, exposure time, 

and whether exposed animals are listed species.

The G&G activities proposed under Alternative A will not significantly increase the historical 

level of similar activities in the GOM under the cumulative scenario. In addition, G&G activities 

under Alternative A are more concentrated in the deepwater areas of the WPA and CPA, and less so 

on the continental shelf. Under the cumulative scenario, the cumulative IPFs to marine mammals 

would result in nominal to minor incremental increases in impacts.

Alternative B – Settlement Agreement Alternative: Alternative B would implement the 

mitigation measures of Alternative A and would add four mitigation measures that include expanded 

use of PAM, time-area closure of Federal coastal waters, requiring a separation distance between 

deep-penetration seismic sources in Areas of Concern, and prohibiting deep-penetration surveys in 

a portion of the EPA. Specifically, the addition of mitigation measures under Alternative B provides 

protection under deep-penetration airguns and shallow-penetration airguns to coastal marine 

mammal species (i.e., common bottlenose dolphins, manatees, and Atlantic spotted dolphins) when 

they are reproducing (calving). This may increase the fitness values of the reproducing species; 

bay, sound, and estuary (BSE) stocks of bottlenose dolphins; and individual coastal stocks of 
Gulf of Mexico G&G Activities Programmatic EIS xxi

bottlenose dolphins, Atlantic spotted dolphins, manatees, and whale species (i.e., Bryde’s, beaked, 

sperm, and dwarf and pygmy sperm whales). Additionally, manatees are provided localized 

reduction in sound exposure and associated impacts. Individual beaked whales and sperm whales, 

as well as potentially calving sperm whales, and the small population of geographically and 

genetically distinct Bryde’s whales in the GOM and vocalizing marine mammals are expected to 

benefit from these mitigations as well. Analysis of these measures for the IPFs affecting marine 

mammals determined that the impact ratings for the IPFs affecting marine mammals would remain 

unchanged from those found under Alternative A (nominal to moderate), while potentially reducing 

impacts to individuals and groups of marine mammals within the AOI, perhaps significantly so for 

Bryde’s whales and sperm whales. Under the cumulative impact assessment, the addition of 

Alternative B mitigation measures would also not significantly change the comparative contribution of 

Alternative B from that of Alternative A. The cumulative impacts under Alternative B would not 

change from those found under Alternative A (nominal to minor).

Alternative C – Alternative A Plus Additional Mitigation Measures: The IPFs and impact 

significance criteria applied for Alternative A are used for Alternative C. The impact analysis 

considered the effect of three additional mitigation measures implemented under Alternative C on 

marine mammals (e.g., required use of PAM in water depths >100 m [328 ft] and for surveys in the 

Mississippi Canyon and De Soto Canyon OCS lease blocks, and implementation of the Non-Airgun 

Survey Protocol) and one expanded mitigation measure (e.g., coastal restriction expanded to 

between February 1 and May 31). Specifically, the addition of mitigation measures under 

Alternative C provides protection under deep-penetration airguns and shallow-penetration airguns to 

coastal marine mammal species (i.e., common bottlenose dolphins, manatees, and Atlantic spotted 

dolphins) when they are reproducing (calving). It is expected that these mitigation measures would 

also increase the fitness values of the bay, sound, and estuary (BSE) stocks of bottlenose dolphins; 

individual coastal stocks of bottlenose dolphins, Atlantic spotted dolphins, and manatees; individual 

beaked whales and sperm whales, as well as potentially calving sperm whales; the small population 

of geographically and genetically distinct Bryde’s whales in the GOM; and vocalizing marine 

mammals. Additional mitigation protection is provided to all marine mammals and sea turtles, with 

additional protection (shutdown) for sperm, Bryde’s, beaked, dwarf and pygmy sperm whales, and 

manatees. These measures are an extension of using Protected Species Observers (PSOs) and 

Passive Acoustic Monitoring (PAM), time-area closures in Federal coastal waters, expansion of 

protection to manatees, clearance of marine mammals from exclusion zones before survey start-up 

or following the Non-Airgun Survey Protocol for non-airgun HRG surveys using low-frequency

(<200 kHz) sound sources, and Airgun Survey Protocols for deep-penetration seismic surveys. 

While the additional mitigation measures under Alternative C might reduce impacts to marine 

mammals from routine activities and accidental event IPFs, the overall impact ratings by IPF would 

remain the same as those found for Alternative A (nominal to moderate). The cumulative impacts 

under Alternative C would not change from those found under Alternative A (nominal to minor). 

Alternative D – Alternative C Plus Marine Mammal Shutdowns: Under Alternative D, 

impact significance criteria and IPFs are the same as those under Alternative A but with the addition 

of three mitigation measures. Mitigation measures implemented under Alternative D would include 
xxii Executive Summary

some of those implemented under Alternatives A and C plus additional survey protocols for airgun 

and non-airgun HRG surveys presented previously. Specifically, the addition of mitigation measures 

under Alternative D provides protection under deep-penetration and shallow-penetration airguns to 

vocalizing marine mammals and all marine mammals except bow-riding dolphins (i.e., bottlenose, 

Fraser’s, Clymene’s, rough-toothed, striped, spinner, Atlantic spotted, pantropical, and Risso’s). 

Additional mitigation protection is provided from non-airgun HRG equipment operating at frequencies 

<200 kHz to all marine mammals and sea turtles, with additional protection (shutdown) for sperm, 

Bryde’s, beaked, dwarf, and pygmy sperm whales, and manatees. Although the additional mitigation 

measures implemented under Alternative D might reduce impacts to marine mammals from IPFs of 

routine activities and accidental events, the potential reductions, as evaluated using impact 

significance criteria, are not sufficient to change the overall impact ratings for IPFs from those of 

Alternative A (nominal to moderate). The timing of seismic airgun surveys in certain areas would 

change; however, these changes would not significantly change contributions to the cumulative 

impacts determined under Alternative A (nominal to minor).

Alternative E – Alternative C at Reduced Activity Levels: Alternative E would implement 

the mitigation measures of Alternatives A and C at reduced levels of activity through two mitigation 

alternatives (E1 and E2) that would reduce the level of deep-penetration, multi-client survey activities 

by 10 and 25 percent, respectively, for calendar year estimated levels. Specifically, the addition of 

mitigation measures under Alternative E provides protection for deep-penetration airguns and 

shallow-penetration airguns to coastal marine mammal species (i.e., common bottlenose dolphins, 

manatees, and Atlantic spotted dolphins) when they are reproducing (calving). It is also projected 

that the mitigation measures would increase the fitness values of the following species: BSE stocks 

of bottlenose dolphins; individual coastal stocks of bottlenose dolphins, Atlantic spotted dolphins, 

and manatees; individual beaked whales and sperm whales, as well as potentially calving sperm 

whales; the small population of geographically and genetically distinct Bryde’s whales in the GOM; 

and vocalizing marine mammals. Additional mitigation protection is provided for non-airgun HRG 

surveys using low-frequency (<200 kHz) sound sources to all marine mammals and sea turtles, with 

additional protection (shutdown) for sperm, Bryde’s, beaked, dwarf and pygmy sperm whales, and 

manatees. Impact analysis of these measures found that, while they might reduce potential impacts 

from routine activities and accidental event IPFs, the overall impact ratings would remain the same 

as those found for Alternative A (nominal to moderate). The cumulative impacts analysis for 

Alternative E found that the contributions to cumulative impacts would remain the same as those 

found under Alternative A (nominal to minor).

Alternative F – Alternative C Plus Area Closures: The mitigation measures implemented 

under Alternative F include those of Alternatives A and C plus four area closures targeted to provide 

protection to sperm and Bryde’s whales plus beaked whales and other resources. Specifically, the 

addition of mitigation measures under Alternative F provides protection under deep-penetration and 

shallow-penetration airguns to coastal marine mammal species (i.e., common bottlenose dolphins, 

manatees, and Atlantic spotted dolphins) when they are reproducing (calving). It is also projected 

that the mitigation measures would increase the fitness values of the following species: BSE stocks 

of bottlenose dolphins, individual coastal stocks of bottlenose dolphins, Atlantic spotted dolphins, 
Gulf of Mexico G&G Activities Programmatic EIS xxiii

and manatees; whale species (i.e., Bryde’s, beaked, sperm, and dwarf and pygmy sperm whales) 

and manatees providing localized reduction in sound exposure and associated impacts for those 

species; individual beaked whales and sperm whales, as well as potentially calving sperm whales; 

the small population of geographically and genetically distinct Bryde’s whales in the GOM; and 

vocalizing marine mammals. Additional mitigation protection is provided from non-airgun HRG 

surveys using sources operating at frequencies <200 kHz to all marine mammals and sea turtles, 

with additional protection (shutdown) for sperm, Bryde’s, beaked, dwarf, and pygmy sperm whales, 

and manatees. The Alternative F area closures to deep-penetration seismic surveys would result in 

reduced exposures of marine mammals to seismic sound and a reduction of potential impact for the 

deep-penetration airgun survey noise IPF from moderate to minor. The levels of impact 

determined under Alternative F for all other IPFs for routine activities and accidental events would 

remain the same as those found under Alternative A (nominal to minor). The cumulative impacts 

analysis for Alternative F found that the contributions to cumulative impacts would remain the same 

as those found under Alternative A (nominal to minor) even though the timing of seismic airgun 

survey would change in certain areas and selected areas would be closed to deep-penetration

surveys during the project duration.

Alternative G – No New Activity Alternative: Under Alternative G, the only survey 

activities would be zero-offset, walkaway vertical seismic profile (VSP), and seismic while drilling 

(SWD) surveys. The IPFs and significance criteria would be those of Alternative A; however, there 

would be no impacts from the entanglement IPF since no ocean bottom cable (OBC) surveys would 

occur. Under Alternative G, no new G&G surveys would be permitted but those previously 

authorized would proceed. Elimination of all new G&G survey activities within the AOI would reduce 

potential impacts from IPFs to individual or groups of marine mammals; but, under the impact 

significance criteria applied during analysis, the overall impact ratings for routine events would 

initially remain the same as those for Alternative A (nominal to moderate) with the exceptions of 

that for deep-penetration airgun survey noise, which would be reduced from moderate to minor, 

and entanglement, which would be reduced from nominal to no impact. As G&G activities were 

phased out under Alternative G, impacts would eventually be reduced to no impact. The cumulative 

impacts analysis for Alternative G found that the contributions to cumulative impacts would remain 

the same as those found under Alternative A (nominal to minor).

Impact Conclusions for Sea Turtles

Five species of sea turtles (i.e., loggerhead, green, Kemp’s ridley, hawksbill, and 

leatherback) occur at least seasonally in the northern GOM; all are listed as threatened or 

endangered under the ESA. Little is known about how sea turtles may use sound. Studies of sea 

turtle hearing indicate that only airgun, boomer, and sparker G&G sound sources are likely to be 

heard by sea turtles, and little data are available to set thresholds for impacts to sea turtles from 

exposure to sound generated during G&G activities.

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact sea turtles within the AOI 
xxiv Executive Summary

under Alternative A are shown in Table ES-2, and impact levels and resource-specific significance 

criteria applied during impact analysis are discussed in Chapter 4.3.2. 

No lethal or population-level impacts from auditory injuries, only behavioral disturbances, are 

expected for sea turtles exposed to sound resulting from deep-penetration seismic airgun surveys. 

The impact to sea turtles from seismic airgun survey activities is expected to be minor. 

Only boomer and sparker non-airgun sources used during non-airgun HRG surveys are likely 

to be heard by sea turtles, and any sound-related impacts are expected to be limited to behavioral 

effects and temporary threshold shift (TTS)-related impacts. Impacts to sea turtles from non-airgun 

HRG survey sound sources are expected to range from nominal to minor, depending on the 

conditions of exposure.

Noise from G&G vessels and equipment could potentially disturb individual sea turtles near 

vessels, resulting in evasive maneuvers and contributing to auditory masking. Also, geological test 

well-related noises, dynamic positioning equipment, and other geological test well sounds could be 

heard by sea turtles. However, the level of G&G geological test well activity under Alternative A is 

expected to be very low. Overall, the level of impact from G&G vessels and equipment on sea 

turtles is expected to be nominal. 

The G&G vessels could strike and kill sea turtles because it is very difficult for PSOs to 

detect them at long distances. However, the level of G&G vessel traffic over the 10-year project 

period is low compared with existing vessel traffic in the AOI, and most vessel strikes of sea turtles 

occur in coastal areas by high speed (recreational) vessel traffic. The potential impacts to sea 

turtles in the AOI from G&G vessel traffic are expected to range from nominal to moderate, 

depending on whether a sea turtle is struck and injured by a vessel involved in a G&G event.

Potential impacts to sea turtles from aircraft traffic (fixed wing and helicopter) include noise 

and physical (visual) disturbance. Exposure of a sea turtle to sound from an aircraft flying overhead 

would be brief, and behavioral responses would be evasive in nature. Considering that the number 

of G&G activities requiring aircraft is very limited under Alternative A, the potential impacts to sea 

turtles within the AOI from aircraft traffic are expected to be nominal. 

Sea turtles may ingest or become entangled in trash and debris. While G&G activities will 

generate trash and debris, regulations and management practices are expected to limit trash and 

debris introduced into the AOI from G&G activities to accidental loss. Therefore, trash and debris 

impacts from G&G activities on sea turtles in the AOI are expected to be nominal. 

Several types of equipment (e.g., tether lines, cables, and towed arrays) used during G&G 

activities pose an entanglement or entrapment risk to sea turtles. Measures have been developed to 

reduce the risk of entanglement of sea turtles in tethers. It is possible that entrapment of sea turtles 

in towed seismic equipment occurs, is undetected, and results in injury or death to sea turtles. No 

data are available to evaluate this potential source of impact. Entanglement of sea turtles in 
Gulf of Mexico G&G Activities Programmatic EIS xxv

equipment used for OBC/OBN surveys may be possible but, under Alternative A, such surveys are 

relatively uncommon. Overall, impacts to sea turtles in the AOI from entanglement and entrapment 

during G&G events are expected to be nominal. 

It is unlikely that a small fuel spill in the ocean would reach sea turtle nests and, given the 

expected rapid dispersion of spilled fuel, is it not expected to result in the death or life-threating injury 

to individual sea turtles or hatchlings. Impacts to sea turtles within the AOI from a fuel spill are 

expected to range from nominal to minor, depending on whether individual sea turtles encounter 

the fuel.

While proposed G&G activities under Alternative A could incrementally increase the level of 

some IPFs and result in impacts, the incremental addition under the cumulative scenario compared 

with similar historic, present, and future activities would result in nominal to minor incremental 

increases in impacts.

Alternative B – Settlement Agreement Alternative: Alternative B implements the 

mitigation measures of Alternative A plus analysis of impacts for routine activity IPFs. Considering 

the additional mitigation measures under Alternative B and the project 10-year timeframe, there are 

no changes in impact levels from those found under Alternative A (nominal to minor). The impact 

rating of the effects of an accidental fuel spill on sea turtles was found to be the same for 

Alternative B as for Alternative A (nominal to minor). The cumulative impacts analysis for 

Alternative B found that the contributions to cumulative impacts would remain the same as those 

found under Alternative A (nominal to minor).

Alternative C – Alternative A Plus Additional Mitigation Measures: Alternative C 

implements the mitigation measures of Alternative A plus others that prohibit airgun surveys 

seasonally in all coastal waters, extension of Seismic Survey Protocols to manatees, and survey 

clearance measures for low-frequency (<200 kHz) non-airgun HRG surveys. Specifically, the 

addition of mitigation measures under Alternative C provides protection from non-airgun HRG 

equipment to all marine mammals and sea turtles, with additional protection (shutdown) for sperm, 

Bryde’s, beaked, dwarf and pygmy sperm whales, and manatees. Assessment of the effects of 

Alternative C mitigation measures on impacts from routine activities found no change from those 

found under Alternative A (nominal to minor). The impacts of an accidental fuel spill were 

determined to remain the same as those found under Alternative A (nominal to minor). While 

Alternative C mitigation measures would change the timing of proposed action activities in certain 

areas, the seasonal restriction and operational mitigation measures would not significantly change 

the cumulative impacts under Alternative C, which would remain the same for sea turtles as those 

under Alternative A (nominal to minor).

Alternative D – Alternative C Plus Marine Mammal Shutdowns: Alternative D 

implements the mitigation measures of Alternatives A and C plus shut-downs (additional survey 

protocols for airgun and non-airgun HRG surveys with low-frequency [<200 kHz] equipment) for 

marine mammals. Specifically, the addition of mitigation measures under Alternative D provides 
xxvi Executive Summary

protection from non-airgun HRG equipment to all marine mammals and sea turtles, with additional 

protection (shutdown) for sperm, Bryde’s, beaked, dwarf and pygmy sperm whales, and manatees. 

This additional measure would not reduce the potential for impacts from active acoustic sources to 

sea turtles discussed under Alternatives A and C. Therefore, the impact rating for routine activities 

and accidental event IPFs would remain the same as those described for Alternative A (nominal to 

minor). The cumulative impacts analysis for Alternative D found that the contributions to cumulative 

impacts would remain the same as those found under Alternative A (nominal to minor).

Alternative E – Alternative C at Reduced Activity Levels: Mitigation measures under 

Alternative E are those of Alternatives A and C with reductions in the level of deep-penetration 

surveys. Specifically, the addition of mitigation measures under Alternative E provides protection 

from non-airgun HRG equipment (operating at frequencies <200 kHz) to all marine mammals and 

sea turtles, with additional protection (shutdown) for sperm, Bryde’s, beaked, dwarf and pygmy 

sperm whales, and manatees. The reductions are not specified for any particular area within the 

AOI, so the measures cannot be managed to optimize potential benefits to sea turtles. Assessment 

of Alternative E mitigation measures determined that there would be no change in the overall 

impacts to sea turtles under Alternative A (nominal to moderate) considered IPFs. Analysis under 

the cumulative impacts scenario determined that, while there would be reductions in impacts for 

routine activity IPFs proportional to reductions in deep-penetration seismic survey activities, the 

reductions would not appreciably change the cumulative impacts found under Alternative A 

(nominal to minor).

Alternative F – Alternative C Plus Area Closures: Alternative F includes the mitigation 

measures of Alternatives A and C plus prohibition of seismic airgun surveys in four areas. 

Specifically, the addition of mitigation measures under Alternative F provides protection from nonairgun HRG equipment (operating at frequencies <200 kHz) to all marine mammals and sea turtles, 

with additional protection (shutdown) for sperm, Bryde’s, beaked, dwarf and pygmy sperm whales, 

and manatees. Impact analysis has determined that, because the mitigation measures would not 

change the extent or severity of the IPFs in the majority of the AOI under Alternative F, the potential 

impacts to sea turtles from active acoustic impacts and other routine activity IPFs from those found 

for Alternative A would not be reduced (nominal to moderate). The cumulative scenario remained 

the same as that under Alternatives A and C, as did associated impacts. The area closures and 

changes in the timing of airgun surveys in certain areas did not appreciably change the assessment 

of cumulative impacts from those found for Alternative A (nominal to minor).

Alternative G – No New Activity Alternative: Alternative G would not permit any new G&G 

activities other than zero-offset and walkaway VSP and SWD surveys. The G&G activities already 

permitted would continue. Prohibition of new G&G activities would reduce but not eliminate 

exposure of sea turtles to G&G activity IPFs, with the exception of the entanglement IPF since no 

OBC surveys would occur. Therefore, the overall impact level from routine activity IPFs on sea 

turtles would not change from that of Alternative A (nominal to moderate) in the near term, but it 

would eventually decline to no impact as activities were phased out. The cumulative impacts 
Gulf of Mexico G&G Activities Programmatic EIS xxvii

analysis for Alternative G found that the contributions to cumulative impacts would be reduced to 

nominal. 

Impact Conclusions for Fisheries Resources and Essential Fish Habitat

The AOI covers a broad geographic and bathymetric region ranging from the shoreline to the 

open ocean and features a mix of fish resources that includes estuarine, coastal, and oceanic 

species associated with demersal and pelagic habitats. Fish that inhabit the AOI include threatened 

and endangered species (smalltooth sawfish and Gulf sturgeon) and their EFH managed under the 

ESA, as well as other species and EFH managed under other Federal acts. There are other fish 

species that are candidates for listing (Chapter 4.4.1).

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact fish and EFH within the 

AOI under Alternative A are shown in Table ES-2, and impact levels and resource-specific 

significance criteria applied during impact analysis are discussed in Chapter 4.4.2. 

Fishes exposed to deep-penetration seismic airgun survey activities might move away from 

the sound source or experience TTS or masking, but they would not likely suffer mortality. Because 

of the temporary nature of seismic sound at any particular location during a survey, exposures are 

expected to be short and, given the size of the AOI, occur within a relatively small portion of the AOI. 

Exposure of listed species is expected to be minimal because of their distribution within the AOI 

relative to the expected location of most deep-penetration surveys. Overall, the impacts to fishes 

within the AOI from exposure to deep-penetration seismic survey sound sources, including the 

endangered species, are expected to be nominal to minor. 

Some fishes have the ability to hear the high-frequency sounds emitted by non-airgun sound 

sources used for HRG surveys, in addition to those emitted by sources used for surveys that operate 

at lower frequencies (<200 kHz). Because the exposure of fish to non-airgun sound sources used 

for HRG surveys would be temporary and spatially limited, impacts of fishes and EFH are expected 

to be nominal under Alternative A.

Vessel and equipment noise generated within the AOI by G&G activities under Alternative A 

is expected to be temporary and localized to the area where the activity occurs. Impacts to all fish 

and EFH, as well as endangered species within the AOI, from vessel and equipment noise under 

Alternative A are expected to be minor. Under Alternative A, impacts of vessel and equipment 

noise to endangered smalltooth sawfish and Gulf sturgeon are expected to be nominal because 

their location is distant from the location of G&G activities, and any exposure would be rare.

Under Alternative A, trash and debris is not expected to be a concern for Gulf sturgeon, other 

fish resources, or EFH. Some types of trash and debris generated by G&G activities could pose a 

risk of entanglement to smalltooth sawfish. However, because disposal restrictions on trash and 

debris would limit the introduction of trash and debris into the AOI from vessels involved in G&G 
xxviii Executive Summary

activities to accidental loss and because of the sparse distribution of smalltooth sawfish, potential 

impacts to fish and EFH from trash and debris are expected to be nominal under Alternative A.

Because the area that may be impacted by seafloor disturbance is an extremely small 

portion of the AOI, impacts to fish and EFH from seafloor disturbance under Alternative A are 

expected to be nominal. For threatened and endangered fish, impacts are expected to be nominal

because these fish are mainly located mainly outside of the AOI.

The impacts to fish and EFH from entanglement are expected to be nominal because of the 

implementation of measures to reduce the risk of entanglement from equipment tethers and other 

similar G&G equipment and because of the limited scope and transitory nature of OBC/ocean 

bottom node (OBN) surveys under Alternative A.

The impacts to fish and EFH of a small fuel spill under Alternative A are expected to be 

nominal to minor, depending on the location of the event and encounter of the fuel by pelagic fish, 

as well as buoyant eggs and larvae.

Proposed G&G activities that may impact fish and EFH are spatially and temporally 

distributed over the AOI over the 10-year project period. In addition, fish resources have been 

exposed to IPFs similar to those associated with G&G activities proposed under Alternative A for 

decades, and fish populations have likely habituated to sound levels and many other IPFs. The 

additional exposures to IPFs within the AOI from G&G activities conducted under Alternative A 

would result in nominal to minor incremental increases in impacts to fish and EFH. 

Alternative B – Settlement Agreement Alternative: Alternative B adds three mitigation 

measures to those of Alternative A. These mitigation measures may affect the extent, severity, or 

timing of G&G activities with IPFs that may affect fish resources and EFH: seasonal restriction of 

airgun operation in coastal waters; separation of seismic sources; and seismic survey restriction in 

the EPA. Analysis of impacts under Alternative B has found no change in the level of overall 

impacts from that found for Alternative A (nominal to minor). Because little to no change in 

proposed action activities between Alternatives A and B were identified and because the 

Alternative B mitigation measures had limited effects on IPFs to fish and EFH, it was determined that 

the cumulative increase in impacts for this resource would remain the same as that for Alternative A 

(nominal to minor).

Alternative C – Alternative A Plus Additional Mitigation Measures: Alternative C would 

implement Alternative A mitigation measures plus additional measures, only one of which—seasonal 

restriction of airgun surveys in coastal waters—might benefit fish resources and EFH. Assessment 

of impacts from routine activity IPFs under Alternative C concluded that the level of overall impacts 

would remain the same as that for Alternative A (nominal to minor). The mitigation measures 

under Alternative C would not change proposed action activities so that the cumulative impact 

analysis outcome would remain the same as for Alternative A (nominal to minor).
Gulf of Mexico G&G Activities Programmatic EIS xxix

Alternative D – Alternative C Plus Marine Mammal Shutdowns: The additional mitigation 

measure added under Alternative D to those of Alternatives A and C would not change the impacts 

to fish resources and EFH. The result is no change from that of Alternative A (nominal to minor) in 

the level of overall impacts from the IPFs. The proposed action activities conducted under 

Alternative D do not change cumulative outcomes from those identified for Alternative A (nominal to 

minor).

Alternative E – Alternative C at Reduced Activity Levels: The reductions in G&G activity 

levels resulting from Alternative E mitigation measures were not found to significantly change the 

level of overall impacts from routine activity IPFs found for Alternatives A and C (nominal to minor). 

The risks of an accidental fuel spill were found to be very similar to those analyzed for Alternative C 

and were expected to range from nominal to minor. The mitigation measures of Alternative E 

would reduce the extent, severity, and timing of impacts from routine activity IPFs, but they would 

not change the impact rating of the cumulative outcomes of Alternative A (nominal to minor). 

Alternative F – Alternative C Plus Area Closures: The areas closed by the additional 

mitigation measures of Alternative F are small compared with the AOI, and impacts to fish and EFH 

from G&G activities would not be reduced outside of the areas; therefore, the level of overall impacts 

from routine activity IPFs would not be appreciably reduced from those of Alternatives A and C 

(nominal to minor). The mitigation measures of Alternative F would reduce the extent, severity, 

and timing of impacts from routine activity IPFs, but they would not change the impact rating of the 

cumulative outcomes of Alternative A (nominal to minor). 

Alternative G – No New Activity Alternative: Previously permitted but no new G&G 

activities would be permitted under Alternative G. The impact assessment for routine activity IPFs 

concluded that there would be some reduction in impacts to fish resources and EFH. Overall, the 

severity of impact to fish resources and EFH is expected to diminish from that of Alternative A 

(nominal to minor) to nominal only, eventually declining to no impact as activities are phased out. 

The entanglement IPF would be reduced from nominal to no impact because no OBC surveys 

would occur. The proposed action activities conducted under Alternative G change cumulative 

outcomes from those identified for Alternative A from nominal to minor to nominal only.

Impact Conclusions for Benthic Communities

The benthic environment of the AOI is complex, encompassing habitats with water depths 

ranging from <200 to 3,500 m (656 to 11,483 ft). In the AOI, there are 37 submerged banks 

protected from oil and gas activities. There are also isolated areas of moderate to high relief that 

provide habitat for hard bottom communities of high biomass and diversity, and large numbers of 

plant and animal species that support, either as shelter or food, large numbers of commercially and 

recreationally important fisheries. Seven threatened species of coral (i.e., elkhorn, staghorn, pillar, 

lobed star, mountainous star, star, and rough cactus) are found within the AOI.
xxx Executive Summary

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact benthic communities within 

the AOI under Alternative A are shown in Table ES-2, and impact levels and resource-specific 

significance criteria applied during impact analysis are discussed in Chapter 4.5.2. 

The impacts to benthic communities from sound generated by active acoustic sound sources 

(e.g., airguns) are largely unknown and have not been shown to have a significant impact on benthic 

communities. Benthic organisms are usually well away from the immediate vicinity of sound sources 

where all of the known, more serious effects to organisms occur; therefore, impacts are expected to 

be nominal. Impacts from propagating sound well away from a sound source to sensitive benthic 

environments, like coral reefs, outside of the planning areas but within the AOI also would be 

nominal. Therefore, impacts to all benthic communities from active acoustic sound sources would 

be nominal. 

Because of compliance of G&G activities with Federal regulations and guidance from BOEM, 

the amount of trash and debris introduced into the AOI is expected to be accidental and minimal. 

Therefore, impacts from trash and debris on benthic communities generated by seismic survey 

vessels and other G&G-related activities would be nominal. 

There are several G&G activities that could cause seafloor disturbance; however, the total 

area disturbed by bottom sampling is expected to be very small and, during permitting, BOEM would 

require site-specific information about the presence of potentially sensitive benthic communities and 

require setbacks and other measures to avoid impacts to benthic communities. Therefore, impacts 

to sensitive benthic resources under Alternative A to benthic communities are expected to be 

nominal. 

Under Alternative A, up to two test wells would be drilled in the AOI. The areal extent of 

impacts from geological test well discharges during the proposed action would be small, and the 

impacts on soft bottom communities within the AOI are expected to be nominal. Impacts from 

geological test well discharges on hard/live bottom areas, deepwater coral communities, and 

chemosynthetic communities within the AOI under Alternative A are expected to be nominal

because of actions taken during permitting/authorization.

There is the potential for a small proportion of the heavier fuel components of a small diesel 

fuel spill to adhere to particulate matter in the upper portion of the water column and sink. However, 

given the expected relatively small size of any spill and the loss of most spilled fuel through 

evaporation and weathering, a small diesel fuel spill would be expected to result in nominal impacts 

to benthic communities.

The G&G activities under Alternative A would result in a nominal incremental increase in 

impacts from noise, trash and debris, seafloor disturbances, and an accidental fuel spill to benthic 

communities under the cumulative scenario.
Gulf of Mexico G&G Activities Programmatic EIS xxxi

Alternative B – Settlement Agreement Alternative: Alternative B mitigation measures 

include those of Alternative A plus mitigation measures resulting from the 2013 Settlement 

Agreement and the 2016 Stipulation to Amend Settlement Agreement. Most of the additional 

mitigation measures included in Alternative B will not alter impacts to benthic communities; so, while 

there may be some reduction in impacts from routine activity IPFs, there will be no change in the 

impact level of overall impacts from that of Alternative A (nominal). Alternative B mitigation 

measures would reduce cumulative impacts; they would not significantly change the degree of 

impacts from the proposed action, and impacts would remain nominal. 

Alternative C – Alternative A Plus Additional Mitigation Measures: The additional 

mitigation measures included in Alternative C will not further restrict routine activity actions with IPFs 

that could impact benthic communities. No change in the impact level of the overall impacts of 

routine activity IPFs is expected under Alternative C from that of Alternative A (nominal). 

Alternative C measures would reduce cumulative impacts from IPFs associated with routine 

activities, but they will not change the incremental impacts from the proposed action, which will 

remain nominal. 

Alternative D – Alternative C Plus Marine Mammal Shutdowns: The Alternative D 

additional mitigation measures will not reduce the potential impacts to benthic communities from 

G&G activity routine activity IPFs from that determined for Alternative A (nominal). Alternative D 

measures would not change the extent, timing, or severity of proposed action activities and impacts 

to benthic communities. The incremental increase in impacts to benthic communities under the 

cumulative scenario would remain nominal. 

Alternative E – Alternative C at Reduced Activity Levels: The additional mitigation 

measures under Alternative E would reduce impacts to benthic communities but not enough from 

that determined for Alternative A to change the potential impact level from nominal. Alternative E 

would reduce survey vessel activities, thereby reducing the potential impact from accidental fuel 

spills; so, even though the potential for a spill would be reduced, the impact level would remain 

nominal if a spill occurred. Under the cumulative impacts scenario, Alternative E measures would

reduce impacts for many routine activity IPFs; however, the incremental increase in impacts to 

benthic communities would remain nominal. 

Alternative F – Alternative C Plus Area Closures: Most of the additional mitigation 

measures under Alternative F would not reduce impacts to benthic communities, so there would be 

no change in the impact level for Alternative F of overall impacts from that found for Alternative A 

(nominal). Alternative F seasonal restrictions for airgun surveys in coastal waters and the

prohibition of deep-penetration survey in portions of the EPA would change the location of the 

proposed action activities, but it would not significantly change the degree of proposed action 

impacts with the result that incremental increases in impacts to benthic communities would remain 

nominal for Alternative F.
xxxii Executive Summary

Alternative G – No New Activity Alternative: Impacts of routine activities would be 

reduced from nominal to no impact to nominal under Alternative G. The risk of an accidental spill 

would reduce over time; however, the impacts from accidental fuel spills would range from no 

impact to nominal. Under the cumulative impacts scenario, the incremental impact to benthic 

communities would range from no impact to nominal. 

Impact Conclusions for Marine and Coastal Birds

The GOM supports a diverse avifauna, both resident and migratory species, and includes a 

variety of coastal habitats that are important to the ecology of coastal and marine bird species. 

Within the AOI, there are three species listed under the ESA (i.e., the Piping Plover, Roseate Tern, 

and Red Knot), and no candidate or species of concern have been identified.

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact marine and coastal birds 

within the AOI under Alternative A are shown in Table ES-2, and impact levels and resource-specific 

significance criteria applied during impact analysis are discussed in Chapter 4.6.2. 

The primary potential for direct impact to marine and coastal birds from airguns and other 

active acoustic non-airgun HRG sources is to seabirds and waterfowl that dive below the water 

surface and that are exposed to underwater noise. However, most active acoustic sources used for 

G&G activities are directive, with most of the acoustic energy directed toward the seafloor and 

transmitting pulses (impulses) of sound that have very short durations (milliseconds). These factors 

and others suggest that the potential direct impacts of exposure of deep-diving birds to lower 

frequency sound from airguns and non-airgun sound sources are nominal. 

Seabirds and waterfowl may be indirectly impacted by airgun and non-airgun sounds during 

G&G survey activities if these sounds cause their prey to be temporarily displaced from preferred 

feeding areas. However, because of the large area of important bird areas (IBAs), it is unlikely that 

prey would be affected to a level that would impact foraging success, and nominal indirect impacts 

are expected. However, if airgun and HRG surveys potentially temporarily displace species from a 

portion of preferred feeding areas during migration, then minor impacts are expected.

Underwater sound associated with G&G vessels and equipment activities may potentially 

directly impact marine and coastal birds, while attraction to vessels and potential collisions or 

entanglement could indirectly impact these birds. Direct impacts from underwater noise to marine 

and coastal birds are expected to be nominal because of the rapid attenuation of underwater vessel 

noise or species-specific behavior patterns that would significantly reduce the potential for exposure 

to underwater noise. Indirect impacts from collisions or entanglements are expected to be nominal

because of the low potential of such events and because of mortality or serious injury should they 

occur. 
Gulf of Mexico G&G Activities Programmatic EIS xxxiii

Underwater noise from geological test well operations, while within the hearing range of most 

diving seabirds and waterfowl, would decrease rapidly with distance, affecting only a very small 

portion of the AOI and resulting in nominal expected impacts to marine and coastal birds.

Survey vessel underwater noise would significantly attenuate prior to reaching the nearshore 

waters of Bird Conservation Regions (BCRs) and IBAs; therefore, impacts to marine and coastal 

birds using the BCRs and IBAs are expected to be nominal. However, if G&G activities occur 

during migration season, there is the potential for survey vessel and equipment noise to affect 

preferred feeding grounds, disturbing feeding activity or affecting prey abundance. Under such 

circumstances, indirect impacts would be considered minor for diving seabirds and waterfowl.

The G&G survey vessel noise may result in indirect impacts to marine and coastal birds by 

directly impacting prey abundance and distribution within stopover locations. Because foraging 

success would not be expected and impacts would be limited to a very small portion of a bird’s 

foraging range and for a limited time, impacts are expected to be nominal. 

Breeding colonies of marine and coastal birds could potentially be disturbed by airborne 

noise from vessels (including helicopters) and equipment. However, impacts from airborne noise 

are expected to be nominal because birds are expected to choose nesting locations less exposed to 

such noise, and offshore airborne noise would significantly attenuate before reaching the coast. 

Impacts of vessel and equipment noise to nesting or roosting marine and coastal birds in BCRs and 

IBAs from G&G activities would be nominal because the contribution of G&G survey vessels would 

not increase the vessel traffic in these areas. However, if a G&G survey were to take place within 

one of the eight IBAs during offshore foraging activities, the expected impact from vessel and 

equipment noise in these sensitive areas would be minor. 

It is expected that potential impacts from G&G activity-related aircraft traffic and noise would 

range from nominal during non-migration season to minor during migration season. The amount of 

aircraft traffic under Alternative A is expected to be small and of short duration, with little potential to 

cause physical disturbance or collision with marine and coastal birds.

All G&G survey vessels are required to comply with regulations that manage the handling of 

trash and debris. Therefore, the loss of trash and debris from survey vessels is expected to be 

minimal and accidental, and impacts from trash and debris on marine and coastal birds are expected 

to be nominal under Alternative A.

A small accidental fuel spill could directly affect marine and coastal birds by physical oiling of 

individuals and indirectly by the oiling of nesting and foraging habitats and the displacement of 

affected birds to secondary locations. The risk of a spill is considered remote, the area affected by a 

spill would be small, and the spilled fuel is expected to rapidly evaporate and weather. Direct 

impacts to marine and coastal birds are expected to range from nominal to minor, depending on 

the timing and location of the spill. Populations of listed species are already in peril, so an accidental 
xxxiv Executive Summary

fuel spill affecting any individuals of these species or their food supply would result in moderate

impacts. 

Overall, proposed activities associated with the proposed action would increase levels of 

noise and vessel and aircraft within the AOI sporadically when proposed G&G operations were being 

conducted. The proposed action would produce a nominal incremental increase in impacts to 

marine and coastal birds from active acoustic sound sources, vessels and equipment, vessel traffic, 

aircraft traffic and noise, and trash and debris under the cumulative scenario.

Alternative B – Settlement Agreement Alternative: Analysis of the effect on impacts in 

marine and coastal birds of Alternative B mitigation measures concluded that there might be some 

reductions in impacts from the measures. However, the assessment determined that the impact 

level of the overall impacts under Alternative B would remain the same as that under Alternative A. 

The cumulative scenario would remain unchanged for Alternative B, and associated impacts would 

remain the same as under Alternative A (nominal). Alternative B measures would change the 

timing and place restrictions on where surveys could be conducted, but these changes would not 

appreciably change cumulative impacts identified under Alternative A and remain nominal. 

Alternative C – Alternative A Plus Additional Mitigation Measures: The additional 

mitigation measures included in Alternative C might reduce impacts to birds; however, the impact 

analysis found no change in the overall impacts as presented for Alternative A. The cumulative 

scenario remains unchanged from Alternative A for Alternative C since Alternative C measures will 

not decrease overall activities or impacts to birds for the proposed action and so impacts remain 

nominal. 

Alternative D – Alternative C Plus Marine Mammal Shutdowns: The additional mitigation 

measures included in Alternative D would reduce impacts from vessel traffic and noise, but they 

would not affect the timing or severity of other IPFs. The impacts from G&G activities would remain 

the same as found in the previous alternatives. The cumulative scenario would remain the same for 

Alternative D as for Alternative A (nominal), and Alternative D mitigation measures would not 

appreciably change the cumulative impacts found in the Alternatives A and C analyses (nominal).

Alternative E – Alternative C at Reduced Activity Levels: The reductions of 10 and 

25 percent in deep-penetration, multi-client seismic activities under Alternative E would incrementally 

reduce the impacts associated with active acoustic sound sources, vessel and equipment noise, 

vessel traffic, aircraft traffic and noise, and trash and debris. The impact level for IPFs associated 

with routine activities for marine and coastal birds under Alternative E were nominal to moderate, 

depending on the IPF. Impacts from active acoustic noise from airguns would be reduced, and the 

reduced level of activity and impacts would decrease from nominal to minor to nominal under 

Alternative E. Impacts from trash and debris were nominal, while all other IPFs were nominal to 

minor. Analysis determined that the mitigation measures under Alternative E would not appreciably 

change the cumulative impacts found under Alternative A (nominal).
Gulf of Mexico G&G Activities Programmatic EIS xxxv

Alternative F – Alternative C Plus Area Closures: The Alternative F additional mitigation 

measures did not change the extent or severity of the IPFs analyzed. Therefore, impacts to marine 

and coastal birds remained unchanged from that for Alternatives A and C. The area closures and 

restrictions in airgun surveys may decrease impacts under the cumulative scenario; however, 

analysis determined that the mitigation measures under Alternative F would not appreciably change 

from the cumulative impacts found under Alternative A (nominal).

Alternative G – No New Activity Alternative: Under Alternative G, no new G&G activities 

would be permitted, but those already permitted would continue. The reduction in G&G activities 

under Alternative G would decrease the impacts to nominal, eventually declining to no impact. 

Because BOEM would not be authorizing new G&G activity under Alternative G, there would be no 

increase to cumulative impacts, and they would remain the same as Alternative A (nominal). 

Impact Conclusions for Marine Protected Areas

The MPAs are defined areas where natural and/or cultural resources are given greater 

protection than the surrounding waters. The national system of MPAs currently includes 

355 Federal, State, and territorial MPAs. Offshore MPAs within the AOI include national marine 

sanctuaries (NMSs), deepwater MPAs, and fishery management areas. Coastal MPAs include 

national parks, national wildlife refuges, national estuarine research reserves, and State-designated 

MPAs.

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact MPAs within the AOI under 

Alternative A are shown in Table ES-2, and impact levels and resource-specific significance criteria 

applied during impact analysis are discussed in Chapter 4.7.2.

Under Alternative A, seismic airgun surveys are only expected to occur within the planning 

areas and not the entire AOI; therefore, only 10 offshore MPAs could be exposed to direct noise 

from these activities. The other 88 MPAs within the AOI, but outside of the planning areas, could be 

exposed to secondary impacts from propagated noise. Impacts to resources in NMSs would depend 

largely on their distance from G&G survey sound sources. Overall, impacts from transient activities 

to resources in NMSs would be expected to be nominal. Sounds from G&G airgun and non-airgun 

sound sources that propagate into an NMS would likely have no more than temporary effects on 

protected resources within an NMS, and impacts would be expected to be nominal for most 

resources, with the exception of fisheries resources, EFH, and sea turtles (nominal to minor) and 

marine mammals (minor to moderate). Sound from G&G activities is expected to produce minor

impacts on fishes in offshore MPAs if surveys are conducted within the bounds of the MPAs, while 

impacts to other resources within the MPAs are expected to range between nominal and moderate, 

depending on the resource affected. Similarly, the impacts of G&G activity noise for surveys 

conducted within fishery management areas are expected to range between nominal and

moderate, depending on the resource affected. Noise from G&G surveys could affect fishes, 

marine mammals, sea turtles, and benthic communities in coastal MPAs. The impacts to fishes are 
xxxvi Executive Summary

expected to be minor. Impacts to sea turtles and marine mammals are expected to range from 

nominal to moderate, depending on the timing and location of the survey. Impacts to benthic 

organisms, primarily invertebrates, in coastal MPAs from noise generated by G&G surveys are 

expected to be nominal. 

Because of regulations and anticipated compliance with BOEM guidance for management of 

trash and debris, only minimal accidental discharge of trash and debris is expected. Impacts from 

trash and debris generated by survey vessels, sampling, test well drilling, other G&G-related 

activities on MPAs, and the resources within would be nominal. 

The G&G sampling, geological test wells, and anchor placement may disturb the seafloor. 

BOEM would use site-specific information prior to issuing permits to ensure that physical impacts to 

sensitive benthic communities were avoided. Therefore, seafloor-disturbing impacts to sensitive 

benthic communities within MPAs are expected to be nominal. 

The areal extent of impacts from geological test well discharges during the proposed action 

would be small; a typical effect radius of 500 m (1,640 ft) would be expected. Therefore, geological 

test well discharge impacts to sensitive benthic communities within MPAs are expected to be 

nominal. Given restrictions of no disturbance within NMSs and setback requirements for activities 

outside of an NMS, no discharges of geological test well fluids and cuttings would occur within NMS 

waters, and no impacts in an NMS are expected from drilling discharges. No impacts from drilling 

discharges would be expected to benthic communities, submerged archaeological resources, 

fisheries resources and EFH, sea turtles, and marine mammals in offshore MPAs because 

geological test well would not likely be permitted and because of the requirement for site-specific

information prior to authorization of other activities. Because of the small footprint relative to the 

total area of fishery management areas, impacts from geological test well discharges would be 

expected to be nominal in terms of potential impacts on benthic communities, while no impacts to 

submerged archaeological resources, fisheries resources and EFH, sea turtles, and marine 

mammals are expected from geological test well discharges in these fishery management areas.

The likelihood of a small accidental fuel spill during G&G activities in proximity to MPAs is 

considered remote. In terms of all biological resources potentially affected, impacts from accidents 

involving G&G survey vessels that might result in a fuel spill would range from nominal to 

moderate. 

Small fuel spills are unlikely to significantly affect resources within NMSs, Federal fishery 

management areas, and coastal MPAs. Adult fishes would be less susceptible to the effects of 

spilled fuel or oil than would eggs and larvae, and spills are unlikely to affect benthic communities, 

sea turtles, and marine mammals in MPAs. Marine and coastal birds could possibly contact spilled 

fuel and, while individual birds may be oiled, such impacts would be unlikely to have population-level 

effects. However, the threatened and endangered bird species (i.e., the Piping Plover, Roseate 

Tern, and Red Knot) are very susceptible to oiling. Overall, the impacts of a fuel spill would range 
Gulf of Mexico G&G Activities Programmatic EIS xxxvii

from nominal to moderate, depending on the timing and location of the spill and the resource 

affected.

An incremental increase that would range from nominal to minor to cumulative impacts to 

MPAs is expected from active acoustic sound sources under the cumulative scenario, depending on 

the resources affected. A nominal incremental increase in impacts to MPAs from trash and debris, 

seafloor disturbance, geological test well discharges, and accidental fuel spills is expected. 

Alternative B – Settlement Agreement Alternative: While mitigation measures added 

under Alternative B will help reduce direct impacts to MPAs and the biological resources that utilize 

these areas, the impact level remains the same as that for Alternative A. However, while the various 

IPFs remain the same as Alternative A, they have varying impact levels ranging from nominal to 

moderate, depending on the IPF. Alternative B mitigation measures would not change the degree 

of incremental impacts from the proposed action; therefore, the cumulative impacts scenario would 

also remain unchanged from Alternative A and would remain nominal to minor. 

Alternative C – Alternative A Plus Additional Mitigation Measures: Alternative C 

implements the mitigation measures of Alternative A plus additional mitigation measures. Impact 

assessment has determined that the additional measures will reduce potential impacts to MPAs but 

that the impacts will remain nominal to moderate, depending on the affected resource and acting 

IPFs. Again, while the various IPFs remain the same as Alternative A, they have varying impact 

levels ranging from nominal to moderate, depending on the IPF. Alternative C mitigation measures 

would not change the degree of incremental impacts from the proposed action; therefore, the 

cumulative impacts scenario would also remain unchanged from Alternative A, and impacts would 

remain nominal to minor. 

Alternative D – Alternative C Plus Marine Mammal Shutdowns: The additional mitigation 

measures under Alternative D would not appreciably reduce potential impacts from IPFs associated 

with routine activities, and impact levels would remain the same as those for Alternatives A and C 

(nominal to moderate). Again, while the various IPFs remain the same as Alternative A, they have 

varying impact levels ranging from nominal to moderate, depending on the IPF. Alternative D 

mitigation measures would not change the degree of incremental impacts from the proposed action; 

therefore, the cumulative impacts scenario would also remain unchanged from Alternative A, and 

impacts would remain nominal to minor. 

Alternative E – Alternative C at Reduced Activity Level: Alternative E implements 

mitigation measures from Alternatives A and C with reductions of 10 and 25 percent in deep-seismic, 

multi-client activities. The reduction of activity reduces impact potential; however, impacts of routine 

activities are expected to remain nominal to moderate. While the various IPFs remain the same as 

for Alternative A, they have varying impact levels ranging from nominal to moderate, depending on 

the IPF. Alternative E mitigation measures would not change the degree of incremental impacts 

from the proposed action; therefore, the cumulative impacts scenario would also remain unchanged 

from Alternative A (nominal to minor).
xxxviii Executive Summary

Alternative F – Alternative C Plus Area Closures: Alternative F implements mitigation 

measures from Alternatives A and C and adds four area closures. However, while the various IPFs 

remain the same as Alternative A, they have varying impact levels ranging from nominal to 

moderate, depending on the IPF. Alternative F mitigation measures would not change the degree 

of incremental impacts from the proposed action; therefore, the cumulative impacts scenario would 

also remain unchanged from Alternative A (nominal to minor).

Alternative G – No New Activity Alternative: Under Alternative G, no new G&G activities 

would be permitted, but those already permitted would continue. Impacts would be reduced from 

minor to no impact to nominal for HRG surveys and from nominal to no impact to nominal for 

exposure to trash and debris, seafloor disturbance, and geological test well discharges. In addition, 

the impact level would be reduced from nominal to moderate to no impact to nominal for 

accidental fuel spills. The incremental increase in cumulative impacts to MPAs would also be 

reduced from nominal to minor to no impact to nominal under Alternative G.

Impact Conclusions for Sargassum and Associated Communities

Sargassum mats comprise two species of brown algae: Sargassum natans and S. fluitans. 

Each species is entirely pelagic, spending its entire life cycle on the ocean surface. Sargassum can 

be found in mats of varying size and length, and it is temporally and spatially patchy throughout the 

GOM. Pelagic Sargassum mats provide habitat for fauna, including more than 100 species of fish 

and over 100 species of invertebrates such as crabs, shrimp, and mollusks, as well as 4 species of 

sea turtles and many marine birds.

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact Sargassum communities 

within the AOI under Alternative A are shown in Table ES-2, and impact levels and resource-specific 

significance criteria applied during impact analysis are discussed in Chapter 4.8.2. 

The primary potential impact to Sargassum and associated communities from vessel traffic 

associated with G&G surveys is the physical displacement of Sargassum mats as vessels and towed 

equipment pass through large mats. Displaced Sargassum mats would likely re-form via surface 

winds, ocean currents, and gyres once the vessel has passed. Impacts to Sargassum and 

associated communities from G&G vessel traffic would be nominal. 

Vessel discharges could include bilge, ballast, and sanitary and domestic waste. 

Considering the ratio of the affected area (immediately surrounding the survey vessel) to the entire 

AOI and even to the larger area inhabited by Sargassum, it is clear that only a small percentage of 

the total Sargassum population would directly contact operational discharges; therefore, impacts are 

expected to be nominal. 
Gulf of Mexico G&G Activities Programmatic EIS xxxix

Because Sargassum has a temporally and spatially patchy distribution throughout the AOI, 

only a portion of the entire population would come in contact with trash and debris. No measureable 

impact would occur to Sargassum; therefore, impacts would be nominal. 

Due to the widespread and temporally and spatially patchy distribution of Sargassum, most 

fuel spills would only contact a very small portion of the Sargassum population for a very short time, 

resulting in nominal impacts. 

Cumulative impacts to Sargassum from vessel traffic, vessel discharges, and trash and 

debris would result in a nominal incremental increase in the impact to Sargassum and associated 

communities under the cumulative scenario.

Alternatives B through G: The seasonal restriction for airgun survey in coastal waters and 

seismic restrictions in the EPA could reduce impacts to Sargassum, but impact levels for routine 

activities are expected to remain nominal for all IPFs under Alternatives B through F. Impacts under 

Alternative G could be reduced over time from nominal to no impact, depending on whether or not 

there was an increase in exploratory drilling activity. Under the cumulative impacts analyses, the 

restrictions would not result in an appreciable change of impacts for Alternatives B through F, as 

compared with Alternative A, and impacts remain nominal. However, under Alternative G, impacts 

would decrease to no impact up to nominal. 

Impact Conclusions for Commercial Fisheries

The AOI supports regionally and nationally important commercial fisheries. Commercially 

important fish and shellfish species or species groups within the GOM include blue crab, crawfish, 

groupers, menhaden, mullets, oysters, red snapper, shrimp, stone crab, and tunas.

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact commercial fisheries within 

the AOI under Alternative A are shown in Table ES-2, and impact levels and resource-specific 

significance criteria applied during impact analysis are discussed in Chapter 4.9.2. 

The location, timing, and duration of G&G airgun and non-airgun surveys during the project 

period under Alternative A will vary widely depending on survey purpose. The G&G survey sound 

may temporarily affect the behavior of fish, including feeding, spawning, and migration, as well as 

the catch rate of fishers, and may cause TTS and masking. Overall, considering the temporary 

nature of seismic surveys, limited sound exposure of fishes, and the temporary nature of behavioral 

effects to fish that affect the fisheries for commercial stocks, impacts to commercial fisheries from 

exposure to G&G airgun sounds under Alternative A are expected to be minor. Exposure of 

commercial fish stocks to G&G non-airgun HRG sound sources are expected to be localized and 

temporary, and could influence the behavior and hearing of some commercial fisheries resources 

but with no population-level effects. Impacts to commercial fisheries from exposure of fish resources 

to non-airgun G&G sound sources are expected to be nominal. 
xl Executive Summary

Under Alternative A, vessel traffic associated with G&G activities could increase slightly in 

specific areas. However, impacts from G&G-related vessel traffic to commercial fishing under 

Alternative A are expected to be nominal because vessel traffic is relatively high in the AOI and 

G&G activities have been ongoing in the area.

Vessel traffic associated with G&G activities would increase in specific areas, thereby 

increasing the potential for temporary interactions of seismic vessels and commercial fishing vessels 

through stand-off distances and resulting in the potential for direct interference with commercial 

fishing operations. Given the small area typically occupied by the stand-off distance for seismic 

vessels, the short duration of the impact at any given location, and the advance notice provided by 

seismic survey operators, the potential for stand-off distance (space-use conflicts) between G&G 

activities and commercial fishing operations within the AOI will be limited and result in minor

impacts. 

Seafloor disturbance could affect commercial fisheries operations within the AOI, specifically 

the potential for damage to fishing gear placed on the seafloor. Seafloor disturbance caused by 

bottom-sampling activities has the potential to affect unmarked fishing gear or segments of gear 

deployments used by bottom-associated commercial fishing operations. However, the projected 

area of seafloor disturbance under Alternative A is an extremely small area of the AOI. Seafloor 

disturbance and its impact to commercial fishing operations and commercial fishery landings under 

Alternative A are expected to be limited and localized, but potentially overlapping with productive 

fishing grounds; therefore, impacts are expected to be minor. 

Direct impacts to commercial fisheries associated with G&G activities would include 

entanglement or damage to fishing gear. The G&G survey activities would be expected to result in 

an increased risk for entanglement of fishing gear with seismic gear, particularly in nearshore waters 

(<4.8 km [3 mi] from shore) where benthic and demersal inshore fisheries are operating. 

Commercial fisheries and G&G operators are accustomed to cooperatively utilizing the same waters 

and are familiar with the operations and equipment of each other’s industries. Thus, fishing 

equipment could be damaged, but the potential for impacts is reduced by several measures, and any 

impacts would be spatially localized and temporary. Therefore, impacts to commercial fisheries 

landings arising from entanglement are expected to range from nominal to minor. 

Commercially important fishes could be exposed to water-soluble fractions of spilled diesel 

fuel, particularly surface-feeding fishes. It is unlikely that a small diesel fuel spill would have any 

direct impact to commercial fishery landings in the AOI, but misperceptions about the potential for 

contamination of fish caught in the vicinity of a spill could result in a temporary drop in revenue to 

local commercial fishers. Therefore, impacts to commercial fisheries resources from an accidental 

fuel spill would be nominal under Alternative A.

Temporary impacts to fisheries from G&G survey activities have been noted, but G&G 

survey activities are temporary, spatially limited, and distributed non-uniformly in space and time 

over the AOI under Alternative A, so impacts to commercial fisheries are not likely to increase over 
Gulf of Mexico G&G Activities Programmatic EIS xli

time. Therefore, the cumulative effects of exposure to active acoustic sound sources under 

Alternative A are expected to result in minor incremental increases in impacts. Considering the 

long-standing cooperative use of the AOI between commercial fishers and G&G-associated activities 

and advance notice of seismic survey activity, effects from vessel traffic under Alternative A are not 

expected to significantly increase impacts from the cumulative scenario and, under the cumulative 

scenario, a nominal incremental increase in impacts from vessel traffic on commercial fisheries is 

expected. Seafloor disturbances under Alternative A are expected to be few, to impact an extremely 

small portion of the AOI, and to be distributed in space and time, and their impacts are not likely to 

increase over time. The cumulative effects of seafloor disturbance are expected to result in a 

nominal incremental increase under Alternative A. Overall, proposed activities are expected to 

result in nominal to minor incremental increases in impacts to commercial fisheries.

Alternative B – Settlement Agreement Alternative: The closures of coastal waters and a 

restriction of seismic surveys in the AOI under Alternative B would likely provide benefits to coastal 

fish stocks, but they would otherwise not significantly change the exposure of commercial fisheries 

to the impacts of routine G&G activities. The impacts from routine G&G activities are expected to 

remain nominal to minor, depending on IPF. Under Alternative B, there would be no increase to 

cumulative impacts, and so would remain the same as Alternative A (nominal to minor).

Alternative C – Alternative A Plus Additional Mitigation Measures: Only the extension 

of seasonal restriction on airgun surveys in coastal waters under Alternative C would potentially 

reduce impacts to some coastal fish stocks, but it would not affect the conduct of G&G activities 

though the majority of the AOI. The impacts of routine activities are expected to remain nominal to 

minor, depending on IPF. Under Alternative C, there would be no increase to cumulative impacts 

and so would remain the same as Alternative A (nominal to minor).

Alternative D – Alternative C Plus Marine Mammal Shutdowns: The additional mitigation 

measure of shutdowns for all marine mammals, except for bow-riding dolphins, under Alternative D 

would not affect commercial fisheries, and impacts of routine G&G activities would remain nominal

to minor, depending on IPF. Under Alternative D, there would be no increase to cumulative impacts 

and so would remain the same as Alternative A (nominal to minor).

Alternative E – Alternative C at Reduced Activity Levels: Reductions in the level of 

deep-penetration, multi-client seismic surveys under Alternative E will not, with the exception of 

stand-off distance and entanglement, significantly reduce the exposure of commercial fisheries to 

G&G activities throughout the AOI, and impacts are expected to remain nominal to minor, 

depending on the IPF. Stand-off distance and entanglement impacts are reduced to nominal under 

Alternative E2. Under Alternative E, there would be no increase to cumulative impacts and so would 

remain the same as Alternative A (nominal to minor).

Alternative F – Alternative C Plus Area Closures: Alternative F mitigation measures 

include the closure of four areas to all G&G activities. These closures will provide some benefits to 

some fish species and commercial fisheries, but they will not affect the impact of routine G&G 
xlii Executive Summary

activities through the majority of the AOI. Impacts to commercial fisheries are expected to remain in 

the same range as Alternative A (nominal to minor). Under Alternative F, there would be no 

increase to cumulative impacts and so would remain the same as Alternative A (nominal to minor).

Alternative G – No New Activity Alternative: Under Alternative G, no new G&G activities 

would be permitted and the impacts of routine G&G activities would decrease over time as G&G 

activities are phased out. Impacts to commercial fisheries would generally decrease from those 

described under Alternative A to nominal, eventually declining to no impact, across all IPFs. Under 

Alternative G, there would be a concomitant decrease in cumulative impacts to nominal as 

compared with nominal to minor for all other alternatives.

Impact Conclusions for Recreational Fisheries

Saltwater recreational fishing, a year-round activity throughout the AOI, is an important social 

and economic activity, and those recreational fisheries adjacent to the AOI are among the most 

valuable in the U.S. Saltwater recreational fisheries can be classified as nearshore or offshore, 

depending on the size of the vessel and its fishing location (<4.8 km [3 mi] from shore for nearshore 

and >4.8 km [3 mi] from shore for offshore).

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact recreational fisheries within 

the AOI under Alternative A are shown in Table ES-2, and impact levels and resource-specific 

significance criteria applied during impact analysis are discussed in Chapter 4.10.2. 

Based on research results of the effects of airgun and other active acoustic sound sources 

on fish and due to the mitigation measures in place, it is unlikely that the sounds produced by 

airguns for seismic surveys and electromechanical sources for non-airgun HRG surveys would 

cause injury or mortality to recreationally important fishes (e.g., reef, coastal, and pelagic species). 

In general, temporary impacts to fish hearing and behavior are more likely. However, changes in 

fish behavior and hearing will not occur in all fish species and effects will be temporary. Therefore, 

there will be little or no measurable impacts to reef fishes, coastal fishes, or pelagic fishes. Impacts 

on reef fishes, coastal fishes, and pelagic fishes as a component of recreational fisheries would be 

nominal. 

Given the absence of serious injury or mortality to recreational fishes and the low potential 

for behavioral changes from exposure to airguns used for seismic surveys and electromechanical 

sources for non-airgun HRG surveys, it is likely that potential impacts to recreational fishers would 

be intermittent, temporary, and short term in duration or frequency. Exposure to active acoustic 

sound sources (e.g., seismic airgun and electromechanical sounds) from G&G activities is expected 

to produce nominal impacts to recreational fisheries activities.

Inshore fisheries (i.e., estuaries and bays) are not expected to be affected by vessel traffic 

and stand-off distance issues because they are outside of the AOI; however, coastal inlets would still 
Gulf of Mexico G&G Activities Programmatic EIS xliii

be susceptible to impacts from G&G activities. Effects are likely to be localized, intermittent in 

frequency of occurrence, temporary, and short term in nature. Therefore, vessel traffic disturbance 

and how it relates to recreational fishing activities would be expected to produce nominal impacts. 

The G&G activities and associated stand-off distance are expected to have no indirect 

effects on recreational fishery operations unless these activities cause recreational anglers to 

concentrate their fishing efforts on other species or areas. Impacts to recreational fisheries 

associated with stand-off distance under Alternative A are expected to be nominal. 

In the event of a small fuel spill, recreational fishing activity is not expected to be precluded 

from the area around the fuel source; spilled diesel would evaporate and disperse within a day or 

less. Given the relatively small size of the fuel spill and the rapid loss of most spilled fuel through 

evaporation and dispersion, a small diesel fuel spill at the surface would have little to no effect on 

recreational fisheries. An accidental fuel spill would be expected to result in nominal impacts to 

recreational fisheries.

While G&G activities under Alternative A would sporadically increase noise levels and vessel 

and aircraft traffic and other IPFs within the AOI, activities would be concentrated offshore with little 

activity planned for the EPA. Because the majority of fishing is done in State waters, a nominal

incremental increase in impacts to recreational fisheries is expected when the IPFs associated with 

G&G activities under Alternative A are added to activities in the cumulative scenario.

Alternatives B through G: Here, additional mitigation measures under Alternatives B 

through F may provide some benefits to recreational fisheries, mainly to some coastal and oceanic

fish stocks, but will otherwise not alter impacts from routine G&G activities in the AOI that have been 

assessed to be nominal. As in the analysis for commercial fisheries, the additional mitigation 

measures under Alternative B may provide some benefits to recreational fisheries, mainly to some 

coastal and oceanic fish stocks, but will otherwise not alter impacts from routine G&G activities in the 

AOI. The only mitigation measure under Alternative C that might affect recreational fisheries is the 

seasonal restriction on seismic airgun operations in coastal waters. Because routine G&G activities 

will continue through the rest of the AOI, potential benefits are minimal. None of the mitigation 

measures under Alternative D will benefit recreational fisheries beyond those discussed in 

Alternative A. Reductions in deep-penetration, multi-client seismic airgun surveys under 

Alternative E would reduce exposure of fish and recreational fisheries to impacts from active 

acoustic sound sources. However, airgun surveys would still occur throughout the AOI, and impacts 

to recreational fisheries are expected to remain unchanged. The area closures of Alternative F 

would benefit recreational fisheries within and near the closure areas, but they would have no effect 

throughout the rest of the AOI. The impacts from all IPFs under Alternatives B through F remain 

nominal. Under Alternative G, impacts from routine activities would not change immediately but 

would eventually decline from nominal to no impact as activities were phased out. There would be 

a nominal incremental increase in impacts to recreational fisheries under the cumulative impacts 

analysis scenario, and this remains consistent across all alternatives.
xliv Executive Summary

Impact Conclusions for Archaeological Resources

The AOI holds the potential to contain unknown historic shipwrecks and prehistoric sites. 

Shipwrecks within the AOI date from the 16th century until modern times. Research has also shown 

the possibility of prehistoric resources in the AOI. Archaeological evidence indicates that the GOM 

region was first occupied approximately 12,000 B.P.

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact archaeological resources 

within the AOI under Alternative A are shown in Table ES-2, and impact levels and resource-specific 

significance criteria applied during impact analysis are discussed in Chapter 4.11.2. 

The depth distribution of submerged cultural resources is an important consideration when 

evaluating the potential impact. While historic shipwrecks may occur at any water depth within the 

AOI, prehistoric resources are limited to depths <60 m (197 ft). Impacts to archaeological resources 

from seafloor disturbance and entanglement would likely result in nominal to major impacts 

depending on the type of survey and whether or not site-specific information regarding potential 

archaeological resources is available.

Avoidance of archaeological resources and the immediate reporting of unanticipated 

discoveries to BOEM are expected to prevent a serious impact to archaeological resources. Given 

BOEM’s requirement for site-specific information regarding archaeological resources for all 

geological test well activities, impacts from geological test well discharges in the AOI are expected to 

be nominal. 

Given the relatively small size of anticipated fuel spills and the loss of most spilled fuel 

through evaporation and dispersion, a small diesel fuel spill at the surface would have no effect on 

the seafloor and would not require seafloor cleanup activity. An accidental diesel fuel spill would be 

expected to result in nominal impacts to archaeological resources.

BOEM requires site-specific information regarding archaeological resources prior to 

approving G&G activities that might impact archaeological resources. This review process is 

expected to limit impacts to archaeological resources from G&G activities under Alternative A. 

Therefore, overall, the potential cumulative impacts to archaeological resources under Alternative A 

would result in a nominal incremental increase in impacts from seafloor disturbance and geological 

test well discharges. Vessel traffic management systems, along with other measures, limit the 

potential of vessel collisions and further reduce the likelihood of an accidental fuel spill, which is 

considered low. The impacts associated with G&G activities under Alternative A that might impact 

archaeological resources would result in a nominal incremental increase in cumulative impacts to 

archaeological resources.

Alternatives B through G: The additional mitigation measures included in Alternatives B 

through F do not change the impact assessment from Alternative A for archaeological resources 
Gulf of Mexico G&G Activities Programmatic EIS xlv

(nominal to major). Incremental increases in impacts under the cumulative activities scenario 

remain the same as under Alternative A (nominal). However, under Alternative G, no new G&G 

activities would be permitted and the impact level would be reduced from nominal to major, as seen 

in Alternatives A through F, to no impact (seafloor disturbance, entanglement and geological test 

well discharges) and nominal declining to no impact (accidental fuel spills).

Impact Conclusions for Other Marine Uses

Other uses of the marine environment in the AOI include shipping and other marine traffic, 

military warning areas, sand and gravel mining, renewable energy development, ODMDSs, oil and 

gas exploration and production, commercial and recreation fishing, recreational resources, tourism, 

and human resources.

Alternative A – Pre-Settlement (June 2013) Alternative: The mitigation measures applied 

under Alternative A are shown in Table ES-1. The IPFs that may impact other marine uses within 

the AOI under Alternative A are shown in Table ES-2, and impact levels and resource-specific 

significance criteria applied during impact analysis are discussed in Chapter 4.12.2. 

Based on the vessel traffic and associated stand-off distances, aircraft traffic, and seafloor 

disturbance expected under G&G activities, impacts to shipping and marine transport, military, sand 

and gravel, renewable energy, ODMDSs, oil and gas activities, and infrastructure are expected to 

range from no impact to nominal because of the level of G&G-related activity involved and because

the duration of these surveys is short in relation to the existing vessel traffic throughout the AOI. 

There would not be a sufficient increase in vessel or aircraft traffic or seafloor disturbances to impact 

the other marine uses activities existing in the AOI.

The impacts of an accidental spill event would depend on the size and location of the spill, in 

addition to the meteorological conditions at the time. If a small diesel spill were to occur, it would 

have a nominal impact on other marine uses because it would only prohibit full use of a small area 

by other marine users for a very limited amount of time.

The contribution of G&G activities under Alternative A to the existing cumulative activities in 

the cumulative scenario would be a nominal incremental increase in impacts from vessel or aircraft 

traffic or seafloor disturbances to the other marine uses activities existing in the AOI.

Alternatives B through G: Mitigation measures included in Alternatives B through F do not 

change the impact assessment from Alternative A for other marine uses (no impact to nominal). 

Similarly, under Alternative G, impacts to other marine uses would remain the same (no impact to 

nominal), eventually declining to no impact as activities were phased out. Cumulative impacts to 

other marine uses would result in nominal incremental increases under Alternative G.
xlvi Executive Summary

Impact Conclusions for Human Resources and Land Use

The onshore portion of the AOI extends along the GOM coastline from the southwestern tip 

of the Florida Keys to the southern coast of Texas. The area encompasses 133 counties/parishes in 

23 BOEM-designated Economic Impact Areas. The G&G activities in the GOM have a concurrent 

impact on the human environment onshore, including land use and coastal infrastructure, 

environmental justice, demographics, and socioeconomic aspects of the communities along the Gulf 

Coast. Activities in the OCS are supported by onshore facilities, which can impact the human 

environment.

The G&G activities under the proposed action would have no impact on human resources 

and land use in the Gulf Coast area. Subcomponents, including land use and infrastructure, 

environmental justice, demographics, and socioeconomics, would not be impacted because all G&G 

activities would occur on the OCS and have been occurring for the past 30 years. Nominal to 

minor impacts may occur to the local and regional economy as well as to the coastal infrastructure, 

resulting from changes in employment and earnings in the G&G service sector under two of the 

alternatives that include reductions in survey activities.

Alternative A – Pre-Settlement (June 2013) Alternative: No impact is expected to occur 

on human resources and land use in the AOI as a result of Alternative A. The G&G activities are 

projected to remain at current levels; therefore, this alternative is not expected to impact the size or 

structure of the existing G&G industry. In addition, employment and earnings in this industry are not 

expected to change; therefore, no secondary impacts to demographics, socioeconomics, 

environmental justice, or land use are expected to occur under this alternative.

Alternative B – Settlement Agreement Alternative: Under Alternative B, BOEM would 

continue to authorize the current level of G&G activity through the use of site-specific NEPA 

evaluations, lease stipulations, NTLs, best management practices, and COAs issued since the 

Settlement Agreement was issued. Similar to Alternative A, no impact is expected to occur on 

human resources and land use. Under Alternative B, there would be no increase to cumulative 

impacts; therefore, the impact determination remains the same as Alternative A (no impact).

Alternative C – Alternative A Plus Additional Mitigation Measures: Under Alternative C, 

BOEM would continue to authorize the current level of G&G activity and include mitigation 

measures, monitoring, reporting, survey protocols, and guidance in place under Alternative A, as 

well as additional mitigation measures for survey protocols for airgun and non-airgun HRG surveys. 

Similar to the previous alternatives discussed, no impact is expected to occur on human resources 

and land use. Under Alternative C, there would be no increase to cumulative impacts; therefore, the 

impact determination remains the same as Alternative A (no impact).

Alternative D – Alternative C Plus Marine Mammal Shutdowns: Under Alternative D, 

BOEM would continue to authorize the current level of G&G activity and include the mitigation 

measures, monitoring, reporting, survey protocols, and guidance included in Alternative C with the 
Gulf of Mexico G&G Activities Programmatic EIS xlvii

addition of shutdowns for all marine mammals within the exclusion zone, except bow-riding dolphins. 

Similar to the previous alternatives discussed, no impact is expected to occur to human resources 

and land use under this alternative. Under Alternative D, there would be no increase to cumulative 

impacts; therefore, the impact determination remains the same as Alternative A (no impact).

Alternative E – Alternative C at Reduced Activity Levels: Under Alternative E, all 

mitigation measures and protocols described in Alternative C would be followed; however, BOEM 

would require a reduced level of activity (calculated in line miles) for deep-penetration, multi-client 

seismic airgun surveys. Alternative E has two proposed reduction options in seismic airgun survey 

activities: a 10-percent reduction proposed in Alternative E1 and a 25-percent reduction for 

Alternative E2. The reduction of deep-penetration, multi-client seismic activities would lead to a 

corresponding reduction in the size of the G&G industry in the GOM and would result in an increase 

of impacts on human resources and land use from no impact under the previous alternatives to 

nominal to minor impacts, depending upon the IPF. Consequently, under Alternative E there would 

be an increase in cumulative impacts from no impact in previous alternatives to minor. 

Alternative F – Alternative C Plus Area Closures: Under Alternative F, BOEM would 

continue to authorize the current level of G&G activity and include mitigation measures, monitoring, 

reporting, survey protocols, and guidance under Alternative C with the addition of four area closures 

(except for non-airgun HRG surveys operating at frequencies >200 kHz). The closure areas are

designed to provide additional protection for certain cetacean species and other resources. No 

impact is expected to human resources and land use in the GOM as a result of this alternative. 

Under Alternative F, there would be no increase to cumulative impacts; therefore, the impact 

determination remains the same as Alternative A (no impact).

Alternative G – No New Activity Alternative: Under Alternative G, no new G&G activities 

associated with the development of oil and gas reserves, renewable energy, or marine materials 

would be authorized to occur within the AOI during the time period covered by this Programmatic 

EIS. Other G&G survey activities would be unaffected, including any that occur within State waters; 

those that are for scientific studies and regulated by other Federal agencies; and any BOEM nonregulated G&G activities (i.e., geophysical surveys for archaeological and benthic resources). In the 

short-term, G&G activities already approved would be allowed to continue for the duration of their 

authorized permits/approvals; however, no additional permits would be approved. In the long-term, 

all BOEM-regulated G&G activities in the GOM would cease upon maturity of the permits/approvals, 

resulting in negative economic impacts on the G&G industry. Potential impacts would increase to 

minor under Alternative G for human resources and land use. Cumulative impacts under 

Alternative G would increase to moderate as compared with Alternative A (no impact).

Gulf of Mexico G&G Activities Programmatic EIS xlix

TABLE OF CONTENTS

Volume I

Page

EXECUTIVE SUMMARY ..................................................................................................................... vii

LIST OF FIGURES.............................................................................................................................lxvii

LIST OF TABLES................................................................................................................................lxix

ABBREVIATIONS AND ACRONYMS ..............................................................................................lxxiiI

CONVERSION CHART ....................................................................................................................lxxix

1 INTRODUCTION ............................................................................................................................ 1-3

1.1 Proposed Action and Purpose and Need............................................................................. 1-3

1.1.1 Proposed Action....................................................................................................... 1-3 

1.1.2 Purpose and Need................................................................................................... 1-4 

1.1.3 Area of Interest......................................................................................................... 1-5 

1.2 Background .......................................................................................................................... 1-6

1.2.1 History of G&G Environmental Review in the GOM................................................ 1-7 

1.2.2 Petition for Authorization to Take Marine Mammals Incidental to Conducting 

Oil and Gas Exploration Activities in the Gulf of Mexico ......................................... 1-8 

1.2.3 Litigation Settlement ................................................................................................ 1-9 

1.2.4 Environmental Baseline and the Deepwater Horizon Explosion, Oil Spill, and 

Response ............................................................................................................... 1-14

1.2.5 Exposure Versus Take of Listed Species.............................................................. 1-15

1.2.6 NMFS’ Acoustic Guidelines ................................................................................... 1-17

1.2.7 Risk Assessment Framework ................................................................................ 1-20

1.3 Regulatory Framework ....................................................................................................... 1-22

1.3.1 Federal Laws, Regulations, and Agreements........................................................ 1-22

1.3.2 State Laws, Regulations, and Agreements ........................................................... 1-23

1.4 Programmatic Approach to the NEPA Process ................................................................. 1-23

1.5 Objectives and Scope ........................................................................................................ 1-25

2 ALTERNATIVES INCLUDING THE PROPOSED ACTION ........................................................... 2-3

2.1 Overview............................................................................................................................... 2-3

2.2 Additional Information Applicable to the Alternatives........................................................... 2-3

2.3 Alternative A – Pre-Settlement (June 2013) Alternative ...................................................... 2-7

2.3.1 Description ............................................................................................................... 2-7 

2.3.2 Mitigation Measures................................................................................................. 2-7 

2.3.3 Rationale.................................................................................................................. 2-8 

2.4 Alternative B – Settlement Agreement Alternative............................................................... 2-8

2.4.1 Description ............................................................................................................... 2-8 

2.4.2 Mitigation Measures................................................................................................. 2-9 

2.4.3 Rationale................................................................................................................ 2-10

2.5 Alternative C – Alternative A Plus Additional Mitigation Measures.................................... 2-11

2.5.1 Description ............................................................................................................. 2-11

2.5.2 Mitigation Measures............................................................................................... 2-11

2.5.3 Rationale................................................................................................................ 2-12
l Table of Contents

2.6 Alternative D – Alternative C Plus Marine Mammal Shutdowns........................................ 2-12

2.6.1 Description ............................................................................................................. 2-12

2.6.2 Mitigation Measures............................................................................................... 2-13

2.6.3 Rationale................................................................................................................ 2-14

2.7 Alternative E – Alternative C At Reduced Activity Levels .................................................. 2-14

2.7.1 Description ............................................................................................................. 2-14

2.7.2 Mitigation Measures............................................................................................... 2-14

2.7.3 Rationale................................................................................................................ 2-16

2.8 Alternative F – Alternative C Plus Area Closures .............................................................. 2-16

2.8.1 Description ............................................................................................................. 2-16

2.8.2 Mitigation Measures............................................................................................... 2-16

2.8.3 Rationale................................................................................................................ 2-17

2.9 Alternative G – No New Activity Alternative....................................................................... 2-19

2.9.1 Description ............................................................................................................. 2-19

2.9.2 Mitigation Measures............................................................................................... 2-20

2.9.3 Rationale................................................................................................................ 2-21

2.10 Issues ................................................................................................................................. 2-21

2.10.1 Issues to be Analyzed............................................................................................ 2-21

2.10.2 Issues Considered but Not Analyzed .................................................................... 2-23

2.11 Alternatives Considered but Not Carried Forward ............................................................. 2-24

2.11.1 Shutdown for All Marine Mammals Within the Level A Harassment Exclusion 

Zone ..................................................................................................................... 2-24

2.11.2 Require Alternative Technology Use..................................................................... 2-24

2.11.3 Requirement to Obtain an LOA or IHA Prior to Receiving BOEM’s G&G 

Approval ................................................................................................................. 2-26

2.12 Mitigation Measures Considered But Not Carried Forward ............................................... 2-27

2.12.1 Active Acoustic Monitoring..................................................................................... 2-27

2.12.2 Aerial Surveys........................................................................................................ 2-28

2.13 Comparison of Impacts by Alternative ............................................................................... 2-29

2.14 Mitigation, Monitoring, and Effectiveness .......................................................................... 2-36

2.14.1 Time and Area Restrictions and Closures............................................................. 2-37

2.14.2 Minimum Separation Distances............................................................................. 2-38

2.14.3 Non-Duplicative Surveys and Lowest Practicable Source .................................... 2-39

2.14.4 Exclusion Zone....................................................................................................... 2-40

2.14.5 Exclusion Zone Monitoring .................................................................................... 2-41

2.14.6 Ramp-Up................................................................................................................ 2-45

2.14.7 Shutdowns of Sources for Protected Species ....................................................... 2-46

2.14.8 Reduction in G&G Activity Levels.......................................................................... 2-47

3 G&G ACTIVITIES AND PROPOSED ACTION SCENARIO.......................................................... 3-3

3.1 Introduction........................................................................................................................... 3-3

3.2 Proposed Action Scenario by Program Area ....................................................................... 3-3

3.2.1 Oil and Gas Program G&G Surveys........................................................................ 3-4 

3.2.1.1 Proposed Action Scenario......................................................................... 3-4

3.2.1.2 Projected Activity Levels ........................................................................... 3-5

3.2.2 Renewable Energy Program G&G Surveys ............................................................ 3-6 

3.2.2.1 Proposed Action Scenario......................................................................... 3-7

3.2.2.2 Projected Activity Levels ........................................................................... 3-9

3.2.3 Marine Minerals Program G&G Surveys ................................................................. 3-9 

3.2.3.1 Proposed Action Scenario....................................................................... 3-11

3.2.3.2 Projected Activity Levels ......................................................................... 3-14
Gulf of Mexico G&G Activities Programmatic EIS li

3.3 Impact-Producing Factors from the Proposed Action........................................................ 3-16

3.3.1 Impact-Producing Factors for Routine Activities ................................................... 3-17

3.3.1.1 Active Acoustic Sound Sources .............................................................. 3-17

3.3.1.1.1 Airguns.................................................................................. 3-17

3.3.1.1.2 Non-Airgun (Electromechanical) HRG Sources................... 3-18

3.3.1.2 Vessel and Equipment Noise.................................................................. 3-19

3.3.1.2.1 Vessel Noise......................................................................... 3-19

3.3.1.2.2 Equipment Noise Including Drilling Noise ............................ 3-20

3.3.1.3 Vessel Traffic........................................................................................... 3-21

3.3.1.3.1 Surveys for Oil and Gas Exploration .................................... 3-22

3.3.1.3.2 Renewable Energy Surveys ................................................. 3-23

3.3.1.3.3 Marine Minerals Surveys...................................................... 3-24

3.3.1.4 Aircraft Traffic and Noise......................................................................... 3-25

3.3.1.5 Stand-Off Distance.................................................................................. 3-26

3.3.1.6 Vessel Discharges................................................................................... 3-27

3.3.1.7 Trash and Debris..................................................................................... 3-27

3.3.1.8 Seafloor Disturbance............................................................................... 3-29

3.3.1.8.1 Seafloor or Bottom Sampling Activities ................................ 3-30

3.3.1.8.2 Placement of Anchors, Nodes, Cables, and Sensors.......... 3-30

3.3.1.8.3 COST Wells and Shallow Test Drilling................................. 3-31

3.3.1.8.4 Bottom-Founded Monitoring Buoys ...................................... 3-31

3.3.1.9 Drilling Discharges .................................................................................. 3-32

3.3.1.10 Entanglement .......................................................................................... 3-33

3.3.2 Impact-Producing Factors for Accidental Fuel Spills............................................. 3-33

3.4 Cumulative Activities Scenario........................................................................................... 3-34

3.4.1 OCS Program......................................................................................................... 3-36

3.4.1.1 OCS Oil and Gas Exploration and Development.................................... 3-37

3.4.1.2 Decommissioning.................................................................................... 3-38

3.4.1.3 Renewable Energy Development............................................................ 3-39

3.4.1.4 Marine Minerals Use ............................................................................... 3-39

3.4.2 Oil and Gas Activities in State Waters................................................................... 3-40

3.4.3 Other Major Factors Affecting Offshore Environments ......................................... 3-41

3.4.3.1 Deepwater Ports...................................................................................... 3-41

3.4.3.2 Commercial and Recreational Fishing.................................................... 3-41

3.4.3.3 Shipping and Marine Transportation....................................................... 3-43

3.4.3.4 Dredged Material Disposal...................................................................... 3-44

3.4.3.5 Existing, Planned, and New Cable Infrastructure ................................... 3-44

3.4.3.6 Military Activities...................................................................................... 3-45

3.4.3.7 Scientific Research.................................................................................. 3-46

3.4.3.8 Maintenance Dredging of Federal Channels .......................................... 3-47

3.4.3.9 Coastal Restoration Programs................................................................ 3-47

3.4.3.10 Mississippi River Hydromodification and Subsidence ............................ 3-47

3.4.3.11 Ancillary Considerations.......................................................................... 3-48

4 DESCRIPTION OF THE AFFECTED RESOURCES AND IMPACT ANALYSIS .......................... 4-3

4.1 Introduction........................................................................................................................... 4-3

4.1.1 Preliminary Screening of Activities and Affected Resources .................................. 4-4 

4.1.1.1 Activity Screening...................................................................................... 4-5

4.1.1.2 Resource Screening.................................................................................. 4-5

4.1.2 Impact Levels and Impact Significance Criteria ...................................................... 4-8 

4.1.3 Impact-Producing Factors........................................................................................ 4-9 
lii Table of Contents

4.1.4 Other Considerations............................................................................................. 4-10

4.1.4.1 Analysis and Incomplete or Unavailable Information.............................. 4-10

4.1.4.2 Cumulative Scenario Summary............................................................... 4-11

4.1.4.3 NMFS’ Acoustic Guidelines..................................................................... 4-12

4.1.4.4 Risk Assessment Framework.................................................................. 4-15

4.1.4.5 Space-Use Conflicts................................................................................ 4-17

4.1.5 Effects of the Deepwater Horizon Oil Spill............................................................. 4-18

4.2 Marine Mammals................................................................................................................ 4-21

4.2.1 Description of the Affected Environment ............................................................... 4-21

4.2.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)........................ 4-25

4.2.2.1 Impacts of Routine Activities ................................................................... 4-27

4.2.2.1.1 Characteristics of Active Acoustic Sound Sources .............. 4-27

4.2.2.1.2 Analysis of Active Acoustic Sound Sources......................... 4-50

4.2.2.1.3 HRG Survey Activities .......................................................... 4-60

4.2.2.1.4 Vessel and Equipment Noise ............................................... 4-66

4.2.2.1.5 Drilling-Related Noise........................................................... 4-69

4.2.2.1.6 Vessel Traffic........................................................................ 4-70

4.2.2.1.7 Aircraft Traffic and Noise...................................................... 4-71

4.2.2.1.8 Trash and Debris .................................................................. 4-73

4.2.2.1.9 Entanglement........................................................................ 4-74

4.2.2.1.10 Routine Activities Impact Conclusions ................................. 4-75

4.2.2.2 Impacts of Accidental Events .................................................................. 4-76

4.2.2.3 Cumulative Impacts................................................................................. 4-77

4.2.2.3.1 Noise..................................................................................... 4-77

4.2.2.3.2 Vessel and Aircraft Traffic .................................................... 4-83

4.2.2.3.3 Trash and Debris .................................................................. 4-84

4.2.2.3.4 Entanglement........................................................................ 4-85

4.2.2.3.5 Cumulative Impact Conclusions ........................................... 4-85

4.2.2.3.6 Accidental Fuel Spills ........................................................... 4-87

4.2.3 Impacts – Alternative B (Settlement Agreement Alternative)................................ 4-88

4.2.3.1 Impacts of Routine Activities ................................................................... 4-88

4.2.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to 

April 30)................................................................................. 4-88

4.2.3.1.2 Expanded PSO Program...................................................... 4-91

4.2.3.1.3 Minimum Separation Distances............................................ 4-92

4.2.3.1.4 Seismic Restrictions in the Areas of Concern within the 

EPA....................................................................................... 4-94

4.2.3.1.5 Use of PAM Required........................................................... 4-95

4.2.3.1.6 Routine Activities Impact Conclusions ................................. 4-97

4.2.3.2 Impacts of Accidental Events .................................................................. 4-98

4.2.3.3 Cumulative Impacts................................................................................. 4-98

4.2.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures).............................................................................................. 4-99

4.2.4.1 Impacts of Routine Activities .................................................................4-100

4.2.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to 

May 31)...............................................................................4-100

4.2.4.1.2 Expanded PSO Program....................................................4-100

4.2.4.1.3 Use of PAM Required.........................................................4-101

4.2.4.1.4 Non-Airgun HRG Survey Protocol......................................4-102

4.2.4.1.5 Routine Activities Impact Conclusions ...............................4-103

4.2.4.2 Impacts of Accidental Events ................................................................4-104

4.2.4.3 Cumulative Impacts...............................................................................4-105
Gulf of Mexico G&G Activities Programmatic EIS liii

4.2.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns) .........4-105

4.2.5.1 Impacts of Routine Activities .................................................................4-106

4.2.5.1.1 Expanded PSO Program with Additional Shutdowns ........4-106

4.2.5.1.2 Routine Activities Impact Conclusions ...............................4-106

4.2.5.2 Impacts of Accidental Events ................................................................4-108

4.2.5.3 Cumulative Impacts...............................................................................4-108

4.2.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-109

4.2.6.1 Impacts of Routine Activities .................................................................4-109

4.2.6.1.1 Reduced Level of Activity ...................................................4-109

4.2.6.1.2 Routine Activities Impact Conclusions ...............................4-110

4.2.6.2 Impacts of Accidental Events ................................................................4-111

4.2.6.3 Cumulative Impacts...............................................................................4-111

4.2.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-112

4.2.7.1 Impacts of Routine Activities .................................................................4-112

4.2.7.1.1 Closure Areas.....................................................................4-112

4.2.7.1.2 Routine Activities Impact Conclusions ...............................4-117

4.2.7.2 Impacts of Accidental Events ................................................................4-119

4.2.7.3 Cumulative Impacts...............................................................................4-119

4.2.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-120

4.2.8.1 Impacts of Routine Activities .................................................................4-120

4.2.8.1.1 Active Acoustic Sources.....................................................4-120

4.2.8.1.2 Vessel and Equipment Noise .............................................4-121

4.2.8.1.3 Vessel Traffic......................................................................4-121

4.2.8.1.4 Aircraft Traffic and Noise....................................................4-121

4.2.8.1.5 Trash and Debris ................................................................4-121

4.2.8.1.6 Routine Activities Impact Conclusions ...............................4-121

4.2.8.2 Impacts of Accidental Events ................................................................4-123

4.2.8.3 Cumulative Impacts...............................................................................4-123

4.3 Sea Turtles .......................................................................................................................4-123

4.3.1 Description of the Affected Environment .............................................................4-123

4.3.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-126

4.3.2.1 Impacts of Routine Activities .................................................................4-127

4.3.2.1.1 Characteristics of Active Acoustic Sound Sources ............4-127

4.3.2.1.2 Analysis of Active Acoustic Sound Sources.......................4-135

4.3.2.1.3 Vessel and Equipment Noise .............................................4-139

4.3.2.1.4 Vessel Traffic......................................................................4-141

4.3.2.1.5 Aircraft Traffic and Noise....................................................4-142

4.3.2.1.6 Trash and Debris ................................................................4-143

4.3.2.1.7 Entanglement/Entrapment..................................................4-145

4.3.2.1.8 Routine Activities Impact Conclusions ...............................4-145

4.3.2.2 Impacts of an Accidental Fuel Spill .......................................................4-146

4.3.2.3 Cumulative Impacts...............................................................................4-148

4.3.2.3.1 Noise...................................................................................4-148

4.3.2.3.2 Vessel and Aircraft Traffic ..................................................4-151

4.3.2.3.3 Trash and Debris ................................................................4-152

4.3.2.3.4 Entanglement and Entrapment...........................................4-152

4.3.2.3.5 Cumulative Impact Conclusions .........................................4-153

4.3.2.3.6 Accidental Fuel Spills .........................................................4-154

4.3.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-155

4.3.3.1 Impacts of Routine Activities .................................................................4-155

4.3.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to 

April 30)...............................................................................4-155

4.3.3.1.2 Expanded PSO Program....................................................4-157
liv Table of Contents

4.3.3.1.3 Minimum Separation Distances..........................................4-158

4.3.3.1.4 Seismic Restrictions in the Areas of Concern within the 

EPA.....................................................................................4-159

4.3.3.1.5 Routine Activities Impact Conclusions ...............................4-160

4.3.3.2 Impacts of an Accidental Fuel Spill .......................................................4-160

4.3.3.3 Cumulative Impacts...............................................................................4-161

4.3.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-162

4.3.4.1 Impacts of Routine Activities .................................................................4-162

4.3.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to 

May 31)...............................................................................4-162

4.3.4.1.2 Expanded PSO Program....................................................4-162

4.3.4.1.3 Non-Airgun HRG Survey Protocol......................................4-163

4.3.4.1.4 Routine Activities Impact Conclusions ...............................4-164

4.3.4.2 Impacts of an Accidental Fuel Spill .......................................................4-165

4.3.4.3 Cumulative Impacts...............................................................................4-165

4.3.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-166

4.3.5.1 Impacts of Routine Activities .................................................................4-166

4.3.5.2 Impacts of an Accidental Fuel Spill .......................................................4-166

4.3.5.3 Cumulative Impacts...............................................................................4-166

4.3.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-167

4.3.6.1 Impacts of Routine Activities .................................................................4-167

4.3.6.1.1 Reduced Level of Activity ...................................................4-167

4.3.6.2 Impacts of an Accidental Fuel Spill .......................................................4-167

4.3.6.3 Cumulative Impacts...............................................................................4-168

4.3.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-168

4.3.7.1 Impacts of Routine Activities .................................................................4-168

4.3.7.1.1 Closure Areas.....................................................................4-168

4.3.7.2 Impacts of an Accidental Fuel Spill .......................................................4-169

4.3.7.3 Cumulative Impacts...............................................................................4-169

4.3.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-169

4.3.8.1 Impacts of Routine Activities .................................................................4-169

4.3.8.1.1 Active Acoustic Sound Sources .........................................4-169

4.3.8.1.2 Vessel and Equipment Noise .............................................4-170

4.3.8.1.3 Vessel Traffic......................................................................4-170

4.3.8.1.4 Aircraft Traffic and Noise....................................................4-170

4.3.8.1.5 Trash and Debris ................................................................4-170

4.3.8.1.6 Routine Activities Impact Conclusions ...............................4-170

4.3.8.2 Impacts of Accidental Events ................................................................4-171

4.3.8.3 Cumulative Impacts...............................................................................4-171

4.4 Fish Resources and Essential Fish Habitat .....................................................................4-171

4.4.1 Description of the Affected Environment .............................................................4-171

4.4.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-174

4.4.2.1 Impacts of Routine Activities .................................................................4-175

4.4.2.1.1 Background: Potential Effects of Noise on Fishes............4-175

4.4.2.1.2 Analysis of Active Acoustic Sound Sources.......................4-178

4.4.2.1.3 Vessel and Equipment Noise .............................................4-181

4.4.2.1.4 Trash and Debris ................................................................4-182

4.4.2.1.5 Seafloor Disturbance..........................................................4-183

4.4.2.1.6 Drilling Discharges..............................................................4-184

4.4.2.1.7 Entanglement......................................................................4-184

4.4.2.1.8 Routine Activities Impact Conclusions ...............................4-184

4.4.2.2 Impacts of an Accidental Fuel Spill .......................................................4-185
Gulf of Mexico G&G Activities Programmatic EIS lv

4.4.2.3 Cumulative Impacts...............................................................................4-186

4.4.2.3.1 Noise...................................................................................4-186

4.4.2.3.2 Trash and Debris ................................................................4-188

4.4.2.3.3 Seafloor Disturbances ........................................................4-189

4.4.2.3.4 Drilling Discharges..............................................................4-189

4.4.2.3.5 Entanglement......................................................................4-190

4.4.2.3.6 Cumulative Impact Conclusions .........................................4-191

4.4.2.3.7 Accidental Fuel Spills .........................................................4-191

4.4.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-192

4.4.3.1 Impacts of Routine Activities .................................................................4-193

4.4.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to 

April 30)...............................................................................4-193

4.4.3.1.2 Minimum Separation Distances..........................................4-193

4.4.3.1.3 Seismic Restrictions in the Areas of Concern within the 

EPA.....................................................................................4-194

4.4.3.1.4 Routine Activities Impact Conclusions ...............................4-194

4.4.3.2 Impacts of an Accidental Fuel Spill .......................................................4-195

4.4.3.3 Cumulative Impacts...............................................................................4-195

4.4.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-196

4.4.4.1 Impacts of Routine Activities .................................................................4-196

4.4.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to 

May 31)...............................................................................4-196

4.4.4.1.2 Routine Activities Impact Conclusions ...............................4-197

4.4.4.2 Impacts of an Accidental Fuel Spill .......................................................4-197

4.4.4.3 Cumulative Impacts...............................................................................4-197

4.4.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-198

4.4.5.1 Impacts of Routine Activities .................................................................4-198

4.4.5.2 Impacts of an Accidental Fuel Spill .......................................................4-198

4.4.5.3 Cumulative Impacts...............................................................................4-198

4.4.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-199

4.4.6.1 Impacts of Routine Activities .................................................................4-199

4.4.6.1.1 Reduced Level of Activity ...................................................4-199

4.4.6.2 Impacts of an Accidental Fuel Spill .......................................................4-200

4.4.6.3 Cumulative Impacts...............................................................................4-200

4.4.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-200

4.4.7.1 Impacts of Routine Activities .................................................................4-200

4.4.7.1.1 Closure Areas.....................................................................4-200

4.4.7.2 Impacts of an Accidental Fuel Spill .......................................................4-201

4.4.7.3 Cumulative Impacts...............................................................................4-201

4.4.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-202

4.4.8.1 Impacts of Routine Activities .................................................................4-202

4.4.8.2 Impacts of Accidental Fuel Spills ..........................................................4-202

4.4.8.3 Cumulative Impacts...............................................................................4-203

4.5 Benthic Communities .......................................................................................................4-203

4.5.1 Description of the Affected Environment .............................................................4-203

4.5.1.1 Soft Bottom Communities......................................................................4-204

4.5.1.2 Hard Bottom Communities ....................................................................4-204

4.5.1.2.1 Deepwater Coral Communities ..........................................4-205

4.5.1.2.2 Live Bottoms (Pinnacle Trend)...........................................4-205

4.5.1.2.3 Live Bottoms (Low Relief)...................................................4-206

4.5.1.2.4 Topographic Features ........................................................4-206

4.5.1.2.5 Artificial Reefs.....................................................................4-206
lvi Table of Contents

4.5.1.3 Chemosynthetic Communities ..............................................................4-207

4.5.1.4 Listed, Candidate, and Species of Concern..........................................4-208

4.5.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-208

4.5.2.1 Impacts of Routine Activities .................................................................4-209

4.5.2.1.1 Active Acoustic Sound Sources .........................................4-209

4.5.2.1.2 Trash and Debris ................................................................4-211

4.5.2.1.3 Seafloor Disturbance..........................................................4-212

4.5.2.1.4 Drilling Discharges..............................................................4-214

4.5.2.1.5 Routine Activities Impact Conclusions ...............................4-215

4.5.2.2 Impacts of an Accidental Fuel Spill .......................................................4-215

4.5.2.3 Cumulative Impacts...............................................................................4-216

4.5.2.3.1 Active Acoustic Sound Sources .........................................4-216

4.5.2.3.2 Trash and Debris ................................................................4-217

4.5.2.4 Seafloor Disturbances...........................................................................4-217

4.5.2.4.1 Drilling Discharges..............................................................4-218

4.5.2.4.2 Cumulative Impact Conclusions .........................................4-218

4.5.2.4.3 Accidental Fuel Spills .........................................................4-219

4.5.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-219

4.5.3.1 Impacts of Routine Activities .................................................................4-219

4.5.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to 

April 30)...............................................................................4-219

4.5.3.1.2 Seismic Restrictions in the Areas of Concern within the 

EPA.....................................................................................4-220

4.5.3.1.3 Routine Activities Impact Conclusions ...............................4-220

4.5.3.2 Impacts of an Accidental Fuel Spill .......................................................4-220

4.5.3.3 Cumulative Impacts...............................................................................4-220

4.5.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-221

4.5.4.1 Impacts of Routine Activities .................................................................4-221

4.5.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to 

May 31)...............................................................................4-221

4.5.4.1.2 Routine Activities Impact Conclusions ...............................4-221

4.5.4.2 Impacts of an Accidental Fuel Spill .......................................................4-221

4.5.4.3 Cumulative Impacts...............................................................................4-221

4.5.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-222

4.5.5.1 Impacts of Routine Activities .................................................................4-222

4.5.5.2 Impacts of an Accidental Fuel Spill .......................................................4-222

4.5.5.3 Cumulative Impacts...............................................................................4-223

4.5.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-223

4.5.6.1 Impacts of Routine Activities .................................................................4-223

4.5.6.1.1 Reduced Level of Activity ...................................................4-223

4.5.6.1.2 Routine Activities Impact Conclusions ...............................4-223

4.5.6.2 Impacts of an Accidental Fuel Spill .......................................................4-223

4.5.6.3 Cumulative Impacts...............................................................................4-224

4.5.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-224

4.5.7.1 Impacts of Routine Activities .................................................................4-224

4.5.7.1.1 Closure Areas.....................................................................4-224

4.5.7.1.2 Routine Activities Impact Conclusions ...............................4-224

4.5.7.2 Impacts of an Accidental Fuel Spill .......................................................4-224

4.5.7.3 Cumulative Impacts...............................................................................4-225
Gulf of Mexico G&G Activities Programmatic EIS lvii

4.5.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-225

4.5.8.1 Impacts of Routine Activities .................................................................4-225

4.5.8.2 Impacts of Accidental Fuel Spill ............................................................4-225

4.5.8.3 Cumulative Impacts...............................................................................4-226

4.6 Marine and Coastal Birds.................................................................................................4-226

4.6.1 Description of the Affected Environment .............................................................4-226

4.6.1.1 Unlisted Species....................................................................................4-226

4.6.1.2 Listed Species .......................................................................................4-228

4.6.1.3 Baseline Populations and the Deepwater Horizon Explosion, Oil Spill, 

and Response .......................................................................................4-228

4.6.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-230

4.6.2.1 Impacts of Routine Activities .................................................................4-231

4.6.2.1.1 Active Acoustic Sound Sources .........................................4-231

4.6.2.1.2 Vessel and Equipment Noise and Vessel Traffic ...............4-234

4.6.2.1.3 Aircraft Traffic and Noise....................................................4-239

4.6.2.1.4 Trash and Debris ................................................................4-240

4.6.2.1.5 Routine Activities Impact Conclusions ...............................4-241

4.6.2.2 Impacts of an Accidental Fuel Spill .......................................................4-241

4.6.2.3 Cumulative Impacts...............................................................................4-242

4.6.2.3.1 Noise...................................................................................4-243

4.6.2.3.2 Vessel and Aircraft Traffic ..................................................4-245

4.6.2.3.3 Trash and Debris ................................................................4-247

4.6.2.3.4 Cumulative Impact Conclusions .........................................4-247

4.6.2.3.5 Accidental Fuel Spills .........................................................4-248

4.6.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-248

4.6.3.1 Impacts of Routine Activities .................................................................4-248

4.6.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to 

April 30)...............................................................................4-249

4.6.3.1.2 Minimum Separation Distances..........................................4-249

4.6.3.1.3 Seismic Restrictions in the Areas of Concern within the 

EPA.....................................................................................4-250

4.6.3.1.4 Routine Activities Impact Conclusions ...............................4-251

4.6.3.2 Impacts of an Accidental Fuel Spill .......................................................4-251

4.6.3.3 Cumulative Impacts...............................................................................4-252

4.6.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-252

4.6.4.1 Impacts of Routine Activities .................................................................4-252

4.6.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to 

May 31)...............................................................................4-252

4.6.4.1.2 Routine Activities Impact Conclusions ...............................4-253

4.6.4.2 Impacts of an Accidental Fuel Spill .......................................................4-254

4.6.4.3 Cumulative Impacts...............................................................................4-254

4.6.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns) .........4-255

4.6.5.1 Impacts of Routine Activities .................................................................4-255

4.6.5.2 Impacts of an Accidental Fuel Spill .......................................................4-255

4.6.5.3 Cumulative Impacts...............................................................................4-256

4.6.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-256

4.6.6.1 Impacts of Routine Activities .................................................................4-256

4.6.6.1.1 Reduced Level of Activity ...................................................4-256

4.6.6.1.2 Routine Activities Impact Conclusions ...............................4-258

4.6.6.2 Impacts of an Accidental Fuel Spill .......................................................4-258

4.6.6.3 Cumulative Impacts...............................................................................4-258
lviii Table of Contents

4.6.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-258

4.6.7.1 Impacts of Routine Activities .................................................................4-259

4.6.7.2 Impacts of an Accidental Fuel Spill .......................................................4-259

4.6.7.3 Cumulative Impacts...............................................................................4-259

4.6.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-260

4.6.8.1 Impacts of Routine Activities .................................................................4-260

4.6.8.2 Impacts of Accidental Fuel Spill ............................................................4-260

4.6.8.3 Cumulative Impacts...............................................................................4-261

4.7 Marine Protected Areas....................................................................................................4-261

4.7.1 Description of the Affected Environment .............................................................4-261

4.7.1.1 Offshore Marine Protected Areas..........................................................4-262

4.7.1.2 Coastal Marine Protected Areas ...........................................................4-264

4.7.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-267

4.7.2.1 Impacts of Routine Activities .................................................................4-268

4.7.2.1.1 Active Acoustic Sound Sources .........................................4-268

4.7.2.1.2 Trash and Debris ................................................................4-273

4.7.2.1.3 Seafloor Disturbance..........................................................4-273

4.7.2.1.4 Drilling Discharges..............................................................4-274

4.7.2.1.5 Routine Activities Impact Conclusions ...............................4-275

4.7.2.2 Accidental Fuel Spills ............................................................................4-276

4.7.2.3 Cumulative Impacts...............................................................................4-277

4.7.2.3.1 Noise...................................................................................4-277

4.7.2.3.2 Trash and Debris ................................................................4-277

4.7.2.3.3 Seafloor Disturbances ........................................................4-278

4.7.2.3.4 Drilling Discharges..............................................................4-278

4.7.2.3.5 Cumulative Impact Conclusions .........................................4-279

4.7.2.3.6 Accidental Fuel Spills .........................................................4-279

4.7.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-279

4.7.3.1 Impacts of Routine Activities .................................................................4-279

4.7.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to 

April 30)...............................................................................4-280

4.7.3.1.2 Expanded PSO Program....................................................4-280

4.7.3.1.3 Minimum Separation Distances..........................................4-280

4.7.3.1.4 Seismic Restrictions in the Areas of Concern within the 

EPA.....................................................................................4-280

4.7.3.1.5 Use of PAM Required.........................................................4-280

4.7.3.1.6 Routine Activities Impact Conclusions ...............................4-280

4.7.3.2 Accidental Fuel Spills ............................................................................4-281

4.7.3.3 Cumulative Impacts...............................................................................4-281

4.7.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-282

4.7.4.1 Impacts of Routine Activities .................................................................4-282

4.7.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to 

May 31)...............................................................................4-282

4.7.4.1.2 Expanded PSO Program....................................................4-282

4.7.4.1.3 Use of PAM Required.........................................................4-282

4.7.4.1.4 Non-Airgun HRG Survey Protocol......................................4-283

4.7.4.1.5 Routine Activities Impact Conclusions ...............................4-283

4.7.4.2 Accidental Fuel Spills ............................................................................4-283

4.7.4.3 Cumulative Impacts...............................................................................4-283
Gulf of Mexico G&G Activities Programmatic EIS lix

4.7.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-284

4.7.5.1 Impacts of Routine Activities .................................................................4-284

4.7.5.2 Accidental Fuel Spills ............................................................................4-284

4.7.5.3 Cumulative Impacts...............................................................................4-285

4.7.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-285

4.7.6.1 Impacts of Routine Activities .................................................................4-285

4.7.6.2 Accidental Fuel Spills ............................................................................4-286

4.7.6.3 Cumulative Impacts...............................................................................4-286

4.7.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-287

4.7.7.1 Impacts of Routine Activities .................................................................4-287

4.7.7.2 Accidental Fuel Spills ............................................................................4-287

4.7.7.3 Cumulative Impacts...............................................................................4-288

4.7.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-288

4.7.8.1 Impacts of Routine Activities .................................................................4-288

4.7.8.2 Impacts of Accidental Fuel Spill ............................................................4-289

4.7.8.3 Cumulative Impacts...............................................................................4-289

4.8 Sargassum and Associated Communities .......................................................................4-289

4.8.1 Description of the Affected Environment .............................................................4-289

4.8.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-291

4.8.2.1 Impacts of Routine Activities .................................................................4-292

4.8.2.1.1 Vessel Traffic......................................................................4-292

4.8.2.1.2 Vessel Discharges..............................................................4-293

4.8.2.1.3 Trash and Debris ................................................................4-293

4.8.2.1.4 Routine Activities Impact Conclusions ...............................4-294

4.8.2.2 Impacts of an Accidental Fuel Spill .......................................................4-295

4.8.2.3 Cumulative Impacts...............................................................................4-296

4.8.2.3.1 Vessel Traffic......................................................................4-296

4.8.2.3.2 Vessel Discharges..............................................................4-297

4.8.2.3.3 Trash and Debris ................................................................4-297

4.8.2.3.4 Cumulative Impact Conclusions .........................................4-298

4.8.2.3.5 Accidental Fuel Spills .........................................................4-298

4.8.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-298

4.8.3.1 Impacts of Routine Activities .................................................................4-299

4.8.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to 

April 30)...............................................................................4-299

4.8.3.1.2 Seismic Restrictions in the Areas of Concern within the 

EPA.....................................................................................4-299

4.8.3.1.3 Routine Activities Impact Conclusions ...............................4-300

4.8.3.2 Impacts of an Accidental Fuel Spill .......................................................4-300

4.8.3.3 Cumulative Impacts...............................................................................4-300

4.8.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-301

4.8.4.1 Impacts of Routine Activities .................................................................4-301

4.8.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to 

May 31)...............................................................................4-301

4.8.4.1.2 Routine Activities Impact Conclusions ...............................4-301

4.8.4.2 Impacts of an Accidental Fuel Spill .......................................................4-302

4.8.4.3 Cumulative Impacts...............................................................................4-302

4.8.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-302

4.8.5.1 Impacts of Routine Activities .................................................................4-303

4.8.5.2 Impacts of an Accidental Fuel Spill .......................................................4-303

4.8.5.3 Cumulative Impacts...............................................................................4-303
lx Table of Contents

4.8.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-304

4.8.6.1 Impacts of Routine Activities .................................................................4-304

4.8.6.2 Impacts of an Accidental Fuel Spill .......................................................4-304

4.8.6.3 Cumulative Impacts...............................................................................4-304

4.8.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-305

4.8.7.1 Impacts of Routine Activities .................................................................4-305

4.8.7.2 Impacts of an Accidental Fuel Spill .......................................................4-305

4.8.7.3 Cumulative Impacts...............................................................................4-305

4.8.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-306

4.8.8.1 Impacts of Routine Activities .................................................................4-306

4.8.8.2 Impacts of Accidental Fuel Spill ............................................................4-306

4.8.8.3 Cumulative Impacts...............................................................................4-306

4.9 Commercial Fisheries.......................................................................................................4-306

4.9.1 Description of the Affected Environment .............................................................4-306

4.9.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-308

4.9.2.1 Impacts of Routine Activities .................................................................4-309

4.9.2.1.1 Routine Activities Impact Conclusions ...............................4-314

4.9.2.2 Impacts of an Accidental Fuel Spill .......................................................4-314

4.9.2.3 Cumulative Impacts...............................................................................4-315

4.9.2.3.1 Active Acoustic Sound Sources .........................................4-315

4.9.2.3.2 Vessel Traffic......................................................................4-316

4.9.2.3.3 Stand-Off Distance .............................................................4-317

4.9.2.3.4 Seafloor Disturbance..........................................................4-317

4.9.2.3.5 Entanglement......................................................................4-318

4.9.2.3.6 Cumulative Impact Conclusions .........................................4-319

4.9.2.4 Accidental Fuel Spills ............................................................................4-319

4.9.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-320

4.9.3.1 Impacts of Routine Activities .................................................................4-320

4.9.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to 

April 30)...............................................................................4-321

4.9.3.1.2 Minimum Separation Distances..........................................4-321

4.9.3.1.3 Seismic Restrictions in the Areas of Concern within the 

EPA.....................................................................................4-322

4.9.3.1.4 Routine Activities Impact Conclusions ...............................4-322

4.9.3.2 Impacts of an Accidental Fuel Spill .......................................................4-323

4.9.3.3 Cumulative Impacts...............................................................................4-323

4.9.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-323

4.9.4.1 Impacts of Routine Activities .................................................................4-323

4.9.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to 

May 31)...............................................................................4-324

4.9.4.1.2 Routine Activities Impact Conclusions ...............................4-324

4.9.4.2 Impacts of an Accidental Fuel Spill .......................................................4-324

4.9.4.3 Cumulative Impacts...............................................................................4-325

4.9.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-325

4.9.5.1 Impacts of Routine Activities .................................................................4-325

4.9.5.2 Impacts of an Accidental Fuel Spill .......................................................4-325

4.9.5.3 Cumulative Impacts...............................................................................4-326

4.9.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-326

4.9.6.1 Impacts of Routine Activities .................................................................4-326

4.9.6.2 Impacts of an Accidental Fuel Spill .......................................................4-327

4.9.6.3 Cumulative Impacts...............................................................................4-328
Gulf of Mexico G&G Activities Programmatic EIS lxi

4.9.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-328

4.9.7.1 Impacts of Routine Activities .................................................................4-328

4.9.7.1.1 Closure Areas.....................................................................4-328

4.9.7.1.2 Routine Activities Impact Conclusions ...............................4-329

4.9.7.2 Impacts of an Accidental Fuel Spill .......................................................4-329

4.9.7.3 Cumulative Impacts...............................................................................4-329

4.9.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-330

4.9.8.1 Impacts of Routine Activities .................................................................4-330

4.9.8.2 Impacts of Accidental Fuel Spills ..........................................................4-330

4.9.8.3 Cumulative Impacts...............................................................................4-330

4.10 Recreational Fisheries......................................................................................................4-331

4.10.1 Description of the Affected Environment .............................................................4-331

4.10.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-333

4.10.2.1 Impacts of Routine Activities .................................................................4-334

4.10.2.1.1 Routine Activities Impact Conclusions ...............................4-337

4.10.2.2 Impacts of an Accidental Fuel Spill .......................................................4-337

4.10.2.3 Cumulative Impacts...............................................................................4-337

4.10.2.3.1 Active Acoustic Sound Sources .........................................4-337

4.10.2.3.2 Vessel Traffic......................................................................4-338

4.10.2.3.3 Stand-off Distance ..............................................................4-339

4.10.2.3.4 Cumulative Impact Conclusions .........................................4-340

4.10.2.3.5 Accidental Fuel Spills .........................................................4-340

4.10.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-342

4.10.3.1 Impacts of Routine Activities .................................................................4-342

4.10.3.1.1 Seasonal Restriction for Federal Coastal Waters 

(January 1 to April 30) ........................................................4-342

4.10.3.1.2 Minimum Separation Distances..........................................4-342

4.10.3.1.3 Seismic Restrictions in the EPA.........................................4-343

4.10.3.1.4 Routine Activities Impact Conclusions ...............................4-344

4.10.3.2 Impacts of an Accidental Fuel Spill .......................................................4-344

4.10.3.3 Cumulative Impacts...............................................................................4-344

4.10.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-345

4.10.4.1 Impacts of Routine Activities .................................................................4-345

4.10.4.1.1 Seasonal Restriction for all Coastal Waters (February 1 to 

May 31)...............................................................................4-345

4.10.4.1.2 Routine Activities Impact Conclusions ...............................4-346

4.10.4.2 Impacts of an Accidental Fuel Spill .......................................................4-346

4.10.4.3 Cumulative Impacts...............................................................................4-346

4.10.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-346

4.10.5.1 Impacts of Routine Activities .................................................................4-347

4.10.5.2 Impacts of an Accidental Fuel Spill .......................................................4-347

4.10.5.3 Cumulative Impacts...............................................................................4-347

4.10.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-347

4.10.6.1 Impacts of Routine Activities .................................................................4-347

4.10.6.1.1 Reduction of G&G Activity Levels ......................................4-348

4.10.6.2 Impacts of an Accidental Fuel Spill .......................................................4-348

4.10.6.3 Cumulative Impacts...............................................................................4-348

4.10.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-349

4.10.7.1 Impacts of Routine Activities .................................................................4-349

4.10.7.1.1 Area Closures.....................................................................4-349

4.10.7.1.2 Routine Activities Impact Conclusions ...............................4-349
lxii Table of Contents

4.10.7.2 Impacts of an Accidental Fuel Spill .......................................................4-349

4.10.7.3 Cumulative Impacts...............................................................................4-350

4.10.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-350

4.10.8.1 Impacts of Routine Activities .................................................................4-350

4.10.8.2 Impacts of Accidental Fuel Spills ..........................................................4-350

4.10.8.3 Cumulative Impacts...............................................................................4-351

4.11 Archaeological Resources................................................................................................4-351

4.11.1 Description of the Affected Environment .............................................................4-351

4.11.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-352

4.11.2.1 Impacts of Routine Activities .................................................................4-354

4.11.2.1.1 Seafloor Disturbance and Entanglement ...........................4-354

4.11.2.1.2 Drilling Discharges..............................................................4-355

4.11.2.1.3 Routine Activities Impact Conclusions ...............................4-356

4.11.2.2 Impacts of an Accidental Fuel Spill .......................................................4-356

4.11.2.3 Cumulative Impacts...............................................................................4-357

4.11.2.3.1 Seafloor Disturbance and Entanglement ...........................4-357

4.11.2.3.2 Drilling Discharges..............................................................4-358

4.11.2.3.3 Accidental Fuel Spills .........................................................4-359

4.11.2.3.4 Cumulative Impact Conclusions .........................................4-359

4.11.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-359

4.11.3.1 Impacts of Routine Activities .................................................................4-359

4.11.3.2 Impacts of an Accidental Fuel Spill .......................................................4-360

4.11.3.3 Cumulative Impacts...............................................................................4-360

4.11.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-361

4.11.4.1 Impacts of Routine Activities .................................................................4-361

4.11.4.2 Impacts of an Accidental Fuel Spill .......................................................4-361

4.11.4.3 Cumulative Impacts...............................................................................4-361

4.11.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-362

4.11.5.1 Impacts of Routine Activities .................................................................4-362

4.11.5.2 Impacts of an Accidental Fuel Spill .......................................................4-363

4.11.5.3 Cumulative Impacts...............................................................................4-363

4.11.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-363

4.11.6.1 Impacts of Routine Activities .................................................................4-363

4.11.6.2 Impacts of an Accidental Fuel Spill .......................................................4-364

4.11.6.3 Cumulative Impacts...............................................................................4-364

4.11.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-365

4.11.7.1 Impacts of Routine Activities .................................................................4-365

4.11.7.2 Impacts of an Accidental Fuel Spill .......................................................4-365

4.11.7.3 Cumulative Impacts...............................................................................4-365

4.11.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-366

4.11.8.1 Impacts of Routine Activities .................................................................4-366

4.11.8.2 Impacts of Accidental Fuel Spill ............................................................4-366

4.11.8.3 Cumulative Impacts...............................................................................4-367

4.12 Other Marine Uses ...........................................................................................................4-367

4.12.1 Description of the Affected Environment .............................................................4-367

4.12.1.1 Shipping and Marine Transportation.....................................................4-368

4.12.1.2 Military Warning Areas and Other Military Uses ...................................4-368

4.12.1.3 Sand and Gravel Mining........................................................................4-368

4.12.1.4 Renewable Energy Development – Wind Energy.................................4-369

4.12.1.5 Ocean Dredged Material Disposal Sites...............................................4-369

4.12.1.6 Oil and Gas Exploration, Development, and Production ......................4-369
Gulf of Mexico G&G Activities Programmatic EIS lxiii

4.12.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-370

4.12.2.1 Impacts of Routine Activities .................................................................4-371

4.12.2.1.1 Vessel Traffic and Stand-Off Distance ...............................4-371

4.12.2.1.2 Shipping and Marine Transportation Vessel Traffic...........4-372

4.12.2.1.3 Military Warning Areas and Other Military Uses ................4-372

4.12.2.1.4 Sand and Gravel Mining.....................................................4-372

4.12.2.1.5 Renewable Energy Development.......................................4-373

4.12.2.1.6 Ocean Dredged Material Disposal Sites ............................4-373

4.12.2.1.7 Oil and Gas Exploration, Development, and Production....4-373

4.12.2.1.8 Pipeline and Cable Infrastructure.......................................4-373

4.12.2.1.9 Routine Activities Impact Conclusions ...............................4-374

4.12.2.2 Impacts of an Accidental Fuel Spill .......................................................4-374

4.12.2.3 Cumulative Impacts...............................................................................4-374

4.12.2.3.1 Vessel Traffic and Stand-Off Distances .............................4-375

4.12.2.3.2 Aircraft Traffic and Noise....................................................4-376

4.12.2.3.3 Seafloor Disturbances ........................................................4-376

4.12.2.3.4 Cumulative Impact Conclusions .........................................4-376

4.12.2.3.5 Accidental Fuel Spills .........................................................4-377

4.12.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-377

4.12.3.1 Impacts of Routine Activities .................................................................4-377

4.12.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to 

April 30)...............................................................................4-378

4.12.3.1.2 Minimum Separation Distances..........................................4-378

4.12.3.1.3 Routine Activities Impact Conclusions ...............................4-378

4.12.3.2 Impacts of an Accidental Fuel Spill .......................................................4-378

4.12.3.3 Cumulative Impacts...............................................................................4-379

4.12.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-379

4.12.4.1 Impacts of Routine Activities .................................................................4-379

4.12.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to 

May 31)...............................................................................4-380

4.12.4.1.2 Routine Activities Impact Conclusions ...............................4-380

4.12.4.2 Impacts of an Accidental Fuel Spill .......................................................4-380

4.12.4.3 Cumulative Impacts...............................................................................4-380

4.12.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-381

4.12.5.1 Impacts of Routine Activities .................................................................4-381

4.12.5.2 Impacts of an Accidental Fuel Spill .......................................................4-381

4.12.5.3 Cumulative Impacts...............................................................................4-381

4.12.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-381

4.12.6.1 Impacts of Routine Activities .................................................................4-381

4.12.6.2 Impacts of an Accidental Fuel Spill .......................................................4-382

4.12.6.3 Cumulative Impacts...............................................................................4-382

4.12.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-382

4.12.7.1 Impacts of Routine Activities .................................................................4-383

4.12.7.2 Impacts of an Accidental Fuel Spill .......................................................4-383

4.12.7.3 Cumulative Impacts...............................................................................4-383

4.12.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-384

4.12.8.1 Impacts of Routine Activities .................................................................4-384

4.12.8.2 Impacts of Accidental Events ................................................................4-384

4.12.8.3 Cumulative Impacts...............................................................................4-384
lxiv Table of Contents

4.13 Human Resources and Land Use....................................................................................4-384

4.13.1 Description of the Affected Environment .............................................................4-384

4.13.1.1 Land Use and Coastal Infrastructure ....................................................4-385

4.13.1.2 Environmental Justice ...........................................................................4-386

4.13.1.3 Demographics .......................................................................................4-387

4.13.1.4 Socioeconomics ....................................................................................4-388

4.13.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)......................4-389

4.13.3 Impacts – Alternative B (Settlement Agreement Alternative)..............................4-389

4.13.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)............................................................................................4-389

4.13.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns).........4-390

4.13.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)....................4-390

4.13.7 Impacts – Alternative F (Alternative C Plus Area Closures)................................4-392

4.13.8 Impacts – Alternative G (No New Activity Alternative) ........................................4-392

4.13.9 Economic Factors ................................................................................................4-394

4.13.9.1 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative) .......4-396

4.13.9.2 Impacts – Alternative B (Settlement Agreement Alternative) ...............4-397

4.13.9.3 Impacts – Alternative C (Proposed Action – Alternative A Plus 

Additional Mitigation Measures)............................................................4-398

4.13.9.4 Impacts – Alternative D (Alternative C Plus Marine Mammal 

Shutdowns)............................................................................................4-398

4.13.9.5 Impacts – Alternative E (Alternative C at Reduced Activity Levels) .....4-399

4.13.9.6 Impacts – Alternative F (Alternative C Plus Area Closures).................4-401

4.13.9.7 Impacts – Alternative G (No New Activity Alternative)..........................4-403

4.14 NMFS’ Analysis of Chronic Effects in the Gulf of Mexico in Support of the MMPA 

Petition for Incidental Take Regulations ..........................................................................4-405

5 OTHER NEPA CONSIDERATIONS............................................................................................... 5-3

5.1 Unavoidable Adverse Impacts of the Proposed Action........................................................ 5-3

5.2 Irreversible and Irretrievable Commitment of Resources .................................................... 5-4

5.3 Relationship Between Short-Term Uses of the Environment and the Maintenance 

and Enhancement of Long-Term Productivity ..................................................................... 5-5

6 PUBLIC INVOLVEMENT AND AGENCY CONSULTATION AND COORDINATION ................... 6-3

6.1 Development of the Proposed Action................................................................................... 6-3

6.2 Notice of Intent ..................................................................................................................... 6-3

6.3 Scoping and Development of the Draft Programmatic EIS.................................................. 6-3

6.3.1 Scoping Meetings .................................................................................................... 6-4 

6.3.2 Comments Received During Scoping...................................................................... 6-4 

6.3.3 Cooperating Agencies.............................................................................................. 6-5 

6.3.3.1 Bureau of Safety and Environmental Enforcement................................... 6-6

6.3.3.2 National Oceanic and Atmospheric Administration................................... 6-7

6.4 Distribution of the Draft Programmatic EIS.......................................................................... 6-8

6.5 Public Meetings .................................................................................................................. 6-12

6.6 Regulatory Framework ....................................................................................................... 6-12

6.6.1 Federal Agencies and Regulations........................................................................ 6-12

6.6.2 State Agencies and Regulations............................................................................ 6-13

6.7 Consultation with the National Marine Fisheries Service .................................................. 6-13

7 LITERATURE CITED...................................................................................................................... 7-3
Gulf of Mexico G&G Activities Programmatic EIS lxv

8 PREPARERS AND REVIEWERS .................................................................................................. 8-3

8.1 BOEM, BSEE, and NMFS Preparers................................................................................... 8-3

8.2 BOEM and NMFS Reviewers............................................................................................... 8-3

8.3 Contractor Preparers............................................................................................................ 8-4

 
lxvi Table of Contents

Volume II 

Page

LIST OF FIGURES.............................................................................................................................. xxi

LIST OF TABLES............................................................................................................................... xxiii

FIGURES ................................................................................................................................. Figures-3 

TABLES......................................................................................................................................Tables-3 

APPENDIX A AGREEMENTS AND COOPERATING AGENCY LETTERS................................... A-1 

APPENDIX B PROTECTIVE MEASURES AND MITIGATION AND REGULATORY 

REQUIREMENTS..................................................................................................... B-1 

APPENDIX C SETTLEMENT AGREEMENT AND STIPULATION TO AMEND SETTLEMENT 

AGREEMENT ........................................................................................................... C-1 

APPENDIX D ACOUSTIC PROPAGATION AND EXPOSURE MODELING ................................. D-1 

Volume III

Page

LIST OF FIGURES.............................................................................................................................. xxi

LIST OF TABLES............................................................................................................................... xxiii

APPENDIX E EXPANDED AFFECTED ENVIRONMENT INFORMATION .................................... E-1 

APPENDIX F G&G SURVEY DESCRIPTIONS.............................................................................. F-1 

APPENDIX G SCREENING OUT TEAM REPORT......................................................................... G-1 

APPENDIX H MARINE MAMMAL HEARING AND SENSITIVITY TO ACOUSTIC IMPACTS....... H-1 

APPENDIX I SEA TURTLE HEARING AND SENSITIVITY TO ACOUSTIC IMPACTS ................. I-1 

APPENDIX J FISH HEARING AND THE SENSITIVITY OF FISH TO HEARING LOSS AND 

INJURY FROM EXPOSURE TO ANTHROPOGENIC SOUND................................ J-1 

APPENDIX K CUMULATIVE AND CHRONIC EFFECTS IN THE GULF OF MEXICO ................. K-1 

APPENDIX L PANEL REPORTS..................................................................................................... L-1 
Gulf of Mexico G&G Activities Programmatic EIS lxvii

LIST OF FIGURES

Page

Figure ES-1. Area of Interest for the Proposed Action. .................................................................. ix

Figure 1.1-1. Area of Interest for the Proposed Action. ..................................................... Figures-3

Figure 2.2-1. Alternative B Seasonal Restrictions for Coastal Waters Between 

January 1 and April 30 and Areas of Concern as Defined in the 

Settlement Agreement. ................................................................................. Figures-4

Figure 2.3-1. Alternatives C through F Seasonal Restrictions for Coastal Waters 

Between February 1 and May 31 and Areas Requiring PAM for All 

Seismic Airgun Surveys................................................................................ Figures-5

Figure 2.6-1. Alternative F Closure Areas (the CPA Closure Area; the EPA Closure 

Area; the Dry Tortugas Closure Area; and the Flower Gardens Closure 

Area) and Seasonal Restrictions for Coastal Waters Between February 1 

and May 31 and Areas Requiring PAM for All Seismic Airgun Surveys. ..... Figures-6

Figure 3.4-1. Cumulative Activities Occurring in the AOI................................................... Figures-7

Figure 4.1-1. Locations of Selected Northern Gulf of Mexico Cetacean Stocks in 

Relation to the Cumulative Surface Oiling Footprint of the Deepwater 

Horizon Oil Spill............................................................................................. Figures-8

Figure 4.2-1. Distribution of Sperm Whale Sightings from Vessel Surveys....................... Figures-9

Figure 4.2-2. Manatee Sightings in the AOI..................................................................... Figures-10

Figure 4.2-3. Distribution of Bryde’s Whale Sightings from Vessel Surveys ................... Figures-11

Figure 4.2-4. Bays and Sounds of the Northern GOM..................................................... Figures-12

Figure 4.3-1. Sea Turtle Nesting Locations Reported for Individual Counties Adjacent 

to the AOI from 1992 to 2014 ..................................................................... Figures-13

Figure 4.3-2. Location of the Four Recovery Units for the Loggerhead Turtle 

in the U.S. ................................................................................................... Figures-14

Figure 4.3-3. Designated Critical Habitat for Hatchling Loggerhead Turtles, Including 

Sargassum Habitat. .................................................................................... Figures-15

Figure 4.3-4. Frequency Range of Hearing in Sea Turtles and Typical Frequency 

Output from Seismic Airguns ...................................................................... Figures-16

Figure 4.4-1. Smalltooth Sawfish and Gulf Sturgeon Critical Habitat in the AOI............. Figures-17

Figure 4.5-1. Distribution of Known Hard/Live Bottom and Chemosynthetic 

Communities Locations in the AOI for Which NTLs Apply......................... Figures-18

Figure 4.5-2. Topographic Features Located in the AOI.................................................. Figures-19

Figure 4.5-3. Location of Artificial Reefs (deliberately placed objects/structures 

of human origin) in the AOI......................................................................... Figures-20

Figure 4.6-1. Mississippi Flyway Migratory Routes.......................................................... Figures-21

Figure 4.6-2. Bird Conservation Regions ......................................................................... Figures-22

Figure 4.6-3. U.S. Important Bird Areas........................................................................... Figures-23

Figure 4.6-4. IBAs of Louisiana that Include Nearshore Waters Within the AOI............. Figures-24

Figure 4.7-1. National System Offshore Marine Protected Areas Within the AOI........... Figures-25

Figure 4.7-2. National System Coastal Marine Protected Areas Within the AOI............. Figures-26

Figure 4.9-1. Locations of Selected Seasonal and/or Area Closures to Commercial 

Fishing in the AOI. ...................................................................................... Figures-27

Figure 4.12-1. Aids to Navigation, Shipping Lanes, Precaution Areas, Fairways, and 

Traffic Separation Schemes in the AOI. ..................................................... Figures-28

Figure 4.12-2. Military Use and Ordnance Disposal Areas in the AOI............................... Figures-29

Figure 4.12-3. OCS Sand and Gravel Borrow Areas Within the AOI................................. Figures-30

Figure 4.12-4. Ocean Dredged Material Disposal Sites in the AOI ................................... Figures-31

Figure 4.12-5. Gulf of Mexico Energy Security Act (GOMESA) Areas. ............................. Figures-32
lxviii List of Figures

Figure 4.12-6a. Oil and Gas Platforms and Pipelines in the Western Planning Area 

in the AOI .................................................................................................... Figures-33

Figure 4.12-6b. Oil and Gas Platforms and Pipelines in the Central Planning Area 

in the AOI. ................................................................................................... Figures-34

Figure 4.12-6c. Oil and Gas Platforms and Pipelines in the Eastern Planning Area 

in the AOI .................................................................................................... Figures-35

Figure 4.12-7. Existing Submarine Telecommunications Cables Located in the AOI....... Figures-36

 
Gulf of Mexico G&G Activities Programmatic EIS lxix

LIST OF TABLES

Page

Table ES-1 Applicability of Mitigation Measures to G&G Surveys by Alternative.......................xiii

Table ES-2 Preliminary Screening of Potential Impacts (Leopold Matrix) ................................. xvii

Table 1.1-1. Federal Regulations Applicable to Pre-Lease and Post-Lease Activities 

by Mineral Resource of Interest......................................................................Tables-3

Table 1.4-1. Program Area, G&G Activity, Permitting Authority, and Typical NEPA 

ActionTables-5

Table 2-1. Applicability of Mitigation Measures to G&G Surveys by Alternative.............Tables-6

Table 2-2. Summary of Mitigation Measures Included in Alternatives A through F ........Tables-7

Table 2.5-1. Alternative E1: 10-Percent Reduction of Deep-Penetration Seismic, 

Multi-Client Activities’ (in line miles) Projected Levels of G&G Activities 

for Oil and Gas Exploration in the AOI .........................................................Tables-11

Table 2.5-2. Alternative E2: 25-Percent Reduction of Deep-Penetration Seismic, 

Multi-Client Activities’ (in line miles) Projected Levels of G&G Activities 

for Oil and Gas Exploration in the AOI .........................................................Tables-13

Table 2.7-1. Alternative G, the No New Activity Alternative: Projected Levels of G&G 

Activities in the AOI Over the 10-Year Period ..............................................Tables-15

Table 2.10-1. Impact Levels by Resource and Applicable IPF Across Alternatives A 

Through G, as Discussed in Chapter 2.10 ...................................................Tables-16

Table 3.1-1. Types of G&G Activities Included in this Programmatic EIS........................Tables-20

Table 3.2-1. Projected Levels of Acoustic Geophysical Activities for Oil and Gas 

Exploration in the AOI Over the 10-Year Time Period (numbers of 

surveys) and Survey Line Distance (miles)..................................................Tables-22

Table 3.2-2. Projected Levels of Non-Acoustic and Geological Activities for Oil and 

Gas Exploration in the AOI Over the 10-Year Time Period (numbers 

of surveys) and Survey Line Distance (miles) or Cores ...............................Tables-24

Table 3.2-3. Projected Levels of G&G Activities for Renewable Energy Site 

Characterization and Assessment in the AOI Over the 10-Year Time 

Period............................................................................................................Tables-25

Table 3.2-4. Projected Levels of Geological Surveys for OCS Marine Minerals 

Projects in the AOI Over the 10-Year Time Period ......................................Tables-26

Table 3.2-5. Projected Levels of Geophysical Surveys for Marine Minerals Projects 

in the AOI Over the 10-Year Time Period.....................................................Tables-27

Table 3.2-6. Characteristics of the Proposed G&G Activities Scenario in the AOI 

Over the 10-Year Time Period......................................................................Tables-29

Table 3.2-7. Vessel and Helicopter Traffic Associated with the Proposed Action............Tables-33

Table 3.2-8. Summary of All Projected Levels of G&G Activities in the AOI Over 

the 10-Year Time Period for the Oil and Gas, Renewable Energy, and 

Marine Minerals Program Areas...................................................................Tables-34

Table 3.3-1. Impact-Producing Factor Descriptions .........................................................Tables-35

Table 3.3-2. Characteristics of Active Acoustic Sound Sources Included in the 

Proposed Action............................................................................................Tables-36

Table 3.4-1. Cumulative Scenario Activities that Include Coincident Impact-Producing 

Factors with the Proposed Action G&G Activities ........................................Tables-37

Table 3.4-2. Summary of Oil and Gas Exploration and Development Activities in the

U.S. Gulf of Mexico Projected 10-Year Projections (based on 40-year 

projections) ....................................................................................................Tables-38

Table 3.4-3. Structure Removal Permit Applications on the AOI, 2002 to 2013 ..............Tables-39

Table 3.4-4. Structures Removed from the AOI, 2002 to 2013 ........................................Tables-39
lxx List of Tables

Table 3.4-5. Summary of Annual Oil and Gas Production from State Waters of 

Several Gulf States.......................................................................................Tables-39

Table 3.4-6. Summary of Deepwater Ports in the AOI .....................................................Tables-40

Table 3.4-7. Summary of Commercial Vessel Port Visits for Vessels >1,000 Gross 

Tons to AOI Ports in 2012 ............................................................................Tables-42

Table 3.4-8. Vessel Trips in the AOI in 2012 Recorded by Vessels Equipped with 

Automatic Identifications Systems................................................................Tables-43

Table 3.4-9. Cruise Ship Departures from Gulf Ports, by Year ........................................Tables-44

Table 4.1-1. Types of G&G Activities, by Survey Type, and Associated IPFs 

Associated with Each Survey Type as Described in Appendix F.................Tables-45

Table 4.1-2. Preliminary Screening of Potential Impacts (Leopold Matrix) ......................Tables-47

Table 4.1-3. Length and Area of Oiling of State and Federal Lands along the 

Northern Gulf Coast Caused by the Deepwater Horizon Oil Spill................Tables-48

Table 4.2-1. Marine Mammals Potentially Occurring in the AOI.......................................Tables-49

Table 4.2-2. Stocks of Bottlenose Dolphins within the AOI ..............................................Tables-53

Table 4.2-3. Functional Marine Mammal Hearing Groups, Associated Auditory 

Bandwidths, and Marine Mammal Species Present in the AOI....................Tables-54

Table 4.2-4. Dual Injury Criteria for Marine Mammals Exposed to Impulsive Noise 

Over a 24-Hour Period..................................................................................Tables-54

Table 4.2-5. Existing and Proposed Injury and Behavior Exposure Criteria for 

Cetaceans and Manatees Exposed to Pulsed Sounds ................................Tables-55

Table 4.2-6. Density Ratios for Each of the Modeling Zones and Seasonal 

Restrictions/Closure Areas ...........................................................................Tables-56

Table 4.3-1. Sea Turtles Occurring in the AOI..................................................................Tables-57

Table 4.4-1. Hard Bottom Species and Life Stages with Essential Fish Habitat 

Identified within the AOI................................................................................Tables-58

Table 4.4-2. Coastal Migratory Pelagic Species and Life Stages with Essential Fish 

Habitat Identified within the AOI ...................................................................Tables-65

Table 4.4-3. Highly Migratory Species and Life Stages with Essential Fish Habitat 

Identified within the AOI................................................................................Tables-66

Table 4.4-4. Shark Species and Life Stages with Essential Fish Habitat Identified 

within the AOI................................................................................................Tables-68

Table 4.5-1. Topographic Features (Banks) of the Gulf of Mexico...................................Tables-70

Table 4.6-1. Families of Seabirds, Waterfowl, and Shorebirds Occurring in the AOI ......Tables-71

Table 4.7-1. National System MPAs Within or Partially Within the AOI ...........................Tables-74

Table 4.9-1. 2012 Economic Impacts of the Gulf of Mexico Region Seafood Industry 

(thousands of dollars) ...................................................................................Tables-79

Table 4.9-2. Total Landings and Landings of Key Species/Species Groups 

(thousands of pounds)..................................................................................Tables-79

Table 4.9-3. Primary Commercial Fishing Methods, Target Species, Seasons, and 

General Areas Fished in the Gulf of Mexico.................................................Tables-80

Table 4.9-4. Summary of Seasonal and/or Area Closures to Commercial Fishing in 

Federal Waters in the Gulf of Mexico ...........................................................Tables-81

Table 4.10-1. Recreational Fishing Effort by Mode (thousands of angler-trips).................Tables-82

Table 4.10-2. 2012 Economic Impacts of Recreational Fishing Expenditures 

(thousands of dollars) ...................................................................................Tables-82

Table 4.10-3. Recreational Harvest (H) and Release (R) of Key Species and Species 

Groups (thousands of fish) ...........................................................................Tables-82

Table 4.10-4. Summary of Recreational Fishing Tournaments in the Gulf of Mexico........Tables-83

Table 4.12-1. Recent Marine Mineral Projects in Florida and Louisiana............................Tables-92

Table 4.13-1. Population Living in Gulf of Mexico Coastal Watershed Communities 

(1970 to 2010)...............................................................................................Tables-92

Table 4.13-2. 2012 Economic Impact of the Gulf of Mexico on Coastal Communities ......Tables-92
Gulf of Mexico G&G Activities Programmatic EIS lxxi

Table 4.13-3. 2012 Minority Populations in Geographic Areas Associated with Ports 

Serving the G&G Industry in the AOI............................................................Tables-93

Table 4.13-4. 2012 Low-Income Populations in Geographic Areas Associated with 

Ports Serving the G&G Industry in the AOI ..................................................Tables-94

Table 4.13.9-1. Survey Incremental Cost and Percent Cost Change by Alternative ............Tables-95

Table 4.13.9-2. Total Annual Survey Incremental Cost by Alternative..................................Tables-96

Table 4.13.9-3. Percent Change in Operational Efficiency by Alternative.............................Tables-97

Gulf of Mexico G&G Activities Programmatic EIS lxxiii

ABBREVIATIONS AND ACRONYMS

μPa micropascal

μs microsecond

2D two-dimensional

3D three-dimensional

4C four-component

4D four-dimensional

ac acre

AFTT Atlantic Fleet Training and Testing

AIS Automated Identification System

AOI Area of Interest

API American Petroleum Institute

bbl barrel

BCR Bird Conservation Region

BIA Biologically Important Area

BOEM Bureau of Ocean Energy Management

BOEMRE Bureau of Ocean Energy Management, Regulation and Enforcement

BOP blowout preventer

BSE Bay, Sound, and Estuary (stock)

BSEE Bureau of Safety and Environmental Enforcement

CAA Clean Air Act

CATEX categorical exclusion

CEQ Council on Environmental Quality

CetMap Cetacean Density and Distribution Mapping Working Group

CFR Code of Federal Regulations

CHIRP compressed high-intensity radiated pulse

cm centimeter

CMP coastal management program

CMSP coastal and marine spatial planning

CO carbon monoxide

CO2 greenhouse gases

COA condition of approval

COLREGS International Regulations for Preventing Collisions at Sea

COP Construction and Operation Plan

CP Central Planning (for the closure area)

CPA Central Planning Area

CPT cone penetrometer test

CSEM controlled source electromagnetic

CWA Clean Water Act

CWPPRA Coastal Wetlands Planning, Protection and Restoration Act

CZMA Coastal Zone Management Act

dB decibel

DCL detection, classification, and localization

DFO Fisheries and Oceans Canada

DOCD Development Operations Coordination Documents
lxxiv Abbreviations and Acronyms

DoD U.S. Department of Defense

DOI U.S. Department of the Interior (also: USDOI)

DP dynamic positioning

DPS distinct population segment

DTAGS deep-towed acoustics/geophysical system

EA Environment Assessment

EEZ Exclusive Economic Zone

EIS Environmental Impact Statement

EO Executive Order

EP Eastern Planning (for the closure area)

EPA Eastern Planning Area

EPAct Energy Policy Act

ESA Endangered Species Act

EWTA Eglin Water Test Area

FGB Flower Garden Banks

FGBNMS Flower Garden Banks National Marine Sanctuary

FKNMS Florida Keys National Marine Sanctuary

FMC Fishery Management Council

FONSI Finding of No Significant Impact

FR Federal Register

ft feet

ft2 square feet

FWC Florida Fish and Wildlife Conservation Commission

FWS Fish and Wildlife Service (U.S. Department of the Interior)

G&G geological and geophysical

gal gallon

GAP General Activities Plan

GMFMC Gulf of Mexico Fishery Management Council

GOM Gulf of Mexico

GOMESA Gulf of Mexico Energy Security Act

GOMEX Gulf of Mexico (Range Complex)

GoMRI Gulf of Mexico Research Initiative

H.R. House Report

H2S hydrogen sulfide

HAPC Habitat Area of Particular Concern

Ho-Ho Houston to Houma (pipeline)

HRG high-resolution geophysical

HSSE health, safety, security, and environment

Hz hertz

IBA Important Bird Area

IPCC Intergovernmental Panel on Climate Change

IPF impact-producing factor

ITA incidental take authorization

IUCN International Union for Conservation of Nature

J joule

JIP Joint Industry Programme
Gulf of Mexico G&G Activities Programmatic EIS lxxv

JNCC Joint Nature Conservation Committee

kg kilogram

kHz kilohertz

km kilometer

km2 square kilometer

kn knot

LACS low-frequency acoustic source

lb pound

LC Loop Current

LFPS low-frequency passive seismic

LISA low-impact seismic array

LNG liquefied natural gas

LOOP Louisiana Offshore Oil Port

m meter

m2 square meter

MARAD Maritime Administration (U.S. Department of Transportation)

MARPOL International Convention for the Prevention of Pollution from Ships

MBES multibeam echosounder

MDA Mississippi Development Authority

mi mile

mi2 square mile

MISLE Marine Information for Safety and Law Enforcement

mm millimeter

MMP Marine Minerals Program (BOEM)

MMPA Marine Mammal Protection Act

MMS Minerals Management Service

MOA Memorandum of Agreement

MODU mobile offshore drilling unit

MOU Memorandum of Understanding

MPA Marine Protected Area

mph mile per hour

ms millisecond

MSA Metropolitan Statistical Area

MSFCMA Magnuson-Stevens Fisheries Conservation and Management Act

mt metric ton

MT magnetotelluric

MW megawatt

MWA Military Warning Area

NABCI North American Bird Conservation Initiative

NAO NOAA Administrative Order

NARW North Atlantic right whale

NAZ narrow azimuth

NDBC National Data Buoy Center

NEPA National Environmental Policy Act

NERR National Estuarine Research Reserve

NGO nongovernmental organization
lxxvi Abbreviations and Acronyms

NHPA National Historic Preservation Act

NMFS National Marine Fisheries Service

nmi nautical mile

NMS National Marine Sanctuary

NMSA National Marine Sanctuaries Act

NOAA National Oceanic and Atmospheric Administration

NOI Notice of Intent

NOR Notice of Receipt

NOS National Ocean Service

NOx nitrogen oxide

NPDES National Pollutant Discharge Elimination System

NPS National Park Service

NRC National Research Council

NRDA Natural Resource Damage Assessment

NRDC National Resources Defense Council Inc.

NREL National Renewable Energy Laboratory (USDOE)

NRHP National Register of Historic Places

NSF National Science Foundation

NTL Notice to Lessees and Operators

NWR National Wildlife Refuge

OBC ocean bottom cable

OBN ocean bottom node

OCS Outer Continental Shelf

OCSLA Outer Continental Shelf Lands Act

ODMDS ocean dredged material disposal site

OMNS National Office of Marine Sanctuaries (NOAA)

OPAREA (U.S. Navy) Operating Area

OREP Office of Renewable Energy Programs (BOEM)

OSP optimum sustainable population

P.L. Public Law

PAH polycyclic aromatic hydrocarbon

PAM passive acoustic monitoring

PBR potential biological removal

PCB polychlorinated biphenyl

PEA Programmatic Environmental Assessment

Pemex Petróleos Mexicanos

PM particulate matter

ppm parts per million

PSO protected species observer

PTS permanent threshold shift

RE resource evaluation

RHA Rivers and Harbors Act

rms root mean square

ROV remotely operated vehicle

SAFMC South Atlantic Fishery Management Council

SAP Site Assessment Plan
Gulf of Mexico G&G Activities Programmatic EIS lxxvii

SAR Stock Assessment Report

SAV submerged aquatic vegetation

SBES single-beam echosounder

SBF synthetic-based fluid

ScOT Screening Out Team

SEA site-specific environmental assessment

SEL sound exposure level

SLR sea-level rise

SOx sulfur oxide

SPL sound pressure level

SRG Scientific Review Group

TMA target motion analysis

TTS temporary threshold shift

U.S. United States

U.S.C. United States Code

ULCC ultra-large crude carrier

UME unusual mortality event

USACE U.S. Department of the Army, Corps of Engineers

USCG U.S. Department of Homeland Security, Coast Guard

USDOC U.S. Department of Commerce

USDOE U.S. Department of Energy

USDOI U.S. Department of the Interior (also: DOI)

USEPA U.S. Environmental Protection Agency

USGS U.S. Department of the Interior, Geological Survey

VLCC very large crude carrier

VOC volatile organic compound

VSP vertical seismic profile

WAZ wide azimuth

WBF water-based fluid

WCD worst-case discharge

WPA Western Planning Area

WW wet weight

yd3 cubic yard

Gulf of Mexico G&G Activities Programmatic EIS lxxix

CONVERSION CHART

To convert from To Multiply by

centimeter (cm) inch (in) 0.3937

millimeter (mm) inch (in) 0.03937

meter (m) foot (ft) 3.281

meter2 (m2) foot2 (ft2) 10.76

meter2 (m2) yard2 (yd2) 1.196

meter2 (m2) acre (ac) 0.0002471

meter3 (m3) foot3 (ft3) 35.31

meter3 (m3) yard3 (yd3) 1.308

kilometer (km) mile (mi) 0.6214

kilometer2 (km2) mile2 (mi2) 0.3861

hectare (ha) acre (ac) 2.47

liter (L) gallons (gal) 0.2642

degree Celsius (°C) degree Fahrenheit (°F) °F = (1.8 x °C) + 32

1 barrel (bbl) = 42 gal = 158.9 L = approximately 0.1428 metric tons

1 nautical mile (nmi) = 1.15 mi (1.85 km) or 6,076 ft (1,852 m)

tonnes = 1 long ton or 2,240 pounds (lb)

CHAPTER 1 

INTRODUCTION

Gulf of Mexico G&G Activities Programmatic EIS 1-3 

1 INTRODUCTION

The Bureau of Ocean Energy Management’s (BOEM) mission is to manage development of 

U.S. Outer Continental Shelf (OCS) energy and mineral resources in an environmentally and 

economically responsible way. BOEM, as the lead Federal agency, is preparing this Programmatic 

Environmental Impact Statement (EIS) to describe and evaluate the potential environmental impacts 

related to reasonably foreseeable geological and geophysical (G&G) survey activities in Federal and 

affected State waters of the Gulf of Mexico (GOM), as mandated in the Outer Continental Shelf 

Lands Act (OCSLA). The Bureau of Safety and Environmental Enforcement (BSEE) and the 

National Oceanic and Atmospheric Administration (NOAA) are serving as cooperating agencies. 

Appendix A provides the Memoranda of Agreement (MOAs) between BOEM and the cooperating 

agencies describing the obligations of the agencies concerning the preparation of this Programmatic 

EIS, and Chapter 6.3.3 further discusses the cooperating agency status and roles.

This Programmatic EIS addresses potential environmental impacts of BOEM’s oil and gas, 

renewable energy, and marine mineral resource programs and focuses particularly on the 

environmental impacts of off-lease and on-lease geological (bottom sampling and test drilling) and

geophysical surveys (deep-penetration, high-resolution geophysical [HRG], electromagnetic, deep 

stratigraphic, and remote sensing).

The area evaluated (Area of Interest, or AOI) includes the OCS waters of the GOM and the 

waters above the OCS that are within BOEM’s GOM planning areas (Western, Central, and Eastern

Planning Areas [WPA, CPA, and EPA]). The AOI also includes coastal waters of Texas, Louisiana, 

Mississippi, Alabama, and Florida extending from the coastline (outside of estuaries) seaward 

3 nautical miles (nmi) (3.5 miles [mi]; 5.6 kilometers [km]) (Louisiana, Mississippi, and Alabama) or 

9 nmi (10.4 mi; 16.7 km) (Texas and Florida) to the limit of State jurisdiction.

1.1 PROPOSED ACTION AND PURPOSE AND NEED

1.1.1 Proposed Action

BOEM’s proposed action is the issuance of permits or authorizations for G&G activities in 

the GOM. The proposed action specifically includes the following:

(1) continuance of G&G operations in the GOM subject to regulatory authorities 

including, but not limited to, 30 CFR parts 551, 580, and 585; Section 11 and 

Subsections 8(k) and 8(p) of the OCSLA; and Section 388(a) of the Energy 

Policy Act of 2005 (EPAct); and

(2) continuance of G&G activities conducted under a lease as described in 30 CFR 

part 550 (Appendix B, Section 1.1.15).

The activities included in BOEM’s permitting or authorization process described above cover 

G&G activities associated with the exploration, development, and/or scientific research of oil, gas, 

sulfur, other minerals (e.g., sand), and alternative energy-related resources. For oil and gas 
1-4 Introduction

activities, there are different phases of G&G activities, including pre-lease, on-lease, and post-lease 

activities, as well as ancillary activities. Surveys done by a lessee in support of a BOEM-issued oil 

and gas lease that are on and around geospatial lease boundaries are regulated under the terms of 

a lease agreement and are referred to as “ancillary activities” (also referred to as on-lease activities) 

(refer to 30 CFR § 550.207). For pre-lease oil and gas activities (prior to a lease sale), a permit 

must be obtained from BOEM prior to conducting G&G activities on any unleased OCS lands or on 

lands under lease to a third party (30 CFR §§ 551.4(a) and (b)). Additional G&G surveys are 

performed post-lease (after a lease sale has been held and leases issued), including engineering 

studies that are used to guide the placement of production facilities and pipelines in deep water as 

well as to meet archaeological requirements. Tables 1.1-1 and 1.4-1 provide additional information 

regarding activities performed during these phases.

The National Marine Fisheries Service’s (NMFS) proposed action will be a direct 

outcome of responding to BOEM’s request for incidental take regulations under the Marine Mammal 

Protection Act of 1972, as amended (MMPA; 16 U.S.C. §§ 1361 et seq.), for the “take” of marine 

mammals incidental to G&G activities conducted by the oil and gas industry in the GOM. The term 

"take," as defined in the MMPA (16 U.S.C. § 1362(13)), means to “harass, hunt, capture, or kill, or 

attempt to harass, hunt, capture, or kill any marine mammal.” The NMFS intends to use this 

Programmatic EIS as the National Environmental Policy Act (NEPA) documentation associated with 

the issuance of incidental “take” authorizations and rule-making process under the MMPA for the 

incidental taking of marine mammals in connection with all G&G survey activities in the GOM. 

1.1.2 Purpose and Need

The purpose of the proposed action is to gather state-of-the-practice data about the ocean 

bottom and subsurface. These data, collected through G&G activities, would provide information 

about (1) the potential location and extent of oil and gas reserves, (2) the locations for placement of 

oil and gas or renewable energy installations and excavation of marine mineral resources, and 

(3) about the composition and volume of identified seafloor sediment deposits (e.g., marine minerals 

required for wetland, beach, and coastal restoration projects).

Current G&G data and information are required to support leasing, resource assessment, 

and planning decisions while taking into account environmental stewardship and protection. The 

G&G data also further support BOEM’s mandate that the OCS be made available for expeditious 

and orderly development, subject to environmental safeguards, while maintaining competition for the 

OCS resources, including, but not limited to (1) exploration and development of oil and gas 

resources, (2) assessing sites for renewable energy facilities, (3) preservation of marine 

archaeological resources in compliance with Sections 106 and 110 of the National Historic 

Preservation Act (NHPA), and (4) using marine mineral resources in the three GOM planning areas 

to support beach restoration and nourishment projects.

The need for the proposed action is to have access to and use of the best available 

information obtained from G&G activities in order to make informed business, management, design, 
Gulf of Mexico G&G Activities Programmatic EIS 1-5 

stewardship, and environmental protection decisions. Such decisions are an integral part of several 

OCS programs, including oil and gas (e.g., location, extent, fair market value of resources, and 

orderly development of hydrocarbon reserves), renewable energy (e.g., engineering decisions 

regarding the construction of renewable energy projects), and marine minerals (e.g., informed 

estimates regarding the composition and volume of marine mineral resources). This information 

would also be used to ensure (1) the issuance of permits and authorizations follows OCSLA’s 

principles of activities being conducted in a technically safe and environmentally sound manner, 

(2) the proper use and conservation of OCS energy resources, (3) receipt of fair market value for the 

leasing of public lands, (4) development of current estimates of potential reserves, and (5) efficient 

future production of resources.

This Programmatic EIS will enable BOEM and NMFS to fulfill statutory responsibilities 

associated with permitting or authorizing G&G activities/ the take of marine mammals in connection 

with activities conducted in support of oil and gas, renewable energy, and marine minerals programs 

on the Gulf of Mexico OCS. These responsibilities include assessing the reasonably foreseeable 

impacts to the marine environment from G&G activities, meeting listed and protected species 

consultation requirements, and incorporating measures to protect resources present in the GOM.

1.1.3 Area of Interest

The AOI is the area in which the activities of the proposed action would take place and, 

therefore, the area of potential effect by the proposed action. The AOI includes the OCS of the 

GOM and the waters above the OCS that are within BOEM’s GOM Western, Central, and Eastern 

Planning Areas (WPA, CPA, and EPA). The AOI also includes coastal waters of Texas, Louisiana, 

Mississippi, Alabama and Florida extending from the coastline (outside of estuaries) seaward 3 nmi

(3.5 mi; 5.6 km) (Louisiana, Mississippi, and Alabama) or 9 nmi (10.4 mi; 16.7 km) (Texas and 

Florida) to the limit of State jurisdiction (Figure 1.1-1). While this Programmatic EIS analyzes the 

entire AOI, it is important to note that the impacted areas for renewable energy and the marine 

minerals program’s activities is only a small portion of the entire AOI (i.e., the marine minerals 

program AOI is 1.06 percent of the AOI covered by this Programmatic EIS).

This Programmatic EIS addresses resources that are found in or migrate through the AOI 

and adjacent areas and that may be affected by the proposed action. The AOI inner boundary 

follows the shoreline along most of the coast but extends across the mouths of estuaries and bays 

as necessary. State waters are not within the jurisdiction of BOEM, but rather the State itself and 

the U.S. Army Corps of Engineers (USACE), who permits these activities in State waters.

Despite limits to its regulatory authority, BOEM is addressing adjacent State waters in this 

Programmatic EIS because

(1) NMFS has jurisdiction and MMPA permitting authority in Federal and State 

waters, and requires an assessment of potential impacts to the human 

environment;
1-6 Introduction

(2) the acoustic energy introduced into the environment during G&G activities in 

Federal waters could affect resources in State waters; and

(3) G&G activities could include interrelated and connected activities in Federal and 

State waters that would be considered connected actions.

In December 2013, the U.S. Congress approved the U.S.-Mexico Transboundary 

Hydrocarbons Agreement (Public Law [P.L.] 113-67, the Bipartisan Budget Act of 2013), which aims 

to facilitate joint development of oil and natural gas in part of the Gulf of Mexico. This, coupled with 

recent reforms in Mexico, could transform Mexican GOM waters into a more developed oil and gas 

landscape including infrastructure development and cross-border pipelines.

The opening of these waters to leasing will make it possible for U.S. lessees to enter into 

voluntary agreements with a licensee of the United Mexican States to develop transboundary 

reservoirs. The Transboundary Agreement contains a stipulation that applies only to lease blocks or 

portions of lease blocks located within 3 statute miles (4.8 km) of the Maritime or Continental Shelf 

Boundary with Mexico (formerly known as the “buffer zone”).

In January of 2015, Mexico issued rules for seismic exploration and, while new leasing has

had a slow start following Mexican constitutional reforms, geophysical companies are moving 

forward aggressively to acquire data in Mexican waters of the GOM. To date, at least nine

companies have permits either pending or approved, and two-dimensional (2D) and threedimensional (3D) data collection has begun. Many of these companies have permits from BOEM for 

U.S. waters as well. For instance, Mexico’s Petroleos Mexicanos (Pemex) can now partner with 

international companies that have the experience and capital required for exploring Mexico’s deep 

water and shale resources.

In reference to G&G data, the actual ownership of the seismic data is retained on the U.S. 

side by the geophysical contractors or the lessees who may have contracted for exclusive ownership 

of that data. The contractors sell licenses for the usage of that seismic data to potential lessees. 

Exploration and production companies may also purchase and retain such proprietary data from 

contractors (USDOI, BOEM, 2015a).

1.2 BACKGROUND

Section 18 of OCSLA directs the USDOI to conduct environmental studies and prepare any 

EIS required in accordance with OCSLA and with Section 102(2)(C) of NEPA (42 U.S.C. § 

4332(2)(C)). To implement this and other energy and mineral responsibilities, the Secretary of the 

Interior designated BOEM as the agency responsible for leasing submerged OCS lands for 

development and production and for approving operational plans. OCSLA also directs BOEM to 

ensure G&G data are obtained in a technically safe and environmentally sound manner. The G&G 

activities are subject to various permits, authorizations, and notices. BOEM oversees G&G data 

acquisition and permitting activities pursuant to regulations at 30 CFR parts 550, 551, 580, and 585; 

Subsections 8(k) and 8(p) of OCSLA; and Section 388(a) of EPAct (USDOI, BOEM, 2013a).
Gulf of Mexico G&G Activities Programmatic EIS 1-7 

This Programmatic EIS would establish a framework for subsequent NEPA analyses of sitespecific actions and also identifies and analyzes potential mitigation measures for use in future G&G 

activities on the Gulf of Mexico OCS involving all three of BOEM’s program areas. BOEM will 

address the impacts of future site-specific actions in subsequent NEPA evaluations (40 CFR § 

1502.20) using a tiered process based on this programmatic evaluation.

In conjunction with this Programmatic EIS, BOEM plans to submit its MMPA application to 

NMFS, requesting the issuance of regulations governing the authorization of incidental take of 

marine mammals in the GOM under Section 101(a)(5) of the MMPA on behalf of oil and gas and 

geophysical companies for geophysical-permitted (authorized) and ancillary activities. The G&G 

surveys conducted in support of marine mineral beach nourishment or coastal restoration projects 

under a non-competitive lease and renewable energy projects would separately comply with the 

Endangered Species Act (ESA), MMPA, and other relevant laws, regulations, and Executive Orders 

(EOs) as deemed appropriate by all agencies on a project-by-project basis.

The NMFS intends to use this Programmatic EIS as the NEPA documentation associated 

with the issuance of incidental “take” authorizations and rule-making process under the MMPA and 

the Section 7 Consultation process under the ESA for the incidental taking of marine mammals and 

ESA-listed species during G&G survey activities. Additional information regarding these agencies, 

roles, and regulations is provided in Chapter 6 and Appendix B. 

1.2.1 History of G&G Environmental Review in the GOM

In 1976, the U.S. Geological Survey (USGS) completed an EIS evaluating the impacts of 

policies and procedures set forth in proposed regulations for G&G surveys within the Gulf of Mexico

OCS. In 1984, the Minerals Management Service (MMS; BOEM’s predecessor)

1 completed a 

Programmatic Environmental Assessment (EA) that analyzed the potential impacts of G&G activities 

in the GOM (USDOI, MMS, 1984). Based on the information available at the time, MMS concluded 

that no significant impact was expected. The MMS further determined that the vast majority of G&G

 

1 On May 19, 2010, USDOI Secretary Salazar announced in Secretarial Order 3299 that MMS would be

reorganized into two new bureaus within the USDOI, each reporting to the Assistant Secretary of Land 

and Minerals Management, as well as the Office of Natural Resources Revenue (USDOI, 2010a). The 

two bureaus would come to be known as BOEM and BSEE. BOEM administers leasing and plans, 

environmental studies, NEPA analysis, resource evaluation, economic analysis, and the renewable 

energy and marine minerals programs. The BSEE administers all field operations including permitting 

and research, inspections, research, offshore regulatory programs, oil-spill response, and newly formed 

training and environmental compliance functions. After the new organizations were announced, on June

18, 2010 (USDOI, 2010b), the Secretary issued Secretarial Order 3302 that, for the interim, changed the 

name of the former MMS to the Bureau of Ocean Energy Management, Regulation and Enforcement 

(BOEMRE). On October 1, 2011, BOEM and BSEE were officially created and succeeded BOEMRE.
1-8 Introduction

activities could be categorically excluded2 from additional NEPA review and this determination was 

adopted as department policy by USDOI. The Council on Environmental Quality (CEQ) provided its 

concurrence with that determination. 

In 2005, the Minerals Management Service’s NEPA team determined that seismic surveys 

using air or water guns and solid or liquid explosives should not be categorically excluded (USDOI, 

MMS, 2007a) and required further analysis under NEPA. In 2006, MMS narrowed the application of 

the categorical exclusions (CATEXs) (C9/C13 in the existing Department Manual) to exclude seismic 

surveys using airguns and in December 2009, narrowed the application of CATEXs again to exclude 

all deep-penetration seismic airgun surveys, HRG surveys, and vertical seismic profile (VSP) 

surveys. However, MMS continued to allow HRG surveys without air guns to be approved under the 

CATEXs if no extraordinary circumstances were identified.

During site-specific analyses for a variety of G&G survey activities, including geological 

sampling and geophysical surveys using airguns, it may be determined that additional NEPA 

analysis in the form of an EA or EIS must be prepared for the proposed activity. In the event an 

action cannot be categorically excluded, the decision to prepare an EA will be made by the Regional 

Supervisor, Office of Environment or the Chief, Environmental Division. Currently, EAs are prepared 

for G&G activities that include airguns, such as high resolution surveys, 2D and 3D seismic surveys, 

ocean bottom nodes, and ocean bottom cables and any non-airgun activities that have the potential 

to impact benthic or archaeological resources such as geologic cores and grab samples.

1.2.2 Petition for Authorization to Take Marine Mammals Incidental to 

Conducting Oil and Gas Exploration Activities in the Gulf of Mexico

On December 20, 2002, the MMS petitioned the NMFS for rulemaking under Section 

101(a)(5)(A) of the MMPA to authorize any potential take of sperm whales (Physeter 

macrocephalus) incidental to operators conducting seismic surveys during oil and gas exploration 

activities in GOM. On March 3, 2003, the NMFS published a notice of receipt (NOR) of the petition 

and requested comments and information from the public (68 FR 9991), later extended to April 16, 

2003 (68 FR 16262). The MMS prepared a Programmatic Environmental Assessment 

(Programmatic EA) for the petition, completed in July 2004. Based on the Programmatic EA’s

findings, BOEM submitted a revised petition in September 2004 to request incidental take 

regulations for the incidental take of all NMFS-protected marine mammals considered to routinely 

inhabit the GOM and potentially impacted by seismic surveys related to oil and gas exploration and 

development activities.

Based on review of public comments received on the 2002 petition, the 2004 revised MMPA 

petition, and the 2004 Programmatic EA, the NMFS determined, and the MMS agreed, that an EIS 

 

2 Categorical Exclusions (CATEXs) are "a category of actions which do not individually or cumulatively 

have a significant effect on the human environment . . . and for which, therefore, neither an environmental 

assessment nor an environmental impact statement is required" (40 CFR § 1508.4).
Gulf of Mexico G&G Activities Programmatic EIS 1-9 

was warranted and published an NOI to prepare an EIS in November 2004 (69 FR 67535). This 

decision was based on a combination of the following factors:

• public concern over impacts of oil and gas exploration activities on the marine 

environment, which includes marine mammals;

• proposed use of computer modeling as one of two methods for calculating 

incidental take levels for marine mammals and sea turtles for a geographic area 

where multiple seismic sources may be operating simultaneously;

• incorporation of a scientifically based risk assessment for marine mammals;

• possible use of energy criteria rather than pressure criteria to calculate marine 

mammal take levels, especially to calculate potential multiple exposures; and

• incorporation of new acoustic guidelines for assessing impacts of sound on 

marine mammals (69 FR 67535).

After the NOI was published, the NMFS worked on the development of the EIS with the MMS 

serving as a cooperating agency. In 2008, the NOAA requested that the MMS be a co-lead agency; 

however, a Memorandum of Understanding (MOU)/MOA was not finalized until 2013 after the 

reorganization of the MMS. After further evaluation following scoping, the two agencies determined 

that, pursuant to 40 CFR §§ 1501.5 and 1501.6, BOEM should serve as the lead agency and the 

NOAA serve as a cooperating agency.

BOEM provided the NMFS with a revised MMPA petition on April 18, 2011, which 

incorporated updated information and analyses since the 2004 petition. The NMFS published an 

NOI of the petition on June 14, 2011 (76 FR 34656).

On May 10, 2013, BOEM announced its intent to prepare a Programmatic EIS and reopened 

a second public scoping period under NEPA to gather public comments on the content and issues to 

consider in the Programmatic EIS (78 FR 27427). This Programmatic EIS is being prepared to 

serve as the programmatic NEPA analysis from which BOEM will tier its site-specific NEPA analysis 

for BOEM to permit or authorize G&G activities under the OCSLA; to provide necessary information 

and assessment under NEPA to support the NMFS’ decisionmaking regarding MMPA authorizations 

for G&G activities on the OCS; and to support additional coordination and consultation requirements 

under other statutes, including the ESA, Magnuson-Stevens Fishery Conservation and Management 

Act (MSFCMA), Coastal Zone Management Act (CZMA), National Marine Sanctuaries Act (NMSA), 

and NHPA. These statutes are further described in Appendix B. 

1.2.3 Litigation Settlement

On June 30, 2010, the Natural Resources Defense Council (NRDC) et al. (the “Plaintiffs”) 

filed a Complaint for Declaratory and Injunctive Relief (the “Complaint”) alleging that BOEM’s 

predecessor had violated NEPA by concluding that no EIS was required to assess the impact of 
1-10 Introduction

G&G exploration for mineral resources in the Gulf of Mexico OCS. A settlement was reached 

between the parties (i.e., NRDC et al.; U.S. Department of the Interior [DOI]; and industry 

intervenors) on June 24, 2013 (the “Settlement Agreement”). The Settlement Agreement provided 

that all proceedings in the litigation were stayed for 30 months from the day in which the Settlement 

Agreement was approved (which was set to expire on December 25, 2015) or until the terms of the 

Settlement Agreement were satisfied, whichever came first. On February 10, 2016, the parties 

formally agreed to extend the stay until final action by the agencies or September 25, 2017, 

whichever occurs first. The terms of the Settlement Agreement are fully considered in this 

Programmatic EIS. More detailed information regarding the Settlement can be found in Appendix C

and on BOEM’s website at http://www.boem.gov/Civil-Action-No-2-10-cv-01882-SettlementAgreement. Highlights of the Settlement Agreement’s content are discussed in the following 

sections. 

Interim Mitigating Measures

While the stay is in effect, BOEM is required to analyze the following mitigation measures as 

potential conditions of approval (COAs) for permit applications for deep-penetration seismic surveys 

in EAs specific to permitting decisions for individual deep-penetration seismic surveys (i.e., airgun 

surveys) and in this Programmatic EIS. Industry has included these measures in their applications 

for permits and authorizations for the duration of the stay. These interim mitigation measures are 

presented in detail as Alternative B (Chapter 2), and the impact analyses are presented in 

Chapter 4. 

(1) Seasonal Restrictions for Coastal Waters – The permittee shall not operate 

any airguns or airgun arrays in Federal coastal waters of the GOM shoreward of 

the 20-m (66-ft) isobath between January 1 and April 30.

(2) Expansion of NTL 2012-JOINT-G02 – The permittee will comply with this 

Notice to Lessees and Operators (NTL) with the following changes: the 

provision in paragraph 4 of page 3 of NTL 2012-JOINT-G02 (i.e., that a 

permittee will immediately shut down all airguns ceasing seismic operations at 

any time a whale is detected entering or within the exclusion zone; the 

permittee may re-commence seismic operations and ramp-up of airguns only 

when the exclusion zone has been visually inspected for at least 30 minutes to 

ensure the absence of marine mammals and sea turtles) shall apply to 

manatees as well as whales, and this NTL will apply to all deep-penetration 

seismic surveys in the GOM regardless of water depth. This NTL, which 

replaces NTL 2007-G02, was issued to clarify the implementation of seismic 

survey measures, including ramp-up procedures, the use of a minimum sound 

source, airgun testing, and protected species observation and reporting.

(3) Minimum Separation Distances – When operating in the designated Areas of 

Concern (refer to Chapter 2.2, Alternative B, for details on Areas of Concern 

identified by Plaintiffs in the Settlement), the simultaneous deep-penetration 
Gulf of Mexico G&G Activities Programmatic EIS 1-11

seismic surveys (i.e., airgun surveys) will maintain a separation distance of 

40 km (25 mi) between active sound sources. When outside the Areas of 

Concern, the separation distance shall be 30 km (19 mi). This separation 

requirement does not apply to multiple ships operating in a coordinated survey, 

such as a wide azimuth (WAZ) survey, and need not be maintained if unsafe or 

during unfavorable weather conditions.

(4) Seismic Restriction in the EPA – Deep-penetration seismic surveys (i.e., 

airgun surveys) will not be conducted within the portion of the Areas of Concern 

falling within the EPA. This restriction does not apply to currently leased blocks, 

any portion of the area encompassed by EPA Lease Sale 226, or neighboring 

blocks adjacent to permitted survey areas but within an otherwise off-limit area.

(5) Passive Acoustic Monitoring (PAM) – Seismic surveys occurring during 

periods of reduced visibility in waters deeper than 100 m (328 ft) will include 

PAM as a part of the protected species observer (PSO) program.

(6) Reporting Requirements – Operators will provide biweekly reports on the 

seismic survey and confirm compliance with required mitigation measures.

In addition, while the stay is in effect, applicants for deep-penetration seismic survey 

permits agreed to provide the following information to BOEM:

(1) Non-Duplicative Surveys – The applicant must provide an explanation for why 

the proposed deep-penetration seismic survey is not unnecessarily duplicative 

of previously conducted surveys, taking into account technology, targeted 

formations, geographic areas of surveys, and other relevant considerations.

(2) Lowest Practicable Source Levels – The applicant must provide an estimate 

of the total energy output in decibels (root mean square [rms]), referenced to a 

standard pressure, for each proposed energy source. The applicant must 

certify that, to the extent practicable, the proposed array is operating at the 

lowest sound intensity that will achieve the survey’s goals. Verification includes 

confirmation that the array has been calibrated to maximize subsurface 

illumination while minimizing horizontal noise projection.

On February 10, 2016, the parties formally agreed to extend the terms of the Settlement 

Agreement and the stay until final action by the agencies or September 25, 2017, whichever occurs 

first. In addition, the extended Settlement Agreement amended Article V of the Settlement to include 

the following expanded/additional mitigation measures during the stay:

• Expanded Time Area Closure in Certain Areas of Concern Not Located in 

the EPA – Deep-penetration seismic surveying will not be conducted during the 

period from January 1 through April 30 in the portion of the 20-m (66-ft) isobath 

outside the EPA that is covered by the recent Unusual Mortality Event (UME) 
1-12 Introduction

declared for cetaceans by the NOAA (i.e., from the Texas/Louisiana border to the 

eastern border of Franklin County, Florida).

• Buffer Zone around Areas of Concern – A 5-km (3-mi) buffer zone will be 

established adjacent to and seaward of the 20-m (66-ft) isobath and to the 

remaining Areas of Concern that fall within the EPA. Activities in the buffer 

zones will be subject to the same restrictions and requirements that apply to the 

areas to which they are adjacent, during the same time periods.

BOEM has modified Alternative B in this Programmatic EIS to reflect the expansion of 

mitigation measures in Article V of the Settlement and the resulting analyses.

Settlement Agreement Items for Analysis in this Programmatic EIS

In the Settlement, BOEM agreed to the following:

• Convene an internal panel or panels with sufficient geophysical and 

environmental expertise to determine whether it would be feasible to develop 

standards for determining

− whether a deep-penetration seismic survey is unnecessarily duplicative (refer 

to Appendix L);

− the lowest practicable source level for a deep-penetration seismic survey 

(refer to Appendix L); and

− if a draft EIS or EA has not been released prior to the panels’ determinations, 

include the standards if the determination is positive, or the rationale for the 

determination if the determination is negative, within the EIS or EA.

• To analyze alternatives and mitigating measures in any NEPA document (EIS or 

EA) for BOEM’s Marine Mammal Protection Act application that are similar to

− mitigating measures described in the Interim Mitigating Measures (refer to

Chapter 4): 

− means to reduce chronic or cumulative exposure of marine mammal 

populations to noise (refer to Chapter 4); and

− requirements or incentives to use new alternative technologies to accomplish 

deep-penetration seismic surveys (refer to Chapter X).

• To analyze in any NEPA document (i.e., EIS or EA) for BOEM’s Marine Mammals 

Protection Act application the development of a long-term adaptive monitoring plan 

to address potential chronic and cumulative impacts from seismic surveys on marine 

mammal populations in the GOM.
Gulf of Mexico G&G Activities Programmatic EIS 1-13 

Non-Duplicative Surveys and Lowest Practicable Source Levels Panels 

As contemplated in Article VIII of the Settlement Agreement, BOEM convened two panels to 

evaluate the potential to determine whether it is feasible to develop standards for determining 

(1) whether a deep-penetration seismic survey is unnecessarily duplicative and (2) what is the 

lowest practicable source level for deep-penetration seismic surveys. The analyses conducted by 

these two panels were novel and highly technical. The complexity of their analysis is further 

exacerbated by the following: (a) the fact that different data acquisition techniques and, as a 

consequence, algorithmic processing methods, resulting from recent developments in technology to 

illuminate difficult geologic areas (i.e., subsalt) often influence whether an area needs to be surveyed 

more than once; and (b) a wide array of confidential business information, trade secrets, intellectual 

property, and regulatory considerations that must be considered in conjunction.

The panel report and determination on unnecessarily duplicative surveys is presented in 

Appendix L. The panel consisted of internal BOEM subject-matter experts assisted by outside 

experts from the Marine Mammal Commission and the geophysical industry. The panel met 

numerous times since 2013 to more explicitly define “unnecessarily duplicative” and then to discuss, 

evaluate, and determine whether standards for assessing if a newly proposed seismic survey is 

“unnecessarily duplicative” of previous surveys could be created. The final determination of this 

panel was that standards to determine whether a newly proposed seismic survey is unnecessarily 

duplicative of previous surveys is feasible and that this could be accomplished under existing 

statutes and regulations (refer to Appendix L, Section 1 for more detail). The current requirement 

under the Settlement for certification by applicants that permitted activities are not unnecessarily 

duplicative is being considered in the alternatives identified in Chapter 2 (Alternative 2.2) and is 

being carried forward for analysis in the “Environmental Effects” section of Chapter 4. The panel’s

determination on evaluating the feasibility of creating standards on the lowest practicable sound 

source is presented in Appendix L as well. As above, this panel consisted of BOEM and other 

Federal Government subject matter experts, who were assisted by outside experts from industry. 

This panel also met numerous times since 2013 to identify and define key technology and 

parameters needed to appropriately determine the feasibility of creating standards to evaluate 

“lowest practicable sound sources.” The determination of the panel is that it is not feasible at this 

time to create such standards given the variability involved in using sound sources that best capture 

data sought without minimizing the quality of that data, which could lead to additional surveying

(refer to Appendix L for more detail). The panels are discussed in more detail in Chapter 1.2.3.1

below, and the full text of the panels can be found in Appendix L. 

Adaptive Monitoring Plan

A plan to monitor the potential impacts of G&G activities on marine mammals is being 

developed for BOEM’s petition to NMFS, requesting the issuance of incidental take regulations for 

operators’ G&G activities in the Gulf of Mexico. This plan is intended to develop an adaptive

monitoring program that would be implemented for the life of the rule. The plan will outline high-level 

monitoring objectives focused on understanding how and to what extent G&G activities may affect 

marine mammals in the Gulf of Mexico. The monitoring and reporting methods identified in the 
1-14 Introduction

monitoring plan will allow for an “increased knowledge of the species, the level of taking or impacts 

on populations of marine mammals that are expected to be present while conducting activities and 

suggested means of minimizing burdens by coordinating such reporting requirements with other 

schemes already applicable to persons conducting such activity” (50 CFR § 216.104(a)(13)).

Monitoring activities will include the standard monitoring and reporting measures currently 

required of regulated industry in the GOM (refer to Chapter 2 and Appendix B). Additional 

monitoring activities may include visual or acoustic observation of animals, new or ongoing research 

and data analysis, in-situ measurements of sound sources or other potential impact-producing 

factors, or any other number of activities aimed at understanding the coincidence of marine 

mammals and G&G activities in space and time, as well as the impacts that may occur from this 

overlap. The monitoring plan will be designed to be adaptively managed through a process of 

design, implementation, periodic evaluation, and revision as needed. This will involve close, 

continued coordination among regulated industry, NMFS, and BOEM. In addition to the public 

comment process associated with this Programmatic EIS, an opportunity for public input on the 

monitoring plan would occur through the process that NMFS undertakes in response to BOEM’s 

petition for rulemaking under the MMPA.

The development of the monitoring plan is ongoing. BOEM and NMFS are working 

collaboratively with the anticipated regulated parties to identify specific monitoring questions and 

activities that may be implemented during the period for which a rule would be issued. BOEM 

understands the importance of early and substantive public input in our environmental review 

processes. In early 2015, BOEM published a request for information to seek input on the 

development of the monitoring plan (79 FR 66402) and held a series of webinars to solicit 

recommendations for monitoring goals and activities for marine mammals in the Gulf of Mexico. 

This process identified ongoing and planned activities in the GOM that may serve to inform 

monitoring needs. BOEM continues to coordinate with both industry and external stakeholders to 

understand how a marine mammal monitoring and adaptive management plan in the GOM for G&G 

activities may fit into other efforts in order to prevent duplication and to address monitoring needs in 

the context of the larger GOM ecosystem. 

1.2.4 Environmental Baseline and the Deepwater Horizon Explosion, Oil Spill, 

and Response

The information included in this Programmatic EIS considers the potential changes to the 

baseline conditions of physical, biological, and economic resources that resulted from the Deepwater 

Horizon explosion, oil spill, and response (Chapter 4).

On April 20, 2010, the Deepwater Horizon offshore drilling platform, a semi-submersible 

exploratory drilling rig owned by Transocean Ltd. and leased to a BP PLC affiliate, exploded and 

subsequently sank in 4,992 ft (1,522 m) of water in the GOM, approximately 80.5 km (50 mi) off the 

coast of Louisiana. The drilling rig was in the process of temporarily abandoning an exploratory well, 

known as the Macondo well. This incident resulted in the loss of 11 lives and the release of an 
Gulf of Mexico G&G Activities Programmatic EIS 1-15

estimated 4.9 million barrels (bbl) (210 million gallons [gal]) of oil from the compromised well. In 

addition, approximately 43,810 bbl (1.84 million gal) of dispersants were applied to the waters of the 

spill area, both on the surface and at the wellhead on the seafloor (USDOC, NOAA, 2013a).

Approximately 9,000 vessels were involved over the course of the Deepwater Horizon’s oil 

spill response and cleanup. On the single most demanding day of the response, more than 

6,000 vessels, 82 helicopters, 20 fixed-wing aircraft, and more than 47,849 personnel/responders 

were employed; 229,271 square kilometers (km2

) (88,522 square miles [mi2]) of fisheries were 

closed; 168 visibly oiled wildlife were collected; 1,157 km (719 mi) of containment boom was 

deployed; 26 controlled in-situ burns were conducted, burning 59,550 bbl of oil; 291 km (181 mi) of 

shoreline were heavily to moderately oiled; 68,530 gal of dispersant were applied, and 27,097 bbl of 

oil were recovered (USDHS, CG, 2011a). For more information about Deepwater Horizon, go to 

http://response.restoration.noaa.gov/deepwater-horizon-oil-spill and http://www.deepwaterhorizon

economicsettlement.com/docs.php. 

On August 16, 2010, the CEQ issued the “Report Regarding MMS’ NEPA Policies, Practices, 

and Procedures as They Relate to OCS Oil and Gas Exploration and Development,” providing 

recommendations from review of relevant NEPA documents, consultation with agency experts, and 

review of public comments for BOEM to improve NEPA practices and procedures. Since the 

Deepwater Horizon explosion, oil spill, and response, BOEM has undertaken several in-depth 

evaluations under NEPA to assess impacts to the marine resource areas also considered in this 

Programmatic EIS. The following assessment is incorporated by reference: Gulf of Mexico OCS Oil 

and Gas Lease Sales: 2015 and 2016; Western Planning Area Lease Sales 246 and 248, Final 

Environmental Impact Statement (USDOI, BOEM, 2014a). 

The potential changes of an event such as the Deepwater Horizon explosion and oil spill to 

the baseline environmental conditions are addressed in the Chapter 4 “Affected Environment” 

discussion.

1.2.5 Exposure Versus Take of Listed Species

Model Caveats

It is important to note that BOEM and NMFS does not believe that every exposure to sound 

results in a “take” as defined in Section 101(A)(5)(A-D) of the MMPA. Therefore, exposure 

estimates used in this Programmatic EIS are not the same as a “take” or an injury to an animal. 

Where there is an overlap between noise sources and the frequencies of sound used by marine life, 

there may be concerns related to how such sound may interfere with important biological functions. 

Noise, either natural or anthropogenic, can adversely affect marine life in various ways: inducing 

alteration of behavior; reducing communication ranges or orientation capability; temporary or 

permanent damage to the auditory or other systems; and/or, in extreme cases, habitat avoidance or 

even death (e.g., Richardson et al., 1995; NRC, 2003a and 2005; Nowacek et al., 2007; Southall 

et al., 2007). BOEM expects that the majority of exposures are likely to result in only minor 

behavioral impacts, such as short-term disruption of behavioral patterns, abandonment of activities, 
1-16 Introduction

and/or temporary displacement from discrete areas rather than long-term physiological effects such 

as permanent hearing loss. From the definition above, these disruptions may qualify as “takes.” 

Noise impacts may also be additive or synergistic to those of other human stressors. While 

determining the biological significance of noise exposure impacts remains challenging (NRC, 2005), 

significant strides have been made in quantifying the effects of noise on marine mammals (USDOI, 

BOEM, 2014b).

Model Methodology

Exposure estimates presented in this Programmatic EIS were computed from modeled 

sound levels received by simulated (modeled) animals for several types of geophysical surveying. 

Animals and sources are constantly moving relative to the environment and each other. The sound 

fields generated by the sources are shaped by various physical parameters, and the sound levels 

ultimately received by an animal are a complex function of location and time. The basic modeling 

approach was to use acoustic models to compute the three-dimensional (3D) sound fields and their 

variations in time. Simulated animals (animats) were modeled moving through these fields to 

sample the sound levels in a manner similar to how real animals would experience these sounds. 

This allows a history of exposures to be built of the received sound levels of all animats. The 

number of animats exposed to levels exceeding effects threshold criteria (refer to the Chapter 4

analyses) were determined and then adjusted by the number of animals expected in the area based 

on density information (which may not be an accurate representation of the marine mammal 

population in any specific area). This creates an estimate of the potential number of animals 

exposed to the sounds. This estimate alone does not reflect BOEM’s determination of the actual 

expected physical or behavioral impacts to marine mammals but rather an overly conservative upper 

limit because none of the mitigations examined in this Programmatic EIS were modeled. Biological 

significance to marine mammals is left to interpretation by the subject-matter experts.

Model Limitations

Modeling results are inherently difficult to interpret due to the uncertainty associated with the 

data used in the model. There is a high degree of variability associated with input parameters, 

including (1) future source levels, (2) the number and exact description of the surveys to be 

conducted, (3) the exact location of survey efforts, (4) abundance and density information for marine 

mammals in the Gulf of Mexico, and (5) marine mammal behavioral responses to sound. Currently, 

the modeling produces exposure numbers based on NMFS’ acoustic criteria. These values reflect 

exposures that exceed the threshold of the current NMFS guidance (refer to Appendix D for 

detailed information).

The modeling is conservative because it did not apply any of the 19 different mitigations 

analyzed in this Programmatic EIS. These mitigations were used to minimize impacts from the 

proposed actions to the marine environment, and specifically marine mammals. The efficacy of the 

proposed mitigations finally selected for implementation as part of the Record of Decision will be 

examined under the Adaptive Monitoring Plan discussed in Chapter 1.2.3 above. Even with the 

limitations of modeling described, the model used remains the best available method for evaluating 
Gulf of Mexico G&G Activities Programmatic EIS 1-17

the exposure of marine mammals to G&G activity. As described in Chapter 1.2.7 below, a new 

methodology for building on the current modeling work and assessing predicted impacts to marine 

mammals from G&G activity is being developed. BOEM will consider this new approach in 

assessing the impacts to marine mammals from G&G activity once it becomes final.

1.2.6 NMFS’ Acoustic Guidelines

BOEM completed modeling efforts to assess the potential acoustic impacts from G&G 

activities for use in this Programmatic EIS (refer to Appendix D). These modeling efforts used the 

acoustic guidance that was available from the NMFS at that time; this guidance specified that marine 

mammals exposed to pulsed sounds with received levels exceeding 180 or 190 decibels (dB) 

referenced to 1 microPascal (root mean square) (dB re 1 μPa [rms]) are considered to exceed Level 

A (Injury) levels. The NMFS also specified at that time that cetaceans exposed to levels exceeding 

160 dB re 1 μPa (rms) are considered to exceed Level B (Behavioral Harassment) criteria.

In July 2016, NMFS released the final version of the Technical Guidance for Assessing the 

Effects of Anthropogenic Sound on Marine Mammal Hearing: Underwater Acoustic Thresholds for 

Onset of Permanent and Temporary Threshold Shifts (USDOC, NMFS, 2016a). This document 

provided acoustic guidelines (specifically those that identify the onset of Permanent Threshold Shift 

[PTS] or Temporary Threshold Shift [TTS]) to be used when conducting impact analyses for marine 

mammals. As NMFS stated in their Executive Summary, “While the Technical Guidance’s acoustic 

thresholds are more complex than those used to date in most cases by NMFS, they reflect the 

current state of the scientific knowledge regarding the characterization of sound that have the 

potential to impact marine mammal hearing sensitivity.” Throughout the development of this new 

guidance, BOEM provided comments and review.

The table below summarizes the threshold values used by this Programmatic EIS’ modelling 

and the new criteria for impulsive sources (i.e., airguns) for both energy and pressure metrics. 

Additionally, the final two columns show the difference in these threshold values. The negative 

values indicate a decrease in the threshold value, which corresponds to an increased number of 

potential impacts because a lower value implies a larger area or volume that may be exposed to the 

requisite threshold.

Modeled and New Acoustic Guideline Criteria

Functional Hearing Group

GOM Programmatic EIS 

Modeling New Criteria Difference

Energy Pressure Energy Pressure Energy Pressure

SEL

(dB re

1 μPa2·s)

peak SPL

(dB re 

1 μPa)

LE,LF,24h 

(dB re 

1 μPa2·s)

Lpk,flat 

(dB re 

1 μPa)

(dB) (dB)

Low-frequency cetaceans 192 230 183 219 -9 -11

Mid-frequency cetaceans 187 230 185 230 -2 0

High-frequency cetaceans 161 200 155 202 -6 +2
1-18 Introduction

In addition to changing threshold values, the new acoustic guidance incorporates changes to 

marine mammal hearing and weighting functions. The figure below shows the 2012 weighting 

functions (e.g., those used in the modelling for this Programmatic EIS) as dashed lines, while the 

comparable new criteria values are shown as solid lines of the same color. Note that at a first 

glance, there are differences between the values, but they do appear significant at a programmatic 

level. However, if we look specifically at how this could affect seismic operations, there is the 

potential for some fairly large differences in results from the modelling done by BOEM and the 2016 

NMFS acoustic guidance.

Comparison of the M-Weighting Curves for the 2012 Criteria and the July 2016, New Acoustic Criteria

Most of an airgun’s energy is produced in the 100- to 300-Hz frequency band, which is 

shown as the red box in the figure. The red arrow shows the difference between the two criteria for 

the 200-Hz example. The difference is about -13 dB. When this is combined with the -9 difference 

for the threshold value in the table above, it combines for a total threshold change of -22 dB for lowfrequency cetaceans exposed to airgun operations. 

For all of the other species, the combination of the threshold and the M-weighting will 

generally reduce the number of estimated Level A impacts for a given seismic operation.

The table below provides a similar analysis as above to demonstrate what the likely 

differences may be when applying the revised acoustic criteria to non-impulsive sources such as 

HRG sources.

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

-15.0

-10.0

-5.0

0.0

1 10 100 1000 10000 100000 1000000 M - Weighting (dB)

Frequency (Hz)

LF 2012

MF 2012

HF 2012

LF 2012

MF 2012

HF 2012
Gulf of Mexico G&G Activities Programmatic EIS 1-19

Modeled and New Acoustic Guideline Criteria for Non-Impulsive Sources

Functional Hearing Group

GOM Programmatic EIS 

Modeling New Criteria Difference

Energy Pressure Energy Pressure Energy Pressure

SEL 

(dB re

1 μPa2·s)

peak SPL

(dB re 

1 μPa)

LE,LF,24h 

(dB re 

1 μPa2·s)

Generally 

not 

needed 

or used

(dB) (dB)

Low-frequency cetaceans 192 230 199 - +7 N/A

Mid-frequency cetaceans 187 230 198 - +11 N/A

High-frequency cetaceans 161 200 173 - +12 N/A

N/A = not applicable.

Note: The new criteria requires the summation of energy over 24 hours, which is different from the old 

criteria which summed it for shorter periods of time and “reset” the animal to pristine condition. 

Here, even though the energy is now summed over a 24-hour period, the higher thresholds 

and M-weighting curves (for mid-frequency and high-frequency cetaceans) offset this change in the 

timeframe over which energy is summed and the number of Level A impacts for mid-frequency and 

high-frequency cetaceans remain the same or are slightly reduced overall. For low-frequency

cetaceans, however, a +7 threshold only slightly compensates for the reduced M-weighting between 

30 and 1,000 Hz (e.g., the weighting is about -16 dB between 100 and 300 Hz), and the overall 

result can be as much as -9 dB (i.e., +7-16 = -9) overall. This is equivalent to a 3-fold increase in the 

radius for non-impulsive sources in this frequency range (such as boomers) and an approximately 

10-fold (32 = 9 or about 10) increase impacts for low-frequency cetaceans overall. Most HRG 

sources, however, are primarily above 1,000 Hz. Boomer range is generally 800 Hz to 1.2 kHz, 

while chirp uses variable frequencies usually in the 160- to 200-kHz range with some portions of 

chirp sonars in the 3.5 Hz to 1,000 Hz range, possibly resulting in an increase to estimated impacts.

This is based on BOEM’s initial review of the newly published 2016 acoustic guidelines. 

BOEM intends to further review these new guidelines and work with NMFS for further clarification 

and guidance on how to apply this new information. Additionally, the modeling effort in Appendix D, 

which provides numbers estimated for incidental exposures of marine mammals, are higher than 

BOEM expects would actually occur in a real world environment. The modeling effort in 

Appendix D does not, for example, take into account any mitigation measures incorporated into the 

alternatives because the effect of those measures cannot be quantified with statistical confidence at 

this time. Further, the exposure estimates are based on acoustic and impact models that are, by 

their nature, conservative and complex. Each of the inputs into the models is purposely developed 

to be conservative, and this conservativeness accumulates throughout the analysis.

It is important to note that BOEM and NMFS do not equate every exposure to sound results 

in “take” as defined by the MMPA’s Section 101(A)(5)(A-D). Therefore, exposure estimates used in 

this Programmatic EIS are not necessarily the same as a “take” or an injury to an animal under the 

MMPA or ESA. Where there is an overlap between noise sources and the frequencies of sound 

used by marine life, there may be concerns related to how such sound may interfere with important 
1-20 Introduction

biological functions. Noise, either natural or anthropogenic, can adversely affect marine life in 

various ways: inducing alteration of behavior; reducing communication ranges or orientation 

capability; temporary or permanent damage to the auditory or other systems; and/or, in extreme 

cases, habitat avoidance or even death (e.g., Richardson et al., 1995; NRC, 2003, 2005; Nowacek 

et al., 2007; Southall et al., 2007). Noise impacts may also be additive or synergistic to those of 

other human stressors. While determining the biological significance of noise exposure impacts 

remains challenging (NRC, 2005), significant strides have been made in quantifying the effects of 

noise on marine mammals (USDOI, BOEM, 2014b). Additionally, accurate predictive modeling of 

potential acoustic impacts requires knowledge of (1) the specific source(s) that would be used at 

each site of survey operations, (2) the exact environmental acoustic conditions present at each site, 

(3) the timing and type of each survey, and (4) the marine animals present at each site. As such, the 

exposure estimates presented in this Programmatic EIS were computed from modeled sound levels 

received by simulated (modeled) animals for several types of geophysical surveying. Animals and 

sources are constantly moving relative to the environment and each other. The sound fields 

generated by the sources are shaped by various physical parameters, and the sound levels 

ultimately received by an animal are a complex function of location and time. The basic modeling 

approach was to use acoustic models to compute the 3D sound fields and their variations in time. 

Simulated animals (animats) were modeled moving through these fields to sample the sound levels 

in a manner similar to how real animals would experience these sounds. This allows a history of 

exposures to be built of the received sound levels of all animats. The numbers of animals exposed 

to levels exceeding effects threshold criteria were determined and then adjusted by the number of 

animals expected in the area, based on density information (which may not be an accurate 

representation of the marine mammal population due to the model’s assumptions). This creates an 

estimate of the potential number of animals exposed to the sounds. This estimate does not reflect 

an actual expectation that marine mammals will be injured or disturbed; it is an overly conservative 

estimate. Biological significance to marine mammals is left to interpretation by subject-matter 

experts. Using the model estimates most often requires accepting a worst-case scenario, which 

ultimately overestimates the numbers of “take” under the MMPA by equating those numbers with the 

exposures identified in the modeling rather than real world conditions.

1.2.7 Risk Assessment Framework

Throughout this chapter, where information was incomplete or unavailable, BOEM complied 

with its obligations under NEPA to determine if the information was relevant to reasonably 

foreseeable significant adverse impacts; if so, whether it was essential to a reasoned choice among 

alternatives; and, if it was essential, whether it can be obtained and whether the cost of obtaining the 

information is exorbitant, as well as whether scientifically credible information, using generally 

accepted scientific methodologies, can be applied in its place (40 CFR § 1502.22).

The most notable incomplete or unavailable information identified in this Programmatic EIS 

relates to the development of a novel analytical method to evaluate the effects of human-induced 

noise on marine mammal hearing and behavior. A research collaboration of world-leading scientists 

in underwater sound, marine mammal hearing, and marine mammal behavior recently produced an 
Gulf of Mexico G&G Activities Programmatic EIS 1-21

acoustic Risk Assessment Framework (RAF) that may help fill in this gap. In broad terms, the 

acoustic RAF considers the results of conventional assessments (e.g., exposure estimates) and, 

through a rigorous, analytical methodology, interprets what these estimates mean within the context 

of key biological and population parameters (e.g., population size, life history factors, compensatory 

ability of the species, animal behavioral state, source-animal proximity, relative motion, variance in 

density estimates, and aversion) and other biological, environmental, and anthropogenic factors. 

The end result provides not just the numbers of exposures, which is what conventional approaches 

to modeling provide, but instead what these numbers mean biologically for each affected marine 

mammal stock/population (i.e., severity of impact and vulnerability of stock/population), as well as 

the likelihood of any such impact. Traditional approaches to assessing the effects of noise on 

marine mammals involve acoustic modeling that produces estimates of exposures of marine 

mammals to potentially injurious or disturbing noise (e.g., Level A and Level B Harassment, 

respectively, under the MMPA). Agencies like BOEM are then left with interpreting (more 

qualitatively and narratively) what these numbers mean as far as biological significance to marine 

mammals. Without a rigorous methodology to do this interpretation, BOEM and other agencies must 

move forward with an overly conservative scenario equating the numbers of exposures to the 

number of “takes” under the MMPA and ESA. This often produces unrealistically high exposure/take 

numbers. In this instance, the exposure/take numbers were also modeled without the application of 

mitigation measures, adding to the unrealistically high exposure/take numbers.

The RAF analysis is expected to yield a more biologically meaningful analysis while still 

integrating current requirements and needs of U.S. regulatory agencies such as the NOAA/NMFS 

Acoustic Threshold Criteria and use of the best available science, such as the marine mammal 

density estimates produced by Duke University (Roberts et al., 2016). The RAF also integrates risk 

assessment methods used commonly by industry. While the RAF thus far currently focuses on 

airguns, it can also be adapted for other noise-producing activities and different locations.

Therefore, BOEM determined that the RAF is relevant to reasonably foreseeable significant 

adverse impacts and is essential to a reasoned choice among alternatives and, though it cannot be 

obtained in the timeframe contemplated for this Programmatic EIS, scientifically credible information 

using generally accepted scientific methodologies was applied in its place. 

Nonetheless, while the RAF data remain in development, BOEM’s subject-matter experts 

acquired and used newly available, scientifically credible information to determine exposure/take 

estimates; determined that other additional information was not available absent exorbitant 

expenditures or could not be obtained regardless of cost in timeframe contemplated by this 

Programmatic EIS and the Settlement Agreement reached with Plaintiffs and industry intervenors; 

and where gaps remained, exercised their best professional judgment to extrapolate impact 

analyses of anticipated exposure/take numbers using accepted methodologies based on credible 

information. While incomplete or unavailable information could affect the impact analyses of marine 

mammal stocks/populations in the GOM and BOEM’s decisionmaking, BOEM has determined that it 

can make an informed decision at this time without this incomplete or unavailable information. 

BOEM’s subject-matter experts have applied other scientifically credible information using accepted 
1-22 Introduction

approaches and research methods, such as that used in the Acoustic Propagation and Marine 

Mammal Exposure Modeling of Geological and Geophysical Sources in the Gulf of Mexico

conducted by JASCO Applied Sciences (refer to Appendix D).. 

1.3 REGULATORY FRAMEWORK

1.3.1 Federal Laws, Regulations, and Agreements

Federal laws, regulations, and EOs that apply to this proposed action are described in Table 

1.1-1, with additional information contained in the MMS report OCS Regulatory Framework for the 

Gulf of Mexico Region (Cameron and Matthews, 2016). The USDOI, BOEM (2014a) also outlines 

relevant legal requirements related to the proposed action. Both documents are incorporated by 

reference.

These regulations and requirements include the following:

• National Environmental Policy Act (NEPA) (42 U.S.C. §§ 4321 et seq.); 

• Outer Continental Shelf Lands Act (OCSLA) (43 U.S.C. §§ 1331 et seq., as 

amended); 

• Marine Mammal Protection Act (MMPA) (16 U.S.C. §§ 1361-1407); 

• Endangered Species Act (ESA) (16 U.S.C. § 1531); 

• Coastal Zone Management Act (CZMA) (16 U.S.C. §§ 1451 et seq.); 

• Magnuson-Stevens Fishery Conservation and Management Act (MSFCMA) 

(16 U.S.C. §§ 1801 et seq., as amended); 

• Clean Air Act (CAA) (42 U.S.C. §§ 7401 et seq., as amended); 

• Clean Water Act (CWA) (33 U.S.C. §§ 1251 et seq.); 

• Rivers and Harbors Act (RHA) (33 U.S.C. §§ 401, 403, and 407); 

• National Historic Preservation Act (NHPA) (54 U.S.C. §§ 300101 et seq.); 

• Marine Protection, Research, and Sanctuaries Act (33 U.S.C. §§ 1401 et seq.); 

• National Marine Sanctuaries Act (NMSA) (16 U.S.C. §§ 1431 et seq.); 

• Migratory Bird Treaty Act and EO 13186: Responsibilities of Federal Agencies to 

Protect Migratory Birds (16 U.S.C. §§ 703-712 and 66 FR 3853); 

• EO 12114: Environmental Effects Abroad of Major Federal Actions 

(44 FR 1957); 

• EO 12898: Federal Actions to Address Environmental Justice in Minority 

Populations and Low Income Populations (59 FR 7629); 
Gulf of Mexico G&G Activities Programmatic EIS 1-23

• EO 12989: Economy and Efficiency in Government Procurement Through 

Compliance With Certain Immigration and Naturalization Act Provisions 

(61 FR 6091); 

• EO 13089: Coral Reef Protection Act (63 FR 32701); 

• EO 13547: Stewardship of the Ocean, Our Coasts, and the Great Lakes 

(75 FR 43023); 

• EO 13158: Marine Protected Areas; 

• EO 13175: Consultation and Coordination with Indian Tribal Governments 

(65 FR 67249); 

• Marine Plastic Pollution Research and Control Act (33 U.S.C. §§ 1901 et seq.); 

• Fishermen’s Contingency Fund (50 CFR part 296); and

• Outer Continental Shelf Transboundary Hydrocarbon Agreements Authorization 

Act (H.R. 1613); 

Details of these laws and regulations are further discussed in Appendix B. 

1.3.2 State Laws, Regulations, and Agreements

While Texas, Louisiana, Mississippi, Alabama, and Florida State waters are not within the 

jurisdiction of BOEM, the AOI may encompass adjacent State waters for reasons described above in 

Chapter 1.1.3. State-issued permits may be required for activities in State waters. State regulations 

are further detailed in Appendix B. 

1.4 PROGRAMMATIC APPROACH TO THE NEPA PROCESS

BOEM has prepared this Programmatic EIS in accordance with the following (details 

provided in Appendix B):

• National Environmental Policy Act (NEPA) of 1969 (42 U.S.C. §§ 4321 et seq.);

• Council on Environmental Quality (CEQ) Regulations for Implementing the 

Procedural Provisions of NEPA (40 CFR parts 1500 through 1508);

• U.S. Department of the Interior Manual Part 516;

• USDOI Regulations implementing NEPA (43 CFR part 46);

• NOAA Administrative Order (NAO) 216-6, Environmental Review Procedures for 

Implementing NEPA (May 20, 1999); and

• EO 12114: Environmental Effects Abroad of Major Federal Actions.
1-24 Introduction

The NEPA process is designed to ensure environmental impacts of proposed major Federal 

actions are considered in the decision-making process. Federal agencies are encouraged to 

integrate the NEPA process at the earliest stage to ensure planning and decisions reflect 

environmental values, avoid delays, and address potential conflicts (40 CFR § 1501.2).

The NEPA review must fully disclose and discuss significant environmental impacts and 

inform decision-makers and the public of reasonable alternatives to the proposed Federal action. It 

also must address any adverse environmental effects that cannot be avoided or mitigated, the 

relationship between short-term uses and long-term productivity of the environment, and any 

irreversible and irretrievable commitments of resources involved in the proposed action.

In addition to compliance with NEPA, preparation of this Programmatic EIS will help ensure 

the necessary documentation and analyses to support informed decisions regarding future OCSLA 

permit and MMPA authorization actions related to G&G activities on the OCS. This Programmatic 

EIS provides information that can be used when complying with other applicable laws, including the

ESA, MSFCMA, NMSA, NHPA, and CZMA.

Given the scope and frequency of proposed G&G activities, their potential cumulative 

impacts, and the pending petition for NMFS’ incidental take regulations for the category of G&G 

activities, BOEM determined that a Programmatic EIS under NEPA is appropriate. The specific 

details (e.g., location, timing, and proposed activities to be permitted) will not be known until BOEM 

receives individual applications for permits. This Programmatic EIS provides a programmatic-level 

evaluation for reasonably foreseeable G&G activities that could be utilized for any of the three 

program areas (i.e., oil and gas, renewable energy, and marine minerals) for which BOEM has 

oversight. The most recent programmatic NEPA coverage for G&G activities in Federal waters of 

the GOM was prepared in 2004.

The analysis in this Programmatic EIS supports BOEM and the cooperating agencies 

planning level decisions for permitting G&G activities. It provides a comprehensive analysis of a 

broad range of direct, indirect, and cumulative impacts associated with G&G activities across a 

breadth of marine resource areas in addition to other past, present, and reasonably foreseeable 

projects in the area. This Programmatic EIS establishes a framework for BOEM and the cooperating 

agencies for subsequent environmental documents related to site specific actions, and identifies and 

analyzes appropriate mitigation measures to be used programmatically or considered at future sitespecific levels (tiered analysis). The USDOI Departmental Manual, Part 516, Chapter 15, provides 

guidance for implementing NEPA and lists activities that could be categorically excluded or require 

an EIS.

The scope of this Programmatic EIS does not include a NEPA analysis that evaluates a 

specific plan for oil and gas exploration or development, a specific permit or authorization for a G&G 

survey, authorization for use of marine minerals, or renewable energy leasing in the GOM, and it 

does not authorize an OCS lease sale. However, BOEM and the Cooperating Agencies will prepare 

sufficient in-depth tiered analyses, as appropriate, to authorize specific activities. Subsequent 
Gulf of Mexico G&G Activities Programmatic EIS 1-25

(tiered) analyses will be based on project-specific factors when a specific G&G activity authorization 

is requested.

The scenario analyzed in this Programmatic EIS for projected G&G activity levels extends 

over a 10-year period (Chapter 3). The 10-year period is a practical limit for making activity 

projections and does not imply that impacts on resources that have been evaluated are no longer 

valid beyond this date. All G&G activities permitted or authorized under the proposed action would 

be expected to comply with existing and future applicable laws and regulations. Compliance with 

existing and future applicable laws and regulations – by BOEM as well as individual operators and 

lessees, as required – may result in additional mitigation measures or changes to the measures 

described here.

A NEPA evaluation for approving the OCS plans that actualize leases for oil and gas 

exploration and development is not part of this proposed action.

1.5 OBJECTIVES AND SCOPE

The objectives of this Programmatic EIS are to

• characterize potential future G&G activities in the AOI over a 10-year period;

• describe the proposed action, including the purpose and need for BOEM;

• identify and analyze direct, indirect, and cumulative impacts that could result from 

the proposed action; and

• evaluate alternatives and mitigation measures that are practical and feasible to 

ensure impacts to the human environment are minimized.

A variety of G&G techniques are used to characterize the shallow and deep structure of the 

shelf, slope, and deepwater environments of the GOM. The G&G surveys are conducted to 

(1) obtain data for hydrocarbon and mineral exploration and production; (2) aid in siting of oil and 

gas structures and facilities, renewable energy structures and facilities, and pipelines; (3) locate and 

monitor use of potential sand and gravel resources for coastal restoration projects; (4) identify 

possible seafloor or shallow-depth geologic hazards; and (5) locate potential archaeological 

resources and benthic habitats that should be avoided. The selection of a specific technique or suite

of techniques is driven by data needs and the target of interest. The specific equipment used as part 

of G&G activities evaluated in this Programmatic EIS is described in Chapter 3 and detailed 

descriptions of G&G activities are provided in Chapter 3 and Appendix F. The scenario for the 

G&G activity levels projected in Chapter 3 is for a 10-year period. The G&G activities include the 

following:

• types of deep-penetration seismic (i.e., airgun) surveys used almost exclusively 

for oil and gas exploration;
1-26 Introduction

• other types of surveys and sampling activities used only in support of oil and gas 

exploration, including electromagnetic surveys, deep stratigraphic and shallow 

test drilling, and various remote-sensing methods;

• non-airgun HRG surveys used in all three program areas to detect and monitor 

geohazards, archaeological resources, and certain types of benthic communities; 

and

• geological and geotechnical bottom sampling (e.g., grab samples, vibracores) 

used in all three program areas to assess the suitability of seafloor sediments for 

supporting structures (e.g., platforms, pipelines, cables, wind turbines) or to 

evaluate the quantity and quality of sand, gravel or shell resources for beach 

nourishment and coastal restoration projects.
CHAPTER 2 

ALTERNATIVES INCLUDING THE PROPOSED ACTION

Gulf of Mexico G&G Activities Programmatic EIS 2-3 

2 ALTERNATIVES INCLUDING THE PROPOSED ACTION 

2.1 OVERVIEW

The alternatives considered in this analysis are briefly described as follows:

• Alternative A – Pre-Settlement (June 2013) Alternative; 

• Alternative B – Settlement Agreement Alternative; 

• Alternative C – Alternative A Plus Additional Mitigation Measures; 

• Alternative D – Alternative C Plus Marine Mammal Shutdowns; 

• Alternative E – Alternative C at Reduced Activity Levels; 

• Alternative F – Alternative C Plus Area Closures; and

• Alternative G – No New Activity Alternative. 

Alternatives A through F would allow BOEM to permit and/or authorize G&G activities in 

support of all BOEM program areas (i.e., oil and gas exploration and development, renewable 

energy, and marine minerals) within the AOI. Alternative G, the No New Activity Alternative, 

provides the CEQ requirement for including a No Action Alternative. The general purpose of each 

alternative evaluated is to analyze the impacts to the marine environment with each suite of 

mitigation measures proposed in each alternative. Only G&G activities directly permitted or 

authorized by BOEM, or interrelated or interconnected activities occurring in State waters and 

closely related to BOEM authorizations, are considered within the AOI. While State waters are not 

within BOEM’s jurisdiction, the AOI encompasses adjacent State waters for three reasons, which are 

described in Chapter 1.1.3. 

2.2 ADDITIONAL INFORMATION APPLICABLE TO THE ALTERNATIVES

Alternatives evaluated in this Programmatic EIS include different mitigation measures to 

provide protection of specific resources. A variety of mitigation measures have been implemented in 

the GOM to minimize environmental impacts. As defined by the CEQ, mitigation includes 

(1) avoiding an impact by not taking a certain action or parts of an action; (2) minimizing an impact 

by limiting the degree or magnitude of the action and its implementation; (3) rectifying an impact by 

repairing, rehabilitating, or restoring the affected environment; (4) reducing or eliminating an impact 

over time through preservation and maintenance operations during the life of the action; and 

(5) compensating for an impact by replacing or providing substitute resources or environments. Of 

these, BOEM’s regulated programs primarily use avoidance and minimization as the main, and most 

effective, strategies for environmental protection.

To ensure clarity in application, survey protocols and mitigation measures (as may be 

applicable to a specific program area) common to all seven alternatives (i.e., Alternatives A 

through G) are summarized in the following subsections and Table 2-1, and are detailed in 
2-4 Alternatives Including the Proposed Action

Appendix B, Section 1. Federal statutes, regulations, and Executive Orders (EOs) that apply to the 

proposed action are described in Table 1-1, Chapter 1.3.1, and Appendix B and are detailed in the 

OCS Regulatory Framework for the Gulf of Mexico Region (Cameron and Matthews, 2016). Many of 

these mitigation measures are based on existing regulations and NTLs that are available on BOEM’s 

website (http://www.boem.gov/Notices-to-Lessees-and-Operators/), that would be included as 

COAs, and that are contained in the following documents:

• “Guidance for Vessel Strike Avoidance and Injured/Dead Protected Species 

Reporting” (NTL 2016-BOEM-G01), which requires vigilant watch for marine 

mammals and sea turtles, specifies vessel speeds and required distance for 

vessels to keep away from marine mammals and sea turtles, and reporting 

requirements;

• “Guidance for Marine Trash and Debris Awareness And Elimination” (NTL 2015-

BSEE-G03), which provides information on the marine trash and debris 

awareness training video and slide show and reporting requirements (expires on 

November 30, 2018); 

• “Guidance for Avoidance of Biologically Sensitive Underwater Features and 

Areas” (NTL 2009-G39), which establish protection zones around the core of the 

Pinnacle Trend feature and prohibits any contact with the seafloor;

• “Guidance for Avoidance of Deepwater Benthic Communities” (NTL 2009-G40), 

which provides protective measures for protecting high-density deepwater 

benthic communities by requiring set-back distance for seafloor disturbing 

activities;

• “Guidance for Archaeological Resource Surveys and Reports” (NTL 2005-G07), 

which provides archaeological survey and reporting requirements; 

• “Guidance for Shallow Hazards Program” (Section VI.B of NTL 2008-G05), which 

provides the requirements for shallow hazards surveys and reporting for seafloordisturbing activities;

• “Guidance for Activities in or Near National Marine Sanctuaries” (NMSs) (15 CFR 

part 922), which provides a listing of prohibited or otherwise regulated activities 

for NMSs; and 

• “Guidance for Activities in or Near Military Warning and Water Test Areas” (NTL 

2014-BOEM-G04), which provides contact information for required coordination 

for activities within military warning areas.

Additional regulations and mitigation measures applicable to surveys performed for the Oil 

and Gas Program are detailed in Appendix B, Section 1. These measures are included in existing 

NTLs as follows:
Gulf of Mexico G&G Activities Programmatic EIS 2-5 

• “List of OCS Lease Blocks Requiring Archaeological Resource Surveys and 

Reports” (NTL 2011-JOINT-G01), which supersedes NTL 2008-G20, and 

provides additions and modifications to the list of OCS lease blocks that require 

archeological surveys and reports; 

• “Additional Shallow Hazards Guidance” (NTL 2008-G05), which provides the 

requirements for inclusion in Exploration Plans (EPs) and Development 

Operations Coordination Documents (DOCDs), requirements for shallow hazards 

surveys and reporting, and how to prepare for EP operations; and

• “Guidance for Conducting Ancillary Activities” (NTL 2009-G34), which provides 

notification requirements, follow-up reporting requirements, and review 

requirements.

BOEM does not issue permits for the acquisition of geophysical data or geotechnical 

sampling on the OCS for renewable energy development. The G&G activities for renewable energy 

activities are typically performed under a lease and the results of such surveys and testing are 

required under BOEM’s renewable energy regulations at 30 CFR part 585 for the submission of a 

Site Assessment Plan (SAP) (30 CFR § 585.610(b)), a Construction and Operations Plan (COP) 

(30 CFR § 585.626(a)), or General Activities Plan (GAP) (30 CFR § 585.645(a)). Guidelines 

applicable to G&G surveys under the Renewable Energy Program include the following:

• “Guidelines for Providing Archaeological and Historic Property Information” 

pursuant to 30 CFR part 585; and

• “Guidelines for Providing Geophysical, Geotechnical, and Geohazard 

Information” pursuant to 30 CFR part 585.

There are no additional mitigation measures applicable to surveys performed for the Marine 

Minerals Program that are not included above in the regulations and mitigation measures for G&G 

surveys.

All seismic airgun surveys in the Gulf of Mexico currently require implementation of the 

Seismic Airgun Survey Protocol (Appendix B, Attachment 1) that specifies the following mitigation 

measures, including

• an exclusion zone;

• ramp up requirements;

• visual monitoring by PSOs prior to and during seismic airgun surveys; and 

• array shutdown requirements for seismic airgun surveys performed in water 

depths >200 m (656 ft) in the CPA and WPA and for all seismic airgun surveys 

performed in the EPA. 
2-6 Alternatives Including the Proposed Action

The purpose of the Seismic Airgun Survey Protocol is to minimize the potential for injury to 

marine mammals and sea turtles and to avoid most potential for Level A harassment of marine 

mammals. The protocol specifies the conditions under which airgun arrays can be started and those 

under which they must be shut down. It also includes the recommended but optional use of PAM to 

help detect vocalizing marine mammals.

The protocol is based on NTL 2012-JOINT-G02 (“Implementation of Seismic Survey 

Mitigation Measures and Protected Species Observer Program”) and provides the requirements 

applicable to all seismic airgun surveys for all alternatives evaluated in this Programmatic EIS; 

however, additional mitigation requirements are required for the various alternatives (i.e., 

Alternatives B-F).

In addition to the NTLs and guidance noted above that is applicable to specific program 

areas, all G&G surveys will incorporate marine mammal monitoring consistent with what is outlined

in the Gulf G&G Marine Mammal Monitoring Plan Framework being developed by BOEM, NMFS, 

and the anticipated regulated parties (Chapter 1.2.3.2) and will include the ability to adjust 

compliance measures based on new information, new technologies, monitoring results, and specific 

program needs throughout the timeframe of this Programmatic EIS. A Gulf G&G Marine Mammal 

Monitoring Plan is being developed based on the requirements for an application for “take” under the 

MMPA. Monitoring requirements will be included in the Incidental Take Regulations (ITR) NMFS 

may promulgate in response to the Bureau of Ocean Management’s MMPA application. After 

issuance of ITRs, NMFS would issue individual annual Incidental Take Authorizations (ITAs) under 

Sections 101(a)(5)(A) of the MMPA for G&G surveys and ancillary activities in the form of LOAs. 

The G&G surveys conducted in support of marine mineral and renewable energy projects would 

comply separately with the ESA, MMPA, and other relevant statutes as deemed appropriate by all 

agencies. The NTLs and COAs may be modified or revised with new baseline mitigation measures 

and applicable terms and conditions of any and future ESA Section 7 consultations, MMPA, and 

other regulatory requirements.

Summarized characterizations of each alternative are provided in the following subsections 

and are detailed in Appendix B, Section 1. Additionally, Tables 2-1 and 2-2 provide a comparison 

summary of the mitigation measures for each alternative.

Exposure Versus Take of Listed Species

It is important to note that BOEM and NMFS do not equate every exposure to sound by a 

listed species or marine mammal as a “take” as defined in Section 101(A)(5)(A-D) of the MMPA or 

under the ESA. Using the model estimates most often requires assuming an extremely conservative 

or maximum case scenario, which ultimately may overestimate exposures. For a full discussion of 

the model methodology and limitations, refer to Chapter 1.2.3, “Exposure Versus Take of Listed 

Species.” 
Gulf of Mexico G&G Activities Programmatic EIS 2-7 

2.3 ALTERNATIVE A – PRE-SETTLEMENT (JUNE 2013) ALTERNATIVE

2.3.1 Description

Under Alternative A, BOEM would continue to permit or authorize G&G activities at the 

current projected activity levels with implementation of standard (pre-settlement) mitigation 

measures applied to those activities through lease stipulations, permits and authorizations, typically 

as COAs. Currently, BOEM implements seismic survey mitigation measures for marine mammals 

and sea turtles in the GOM through terms and conditions and conservation recommendations of 

biological opinions developed for lease sales.

2.3.2 Mitigation Measures

All G&G survey activities supporting the oil and gas, renewable energy, and marine minerals 

programs permitted or authorized under Alternative A would be required to comply with all statutes, 

regulations, lease stipulations, and mitigation measures identified above and detailed in 

Appendix B, Section 1. The mitigation measures included in Alternative A are the measures that 

were in place prior to the Settlement Agreement (refer to Appendix C). This alternative includes no 

newly proposed mitigation measures since the Settlement Agreement, and the measures listed 

below are italicized within the subsequent alternative descriptions to distinguish them from newly 

proposed measures. Mitigation measures described include guidance in NTLs and requirements 

promulgated through regulations (oil and gas program surveys only), which are adopted as COAs or 

stipulations in permits, plans, or other authorizations. For NMFS’ purpose, these measures would 

be considered for inclusion in ITRs and/or IHAs issued under the MMPA.

The standard mitigations implemented for Alternative A are presented in Tables 2-1 and 2-2, 

are detailed in Appendix B, Section 1, and include the following: 

• guidance for vessel strike avoidance;

• guidance for marine debris awareness;

• avoidance of sensitive benthic resources;

• guidance for avoidance of historic and prehistoric sites;

• guidance for shallow hazards survey and reporting;

• guidance for activities in or near national marine sanctuaries (NMSs); 

• guidance for military coordination;

• guidance for ancillary activities (Oil and Gas Program only) ; and

• implementation of the Seismic Airgun Survey Protocol: PSO and PAM Programs 

(refer to Tables 2-1 and 2-2 for PSO and PAM details that apply to each 

alternative).
2-8 Alternatives Including the Proposed Action

2.3.3 Rationale

The use of acoustic sources while conducting G&G operations may have an impact on 

marine wildlife, including marine mammals and sea turtles. Some marine mammals, such as the 

sperm whale (Physeter macrocephalus), and all sea turtles that inhabit the GOM are protected under 

the ESA, while all marine mammals are protected under the MMPA. The purpose of the operational 

measures included in Alternative A is to minimize the potential for injury to marine mammals and sea 

turtles.

This alternative examines the impacts to the environment from G&G survey operations 

performed implementing the mitigation measures that had been used in the GOM prior to the 

Settlement Agreement. The implementation of the Seismic Airgun Survey Protocol affords 

protection for marine mammals by reducing Level A exposures in deep water.

2.4 ALTERNATIVE B – SETTLEMENT AGREEMENT ALTERNATIVE 

2.4.1 Description

Under Alternative B (Settlement Agreement Alternative), G&G activities would include 

implementation of mitigation, monitoring, and reporting as well as mitigation measure requirements 

outlined in the Settlement Agreement for Civil Action No. 2:10 cv-01882 dated June 25, 2013, as 

discussed in Chapter 1.2.3 and as provided in Appendix C. Under Alternative B, BOEM would 

continue to permit or authorize G&G activities through the use of site-specific NEPA evaluations, 

lease stipulations, NTLs, best management practices, and COAs as provided in the Settlement 

Agreement. Under this alternative, Settlement Agreement requirements (as of November 2015)1

, 

existing NTLs, COAs, and best management practices -- including required mitigation, monitoring, 

and reporting -- would remain in effect.

The Settlement Agreement puts in place interim mitigation measures, which are analyzed 

under this alternative. While the stay (temporary suspension of the judicial proceedings) is in effect, 

BOEM has agreed to analyze the interim mitigation measures listed in Chapter 2.4.2 as potential 

COAs for permits or authorizations to conduct deep penetration seismic airgun surveys. Analyzing 

these interim mitigation measures does not obligate BOEM to require them as part of a resulting 

 

1 The Settlement Agreement was by its original terms to expire in December 2015. On February 10, 

2016, the parties formally agreed to extend the terms of the Settlement Agreement until September 25, 

2017. In addition, the extended Settlement Agreement amended Article V of the agreement to include 

additional mitigation measures. However, the additional mitigation measures do not modify the impact 

conclusions in this Draft Programmatic EIS. Because the terms of the Settlement Agreement were 

modified after the analysis for this Draft Programmatic EIS was performed, and their future inclusion will 

not adversely modify the impact determinations in this document, BOEM has decided to modify this 

alternative at the Final Programmatic EIS stage rather than in this Draft Programmatic EIS to reflect the 

expansion of mitigation measures in Article V of the Settlement and any resulting analysis.
Gulf of Mexico G&G Activities Programmatic EIS 2-9 

permit or authorization. However, BOEM is typically implementing these measures as COAs in 

permits and authorizations.

The Settlement Agreement upon which Alternative B is based is a temporary and voluntary 

agreement between the parties performing and regulating G&G activities in the GOM and not a G&G 

regulatory framework adopted by BOEM. Under Alternative B, the temporary provisions of the 

Settlement Agreement, as described below, may be formally adopted into the process BOEM uses 

for issuing future G&G permits. For NMFS’ purpose as a cooperating agency, these measures 

would be considered for inclusion in incidental take regulations issued under the MMPA.

2.4.2 Mitigation Measures

The G&G surveys permitted or authorized under Alternative B would be required to comply 

with the interim mitigation measures outlined in the Settlement Agreement (Appendix C). 

Alternative B consists of all mitigation measures, with the exception of guidance for ancillary 

activities, that were in place prior to the Settlement Agreement (included in Alternative A, Chapter 

2.3 and which are in italics below), as well as the newly proposed mitigation measures. All 

mitigation measures required for Alternative B are included in Chapter 1.2.3, presented in Tables 

2-1 and 2-2, detailed in Appendix B, Section 1, and include the following: 

• guidance for vessel strike avoidance;

• guidance for marine debris awareness;

• avoidance of sensitive benthic resources;

• guidance for avoidance of historic and prehistoric sites; 

• guidance for shallow hazards survey and reporting;

• guidance for activities in or near NMSs; 

• guidance for military coordination;

• implementation of the Seismic Airgun Survey Protocol: PSO and PAM Programs 

(refer to Tables 2-1 and 2-2 for PSO and PAM details that apply to each 

alternative);

− implementation of the expanded PSO Program: expanded to include 

manatees as well as whales and would also apply to all authorizations for 

deep-penetration seismic airgun surveys in the AOI regardless of water 

depth; and 

− implementation of the expanded PAM requirement: the required use of PAM 

for all deep-penetration seismic airgun surveys in water depths >100 m 

(328 ft);
2-10 Alternatives Including the Proposed Action

• implementation of a minimum separation distance between simultaneous deeppenetration seismic airgun surveys when operating in the designated Areas of 

Concern identified by Plaintiffs in the Settlement (Figure 2.2-1);

• coastal waters’ seasonal restrictions from January 1 to April 30 (Figure 2.2-1);

and

• restriction of deep-penetration seismic airgun surveys in the Areas of Concern 

within the EPA (Figure 2.2-1).

In addition to the mitigation measures above, the following requirements for reporting and 

information that are not included in the Seismic Airgun Survey Protocol (Appendix B, 

Attachment 1) would be included in all permits or authorizations under Alternative B:

• Reporting Requirements – Operators shall provide biweekly reports on the 

seismic survey and confirm compliance with required mitigation measures.

• Application Requirements – For confirmation of survey non-duplicity and use of 

the lowest practicable sound source, the applicant must provide

− written justification explaining why the proposed deep-penetration seismic 

airgun survey is not unnecessarily duplicative of previously conducted 

surveys; and

− an estimate of total energy output per impulse in decibels (rms) with respect 

to each energy source to be used and verify in writing that the airgun arrays, 

to the furthest extent practicable, use the lowest sound intensity level that still 

achieves the survey’s goals.

2.4.3 Rationale

The Settlement Agreement (refer to Appendix C) requires BOEM to evaluate the 

agreement’s mitigation measures in this Programmatic EIS. These mitigation measures are 

intended to reduce cumulative or chronic exposures of marine mammal populations to noise (e.g., 

limiting concurrent surveying and limiting the total amount of survey activity in portions of the GOM).

The interim mitigation measures included in the Settlement Agreement go beyond those 

mitigation measures included in Alternative A and afford additional protection for all marine 

mammals, with some mitigation measures focused on protection of specific species. These 

mitigation measures include the expansion of the PSO Program and the required use of PAM for all 

surveys performed in water depths >100 m (328 ft) during time of reduced visibility, which provides 

additional protection for marine mammals, including manatees, to reduce Level A exposures.

The Settlement Agreement includes four geographic “Areas of Concern” to Plaintiffs (Figure 

2.2-1). Within these areas, the agreement establishes mitigation measures including seasonal 

restrictions (refer to Area of Concern 3); closures for all deep-penetration seismic airgun surveys 
Gulf of Mexico G&G Activities Programmatic EIS 2-11

(portions of Areas of Concern 2, 3 and 4) located in the EPA; and a minimum separation distance 

between simultaneous deep-penetration seismic airgun surveys when operating in any Area of 

Concern.

2.5 ALTERNATIVE C – ALTERNATIVE A PLUS ADDITIONAL MITIGATION MEASURES

2.5.1 Description

Under Alternative C, G&G activities would continue to be authorized and would include the 

mitigation measures, monitoring, reporting, survey protocols, and guidance that were in place prior 

to the Settlement Agreement (included in Alternative A, Chapter 2.3 and which are in italics below), 

as well as additional mitigation and temporal measures for survey protocols for seismic airgun and 

non-airgun HRG surveys. A Gulf G&G Marine Mammal Monitoring Plan is being developed by 

BOEM (Chapter 1.2.3.2) and would allow for adaptive management of mitigation measures for all 

three programs (i.e., oil and gas, renewable energy, and marine minerals) if warranted by new 

information, new technologies, monitoring results, and specific program needs throughout the 

timeframe of this Programmatic EIS.

2.5.2 Mitigation Measures

The G&G surveys permitted or authorized under Alternative C would be required to comply 

with all the mitigation measures included in Alternative A plus additional measures as described 

below. The mitigation measures required for Alternative C are presented in Tables 2-1 and 2-2,

detailed in Appendix B, Section 1, and include the following:

• guidance for vessel strike avoidance;

• guidance for marine debris awareness;

• avoidance of sensitive benthic resources;

• guidance for avoidance of historic and prehistoric sites; 

• guidance for shallow hazards survey and reporting;

• guidance for activities in or near NMSs; 

• guidance for military coordination;

• guidance for ancillary activities (Oil and Gas Program only);

• implementation of the Seismic Airgun Survey Protocol: PSO and PAM Programs 

(refer to Tables 2-1 and 2-2 for PSO and PAM details that apply to each 

alternative):

− implementation of expanded PSO Program: expanded to include manatees 

as well as whales and would also apply to all authorizations for deeppenetration seismic airgun surveys in the AOI regardless of water depth;
2-12 Alternatives Including the Proposed Action

− implementation of expanded PAM requirement: the required use of PAM for 

all deep-penetration seismic airgun surveys in water depths >100 m (328 ft); 

and

− implementation of expanded PAM requirement: the required use of PAM for 

all deep-penetration seismic airgun surveys at all times in the Mississippi 

Canyon and De Soto Canyon lease blocks (Figure 2.3-1);

• implementation of the Non-Airgun HRG Survey Protocol; and 

• coastal waters’ seasonal restrictions from February 1 to May 31, expanded from 

Alternative B (Figure 2.3-1).

2.5.3 Rationale

The purpose of the mitigation measures included in Alternative C is to further minimize the 

potential for injury to marine mammals and sea turtles, to avoid most potential for Level A 

harassment of marine mammals, and to provide additional protection for coastal stocks of bottlenose 

dolphins. This alternative was developed based on the Alternative A mitigation measures. 

However, in Alternative C, the seasonal restrictions for coastal waters were expanded for additional 

protection of reproducing dolphins and requirements to use PAM in the Mississippi Canyon and 

De Soto Canyon blocks were included. Although there is no fixed reproductive season for 

bottlenose dolphins in the GOM, there does appear to be a peak in calf and neonate strandings 

falling within the boundaries of the UME in the northern Gulf of Mexico from February to May (now 

closed and determined by NMFS to be largely unrelated to seismic activities); therefore, the 

restriction was extended to incorporate this timeframe. In addition, the inclusion of the expanded 

PSO Program for all surveys performed in water depths >100 m (328 ft) and for all deep-penetration 

seismic airgun surveys performed in the Mississippi Canyon and De Soto Canyon lease blocks 

provides additional protection for marine mammals, including manatees, to reduce the potential for 

Level A exposures.

In addition, the implementation of the Non-Airgun HRG Survey Protocol further reduces 

exposure of marine mammals to acoustic sources that fall within their hearing range (<200 kilohertz

[kHz]) resulting in further reductions in Level A exposures to marine mammals.

Unlike Alternative B, the minimum separation distances and restrictions in the EPA were not 

carried forward to Alternative C.

2.6 ALTERNATIVE D – ALTERNATIVE C PLUS MARINE MAMMAL SHUTDOWNS

2.6.1 Description

Under Alternative D, G&G activities would continue to be authorized and would include the 

mitigation measures, monitoring, reporting, survey protocols, and guidance that are included in 

Alternative C (Chapter 2.5) as well as additional mitigation and temporal measures for survey 
Gulf of Mexico G&G Activities Programmatic EIS 2-13

protocols for airgun and HRG surveys and the development of the Gulf G&G Marine Mammal 

Monitoring Plan Framework.

2.6.2 Mitigation Measures

The G&G surveys permitted or authorized under Alternative D would be required to comply 

with all the mitigation measures included in Alternative C (Chapter 2.5), which are the mitigation 

measures, monitoring, reporting, survey protocols, and guidance that were in place prior to the 

Settlement Agreement (included in Alternative A Chapter 2.3 and which are in italics below), as well 

as additional mitigation and temporal measures for survey protocols for seismic airgun and 

non-airgun HRG surveys, and an additional measure that expands the PSO shutdown to include all 

marine mammals except animals that actively approach the vessel to bow ride. In the GOM, bowriding dolphin species include the bottlenose, Fraser’s, Clymene’s, rough-toothed, striped, spinner, 

Atlantic spotted, pantropical, and Risso’s dolphins. The mitigation measures required for 

Alternative D are presented in Tables 2-1 and 2-2, detailed in Appendix B, Section 1, and include 

the following:

• guidance for vessel strike avoidance;

• guidance for marine debris awareness;

• avoidance of sensitive benthic resources;

• guidance for avoidance of historic and prehistoric sites; 

• guidance for shallow hazards survey and reporting;

• guidance for activities in or near NMSs; 

• guidance for military coordination;

• guidance for ancillary activities (Oil and Gas Program only);

• implementation of the Seismic Airgun Survey Protocol: PSO and PAM Programs 

(refer to Tables 2-1 and 2-2 for PSO and PAM details that apply to each 

alternative):

− implementation of the expanded PSO Program and includes shutdown for all 

marine mammals with the exception of bow-riding dolphins (i.e., bottlenose, 

Fraser’s, Clymene’s, rough-toothed, striped, spinner, Atlantic spotted, 

pantropical, and Risso’s dolphins) and would also apply to all authorizations 

for deep-penetration seismic airgun surveys in the AOI regardless of water 

depth;

− implementation of expanded PAM requirement: the required use of PAM for 

all deep-penetration seismic airgun surveys in water depths >100 m (328 ft); 

and
2-14 Alternatives Including the Proposed Action

− implementation of expanded PAM requirement: the required use of PAM for 

all deep-penetration seismic airgun surveys at all times in the Mississippi 

Canyon and De Soto Canyon lease blocks (Figure 2.3-1);

• implementation of the Non-Airgun HRG Survey Protocol; and 

• coastal waters’ seasonal restrictions from February 1 to May 31, expanded from 

Alternative B (Figure 2.3-1).

2.6.3 Rationale

The purpose of the mitigation measures included in Alternative D is to further minimize the 

potential for injury to marine mammals and sea turtles, to avoid most Level A harassment of marine 

mammals, and to provide additional protection for marine mammals. This alternative was developed 

based on the Alternative C mitigation measures, but includes additional protection for all marine 

mammals species – including manatees, but not bow-riding dolphins (bottlenose, Fraser’s, 

Clymene’s, rough-toothed, striped, spinner, Atlantic spotted, pantropical, and Risso’s) – with the 

inclusion of the expansion of the PSO Program to avoid most potential Level A exposures to marine 

mammals in all water depths.

2.7 ALTERNATIVE E – ALTERNATIVE C AT REDUCED ACTIVITY LEVELS

2.7.1 Description

Under Alternative E, G&G activities would continue to be authorized with the mitigation 

measures described for Alternative C, including the development of the Gulf G&G Marine Mammal 

Monitoring Plan Framework. However, BOEM would require a reduced level of activity (calculated in 

line miles) for deep-penetration, multi-client seismic airgun surveys. Projected scenarios for oil and 

gas exploration seismic airgun survey levels are discussed in Chapter 3.2. Alternative E has two 

proposed reduction options in seismic airgun survey activities: (1) a 10-percent reduction proposed 

in Alternative E1 (Table 2.5-1); and (2) a 25-percent reduction (Table 2.5-2) for Alternative E2. 

These reductions in seismic surveys were identified for evaluation as these reductions have the 

potential to noticeably reduce impacts and/or exposures to marine species and the overall acoustic 

sounds in the Gulf. Activities could be conducted in any of the OCS planning areas.

2.7.2 Mitigation Measures

The G&G surveys permitted or authorized under Alternative E would be required to comply 

with all of the mitigation measures included in Alternative C (Chapter 2.5), which are the mitigation 

measures, monitoring, reporting, survey protocols, and guidance that were in place prior to the

Settlement Agreement (included in Alternative A, Chapter 2.3 and which are in italics below), as well 

as additional mitigation and temporal measures for survey protocols for seismic airgun and 

non-airgun HRG surveys. The required mitigation measures for Alternative E are presented in 

Tables 2-1 and 2-2, detailed in Appendix B, Section 1, and include the following:
Gulf of Mexico G&G Activities Programmatic EIS 2-15

• guidance for vessel strike avoidance;

• guidance for marine debris awareness;

• avoidance of sensitive benthic resources;

• guidance for avoidance of historic and prehistoric sites; 

• guidance for shallow hazards survey and reporting;

• guidance for activities in or near NMSs; 

• guidance for military coordination;

• guidance for ancillary activities (Oil and Gas Program only);

• implementation of the Seismic Airgun Survey Protocol: PSO and PAM Programs 

(refer to Tables 2-1 and 2-2 for PSO and PAM details that apply to each 

alternative):

− implementation of expanded PSO Program: expanded to include manatees 

as well as whales and would also apply to all authorizations for deeppenetration seismic airgun surveys in the AOI regardless of water depth;

− implementation of expanded PAM requirement: the required use of PAM for 

all deep-penetration seismic airgun surveys in water depths >100 m (328 ft); 

− implementation of expanded PAM requirement: the required use of PAM for 

all deep-penetration seismic airgun surveys at all times in the Mississippi 

Canyon and De Soto Canyon lease blocks (Figure 2.3-1);

• implementation of the Non-Airgun HRG Survey Protocol; and 

• coastal waters’ seasonal restrictions from February 1 to May 31, expanded from 

Alternative B (Figure 2.3-1).

Under Alternative E, all mitigation measures described above (same as Alternative C) would 

apply, however, but with a reduced level of activity. Alternative E contains two options:

• Alternative E1 – A reduction (in line miles) of deep-penetration, multi-client 

seismic activities by 10 percent from the estimated levels in a calendar year 

(Table 2.5-1); and

• Alternative E2 – A reduction (in line miles) of deep-penetration, multi-client 

seismic activities by 25 percent from the estimated levels in a calendar year 

(Table 2.5-2).
2-16 Alternatives Including the Proposed Action

2.7.3 Rationale

This alternative is based on Alternative C with the addition of a reduction in the level of 

seismic airgun survey activities. The purpose of the mitigation measures included in Alternative E is 

to minimize the potential for injury to marine mammals and sea turtles, to avoid most potential for 

Level A harassment of marine mammals, and provide additional protection for marine mammals. 

This alternative provides additional protection to these resources and other resources in the GOM by 

reducing the level of deep-penetration seismic airgun surveys by 10 or 25 percent. 

2.8 ALTERNATIVE F – ALTERNATIVE C PLUS AREA CLOSURES

2.8.1 Description

Under Alternative F, G&G activities would continue to be authorized and would include the 

mitigation measures, monitoring, reporting, survey protocols, and guidance that are included in 

Alternative C (Chapter 2.5), which are the mitigation measures, monitoring, reporting, survey 

protocols, and guidance that were in place prior to the Settlement Agreement (included in Alternative 

A, Chapter 2.3 and which are in italics below), as well as additional mitigation and temporal 

measures for survey protocols for seismic airgun and non-airgun HRG surveys, plus the addition of 

area closures for all seismic airgun surveys at all times in four deepwater areas to provide additional 

protection for certain cetacean species and other resources. These area closures include the CPA 

Closure Area, the EPA Closure Area, the Dry Tortugas Closure Area, and the Flower Gardens 

Closure Area, as shown in Figure 2.6-1. All of the closure areas or a subset of the closures areas 

could be selected as part of this alternative.

2.8.2 Mitigation Measures

Under Alternative F, currently authorized G&G activities in the closure areas would be 

allowed to continue subject to the terms and conditions of existing permits or authorizations and 

without being required to implement additional mitigation measures. All new G&G surveys permitted 

or authorized under Alternative F would be required to comply with all the mitigation measures 

included in Alternative C plus the additional closure areas described above. In addition, airgun 

surveys conducted outside of the closure areas would be required to remain at a distance such that 

received sound levels at the closed area boundaries would not exceed the threshold for Level B 

harassment (currently 160 decibels (dB) [relative to 1 micropascal [dB re 1 μPa]), as determined by 

field verification of sound levels or sound field modeling. Also, these areas would be closed to all 

G&G activities except non-airgun HRG surveys in which one or more active acoustic sound sources 

would be operating at frequencies >200 kHz. The mitigation measures required for Alternative F are 

presented in Tables 2-1 and 2-2, detailed in Appendix B, Section 1, and include the following:

• guidance for vessel strike avoidance;

• guidance for marine debris awareness; 

• avoidance of sensitive benthic resources;
Gulf of Mexico G&G Activities Programmatic EIS 2-17

• guidance for avoidance of historic and prehistoric sites; 

• guidance for shallow hazards survey and reporting;

• guidance for activities in or near NMSs; 

• guidance for military coordination;

• guidance for ancillary activities (Oil and Gas Program only);

• implementation of the Seismic Airgun Survey Protocol: PSO and PAM Programs 

(refer to Table 2-1 and 2-2 for PSO and PAM details that apply to each 

alternative):

− implementation of expanded PSO Program;

− the required use of PAM for all deep-penetration seismic airgun surveys in 

water depths >100 m (328 ft); and

− the required use of PAM for all deep-penetration seismic airgun surveys at all 

times in the Mississippi Canyon and De Soto Canyon lease blocks (Figure 

2.3-1);

• implementation of the Non-Airgun HRG Survey Protocol;

• coastal waters’ seasonal restrictions from February 1 to May 31, expanded from 

Alternative B (Figure 2.3-1);

• no new seismic airgun and non-airgun HRG surveys in the CPA, EPA, Dry 

Tortugas, and Flower Garden Banks closure areas (Figure 2.6-1); and

• airgun surveys conducted outside of the closure areas would be required to 

remain at a distance such that received sound levels at the closed area 

boundaries would not exceed the threshold for Level B harassment (currently 

160 dB [relative to 1 micropascal [dB re 1 μPa]), as determined by field 

verification of sound levels or sound field modeling.

2.8.3 Rationale

The purpose of the mitigation measures included in Alternative F is to further minimize the 

potential for injury to marine mammals and sea turtles, to avoid most potential for Level A 

harassment of marine mammals, and to provide additional protection for specific target species of 

marine mammals. Selection of these closure areas was determined based on densities of target 

species relative to other areas of the AOI, as well as biological importance to certain species, 

including the endangered sperm whale (Physeter macrocephalus), Bryde’s whale (Balaenoptera 

edeni) (LaBrecque et al., 2015), beaked whales, and additional marine resources found within the 

closure areas.
2-18 Alternatives Including the Proposed Action

The CPA Closure Area targets sperm whales and beaked whales for protection. The CPA 

Closure Area has been expanded from the Settlement Agreement Area of Concern 1 (Figure 2.2-1) 

based on sighting data. The CPA Closure Area supports relatively high densities of sperm whales 

and beaked whales. Based on satellite tracking studies conducted by Jochens et al. (2008), the 

home range of tagged sperm whales within the northern GOM is broad, comprising nearly the entire 

GOM in waters deeper than 500 m (1,640 ft). Home range is defined as an area over which an 

animal or group of animals regularly travels in search of food or mates and that may overlap with 

those of neighboring animals or groups of the same species. By contrast, the composite core area

(defined as a section of the home range that is utilized more thoroughly and frequently as primary 

locales for activities such as feeding) of GOM sperm whales generally includes the Mississippi 

Canyon, Mississippi River Delta, and, to a lesser extent, the Rio Grande Slope (Jochens et al., 

2008). These data support the fact that sperm whales aggregate in the Mississippi Canyon area, 

including the proposed closure area, but regularly move across the northern GOM continental slope. 

Movements or seasonal migrations of beaked whales are not known, though it is likely that their 

distributional patterns depend on the movement of mesoscale hydrographic features (USDOC, 

NOAA, 2015a).

The EPA Closure Area was designed to protect cetaceans, primarily targeting the Bryde’s 

whale given the small population size and apparent preference for this area. Bryde’s whales that 

inhabit the northern GOM may represent a resident stock and, based on sightings data from surveys 

that uniformly sampled the entire oceanic northern GOM, mostly occur in a very restricted area of 

the northeastern GOM between the 100- and 400-m (328- and 1,312-ft) isobaths. The EPA Closure 

Area was refined from the Area of Concern 2 from the Settlement Agreement (Figure 2.2-1) to 

partially correspond with the year-round Biologically Important Area (BIA) for this population in the 

GOM (LaBrecque et al., 2015) but was expanded to the 400-m (1,312-ft) contour north of 27.5o N. 

latitude to incorporate additional Bryde’s whale sightings.

The Dry Tortugas Closure Area targets sperm and beaked whales and has been expanded 

from the Settlement Agreement Area of Concern 4 (Figure 2.2-1) based on sighting data. This 

Closure Area includes waters bounded by the 200- and 2,000-m (656- and 6,562-ft) isobaths (or 

U.S. EEZ) from the northern border of BOEM’s Howell Hook leasing area to 81.5° W. longitude. 

Acoustic data suggest that beaked whale densities are high in this area (Hildebrand et al., 2012).

The Flower Gardens Closure Area was designed to protect the marine resources found 

within the Flower Garden Banks National Marine Sanctuary (FGBNMS), such as various species of 

stony corals, sponges, anemones, jellies, bony fishes, rays, sharks, sea turtles, birds, and marine 

mammals. The FGBNMS is one of 14 federally designated underwater areas protected by NOAA’s 

Office of National Marine Sanctuaries.
Gulf of Mexico G&G Activities Programmatic EIS 2-19

2.9 ALTERNATIVE G – NO NEW ACTIVITY ALTERNATIVE

2.9.1 Description

Under BOEM’s Alternative G (no new activity), BOEM would cease issuing permits for new 

G&G surveys and would not approve G&G surveys proposed under exploration or development 

plans. G&G activities previously authorized under an existing permit or lease would proceed but 

would not be renewed or reauthorized and, thus, would eventually be phased out. Chapter 3.2 and 

Appendix F provide descriptions of the different types of G&G surveys. Table 2.7-1 provides the 

projected level of activity these surveys would represent. All previously authorized surveys would be 

completed with the implementation of standard mitigation measures applied through lease 

stipulations, COAs, NTLs, or best management practices applied to all authorizations.

This BOEM alternative also stipulates that no new on-lease G&G activities related to 

renewable energy development could be conducted, which would limit the development of 

renewable energy sources. Under this BOEM alternative, no new G&G activities related to marine 

minerals would be authorized by BOEM for survey activities located in Federal waters that require 

BOEM authorization. However, surveys for marine minerals in Federal waters that would not require 

BOEM authorizations, such as those conducted by Federal agencies or their contractors to identify 

sand, gravel, or shell resources, or those in State waters, could still go forward. The G&G activities 

that are not regulated by BOEM would still take place in the GOM (e.g., non-airgun HRG surveys for 

archeological and benthic resources and off-lease G&G activities for renewable energy). Survey 

activity for scientific research that is not regulated by BOEM (such as those conducted by the USGS, 

National Science Foundation [NSF], NOAA, and academia), and surveys occurring in State waters, 

could continue as well.

BOEM’s Alternative G would not meet the purpose and need of the proposed action nor 

would it implement the natural resource development provisions of OCSLA. 

This alternative also has safety and consequently development implications for oil and gas, 

renewable energy, and marine mineral activities. While G&G activities would continue for existing 

authorized permits or approvals, no new activities would be permitted or authorized. Oil and gas 

leasing and future operations require G&G activities in order to evaluate potential reservoirs and to 

conduct operations in a safe and secure manner. For example, placement of a permanent platform 

requires a shallow hazards survey and geological sampling (coring) to ensure that the proposed 

location is free of potential hazards and to determine the geotechnical properties of the substrate to 

assess the substrate stability for placement and anchoring. Under BOEM’s No Activity Alternative, 

these activities could not take place for future leases, infrastructure and other related activities may 

not be as safely constructed or implemented, and development could be suspended in 

consequence.

The No Action Alternative for NMFS is slightly different. For NMFS, denial of MMPA 

authorizations (either as LOAs issued under ITRs or as IHAs) constitutes NMFS’ No Action 

Alternative, which is consistent with NMFS’ statutory obligation under the MMPA to grant or deny 
2-20 Alternatives Including the Proposed Action

applications to authorize incidental take and to prescribe mitigation, monitoring and reporting with 

any authorizations. This NMFS No Action Alternative presents two potential outcomes. One is that 

the G&G activities will occur in the absence of an MMPA authorization. In this case, (1) the entity 

conducting the activity would be in violation of the MMPA if takes occur; (2) mitigation, monitoring, 

and reporting would not be prescribed by NMFS; and (3) mitigation might not be performed 

voluntarily by the operators. If the G&G activity were conducted under a lease or permit issued by 

BOEM, the activity would have to conform to mitigation and monitoring measures as specified in 

applicable lease and lease stipulations, COAs on permit and plans, and best management practices. 

These measures would not obviate the MMPA requirement that any incidental take be authorized by 

NMFS (or FWS), for species under FWS jurisdiction) and that any unauthorized take would be a 

violation of the MMPA. However this scenario assumes that some operators will move forward with 

survey activity, assuming the risk and consequences of potential unauthorized take, and in this case, 

the impacts to the environment would be the same as those analyzed in Alternatives A through F of 

this Programmatic EIS.

The second potential outcome of NMFS’ No Action Alternative assumes that BOEM would 

not issue any new permits or approvals for G&G activities and that these activities would cease or be 

phased out with completion of activity under existing authorizations. This Programmatic EIS 

assumes for this analysis that, as would be the case under this second outcome, no new activities 

would occur under NMFS’ No Action Alternative. The discussion of this outcome scenario is 

consistent with the analysis of BOEM’s No New Activity Alternative.

2.9.2 Mitigation Measures

Under Alternative G, existing permitted or authorized G&G surveys would be required to 

comply, at minimum, with all the mitigation measures included in Alternative A. These mitigation 

measures are presented in Tables 2-1 and 2-2, detailed in Appendix B, Section 1, and include the 

following: 

• guidance for vessel strike avoidance;

• guidance for marine debris awareness;

• avoidance of sensitive benthic resources;

• guidance for avoidance of historic and prehistoric sites;

• guidance for shallow hazards survey and reporting;

• guidance for activities in or near NMSs; 

• guidance for military coordination;

• guidance for ancillary activities (Oil and Gas Program only);

• implementation of a PSO program; and

• implementation of the Seismic Airgun Survey Protocol.
Gulf of Mexico G&G Activities Programmatic EIS 2-21

2.9.3 Rationale

Section 1502.14(d) of CEQ requires the alternatives analysis in an EIS to "include the 

alternative of no action." Alternative G fulfills this requirement and evaluates the impacts from 

BOEM ceasing to issue permits or authorizations for all G&G surveys that may require a permit from 

BOEM. However, previously authorized activities and those not requiring an additional approval 

from BOEM would continue, but industry would still be subject to the risks and consequences of 

engaging in activities that result in the incidental take of marine mammals without an authorization 

from NMFS. 

2.10 ISSUES

Issues are defined by the CEQ to represent the principal “effects” that an EIS should 

evaluate in-depth. Scoping identifies specific environmental resources and activities, rather than 

“causes,” as significant issues for development in the EIS. The analysis in the EIS can then show 

the degree of change from present conditions for each issue due to the relevant actions related to 

the proposed action. Selection of environmental and socioeconomic issues to be analyzed in this 

Programmatic EIS was based on the following criteria:

• the issue is identified in CEQ regulations as subject to evaluation;

• the relevant resource or activity was identified through agency expertise, through 

the scoping process, or from comments on past G&G EISs; or

• the resource or activity may be linked to one or more of the impact-producing 

factors (IPFs) associated with the OCS Program, and a reasonable probability of 

an interaction between the resource or activity and IPF should exist.

The public scoping process for this Programmatic EIS is described in Chapter 6. Public 

scoping meetings were held in seven cities (Tampa and; Fort Walton Beach, Florida; Mobile, 

Alabama; Gulfport, Mississippi; Galveston, Texas; New Orleans, Louisiana; and Silver Spring, 

Maryland). In addition to accepting oral and written comments at each public meeting, BOEM 

accepted written comments by mail and through a dedicated email address. BOEM received a total 

of 66 comments through email (65%), formal letters (13%), and public meeting testimony (32%). 

Each comment was read and categorized according to its source and the nature of the information 

provided in the comment. The scope and content of this Programmatic EIS have been structured to 

ensure that the issues and concerns expressed by stakeholders during the scoping process are fully 

addressed (USDOI, BOEM, 2013b).

2.10.1 Issues to be Analyzed

This Programmatic EIS addresses issues associated with various G&G activities, including 

potential IPFs and related impacts on environmental and socioeconomic resources and activities 

characteristic of the AOI. In addition, this Programmatic EIS addresses the potential environmental 
2-22 Alternatives Including the Proposed Action

and socioeconomic effects of accidents on AOI resources and considers cumulative impacts (i.e., 

the incremental impacts on AOI resources associated with the project alternatives).

The following issues were identified for detailed analysis:

• impacts of underwater noise on marine mammals, sea turtles, fishes, marine and 

coastal birds, benthic communities, Marine Protected Areas (MPAs), commercial 

and recreational fishing (fish catch), and other marine life;

• impacts of vessel traffic (risk of ship strikes) on marine mammals, sea turtles, 

marine and coastal birds, and Sargassum communities;

• impacts of vessel traffic on fishing, shipping, and other marine uses;

• impacts of aircraft traffic and noise on marine mammals, sea turtles, marine and 

coastal birds, and other marine uses;

• impacts of entanglement from marine equipment on marine mammals, sea 

turtles, fishes, other marine life, archaeological sites above the seafloor, and 

benthic communities;

• impacts of stand-off distances (the area that operators attempt to keep around 

the source vessel and its towed-streamer arrays clear of other vessel traffic that 

will result in a space-use conflict with other vessels) on commercial and 

recreational fishing, shipping, recreational resources, and other marine uses;

• impacts of vessel discharges on Sargassum communities;

• impacts of trash and debris on benthic communities, marine mammals, sea 

turtles, marine and coastal birds, endangered or threatened fish species, 

Sargassum communities, and recreational resources;

• impacts of seafloor-disturbing activities on sensitive benthic communities, 

including coral and hard/live bottom communities, and chemosynthetic 

communities;

• impacts of seafloor-disturbing activities on Essential Fish Habitat (EFH), Habitat 

Areas of Particular Concern (HAPCs), and MPAs;

• impacts of seafloor-disturbing activities on archaeological resources, including 

historic shipwrecks and prehistoric archaeological sites;

• impacts of drilling discharges on EFH, benthic communities, and archaeological 

resources; and

• impacts of accidental spills on benthic communities, marine mammals, sea 

turtles, marine and coastal birds, fishes and EFH, benthic communities, 

Sargassum communities, archaeological resources, recreational resources, 

MPAs, and other marine uses.
Gulf of Mexico G&G Activities Programmatic EIS 2-23

2.10.2 Issues Considered but Not Analyzed

As part of the scoping process, CEQ regulations require agencies to identify and eliminate 

from detailed study the issues that are not significant to the proposed action, have been covered by 

prior environmental review, or do not fulfill the purpose and need of the proposed action. 

Chapter 4.1.1 describes the screening process for impact analysis and identifies issues that were 

considered but not analyzed in detail. Examples include impacts of underwater noise on plankton; 

impacts of seafloor-disturbing activities on geology and sediment quality; impacts of vessel 

discharges on water quality; and impacts of vessel and aircraft on air quality. As part of the 

screening process, several resource areas were identified as having no expected impacts from G&G 

activities. The detailed rationale is included in Chapter 4.1.1. Those resources eliminated from 

detailed analysis include

• Human Resources and Land Use for Alternatives A, B, C, D, and F. BOEM 

does not expect there to be impacts to the local and regional economy as well as 

coastal infrastructure or changes in employment and earnings in the G&G 

service sector since current levels of G&G activities would be expected to 

continue, though there would be differences in how those activities are 

conducted among the alternatives. However, since there is a reduced level of 

G&G activities included in Alternatives E and G, an impact analysis is included 

(Chapter 4.13).

• Recreational Resources and Tourism. Because BOEM-regulated G&G 

activities would occur at least 3 or 9 nmi (3.5 or 10.4 mi; 5.6 or 16.7 km) 

(depending on the state) away from the coast in Federal waters, any impacts that 

may occur were determined to be minimal and would not be discernible among 

any of the action alternatives. The G&G activities that would occur in State 

waters are expected to be minimal and would be authorized by others with 

protective measures in place, such as the USACE.

• Air Quality. Because there will be a limited extent and duration of most G&G 

activities, the amount of air pollutants generated would be small and emissions 

will be distributed over a broad area of the OCS due to the generally nonstationary nature of G&G activities and therefore likely would not result in any 

elevated pollutant concentrations exceeding air quality standards.

• Water Quality. Because all vessels in U.S. and international waters are required 

to adhere to International Maritime Organization regulations under the 

International Convention for the Prevention of Pollution from Ships (MARPOL) 

limiting discharges (e.g., treatment of sanitary wastes and maceration of food 

wastes), avoiding releases of oily water, and prohibiting disposal of solid wastes, 

expected effects to water quality would be minimal. 

• Geography and Geology. Due to the nature of the G&G activities, expected 

effects to sediments are minimal.
2-24 Alternatives Including the Proposed Action

• Physical Oceanography. Due to ocean current characteristics, water-column 

density stratification, and vertical current structure, among other factors, which 

would be considered during planning, operation, and data post processing of 

G&G surveys or sampling efforts, no physical oceanographic resources would be 

affected by the G&G activities.

• Coastal Barrier Islands, Beaches, Seagrass, and Wetlands. Because BOEMregulated G&G activities would occur at least 3 nmi or 9 nmi (3.5 or 10.4 mi; 

5.6 or 16.7 km) (depending on the state), few, if any, negative impacts would 

occur to these resources. The activities that would occur in State waters are 

expected to be minimal and would be authorized by others with protective 

measures in place for protection of these resources.

2.11 ALTERNATIVES CONSIDERED BUT NOT CARRIED FORWARD

The following additional alternatives were identified during the scoping process. For the 

reasons identified below, they are not considered for detailed analysis in this Programmatic EIS.

2.11.1 Shutdown for All Marine Mammals Within the Level A Harassment 

Exclusion Zone

Under this proposed alternative, G&G activities would be shut down for all marine mammals 

within the Level A isopleths for potential harassment. This alternative would provide protection from 

potential exposure to Level A harassment sound levels for all marine mammals identified within the 

Level A harassment exclusion zone, including bow-riding dolphins or animals that actively approach 

G&G vessels.

Based on PSO sighting data from 2002 to 2008 (Barkaszi et al., 2012), it is estimated that 

shutdown for all bow-riding dolphins would increase shutdowns by approximately 35 to 41 percent 

and could result in 44 to 46 additional shutdowns per year across the fleet. However, multiple years 

of data collection and observations by PSOs of bow-riding animals report no observable impacts as 

they actively approach vessels and continue to bow-ride while vessels are conducting surveys. 

Therefore, to require shut-down for all bow-riding animals that actively approach the survey 

vessel is unwarranted and would be overly burdensome to industry by creating a 35- to 41-percent

increase in shut-downs and potentially prolonging survey duration and overall cost. Because of the 

foregoing, BOEM does not consider this alternative reasonable and, thus, will not carry it forward for 

additional analysis.

2.11.2 Require Alternative Technology Use

Under this proposed alternative, BOEM would not authorize the use of standard, large 

airguns as sound sources for seismic surveys. Industry would have to rely on other measures to 

obtain accurate data on the location and extent of hydrocarbon resources, including alternative 
Gulf of Mexico G&G Activities Programmatic EIS 2-25

acoustic source technologies that may produce less underwater noise and reduce the potential for 

impacts on marine life.

Alternative technologies are discussed further in Appendix F and include the following:

• marine vibroseis (vibrators);

• low frequency acoustic source (LACS) (patented);

• deep-towed acoustics/geophysical system (DTAGS);

• low-frequency passive seismic (LFPS) methods;

• low-impact seismic array (LISA);

• fiber optic receivers allowing smaller airguns; and

• airgun modifications to lessen impacts.

The preceding list is based in part on the Okeanos Seismic Airgun Alternatives Workshop 

(Weilgart, 2010) and BOEM’s Quieting Technologies for Reducing Noise during Seismic Surveying 

and Pile Driving Workshop (CSA Ocean Sciences Inc., 2014). In 2009, an international multidisciplinary group of geophysical scientists, seismologists, biologists, and regulators met in 

Monterey, California, to discuss potential alternatives and modifications to airguns and airgun array 

configurations in order to minimize the potential impacts from airguns (Weilgart, 2010). The 

Okeanos Seismic Airgun Alternatives Workshop panelists discussed promising new imaging 

technologies that are either completely silent or that can lessen the amount of seismic sound 

required to gather seismic data, thereby still allowing for a reduction of the economic risk of 

hydrocarbon recovery. The Okeanos Workshop panelists acknowledged that these technologies are 

purpose driven and do not work in all circumstances; additionally, most of the technologies are not 

yet advanced enough to be used commercially. This statement remains true today, and it has been 

further complicated by the continued development of new and improved acquisition techniques in 

seismic exploration, including (but not limited to), coil surveys, airgun hardware developments, fiberoptic receiver systems, and improved computational capabilities. Essentially, not only are these 

developmental systems working to achieve what the capabilities that existed 6 years ago, but they 

also need to compete against the proven improvements that have arisen since then.

Marine vibroseis appears to be a promising alternative technology, with several different 

systems being developed and tested. BOEM is aware that the oil and gas industry has formed a 

Joint Industry Program (JIP) on Marine Vibroseis whose goal is to develop prototypes and test 

potential technologies and that yet another industry sponsored subset of members from the 

American Petroleum Institute (API) has been working on three distinct vibroseis prototypes as a 

condition of the Settlement to litigation filed by Natural Resource Defense Council, et. al., vs 

Department of Interior with API, et. al., as Intervenor-Defendents. BOEM acknowledges that these 

research and development efforts will be necessary to provide new information about the potential 

viability of marine vibroseis and other technologies for commercial applications as BOEM examines 
2-26 Alternatives Including the Proposed Action

potential environmental impacts of these technologies when compared to existing technologies. In 

data comparisons, marine vibroseis data should be theoretically comparable to airgun data; 

however, there are some challenges especially in deepwater. For example, by its very nature, a 

vibroseis system is attempting to produce the most useful portion of the frequency spectrum in a 

controlled way. This is currently produced by an airgun in a pulsed manner in about 10 milliseconds. 

However, a vibroseis system is distributing this acoustic energy as a swept (nonpulsed) manner 

lasting approximately 10 to 15 seconds. At some point in the signal processing of the echoes 

received by this system, this energy needs to be re-combined so that the geological structure that 

produced those echoes can be clearly resolved or seen. This requires not only expanded 

computational power, but also the appropriate configurations of the entire receiver system 

(hydrophones, streamer configuration, and support systems). Additionally, there are a number of 

technical issues with the vibroseis system itself ranging from purely mechanical ones (e.g., the 

number of sources in an array, their tow-body design and stability, the number sources designed in 

for redundancy and reliability, etc.), to electronic ones (e.g., power supply and cabling issues, 

selection of the signals to be sent, etc.), to operational considerations (e.g., the best operating depth 

for the system physically or acoustically, tow speed selection, etc.). Even after a vibroseis source 

system has been fully developed to achieve some specified specifications, the details of how the 

source integrates into an operationally reliable and useful seismic survey system will require a great 

deal of effort. Additional discussions of these alternative technologies are included in Appendix F. 

Alternative technologies are in various stages of development and none of the systems with 

the potential to replace airguns as a seismic source are currently commercially available for use on a 

scale of activity considered in the proposed action scenario described in Chapter 3. Although some 

alternative technologies are available now or will be in the next several years, none are currently, or 

will be in the next 10 years, at a stage where they can replace airgun arrays outright; however, some 

may be able to be used in select environments when commercially available. This alternative would 

not provide the oil and gas industry or the government with sufficiently accurate data on the location, 

extent, and properties of hydrocarbon resources or the character of formation fluids or gases, as well 

as information on shallow geologic hazards and seafloor geotechnical properties, in order to explore, 

develop, produce, and transport hydrocarbons safely and economically. As this alternative does not 

meet the stated purpose and need, and cannot be analyzed on a programmatic scale at this stage, it 

has not been carried forward for detailed environmental impact analysis in this Programmatic EIS. 

Should these technologies become commercially available, BOEM can evaluate them in the future 

as a stand-alone, site-specific request or in a supplemental programmatic document.

2.11.3 Requirement to Obtain an LOA or IHA Prior to Receiving BOEM’s G&G 

Approval

As noted in the discussion of alternatives, this Programmatic EIS supports two potential 

agency actions: BOEM’s G&G survey program in the GOM and NMFS’ issuance of MMPA 

authorizations for those G&G activities. It is expected that industry applicants seeking to conduct 

G&G activities in the GOM would seek both BOEM and NMFS approval. BOEM’s authorization 

would result, directly or indirectly, from lease or permit issuance. The NMFS’ authorization would 
Gulf of Mexico G&G Activities Programmatic EIS 2-27

result from an MMPA authorization in the form of an LOA if NMFS issues ITRs or as an IHA if ITRs 

are not issued or activities are not covered by the ITRs. While industry is not required under the 

MMPA to obtain an authorization before proceeding, industry is required to seek a BOEM permit or 

authorization and an entity conducting G&G activities would be in violation of the MMPA if takes 

occur without an MMPA authorization. Impacts from G&G activities not authorized by BOEM are not 

a reasonable scenario to evaluate in this Programmatic EIS, since BOEM would enforce compliance 

with its regulations to prevent activities under its jurisdiction and not permitted to be conducted. The 

potential impacts of BOEM-approved G&G activities in the GOM, whether or not they are conducted 

under an NMFS authorization, have been considered in detail in the alternatives discussed in this 

Programmatic EIS. The issuance of an MMPA authorization prior to receiving a BOEM G&G permit 

or authorization does not in and of itself alter the proposed activities or their impacts as analyzed in 

the action alternatives, but the mitigations imposed by those authorizations could. The action 

alternatives analyzed in this Programmatic EIS already include the breadth of G&G activities 

expected to be proposed in the GOM, as well as feasible mitigations that are likely to be considered 

and applied through BOEM approvals and/or MMPA authorizations. Should NMFS determine that 

additional or different mitigations are warranted when issuing an LOA or IHA, that decision would be 

subject to additional NEPA review, as appropriate. It is expected that any mitigation NMFS or 

BOEM applies in the future would reduce or avoid impacts analyzed in this Programmatic EIS. For 

the foregoing reasons, BOEM and NMFS have determined that this alternative (Requirement to 

Obtain an LOA or IHA Prior to Receiving BOEM G&G Approval) need not be analyzed as a separate 

alternative in this Programmatic EIS. The potential impacts from G&G activities and mitigations 

likely to be included in any BOEM approval or NMFS authorization have already been analyzed in 

the action alternatives carried forward for full analysis in this Programmatic EIS.

2.12 MITIGATION MEASURES CONSIDERED BUT NOT CARRIED FORWARD

The following additional mitigation measures were identified during the scoping process. For 

the reasons identified under each, they were not carried forward in this Programmatic EIS. 

However, as discussed above, in addition to the NTLs and guidance noted applicable to specific 

program areas, all G&G surveys will follow requirements consistent with the monitoring identified in 

the ITRs. The monitoring requirements will be adaptive such that they be modified based on new 

information, new technologies, monitoring results, and specific program needs throughout the 

timeframe of this Programmatic EIS. Therefore, as these technologies and mitigation measures 

advance, they could be included at a later date after evaluation by BOEM prior to imposing as lease 

stipulations for ancillary activities or COAs on a plan or a G&G permit or authorization.

2.12.1 Active Acoustic Monitoring

Active acoustic monitoring mitigation uses high-frequency sound (e.g., fisheries sonar) to 

survey a zone of the water column for marine species. The active systems create acoustic “images” 

for which species’ shapes and unique signatures can be determined. Scanning sonar equipment 

would be mounted on the vessel and would acoustically survey an area while the scan images are 

monitored by a shipboard observer. This technology has been used with good correlation between 
2-28 Alternatives Including the Proposed Action

shipboard observer sightings and sonar detections for mysticetes (Geoffroy et al., 2012; Pyc et al., 

2015). Active acoustics can be used in day or night time conditions.

Outside of experimental testing, this methodology has not been employed by seismic 

surveys as part of a mitigation plan and there are no standardized protocols for operations. Based 

on the Geoffroy et al. (2012) study, active acoustic surveys would require additional observers 

working in rotation alongside the visual and acoustic observers for 24-hour operations. The 

provision of reliable sonar for mitigation on board seismic vessels would require vessel, likely hull, 

modifications for equipment installation that may not be applicable from one survey to another.

Like traditional visual surveys, the sonar detection limits and reliability will be affected by 

weather and water conditions, size of the target, and location and activity of the target; therefore, 

active acoustic monitoring surveys may not offer distinct advantages under poor visibility conditions. 

There may be additional potential impacts or unintended consequences to consider with the 

introduction of another sound source into the water even though the frequency may be outside the 

functional hearing ranges of many marine mammals. Active acoustics may play a role in some 

offshore operations (e.g., decommissioning) to search for specific targets. More assessment of the 

technology, operating parameters, and associated costs is required before this method could be fully 

considered as a mitigation measure for the GOM.

2.12.2 Aerial Surveys

Traditional aerial surveys comprise a single or team of trained observers flying in an aircraft 

to survey for marine species in order to supplement the visual monitoring conducted from a vessel. 

Unmanned aerial surveys utilize a remote platform (e.g., drone or kite) with mounted camera 

equipment and an operator to conduct a smaller scale survey with the images relayed to the vessel 

observers. Aerial surveys offer an advantage to surveying for marine mammals and sea turtles due 

to an improved coverage area and the ability to spot animals from altitude.

Manned aerial surveys are used for mitigation in operations that present a high probability of 

lethal impacts to marine mammals or sea turtles within a small area and a short timeframe, such as 

during underwater blasting. However, they do not lend themselves to real-time mitigation for long 

duration projects such as seismic surveys due to the logistics of offshore flights, weather restrictions, 

and the functionality of the aerial observer’s field of view compared to the size of the mitigation zone. 

In addition, manned aerial surveys present a significant risk to personnel and have significant 

limitations for offshore waters due to the long transit times.

Unmanned aerial surveys may be useful in real-time monitoring as a tool used as part of the 

overall visual monitoring regime. A number of organizations, such as members of the offshore oil 

and gas industry, NMFS, BOEM, and the U.S. Navy, have been investigating the use of these 

surveys for a number of reasons, including, but not limited to, (1) unmanned surveys address safety 

concerns of putting human pilots and observers in potentially dangerous offshore areas; 

(2) unmanned aircraft can generally fly up to 20 hours, which is longer than manned surveys; 
Gulf of Mexico G&G Activities Programmatic EIS 2-29

(3) unmanned surveys can provide video data, even with high definition video cameras, which can 

be carefully reviewed post-flight rather than relying simply on visual observations during the flight; 

(4) unmanned surveys may provide for more frequent survey effort because securing personnel for 

flights is not necessary; and (5) aircraft can be launched from seismic ships. However, although the 

application of unmanned aerial surveys is highly promising, the technology and permitting 

environment for such systems is not yet fully developed and cannot be assessed as a standard 

mitigation measure at this time.

As stated above, if the technology is further developed and tested and permitting issues 

streamlined during the 10-year timeframe of this Programmatic EIS, unmanned aerial surveys could 

be implemented as a mitigation measure for future actions after further evaluation by BOEM prior to 

imposing as lease stipulations for ancillary activities or COAs on a plan or a G&G permit or 

authorization.

2.13 COMPARISON OF IMPACTS BY ALTERNATIVE

Alternatives A through G are carried through the detailed environmental impact analysis in 

Chapter 4. Table 2.10-1 compares the seven alternatives with respect to the impact significance 

ratings from Chapter 4. 

To help frame the comparison of the impact levels included in Table 2.10-1, the following 

describes the process used for the development of significance criteria. Broad significance criteria 

were developed for each of the biological and socioeconomic resources present on the GOM OCS 

based on the results of resource screening and in consideration of recent environmental impact 

analyses and their respective impact descriptions (Chapter 4.1.2). Significance criteria reflect 

consideration of the context and intensity of impact (40 CFR § 1508.27), based on four parameters: 

detectability (i.e., measurable or detectable impact); duration (i.e., short term, long term); spatial 

extent (i.e., localized, extensive); and severity (i.e., severe, less than severe). The impact 

descriptions developed for this analysis are based on impact thresholds employed and impacts 

determined in earlier EISs (USDOI, BOEM, 2015b). For biological and socioeconomic resources, 

the significance criteria have been broadly defined as follows:

• Nominal: Little or no measurable/detectable impact.

• Minor: Impacts are detectable, short term, extensive or localized, but less than 

severe.

• Moderate: Impacts are detectable, short term, extensive, and severe; or impacts 

are detectable, short term or long term, localized, and severe; or impacts are 

detectable, long term, extensive or localized, but less than severe.

• Major: Impacts are detectable, long term, extensive, and severe.

These broad significance categories were tailored as needed to evaluate impacts of each 

relevant IPF on each resource. These tailored significance criteria are included in Chapter 4 for 
2-30 Alternatives Including the Proposed Action

each resource evaluated. Each impact parameter was evaluated on a resource-specific basis to 

determine the appropriate impact level for each IPF. For biological resources, attributes such as 

distribution/range, life history, and susceptibility to impact of individuals and populations were 

considered, among other factors.

The evaluation process to determine significance considered potential impacts by context 

(e.g., short versus long term) and intensity (e.g., severity), following NEPA regulations (40 CFR § 

1508.27). Context was defined as the extent of the effect (geographic extent or extent within a 

species, ecosystem, or region) and any special circumstances (e.g., endangered species or legal 

status), while intensity of an impact was defined as its magnitude. Moreover, the potential effect was 

evaluated in terms of duration or frequency (short term, long term, or intermittent). The evaluation 

process also consisted of evaluating the likelihood (likely or not likely) of an effect to occur (i.e., 

whether it was plausible or just speculative). During the preparation of the impacts analysis, each 

application of an impact level was accompanied by a statement explaining how the judgment was 

reached. Data or information from peer-reviewed journals or other sources used to support each 

determination are cited, as applicable. Otherwise, the determinations are based on the best 

available information.

The impact levels are based on numbers of individuals, groups, and local population-level 

effects to all species within a resource category throughout the entire AOI but also consider specific 

species, species groups, or stocks and their spatiotemporal distribution, as applicable, to discuss 

specific protection afforded. The analysis assessed individual species with special circumstances or 

species group in a given resource category relative to the protection afforded by the mitigation 

measures included in each alternative, but the impact level is determined for the resource category 

as a whole.

Table 2.10-1 provides a summary of the impacts as determined in Chapter 4 for all 

resources and IPFs across Alternatives A through G. The impact levels for some resources and 

IPFs include a range. This occurs when an IPF may have acute, short-term, or spatiotemporal 

impacts that can result in an increase in impacts depending on a specific parameter but overall the 

IPF warrants a lesser rating under routine activities across all species in a resource category 

throughout the AOI.

The seasonal restriction in coastal waters for operation of airguns from January 1 to April 30 

in Alternative B and from February 1 to May 31 in Alternatives C through F was designed to protect 

the coastal and estuarine stocks of the common bottlenose dolphin during their peak reproductive 

activity by reducing active acoustic sound sources from airguns; however, when applying the 

significance criteria for marine mammals (Chapter 4.2.2.1), which evaluates population-level 

impacts for all marine mammals that may occur in the AOI, that protection does not result in an 

overall reduction of impacts across the alternatives. Although this measure would provide protection 

to marine mammals that may occur within the restriction area during the seasonal restriction period, 

it would not benefit individual marine mammals outside of these areas or during other times of year.
Gulf of Mexico G&G Activities Programmatic EIS 2-31

The seasonal restriction in coastal waters would also provide protection for loggerhead 

turtles during a portion of their mating and nesting/inter-nesting season, but when applying the 

significance criteria for sea turtles (Chapter 4.3.2), which evaluates population-level impacts for all 

sea turtles in the entire AOI, this mitigation measure does not result in an overall reduction of the 

impact level. Other resources, including endangered fish and coastal fish species, coastal birds, 

coastal MPAs, Sargassum, commercial and recreational fisheries, archeological resources, and 

other marine uses would receive the associated protection in that area during the restriction period, 

but not to an extent that would reduce the overall impact level annually or across the full analysis 

period.

In accordance with NTL 2012-JOINT-G02, prior to the Settlement Agreement, shutdown of 

airguns was only required for whales (Bryde’s, beaked, sperm, or dwarf and pygmy sperm whales). 

Under Alternatives B-F, the expansion of the PSO Program adds shutdown requirements for 

manatees, applies to all deep-penetration seismic airgun surveys in the GOM regardless of water 

depth, provides specific protection to marine mammals, and may afford some protection to sea 

turtles; however, when applying the significance criteria for sea turtles (Chapter 4.3.2), which 

evaluates the impacts at the individuals, groups, and local population level in the entire AOI does not 

result in an overall change of the impact level. This mitigation does not apply to other resources; 

therefore, no changes in impact levels are realized. Similarly, the expanded use of PAM applies 

specifically to marine mammals, and PSOs can monitor for marine mammals, affording some 

additional protection. However, when applying the significance criteria for these resources, this 

mitigation measure would not reduce the impacts for all marine mammals present in the AOI to the 

extent that the impact level for either resource would change.

Alternative E includes a reduction of 10 percent or 25 percent in deep-seismic, multi-client 

activities (Tables 2.5-2 and 2.5-3), incrementally reducing the extent of seismic survey related 

sound sources (airguns), vessel and equipment noise, vessel traffic, aircraft traffic and noise, and 

trash and debris within the AOI, and thus, incrementally decreasing impacts from these IPFs to all 

resources. However, when applying the resource specific significance criteria, the reduction of 

overall seismic airgun activity under the two sub-alternatives included in Alternative E is not enough 

to reduce the overall impact determinations from Alternative A. 

Four area closures are introduced in Alternative F: the CPA Area Closure Area, the EP Area 

Closure Area, the Dry Tortugas Closure Area, and the Flower Gardens Closure Area. The selection 

of these closure areas was based on expert opinion (within NOAA and BOEM) of the relative 

densities of and biological importance to target cetacean species within the AOI, such as the 

endangered sperm whale, Bryde’s whale, and beaked whales as well as reef and pelagic fishes 

associated with the FGBNMS. Closure of these areas from airgun surveys would provide refuge to 

these species (as well as the suite of other deepwater cetacean species of the GOM in these areas) 

during the 10-year period of this Programmatic EIS. However, with exception of the Bryde’s whale 

whose distribution appears to be largely limited to the EPA Closure Area, other species regularly 

move beyond the boundaries of the closure areas. Therefore, protection is afforded to those target 

species, as well as other species present in those closure areas; however, the protection afforded to 
2-32 Alternatives Including the Proposed Action

most species by these closure areas would be limited because their presence outside of the closure 

areas would expose them to potential impacts from seismic airgun survey activities at a 

concentrated level because, for purposes of this analysis, the same level of activity is anticipated to 

occur within the reduced survey area (i.e., the AOI minus the closure areas). In addition, other nonairgun G&G activities would still occur throughout the AOI, including in the closure areas although 

they would be limited. Therefore, even though protection is afforded to target species, the mitigation 

provided by the implementation of these closure areas would reduce but not prevent impacts to the 

resources in the AOI. Based on resource-specific significance criteria (Chapter 4), this measure, 

while it would reduce potential effects in the closure areas, would not change the overall level of 

impacts within the AOI from deep-penetration seismic airgun surveys from Alternative A.

Alternative G includes no new G&G activities that require permits or authorizations from 

BOEM. However, previously authorized activities would still occur under existing agreements, 

permits, or authorizations. This would include a very limited number of localized survey activities to 

support ongoing oil and gas exploration and development on existing leases. Alternative G does not 

meet BOEM’s mandates outlined in the OCSLA because orderly development of oil and gas would 

not occur under this alternative. Impacts from Alternative G would be reduced from the other 

alternatives because very limited (i.e., previously approved) survey activities would occur in the short 

term. 

Overall, the entire suite of mitigation measures included in Alternatives A through G affords 

protection to specific species and may reduce impacts to a degree for those specific species on a 

spatial or temporal scale. These specific protections are discussed in Chapter 4. Table 2.10-1

provides the impact levels by resource and IPF across Alternatives A through G. Below is a 

summary of the notable impact levels for each resource category and an assessment of changes of 

impact levels across the alternatives.

• Impacts to marine mammals from deep-penetration seismic airgun surveys result 

in extensive (i.e., affecting large numbers of individuals), short-term but not 

severe impacts, with limited physical injury or mortality expected. Some of the 

mitigation measures included in the alternatives provide a level of protection to 

various target species and afford a reduced level of impacts to those target 

species and biologically important periods and geographic locations (e.g., 

seasonal restrictions in coastal waters affords protection to individual members of 

the bay, sound and estuary [BSE] stocks during their calving season as well as 

coastal stocks of bottlenose dolphins, Atlantic spotted dolphins, and individual 

manatees that may occur in coastal and inshore waters; the EPA Closure Area 

provides protection targeted to the Bryde’s whale, with protection afforded to 

other species present in the closure area; and the CPA Closure Area provided 

targeted protection to the sperm whale, with protection afforded to other species 

within the closure area). However, when impacts to all marine mammals within 

the AOI during the 10-year timeframe of this Programmatic EIS are considered 

for the impact-level determination, the overall impact level is moderate, 
Gulf of Mexico G&G Activities Programmatic EIS 2-33

depending on the stock, for Alternatives A through D, minor to moderate for 

Alternative E, minor for Alternative F, and minor, declining to no impact for 

Alternative G due to the minimal level of proposed deep-penetration seismic 

airgun surveys and eventual phasing out of activities. Minor impacts are 

expected for shallow-penetration airgun surveys and non-airgun HRG surveys for 

Alternatives A-F based on exposure modeling. Impacts under Alternative G area 

assessed as minor, declining to no impact. Impacts from vessel and equipment 

noise are assessed as nominal to minor for Alternatives A-F because many 

marine mammal species produce and perceive low- to mid-frequency sounds; 

furthermore, the effect of increased ambient noise on marine mammals has the 

potential to mask biologically significant sounds. Impacts under Alternative G 

range from nominal to minor, declining to no impact. Vessel collisions with 

marine mammals are likely to be avoided; however, if a collision did occur it 

could result in mortality. Therefore, depending on whether or not a collision did 

occur, nominal to moderate impacts are expected for Alternatives A-F. Impacts 

under Alternative G range from nominal to moderate, declining to no impact. 

Potential impacts to marine mammals from an accidental fuel spill are expected 

to range from nominal to minor, depending on the numbers of individuals 

coming into contact with the spilled fuel and their exposure time as well as the 

exposure of federally listed species to the spilled fuel, for all alternatives, except 

Alternative G (nominal to minor declining to no impact). Other IPFs affecting 

marine mammals are assessed as nominal for Alternatives A-F and nominal

declining to no impact under Alternative G.

The behavioral impacts anticipated as a result of the proposed actions analyzed 

in this Programmatic EIS are short-term disruption of behavioral patterns, 

abandonment of activities, and/or temporary displacement from discrete areas. 

Due to the extensive mitigations in the proposed action, no serious injuries or 

mortalities are anticipated.

• Impacts to sea turtles are assessed as minor for airgun surveys for Alternatives 

A-D and F because they are not expected to result in substantial changes to 

behavior, growth, survival, annual reproductive success, or lifetime reproductive 

success (fitness). Due to the reduced level of proposed activities under 

Alternative E, the impact level is expected to range from nominal to minor. Due 

to the minimal level of proposed deep-penetration seismic airgun surveys and 

eventual phasing out of survey activities under Alternative G, the impact level is 

reduced to nominal, declining to no impact. In addition, some protection is 

afforded to sea turtles in Alternatives B, C, D, E, and F to reduce the extent of 

potential PTS auditory injuries from implementation of the expanded PSO 

program, but not significantly enough to change the overall impact level. For 

Alternatives A-F, nominal to minor impacts are expected for non-airgun HRG 

surveys. However, for Alternative G, since the level of non-airgun HRG surveys 

would be significantly reduced and eventually phased out, the impact to sea 
2-34 Alternatives Including the Proposed Action

turtles would be nominal, declining to no impact. Impacts to sea turtles from 

vessel traffic would range from nominal to moderate (if a collision occurred) for 

Alternatives A-F since the support vessels associated with G&G activities travel 

at higher speeds and the potential for collisions is increased at night and at times 

of reduced visibility. However, for Alternative G, the impact to sea turtles would 

be moderate, declining to no impact. Potential impacts to sea turtles from an 

accidental fuel spill are expected to range from nominal (if the fuel does not 

contact individual sea turtles) to minor (if individual sea turtles encounter the 

dispersed windrows of the surface slick) for all alternatives, except Alternative G 

(nominal to minor declining to no impact). Impacts from 

entanglement/entrapment would be nominal for all alternatives except 

Alternative G, which would be reduced to no impact over time as survey 

activities are phased out. Other IPFs affecting sea turtles are assessed as 

nominal for Alternatives A-F and nominal declining to no impacts under 

Alternative G.

• Impacts to fish resources and EFH are assessed as nominal to minor for airgun 

surveys and for vessel and equipment noise across Alternatives A-F based on 

the potential to disrupt spawning aggregations or schools of important prey 

species, the mobile and temporary nature of most surveys, the small area of the 

seafloor affected during the surveys, and the possibility of fishes to temporarily 

move away from noise that is affecting them. Impacts under Alternative G would 

range from nominal to minor, declining to no impact as activities are phased 

out. Impacts from an accidental fuel spill range from nominal to minor for 

Alternatives A-F based on the location of the event and presence of fish or 

buoyant eggs and larvae. Impacts from an accidental fuel spill under 

Alternative G would range from nominal to minor, declining to no impact as 

activities are phased out. Other IPFs affecting fish resources and EFH are 

assessed as nominal for all alternatives with the exception of entanglement for 

Alternative G, which would be no impact since there is no equipment used that 

could cause entanglement.

• Impacts to benthic communities are assessed as nominal for all applicable IPFs 

and alternatives, except Alternative G, due to the existing protective measures in 

place for avoiding known sensitive communities during seafloor-disturbing 

activities and the prevalence of soft bottom in the AOI. In addition, active 

acoustic sound sources have not been determined to have significant impacts to 

benthic communities. Impacts under Alternative G are reduced to no impact to 

nominal for all IPFs.

• Impacts to marine and coastal birds are assessed as nominal to minor for active 

acoustic sound sources, vessel and equipment noise, vessel traffic, and aircraft 

traffic and noise for Alternatives A-F. Impacts from an accidental fuel spill are 

nominal under most circumstances, may increase to minor based on timing and 
Gulf of Mexico G&G Activities Programmatic EIS 2-35

location, and could increase to moderate if a listed species or their prey are 

directly impacted across all alternatives. Impacts under Alternative G would be 

reduced to nominal, eventually declining to no impact. 

• Impacts to MPAs are assessed based on the impact levels presented across all 

resources that may occur within the boundaries of MPAs. Therefore, impacts 

from active acoustic sound sources range from nominal to moderate for all 

alternatives except Alternative G. Impacts from Alternative G would be reduced 

to nominal, eventually declining to no impact as survey activities are phased 

out. Accidental fuel spills range from nominal to moderate for all alternatives, 

with the exception of Alternative G, which would be reduced to nominal, 

eventually declining to no impact. 

• Impacts to Sargassum and associated communities are assessed as nominal for 

Alternatives A-F based on the widespread patchy distribution of Sargassum mats 

and the propensity of Sargassum mats to be undisturbed by physical 

displacement. Species that utilize Sargassum as habitat for all or some of their 

life cycle (e.g., fish, sea turtles, and invertebrates) would be spatially limited and 

short term. No serious damage to Sargassum and associated fauna is expected 

to occur for all alternatives. Impacts under Alternative G could be reduced over 

time from nominal to no impact, depending on whether or not there was an 

increase in exploratory drilling activity.

• Impacts to commercial fisheries are assessed as minor for airgun surveys for all 

alternatives except Alternative G which would be reduced to nominal, eventually 

declining to no impact, because limited number of surveys will result in fewer 

changes in catch rates from fish displacement. Impacts are expected to be 

intermittent, temporary, and short term. Since fishing equipment could be 

damaged, the potential for impacts are reduced by several measures, and any 

impacts would be spatially localized and temporary; impacts from entanglement 

are assessed as nominal to minor for all alternatives except Alternative E2, 

which would be nominal, and Alternative G, which would be nominal, declining 

to no impact as activities are phased out. Impacts from stand-off distance are 

assessed as minor for all alternatives except Alternatives E2 and G. Under 

Alternative E2 (25% reduction in line miles of deep-penetration seismic airgun 

surveys), a decrease in impacts to nominal from minor is expected for stand-off 

distance impacts because these types of surveys typically have the larger standoff distance requirements and large arrays. Under Alternative G, impacts would 

be nominal, eventually decreasing to no impact. Impacts from seafloor 

disturbance are assessed as minor for all alternatives, with the exception of 

Alternative G (nominal declining to no impact). The impacts from non-airgun 

HRG sound sources, vessel traffic, and accidental fuel spills impacts are 

assessed as nominal for Alternatives A-F due to the limited and localized 

activities; however, the potential exists for G&G activities to overlap with 
2-36 Alternatives Including the Proposed Action

productive fishing grounds. Under Alternative G, impacts would eventually 

decline to no impact. 

• Impacts to recreational fisheries are assessed as nominal for all alternatives for 

all applicable IPFs due to the short-term and localized interactions between 

recreational fishing and G&G activities, with the exception of Alternative G. 

Impacts under Alternative G would eventually decline to no impact. 

• Impacts to archeological resources from seafloor disturbance and entanglement 

are assessed as nominal to major, depending on the type of survey and 

whether or not site-specific information regarding potential archaeological 

resources is available, for all alternatives, except Alternative G. Under 

Alternative G, impacts would be reduced to no impact. Impacts from drilling 

discharges and accidental fuel spills are assessed as nominal for all 

alternatives, with the exception of Alternative G. Under Alternative G, impacts 

from drilling discharges would be reduced to no impact and impacts from 

accidental fuel spills would be nominal, eventually declining to no impact. 

• Impacts to other marine uses are assessed as nominal for all alternatives for all 

applicable IPFs because many of the components of other marine uses are 

expected to be conducted in support of or in coordination with G&G activities for 

all three Program Areas. In addition, activities would be of relatively short 

duration, with the time and extent dependent upon the type of G&G activity. 

Impacts under Alternative G would eventually decline to no impact as activities 

were phased out.

• Impacts to human resources and land use are assessed as no impact from all 

subcomponents (land use and coastal infrastructure, environmental justice, 

demographics, and socioeconomics) for Alternatives A, B, C, D, and F since 

these activities have been ongoing in the GOM for over 30 years. For 

Alternatives E1 and E2, a nominal impact to land use and infrastructure, 

environmental justice, and demographics is expected with the reduced level of 

activity. However, a minor impact to socioeconomics is expected since there 

would be some displacement of the workforce. For Alternative G, a minor

impact to all subcomponents is expected from the significant reduction in 

activities associated with this alternative, with a moderate incremental increase 

in cumulative impacts, as explained in Chapter 4.13.8. 

2.14 MITIGATION, MONITORING, AND EFFECTIVENESS

The proposed mitigation measures for all alternatives consist of some combination of 

monitoring components and operational procedures that are designed to minimize the potential for 

injury or harassment to marine mammal species during G&G surveys. The purpose of this section is 

to provide an overview of the potential mitigation measures that are proposed under all the 

alternatives. In this overview, the historic state of the mitigation, prior to the Settlement Agreement, 
Gulf of Mexico G&G Activities Programmatic EIS 2-37

in the GOM is detailed as a basis for comparison with the alternatives. The effectiveness of each 

mitigation measure is evaluated based on their application under requirements in the GOM as well 

as research and application in other areas of the G&G industry. NTL 2012-JOINT-G02 is the 

framework for most of the proposed mitigation measures because it was specifically developed to 

minimize noise impacts to protected species within the GOM and includes the conditions identified in 

Alternative A. The NTL, which originally came about as a result of the Section 7 consultation with 

NMFS specifically for sperm whales, has been used successfully in the GOM since 2002; and 

therefore, provides structure to assess effectiveness through the information collected during 

implementation of NTL mitigation measures to recommend practical measures for the future. Since 

the implementation of this NTL and its previous versions, the following have contributed to mitigation 

recommendations and requirements for future G&G activities in the GOM: (1) BOEM Mitigation 

Survey Report (Barkaszi et al., 2012), BOEM/NMFS observer standards Technical Memorandum 

(Baker et al., 2013); (2) research and workshops on acoustic criteria and sound and marine life 

(Southall et al., 2007; Weilgart, 2013; Barton et al., 2008; Hannay et al., 2011; USDOI, BOEMRE, 

2011; CSA Ocean Sciences Inc., 2014); and (3) GOM Settlement Agreement. Modifications to the 

original NTL framework were based on the lessons learned, recommendations, and regulatory 

requirements from these sources. The various modifications made to the original NTL framework 

assisted in the development of the alternatives considered in this Programmatic EIS. The individual 

mitigation measures considered in the proposed alternatives include the following:

• time and area restrictions;

• separation distances between surveys;

• use of lowest practicable source power output that is necessary to achieve 

survey goals;

• establishing an exclusion zone;

• visually and/or acoustically monitoring an exclusion zone;

• clearance period before activating sound source;

• ramp-up, or gradual increase in output energy, of the sound source;

• shutdown or deactivation of sound sources; and

• overall reduction in deep-penetration seismic airgun activities.

The components and procedures are described individually for each alternative and are 

presented in Tables 2-1 and 2-2. 

2.14.1 Time and Area Restrictions and Closures

Time-area restrictions limit G&G activities within certain areas and for time periods that have 

been determined as critical to certain species. These restrictions take a biological approach to 

mitigation in an effort to focus restrictive or reactive measures to areas likely to receive the greatest 
2-38 Alternatives Including the Proposed Action

benefit from those measures. In the GOM, water depth is a key factor used to help delineate area 

restrictions and closures for G&G operations.

In Alternatives A and G, mitigation requirements are applied when airgun surveys are 

operating in water depths of 200 m (656 ft) or greater within the CPA and WPA and in all water 

depths in the EPA. The 200-m (656-ft) isopleth was originally selected as a delineation boundary 

based on ESA consultation for the protection of the sperm whale (Northern GOM stock). 

Subsequently, other deepwater/deep-diving species such as beaked whales, Bryde’s whales, and 

Kogia spp., were afforded the same protections under the NTL as the ESA-listed sperm whale. 

Other MMPA protected species (delphinids) and ESA-listed marine turtle species are also included 

in the conditions of the current NTL and are afforded some, but not all, of the same protections 

designed for the sperm whale. As a condition of the Settlement Agreement, application of NTL 

2012-JOINT-G02 mitigation measures, in the interim, are applied to G&G activities in all water 

depths within the GOM (Alternative B). These same mitigation measures, from NTL 2012-JOINTG02, also apply to Alternatives C, D, E, and F. Alternative B also includes seasonal closures to 

deep-penetration seismic airgun surveys, which have been in effect since the Settlement Agreement 

for areas shoreward of the 20-m (65.6-ft) isobath between January 1 and April 30, while Alternatives 

C, D, E, and F expand this same seasonal closure area to between February 1 and May 31 

(Table 2-1).

Limiting or eliminating G&G activities from an area can be an effective mitigation strategy to 

reduce direct impacts from an activity within the closed or restricted area. Physical disturbances to 

species and habitats are eliminated with the removal of the activity from the area either seasonally or 

year-round. However, introduced noise is still likely to be present, at lower levels, if activities are 

occurring near the restricted or closed area. The noise levels propagated into the restricted or 

closed areas will be dependent on distance, source characteristics, and environmental parameters. 

There are considerations that need to be addressed prior to establishing such closures; for example, 

efforts to limit activity during a critical period for a single species may introduce greater potential 

impacts to other species or a more diverse suite of species during closure and non-closure periods. 

Distribution of and habitat use by the species of concern can fluctuate over time; therefore, area or 

seasonal restrictions need to be periodically reviewed and modified to meet the intended biological 

application, which can make survey planning challenging. All surveys or G&G activities may not 

cause the same impacts and may be better suited for consideration on an individual basis rather 

than a full closure for all activities.

2.14.2 Minimum Separation Distances

A minimum separation distance between concurrent G&G surveys using high-energy 

sources is designed to minimize the sound exposure levels for marine mammals and sea turtles 

moving through a large region. The separation distance is calculated such that individuals will have 

the opportunity to move away from sounds exceeding TTS levels without encountering another 

survey exposing them to the same sound levels. In this case, minimal sound “corridors” are 

maintained to allow for movement of marine life around and between the surveys. In practice, 
Gulf of Mexico G&G Activities Programmatic EIS 2-39

minimum separation distances become highly complex when considered within the context of sound 

propagation in water. To effectively create low-sound corridors, a thorough understanding of how 

each source propagates within the existing environmental conditions is necessary. In some cases, 

higher received levels could occur farther from, rather than nearer to, the sound source depending 

on absorption, reflection, and refraction of the initial sound and the location of the receiver (i.e., 

marine mammal). In addition to the complexity of sound propagation, there are no current studies 

documenting the use of such corridors by marine mammals. The animals’ specific activity (e.g., 

feeding, migration) at the time may be more influential than the availability of a low-sound corridor; 

therefore, a separation distance may give a false sense of impact minimization and not provide the 

desired protection levels. Some marine mammals have shown avoidance behavior to certain types 

of sound sources (Malme et al., 1983, 1984, 1986, and 1988; Richardson et al., 1986; Ljungblad 

et al., 1988; DeRuiter et al., 2013). However, much of the behavioral response has been variable 

and research is continuing on this matter. 

Alternative B includes minimum separation distance between surveys (not individual vessels 

within a survey) of 40 km (24 mi) within the settlement defined areas of concern (Figure 2.2-1) and 

30 km (19 mi) outside the areas of concern as a result of the current GOM Settlement Agreement. 

Documentation that separation distances produce low-sound corridors as well as research 

confirming the use of these corridors by marine animals is necessary before the measures 

effectiveness can be evaluated. Assessment of unintended consequences, such as lost fitness, and 

changes in population structure by using such corridor habitat is also needed to evaluate the 

effectiveness of this mitigation measure. Marine mammal species in the GOM are not highly 

migratory and are driven mainly by access to food resources; therefore, it is doubtful that separation 

distances would provide the necessary benefits to offset potential impacts from sound exposure.

2.14.3 Non-Duplicative Surveys and Lowest Practicable Source

Under Alternative B, two requirements are stipulated that are designed to reduce 

unnecessary noise into the AOI. While these are not active mitigation measures implemented at the 

time of the survey, they are considered in this discussion due to their mitigation intention to reduce 

sound impacts on marine mammals. In the non-duplicative survey requirement, the applicant of a 

G&G permit must state, in writing, justification for the survey, confirming that previous, duplicative, 

surveys have not been performed or do not provide the required data. In the lowest practicable 

source requirement, the applicant must provide an estimate of the total energy output per impulse 

with respect to each energy source to be used and confirm, in writing, that the proposed airgun 

arrays to be used are, to the extent practicable, of the lowest sound intensity level that still achieves 

the survey’s goals. The goal of these measures is to reduce the overall sound source levels in the 

AOI, which could be effective in achieving this goal. Overall reduction in sound input may have 

wide-scale benefits. As noted in Chapter 1, under the terms of the Settlement Agreement, BOEM 

convened two panels to determine the feasibility of including refined standards for these two 

requirements; however, the panels’ work on these matters is still in process and was not available at

the time the analysis for this Programmatic EIS was completed. While the process for determining 

these requirements are still under discussion by the panels (refer to Chapter 1.2.3.1), BOEM is 
2-40 Alternatives Including the Proposed Action

evaluating in this Programmatic EIS the potential effects and mitigations from the current 

requirements of the settlement agreement on non-duplicative surveys and lowest practicable sound 

source. Further, determining the feasibility of developing standards for determining lowest 

practicable sound sources and non-duplicative sound sources will not have an adverse effect on the 

impact determinations contained in this Programmatic EIS.

2.14.4 Exclusion Zone

An exclusion zone is an area around a sound source, typically reflective of sound (acoustic) 

isopleths, based on NMFS’ acoustic guidelines, that is monitored by visual and/or acoustic methods 

and demarcates the limits for active mitigation actions to take place. All alternatives use a standard 

exclusion zone radius of 500 m (1,640 ft) around a sound source (Joint Nature Conservation 

Committee, 2010; NTL 2012-JOINT-G02). Theoretically, this 500-m (1,640-ft) distance delineates 

limits for potential Level A exposure. In practice, the distance to the Level A potential exposure 

isopleth will be dependent upon the source levels, array configuration, operational parameters, and 

environmental and oceanographic conditions. The actual extent of the acoustic isopleths around the 

sound source will depend on the source level, source configuration, water depth, bottom properties, 

and sound propagation through the immediate environment. There has been discussion of the 

potential to model the project-specific sound sources and survey environments in order to provide 

operators and regulators with more accurate measures of the expected SPLs at various distances 

(MacGillivray and Mathews, 2012).

Establishing an exclusion zone in which protective measures are initiated is effective only if it 

can be successfully monitored. Monitoring success will depend on the abilities of the observer, 

observer equipment, environmental conditions, and the species to be detected (some species being 

more easily observed than others). The effects of these variables are discussed in the following 

section. Larger exclusion zones may require enhanced monitoring methods, which should be 

tailored to the exclusion zone and target species in order to be most effective as observer 

effectiveness decreases with increasing distance (Barlow and Gisiner, 2006). Larger exclusion 

zones offer a more conservative measure of protection to marine species; however, observer 

abilities are not infinite in distance, and so lower detection rates may result at greater distances, and 

thereby provide inaccurate accounts of mitigation effectiveness.

Operational downtime typically is equated with loss of production and implies that there is a 

necessary re-acquisition period needed to obtain the “missed” data from that downtime period. Due 

to the size of the survey array configurations and survey data parameters, re-acquisition requires a 

substantial operational effort, including having the survey and support vessels working in the 

prospect for longer periods (sometimes on the timescale of days to weeks) to adequately re-acquire 

data, which can result in longer periods of sound exposure in the area on a project-wide basis. In 

addition, frequency components of the propagated sound will reach different distances, and each 

receiver (i.e., marine mammal) may have individual sensitivity to sound levels and frequency bands.
Gulf of Mexico G&G Activities Programmatic EIS 2-41

2.14.5 Exclusion Zone Monitoring

Visual Observations by PSOs

The primary purpose of a visual PSO is to reduce the potential for injury or harassment to 

protected species by that ensuring mitigation and monitoring requirements are followed during G&G 

survey activities and to monitor any take of protected species (USDOC, NMFS, 2013a). The visual 

monitoring conducted by a PSO is intended to maintain clearance of an exclusion zone around the 

sound source, thereby reducing the potential for sound injury (i.e., hearing damage) or adverse 

impacts associated with disturbance of a species’ normal behavior. A PSO visually monitors the sea 

surface around the G&G survey vessel for the presence of marine mammals and sea turtles, as 

required under the permit/authorization conditions. The PSOs must successfully complete an 

approved training course prior to performing any G&G visual monitoring duties. The PSOs, required 

in all proposed alternatives, are responsible for visually surveying for protected species, data 

collection, informing the vessel captain and crew of actions necessary for compliance with mitigation 

requirements, and submitting data and reports to the BSEE on a biweekly basis.

Under the conditions included in NTL 2012-JOINT-G02 and for all action alternatives, 

specific for seismic airgun surveys, two PSOs will be on watch during all daylight hours (defined as 

nautical twilight dawn and nautical twilight dusk, regardless of source operations). The exception to 

this would be non-airgun HRG surveys, which require only one observer on watch, as proposed in 

Alternatives C, D, E, and F, as applicable. For seismic airgun surveys, PSOs work in a threeobserver rotational shift with two trained PSOs on active watch at all times and one PSO on break. 

Individual PSOs may only work 4 consecutive hours then must take a 2-hour break at which time no 

shipboard duties may be assigned. A PSO may work a total of 12 hours, including all shipboard 

duties, within any 24-hour period. The same rotational schedule is expected for all proposed 

alternatives.

Under NTL 2012-JOINT-G02 conditions, PSOs survey the exclusion zone and surrounding 

waters using binoculars and the naked eye for the presence of marine mammals and sea turtles. 

The PSOs must effectively determine the species and distance of the animal relative to the source in 

order to initiate any required mitigation actions. In addition, stipulations, terms, and conditions may 

be used to assign mitigation specifications within the framework of a lease agreement for a plan or 

permit/authorization.

Visual monitoring and data collection will be continuous during all daylight hours. The PSOs 

do not conduct monitoring at night or when the exclusion zone cannot be fully monitored (e.g., fog, 

rough sea conditions, precipitation). Suitable weather conditions should allow an unhindered view of 

the entire exclusion zone.

There are numerous factors that can influence the effectiveness of visual monitoring, 

including PSO experience and training, sea conditions, survey platform, visual monitoring 

equipment, and species behavior (Barlow et al., 2006; Barlow, 2015). Accurate, consistent, and 

frequent recording of sea-state conditions by a PSO will improve the assessment of visual 
2-42 Alternatives Including the Proposed Action

monitoring effectiveness. Sea conditions that are considered suitable for observation are not 

defined within the alternatives. However, many standardized surveys are conducted only in sea 

states under Beaufort 5 (Barlow et al., 2006; Fisheries and Oceans Canada [DFO], 2008; Barlow, 

2015). Beaufort Sea State 5 has moderate waves, many white caps, spray possible with wind 

speeds at 19 to 24 mph (17 to 21 kn), and wave heights of 6.6 ft (2 m). The limits of allowable sea 

conditions in which visual monitoring can be conducted for mitigation may need to be adjusted for 

specific areas and species as the ability to observe some species is more drastically affected by the 

sea state than others.

Outside of the required attendance at a PSO training course, there are no additional 

minimum qualification requirements for PSOs under any of the proposed alternatives. The 

capabilities and experience of the visual observers will have a direct effect on the effectiveness of 

visual monitoring as a mitigation measure. However, NMFS, with the assistance of BOEM and the 

BSEE, developed national standards for PSOs and data management, which are outlined in the 

2013 National Standards for Protected Species Observers Technical Manuscript (Baker et al., 2013). 

These standards recommend that a PSO has

• a bachelor’s degree from an accredited college or university with a major in one 

of the natural sciences; 

• a minimum of 30 semester hours or equivalent in the biological sciences, at least 

one undergraduate course in math or statistics; and

• experience with data entry on computers; or

• the PSO must have documented comparable experience.

Currently in the GOM, PSOs may be trained crew members or independent (3rd party) 

PSOs. Most PSOs working under NTL 2012-JOINT-G02 and the Settlement Agreement conditions 

are 3rd party contractors who are subcontracted by a QA/QC service company. It is the 

responsibility of the service company to select and deploy the PSOs. This trend is standard in the 

industry worldwide and is not expected to change under any of the alternatives in the GOM.

Acoustic Observations by PSOs (PAM Operator)

The primary purpose of a PSO working as a PAM operator is similar to a PSO conducting 

visual observations; however, the PAM operator acoustically monitors an area around the G&G 

survey vessel for the presence of vocalizing marine mammals. The PAM systems employed in the 

GOM for mitigation generally use a traditional towed configuration with the hydrophone array towed 

behind the source vessel and the PAM Operator on the same vessel. The PAM Operator listens and 

visually monitors the exclusion zone via sound analysis software that facilitates acoustic and visual 

representation of marine mammal vocalizations on a monitor. Recent BOEM permit conditions 

stipulate that standard practice for the GOM is that all PAM Operators be third-party observers 

(Epperson, official communication, 2015). Similarly, recent permit conditions in the GOM have 

stipulated that all PAM Operators maintain the same rotational watch schedule as described in the 
Gulf of Mexico G&G Activities Programmatic EIS 2-43

visual observation section. Therefore, these assumptions are used in analysis of the alternatives. 

Consistent with the above, two PAM Operators are required to work on board the source vessel for 

each 12-hour monitoring period. As technologies develop, new monitoring regimes may be 

considered that could reduce the number of on-vessel PAM personnel.

Under Alternatives A and G, the use of PAM is optional and if used would allow ramp-up and 

the subsequent start of an airgun survey from silence during times of reduced visibility (e.g., 

darkness, fog, rain, etc.) when such ramp-up otherwise would not be permitted using only visual 

observers (PSO). Under Alternative B, the use of PAM is required in all planning areas in water 

depths >100 m (328 ft) during times of reduced visibility. Proposed for Alternatives C through F, 

PAM would be required during times of reduced visibility in waters deeper than 100 m (328 ft) in all 

planning areas and would be a mandatory requirement at all times for use in Mississippi Canyon and 

De Soto Canyon lease block areas.

The PAM monitoring as a mitigation measure can be highly effective when implemented 

properly and when expectations are clearly defined. The PAM allows monitoring of the exclusion 

zone when visual monitoring is not possible. However, PAM will only detect vocalizing individuals 

that can be detected by the system under survey conditions. The effectiveness of PAM as a 

mitigation measure during G&G activities is directly influenced by the ability of the PAM operator and 

the deployment of appropriate PAM equipment for the monitoring environment. The PAM operators 

are expected to have had training and practical experience with documented proficiency in the 

detection, classification, and localization of marine mammal vocalizations in high-noise 

environments. Not all PAM systems are suitable for mitigation due to the localization and real-time 

action requirements; in other words, a PAM system used on one survey may not be suitable for 

other surveys. A detailed assessment of each PAM plan for proper implementation will drive the 

effectiveness of this mitigation measure.

PAM Monitoring Plan

The PAM technologies and system options are continually evolving, and each will have 

advantages and disadvantages for any particular geophysical survey. As such, there are several 

technical aspects to consider when evaluating the scope and application of a PAM system for 

mitigation requirements within cetacean regulations. Under all alternatives using PAM (Tables 2-1 

and 2-2), an acoustic monitoring plan is required to be submitted to the BSEE prior to the start of the 

survey. Evaluation of the PAM plan will include four main factors:

• appropriateness of the PAM system and the PAM operators for the project 

parameters and species assemblages;

• methods of deployment to minimize vessel and flow noise while maintaining 

safety of equipment and crew;

• assessment of the detection, classification, and localization (DCL) capabilities in 

regard to protocols for implementing mitigation actions; and
2-44 Alternatives Including the Proposed Action

• methods of assessing the efficacy and performance of the system during the 

project.

Because noise in a commercial mitigation setting is one of the greatest challenges for 

acoustic monitoring, moored arrays or arrays deployed from dedicated platforms beyond the 

influence of vessels and machinery have a distinct advantage of working in a relatively quiet 

environment. However, most mitigation applications require real-time monitoring, which results in 

the necessity of a towed array behind the source vessel. As stated previously, as technologies 

continue to evolve, other hardware configurations can be evaluated through the PAM Plan 

assessment process.

The software tools needed to address signal processing in a high-noise environment will 

have significant bearing on the effectiveness of PAM as a mitigation measure; and therefore should 

also be evaluated fully in the PAM plan. The primary purpose of any software package is to process 

and display visual representations of the signals that are received from the array in a way that allows 

the operator to detect, identify, and localize (i.e., estimate the location of a vocalizing marine 

mammal in the volume being monitored) target species. There are several good software packages 

on the market, some of which are free. Differences in software occur mainly in user-interface 

capabilities, degree of user adjustability in processing and display, automation, and methods of 

localization. Processing capabilities of the software and computer hardware need to reliably handle 

the data load. Adequate bandwidth for data transmission is critical to ensure data integrity and allow 

for proper mitigation implementation.

The PAM localization of animals is critical to the mitigation process. The most common form 

of localization is target motion analysis (TMA). The TMA method requires the following 

assumptions: 

• the target (i.e., sound source) is relatively stationary or moves slowly relative to 

the survey vessel;

• the source vessel towing the hydrophone array is traveling in a straight line;

• the marine mammal is producing frequent calls (at least every few minutes);

• if multiple animals are calling, they occur in compact groups, or individual callers 

are able to be clearly differentiated; and

• animals detected close to the vessel are not diving deeper than the horizontal 

distance to the array’s hydrophones.

If most of these assumptions can be met, then TMA works very well. If these assumptions 

cannot be met (which is the more common scenario), then the accuracy and reliability of localization 

is reduced and may reduce the ability of the PAM operator to implement mitigation actions. It is 

important to note that, while current BOEM requirements state that shutdowns for marine animals 
Gulf of Mexico G&G Activities Programmatic EIS 2-45

detected in the exclusion zone should be instantaneous, the reality of the TMA method requirements 

may substantially delay the mitigation action.

Under the current NTL 2012-JOINT-G02, PAM operators are required to provide an 

assessment of the usefulness, effectiveness, and problems encountered during monitoring and 

mitigation. However, there are no matrices or minimum requirement for data archiving to achieve 

this requirement; therefore, a useful assessment of the PAM system efficacy for a survey is difficult 

to obtain. Archival requirements stipulated in the PAM plan or under the permit conditions will have 

a direct correlation to the successful validation of data. While post-processing of full datasets is 

desirable, software that can sample several hours per day (for example) can reduce time and costs 

but still provide an unbiased post processing avenue for efficacy assessment.

Pre-Start Surveys

All action alternatives require a period of clearance, either visually or acoustically, prior to the 

start of any sound sources. Pre-start clearance surveys are defined as required periods of time in 

which the exclusion zone around the airguns is acoustically or visually monitored before initiation of 

the sound source. The time period for clearance prior to the initial ramp-up (airgun survey) or startup (non-airgun HRG survey) is 30 minutes. The premise behind this mitigation measure is that 

PSOs monitor for a period of time so that when the source is started, there is reasonable assurance 

that no marine mammals or sea turtles are within the exclusion zone. If a marine mammal or sea 

turtle is detected in the exclusion zone, there is a delay in source initiation to allow time for the 

animal(s) to leave the area.

While the premise of this mitigation measure is well founded, in practice the measure is most 

effective for stationary exclusion zones, which would be associated with geological surveys or 

vertical seismic profiles (VSPs), rather than traditional seismic airgun and non-airgun HRG 

geophysical surveys. On a moving vessel, the PSOs are monitoring a continuously changing 

exclusion zone up to the point of source initiation rather than clearing the actual exclusion zone that 

would be present at the time the source is initiated. The effectiveness of pre-start surveys as a 

mitigation measure, therefore, will vary greatly with species and diving behavior. To improve the 

effectiveness of this measure, monitoring should be focused ahead of the vessel to clear the area 

where ramp up is likely to begin. This improvement to the methodology will be more effective for 

visual monitoring than for acoustic monitoring.

2.14.6 Ramp-Up

Ramp-up of the source is defined as an incremental increase in the sound output over a 

certain time period. This gradual increase in sound level is designed to minimize the risk of 

exposing animals near or under the sound source to the maximum output levels. It is suggested that 

the ramp-up will serve as a warning to animals in the area and allow them time to move away from 

the source. There are few data on the efficacy of ramp-up as a mitigation measure. A study funded 

by the JIP and BOEM of humpback whale (Megaptera novaeangliae) responses to airgun ramp-up is 
2-46 Alternatives Including the Proposed Action

currently underway, and the results may provide an assessment of ramp-up effectiveness (refer to

http://www.uq.edu.au/whale/brahss-10-11 for the most recent information).

All alternatives require ramp-up as a mitigation measure for surveys using airguns. Nonairgun HRG survey equipment is turned on to full-power and begins to output sound sources; 

therefore, ramp-up is not applicable for these types of geophysical survey equipment.

2.14.7 Shutdowns of Sources for Protected Species

Shutdown of active sources is initiated when a protected species enters (or will soon enter) 

the exclusion zone. Shutting down the active source when a protected species is detected within the 

exclusion zone is designed to minimize the potential for animals to be exposed to sound levels that 

are potentially injurious (as defined by NMFS’ acoustic guidelines). While the source cannot be 

initiated from silence if any marine mammal or sea turtle is sighted within the exclusion zone, the 

alternatives differ on which species require a shutdown of a source that is operating. In Alternatives 

A and G, shutdowns would be required for all whales (non-delphinid cetaceans) in accordance with 

NTL 2012-JOINT-G02 and include Bryde’s, beaked, sperm, or dwarf and pygmy sperm whales. In 

Alternatives B, C, E, and F, the shutdown would be expanded to manatees. In these alternatives, 

there would continue to be no shutdown for sea turtles or dolphins (Family Delphinidae). In 

Alternative D, a source shutdown would be required for all marine mammals that enter the exclusion 

zone, with the exception of bow-riding dolphins (i.e., bottlenose, Fraser’s, Clymene’s, rough-toothed, 

striped, spinner, Atlantic spotted, pantropical, and Risso’s dolphins) that voluntarily approach the 

vessel. Shutdown for dolphins would be determined by the PSO and would not apply when 

individuals are bow riding or continuing to actively approach G&G operations. Vessel operators 

must comply immediately with a shutdown call from the PSO. There would be no shutdown for sea 

turtles under any alternative.

Modeling (and verifying) the mitigation zones to delineate the distances at which shutdowns 

will occur will increase the effectiveness of shutdowns. The TTS and PTS isopleths will vary 

significantly from project to project depending on the source characteristics, environmental 

parameters, and hearing functions of the potential species. Sound exposures within these isopleths 

will be minimized if the operational shutdowns are implemented based an accurate mitigation zone. 

A mammal detected within the exclusion zone has already potentially been exposed to PTS or TTS 

sound levels based on the fact that they are within the exclusionary isopleths. The shutdown 

mitigation measure minimizes the time exposed to those levels so that impacts are minimized to 

negligible levels. As discussed in Appendix D, the usefulness of mitigation depends on species 

characteristics and environmental conditions. Mitigation effectiveness, measured as percent 

reduction in exposures relative to no mitigation, is correlated to detection probability and animal 

density.

Based on the analysis of PSO reports from seismic mitigation surveys in the GOM between 

2002 and 2008, there were 144 shutdowns totaling 125.74 hours of lost production from visual 

detections of whales in the surveys’ exclusion zones (Barkaszi et al., 2012). This lost production 
Gulf of Mexico G&G Activities Programmatic EIS 2-47

equates to an average downtime of 58 minutes for the individual vessels requiring a mitigation 

shutdown or approximately 16 minutes of lost production per month across the entire seismic fleet in 

the GOM. This does not include production losses due to the necessary re-acquisition of survey 

sections that were interrupted due to the shutdown. Comparatively, there have been 51 shutdowns 

totaling 68.98 hours of lost production due to acoustic detections (data from July 2013 and 

December 2014 [the time period that nighttime PAM has been required under permit conditions]) 

(Epperson, official communication, 2015). The average downtime due to acoustic detection 

shutdowns for individual vessels was 1.9 hours, which equates to a loss of 42 minutes per month 

across the GOM seismic fleet. Comparable downtimes are expected for surveys working under 

Alternatives A, B, C, E, and F. However, with the additional shutdowns for dolphins in Alternative D, 

it is estimated that there would be approximately a 25-percent increase in the number of shutdowns. 

This is based on data from Barkaszi et al. (2012) showing that, out of all confirmed whale and 

dolphin sightings, 26.1 percent involved dolphins within 500 m (1,640 ft) of any active source.

2.14.8 Reduction in G&G Activity Levels

Alternative E presents options to reduce the overall number of deep-penetration seismic 

airgun surveys. Alternative E requires a reduction in deep-penetration, multi-client airgun surveys by 

either 10 or 25 percent. This action would likely be effective in reducing protected species 

cumulative sound exposures because a reduced number of surveys would be performed. This 

mitigation measure represents a Gulfwide strategy designed to reduce overall exposures and noise 

levels; however, these measures do not afford any additional mitigation benefit to surveys already in 

progress.

CHAPTER 3 

G&G ACTIVITIES 

AND 

PROPOSED ACTION SCENARIO

Gulf of Mexico G&G Activities Programmatic EIS 3-3 

3 G&G ACTIVITIES AND PROPOSED ACTION SCENARIO

3.1 INTRODUCTION

A variety of G&G techniques are used to characterize the shallow and deep structure of the 

shelf, slope, and deepwater ocean environments. The G&G activities and project activity levels that

are evaluated as part of this Programmatic EIS are described in this chapter and their applicability to 

the three program areas (i.e., oil and gas, renewable energy, and marine minerals) is summarized in 

Table 3.1-1. Detailed descriptions of all G&G survey equipment are provided in Appendix F. In 

general, the activities include the following:

• types of deep-penetration seismic airgun surveys used almost exclusively for oil 

and gas exploration and development (Appendix F, Section 1.1);

• other types of surveys and sampling activities used only in support of oil and gas 

exploration and development, including electromagnetic surveys, deep 

stratigraphic and shallow test drilling, and various remote-sensing methods 

(Appendix F, Section 1.4.4); 

• non-airgun HRG surveys used in all three program areas to detect and monitor 

geohazards, archaeological resources, and certain types of benthic communities, 

and to assess potential offshore sand resources for coastal restoration projects 

(Appendix F, Section 1.3); and

• geological and geotechnical bottom sampling used in all three program areas to 

assess the suitability of seafloor sediments for supporting structures (e.g., 

platforms, pipelines, cables, and renewable energy facilities such as wind 

turbines) or to evaluate the quantity and quality of sand for beach nourishment 

and coastal restoration projects (Appendix F, Section 2).

3.2 PROPOSED ACTION SCENARIO BY PROGRAM AREA

This chapter provides a basic discussion of the types of G&G activities that BOEM is 

proposing to authorize under the proposed action within the three broad program areas (oil and gas, 

renewable energy, and marine minerals). The projected activity levels for each program area are 

discussed and broken down by year and planning area in Tables 3.2-1 and 3.2-2 for oil and gas, 

Table 3.2-3 for renewable energy, and Tables 3.2-4 and 3.2-5 for marine minerals. Table 3.2-6

provides additional details to describe the activity types for all program areas. A summary of all 

projected levels of activity for all program areas is provided in Table 3.2-8. 

This EIS analyzes projected scenarios for activity levels that are expected to occur over the 

next 10 years. While BOEM acknowledges the current calendar year 2016 reduced level of

exploration G&G activity and the corresponding decrease in permit applications, BOEM assumes 

that future levels will return to previous historic levels within the next 10 years. BOEM must 

therefore be prudent and conservatively consider the full range of potential impacts. Therefore, the 

scenarios contain projections based on the analysis of recent historic activity levels and trends made 
3-4 G&G Activities and Proposed Action Scenario

by BOEM’s subject-matter experts who also considered Industry-projected activity levels in their 

estimates.

3.2.1 Oil and Gas Program G&G Surveys

Certain G&G activities are necessary precursor steps needed to determine if there is industry 

interest for oil and gas leasing in the AOI. The scope of this Programmatic EIS includes a NEPA 

analysis of specific types of G&G activity that can take place before or after leasing (Table 1.4-1). It 

includes the G&G activities needed for operators to make business decisions about acquiring leases 

and the G&G activities that can take place on and near a lease once it has been acquired by an 

operator.

In addition to the needs of private industry, G&G surveys provide important information for 

Government decisions. BOEM’s resource evaluation (RE) staff uses deep 2D and 3D seismic data 

for resource estimation and bid evaluation to ensure that the government receives a fair market 

value for OCS lease blocks that have received bids in OCS lease sales. They also use G&G data to 

help them make potential estimates of existing resources, to evaluate of worst-case discharge 

(WCD) for potential oil-spill analysis, and to evaluate sites for potential hazards prior to drilling.

The G&G activities for oil and gas exploration may include proposed activities that occur 

either before leasing takes place (prelease) or after authorization of an existing lease (postlease). 

The NEPA action for the various types of activities is shown in Table 1.3-1. 

A NEPA evaluation is part of the approval process for OCS plans under the Oil and Gas 

Program. The evaluation includes a proposed action at a specific location with specific tool types 

and intensity of G&G activity, which may be an EA. The consultations required under environmental 

law for protected species typically are carried out at the time of the NEPA evaluation for the 

proposed action of a lease sale, where all actions consequent to a lease sale are examined in an 

EIS, and not for each OCS plan.

Many postlease activities are guided by NTLs, which are posted to BOEM’s website, and 

those applicable to G&G activities are described in Appendix B. Ancillary activities are postlease 

operations by lease owners in furtherance of developing oil and gas resources. Ancillary activities 

are defined in 30 CFR § 550.105 and regulated in 30 CFR §§ 550.207 through 550.210. A 

discussion of ancillary activities and NTL 2009-G34 (“Ancillary Activities”) is provided in Appendix B. 

In conclusion, whether pre- or postlease, all G&G survey types for exploration, development, 

or decommissioning are subject to the same types of review, especially if airguns will be used or 

seafloor-disturbing activity is proposed.

3.2.1.1 Proposed Action Scenario

Typical prelease activities include deep-penetration seismic airgun surveys to explore and 

evaluate deep geologic formations. The 2D seismic surveys are usually designed to cover 
Gulf of Mexico G&G Activities Programmatic EIS 3-5 

thousands of square miles or entire geologic basins as a means to geologically screen large areas 

for potential hydrocarbon prospectivity. The 3D surveys can consist of several hundred OCS lease 

blocks and provide much better resolution to evaluate hydrocarbon potential in smaller areas or 

specific prospects. Other prelease surveys include largely passive data gathering methods such as 

electromagnetic, gravity, and magnetic surveys, as well as remote-sensing surveys from aircraft and 

satellites.

Postlease activities conducted by operators can include additional seismic surveys, nonairgun HRG seismic surveys, and seafloor sampling (including stratigraphic wells, shallow test wells, 

and geotechnical sampling). Examples of postlease seismic surveys include vertical seismic profiles 

(VSP) with geophone receivers placed in a wellbore and four-dimensional (4D; time-lapse) surveys 

to monitor reservoirs during production. Non-airgun HRG surveys are conducted in leases and 

along pipeline routes to evaluate the potential for geohazards, archaeological resources, and certain 

types of benthic communities. Geotechnical sampling is conducted to assess seafloor conditions 

with respect to siting facilities such as platforms and pipelines.

The following major categories of G&G activities conducted for oil and gas exploration are 

summarized in Table 3.1-1 and described by specific activity in Appendix F, and the projected 

activity levels are described in the following chapter: 

• seismic airgun surveys;

• non-airgun HRG surveys

• non-acoustic marine geophysical surveys; and

• geological and geotechnical surveys.

3.2.1.2 Projected Activity Levels

To construct a scenario for G&G surveys in support of oil and gas exploration, BOEM has 

evaluated recent trends in permit applications as well as industry estimates of future seismic survey 

activity. BOEM also has taken into account the restrictions under the Gulf of Mexico Energy Security 

Act (GOMESA), which precludes leasing, preleasing, or any related activity in all areas in the GOM 

east of the Military Mission Line (86°41' W. longitude), and the area within the CPA that is within 

125 mi (201 km) of Florida. The GOMESA restrictions place most of the EPA and a portion of the 

CPA under restriction from oil and gas leasing until 2022, which is within the time period covered by 

this Programmatic EIS (Chapter 4.12.1.6). However, geophysical surveys are not restricted by 

GOMESA.

Projected activity levels for geophysical surveys related to oil and gas exploration over the 

10-year time period analyzed in this Programmatic EIS are shown in Table 3.2-1. The G&G surveys 

for the Oil and Gas Program could occur anywhere in the AOI; however, as shown in Table 3.2-1, a 

higher activity level is expected in deeper waters.
3-6 G&G Activities and Proposed Action Scenario

While the primary focus of the analysis in this Programmatic EIS is on seismic airgun and 

non-airgun HRG surveys, there are many other oil and gas surveys that do not depend on sounds 

for actual data collection (Appendix F); however, the surveys can contribute operational and 

equipment noise while the surveys are being conducted. These include controlled source 

electromagnetic (CSEM), magnetometer, shallow test drilling, magnetotelluric, gravity and magnetic 

surveys, full sensor gravity (gradiometry), aeromagnetic surveys, COST wells, shallow test drilling, 

geologic coring, cone penetrometer tests (CPTs), and seafloor sampling. Non-acoustic and

geological activities that have an estimated level of activity broken down by year and planning area 

are included in Table 3.2-2. BOEM anticipates that only one aeromagnetic survey may be 

conducted in the AOI during the time period covered by this Programmatic EIS. 

Although gravity, magnetic, and electromagnetic surveys are conducted in the GOM, they 

are almost always complementary to airgun and non-airgun HRG seismic surveys. The principal 

seismic acquisition method is 3D, using towed hydrophones (streamers) or seafloor cables and 

nodes (geophones) as acoustic receivers. Time-lapse surveys (4D) are 3D surveys that are 

repeated one or more times after the original survey and are used for reservoir monitoring. Seismic 

airgun surveys, using a hydrophone and three orthogonal geophones, are also more frequently 

conducted to obtain four-component (4C) data, seismic pressure, vertical motion, and two horizontal 

motions of the seafloor.

A summary of the projected levels of activity for all program areas over the 10-year project 

period is provided in Table 3.2-8. Specific to the Oil and Gas Program, the total projected line miles 

or geological tests over the 10-year time period for each major activity category are as follows:

• seismic airgun surveys (i.e., sum of VSP, SWD, 2D, 3D, WAZ, and 4D surveys) 

totaling 2,485,992 line miles (4,000,816 line kilometers); 

• non-airgun HRG surveys totaling 103,025 line miles (186,803 line kilometers); 

• non-acoustic marine geophysical surveys totaling 8,120 line miles (13,068 line 

kilometers); and

• geological and geotechnical surveys (i.e., bottom sampling) totaling 

2,241 tests/cores/grabs/probes/wells.

3.2.2 Renewable Energy Program G&G Surveys

BOEM is responsible for offshore renewable energy development in Federal waters and 

anticipates that any potential renewable energy projects would need to be supported by G&G 

surveys in the GOM. While there are no projects planned, potential future projects may include wind 

energy, carbon sequestration, and hydrokinetic power.

Under the renewable energy program (30 CFR part 585), lessees are granted the right to 

use leased areas to develop their plans for renewable energy projects, which must be approved by 

BOEM. Specifically, the regulations require that a lessee provide the results of G&G surveys within 
Gulf of Mexico G&G Activities Programmatic EIS 3-7 

a SAP, COP, or GAP. The G&G surveys conducted in support of SAPs, COPs, and GAPs can 

include the following: 

• shallow hazards surveys (30 CFR §§ 585.610(b)(2), 585.626(a)(1), and 

585.645(a)(2)); 

• geological surveys (30 CFR §§ 585.610(b)(4), 585.616(a)(2), and 585.645(a)(4)); 

• geotechnical surveys (30 CFR §§ 585.610(b)(1), 585.626(a)(4), and 

585.645(a)(1)); 

• biological surveys (30 CFR §§ 585.610(b)(5), 585.626(a)(3), and 585.645(a)(5)); 

and 

• archaeological resource surveys (30 CFR §§ 585.610(b)(3), 585.626(a)(5), and 

585.645(a)(3)).

BOEM refers to these surveys as “site characterization” activities. The G&G surveys are 

conducted in support of these planning requirements to develop a lease. Although BOEM does not 

issue permits or approvals for these site characterization activities, it will not consider approving a 

lessee’s SAP, COP, or GAP if the required survey information is not included. If the lessee is 

required to obtain an authorization pursuant to Section 101(a)(5) of the Marine Mammal Protection 

Act prior to conducting survey activities, the lessee must provide to the lessor a copy of such 

authorization prior to commencing survey activities, pursuant to 30 CFR 585.801(b).

BOEM’s Office of Renewable Energy Programs (OREP) has developed guidance documents 

for various surveys, including G&G surveys, to support SAP, COP, and GAP submittal, including in 

the GOM (USDOI, BOEM, 2015c). The guidance includes acceptable instrumentation, survey 

design parameters, and the report outputs that allow BOEM decisions to be made.

3.2.2.1 Proposed Action Scenario

To estimate the survey activity that could reasonably result from renewable energy lease 

issuance and approval of site characterization activities in the GOM associated with wind, marine 

hydrokinetic power, and alternate use of existing platforms, BOEM’s GOMR developed an activity 

scenario incorporating information gathered from various sources. These sources include the Gulf 

Coast States’ Coastal Management Programs; interviews with industry that have shown interest in 

developing renewable energy projects in the GOM; information from the U.S. Department of Energy 

(USDOE), National Renewable Energy Laboratory (NREL); and information gathered from the 

Atlantic OCS Proposed Geological and Geophysical Activities; Mid-Atlantic and South Atlantic 

Planning Areas; Final Programmatic Environmental Impact Statement (USDOI, BOEM, 2014b).

Wind

The NREL (USDOE, NREL, 2010) produced maps indicating the offshore 90-m (295-ft) wind 

resource potential. As indicated by the NREL (USDOE, NREL, 2010), the GOM is limited to the 
3-8 G&G Activities and Proposed Action Scenario

WPA for wind resource potential, with the southeast Texas coast having the highest potential for 

wind resources.

From the information provided by the State Coastal Management Programs, the NREL, and 

Schellstede and Associates, Inc., BOEM assumes that up to one new wind energy lease could be 

issued in the Gulf of Mexico OCS over the 10-year time period of this Programmatic EIS. The 

current target size of an offshore wind facility is approximately 500 megawatts (MW) (USDOE, 

NREL, 2012a and 2012b); however, projects between 350 and 500 MW or greater are possible. 

Using current technology and spacing requirements for offshore wind turbines, this equates to a 

minimum lease area of approximately 150 km2

 (58 square miles [mi2]; 37,000 acres [ac]) or 

approximately six OCS lease blocks. While an offshore wind energy lease for six OCS lease blocks 

or more is possible off the coast of Galveston, Texas, in the next 10 years, it is unlikely due to the

low cost of natural gas, which thereby reduces the economic incentive for wind energy development.

If an offshore wind energy lease is issued, it is assumed that the Port of Galveston would be 

utilized as the shore base to conduct site characterization activities due to current activity taking 

place within Texas State waters. Based on the duration of time per G&G event related to wind 

energy, up to one service vessel is projected to be utilized because the distance to shore is minimal 

and the survey vessels will likely return to the shore base daily (USDOI, BOEM, 2014b).

The G&G activities for renewable energy could occur anywhere within the AOI. However, 

the potential geographic scope is likely to be limited for several reasons. Wind energy facilities 

currently are the only type of renewable energy facility considered in the GOM. Although offshore 

wind foundation designs are rapidly changing, the distance from shore for a wind facility generally is 

defined as the outward limit of its economic viability, which currently is approximately 46 km (25 nmi

[27 mi]) from shore or 40-m (131-ft) water depth. As a result, renewable energy projects are likely to 

occur only in a narrow band along the coast of Texas having sufficient wind resources.

Alternate Use of Existing Platforms

Alternate use of existing platforms on the OCS could be done for the following activities: 

research; education; recreation; support for offshore operations and facilities; telecommunication 

facilities; renewable energy; and offshore aquaculture. At this time, alternate use is not foreseeable 

within the 10-year time period. If alternate use of existing facilities is proposed, G&G events related 

to the specific use would be determined at that time, but likely will rely on historic G&G data for that 

site-specific location.

As previously discussed for all renewable energy-related G&G activities in the GOM, the 

shore bases and ports to be utilized are Galveston, Texas, and Amelia, Louisiana, with Fourchon, 

Louisiana, as an alternate because they currently are utilized for projects within close proximity to 

proposed activities.
Gulf of Mexico G&G Activities Programmatic EIS 3-9 

3.2.2.2 Projected Activity Levels

Table 3.2-3 summarizes the projected activity levels for G&G activities associated with 

renewable energy development over the 10-year time period; as stated above, BOEM assumes that 

up to one new wind energy lease could be issued in the Gulf of Mexico OCS over the 10-year time 

period. To estimate non-airgun HRG activity levels, BOEM assumed that geophysical surveys for 

shallow hazards and archaeological resources would be conducted at the same time using the finer 

line spacing required for archaeological resource assessment (30 m; 98 ft). Tie-lines would run 

perpendicular to the track lines at a line spacing of 150 m (492 ft), which would result in 925 km 

(575 mi) of non-airgun HRG surveys per OCS lease block. It would take approximately 150 hours to 

survey one OCS lease block. In addition, a 16-km (9.9-mi) cable route to shore was assumed for 

each state with a 300-m (984-ft) wide survey corridor, which would include approximately 8 km 

(5 mi) or 1 hour of survey per mile of cable. In order to survey an entire renewable energy area and 

potential cable route, non-airgun HRG surveys would have to be conducted by multiple vessels or 

over multiple years and potential cable routes.

The number of seafloor sampling/testing locations for geotechnical surveys was estimated by 

assuming that a sample would be collected at every potential turbine location. Spacing between 

wind turbines typically is determined on a case-by-case basis and is based on several projectspecific factors to minimize wake effect, including turbine size and rotor diameter (for 3 MW to 8 MW 

turbines, the rotor diameters range from about 100 m to 164 m [328 ft to 538 ft]). Offshore Denmark, 

a spacing of seven rotor diameters between units has been used. In the U.S., the Cape Wind 

project proposed a spacing of 6 to 9 rotor diameters. In some land-based settings, turbines are 

separated from each other by 10 rotor diameters. Based on this range in spacing for a 3.6-MW 

(110-m [361-ft] rotor diameter) turbine and a 5-MW (130-m [427-ft] rotor diameter) turbine, it would 

be possible to place 14 to 45 turbines in one OCS lease block. The sampling numbers in Table 

3.2-3 are based on the assumption that a seafloor sample would be collected at every potential 

turbine location in a Wind Energy Area, at a density of 14 to 45 turbines per OCS lease block. It is 

also projected that up to two bottom-founded monitoring buoys would be placed to collect metocean 

and meteorological data.

3.2.3 Marine Minerals Program G&G Surveys

Under Section 11 of the OCSLA, BOEM may authorize G&G exploration for non-energy 

marine minerals. Commercial G&G prospecting for marine minerals is regulated under 30 CFR part 

580 and requires authorizations from BOEM. State and local government-sponsored, 

noncommercial G&G prospecting for marine minerals for use in coastal restoration and public works 

projects require BOEM’s authorization. The G&G prospecting conducted by a Federal agency or 

their contractor does not require BOEM’s authorization.

Under Section 8(k) of the OCSLA, BOEM may authorize use of non-energy, marine minerals 

from the OCS. Authorizations for use of OCS marine minerals are by (1) a noncompetitive 

negotiated agreement, which can only be used for obtaining sand and gravel (or other sediment) for 

beach nourishment, coastal restoration, and public works projects partially or entirely funded by a 
3-10 G&G Activities and Proposed Action Scenario

Federal, State, or local government (implemented through program guidelines); or (2) a competitive 

lease sale in which any qualified person may submit a bid (30 CFR parts 581 and 582). BOEM’s 

marine minerals program (MMP) has historically implemented the combined authorities through the 

following four primary functions:

• authorizing G&G prospecting for OCS sand resources for Federal, State, and 

local government-sponsored public works projects;

• preparing noncompetitive leases and MOAs authorizing the use of OCS sand 

resources for beach nourishment and coastal restoration projects;

• managing and coordinating cooperative agreements, task forces, and working 

groups with local, State, and Federal partners; and

• sponsoring, funding, and partnering with stakeholders to conduct environmental 

evaluations and resource studies to support permitting, leasing, and stewardship 

of OCS sand resources.

Although there has been occasional interest, no competitive leasing for marine minerals has 

occurred, and BOEM does not anticipate any commercial prospecting for marine minerals in the 

GOM during the time period of this Programmatic EIS. Moreover, no prospecting for marine 

minerals other than sediment for coastal restoration or beach nourishment projects are anticipated 

on the OCS over the next few years. In general, most of the OCS marine minerals used in the GOM 

are associated with sand resources for coastal ecosystem restoration projects sponsored and 

funded by State and Federal agencies.

Until 2011, BOEM managed cooperative agreements with all five Gulf Coast States. 

Currently, BOEM only has such an agreement with Louisiana. Between 2005 and 2015, BOEM 

issued eight negotiated agreements along the Gulf Coast authorizing the use of OCS sand 

resources from borrow areas offshore Louisiana and Florida for barrier island restoration, hurricane 

damage protection, infrastructure protection, ecosystem restoration, and recreational beach 

nourishment projects. Much of the OCS sand used in these projects was identified through the 

cooperative agreement program between BOEM and the Gulf Coast States. Over the 10-year 

project period, BOEM anticipates that OCS marine minerals G&G actions will be associated with 

prospecting and noncompetitive leases with Federal, State, and local governments.

In all cases, the OCS sand will be utilized for projects in State waters or on State lands. 

These projects generally will be under the jurisdiction of the USACE, through civil works mandates 

or Section 10/404 regulatory authority. BOEM will not be the lead Federal agency but likely will 

serve as a cooperating agency in collaboration with the lead agency to ensure effective 

implementation of NEPA requirements and associated consultations. In these cases, BOEM will 

adopt the NEPA documentation prepared by the project proponent for the Federal action of the lease 

issuance.
Gulf of Mexico G&G Activities Programmatic EIS 3-11

3.2.3.1 Proposed Action Scenario

The suite of survey and tool types deployed for the renewable energy and marine minerals 

programs are very similar. The G&G surveys supporting the marine minerals program historically 

have occurred:

• under cooperative agreements where State researchers and other Federal 

agencies, funded by BOEM, identified and assessed potential offshore sand 

resources for use in public works projects (USDOI, MMS, 1999 and 2004); 

• under prospecting permits or authorizations; and 

• in support of noncompetitive leasing before and after dredging operations.

The general area where G&G prospecting, prelease site assessment, and on-lease 

bathymetric surveys in the GOM likely will occur over the 10-year time period is a relatively discrete 

area of the OCS inner shelf, with water depths of less than 25 m (82 ft) offshore Texas, Louisiana, 

Mississippi, Alabama, and the west coast of Florida where sand resources are present and within an 

economically feasible transport distance to shoreline restoration sites. The total area within which 

marine minerals program activities occur represents approximately 1.06 percent of the AOI covered 

by this Programmatic EIS. Though the U.S. fleet is generally limited to 30 m (98 ft) based on current 

hopper and cutterhead dredge configurations, technologies are available to dredge deeper but these 

have not been used on U.S.-flagged vessels and may require costly retrofits. Moreover, the cost for 

transporting sand located in offshore sand shoals and banks to shoreline project areas where it is 

placed for beach nourishment or coastal restoration projects is relatively expensive, causing coastal 

planners to use resources in areas closest to shore first.

Because BOEM, the USGS, USACE, and other State, local, and Federal entities have 

invested considerable resources over the past three decades toward identifying and delineating 

sand resources on the OCS, the location of beach-quality sand resources on the shelf is relatively 

well known, excluding some OCS areas offshore the west coast of Florida. This general knowledge 

further refines the spatial extent of anticipated marine minerals-related G&G activities because it 

removes much of the reconnaissance phase of G&G prospecting. Therefore, many surveys will be 

conducted at the design scale and within areas of previously identified sand resources.

The G&G surveys may occur during the following three distinct phases of a project, in order 

of occurrence: (1) initial reconnaissance level sand search; (2) pre-authorization or pre-leasing 

environmental review; and (3) borrow area monitoring before, during, and after dredging and 

construction.

Reconnaissance level sand search data often exist from previous projects, regional resource 

evaluation studies, or scientific research studies; therefore, new projects often begin at the designlevel phase. Additional geophysical surveys may be conducted at the borrow area (i.e., the location 

of the sand source that is being dredged) prior to and at regular intervals after dredging. These 
3-12 G&G Activities and Proposed Action Scenario

surveys are performed as conditions of BOEM’s authorization to use the OCS sediment resource. 

Previous environmental reviews would have considered, analyzed, and established the need for 

such monitoring surveys to monitor seafloor change in the vicinity of the borrow area. Typical 

surveys include pre- and post-construction bathymetric surveys in the borrow area and are used to 

document seafloor changes, determine volumes used, and validate environmental analyses.

Sand Search, Borrow Design, Site Characterization, and Site Clearance Geophysical Surveys

Site characterization and sand search (prospecting) geophysical surveys are undertaken to 

identify OCS sand resources and any environmental resources, cultural resources, and shallow 

hazards such as pipelines that may exist in potential borrow areas. Marine minerals prospecting 

surveys usually deploy the same suite of geophysical instruments that are used for archaeological 

surveys; therefore, a single survey effort often satisfies the needs for sand prospecting, identification 

of cultural resources and sensitive seafloor habitat, and identification of shallow hazards.

Typical survey deployments may involve single-beam echosounders (SBESs) (24 to 

400 kHz) or multibeam echosounders (MBESs) (50 to 400 kHz); side-scan sonar (usually 16 to 

1,500 kHz); marine magnetometers; and sediment profilers (compressed high-intensity radiated 

pulse [CHIRP] subbottom profiler [4 to 24 kHz]). On rare occasions, boomer subbottom profilers 

(300 to 3,000 hertz [Hz]) may be deployed. However, newer CHIRP systems are able to penetrate 

to comparable levels as the boomer with improved resolution, essentially eliminating the utility of 

boomers for marine minerals applications in the context discussed herein (USDOI, GS, 2014). In 

addition, the SBESs usually employed are above 200 kHz, and the lower frequency (12 to 240 kHz) 

instruments are only used in muddy environments where fluid mud layers develop within dredge 

areas (<5% of all surveys). Operating frequencies listed above are further described in Chapter 

3.3.1.1 and Table 3.3 2. Table 3.1-1 shows the types of G&G activities associated with the marine 

minerals program, and further descriptions of the surveys and equipment is included in Appendix F. 

Geophysical survey equipment usually is deployed from a single, relatively small (8 to 30 m 

[26 to 98 ft]), slow-moving (<5 knots [kn] [6 miles per hour; mph] survey speed) vessel. Because 

survey areas are small (3 to 10 km2 [1.2 to 3.9 mi2

]) relative to oil and gas and renewable energy site 

characterization surveys, they generally are completed in 1 to 3 days (which rarely, if ever, include 

work during non-daylight hours).

If preexisting regional scale sand resources data are not available (which is usually not the 

case in the GOM), an early phase of regional reconnaissance sand search is conducted to define 

and map sediment bodies and to characterize the surficial geology of potential sand resources. The 

initial surveys are used to ascertain if sediment resources are of a certain quality (i.e., texture, 

mineralogy, percent sand, color) and quantity to warrant further exploration. The surveys may be 

conducted with line spacing between 120 and 600 m (394 and 1,968 ft). During the reconnaissance 

phase, limited geological sampling by vibracores or surface grab samples may occur along seismic 

lines and are used to validate geophysical data interpretations. Table 3.1-1 shows the types of G&G 

activities associated with the marine minerals program.
Gulf of Mexico G&G Activities Programmatic EIS 3-13

Design-level surveys often are performed using the same instrumentation suite discussed 

previously once a relatively smaller area is identified as a promising borrow area target based on 

reconnaissance level or other preexisting sand resource data. Design-level surveys provide 

information on seafloor and sub-seafloor conditions, shallow hazards, infrastructure condition and 

location, archaeological resources, and sensitive benthic habitats. The data are often used to 

prepare a dredging plan to efficiently and economically obtain the needed sand volumes while 

minimizing adverse environmental impacts and avoiding existing infrastructure. Depending on the 

quality of the initial reconnaissance geophysical data, the data may also be used to refine the borrow 

area or determine horizontal and vertical continuity of sedimentary units (in which case, the survey 

may be subject to BOEM authorization).

Design-level surveys do not have a required line spacing for the full suite of instruments; 

however, because archaeological guidelines call for a 30-m (98-ft) line spacing for marine 

magnetometer surveys, the full suite usually is towed at this spacing. The surveys conducted for 

marine minerals site clearance employ marine magnetometers (in addition to the suite of tools 

discussed previously) to identify infrastructure and seafloor debris hazards within approximately 

10 m (33 ft) of the seafloor and should not be confused with shallow hazards surveys. Shallow 

hazards surveys are conducted in support of oil and gas development, as defined by NTL 2008-G05, 

that requires operators to employ geophysical tools with usable frequency content across the 

20- to 300-Hz band and are capable of penetrating the subsurface to at least 750 m (2,461 ft) below 

the seafloor to identify potential geological hazards such as faults and gas deposits.

Pre- and Post-Dredging Bathymetric Surveys

Bathymetric surveys that use SBESs (12 to 240 kHz) or MBESs (50 to 400 kHz) typically are 

performed at the borrow area, or within a subarea of the borrow area, before and at specified 

intervals after dredging. BOEM uses the surveys to monitor the location and volumes of sand 

dredging, ensure observance of stand-off distances, and monitor the morphologic evolution of sand 

bodies and borrow pits. If submerged cultural resources or sensitive benthic habitat and 

communities are in the immediate vicinity of dredging, side-scan sonar (16 to 1,500 kHz) may be 

deployed. Because survey areas are relatively small, bathymetric surveys generally are completed 

within 1 to 2 days. Operating frequencies listed above are further described in Chapter 3.3.1.1 and 

Table 3.3 2. Table 3.1-1 shows the types of G&G activities associated with the MMP.

Prospecting and Geological (Geotechnical) Sampling

Geological sampling is typically conducted by means of pneumatic vibracoring, jet probes, or 

grab sampling, and it is carried out to characterize the volume (footprint and thickness) and quality of 

a prospective sand body. Geotechnical sampling is most frequently done in connection with 

reconnaissance geophysical surveying but may occur at the design level as well. Of these 

techniques, vibracoring is the most common technique used to define the thickness and lateral 

extent of OCS sand bodies and to provide samples for borrow area sand compatibility and beach 

performance analysis. Table 3.1-1 shows the types of G&G activities associated with the marine 

minerals program, and further descriptions of the sampling equipment is included in Appendix F. 
3-14 G&G Activities and Proposed Action Scenario

Vibracoring generally uses a 7-centimeter (cm) (2.8-inch [in]) diameter core barrel mounted 

on a 1- to 4 m (3- to 13-ft) square platform or support assembly and penetrates sediments in the 

upper 3 to 13 m (10 to 43 ft) of the seafloor. A typical vibracore survey will obtain 10 to 25 cores 

(each approximately 6 m [20 ft] in length) within the AOI. Vibracoring may occur with diver and/or jet 

hose assistance.

Grab sampling penetrates less than 1 m (3.3 ft) below the seafloor and typically involves 

30 to 40 grabs within the AOI. Nearly all geotechnical sampling occurs from relatively small (7 to 

30 m [23 to 98 ft]) vessels, small work barges towed into place, or self-propelled lift boats.

Operators performing the range of geological sampling activity in support of the MMP have 

among their array of work boats those that are dynamically positioned (vessels that can 

automatically maintain position using propellers, rudders, and thrusters). Consequently, not all 

geological sampling includes bottom disturbance by anchoring. Approximately 25 percent of 

deployments for this sampling work could involve a boat having dynamic positioning capability. The 

majority of operational platforms, however, do require anchoring for short periods using relatively 

small anchors or, offshore Louisiana, spuds on small lift boats.

Because marine minerals’ geophysical exploration surveys employ the same suite of tools as 

cultural resources surveys and because data collected are used for cultural resources evaluations, 

sites for geological sampling are cleared prior to any seafloor-disturbing activities. In some cases, 

when geophysical surveying and geological sampling are done under a single mobilization, a project 

archaeologist clears potential sample locations in real time.

3.2.3.2 Projected Activity Levels

The marine minerals program identified beach nourishment and coastal restoration projects 

likely to require use of OCS sand resources over the next 10 years and employ some or all of the 

G&G techniques described previously. Because marine minerals G&G activity is embedded as a 

component of the coastal restoration projects, projected marine minerals leasing activity serves as a 

good proxy for estimating levels of G&G activity. Therefore, this proposed activity scenario is based 

on an examination of past trends in OCS G&G and leasing activity and anticipated OCS leasing 

requests. The activity scenario is spatially and temporally explicit; however, because activity beyond 

the next 2 to 3 years is difficult to accurately predict, this scenario is not intended to limit marine 

minerals G&G activity to the exact list of restoration projects used for scenario development. Tables 

3.2 4 and 3.2-5 summarize the projected activity levels for G&G activities associated with the marine 

minerals program over the 10-year period.

For each project listed, borrow area sand volumes are used as a proxy for calculating 

potential G&G activity levels; however, this analysis does not cover any activity associated with sand 

extraction except for sand search, design and clearance surveys, and dredging compliance 

bathymetry surveys. Note that G&G prospecting and design surveys have been completed for many 
Gulf of Mexico G&G Activities Programmatic EIS 3-15

of the Louisiana and Mississippi projects; therefore, only pre- and post-dredging surveys are 

considered for projects under this scenario.

Geophysical and Bathymetric Surveys

The activity level for geophysical activity in support of marine minerals is based on the 

following assumptions for two different survey types:

(1) sand search, borrow design, site characterization, and site clearance (including 

hazards and biological and cultural resources) geophysical surveys consist of a 

CHIRP subbottom profiler (4 to 24 kHz), marine magnetometer, swath or SBES 

(>200 kHz), and side-scan sonar (100 to 500 kHz) and assume a 30-m (98-ft) 

line spacing; and

(2) pre- and post-dredging bathymetric surveys assume a line spacing of 

approximately twice the water depth (line spacing is determined by swath width, 

which increases with depth).

The number and size of borrow areas across known projects vary substantially. In some 

cases, specific borrow areas have yet to be identified. Nourishment volumes and frequency are 

comparatively well-defined for the relevant time frame, except for potential use in critically eroding 

segments along the central west coast of Florida. Given a projected fill volume and assuming a 

typical cut depth (2.5 m [8 ft] for this case, with the exception of Florida where shallow limestone 

bedrock limits cut depth to approximately 2 m [7 ft]), the borrow area footprint can be estimated to 

calculate kilometers of survey line for each project. For these calculations, a borrow area footprint is 

assumed to be 0.3 km2 (0.12 mi2

) per 1 million cubic yards (yd3) of sand for each project. Based on 

instrument-dictated maximum survey speeds (<5 kn; 5.8 mph), a survey duration can be calculated 

from the estimated kilometers of survey line for each project. Projections were verified by comparing 

historical prospecting, pre-dredging, and post-dredging survey kilometers of line with what would 

have been estimated strictly from anticipated volumes.

In some cases, sand search surveys are designed to cover areas containing up to twice the 

volume of sand required for the associated restoration project so that areas identified for dredging 

avoidance due to sensitive habitat, archaeological buffers, or slight variations in sand quality will not 

result in the need to deploy a subsequent survey effort to meet target sand volumes. To account for 

this practice, this scenario employs a conservative multiplier of two, applied to each of the 

anticipated projects, effectively doubling the spatial and temporal G&G survey footprint for each 

project. Furthermore, because sand volumes in the borrow area often far exceed those that are 

actually excavated for the associated project, the remaining sand is often used for later projects 

where no new sand search or design-level surveys are required; however, this scenario anticipates a 

new survey for each project, further reinforcing the conservative nature of this scenario.

The marine minerals geophysical surveying scenario for the GOM includes approximately 

675 km (419 mi) of prospecting/design surveys over a cumulative duration of approximately 81 hours 
3-16 G&G Activities and Proposed Action Scenario

for the entire 10-year period of analysis and approximately 2,860 km (1,777 mi) of pre- and postdredging bathymetric surveys with a cumulative duration of approximately 345 hours for the entire 

period of analysis (Table 3.2-5). Broken down into 8-hour survey days, this equates to 

approximately 10 survey days over the project period (or 1 survey day per year) of 

prospecting/design surveys and 43 days over the project period (or 4.3 survey days per year) of 

bathymetry surveys. However, most surveys are 1 to 3 days (daylight only) in duration, so there will 

be years in which no prospecting/design surveys occur. This scenario does not include similar 

activities that may occur in State waters or prospecting conducted by other Federal agencies or their 

contractors on the OCS. Similarly, G&G surveys associated with connected actions such as 

monitoring of nearshore environmental resources or beach fill performance are not included.

Geological or Geotechnical Surveys

Approximately 10 events for 392 pneumatic vibracores, 5 events for 50 jet probes, and 

2 events for 90 grab samples are expected to occur in the AOI over the 10-year time period. The 

spatial distribution and timing are expected to be similar to that described for geophysical survey 

activity. It is assumed that approximately 8 to 10 vibracores per 1,000,000 yd3 target volume will be 

sampled for each project with the exception of Florida projects, which require approximately 

15 vibracores per 1,000,000 yd3 target volume due to State color matching and quality requirements. 

Based on historic efforts, approximately 12 vibracores are sampled per day. Effects from marine 

minerals geophysical explorations are short-term and minor. Total seafloor disturbance from all 

combined geophysical activities for 532 samples with an average disturbance of 0.018 m2 (0.194 ft2

) 

per sample would be under 10 m2 (107 ft2

) total.

Appendix F provides descriptions of the survey equipment.

3.3 IMPACT-PRODUCING FACTORS FROM THE PROPOSED ACTION

Table 3.2-6 summarizes scenario elements for the three program areas (oil and gas, 

renewable energy, and marine minerals) and Table 3.2-8 provides the sum of all proposed survey 

activities for all program areas. Based on the scenario, the following impact-producing factors have 

been identified for routine activities in the proposed action:

(1) active acoustic sound sources;

(2) vessel and equipment noise;

(3) vessel traffic;

(4) aircraft traffic and noise;

(5) stand-off distance;

(6) vessel discharges;

(7) trash and debris;

(8) seafloor disturbance; 

(9) drilling discharges; and

(10) entanglement.

The only impact-producing factor identified for accidental events is fuel spills. Table 3.3-1

summarizes the impact-producing factors with respect to the associated survey types and program 

areas.
Gulf of Mexico G&G Activities Programmatic EIS 3-17

3.3.1 Impact-Producing Factors for Routine Activities

3.3.1.1 Active Acoustic Sound Sources

Active acoustic sound sources included in the proposed action include airguns, boomers, 

sparkers, and CHIRP subbottom profilers; side-scan sonars; and MBESs. Table 3.3-2 summarizes

the characteristics of these sources. Appendix F provides detailed descriptions of the different 

survey types that use active acoustic sound sources. Detailed acoustic characteristics and 

assumptions for representative sources are discussed in Appendix D. Representative active 

acoustic sound sources were modeled to provide acoustic propagation of these sources and marine 

mammal exposures for the proposed level of activity during the 10-year time period of this 

Programmatic EIS (Appendix D).

As part of the development of this Programmatic EIS, BOEM’s senior staff recognized a 

need to identify, quantify, and analyze all active acoustic source operations that might occur during 

G&G activities. The ultimate goal was for this process to indicate which sources and activities, 

based on their potential to affect the environment, required thorough analysis in this Programmatic 

EIS and which sources and activities did not. BOEM created a Screening Out Team (ScOT) to 

examine the issue and make recommendations; the ScOT’s results and recommendations are 

provided in Appendix G. 

3.3.1.1.1 Airguns

Airguns would be used as seismic sources during deep-penetration seismic surveys for oil 

and gas exploration, and individual airguns would be used for some postlease HRG surveys of oil 

and gas leases. BOEM predicts that no survey using airguns would be used for renewable energy 

site assessment activities (Table 3.2-3) or for assessment of marine minerals sites (Table 3.2-5).

An airgun is a stainless steel cylinder filled with high-pressure air. An acoustic signal is 

generated when the air is released nearly instantaneously into the surrounding water. During 

seismic surveys seismic pulses are emitted at intervals of 5 to 30 seconds, and occasionally at 

shorter or longer intervals.

The acoustic characteristics of the representative airguns selected for modeling are 

discussed in Appendix D. Modeling was conducted to calculate incidental exposure levels for 

marine mammals from active acoustic sound sources associated with the proposed action 

(Appendix D). Although airguns have a frequency range from approximately 10 to 2,000 Hz, most 

of the acoustic energy is radiated at frequencies below 500 Hz. The amplitude of the acoustic 

impulse emitted from the source is equal in all directions, but airgun arrays do possess some 

directionality due to different phase delays between airguns in different positions within an array.

Individual airguns are available in a wide range of chamber volumes, from less than 5 in3 to 

more than 2,000 in3

, depending on the survey requirements. Airgun sources can range from a single 

airgun (for HRG surveys) to a large array of airguns (for deep-penetration seismic surveys). The 
3-18 G&G Activities and Proposed Action Scenario

volume of airgun arrays used for seismic surveys can vary from approximately 45 to 8,460 in3. For 

this Programmatic EIS, the following two airgun configurations and sizes were modeled 

(Appendix D), based on current usage in the GOM, and considered representative for potential 

future G&G seismic surveys in the GOM:

• Large airgun array (8,000 in3

) – This array was used to represent sound sources 

for deep penetration seismic surveys, including 2D, 3D narrow azimuth (NAZ), 

3D WAZ, and other variations.

• Small single airgun (90 in3

) – This array was used to represent sound sources for 

HRG surveys.

The modeling methods and justification are described in Appendix D. The large airgun 

array has dimensions of 48 by 15 m (157 by 49 ft) and consists of 6 subarrays, each with 12 airguns 

for a total of 72 airguns, and a separation distance of 9 m (30 ft) between subarrays. The volume of 

individual airguns ranges from 40 to 250 in3

. The depth below the sea surface for the array was set 

at 8 m (26 ft) for the large array. The small 90-in3 airgun had a tow depth of 4 m (13 ft).

Broadband source levels are 248 and 228 dB re 1 μPa at 1 m for the large and small airgun 

arrays, respectively (Table 3.3-2). The two airgun configurations differ in source level and frequency 

spectrum; large arrays generate sound with more energy at low frequencies due to the presence of 

large volume airguns. Different survey scenarios to represent the various survey types performed in 

the GOM were analyzed as well (Appendix D). Appendix F provides detailed descriptions of the 

survey types using airguns.

3.3.1.1.2 Non-Airgun (Electromechanical) HRG Sources

In non-airgun HRG surveys, a high-resolution boomer, sparker, or CHIRP subbottom profiler 

is used to delineate near-surface geologic strata and features. Typical survey deployments also 

include SBESs or MBESs and side-scan sonars, which often are towed on an autonomous 

underwater vehicle. These electromechanical sources may operate simultaneously with airguns 

during deep penetration seismic surveys. Boomer use in shallow water is rare for the Marine 

Minerals Program, since it provides a roughly 0.5- to 1-m (1.6- to 3.3-ft) resolution, and it is typically 

replaced with subbottom profile systems that have sufficient depth penetration and higher resolution 

(note that it was kept in the analysis because it may be used to examine ancient, sediment-filled, 

river channels in the future) and that, in Renewable Energy Program surveys, it is more commonly 

used.

Boomers generate short, broadband acoustic pulses that are useful for high-resolution, 

shallow penetration sediment profiling. Boomers are commonly mounted on a sled and towed off 

the stern or alongside a ship. The reflected signal is received by a towed hydrophone streamer. 

Sparkers provide seafloor profiles, but boomers were selected as a representative source for this 

Programmatic EIS because the acoustic impulses produced by both sources are similar. The 

CHIRP systems are used for high-resolution mapping of relatively shallow deposits and have less 
Gulf of Mexico G&G Activities Programmatic EIS 3-19

penetration than boomers; however, newer CHIRP systems are able to penetrate to levels 

comparable to boomers yet yield extraordinary resolution of the substrate (National Science 

Foundation and USDOI, GS, 2011). The MBESs emit brief impulses of medium- or high-frequency 

sound in a fan-shaped beam extending downward and to the sides of the ship, allowing bathymetric 

mapping of swaths of the seafloor. The SBESs may be used for seafloor mapping, but the boomer 

was selected as a representative source for this Programmatic EIS and is conservative from the 

standpoint of acoustic impacts. Further details regarding non-airgun HRG acoustic sound sources 

are provided in Appendix F. 

The acoustic characteristics of the modeled electromechanical sources are discussed in 

Appendix D and included a boomer as well as a suite of MBESs, side-scan sonars, and subbottom 

profilers. Electromechanical sources are considered mid- or high-frequency sources. They usually 

have one or two (sometimes three) main operating frequencies (Table 3.3-2). The frequency ranges 

for the representative sources used for modeling are 100 Hz to 10 kHz for boomers, 100 to 410 kHz 

for side-scan sonars, 4 to 24 kHz for CHIRP subbottom profilers, and 200 kHz for MBESs. For these 

sources, the acoustic energy emitted outside the main operating frequency band is negligible; 

therefore, these can be considered narrow-band sources. High-frequency electromechanical 

sources can be highly directive, with beam widths as narrow as a few degrees or less. Broadband 

source levels for the representative electromechanical sources analyzed in this Programmatic EIS 

range from 200 to 213 dB re 1 μPa at 1 m SPL (Table 3.3-2).

A BOEM-funded field verification study of electromechanical sound sources was conducted 

in 2012 and examined sound emissions from a subbottom profiler (Zykov and MacDonnell, 2013). 

The study measured sound emissions of a subbottom profiler in a shallow-water and a deepwater 

location and compared the field results with results of the modeling conducted specifically for the 

preparation of the Atlantic OCS Proposed Geological and Geophysical Activities: Mid-Atlantic and 

South Atlantic Planning Areas; Final Programmatic EIS (USDOI, BOEM, 2014b). Zykov and 

MacDonnell (2013) demonstrated for the locations where the field verification was conducted that 

the received levels and threshold radii were much less than previously thought. For 180 and 

160 dB re 1 μPa, the threshold radii were measured at 2 and 29 m (7 and 95 ft), respectively.

3.3.1.2 Vessel and Equipment Noise

3.3.1.2.1 Vessel Noise

Nearly all G&G activities in the proposed action scenario would be conducted from ships. 

The exception would be remote-sensing methods from aircraft and satellites, and some VSP 

surveys. The most extensive vessel activities are 2D and 3D seismic surveys for oil and gas, which 

could occur anywhere in the AOI. Vessels conducting G&G surveys or sampling for renewable 

energy would be operating at specific sites (consisting of one or more OCS lease blocks) in water 

depths less than 40 m (131 ft) and along potential cable routes to shore. Vessels conducting G&G 

surveys or sampling for marine minerals would be operating at specific borrow sites in water depths 

less than 30 m (98 ft). Nearly all marine minerals geotechnical sampling occurs from relatively small 

(7 to 30 m [23 to 98 ft]) vessels, small work barges towed into place, or self-propelled lift boats.
3-20 G&G Activities and Proposed Action Scenario

Vessel noise is one of the main contributors to overall noise in the sea (National Research 

Council [NRC], 2003a). The G&G survey vessels would contribute to the overall noise environment 

by transmitting noise through air and water. Vessel noise is a combination of narrow-band (tonal) 

and broadband sound (Richardson et al., 1995). Tones typically dominate up to approximately 

50 Hz. The majority of broadband sound energy is restricted to frequencies below 100 to 200 Hz, 

but broadband sounds may include sound energy at frequencies as high as 100 kHz.

The primary sources of vessel noise are the propeller and machinery. Ship-generated noise 

at frequencies below 50 Hz is dominated by sound produced by propeller cavitation, which results 

from high thrust loading and non-uniform inflow of water into a propeller (Okeanos, 2008). Some 

propellers in service may produce a high-pitched noise, often referred to as propeller singing. This 

sound usually is a clear harmonic tone within the practical frequency range of approximately 10 to 

1,200 Hz, although the audible range of singing could be as high as 12,000 Hz (HydroComp, Inc., 

2003).

Primary sources of machinery noise include diesel-powered propulsion engines and ship 

service engines (Okeanos, 2008). Other sources of noise include auxiliaries, flow noise from water 

dragging along the hull, and bubbles breaking in the wake (Richardson et al., 1995). Propeller 

cavitation usually is the dominant noise source. The intensity of noise from service vessels is 

roughly related to ship size and speed. Large ships tend to be noisier than small ones, and ships 

underway with a full load (or towing or pushing a load) produce more noise than unladen vessels. 

For a given vessel, relative noise tends to increase with increased speed. Ship noise radiates 

asymmetrically, with stern aspect noise levels higher than bow aspect levels by 5 to 10 dB (Mckenna 

et al., 2012). Broadband source levels for most small ships (a category that would include seismic 

survey vessels and support vessels for drilling of COST wells or shallow test wells) are anticipated to 

be in the range of 170 to 180 dB re 1 μPa at 1 m (Richardson et al., 1995). Broadband source levels 

for smaller boats (a category that would include survey vessels for renewable energy and marine 

minerals sites) are in the range of 150 to 170 dB re 1 μPa at 1 m (Richardson et al., 1995).

Noise levels from project-related survey and survey support vessel traffic would be spatially 

restricted to discrete survey areas or OCS lease blocks and relatively short term in duration. It is 

predicted that additional vessel traffic will contribute to elevated local ambient noise levels during 

surveys; however, it is expected that these levels would dissipate quickly with distance from the 

source.

3.3.1.2.2 Equipment Noise Including Drilling Noise

Drilling of COST and shallow test wells would introduce additional underwater noise into the 

AOI from engines, generators, and other drilling rig equipment. The oil and gas scenario assumes 

that up to one COST well and up to two shallow test wells would be drilled in the planning areas 

during the 10-year time period of this Programmatic EIS. Neither the well locations nor the types of 

drilling rig are known at this programmatic stage. Jack-up rigs typically are used in water depths 

less than 100 m (328 ft) (USDOI, MMS, 2007b). Semisubmersibles are floating rigs that are used in 
Gulf of Mexico G&G Activities Programmatic EIS 3-21

water depths ranging from 100 to 3,000 m (328 to 9,842 ft) and can be moored or dynamically 

positioned (DP). Drillships are used in water depths greater than approximately 600 m (1,968 ft) and 

can also be moored or dynamically positioned (usually the latter).

Noise from drilling operations includes strong tonal components at low frequencies 

(<500 Hz), including infrasonic frequencies in at least some cases (Richardson et al., 1995). 

Machinery noise can be continuous or transient and can be variable in intensity. Noise levels vary 

with the type of drilling rig and water depth. Drillships produce the highest levels of underwater 

noise because the hull containing the rig generators and drilling machinery is well coupled to the 

water. In addition, DP drillships use thrusters to maintain position and are constantly emitting engine 

and propeller noise. The noise levels produced by DP vessels largely depend on the level of 

thruster activity required to keep position, and therefore will vary based on environmental site 

conditions and operational requirements. Representative source levels for DP vessels range from 

184 to 190 dB re 1 μPa, with a primary amplitude frequency below 600 Hz (Kyhn et al., 2011; 

Blackwell and Greene, 2003; McKenna et al., 2012). Jack-up rigs are at the other end of the 

spectrum because they are supported by metal legs with only a small surface area in contact with 

the water, the drilling machinery is located on decks well above the water, and there is no propulsion 

noise. Semisubmersibles are intermediate in noise level because the machinery is located well 

above the water, but the pontoons supporting the structure have a large surface area in contact with 

the water. Richardson et al. (1995) noted that broadband source levels for semisubmersible rigs 

have been reported to be approximately 154 dB re 1 μPa. Drilling operations would be supported by 

crew boats, supply vessels, and helicopters traveling between the drilling rig and the shore base. 

Support vessels usually make a few round trips per week, and helicopters typically make one round

trip per day (Table 3.2-7).

3.3.1.3 Vessel Traffic

The G&G activities in all three program areas involve vessel traffic. All of the vessels 

involved in G&G activities would operate out of shore bases. Ports and shore bases serve as 

launching points for the structures, equipment, supplies, and crew that serve the offshore G&G 

industry. In addition to providing berthing space, fuel, and supplies, the shore bases may provide 

products and services such as engine repair, electric generators, chains, gears, tools, pumps, 

compressors, and a variety of other tools and equipment.

Vessels conducting 2D, 3D, 4D, and WAZ seismic airgun surveys are the largest vessels 

and would account for most of the vessel line miles included in the proposed action. Estimated line 

miles for these four survey types total 2,469,030 line nmi (2,841,309 mi; 4,572,644 km) (Table 

3.2-6). These surveys could occur anywhere within the planning areas; however, roughly 64 percent 

of the surveys are expected to take place in the CPA, 27 percent in the WPA, and the remaining 

9 percent in the EPA (Table 3.2-1).

Vessels conducting G&G surveys for oil and gas exploration would predominantly operate in 

water depths of 40 m (131 ft) or more on large survey prospect areas and for extended periods of 
3-22 G&G Activities and Proposed Action Scenario

time. Vessels conducting G&G surveys or sampling for renewable energy would be smaller and 

would operate at specific sites (consisting of one or more OCS lease blocks) in water depths less 

than 40 m (131 ft) and along potential cable routes to shore. Similarly, vessels conducting G&G 

surveys or sampling for marine minerals would be operating at specific borrow sites in water depths 

less than 30 m (98 ft). Survey vessels for renewable energy and marine minerals projects are 

expected to make daily round trips to their shore base, whereas the larger seismic vessels can 

remain offshore for weeks or months. Additionally, combined marine mineral-associated vessel 

traffic would be approximately 53 days total, i.e., 10 survey days for prospecting/design surveys and 

43 days for bathymetry surveys.

3.3.1.3.1 Surveys for Oil and Gas Exploration

Seismic survey vessels used for deep-penetration seismic airgun surveys typically are 60 to 

90 m (197 to 295 ft) long for 2D surveys and 80 to 90 m (262 to 295 ft) long for 3D, 4D, and WAZ 

surveys. The 3D, 4D, and WAZ surveys usually require larger vessels because there is more 

equipment to be towed. Survey vessels for 2D, 3D, 4D, and WAZ surveys are likely to remain 

offshore for most, if not all, of the survey duration. The larger ships used for seismic surveys 

typically are foreign-flagged vessels that may mobilize from ports outside the AOI, but they may 

periodically travel to a shore base in the AOI for servicing. Typical towing speed during a survey is 

4.5 kn (5.2 mph). These surveys could occur anywhere within the planning areas, with 24-hour 

operations that may continue for weeks or months, depending on the size of the survey. Seismic 

survey vessels may transit into the GOM and stay within the survey area for the duration of the 

survey with no port calls. Therefore, while these survey vessels contribute a large percentage of the 

total vessel line miles over the 10-year time period, the majority of the line miles are at slow vessel 

speeds and likely represent only a small portion of vessel transits between offshore and shore bases 

(Table 3.2-7). As such, most supply runs, crew transfers, and refueling must be done with smaller, 

faster support vessels and helicopters. The smaller vessels are classified as service vessels in the 

impact-producing factor analysis and include supply ships, crew boats, fuel boats, USCG boats, and 

guard vessels. Deep penetration seismic airgun surveys conducted in association with a platform or 

drill ship (e.g., VSP and SWD) are shorter in duration, and while they may use typical 2D or 3D 

vessels, more commonly a supply vessel or similar platform (approximately 30 to 60 m in length) is 

used for drilling-based surveys (Table 3.2-6). These surveys typically do not require any service 

vessels due to the shorter duration and association with a drilling platform.

The proposed action scenario for oil and gas (Table 3.2-8) includes 108,693 mi (174,924 line 

km) of HRG surveys; 149,800 mi (241,080 line km) of 2D streamer surveys; 16,962 mi (27,298 line 

km) of VSP surveys; 2,319,230 mi (3,732,439 line km) of 3D, 4D, and WAZ streamer surveys; and 

8,120 mi (13,068 line km) of CSEM surveys, for a total of 2,602,805 mi (4,188,809 line km). 

Assuming a vessel speed of 4.5 kn (5.2 mph), these surveys would represent approximately 

502,569 hours (20,940 days) of active seismic data acquisition. This estimate does not include 

transit times; non-acquisition periods (e.g., mobilization, testing, turns, and ramp-ups); downtime for 

weather, mitigation, and mechanical and regular services; data re-acquisition time; or multiple vessel 

components of a survey. Therefore, to take into account the full vessel activity required to assess 
Gulf of Mexico G&G Activities Programmatic EIS 3-23

vessel traffic as an impact-producing factor, the non-active and active seismic acquisition time is 

considered a survey “event.” A survey event takes into account all vessel and aircraft activities 

necessary to complete a seismic survey from beginning to end. Seafloor sampling for oil and gas 

exploration includes up to 100 CPTs, 795 corings, 1 grab sample, 2 drill test wells, and up to 

1 COST well. Like the seismic surveys, the vessels and time required to complete sampling 

activities are considered as a whole for each event.

These surveys and sampling events may be supported by service vessels operating from 

ports along the Gulf Coast, but service vessel support is not a requirement. For this analysis, seven 

potential deepwater shore bases were identified: Houston, Texas; Corpus Christi, Texas; 

Beaumont, Texas; Galveston, Texas; New Orleans, Louisiana; Mobile, Alabama; and Tampa, 

Florida. The ports were selected based on their geographic proximity to the AOI, locations named in 

permit applications for G&G activities, and the availability of adequate support facilities that could be 

used by G&G survey and support vessels.

It is impossible to characterize a typical seismic survey (International Association of Oil & 

Gas Producers, 2011) due to the variability in survey design, implementation, and operating 

conditions. However, based on information from operators in the GOM and from lease sale EISs 

(e.g., USDOI, BOEM, 2013c and 2013d), some generalities were applied to develop vessel traffic 

statistics (Tables 3.2-6 and 3.2-7) as part of this impact-producing factor assessment. Assumptions 

for each oil and gas survey type are as follows:

• average duration for a survey vessel at sea without accessing a port for 2D, 3D, 

4D, and WAZ survey vessels is 10.5 months; 

• average duration for a survey vessel at sea without accessing a port for all other 

surveys and sampling is less than 1 month; 

• average duration of a service vessel at sea without accessing a port is 14 days; 

• number of crew changes is based on a 5-week rotational schedule with change 

out of personnel every 2.5 weeks to achieve 50 percent crew overlap; and

• 90 percent of crew changes on all deep-penetration seismic airgun surveys are 

done via helicopter while 10 percent are done with vessels.

Based on these assumptions and the projected level of survey activity (Table 3.2-6), an 

estimated 993 transits to or from shore will be made by the survey vessels and 19,689 transits will 

be made by service and support vessels for oil and gas surveys (Table 3.2-7). An estimated 

7,497 helicopter trips will be required to support crew changes on active seismic surveys.

3.3.1.3.2 Renewable Energy Surveys

Vessels conducting G&G surveys or sampling for renewable energy would operate mainly at 

specific sites (consisting of one or more OCS lease blocks) in water depths generally less than 40 m 
3-24 G&G Activities and Proposed Action Scenario

(131 ft) and along potential cable routes to shore. As previously discussed (Chapter 3.2.2), 

renewable energy is likely to occur only offshore southeast Texas. While it is recognized that 

24-hour surveys occur for renewable energy surveys in the Atlantic Ocean, typically in the GOM, the 

vessel would return to its shore base daily. Therefore, for the purposes of this assessment the 

following was assumed:

• all surveys will work an 8- to 12-hour offshore shift requiring 1 daily transit 

between the port and the survey site;

• the average number of days required to complete a survey will be used in 

calculating the number of transits; and

• survey vessels on site will operate at slow speeds but may increase speed during 

transit.

In nearshore waters, non-airgun HRG surveys would be conducted by a single small (<23 to 

30 m [75 to 98 ft]) vessel moving at less than 5 kn (6 mph). Geotechnical surveys for renewable 

energy sites are expected to be conducted from a small barge or ship of a similar size.

While there are no renewable energy projects planned in OCS waters of the GOM, for the 

purposes of this analysis, the renewable energy scenario includes 5,587 km (3,472 mi) and 

931 hours (assuming 6 km/hr [4 mi/hr]) of non-airgun HRG surveys (Table 3.2-8). Assuming that 

non-airgun HRG survey vessels would operate on 8-hour working days, the scenario would require 

116 active survey days. Five survey vessel transits are estimated (Table 3.2-6). However, survey 

vessels may return to port daily, depending on site location and vessel type.

Included in the renewable energy scenario are a maximum of 810 geotechnical sampling 

locations where cone penetrometer testing, geologic coring, and grab sampling would be conducted. 

There are nine projected survey events necessary to complete this sampling scenario.

Two projected bottom-founded monitoring buoy placements are included in this scenario. 

Based on the average duration of these activities and the presumed daily transits, there are an 

additional 34 round-trip vessel transits anticipated for the renewable energy geological and buoy 

placement surveys. Vessel trips associated with renewable energy areas would use existing ports in 

southeast Texas.

3.3.1.3.3 Marine Minerals Surveys

For non-airgun HRG surveys of sand source areas, geophysical survey equipment typically 

is deployed from a single vessel (<20 to 30 m [66 to 98 ft]) long, moving at approximately 4.5 kn

(5.2 mph). Surveys are likely to focus on prospective borrow sites (3 to 10 km2 [1.2 to 3.9 mi2

]) or 

reconnaissance areas (1 to 3 OCS lease blocks), and each survey is assumed to require 3 to 

7 operational days for completion. Vessels are assumed to operate on site for 8 hours per day and 

return to the shore base at the end of each day.
Gulf of Mexico G&G Activities Programmatic EIS 3-25

The marine minerals scenario includes approximately 673 km (418 mi) of non-airgun HRG 

prospecting surveys, 1,155 km (718 mi) of non-airgun HRG pre-lease/design surveys, and 1,706 km 

(921 nmi; 1,060 mi) of on-lease HRG surveys (Table 3.2-5). Across all geophysical survey activities, 

the maximum activity level is estimated at 3,534 km (2,196 mi); this is the equivalent of 

approximately 424 hours (Table 3.2-5) of surveying across 8-hour operational survey days. Given 

the projected number of surveys, the scenario would require 53 to 126 vessel round trips.

Nearly all geotechnical sampling occurs from relatively small vessels (approximately 20 m 

[66 ft] in length) or from work barges towed into place. A typical survey would last 1 to 5 days (Table 

3.2-6). The marine minerals scenario includes a maximum of 90 grab samples, 50 jet probes, and 

392 pneumatic vibracoring deployments (Table 3.2-4). Seventeen geotechnical sampling surveys 

are projected for the period, and given the average duration of the specific survey types, an 

estimated 64 round-trip vessel transits would be associated with these surveys. Vessel trips 

associated for marine minerals activities would be divided among several existing ports in Texas, 

Louisiana, Alabama, and Florida. Depending on the location of the marine mineral area, the surveys 

could operate from one of the larger ports analyzed in this Programmatic EIS (i.e., Houston, Corpus 

Christi, Galveston, Beaumont, New Orleans, Mobile, or Tampa) or any number of smaller ports 

along the coast, depending on what is convenient.

3.3.1.4 Aircraft Traffic and Noise

BOEM anticipates that only one aeromagnetic survey may be conducted in the AOI during 

the time period covered by this Programmatic EIS. The survey would be conducted by fixed-wing 

aircraft flying at speeds of approximately 135 kn (155 mph) (Reeves, 2005). Based on aeromagnetic 

datasets posted by Fugro Gravity and Magnetic Services (2012) for the northern GOM, most 

offshore aeromagnetic surveys are flown at altitudes between 61 and 152 m (200 and 499 ft) and 

collect 9,321 to 37,284 line mi (15,000 to 60,000 line km) of data. Line spacing varies depending on 

the objectives, but typical grids are 0.5 × 1.0 mi or 1.0 × 1.0 mi (0.8 x 1.6 km or 1.6 x 1.6 km). A 

broad-scale survey may be flown at higher altitudes (e.g., 305 m [1,001 ft]) and use wider line 

spacing (e.g., 4 × 12 mi or 8 × 24 mi [6 x 19 km or 13 x 39 km]). A fixed-wing aircraft typically 

acquires 12,428 line mi (20,000 line km) of useful data per month (Reeves, 2005). Therefore, it is 

expected that a typical aeromagnetic survey may require 1 to 3 months to complete. Based on the 

scale of aeromagnetic surveys that have been conducted in the northern GOM, an individual survey 

probably would cover less than 10 percent of the AOI.

Helicopters are used extensively in the offshore industry throughout the GOM. Helicopters 

are a potential source of aircraft noise during all G&G activities in the GOM and are most heavily 

used for personnel transport in vessel- and platform-based seismic surveys that stay on site for 

extended periods. The Helicopter Safety Advisory Conference recommended practice states that 

helicopters should maintain a minimum altitude of 750 ft (229 m) while in transit offshore and a 

maximum of 500 ft (152 m) while working between platforms and drilling rigs (Helicopter Safety 

Advisory Conference, 2010). These helicopters also follow FAA Minimum Altitudes over “coastal 

game reserves” (bird strike issues), cruising altitudes for easterly and westerly headings, altitude 
3-26 G&G Activities and Proposed Action Scenario

restrictions over certain offshore fields, and the operators' contractual guidelines. These helicopters 

follow these recommendations and restrictions as applicable and weather permitting. For this 

analysis, survey crew changes are assumed to be on a 5-week rotational schedule with a minimum 

50 percent overlap required for transferring personnel (i.e., a minimum of 1 flight every 2.5 weeks to 

change personnel). Based on the projected number of seismic surveys for oil and gas operations 

(Table 3.2-8), a minimum of 7,497 helicopter transits associated with the active G&G surveys is 

estimated for the 10-year period (Table 3.2-7). The oil and gas scenario assumes that up to one 

COST well and up to two shallow test wells would be drilled in the planning areas during the time 

period of this Programmatic EIS. It is expected that drilling activities would be supported by a 

helicopter making one round trip daily between the drilling rig and shore base. Neither the well 

locations nor the location of potential helicopter shore bases are known at this programmatic stage.

Helicopters and fixed-wing aircraft generate noise from their engines, airframe, and 

propellers. The dominant tones for both types of aircraft generally are below 500 Hz (Richardson 

et al., 1995). Richardson et al. (1995) reported that received SPLs (in water) from aircraft flying at 

altitudes of 152 m (499 ft) were 109 dB re 1 μPa for a Bell 212 helicopter and 101 dB re 1 μPa for a 

small fixed-wing aircraft such as a BN Islander aircraft. Helicopters are approximately 10 dB louder 

than fixed-wing aircraft of similar size (Richardson et al., 1995). Penetration of aircraft noise into the 

water is greatest directly below the aircraft; at angles greater than 13° from the vertical, much of the 

sound is reflected and does not penetrate into the water (Richardson et al., 1995). The duration of 

underwater sound from passing aircraft is much shorter in water than air; for example, a helicopter 

passing at an altitude of 152 m (499 ft) that is audible in air for 4 minutes may be detectable 

underwater for only 38 seconds at 3-m (10-ft) depth and for 11 seconds at 18-m (59-ft) depth 

(Richardson et al., 1995).

3.3.1.5 Stand-Off Distance

The proposed action includes extensive 2D and 3D surveys involving towed-streamer arrays. 

The scenario includes 149,800 line mi (241,080 line km ) of 2D streamer surveys; 2,319,230 line mi

(3,732,439 line km) of 3D streamer, 4D, and WAZ surveys; and 8,120 line mi (13,068 line km) of 

CSEM surveys (Table 3.3-8). These surveys could occur anywhere within the planning areas.

Vessels towing streamers during 2D, 3D, 4D, and WAZ seismic surveys follow pre-plotted 

track lines and have limited maneuverability during data acquisition. Accordingly, seismic vessels 

typically are accompanied by an escort vessel, which is used to scout the route ahead; identify 

hazards such as adverse currents, vessel traffic, or fishing equipment; and ensure that other vessels 

do not cross over or interfere with the equipment being towed.

For safety and security reasons, survey operators attempt to keep an area around the source 

vessel and its towed-streamer arrays clear of other vessel traffic and marine hazards that could 

result in a space-use conflict or interaction with other vessels. For the proposed action, this is 

defined as the “stand-off distance.” Depending on the survey and region, other names for this area 

include separation distance, fisheries exclusion zone, vessel clearance zone, or safety zone. The 
Gulf of Mexico G&G Activities Programmatic EIS 3-27

size of the stand-off distance that would be maintained around a source vessel and its towedstreamer arrays varies depending on the array configuration. A typical stand-off distance would be 

approximately 8.5 km (4.6 nmi; 5.3 mi) long and 1.2 km (0.6 nmi; 0.7 mi) wide, covering a total of 

1,021 ha (2,523 ac) of the sea surface. With the source vessel moving at speeds of approximately 

4.5 kn (5.2 mph), the length of time that any particular point would be within the stand-off distance 

would be approximately 1 hour.

The stand-off distance is an area monitored by a seismic survey operator and has no formal 

status or designation by the USCG. Prior to conducting a seismic survey, operators would submit 

information to the local USCG office and the local Harbormaster for issuance of a Local Notice to 

Mariners. The Local Notice to Mariners would specify the survey dates and locations as well as the 

recommended avoidance requirements. The wording of these notices is general (e.g., “a wide berth 

is urged”). All vessels operating with restricted maneuverability are required to carry the lights and 

signals described in Rule 27 of International Regulations for Preventing Collisions at Sea 

(COLREGS). Towed streamers are marked with an orange buoy equipped with a flashing light and 

radar reflector.

3.3.1.6 Vessel Discharges

Operational waste generated from vessels associated with the proposed action includes 

bilge and ballast waters, trash and debris, and sanitary and domestic wastes. Bilge water is water 

that collects in the lower part of a ship; it may be contaminated by oil that leaks from the machinery 

within the vessel. The discharge of any oil or oily mixtures of greater than 15 parts per million (ppm) 

is prohibited under 33 CFR § 151.10. Ballast water is used to maintain the stability of the vessel. 

Generally, ballast water is pumped into and out of separate compartments and is not contaminated 

with oil. In March 2012, the USCG issued Ballast Water Discharge Standards enumerating the 

requirements for the management of ballast (33 CFR part 151 subpart D); additionally, USCG 

regulations specify certain technologies be applied on vessels for treatment of ballast water prior to 

discharge. The U.S. Environmental Protection Agency (USEPA) provides National Pollutant 

Discharge Elimination System (NPDES) permit coverage for ballast water from commercial vessels 

of all sizes through the Final 2013 Vessel General Permit, which only covers NPDES permits for 

incidental discharges from commercial vessels greater than 79 ft (24 m) in length. The changes are 

included in the USEPA’s Final 2013 Vessel General Permit and the Final 2014 Small Vessel General 

Permit, which provides NPDES permit coverage for discharges incidental to the normal operation of 

nonmilitary, nonrecreational vessels less than 79 ft (24 m) (i.e., “small vessels”) operating in a 

capacity as a means of transportation.

3.3.1.7 Trash and Debris

Marine debris (here termed trash and debris) is defined as any persistent solid material that 

is manufactured or processed and directly or indirectly, intentionally or unintentionally disposed of or 

abandoned into the marine environment (USDOC, NOAA, 2015b). Survey operations generate 

trash made of paper, plastic, wood, glass, and metal that could be accidentally lost overboard. Most 

trash is associated with galley and offshore food service operations. Occasionally, some personal 
3-28 G&G Activities and Proposed Action Scenario

items such as hardhats and personal flotation devices are accidentally lost overboard. Discarded 

trash and debris is a major form of marine pollution.

The most common materials that compose trash and debris are plastics, glass, metal, paper, 

cloth, rubber, and wood. Like plastics, glass, metal, and rubber are used for a wide range of 

products, and while they can be worn away or broken down into smaller fragments, they generally 

do not biodegrade entirely.

The types of objects most commonly encountered in offshore waters are plastic bags, 

wrappers, bottles, and cups; raw plastic pellets; synthetic rope; glass bottles; metal cans; lumber; 

and cigarette butts (Laist, 1996 and 1997; Barnes et al., 2009; Gregory, 2009). Factors that account 

for recent increases in trash and debris include unlawful disposal practices, proliferation of synthetic 

materials that are resistant to degradation in the marine environment, and increasing numbers of 

people using and disposing of more synthetic items (USDOC, NOAA, 2015b).

The discharge of trash and debris is prohibited (33 CFR §§ 151.51 through 151.77) unless it 

is passed through a comminutor (a machine that breaks up solids) and can pass through a 

25-millimeter (mm) (1-inch) mesh screen. Discharge of plastic is prohibited regardless of size. All 

other trash and debris must be returned to shore for proper disposal with municipal and solid waste.

The USCG and USEPA’s regulations require operators to become proactive in avoiding 

accidental loss of solid waste items by developing waste management plans, posting informational 

placards, manifesting trash sent to shore, and using special precautions such as covering outside 

trash bins to prevent accidental loss of solid waste. In addition, over the last several years, 

companies operating offshore have developed and implemented trash and debris reduction and 

have improved handling practices to reduce the amount of offshore trash that could be lost into the 

marine environment. Trash management practices include replacing Styrofoam cups and dishes 

with those made of paper and ceramic, recycling offshore trash, and transporting and storing 

supplies and materials in bulk containers when feasible. These practices have resulted in a 

reduction of accidental loss of trash and debris.

Under the proposed action, all authorizations for shipboard surveys would include guidance 

for trash and debris awareness as described in NTL 2015-BSEE-G03 (“Marine Trash and Debris 

Awareness and Elimination”). All vessel operators, employees, and contractors actively engaged in 

G&G surveys must be briefed on trash and debris awareness and elimination as described in the 

NTL. An applicant would be required to ensure that its employees and contractors are made aware 

of the environmental and socioeconomic impacts associated with trash and debris as well as their 

responsibilities for ensuring that trash and debris are not intentionally or accidentally discharged into 

the marine environment.
Gulf of Mexico G&G Activities Programmatic EIS 3-29

3.3.1.8 Seafloor Disturbance

Sources of seafloor disturbance in the proposed action include the following:

• seafloor sampling activities in all three program areas;

• placement of anchors, nodes, cables, sensors, or other equipment on or in the 

seafloor for various activities in the oil and gas program;

• COST well and shallow test drilling in the oil and gas program; and

• placement of bottom-founded monitoring buoys in the renewable energy 

program.

BOEM will require site-specific information regarding potential archaeological resources and 

sensitive benthic communities (including hard/live bottom areas, deepwater coral communities, and 

chemosynthetic communities) prior to approving any G&G activities involving seafloor-disturbing 

activities or placement of bottom-founded equipment or structures in the planning areas. BOEM will 

use this information to ensure that physical impacts to archaeological resources or sensitive benthic 

communities are avoided.

BOEM has designated specific benthic locations for avoidance in the planning areas, 

including high-density deepwater benthic communities and biologically sensitive topographic 

features. These areas for benthic disturbance avoidance include known hard/live bottom areas; 

chemosynthetic communities; known deepwater coral locations, including Lophelia and Oculina coral 

sites and deepwater coral HAPCs; deepwater MPAs; pinnacle trend features (Shelf Edge Banks 

such as the Flower Gardens); and archaeological sites. These benthic features and MPAs are 

discussed in Chapters 4.5.1 and 4.7.1. All authorizations for G&G surveys proposed within or near 

these areas would be subject to the review noted previously to facilitate avoidance. BOEM has 

developed specific buffer zones for sensitive benthic communities in the GOM.

For the renewable energy program, BOEM has issued “Guidelines for Providing 

Archaeological and Historic Property Information Pursuant to 30 CFR Part 585.” The July 2015 

revised guidelines specify that a site characterization survey must reliably cover any portion of the 

site that would be affected by seafloor-disturbing activities. The guidelines recommend avoidance 

as a primary mitigation strategy for objects of historical or archaeological significance. An applicant 

has the option to demonstrate through additional investigations that an archaeological resource 

either does not exist or would not be adversely affected by the seafloor-disturbing activities. While 

site characterization activities covered by these guidelines could identify other resource types (e.g., 

benthic communities), recommendations for conducting and reporting the results of other baseline 

collection studies (e.g., biological) would be provided by BOEM in separate guidelines, e.g., 

“Guidelines for Providing Benthic Habitat Survey Information for Renewable Energy Development.” 
3-30 G&G Activities and Proposed Action Scenario

3.3.1.8.1 Seafloor or Bottom Sampling Activities

The proposed action scenario includes seafloor sampling activities in all three program 

areas, including the following:

• up to 896 CPTs, coring, or grab samples in the oil and gas program;

• up to 810 CPTs, coring, or grab samples in the renewable energy program; and

• up to 90 grab samples, 50 jet probes, and 392 vibracores in the marine minerals 

program.

Collection of each sample is estimated to disturb an area of approximately 10 square meters 

(m2

) (108 square feet [ft2]), although the actual area of the core or grab extracted may be much 

smaller. If all of the samples (total of 2,238) in the proposed action scenario were collected, the total 

area of seafloor disturbed by bottom sampling is expected to be approximately 22,380 m2

(240,896 ft2

) (Table 3.2 8), which represents an extremely small percentage of the planning areas.

Sampling for oil and gas exploration would be conducted at specific OCS lease blocks where 

structures such as drilling rigs, platforms, or pipelines may be installed. The OCS lease blocks could 

be anywhere within the planning areas and cannot be predicted as there are many active oil and gas 

leases in the GOM.

Sampling for renewable energy projects would occur at specific sites consisting of one or 

more OCS lease blocks in water depths less than 40 m (131 ft) and along potential cable routes to 

shore. As discussed in Chapter 3.2.2.1, southeast Texas in the WPA has the highest potential for 

wind resources. These offshore areas would likely be where sampling would occur. No areas 

currently are being considered for hydrokinetic power.

Sampling activities for marine minerals would be conducted at specific sand resource borrow 

sites in water depths less than 25 m (82 ft). As discussed in Chapter 3.2.3.1, much of the marine 

minerals activity is expected to occur within existing borrow sites offshore Texas, Louisiana, 

Alabama, and the west coast of Florida. By design, the sampling locations are expected to be 

almost exclusively sand bottom.

3.3.1.8.2 Placement of Anchors, Nodes, Cables, and Sensors

Certain surveys in oil and gas exploration require placement of anchors, nodes, cables, 

sensors, or other equipment on or in the seafloor. Ocean bottom cable (OBC) and ocean bottom 

node (OBN) surveys, vertical cable surveys, CSEM surveys, and magnetotelluric surveys involve 

placement of sensors and anchors on the seafloor (Appendix F). Each of these activities would 

temporarily affect a small area of seafloor. After a survey is completed, the sensors are removed; 

anchors are removed or left in place (if biodegradable). The OCS lease blocks where these surveys 

would be conducted could be anywhere within the planning areas and cannot be predicted as there 
Gulf of Mexico G&G Activities Programmatic EIS 3-31

are many active oil and gas leases in the GOM. The total area of seafloor disturbed has not been 

calculated.

3.3.1.8.3 COST Wells and Shallow Test Drilling

The oil and gas scenario assumes that up to one COST well and up to two shallow test wells 

would be drilled in the planning areas during the time period of this Programmatic EIS. Locations for 

COST wells and shallow test wells are unknown.

The COST wells and shallow test wells would be drilled using conventional rotary drilling 

techniques. Seafloor disturbance would result from anchoring (if a moored drilling rig was used), 

placing a well template on the seafloor, and jetting the well. The area of seafloor disturbance varies 

with the type of rig chosen to drill a well, which depends primarily on water depth (USDOI, MMS, 

2007b). Jack-up rigs are used in shallow water and disturb approximately 1 ha (2.5 ac) for each 

location. Semisubmersibles can be operated in a wide range of water depths and disturb 

approximately 2 to 3 ha (5 to 7 ac), depending on the mooring configurations. In water depths 

greater than 600 m (1,968 ft), dynamically positioned drillships could be used; these drillships disturb 

only a very small area where the seafloor template and wellbore are located, approximately 0.25 ha 

(0.62 ac).

For this impact analysis, the area of seafloor disturbance is assumed to average 

approximately 2 ha (5 ac) per well. If the COST well and both shallow test wells in the proposed 

action scenario were drilled, the total seafloor disturbance would be approximately 6 ha (15 ac), or 

approximately 0.00001 percent of the AOI.

3.3.1.8.4 Bottom-Founded Monitoring Buoys

As part of the renewable energy program, lessees may install bottom-founded monitoring 

buoys. This Programmatic EIS assumes that lessees would choose to install buoys instead of 

meteorological towers. The buoys would be anchored at fixed locations and regularly collect 

observations from many different atmospheric and oceanographic sensors.

Monitoring buoys typically would be towed or carried on board a vessel to the installation 

location. Once at the location site, the buoy would be lowered to the sea surface from the deck of 

the transport vessel or placed over the final location and then the mooring anchor dropped. A boat 

shaped buoy in shallower waters of the planning areas may be moored with an all-chain mooring, 

while a larger discus type buoy would use a combination of chain, nylon, and buoyant polypropylene 

materials (USDOC, National Data Buoy Center, 2011). After installation, the transport vessel would 

remain in the area for several hours while technicians configure proper operation of all systems. 

Buoys typically take 1 day to install. Transport and installation vessel anchoring for 1 day is 

anticipated for these types of buoys. Decommissioning of buoys is essentially the reverse of the 

installation process.
3-32 G&G Activities and Proposed Action Scenario

The proposed action scenario includes two buoys that may be installed within the AOI during 

the time period of this Programmatic EIS. Anchors for boat- and discus-shaped buoys would have a 

footprint of approximately 0.56 m2 (6 ft2

) and an anchor sweep of approximately 3.4 ha (8.5 ac) 

(USDOI, BOEM, 2012). The larger anchor sweep area is used to estimate seafloor disturbance. If 

both of the monitoring buoys in the proposed action scenario were installed, the total seafloor 

disturbance would be approximately 6.8 ha (17 ac), or approximately 0.00001 percent of the seafloor 

area of the planning areas.

3.3.1.9 Drilling Discharges

The Oil and Gas Program scenario assumes that one COST well and two shallow test wells 

would be drilled in the planning areas during the time period of this Programmatic EIS. The COST 

wells are drilled using conventional rotary drilling techniques, which are the same as those routinely 

used for drilling oil and gas exploration and development wells. During the process, drilling fluid and 

cuttings are discharged, disperse in the water column, and accumulate on the seafloor (NRC, 1983; 

Neff, 1987; Neff et al., 2000). Shallow test wells will result in drilling fluid and cuttings discharges. 

The oil and gas exploration scenario estimates up to two shallow test wells in the AOI.

During the initial stage of drilling, a large-diameter surface hole is jetted a few hundred 

meters into the seafloor. An NPDES permit must be obtained from the USEPA in order to discharge 

drilling fluids and cuttings as well as any other possible produced waters (e.g., bilge, ballast, fire, and 

cooling water; sanitary and domestic waste; and deck drainage) that may be associated with COST 

well drilling (Chapter 1.6.11). At this stage, the cuttings and seawater used as drilling fluid are 

discharged onto the seafloor. A continuous steel pipe known as a surface casing is lowered into the 

hole and cemented in place. A blowout preventer (BOP) is installed to prevent water and 

hydrocarbons from escaping into the environment. Once the BOP is fully pressure tested, the next 

section of the well is drilled.

The marine riser is a pipe with special fittings that establishes a seal between the top of the 

wellbore and the drilling rig. After it is set, all drilling fluid and cuttings are returned to the drilling rig 

and passed through a solids control system designed to remove cuttings and silt so that the drilling 

fluids may be recirculated downhole. The drill cuttings, typically sand or gravel sized with any 

residual drilling mud attached, are passed through a cuttings dryer to decrease the retained drilling 

fluid on cuttings, and then discharged via the shale chute.

The typical drilling fluids in widespread use on the OCS are water-based fluids (WBFs) or 

synthetic-based fluids (SBFs). During well intervals when WBF systems are used, cuttings and 

adsorbed WBF solids are discharged to the ocean at a rate of 0.2 to 2.0 m3

/hr (Neff, 1987). 

Overboard discharge of WBF results in increased turbidity in the water column, alteration of 

sediment characteristics because of coarse material in cuttings, and elevated concentrations of 

some trace metals (NRC, 1983; Neff, 1987). In shallow environments, WBFs disperse rapidly in the 

water column immediately after discharge and quickly descend to the seafloor; in deeper water, 

however, fluids discharged at the sea surface are dispersed over a wider area (Neff, 1987).
Gulf of Mexico G&G Activities Programmatic EIS 3-33

The average exploration well in the GOM is approximately 3,674 m (12,054 ft) below mudline 

(USDOI, MMS, 2007b). Each well discharges approximately 7,000 to 9,700 bbl of WBF and 1,500 to 

2,500 bbl of cuttings (USEPA, 1993, 2000). Assuming an average of 2,000 bbl of cuttings and 

8,350 bbl of drilling fluid discharged per well, the total volumes for one COST well and two test wells 

would range from 2,000 to 6,000 bbl of cuttings and from 8,350 to 25,050 bbl of drilling fluid.

3.3.1.10 Entanglement

Lines, cables, and buoys deployed in the water present entanglement risks to marine wildlife, 

archaeological resources that stand proud of the bottom, and benthic communities. Specific to G&G 

activities in the GOM, acoustic buoy releases, tethered acoustic pingers, and nodal tethering lines 

pose an entanglement risk to marine mammals, sea turtles, and other marine life, and could impact 

archaeological resources through direct contact or by being dragged through an archaeological site. 

Although rare, entanglement has occurred in association with OBC and OBN surveys where rope or 

cable connections are used between nodes and with associated equipment (e.g., anchors and

buoys). The deployment of OBCs and OBNs is accomplished by a Remotely Operated Vehicle 

(ROV), by dropping nodes on a tether, or by laying cables off the back of a layout boat. The 

assemblage remains on the seafloor during the seismic survey and is retrieved at the completion of 

the survey. Not all surveys will have tethered nodes; however, a typical tethered survey can lay out 

more than 500 km (310 mi) of line for nodal surveys. According to BOEM (USDOI, BOEM, 2013e), 

risks of entanglement for pelagic organisms can be further minimized by implementing the following 

measures: (1) shortening acoustic buoy and tethered acoustic pinger lines to the shortest length 

practical; and (2) replacing tether rope lines less than 0.25 in (0.64 cm) in diameter with a thicker, 

more rigid tether line or modifying the line to increase the diameter and rigidity. BOEM also requires 

that if, upon retrieval, a cable becomes snagged, the operator must verify what is causing the snag, 

which could possibly minimize further damage to archaeological resources or benthic communities.

3.3.2 Impact-Producing Factors for Accidental Fuel Spills

Vessel fuel capacities generally depend on vessel size, which varies according to the nature 

of the survey (e.g., 3D surveys use larger vessels than 2D surveys). A large seismic survey vessel 

may carry between 6,447 and 12,108 bbl of fuel, including diesel and fuel oil (Polarcus, 2015). 

Smaller coastal vessels may carry several thousand gallons.

Vessels involved in G&G activities in the GOM could be involved in collisions or other 

accidents that result in a fuel spill. Spill size would depend on the type of vessel, the severity of the 

event, and whether the fuel storage is compartmentalized.

All G&G vessels are required to comply with USCG requirements relating to prevention and 

control of oil spills. Nevertheless, for the purposes of this analysis, a spill scenario was evaluated – 

a release of 1.2 to 7.1 bbl of diesel fuel caused by a vessel collision or an accident during fuel 

transfer. The volume is based on spill statistics from 2000 to 2009 developed by the Coast Guard 

(USDHS, CG, 2011b). During this period, there were 1,521 to 5,220 spills per year from vessels 

other than tankers and tank barges. Total annual spill volumes from these vessels ranged from 
3-34 G&G Activities and Proposed Action Scenario

2,200 to 10,807 bbl, resulting in average spill sizes ranging between 1.2 and 7.1 bbl. There were 

137 reported vessel collisions in the GOM from 2007 to 2014 (USDOI, BSEE, 2015a). Additionally, 

from 1964 to 2013, there were 1,823 reportable spills of 1 to 4 bbl, for a total spill volume of 

4,253 bbl, related to oil and gas activities on the OCS (USDOI, BSEE, 2015b).

The likelihood of a fuel spill during seismic surveys or other G&G activities is expected to be 

remote. For example, in their programmatic analysis of impacts associated with seismic research, 

the National Science Foundation and USDOI, GS (2011) noted that there has never been a recorded 

oil/fuel spill during more than 100,000 km (54,000 nmi; 62,137 mi) of previous National Science 

Foundation-funded seismic surveys.

The potential for impacts from a 1.2- to 7.1-bbl diesel fuel spill would depend on the location 

of the spill, meteorological conditions at the time, and the speed with which cleanup plans and 

equipment could be employed. Diesel fuel is a refined petroleum product that is less dense than 

water. It may float on the sea surface or be dispersed into the water column by waves. It is 

assumed that spilled fuel would rapidly spread to a layer of varying thickness and break into narrow 

bands, or windrows, parallel to the wind direction. Diesel is a distillate of crude oil and does not 

contain the heavier components that contribute to crude oil’s longer persistence in the environment. 

Small diesel spills (500 to 5,000 gallons) usually evaporate and disperse within a day or less, even in 

cold water (USDOC, NOAA, 2015c); thus, there seldom is any oil on the surface for responders to 

recover. However, what is commonly referred to as “marine diesel” is often a heavier intermediate 

fuel oil that will persist longer when spilled. When spilled on water, diesel oil quickly spreads to a 

thin film of rainbow and silver sheens, except for marine diesel, which may form a thicker film of dull 

or dark colors (USDOC, NOAA, 2015c). A small proportion of the heavier fuel components may 

adhere to particulate matter in the upper portion of the water column and sink. Particulate matter 

contaminated with diesel fuel could reach the benthos within or outside the AOI, depending on spill 

location, water depth, ambient currents, and sinking rate.

3.4 CUMULATIVE ACTIVITIES SCENARIO

Cumulative effects (40 CFR § 1508.7) refers to impacts on the environment that result from 

the incremental increase in impact from the proposed action when added to other past, present, and 

reasonably foreseeable future actions regardless of what agency (Federal or non-Federal) or person 

undertakes such actions. Cumulative effects can result from individually minor but collectively 

significant actions taking place over a period of time.

Previous environmental analyses were reviewed to identify and characterize the nature of 

ongoing or proposed non-G&G activities as a basis for development of a cumulative activities 

scenario, focusing exclusively on activities with similar impacts and impact-producing factors to the 

proposed action and alternatives (e.g., USDOI, BOEM, 2012, 2013c, and 2013d; U.S. Department of 

the Navy, 2013). The identification of the cumulative activities that have similar impact-producing 

factors, as defined in Chapter 3.3.1, were presented in a matrix to correlate the proposed action 
Gulf of Mexico G&G Activities Programmatic EIS 3-35

impact-producing factors to the potential cumulative effect of past, present, and reasonably 

foreseeable actions (Table 3.4-1).

The resultant screening analysis identified potentially significant cumulative effects 

associated with the proposed action and defined the assessment goals as well as the resultant 

cumulative scenario, including activities classified under three major areas or components:

• OCS Program

− Oil and Gas Exploration and Development 

− Decommissioning

− Renewable Energy Development

− Marine Minerals Use

• Oil and Gas Activities in State Waters

− Oil and Gas Exploration and Development

− Decommissioning

• Other Major Factors Influencing the AOI

− Deepwater Ports

− Commercial and Recreational Fishing

− Shipping and Marine Transportation

− Dredged Material Disposal

− Existing, Planned, and New Cable Infrastructure

− Military Activities

− Scientific Research

− Dredging and Federal Channels

− Coastal Restoration Programs

− Mississippi River Hydromodification, Subsidence, and Drainage

− Extreme Climatic Events

− Climate Change and Sea-Level Rise

− Natural Oil Seeps

− Treasure Hunting/Looting

− Sport Diving
3-36 G&G Activities and Proposed Action Scenario

As outlined in Chapter 3.3.1, impact-producing factors have been identified in association 

with proposed G&G activities. Key G&G-related, impact-producing factors that could affect marine 

resources in the AOI include the following: (1) active acoustic sound sources; (2) vessel and 

equipment noise; (3) vessel traffic; (4) aircraft traffic and noise; (5) stand-off distance; (6) vessel 

discharges; (7) trash and debris; (8) seafloor disturbance; (9) drilling discharges; (10) entanglement; 

and (11) accidental fuel spills. These impact-producing factors have been compared to the impactproducing factors from each of the cumulative scenario components in order to focus the cumulative 

analysis on the activities that coincide spatially and temporally with the proposed action (Table 

3.4-1). The cumulative effect (additive or synergistic) can then be assessed for each resource to 

determine the incremental increase attributed to the proposed action (refer to Chapter 4).

This cumulative scenario establishes the geographic boundaries for the cumulative analysis 

by considering geographic areas occupied by migratory resources and affected institutional 

jurisdictions, and focusing on the distance that an impact may extend, as recommended by the CEQ 

(1997). The AOI includes all three of BOEM’s Gulf of Mexico OCS planning areas (i.e., Western, 

Central, and Eastern) and the State waters of Texas, Louisiana, Mississippi, Alabama, and Florida 

extending from the coastline (outside of estuaries) to the seaward extent of the planning areas 

(78 FR 27427). The inclusion of State waters considers that impacts from G&G surveys could affect 

resources in State waters. Because the AOI includes all waters of the GOM and not just those 

within BOEM’s jurisdiction, coupled with the understanding that G&G activities will not be occurring 

homogenously throughout the AOI, the geographic bounds for the cumulative analysis are 

reasonable. Figure 3.4-1 depicts, in a predictive manner, the projected spatial distribution of various 

cumulative scenario activity components based on existing activity and the assumption that spatial 

distribution trends would continue in similar locations.

The G&G activities have been ongoing in the GOM for at least the past 30 years, and it is 

reasonable to assume they will continue into the future; however, for the purpose of this 

Programmatic EIS, the cumulative analysis assesses a 10-year time period to coincide with the 

proposed action because it is not expected that G&G activities will have lasting effects or extend 

beyond the 10-year time period of this Programmatic EIS.

3.4.1 OCS Program

The impact-producing factors associated with OCS Program activities that coincide with the 

proposed action include vessel and equipment noise (including explosives use [decommissioning]), 

support vessel traffic, aircraft traffic and noise, stand-off distance, vessel discharges, trash and 

debris, seafloor disturbance, drilling discharges, and accidental fuel spills (Table 3.4-1). All G&G 

survey activities associated with the OCS Program are included in the proposed action; therefore, 

G&G activities are not included in the cumulative analysis but instead are addressed in the proposed 

action impact analysis.
Gulf of Mexico G&G Activities Programmatic EIS 3-37

3.4.1.1 OCS Oil and Gas Exploration and Development

Oil and gas activities in the GOM began in the 1950s and have undergone cyclical swings in 

activity levels (Adams et al., 2009). Most activities and resultant infrastructure such as oil and gas 

platforms and pipelines, are located within the CPA. The G&G survey activities, such as seismic 

surveys, have occurred throughout the WPA and CPA from the State water boundary to the 

Exclusive Economic Zone boundary (Schlumberger, 2015). Vessel traffic associated with oil and 

gas activities originated from several ports within the WPA and CPA. Due to recent growth of oil and 

gas development in deepwater areas of the GOM, oil and gas service activities for OCS operations 

have been centralized at Port Fourchon, Louisiana (Keithly, 2001). Currently, Port Fourchon 

services approximately 90 percent of all deepwater rigs and platforms in the GOM (USDOC, NOAA, 

2012). Consequently, a large percentage of supply, service, and construction vessel traffic 

associated with OCS activities is concentrated in waters offshore of this port. Within the northern 

GOM, oil and gas exploration and development activities were largely spatially limited to waters of 

the continental shelf; however, as OCS exploration and development technologies advanced, 

activities transitioned into shelf edge and deepwater environments. Within the southern GOM, 

beyond the U.S. Exclusive Economic Zone (and beyond the boundaries of the AOI), Mexico stands 

ninth in the worldwide ranking of conventional oil reserves with several fields offshore Campeche, 

Tabasco, and Tampico (Index Mundi, 2015). In December 2013, the U.S. Congress approved the 

U.S.-Mexico Transboundary Hydrocarbons Agreement (P.L. 113-67, the Bipartisan Budget Act of 

2013), which aims to facilitate joint development of oil and natural gas in part of the GOM.

BOEM (USDOI, BOEM, 2013c and 2013d) developed a cumulative activities scenario for oil 

and gas exploration and development in the three planning areas, estimating activity levels over a 

40-year period (2012 to 2051). Given the 10-year time period for the cumulative analysis in this 

Programmatic EIS, estimates developed for the 40-year period have been decreased by 75 percent. 

While this approach provides an approximation of activity levels for the period of interest, many 

factors may affect oil and gas exploration and development. Oil and gas activities are influenced, in 

the short term, by the economic environment, crude oil and natural gas prices, leasing activity, and 

vessel and drilling rig availability, among other factors. Consequently, the 10-year projections 

outlined in Table 3.4-2 represent approximations based on the 40-year projections; actual activity 

levels may vary from estimated levels. The majority of projected oil and gas activities would occur 

within the CPA (Table 3.4-2), followed by a reduced level of projected activities occurring in the 

WPA. The projected level of activities in the EPA is very small, representing all anticipated 

production from lands currently under lease in the EPA plus all anticipated production from future 

lease sales (Table 3.4-2). Detailed descriptions of deepwater (>305 m [1,000 ft]) production 

activities are included in a prior assessment of the physical impacts of installation and operation for 

various types of systems (USDOI, MMS, 2000). Typical effects from exploration (e.g., delineation 

wells and non-seismic) and development that coincide with the impact-producing factors from G&G 

activities can include noise from support vessels and aircraft (helicopters), drilling equipment, and 

pipeline and infrastructure placement (e.g., trenching). Underwater marine sounds associated with 

drilling operations are not particularly intense and include strong tonal components at low 

frequencies and infrasonic frequencies in at least some cases (Richardson et al., 1995; USDOI, 
3-38 G&G Activities and Proposed Action Scenario

MMS, 2000; Wyatt, 2008). Other sources of drilling-related sounds include riser rotation, DP 

thrusters, and ROV operations. Production wells are drilled using mobile offshore drilling units. The 

type of production platform installed will depend on the water depth and other factors, and may be 

fixed or floating; production also may be realized through use of subsea completions and associated 

pipelines (only in deep water).

Vessel traffic and associated discharges associated with oil and gas activities could occur, 

along with potential for accidental loss of trash and debris. Seafloor infrastructure associated with 

production would disturb the seafloor during installation and, to a lesser extent, from operation (e.g., 

drilling discharges). The area surrounding oil and gas activities would be precluded for use by other 

ocean users during certain activities. All activities could result in an accidental spill of diesel fuel. 

Table 3.4-1 outlines the impact-producing factors that coincide between G&G activities and oil and 

gas exploration and development activities.

3.4.1.2 Decommissioning

When an OCS lease expires or development and production operations cease, companies 

are obligated to decommission and remove their facilities (30 CFR § 250.1725(a)) and clear the 

seafloor of all obstructions (30 CFR § 250.1740). As of May 2, 2016, there were more than 

2,479 active production platforms in the GOM (USDOI, BSEE, 2016). Offshore facility 

decommissioning, including platform and caisson removal, typically uses one of two primary 

methods to sever structures attached to the seafloor: mechanical severance or explosive severance. 

Explosive severance utilizes specially designed bulk or shaped charges with specific properties to 

produce enough stress upon detonation to completely sever the bottom-founded components of a 

platform. Explosive charges generally are placed inside the platform legs or conductors 4.6 to 7.6 m 

(15 to 25 ft) below the seafloor. Current regulations do not mandate which method is to be used 

during decommissioning. BOEM is currently preparing a programmatic environmental assessment

for decommissioning activities in the GOM to update the 2005 programmatic environmental 

assessment analyzing impacts from decommissioning operations.

Approximately 85 percent of decommissioned offshore structures in the GOM were destined 

for shore-based scrap processing, while the remaining structures were reused or converted to 

artificial reefs. Structure-removal permit applications for the GOM between 2002 and 2013 are 

summarized in Table 3.4 3. 

Mechanical methods are used for structure removal in approximately 35 percent of 

decommissioning operations (USDOC, NMFS, 2012). Based on 10-year projections, Table 3.4-2

provides estimated number of structure removals.

The impact-producing factors associated with decommissioning that coincide with the 

impact-producing factors from G&G activities include noise from vessels and use of explosives to 

decommission equipment (i.e., platforms), vessel traffic and discharges, trash and debris, stand-off 

distance, and seafloor disturbance. Noise would be generated during explosive and nonexplosive 
Gulf of Mexico G&G Activities Programmatic EIS 3-39

structure removal. Vessel and helicopter traffic would occur in the vicinity of the platform undergoing 

decommissioning. The area surrounding decommissioning activities would be precluded for use by 

other ocean users, requiring a stand-off distance. Seafloor disturbances would occur as a result of 

the requirement to remove components below the mudline. Decommissioning activities have the 

potential for accidental fuel spills associated with support vessels. Table 3.4-1 outlines the impactproducing factors that coincide between G&G activities and decommissioning activities.

3.4.1.3 Renewable Energy Development

The two primary categories of renewable energy that have potential for development in the 

coastal and OCS waters of the U.S. are wind turbines and marine hydrokinetic systems. No wind 

farm developments have been proposed in OCS waters of the GOM; however, one facility in Texas 

State waters is in the initial stages of development. Wind Energy Systems Technology/Coastal Point 

Energy received State consent to build Galveston Offshore Wind Phase I, a 150-megawatt project 

proposed approximately 8 km (5 mi) off the Galveston coast. Neither the company nor the State 

have any intentions at this time of proposing activities in Federal waters. Additional information 

regarding this site is provided in Appendix E, Section 12.4. 

The impact-producing factors associated with renewable energy that could coincide with the 

impact-producing factors from G&G activities include noise from vessels and from installation and 

operation of the equipment (e.g., pile driving, vibratory hammering, and operational vibration), and 

vessel traffic, space-use conflicts, vessel discharges, trash and debris, seafloor disturbance, and 

accidental fuel spills. Table 3.4-1 outlines the impact-producing factors that coincide between G&G 

activities and renewable energy development.

3.4.1.4 Marine Minerals Use

Coastal restoration, beach nourishment, and levee reconstruction are crucial to mitigate 

future coastal erosion, land loss, flooding, and storm damage in the GOM. The success of these 

long-term efforts depends on locating and securing significant quantities of OCS sediment resources 

that are compatible with the target environments being restored. Human activities over the past 

century have contributed to erosion and coastal alteration, leading to the need for restoration and 

stabilization of coastal barrier islands and wetlands utilizing OCS marine minerals. Beginning in the 

late 1920s, flood control of the Mississippi River and subsequent construction of jetties and other 

structures began altering natural sediment availability and land-building processes. As the oil and 

gas, shipping, commerce, and other maritime industries expanded in the GOM, navigation channels 

were constructed, altering coastal habitats. Continued coastal development, coupled with severe 

hurricanes, has resulted in increased demand for coastal restoration projects, which are critical to 

protect human and natural communities as well as important coastal infrastructure.

Projected volumes from OCS sand borrow areas over the 10-year project period are 

9,700,000 yd3 from the EPA; 53,400,000 yd3 from the CPA; and 5,000,000 yd3 from the WPA, all 

from water depths no deeper than 20 m (66 ft) (Table 3.2-5). Offshore sand resources are 

considered extremely scarce, particularly in close proximity to where they are most needed. In 
3-40 G&G Activities and Proposed Action Scenario

addition, many of these offshore sand resources are not extractable because of the presence of oil 

and gas infrastructure, archaeologically sensitive areas, and biologically sensitive areas that require 

setbacks for dredging operations. Additional information regarding sand and gravel mining activity is 

provided in Appendix E, Section 12.3. 

The OCS protraction areas in the GOM with significant sediment resources that could be 

used in coastal restoration, beach nourishment, and levee reconstruction include the following:

• Breton Sound Area; • Vermilion Area;

• Chandeleur Area; • South Marsh Island Area, North Addition;

• Main Pass Area; • Eugene Island Area;

• Main Pass Area, South and East Addition; • Ship Shoal Area;

• High Island Area; • South Pelto Area;

• Sabine Pass Area; • West Delta Area; and

• West Cameron Area; • Mobile Area.

• West Cameron West Area;

The impact-producing factors associated with the marine minerals program that coincide with 

the impact-producing factors from G&G activities can include noise from vessels and dredging 

equipment noise, vessel traffic and discharges, stand-off distance, trash and debris, seafloor 

disturbance, and accidental fuel spills. Table 3.4-1 outlines the impact-producing factors that 

coincide between G&G activities and marine minerals extraction.

3.4.2 Oil and Gas Activities in State Waters

It is recognized that the types of activities described for OCS Program activities 

(Chapter 3.4.1) would be the same as oil and gas activities in State waters and would have the 

same impact-producing factors. However, oil and gas activities in State waters would include the 

G&G surveys permitted by other agencies. Therefore, impact-producing factors that coincide with 

G&G activities include: active acoustic sound sources, vessel and equipment noise, (support) vessel 

traffic, aircraft traffic and noise, stand-off distance, trash and debris, seafloor disturbance, drilling 

discharges, entanglement, and accidental fuel spills.

State waters typically extend from the mean lower low water line to 3 nmi (3.5 mi; 5.6 km) 

offshore, with the exception of Texas and the Gulf Coast of Florida, where State waters extend 9 nmi 

(10.6 mi; 16.7 km) offshore. All five Gulf Coast States have had some level of historical oil and gas 

exploration activity. Texas, Louisiana, and Alabama currently produce oil and gas in State waters 

(USDOI, BOEM, 2013c and 2013d). The USDOI, BOEM (2013c and 2013d) assembled a list of 

various oil and gas program websites for each Gulf Coast State. The websites provide information 

on the activity levels related to State oil and gas activities as well as production data for select 

states. Among the Gulf Coast States, Louisiana and Texas currently have the highest oil and gas 

production from State waters (Table 3.4-5). In addition, there is infrastructure that supports the 

State waters O&G activities, including wells; facilities that produce and treat raw product; and 
Gulf of Mexico G&G Activities Programmatic EIS 3-41

pipelines that transport the product to refineries, gas plants, storage, and market (USDOI, BOEM, 

2012).

3.4.3 Other Major Factors Affecting Offshore Environments

3.4.3.1 Deepwater Ports

Deepwater ports are designed to provide access for tankers and liquefied natural gas (LNG) 

carriers to offshore offloading facilities for hydrocarbon products (i.e., crude oil and natural gas). 

Crude oil passing through an offshore port may be temporarily stored, then transported to shore via 

pipeline, while LNG is regasified and pumped to shore. While the U.S. Department of 

Transportation’s Maritime Administration (MARAD) received numerous deepwater port applications 

between 2000 and 2010, economic conditions for LNG have declined since 2010. BOEM (USDOI, 

BOEM, 2013c and 2013d) expected interest in LNG offshore terminal projects to diminish over the 

next decade, with potential and subsequent stabilization in the LNG market. It is possible that LNG 

facilities in the GOM, or elsewhere, presently in the permitting process or in early construction 

phases could be withdrawn from consideration, cancelled, or deferred until LNG economics improve 

or until facilities under construction for importing LNG could be modified for exporting LNG. A 

summary of LNG terminal applications, application review determinations, and operational status for 

the GOM offshore LNG facilities is provided in Table 3.4-6. Additional discussion of deepwater ports 

is provided in Appendix E, Section 12.6. 

Only one offshore deepwater port currently handles the offloading of petroleum products, the 

Louisiana Offshore Oil Port (LOOP), which offloads crude oil and transports it to shore via pipeline. 

Operational since 1981, LOOP receives and temporarily stores crude oil supplies from three 

sources: (1) tankers carrying foreign and domestic crude oil; (2) domestic crude oil produced in the 

GOM; and (3) movement of domestic crude oil via the Houston to Houma (Ho-Ho) Pipeline. The 

LOOP is the only port in the U.S. capable of offloading deep-draft tankers (i.e., ultra-large crude 

carriers and very large crude carriers); LOOP also offloads smaller crude oil tankers. In 2012, LOOP 

received 304 tanker calls (Table 3.4-7).

The LOOP has a fleet of support vessels that patrol the port, support marine operations, and 

maintain stand-off distances for other vessels within the restricted safety zone. No major spills at 

LOOP have occurred in the more than three decades of operation, and maintenance inspections are 

expected to ensure that none will occur in the future. The operation of deepwater ports includes the 

following impact-producing factors coincident with G&G activities: vessel and equipment noise, 

vessel traffic, stand-off distance, vessel discharges, trash and debris, and accidental fuel spills.

3.4.3.2 Commercial and Recreational Fishing

Commercial Fishing

The commercial fishing industry is an important contributor to the GOM economy and has 

been since the mid-1800s. In 2012, the seafood industry in the five coastal states adjacent to the 

AOI supported nearly 160,000 jobs and generated $21.8 billion in sales (Appendix E, Section 9.1). 
3-42 G&G Activities and Proposed Action Scenario

Florida generated the highest employment, sales, income, and value added impacts, generating 

82,000 jobs, $16.6 billion, $3.1 billion, and $5.5 billion, respectively. Louisiana and Texas had the 

highest landings revenue in 2012, $331 million and $194 million, respectively (USDOC, NMFS, 

2014).

Fishers in the GOM region landed 1.7 billion pounds (lb) of finfish and shellfish in 2012 

(USDOC, NMFS, 2014). The main commercial fishing gears used within the AOI and along the 

GOM coast are bottom trawls, purse seines, gill nets, pots/traps, and longlines (bottom and pelagic), 

all of which can cause seafloor disturbance and pose a risk of entanglement with marine resources. 

Appendix E, Section 9.1 provides information on past landings for key species in the GOM from 

2003 to 2012.

Summary data provided by the USEPA (2010) indicate that commercial fishing vessel activity 

in the GOM, based on a subset of operational U.S.-flagged commercial fishing vessels for which the 

Marine Information for Safety and Law Enforcement provides a hailing port, varies substantially by 

state as follows:

State Number of Commercial Fishing Vessels

Texas >2,000 to 3,000

Louisiana >3,000

Alabama >500 to 1,000

Mississippi >500 to 1,000

Florida >3,000

Commercial fishing vessels utilize various types of active acoustic sound sources (e.g., 

sonar, echosounders, and acoustic instruments) to locate fish and identify seafloor contour and 

composition in order to effectively target desired species. Instrumentation is also used on gear (e.g., 

nets and trawls) to send acoustic signals to the vessel to determine the net’s location in the water or 

along the seafloor.

Recreational Fishing

Recreational fishing activity has influenced the GOM economy in a variety of ways since the 

1950s. Following World War II, increased tourism along the Gulf Coast, coupled with the mass 

production of fiberglass boats and improvements in motor technology and navigational equipment, 

led to increases in recreational fishing (Walter, 2006). Direct economic inputs include spending on 

fishing related goods and services such as expenditures on trips and durable equipment. Trip 

expenditures include transportation costs, boat fees, and bait expenses. Durable equipment 

expenditures include the purchase of fishing equipment and fishing boats. Appendix E, 

Section 10.1 provides information on economic contributions of recreational fishing, along with the 

locations, catch characteristics, and tournaments.

Recreational fishing is a year-round activity throughout the AOI and can be classified as a 

nearshore (<4.8 km [3.0 mi]) or offshore (>4.8 km [3.0 mi]) effort, depending on the size of the vessel 
Gulf of Mexico G&G Activities Programmatic EIS 3-43

and its fishing location (distance from shore). Nearshore recreational fishing consists of anglers 

fishing from private vessels and along beaches, marshes, or man-made structures (e.g., jetties, 

docks, and piers), whereas offshore fishing consists of anglers fishing from larger vessels farther 

from shore (private, rental, charter, or party).

Commercial and recreational fisheries include the following coinciding impact-producing 

factors with G&G activities: active acoustic sound sources; vessel and equipment noise; vessel 

traffic; stand-off distance; vessel discharges; trash and debris; seafloor disturbance; entanglement; 

and accidental fuel spills.

3.4.3.3 Shipping and Marine Transportation

The U.S. economy relies heavily on GOM ports for the import and export of foreign and 

domestic goods. The GOM supports many ports that rank high among U.S. ports in total commerce 

(USDOC, NOAA, 2011). Shipping and marine transportation into GOM ports is summarized in 

Table 3.4-7, in terms of individual port calls and total port calls for the most recent year that data are 

available (2012). Total vessel activity in the GOM can be assessed via the Automated Identification 

System (AIS), based on data acquired and stored by the USCG. The AIS is required on

• ships of 300 gross tons (GT) or more;

• passenger ships and tankers of 150 GT or more;

• all self-propelled commercial vessels (excluding fishing and passenger vessels 

with less than or equal to 150 passengers) 65 ft (20 m) or more in length; and

• towing vessels longer than 26 ft (8 m). 

The AIS data do not include recreational boats and other small vessels owned, leased, or 

operated by the military or other U.S. government entities. The AIS-based vessel trips in the GOM 

in 2012 are summarized in Table 3.4-8. Of the 308,664 total vessel trips documented in 2012, 

approximately 13 percent (39,111) were vessels measuring 60 to 170 m (197 to 558 ft) in length, the 

vessel size range that includes seismic survey vessels; vessel totals for which no vessel length data 

are available (67,344) are likely to include vessels in the 60- to 170-m (197- to 558-ft) size range. 

There were 59,334 cargo ship and 28,112 tanker trips in 2012.

Cruise ship activity in the GOM is limited to four ports: Galveston; Mobile; New Orleans; and 

Tampa. Table 3.4-9 outlines cruise ship departures from GOM ports on an annual basis between 

2008 and 2011. The AIS-based vessel trips in the GOM in 2012 are summarized in Table 3.4-8, 

documenting 14,486 passenger ship (including cruise ship) trips in 2012.

Shipping and marine transportation include the following coinciding impact-producing factors 

with G&G activities: vessel and equipment noise; vessel traffic; vessel discharges; trash and debris; 

and accidental fuel spills.
3-44 G&G Activities and Proposed Action Scenario

3.4.3.4 Dredged Material Disposal

Materials from maintenance dredging are primarily disposed of offshore at existing dredged 

material disposal banks and ocean dredged material disposal sites (ODMDSs), which are regulated 

by the USEPA. Additional dredged material disposal areas for maintenance or new-project dredging 

are developed as needed and must be evaluated and permitted by the USACE and relevant State 

agencies prior to construction.

The USACE currently identifies 40 ODMDSs in the GOM that were in use between 1973 and 

2013. As of early 2015, there were 30 active ODMDSs in the GOM (USACE, Engineer Research 

and Development Center, 2015). Additional information regarding ODMDSs is provided in 

Appendix E, Section 12.5. 

BOEM (USDOI, BOEM, 2013c and 2013d) anticipates that, over the next 40 years, the 

amount of dredged material disposed at ODMDSs will fluctuate within the trends established by the 

Galveston and New Orleans USACE Districts. Over the last 10 years, the Galveston and New 

Orleans Districts have disposed of an average of approximately 6 million yd3 and 22 million yd3 of 

material dredged per year, respectively. Future quantities may decrease slightly as more beneficial 

uses of dredged material onshore are identified.

The 1972 Convention on the Prevention of Marine Pollution by Dumping of Wastes and 

Other Matter (London Convention), to which the U.S. is a signatory, requires annual reporting of the 

amount of materials disposed at sea. The USACE prepares the dredged material disposed portion 

of the report to the International Maritime Organization, the yearly reports for which are posted on 

the USACE’s Ocean Disposal Database. Disposal produces increased water column turbidity as 

material is deposited on the seafloor.

Disposal at ODMDSs typically include use of dredges to excavate the material and to deposit 

the material at the sites and include use of support vessels and barges to monitor operations. The 

impact-producing factors coincident with G&G activities include vessel and equipment noise, vessel 

traffic, stand-off distances, vessel discharges, seafloor disturbance, trash and debris, and accidental 

fuel spills.

3.4.3.5 Existing, Planned, and New Cable Infrastructure

The only in-service submarine cable system that currently traverses the WPA and CPA is the 

BP Fiber Optic Network, which comes ashore in Freeport, Texas, and Pascagoula, Mississippi 

(North American Submarine Cable Association, 2014). The system is buried to a target depth of 1 m 

(3 ft) in water depths up to 800 m (2,625 ft) and is surface laid in water depths exceeding 800 m 

(2,625 ft). The 1,216-km (756-mi) long system is composed of a backbone and spurs. Additional 

information regarding the BP Fiber Optic Network is provided in Appendix E, Section 12.6.3. 

No new cable development projects in the GOM have been publicly reported; however, if 

future installations occur, a route survey utilizing HRG equipment would be conducted along the 
Gulf of Mexico G&G Activities Programmatic EIS 3-45

proposed route to identify seafloor characteristics, identify hazards, and determine burial methods. 

Cable systems typically are installed from a large cable vessel supported by smaller vessels and can 

be buried via plow, jetting, or trenching. The impact-producing factors coinciding with G&G activities 

include active acoustic sound sources, vessel and equipment noise, vessel traffic, stand-off 

distances, vessel discharges, trash and debris, seafloor disturbance, and accidental fuel spills.

3.4.3.6 Military Activities

The Gulf of Mexico (GOMEX) Range Complex contains four separate U.S. Navy Operating 

Areas (OPAREAs): Panama City and Pensacola, Florida; New Orleans, Louisiana; and Corpus 

Christi, Texas. The OPAREAs within the GOMEX Range Complex are not contiguous but scattered 

throughout the GOM. The GOMEX Range Complex includes special-use airspace with associated 

warning areas and restricted airspace as well as surface and subsurface sea space of the 

OPAREAs where underwater detonation testing and training may occur.

Twelve military warning areas and six Eglin Water Test Areas (EWTA) are located within the 

GOM (Figure 3.4-1). These are multiple-use areas where military operations and oil and gas 

development coexist without conflict. Several military stipulations are planned for leases issued 

within identified military areas.

The WPA includes all or parts of the following military warning areas: W-147, W-228, and 

W-602. The airspace over the WPA is used by the U.S. Department of Defense for conducting 

various air-to-air and air-to-surface operations. Naval Mine Warfare Command Operational Area D 

contains 17 OCS lease blocks in the WPA and is used by the U.S. Navy for mine warfare testing and 

training. In addition to Naval Mine Warfare Command Operational Area D, the WPA has four military 

warning areas that are used for military operations. The areas total approximately 8.6 million ha 

(21.3 million ac) or 75 percent of the total acreage of the WPA. To eliminate potential impacts from 

multiple-use conflicts on the aforementioned area, particularly those in OCS lease blocks that the 

U.S. Navy has identified as being needed for testing equipment and for training mine warfare 

personnel, a standard Military Areas Stipulation is routinely applied to all GOM leases in the WPA 

and CPA. 

Within the CPA, wholly or partially, are six designated military warning areas and three 

EWTAs used for military operations (Figure 3.4-1). The military warning areas within the CPA total 

approximately 5.4 million ha (13.3 million ac) or 23 percent of the total acreage of the CPA. The 

EWTAs within the CPA total approximately 2.8 million ha (7 million ac;) or 12 percent of the total 

acreage of the CPA. In addition to the previously noted standard Military Areas Stipulation, the 

EWTAs will require special stipulations, including an Evacuation Stipulation and a Coordination 

Stipulation. Additional information regarding military warning areas and other military uses is 

provided in Appendix E, Section 12.2. 

Within the EPA, the EWTAs encompass nearly all of the planning area and their primary 

function is to support research, development, test, and evaluation of conventional weapons and 
3-46 G&G Activities and Proposed Action Scenario

electronic systems. The secondary function is to support training of operational units (Air Force Air 

Armament Center, 2002). In addition, the Panama City and Key West OPAREAs are located in the 

EPA and have been identified by the U.S. Department of Defense (2010) as areas incompatible with 

oil and gas development.

It is anticipated that the military use areas currently designated in the GOM will remain the 

same and that none will be released for non-military use. With the cumulative activities scenario,

BOEM expects to continue to require military coordination stipulations in these areas. The intensity 

of the military’s use of these areas, or the type of activities conducted in them, is anticipated to 

fluctuate with military mission needs.

Military activities include the following impact-producing factors coinciding with G&G 

activities: active acoustic sound sources; vessel and equipment noise; vessel traffic; aircraft traffic 

and noise; stand-off distance; vessel discharges; trash and debris; seafloor disturbance; and 

accidental fuel spills.

3.4.3.7 Scientific Research

Scientific research in the GOM has been ongoing for several decades. Most of the recent 

oceanographic research in the GOM has centered on assessing the impacts of the Deepwater 

Horizon explosion, oil spill, and response. A few examples include the Gulf of Mexico Research 

Initiative’s selection of 12 research consortia to conduct scientific studies of the impacts of oil, 

dispersed oil, and dispersant on the GOM ecosystem and public health in 2014 and the Resources 

and Ecosystems Sustainability, Tourist Opportunities, and Revived Economies of the Gulf Coast 

States Act’s (RESTORE Act) funding of seven projects that focus on assessing ecosystem 

modeling, evaluating indicators for ecosystem conditions, and assessing and developing 

recommendations for monitoring and observing in the GOM.

Other scientific research in the GOM includes ship and aerial surveys for marine mammal 

population assessment. Ship surveys are used to assess the abundance and distribution of 

cetaceans by conducting visual line-transect surveys during the day and utilizing towed hydrophone 

arrays and sonobuoys at night. Surveys also include biopsy sampling and oceanographic data 

collection. Sea turtle population assessments typically are conducted in-water by visual observers 

from small vessels, but they can also be conducted via aerial surveys. Other methods to obtain sea 

turtle data include nest assessments, stranding data, bycatch, trawling, and satellite tracking. 

Fisheries stock assessments are complex, but methods include the use of acoustic techniques, 

aerial surveys, sampling (e.g., trawling), and visual surveys from autonomous underwater vehicles. 

Research activities include the following impact-producing factors coinciding with G&G 

activities: active acoustic sound sources; vessel and equipment noise; vessel traffic; aircraft traffic 

and noise; vessel discharges; trash and debris; seafloor disturbance; and accidental fuel spills.
Gulf of Mexico G&G Activities Programmatic EIS 3-47

3.4.3.8 Maintenance Dredging of Federal Channels

Navigation channels undergo maintenance dredging that is necessary for sustaining proper 

water depths, allowing ships to move safely through the waterways to ports, shore bases, and 

terminal facilities. BOEM anticipates that there will be maintenance dredging of navigation channels 

and an increase in activity at shore bases as a result of future lease sales in the WPA and CPA, 

although the extent of this dredging has not been quantified (USDOI, BOEM, 2013c and 2013d).

Maintenance dredging activities include the following impact-producing factors coinciding 

with G&G activities: vessel and equipment noise; vessel traffic; stand-off distance; vessel 

discharges; trash and debris; seafloor disturbance; and accidental fuel spills.

3.4.3.9 Coastal Restoration Programs

Coastal erosion results in a loss of sand from beaches, dunes, and barrier islands and has 

become a serious problem. Beach nourishment and other coastal restoration projects are 

authorized by BOEM to address this problem when offshore OCS sand resources are used. The 

P.L. 109-234, enacted in June 2006, appropriates funds to support coastal restoration efforts in the 

Gulf Coast States of Alabama, Mississippi, Louisiana, and Texas to assist in restoring the coastal 

areas damaged by Hurricanes Katrina and Rita in 2005. Sand resources needed to repair the 

damaged coastlines and barrier islands of the four states is estimated to be 191 to 229 million m3

(250 to 300 million yd3

) or more; in Louisiana alone, more than 518 km2 (200 mi2) of coastal land 

was lost due to the hurricanes (USDOI, BOEM, 2015d). Chapter 3.4.1.6 and Appendix E, Section 

12.3 provide details for recent projects in Florida and Louisiana, source sand volumes mined, and 

miles of restored shoreline (USDOI, BOEM, 2015e), as well as additional detail on various marine 

minerals projects in the GOM.

Coastal restoration program activities, in general, and sand source/beach restoration project 

operations, in particular, include the following impact-producing factors coinciding with G&G 

activities: vessel and equipment noise; stand-off distance; vessel discharges; trash and debris; 

seafloor disturbance; and accidental fuel spills.

3.4.3.10 Mississippi River Hydromodification and Subsidence

Hydromodification generally refers to a disruption or alteration of the natural flow of a water 

channel or drainage system that results in impaired water quality. Hydromodification processes 

have transpired over timeframes ranging from millennia to more recent times (e.g., decades, years, 

and months). Nonpoint-source pollution impacts generally are the result of anthropogenic land-use 

activities (e.g., straightening, dredging, and relocation). Hydromodification interventions include the 

construction of (1) levees along the river and distributary channel systems, (2) upstream dams and 

flood control structures that impound sediment and meter the river flow rate, and (3) channelized 

channels with earthen or armored banks. Once the natural processes that act to add sediment to 

the delta plain to keep it emergent are shut down, subsidence begins to outpace deposition of 

sediment (USDOI, BOEM, 2012).
3-48 G&G Activities and Proposed Action Scenario

The USDOI, BOEM (2012) anticipates that over the next 40 years there may be minor 

sediment additions resulting from new and continuing freshwater diversion projects managed by the 

USACE. Of the more than 200 projects currently listed in the Coastal Wetlands Planning Protection 

and Restoration Act (CWPPRA, 2015) program by the State of Louisiana, the majority involve 

introduction of sediment or reestablishment of natural water and sediment flow regimes to allow the 

delta plain to replenish and build up. Remaining programs represent freshwater diversion, outfall 

management, sediment diversion, and marsh creation projects.

Hydromodification activities include the following impact-producing factors coinciding with 

G&G activities: vessel and equipment noise; vessel traffic; vessel discharges; trash and debris; and 

accidental fuel spills.

3.4.3.11 Ancillary Considerations

Several discussion areas are considered in the cumulative scenario and impact analysis, 

although they are not considered in the same context (e.g., in terms of activity levels or spatial and 

temporal attributes) as other cumulative scenario activities previously described. These ancillary 

considerations, including extreme climatic events, global climate change, and natural oil seeps, may 

function in a predictable or unpredictable fashion to influence coastal and offshore environments.

Extreme Climatic Events

Between 1995 and 2015, 18 hurricanes made landfall in the GOM. Half of these hurricanes 

reached a maximum strength of Category 1 or 2; the other half were powerful hurricanes reaching 

maximum strengths of Category 4 or 5. Hurricanes Gustav and Ike in 2008 damaged energy 

infrastructure and supply disruptions for the oil and gas industry similar to, but not as severe as, 

those caused by Hurricanes Katrina, Rita, and Wilma in 2005 (USDOE, 2009). Hurricane Isaac in 

2012 was only a Category 1 storm, and fewer damages were reported; 2013, 2014, and 2015 did not 

have any hurricane landfalls in the GOM.

Climate Change and Sea-Level Rise

Warming of Earth’s climate system is occurring, and most of the observed increases in 

global average temperatures since the mid-20th century are very likely due to the observed increase 

in anthropogenic greenhouse gas concentrations (Intergovernmental Panel on Climate Change, 

2014; U.S. Global Change Research Program, 2009). Globally, many environmental effects have 

been documented, including widespread changes in snow melt and ice extent; spatial changes in 

precipitation patterns; changes in the frequency of extreme weather events; changes in stream flow 

and runoff patterns in snow fed rivers; warming of lakes and rivers, with effects on thermal structure 

and water quality; changes in the timing of spring events such as bird migration and egg laying; 

poleward shifts in ranges of plant and animal species; and acidification of marine environments (Orr 

et al., 2005; Intergovernmental Panel on Climate Change, 2007; Nye et al., 2009).
Gulf of Mexico G&G Activities Programmatic EIS 3-49

Over the next century, the Intergovernmental Panel on Climate Change (2014) projects that 

global temperature increases will cause significant global environmental changes, including a rise in 

sea level. The rate of climate change is forecast to have strong potential for continuation and 

acceleration, although many note that consequences will be unevenly felt across ecosystems 

(Doney et al., 2014). Cascading effects on resources of concern and the services they provide 

manifest in numerous ways that vary both spatially and temporally. Secondary impacts of increasing 

atmospheric concentrations of carbon dioxide and other greenhouse gases include several key 

physicochemical drivers: relative sea-level rise; ocean acidification; ocean heat content; the 

intensity, return interval, duration, and extent of storm events; changes in albedo (reflectivity); 

distribution and abundance of precipitation; and coastal erosion. These have been described in 

numerous reports (e.g., Boesch et al., 2000; Titus et al., 2009; Morel et al., 2010; Blunden et al., 

2011; Blunden and Arndt, 2015).

Tertiary effects of climate change on natural resource services arising from these key drivers 

include the distribution and abundance of both habitats and species. Associated with these climate 

change impacts are effects on critical habitats including sea ice loss (both a driver and a habitat), 

declining coral reef conditions, and loss of critical habitats (e.g., estuaries, wetlands, barrier islands, 

and mangroves). Interestingly, not all habitats are projected to experience an overall decline as a 

result of climate change. For example, Dixon et al. (2015) characterize the genetic response of coral 

to heating and Koch et al. (2013) discuss projected increases in seagrass habitat associated with 

climate change.

According to BOEM (USDOI, BOEM, 2013c and 2013d) in its cumulative impact analysis, the 

relative sea-level rise rates calculated by Penland and Ramsey (1990) are considered representative 

of the GOM. BOEM anticipates that, over the next 40 years, the coastal area of Louisiana will 

experience a total relative sea-level rise of approximately 46 cm (18.1 in); the amount will be lower in 

the eastern GOM and west coast of Florida, approximately 8.4 cm (3.3 in.). For the time period of 

interest to this analysis, Louisiana may experience a sea-level rise of approximately 11.5 cm (4.5 in), 

while the eastern GOM and west coast of Florida may realize a sea-level rise of 2.1 cm (0.83 in).

Natural Oil Seeps

Naturally occurring deepwater hydrocarbon seeps have been estimated to release between 

1 to 1.4 million barrels (bbl)/yr into the GOM (Kvenvolden and Cooper, 2003; NRC, 2003b). Natural 

seeps are extensive throughout the GOM continental slope and are the highest contributor of 

petroleum hydrocarbons to the marine environment. Pelagic tar is a common form of hydrocarbon 

contamination present in the GOM offshore environment (Van Vleet et al., 1983a and 1983b; 

Farrington, 1987). Higher tar concentrations were closely correlated with proximity to the Loop 

Current (Van Vleet, 1983b; Farrington, 1987). Van Vleet (1983a) estimated that approximately 

7,112,328 kilograms (7,000 tons) of pelagic tar are discharged annually from the GOM into the North 

Atlantic and that approximately half of the oil may be brought into the GOM from the Caribbean Sea 

via the Loop Current, while the remainder appears to originate in the GOM. Chemosynthetic 

communities with aerobic bacterial components typically are associated with natural oil seeps.
3-50 G&G Activities and Proposed Action Scenario

Treasure Hunting/Looting

Treasure hunting involves the intentional, nonscientific, usually commercial exploitation of 

archaeological resources for profit. Often, specific shipwrecks are targeted for salvage. It is 

unknown how many archaeological sites have been salvaged by treasure hunters in the GOM. Two 

recent examples of commercial treasure hunting in the Gulf of Mexico OCS are the salvage of the 

New York (Gearhart et al., 2011; Irion and Ball, 2001; Bowers, 2008) and El Cazador

(www.elcazador.com). Looting involves the planned or opportunistic removal of artifacts or features 

from an archaeological site. An example of the looting of an archaeological site was the attempted 

collection and destruction of artifacts on the shipwreck known as the Mardi Gras wreck during an 

remotely operated vehicle pipeline inspection (Ford et al., 2008).

Sport Diving

Sport diving includes private or commercial recreational diving on archaeological sites for 

pleasure and education. Impacts to archaeological sites from sport diving may result from boat 

anchor and mooring damage, disturbance to and removal (looting/souvenir hunting) of artifacts, 

intentional and unintentional physical contact (body or equipment), and the interaction of exhaled air 

bubbles with the site (Edney, 2006). Sport divers may, however, have an impact to archaeological 

sites by monitoring sites, encouraging fellow divers to protect sites, and by reporting any observed 

adverse impacts to the appropriate State or Federal agency.
CHAPTER 4

DESCRIPTION OF THE AFFECTED RESOURCES 

AND IMPACT ANALYSIS

Gulf of Mexico G&G Activities Programmatic EIS 4-3 

4 DESCRIPTION OF THE AFFECTED RESOURCES AND IMPACT 

ANALYSIS

4.1 INTRODUCTION

On the Gulf of Mexico OCS, various types of G&G activities are ongoing in support of 

offshore energy and minerals development under BOEM’s jurisdiction. A detailed summary of G&G 

activities and associated sound sources is provided in Appendix F. The projected activity scenario 

(for each of the 3 offshore program areas; e.g., number of line miles of seismic airgun surveys, 

including airgun and electromechanical sources; and number of core samples) is presented in 

Chapter 3. A brief summary of the program areas and associated survey types includes the 

following: 

Oil and Gas Exploration and Development: Exploratory G&G surveys are 

conducted to locate and evaluate potential oil and gas resources, primarily by 

conducting broad-scale 2D and 3D seismic surveys (deep-penetration surveys). 

Similar seismic sources are used in bore-hole surveys (VSPs) with downhole 

receivers and external sources. In addition, HRG site surveys of individual OCS 

lease blocks are conducted to detect geohazards, shipwrecks and other 

archaeological resources, and certain types of benthic communities. These are 

shallower-penetration surveys. Once development of oil and gas resources has 

begun, periodic surveys of the producing field (e.g., VSP or 4D surveys) also may be 

conducted. Geological surveys include bottom sampling methods including CPTs, 

cores, grabs, and test well drilling (Chapter 3.2.1, Table 3.2-9).

Renewable Energy Development: The G&G surveys in support of renewable 

energy development could include airgun surveys; however, surveys are most likely 

to include non-airgun HRG and geological surveys for three primary purposes: 

(1) assessment and characterization of potential wind facility locations; (2) cable 

routes to shore; and (3) detection of geohazards, shipwrecks and other 

archaeological resources, and certain types of benthic communities (Chapter 3.2.2, 

Table 3.2-9).

Marine Minerals: The G&G surveys are used to locate, characterize, and evaluate 

marine mineral deposits, including, but not limited to, sand for beach nourishment 

and coastal restoration projects. Site characterization and sand search (prospecting) 

geophysical surveys are undertaken to identify OCS sand resources and any 

environmental resources, cultural resources, and shallow hazards such as pipelines 

that may exist in potential borrow areas. The G&G surveys are also conducted to 

monitor dredging activities. Typical geophysical survey deployments may involve 

SBESs or MBESs, side-scan sonar, marine magnetometers, and sediment profilers 

(CHIRP subbottom profiler). Geological sampling is typically conducted by means of 

vibracoring, jet probing, or grab sampling (Chapter 3.2.3, Table 3.2-9).
4-4 Description of the Affected Resources and Impact Analysis

This Programmatic EIS analyzes projected scenarios for activity levels that are expected to

occur over the next 10 years. While BOEM acknowledges the current calendar year 2016 reduced 

level of exploration, G&G activity, and the corresponding decrease in permit applications, BOEM 

assumes that future levels will return to previous historic levels within the next 10 years. BOEM

must therefore be prudent and conservatively consider the full range of potential impacts. Therefore, 

the scenarios contain projections based on the analysis of recent historic activity levels and trends

made by BOEM’s subject-matter experts who also considered industry-projected activity levels in 

their estimates.

4.1.1 Preliminary Screening of Activities and Affected Resources

Earlier environmental analyses were reviewed to determine the physical, chemical, 

biological, and socioeconomic resources that should be considered and incorporated by reference in 

the current programmatic baseline characterization and impact analysis covering Gulf of Mexico

G&G activities. Previous EAs include the Programmatic EA for G&G activities in the GOM (USDOI, 

MMS, 2004) and a series of recent applicable EISs covering oil and gas activities in the GOM (e.g., 

USDOI, BOEM, 2012, 2013c, and 2013d). In addition, the Final Programmatic EIS for Atlantic G&G 

activities (USDOI, BOEM, 2014b) was reviewed and considered during identification of activities and 

affected resources that are also relevant to the GOM and proposed action.

The initial step in the preliminary screening was to briefly identify and characterize G&G 

activities expected to occur on the Gulf of Mexico OCS (i.e., activities expected under the oil and 

gas, renewable energy, and marine minerals programs), focusing on activity- and equipment-specific 

IPFs. The IPFs identified in this analysis were (1) active acoustic sound sources (e.g., airguns; nonairgun HRG sources such as boomers, sparkers, and CHIRP subbottom profilers; SBESs and 

MBESs; and side-scan sonars); (2) vessel and equipment noise; (3) vessel traffic (i.e., physical 

disturbance to and risk of collisions); (4) aircraft traffic and noise (e.g., helicopters and fixed-wing 

aircraft); (5) stand-off distance (i.e., area around the survey vessel cleared of other vessels); 

(6) vessel discharges; (7) trash and debris; (8) seafloor disturbance; (9) drilling discharges; and 

(10) entanglement (Chapter 3.3). Potential accidents were integrated into the preliminary screening 

in the form of a diesel fuel spill resulting from a vessel collision. Chapter 4.1.1.1 discusses the 

activity screening process.

Preliminary screening was also conducted to identify the resources at risk of impact from the 

suite of proposed and anticipated G&G activities. Screening allows for completion of a focused 

impact analysis by eliminating (from detailed analysis) resources with no potential for adverse or 

significant impact. This approach focuses the analysis on the resources at greatest impact risk. A 

total of 20 resources were initially reviewed. Chapter 4.1.1.2 discusses the resource screening 

process.

The G&G activity types and IPFs were formulated into a matrix (Table 4.1-1), which provides 

information on the activity types associated with each G&G activity included in all three program 

areas. A second matrix was subsequently developed to identify resources that could be affected by 
Gulf of Mexico G&G Activities Programmatic EIS 4-5 

each type of G&G activity to identify the applicable IPFs for which impacts must be analyzed 

(Table 4.1-2). In this analysis, the level of impact associated with each interaction was categorized 

as “potential impact for analysis” (e.g., a measurable impact to a resource is predicted) or “no impact

expected” (i.e., no measurable impact to a resource is evident).

4.1.1.1 Activity Screening

Based on the preliminary screening of G&G activities and identifiable IPFs, radar imaging 

using satellites was eliminated because it is not a geological or geophysical survey and does not 

require BOEM permit review and issuance. In addition, the onshore support activities’ IPF was 

determined to result in “no impact expected” because G&G surveys have been ongoing in the AOI 

and because onshore support facilities exist for this type of activity, so no additional onshore 

infrastructure is reasonably expected as a result of the proposed action or alternatives; therefore, it 

was not carried forward to the impact analysis. The IPFs from all G&G activities were evaluated for 

each Gulf of Mexico OCS resource to determine the resource-specific IPFs based on the activities. 

The results of this screening determined that over 60 percent of the possible IPFs were determined 

to have “no impact expected” across the OCS resources (Table 4.1-2).

4.1.1.2 Resource Screening

Several resource areas were identified as having no expected potentially significant impacts 

from G&G activities. Those resources eliminated from detailed analysis (Table 4.1-2) are described 

in Appendix E. The rationale for exclusion of these resources from further analysis is based on the 

following:

Human Resources and Land Use: The G&G activities in the proposed action 

would have a nominal effect on human resources and land use in the Gulf Coast 

area. Subcomponents, including land use and infrastructure, environmental justice, 

demographics, and socioeconomics, would not be impacted because G&G activities 

would all occur on the OCS, and they have been occurring for the past 30 years. 

Some very minor impacts may occur to the local and regional economy, as well as 

the coastal infrastructure, resulting from changes in employment and earnings in the 

G&G service sector. However, given the relative size of the local and regional 

economies compared with the potential changes in the G&G service sector, these 

impacts would be nominal for the proposed action. However, two of the alternatives 

described in Chapter 2 include a reduction in the level of G&G activities, which 

would have a potential effect to this resource. Therefore, an impact analysis of the

human resources and land use resource is provided in Chapter 4.13. 

Recreational Resources and Tourism: The G&G activities in the GOM would have 

a nominal impact on recreational resources and tourism along the Gulf Coast States. 

Many recreational resources and tourist attractions associated with the GOM are 

located on the coast or in coastal waters. As BOEM-regulated G&G activities would 

occur at least 3 nmi (3.5 mi; 5.6 km) away from all Gulf Coast States except Florida 
4-6 Description of the Affected Resources and Impact Analysis

and Texas, where activities would occur at least 9 nmi (10.4 mi; 16.7 km) away from 

the coast in Federal waters, few, if any, negative impacts would occur to recreational 

amenities. Water quality, air quality, and aesthetics near the recreational resources 

would not be affected; therefore, there would be no change in the quality of the 

recreational experience. As a result of the unchanged recreational amenities, tourist 

visitation rates and expenditures are expected to remain constant.

Air Quality: Potential impacts from emissions on air quality are expected to be 

nominal. Survey vessels, aircraft, machinery, and equipment involved in G&G 

activities would emit a variety of air pollutants, including nitrogen oxides (NOx), sulfur 

oxides (SOx), particulate matter (PM), volatile organic compounds (VOCs), and 

carbon monoxide (CO), as well as greenhouse gases (e.g., CO2) primarily from the 

combustion of fossil fuels for propulsion and power generation. The amount of air 

pollutants and greenhouse gases generated during G&G activities will depend 

primarily on the number, design, and size of the vessels; the size of engines and 

generators on the vessels; the distance traversed under power; and overall duration 

of the survey activities. Due to the limited extent and duration of most G&G 

activities, the amount of air pollutants generated would be small. Also, emissions will 

be distributed over a broad area of the OCS due to the generally non-stationary 

nature of G&G activities and likely would not result in any elevated pollutant 

concentrations exceeding air quality standards.

Water Quality: Potential impacts from vessel discharges on water quality are 

expected to be nominal. Survey vessels undertaking G&G activities would discharge 

treated sanitary and domestic wastes from USCG-approved MSDs along with 

miscellaneous discharges (e.g., deck drainage, bilge water, and machinery space 

drainage). The volume of treated discharges generated during G&G activities will 

depend primarily on the number, design, and size of the vessels, which would

determine the onboard crew complement; the distance traversed; and overall 

duration of the G&G activities. All vessels in U.S. and international waters are 

required to adhere to MARPOL limiting discharges (e.g., treatment of sanitary wastes 

and maceration of food wastes), avoiding releases of oily water, and prohibiting 

disposal of solid wastes. Treated sanitary and domestic wastes discharged into OCS 

waters will contain organic matter, particulates, nutrients, and residual chlorine that 

could affect water quality parameters. Due to the limited extent and duration of most 

G&G activities, the volume of liquid wastes generated would be small. Also, 

discharges will be distributed over a broad area of the OCS due to the generally nonstationary nature of G&G activities and likely would not result in any elevated 

concentrations of discharges or pronounced conditions affecting water quality.

Geology/Sediments: The G&G activities that could affect sediments include deep 

stratigraphic and shallow test drilling, CSEM and MT anchors, OBS receivers, and 

bottom sampling. Because of the nature of these sampling activities, only very minor

impacts to ambient sediments are expected as a result of well drilling, coring, grab 
Gulf of Mexico G&G Activities Programmatic EIS 4-7 

sampling, anchor deployment for CSEM and MT surveys, OBN or OBC deployment, 

and penetrometer tests, including the creation of small areas of surficial sediment 

disturbance, localized sediment resuspension and redeposition, and the creation of 

minor surficial discontinuities. Furthermore, deep stratigraphic and shallow test 

drilling and bottom sampling would have no effect on local or regional geology.

Physical Oceanography: Physical oceanographic resources would not be affected 

by G&G activities and associated discharges; impacts to physical oceanography are 

expected to be nominal and temporary. The G&G activities to be conducted from a 

survey vessel or floating platform would necessarily account for local and regional 

physical oceanographic conditions. Ocean current characteristics, water column 

density stratification, and vertical current structure, among other factors, would be 

considered during planning, operation, and data post-processing of G&G survey or 

sampling efforts.

Coastal Barrier Island Beaches, Seagrass, and Wetlands: The G&G activities in 

the GOM would have a direct impact on coastal barrier island beaches, seagrass, 

and wetlands along the Gulf Coast States from G&G vessel traffic; however, this 

impact would be nominal to this resource because G&G vessels represent such a 

small portion of overall vessel traffic in the GOM. However, sand sources found from 

G&G activities in Federal waters for beach nourishment would have a positive 

indirect impact on coastal barrier island beaches. The majority of these resources 

are located on the coast or in coastal waters. As the proposed G&G activities would 

occur at least 3 or 9 nmi (3.5 or 10.4 mi; 5.6 or 16.7 km) (depending on the state) 

away from the coast in Federal waters, few, if any, negative impacts would occur to 

these resources.

Twelve resource categories were carried forward for detailed baseline environment 

characterization and impact analysis in Chapters 4.2 through 4.13: 

• marine mammals;

• sea turtles; 

• fisheries resources and EFH; 

• benthic communities;

• marine and coastal birds;

• MPAs;

• Sargassum communities;

• commercial fisheries;

• recreational fisheries;
4-8 Description of the Affected Resources and Impact Analysis

• archaeological resources;

• other marine uses; and

• human resources and land use.

4.1.2 Impact Levels and Impact Significance Criteria

Broad significance criteria were developed for each of the biological and socioeconomic 

resources present on the Gulf of Mexico OCS based on the results of the resource screening and in 

consideration of recent environmental impact analyses and their respective impact descriptions. 

Criteria reflect consideration of the context and intensity of impact (40 CFR § 1508.27), based on 

four parameters: detectability (i.e., measurable or detectable impact); duration (i.e., short term, long 

term); spatial extent (i.e., localized, extensive); and severity (i.e., severe, less than severe). The 

impact descriptions developed for this analysis are based on impact thresholds employed and 

impacts determined in earlier EISs, including recent applicable EISs covering oil and gas activities in 

the GOM (e.g., USDOI, BOEM, 2012, 2013c, and 2013d), the Final Programmatic EIS for Atlantic 

G&G activities (USDOI, BOEM, 2014b), other impact analyses (e.g., Alternative Energy 

Programmatic EIS [USDOI, MMS, 2007c]; and the NSF-USGS Marine Seismic Research 

Programmatic EIS/OEIS [NSF and USDOI, GS, 2011]). For biological and socioeconomic 

resources, the significance criteria have been broadly defined as follows:

• Nominal: little or no measurable/detectable impact; 

• Minor: impacts are detectable, short term, extensive or localized, but less than 

severe; 

• Moderate: impacts are detectable, short term, extensive, and severe; or impacts 

are detectable, short term or long lasting, localized, and severe; or impacts are 

detectable, long lasting, extensive or localized, but less than severe; and

• Major: impacts are detectable, long lasting, extensive, and severe.

Each impact parameter was evaluated on a resource-specific basis to determine the 

appropriate impact level for each IPF. For biological resources, attributes such as distribution/range, 

life history, and susceptibility to impact of individual and populations were considered, among other 

factors. For socioeconomic resources, attributes such as archaeological significance or 

socioeconomic characteristics and susceptibility to impact were evaluated, among other factors.

The evaluation process to determine significance considered potential impacts by context 

(e.g., short term versus long term) and intensity (e.g., severity), following NEPA regulations as 

guidance (40 CFR § 1508.27). Context was defined as the extent of the effect (geographic extent or 

extent within a species, ecosystem, or region) and any special circumstances (e.g., endangered 

species or legal status), while intensity of an impact was defined as its magnitude and duration. 

Moreover, the potential effect was evaluated in terms of duration or frequency (short term, long term, 

and intermittent). The evaluation process also consisted of evaluating the likelihood (likely or not 
Gulf of Mexico G&G Activities Programmatic EIS 4-9 

likely) of an effect to occur (i.e., whether it was plausible or just speculative). During the preparation 

of the analysis of impacts, each application of an impact level was accompanied by a statement or 

statements explaining how the impact level was reached. Data or information from refereed journals 

used to support each determination are cited, as applicable. Otherwise, the determinations are 

based on the best available information.

4.1.3 Impact-Producing Factors

Chapter 3.3 describes the specific details of each IPF and Table 3.4-1 outlines the IPFs 

identified in association with G&G activities. During screening of IPFs, it was recognized that there 

was a need to identify, quantify, and analyze all of the potential active acoustic sources that might 

occur during G&G activities. The primary function of equipment and activity screening was to 

identify sources and survey types that had the potential to affect the environmental resources and to 

dismiss those that did not rise to this level of potential impact. To accomplish this screening, BOEM 

decided to create a ScOT, which first convened in April 2014, to examine this source identification 

issue and make recommendations. The results of the screening indicated that those acoustic 

sources that operate at frequencies above 200 kHz do not require detailed analyses because this 

frequency is outside of the hearing range for marine mammals, but should focus on the impact 

analysis for specific equipment types that have operational frequencies below 200 kHz and airguns. 

The results of this screening are presented in the ScOT report (Appendix G).

Overall, the impact analyses consider direct, indirect, and cumulative effects. Direct effects 

were defined as effects that may be caused by the proposed action and occur at the identical 

location and time of the action (40 CFR § 1508.8). Indirect effects were defined as effects that may 

be caused by the proposed action at a later time or farther from the location of the action but are still 

reasonably foreseeable to occur (40 CFR § 1508.8). Cumulative effects are defined as additive, 

interactive, or synergistic effects that would result from the incremental impact of the proposed 

action compared with or added to other past, present, and reasonably foreseeable future actions, 

regardless of what agency or person undertakes such other actions (40 CFR § 1508.7; CEQ, 

1997b). Cumulative impacts, or the accumulation of effects, can result from one or more processes. 

These processes, as outlined by the NRC (2003c), can include the following: 

• frequent and repeated impacts on a single environmental resource (i.e., time 

crowding);

• high-density impacts on a single environmental resource (i.e., space crowding);

• synergistic impacts attributable to multiple sources on a single environmental 

resource (i.e., compounding impacts);

• impacts that become qualitatively different once a resource-specific threshold of 

disturbance has been reached or surpassed (i.e., thresholds); and
4-10 Description of the Affected Resources and Impact Analysis

• the progressive loss of habitat resulting from a sequence of activities, each of 

which has relatively innocuous consequences, however, the environmental 

consequences accumulate (i.e., “nibbling”).

Cumulative impacts characterized in the following analysis consider the incremental increase 

of each IPF associated with G&G activities, as well as the additive, interactive, or synergistic effects 

that might result.

4.1.4 Other Considerations

4.1.4.1 Analysis and Incomplete or Unavailable Information

The analyses of potential effects on the wide variety of physical, biological, and 

socioeconomic resources in the vast area of the GOM and adjacent coastal areas are very complex. 

Specialized education, experience, and technical knowledge are required, as well as familiarity with 

the numerous IPFs associated with G&G activities at sea that can cause cumulative impacts in the 

area. Knowledge and practical working experience with major environmental laws and regulations 

such as NEPA, CWA, CAA, CZMA, ESA, MMPA, MSFCMA, and others is also required.

Due to the complexity of the Gulf of Mexico and the wide range of resources found therein, it 

is unlikely that complete information will ever be available for all resources evaluated in this 

Programmatic EIS. However, NEPA guidance allows decisions to be made if certain conditions are 

met. When an agency is evaluating reasonably foreseeable significant adverse effects on the 

environment in an EIS and there is incomplete or unavailable information, NEPA requires the agency 

to report what relevant information is incomplete or unavailable and why, whether it is essential to a 

reasoned choice among the alternatives, and whether the cost or time limitations would be 

exorbitant to obtain the information or if a means to acquire it is not known (40 CFR § 1502.22). The 

action agency must provide a statement to this effect and, in addition, must provide an evaluation of 

impacts based upon existing credible scientific evidence applied using theoretical approaches or 

methods generally accepted in the scientific community (40 CFR § 1502.22).

For example, there is incomplete or unavailable information for marine mammals species 

found in the Gulf of Mexico related to (1) seasonal abundance, (2) stock or population size, and 

(3) stock or population trends. For marine mammals, in general, there is incomplete or unavailable 

information regarding hearing ranges and the basic biology of specific species and their physiology 

for underwater hearing. For both marine mammals and sea turtles, there is incomplete or 

unavailable information about how these species are impacted by anthropogenic sounds, including 

chronic and sub-lethal impacts. Since many environmental factors affect sound propagation in the 

sea, investigations also are underway to improve our understanding of sound propagation.

This chapter has thoroughly examined the existing credible scientific evidence that is 

relevant to evaluating the reasonably foreseeable significant adverse impacts of G&G activities on 

the human environment. A diligent search for pertinent new information was conducted, and 

BOEM’s evaluation of such impacts is based upon theoretical approaches or research methods 
Gulf of Mexico G&G Activities Programmatic EIS 4-11

generally accepted in the scientific community. BOEM’s subject-matter experts acquired and used 

newly available, scientifically credible information; determined that other additional information was 

not available absent exorbitant expenditures or could not be obtained regardless of cost in a timely 

manner; and where gaps remained, exercised their best professional judgment to extrapolate 

baseline conditions and impact analyses using accepted methodologies based on credible 

information, including information in the appendices. All reasonably foreseeable impacts have been 

considered, and the characterization of impact magnitude and duration is supported by credible 

scientific evidence. BOEM’s assessment of impacts is not based on conjecture, media reports, or 

public perception; rather, it is based on theoretical approaches, research methods, and modeling 

applications generally accepted in the scientific community. BOEM has analyzed the results of an 

extensive modeling effort (Appendix D), which estimates marine mammal exposures to the 

proposed G&G activities included in the proposed action.

Where information was incomplete or unavailable, BOEM complied with its obligations under 

NEPA to determine if the information was relevant to reasonably foreseeable significant adverse 

impacts; if so, whether it was essential to a reasoned choice among alternatives; and, if it is 

essential, whether it can be obtained and whether the cost of obtaining the information is exorbitant, 

as well as whether generally accepted scientific methodologies can be applied in its place (40 CFR § 

1502.22). The most notable incomplete or unavailable information relates to some aspects of the 

effects from the Deepwater Horizon explosion, oil spill, and response. Nonetheless, BOEM’s 

subject-matter experts acquired and used newly available, scientifically credible information; 

determined that other additional information was not available absent exorbitant expenditures or 

could not be obtained regardless of cost in a timely manner; and where gaps remained, exercised 

their best professional judgment to extrapolate baseline conditions and impact analyses using 

accepted methodologies based on credible information. While incomplete or unavailable information 

could conceivably result in potential future shifts in baseline conditions of habitats that could affect 

BOEM’s decisionmaking, BOEM has determined that it can make an informed decision even without 

this incomplete or unavailable information because BOEM’s subject-matter experts can apply other 

scientifically credible information using accepted theoretical approaches and research methods, 

such as information on related or surrogate species. Moreover, BOEM will continue to monitor these 

resources for effects caused by the Deepwater Horizon explosion, oil spill, and response, and will 

ensure that future BOEM environmental reviews take into account any new information that may 

emerge.

4.1.4.2 Cumulative Scenario Summary

Cumulative effects (40 CFR §1508.7) refers to the impact on the environment that results 

from the incremental impact of the action when added to other past, present, and reasonably 

foreseeable future actions regardless of what agency (Federal or non-Federal) or person undertakes 

such other actions. Cumulative impacts can result from individually minor but collectively significant 

actions taking place over a period of time. Chapter 3.4 provides the complete description of the 

cumulative activities scenario. The cumulative impact analysis focuses on the resources rather than 

the proposed action and considers impacts that take place on both spatial and temporal scales. The 
4-12 Description of the Affected Resources and Impact Analysis

cumulative impacts analysis focuses only on impacts to resources that are potentially impacted from 

the proposed action. If the proposed action would not impact an identified resource, then those 

resources are not addressed in the cumulative impacts analysis in this Programmatic EIS.

4.1.4.3 NMFS’ Acoustic Guidelines

In July 2016, NMFS released the final version of the Technical Guidance for Assessing the 

Effects of Anthropogenic Sound on Marine Mammal Hearing: Underwater Acoustic Thresholds for 

Onset of Permanent and Temporary Threshold Shifts (USDOC, NMFS, 2016a). This document 

provided acoustic guidelines (specifically those that identify the onset of Permanent Threshold Shift 

[PTS] or Temporary Threshold Shift [TTS]) to be used when conducting impact analyses for marine 

mammals. As NMFS stated in their Executive Summary, “While the Technical Guidance’s acoustic 

thresholds are more complex than those used to date in most cases by NMFS, they reflect the 

current state of the scientific knowledge regarding the characterization of sound that have the 

potential to impact marine mammal hearing sensitivity.” Throughout the development of this new 

guidance, BOEM provided comments and review.

Before this final version of the acoustic guidelines was completed in July 2016, BOEM 

completed modeling efforts to assess the potential acoustic impacts from G&G activities for use in 

this Programmatic EIS (refer to Appendix D). These modeling efforts used the acoustic guidance 

that was available from NMFS at that time; this guidance specified that marine mammals exposed to

pulsed sounds with received levels exceeding 180 or 190 decibels referenced to 1 microPascal (root 

mean square) (dB re 1 μPa [rms]) are considered to exceed Level A (Injury) levels. The NMFS also 

specified at that time that cetaceans exposed to levels exceeding 160 dB re 1 μPa (rms) are 

considered to exceed Level B (Behavioral Harassment) criteria. The table below summarizes the 

threshold values used by this Programmatic EIS’ modeling and the new criteria for impulsive sources 

(i.e., airguns) for both energy and pressure metrics. Additionally, the final two columns show the 

difference in these threshold values. The negative values indicate a decrease in the threshold value, 

which corresponds to an increased number of potential impacts because a lower value implies a 

larger area or volume that may be exposed to the requisite threshold.

Modeled and New Acoustic Guideline Criteria

Functional Hearing Group

GOM Programmatic EIS 

Modeling New Criteria Difference

Energy Pressure Energy Pressure Energy Pressure

SEL

(dB re

1 μPa2·s)

peak SPL

(dB re 

1 μPa)

LE,LF,24h 

(dB re 

1 μPa2·s)

Lpk,flat 

(dB re 

1 μPa)

(dB) (dB)

Low-frequency cetaceans 192 230 183 219 -9 -11

Mid-frequency cetaceans 187 230 185 230 -2 0

High-frequency cetaceans 161 200 155 202 -6 +2
Gulf of Mexico G&G Activities Programmatic EIS 4-13

In addition to changing threshold values, the new acoustic guidance incorporates changes to 

marine mammal hearing and weighting functions. The figure below shows the 2012 weighting 

functions (e.g., those used in the modelling for this Programmatic EIS) as dashed lines, while the 

comparable new criteria values are shown as solid lines of the same color. Note that at a first 

glance, there are differences, but they do not seem very large. However, if we look specifically at 

how this could affect seismic operations, there are some very large differences.

Comparison of the M-Weighting Curves for the 2012 Criteria and the July 2016, New Acoustic Criteria

Most of an airgun’s energy is produced in the 100- to 300-Hz frequency band, which is 

shown as the red box in the figure. The red arrow shows the difference between the two criteria for 

the 200-Hz example. The difference is about -13 dB. When this is combined with the -9 difference 

for the threshold value in the table above, it combines for a total threshold change of -22 dB for lowfrequency cetaceans exposed to airgun operations. This is the equivalent (using a simple spherical 

spreading assumption) of a ten-fold increase in Level A impacts for low-frequency cetaceans.

For all of the other species, the combination of the threshold and the M-weighting will 

generally reduce the number of Level A impacts for a given seismic operation.

The table below provides a similar analysis as above to demonstrate what the likely 

differences may be when applying the revised acoustic criteria to non-impulsive sources such as 

HRG sources.

-50.0

-45.0

-40.0

-35.0

-30.0

-25.0

-20.0

-15.0

-10.0

-5.0

0.0

1 10 100 1000 10000 100000 1000000 M - Weighting (dB)

Frequency (Hz)

LF 2012

MF 2012

HF 2012

LF 2012

MF 2012

HF 2012
4-14 Description of the Affected Resources and Impact Analysis

Modeled and New Acoustic Guideline Criteria for Non-Impulsive Sources

Functional Hearing Group

GOM Programmatic EIS 

Modeling New Criteria Difference

Energy Pressure Energy Pressure Energy Pressure

SEL 

(dB re

1 μPa2·s)

peak SPL

(dB re 

1 μPa)

LE,LF,24h 

(dB re 

1 μPa2·s)

Generally 

not 

needed 

or used

(dB) (dB)

Low-frequency cetaceans 192 230 199 - +7 N/A

Mid-frequency cetaceans 187 230 198 - +11 N/A

High-frequency cetaceans 161 200 173 - +12 N/A

N/A = not applicable.

Note: The new criteria requires the summation of energy over 24 hours, which is different from the old 

criteria which summed it for shorter periods of time and “reset” the animal to pristine condition 

every 24 hours so that it could be impacted again.

Here, even though the energy is now summed over a 24-hour period, the higher thresholds 

and M-weighting curves (for mid-frequency and high-frequency cetaceans) offset this change in the 

timeframe over which energy is summed and the number of Level A impacts for mid-frequency and 

high-frequency cetaceans remain the same or are slightly reduced overall. For low-frequency 

cetaceans, however, a +7 threshold only slightly compensates for the reduced M-weighting between

30 and 1,000 Hz (e.g., the weighting is about -16 dB between 100 and 300 Hz), and the overall 

result can be as much as -9 dB (i.e., +7-16 = -9) overall. This is equivalent to a 3-fold increase in the 

radius for non-impulsive sources in this frequency range (such as boomers) and an approximately 

10-fold (32 = 9 or about 10) increase impacts for low-frequency cetaceans overall. Most HRG 

sources, however, are primarily above 1,000 Hz. Boomer range is generally 800 Hz to 1.2 kHz, 

while chirp uses variable frequencies usually in the 160- to 200-kHz range with some portions of 

chirp sonars in the 3.5 Hz to 1,000 Hz range, possibly resulting in an increase to estimated impacts.

This is based on BOEM’s initial review of the newly published 2016 acoustic guidelines. 

BOEM intends to further review these new guidelines and work with the NMFS for further 

clarification and guidance on how to apply this new information. Additionally, the modeling effort in 

Appendix D, which provides numbers estimated for incidental exposures of marine mammals, are 

higher than BOEM expects would actually occur. They do not, for example, take into account any 

mitigation measures incorporated into the alternatives because the effect of those measures cannot 

be quantified with statistical confidence at this time. Further, the exposure estimates are based on 

acoustic and impact models that are, by their nature, conservative and complex. Each of the inputs 

into the models is purposely developed to be conservative, and this conservativeness accumulates 

throughout the analysis.

It is important to note that BOEM does not believe that every exposure to sound results in 

“take” as defined by the MMPA’s Section 101(A)(5)(A-D). Therefore, exposure estimates used in 

this Programmatic EIS are not the same as a “take” or an injury to an animal. Where there is an 

overlap between noise sources and the frequencies of sound used by marine life, there may be 

concerns related to how such sound may interfere with important biological functions. Noise, either 
Gulf of Mexico G&G Activities Programmatic EIS 4-15

natural or anthropogenic, can adversely affect marine life in various ways—inducing alteration of 

behavior, reduction of communication ranges or orientation capability, temporary or permanent 

damage to the auditory or other systems; and/or, in extreme cases, habitat avoidance or even death 

(e.g., Richardson et al., 1995; NRC, 2003, 2005; Nowacek et al., 2007; Southall et al., 2007). Noise 

impacts may also be additive or synergistic to those of other human stressors. While determining 

the biological significance of noise exposure impacts remains challenging (NRC, 2005), significant 

strides have been made in quantifying the effects of noise on marine mammals (USDOI, BOEM, 

2014b). As such, the exposure estimates presented in this Programmatic EIS were computed from 

modeled sound levels received by simulated (modeled) animals for several types of geophysical 

surveying. Animals and sources are constantly moving relative to the environment and each other. 

The sound fields generated by the sources are shaped by various physical parameters, and the 

sound levels ultimately received by an animal are a complex function of location and time. The basic 

modeling approach was to use acoustic models to compute the 3D sound fields and their variations 

in time. Simulated animals (animats) were modeled moving through these fields to sample the 

sound levels in a manner similar to how real animals would experience these sounds. This allows a 

history of exposures to be built of the received sound levels of all animats. The numbers of animals 

exposed to levels exceeding effects threshold criteria were determined and then adjusted by the 

number of animals expected in the area, based on density information (which may not be an 

accurate representation of the marine mammal population). This creates an estimate of the potential 

number of animals exposed to the sounds. This estimate does not reflect an actual expectation that 

marine mammals will be injured or disturbed; it is an overly conservative estimate. Biological 

significance to marine mammals is left to interpretation by subject-matter experts. Using the model 

estimates most often requires accepting a worst-case scenario, which ultimately equates in some 

from the numbers of exposures to the number of “takes” under the MMPA.

The existing modeling largely does not account for uncertainty in the data inputs and also 

selects highly conservative data inputs. This bias often produces unrealistically high exposure 

numbers and “takes” that exponentially increase uncertainty throughout each step of the modeling. 

The modeling does not incorporate mitigation or risk reduction measures designed to limit exposure. 

The modeling is an overestimate and should be viewed with that understanding.

4.1.4.4 Risk Assessment Framework

Throughout this chapter, where information was incomplete or unavailable, BOEM complied 

with its obligations under NEPA to determine if the information was relevant to reasonably 

foreseeable significant adverse impacts; if so, whether it was essential to a reasoned choice among 

alternatives; and, if it was essential, whether it can be obtained and whether the cost of obtaining the 

information is exorbitant, as well as whether scientifically credible information, using generally 

accepted scientific methodologies, can be applied in its place (40 CFR § 1502.22).

The most notable incomplete or unavailable information relates to the development of a 

novel analytical method to evaluate the effects of human noise on marine mammal hearing and 

behavior. Produced by a research collaboration of world-leading scientists in underwater sound, 
4-16 Description of the Affected Resources and Impact Analysis

marine mammal hearing and behavior recently produced an acoustic RAF. In broad terms, the 

acoustic RAF considers the results of conventional assessments (e.g., exposure estimates) and, 

through a rigorous, analytical methodology, interprets what these estimates mean within the context 

of key biological and population parameters (e.g., population size, life history factors, compensatory 

ability of the species, animal behavioral state, source-animal proximity, relative motion, variance in 

density estimates, and aversion) and other biological, environmental, and anthropogenic factors. 

The end result provides not just the numbers of exposures, which is what conventional approaches 

to modeling provides, but instead what these numbers mean biologically for each affected marine 

mammal stock/population (i.e., severity of impact and vulnerability of stock/population), as well as 

the likelihood of any such impact. Traditional approaches to assessing the effects of noise on 

marine mammals involve acoustic modeling that produces estimates of exposures of marine 

mammals to potentially disturbing or injurious noise (e.g., Level A and Level B Harassment under 

the MMPA). Agencies like BOEM are then left with interpreting (more qualitatively and narratively) 

what these numbers mean as far as biological significance to marine mammals. Without a rigorous 

methodology to do this interpretation, BOEM and other agencies must move forward with an overly 

conservative scenario equating the numbers of exposures to the number of “takes” under the MMPA 

(and ESA and NEPA). This often produces unrealistically high exposure/take numbers. In this 

instance, the exposure/take numbers were also modeled without the application of mitigating 

measures, adding to the unrealistically high exposure/take numbers.

The RAF analysis would yield a more biologically meaningful analysis while still integrating 

current requirements and needs of U.S. regulatory agencies such as NOAA/NMFS’ Acoustic

Threshold Criteria and use of the best available science, such as the marine mammal density 

estimates produced by Duke University (Roberts et al., 2016). The RAF also integrates risk 

assessment methods used commonly by industry. While the RAF thus far currently focuses on 

airguns, it can also be adapted for other noise-producing activities and different locations.

Therefore, BOEM determined that the RAF is relevant to reasonably foreseeable significant 

adverse impacts and is essential to a reasoned choice among alternatives, and though it cannot be 

obtained in the timeframe contemplated for this EIS, scientifically credible information using 

generally accepted scientific methodologies was applied in its place. 

Nonetheless, BOEM’s subject-matter experts acquired and used newly available, 

scientifically credible information to determine exposure/take estimates; determined that other 

additional information was not available absent exorbitant expenditures or could not be obtained 

regardless of cost in a timely manner; and where gaps remained, exercised their best professional 

judgment to extrapolate impact analyses of anticipated exposure/take numbers using accepted 

methodologies based on credible information. While incomplete or unavailable information could 

affect the impact analyses of marine mammal stocks/populations in the GOM and BOEM’s 

decisionmaking, BOEM has determined that the information is essential but that it can make an 

informed decision at this time without this incomplete or unavailable information. BOEM’s subjectmatter experts have applied other scientifically credible information using accepted approaches and 

research methods, such as used in the Acoustic Propagation and Marine Mammal Exposure 
Gulf of Mexico G&G Activities Programmatic EIS 4-17

Modeling of Geological and Geophysical Sources in the Gulf of Mexico conducted by JASCO 

Applied Sciences (refer to Appendix D). 

4.1.4.5 Space-Use Conflicts

Marine space-use issues are a continuing problem and an important element in marine 

spatial planning (Crowder and Norse, 2008; Douvere and Ehler, 2009). Whenever activities take 

place on the OCS, there is the potential for space-use conflict that must be evaluated prior to 

conducting regulated activities. However, as discussed in Chapter 3.4, in the GOM, multiple users 

have been sharing the OCS for decades, including oil and gas exploration and development, military 

operations, commercial fishing, and significant vessel traffic. BOEM’s oil and gas program activities 

have been ongoing since the 1950s and includes the presence of approximately 7,271 platforms 

placed (4,597 removed), 53,961 total miles of pipeline (27,082 miles active), and 53,638 boreholes 

drilled (26,190 permanently abandoned) (Marine Cadastre, 2015). In addition, BOEM takes into 

account the restrictions under the GOMESA, which preclude leasing, pre-leasing, or any related 

activity in certain areas in the GOM that conflict with military operations, as well as requiring 

coordination with the USDOD regarding certain activities occurring in USDOD’s Operating Areas 

(OPAREAs). Commercial fishing in the GOM includes a total of over 9,000 vessels (USEPA, 2010), 

and Automatic Identification System (AIS) vessel traffic data from 2012 included 308,664 total vessel 

trips in the GOM. Therefore, coordinating space-use conflicts is an ongoing process in the GOM.

The three major components of the cumulative scenario discussed in detail in Chapter 3.4, 

include (1) the OCS Program; (2) oil and gas activities in State waters, and (3) other major factors 

influencing the AOI. All of these activities spatially coexist with other activities on the OCS but differ 

in their potential for space-use conflict by their degree of permanence or frequency.

For example, in the GOM, a Military Areas Stipulation is required for leased OCS lands 

under the oil and gas program; this stipulation specifies points of contact between industry operators 

and USDOD facility operators to reduce potential impacts, particularly in regards to safety. Military 

and all other GOM activities coexist with mandated routine coordination of activities. The reduction 

in potential impacts resulting from this stipulation makes multiple-use conflicts unlikely, but without it, 

some potential conflict with respect to safety issues is likely. The best indicator of the overall 

effectiveness of the stipulation may be that, even with the approximately 7,271 oil and gas structures 

and associated activities ongoing since the 1950s, there has never been an accident involving a 

conflict between military operations and oil and gas activities in the GOM.

Marine spatial planning is a key factor in reducing space-use conflicts. Coastal and marine 

spatial planning (CMSP) is “a comprehensive, adaptive, integrated, ecosystem-based, and 

transparent spatial planning process, based on sound science for analyzing current and anticipated 

uses of ocean, coastal, and Great Lakes areas” (75 FR 43023). The CMSP aims to reduce conflict 

among uses, reduce environmental impacts, facilitate compatible uses, and preserve critical 

ecosystem services. BOEM is implementing CMSP as a tool to achieve National Ocean Policy 

objectives. The CMSP will provide a framework for the coordinated application of existing laws and 
4-18 Description of the Affected Resources and Impact Analysis

agency authorities. BOEM is using a phased implementation approach to CMSP that includes 

engaging State, Tribal, Federal, and public stakeholders and technical experts; consulting with 

regional Fishery Management Councils (FMCs); drafting Strategic Action Plans; and developing a 

data portal for all applicable Federal data access and sharing. Space-use conflicts for each 

applicable resource category have been addressed within individual impact discussions, identified 

within the IPFs associated with the presence of structures, vessel traffic, and vessel stand-off 

distances. The analyses include direct, indirect, and cumulative impacts to each resource category.

4.1.5 Effects of the Deepwater Horizon Oil Spill 

On April 20, 2010, the Deepwater Horizon mobile drilling unit exploded, caught fire, and 

eventually sank, resulting in loss of life and a massive release of oil and other substances from BP’s 

Macondo well. The Deepwater Horizon oil spill released approximately 134 million gallons 

(3.19 million barrels) of oil and 1.84 million gallons of dispersant into the environment (USDOC, 

NOAA, 2015d). Every day for 87 days, the well released an average of >1.5 million gallons of fresh 

oil into the ocean, essentially creating a new major oil spill every day for nearly 3 months.

The Oil Pollution Act of 1990, as provided in 33 U.S.C. § 2706, allowed the designation of 

the Natural Resource Damage Assessment Trustee Council (Trustee Council), which included 

certain Federal agencies, States, and Indian Tribes. Executive Order 13554, which was signed on 

October 5, 2010, recognized the role of the Trustee Council under the Oil Pollution Act and 

“designated trustees as provided in 33 U.S.C. § 2706, with trusteeship over those natural resources 

injured, lost, or destroyed as a result of the Deepwater Horizon oil spill.” Specifically, Executive 

Order 13554 recognized the importance of carefully coordinating the work of the Gulf Coast 

Ecosystem Task Force with the Trustee Council, “whose members have statutory responsibility to 

assess natural resource damages from the Deepwater Horizon oil spill, to restore trust resources, 

and seek compensation for lost use of those trust resources” (The White House, 2012). The Task 

Force, on the other hand, was charged with creating a plan to improve the overall health of the Gulf 

of Mexico area and has focused on a number of stressors to the Gulf Coast ecosystem beyond 

those caused by the Deepwater Horizon explosion, oil spill, and response. While the work of the 

Task Force has been independent from the work of the Trustees, the valuable information gathered 

by the Task Force will be useful to the Trustees in their restoration planning efforts (USDOC, NOAA, 

2015e).

The NRDA activities for the BP oil spill have been divided into the categories below and 

focus on specific species, habitats, or uses (USDOC, NOAA, 2015f):

• marine mammals and sea turtles; 

• fish and shellfish;

• birds;

• deepwater habitat (e.g., deepwater coral);
Gulf of Mexico G&G Activities Programmatic EIS 4-19

• nearshore habitats (including seagrasses, mud flats, and coral reefs);

• shoreline habitats (including salt marsh, beaches, and mangroves);

• land-based wildlife and habitat; and

• public uses of natural resources (including recreational fishing, boating, beach 

closures).

The Trustee Council is currently in Phase III of early restoration, and the data collection, 

analysis, and restoration are ongoing (USDOI, 2015). The final Phase III plan proposes $627 million 

for 44 new early restoration projects across the Gulf Coast States. It also includes plans to prepare 

a programmatic EIS and programmatic restoration plan for early restoration (USDOC, NOAA, 

2015g).

In October 2015, NOAA released the Deepwater Horizon Oil Spill: Draft Programmatic 

Damage Assessment and Restoration Plan and Final Programmatic Environmental Impact 

Statement (USDOC, NOAA, 2015d). This was followed by the Deepwater Horizon Oil Spill: Final 

Programmatic Damage Assessment and Restoration Plan and Final Programmatic Environmental 

Impact Statement (Final PDARP/PEIS) in February 2016 (Deepwater Horizon Natural Resource 

Damage Assessment Trustees, 2016). The Final PDARP/PEIS considers programmatic alternatives 

to restore natural resources, ecological services, and recreational use services damaged or lost 

since the 2010 Deepwater Horizon explosion, oil spill, and response. The Final PDARP/PEIS 

includes an assessment of “injury” to natural resources resulting from the Deepwater Horizon

explosion, oil spill, and response. The term “injury” refers to impacts of the spill and derives from the 

Oil Pollution Act of 1990, which requires an assessment of “[d]amages for injury to, destruction of, 

loss of, or loss of use of, natural resources...” (Deepwater Horizon Natural Resource Damage 

Assessment Trustees, 2016). The Final PDARP/PEIS is concerned with impacts to the public’s 

natural resources and the services provided by those resources, such as recreation. It does not 

analyze economic harm to private parties and governments caused by the spill.

Combining direct observations, remote-sensing data, field sampling data, and other lines of 

evidence, the Final PDARP/PEIS estimates that Deepwater Horizon oil created 112,115 km2

(43,300 mi2

) of detectable oil slicks on the sea surface. Oil sank to the seafloor over an area of 

approximately 1,030 km2 (400 mi2

) and contacted >2,100 km (1,300 mi) of shorelines from Texas to 

the Florida Panhandle. Natural resources were exposed to oil, dispersant, or both across a broad 

range of habitats, including the deep-sea, water-column, sea-surface, and nearshore habitats such 

as beach, marsh, mangrove, and submerged aquatic vegetation. A wide variety of biota, including 

marine mammals, sea turtles, fish and shellfish, benthic communities, and birds, were exposed to oil 

and/or dispersant throughout the northern GOM. Natural resources were exposed through various 

pathways, including direct exposure and contact with contaminated water, air, vegetation, and 

sediments. Despite natural weathering processes over the past 5 years, oil persists in some 

habitats where it continues to expose resources in the northern GOM (Deepwater Horizon Natural 
4-20 Description of the Affected Resources and Impact Analysis

Resource Damage Assessment Trustees, 2016), and impacts to various biotic communities persists, 

resulting in new baseline conditions for several living resources and habitats.

The following Federal agencies are the designated natural resource Trustees under Oil 

Pollution Act of 1990 (OPA) for the Deepwater Horizon oil spill:

• the U.S. Department of the Interior, as represented by the Fish and Wildlife 

Service, Bureau of Land Management, and National Park Service;

• the U.S. Department of Commerce, as represented by the National Oceanic and 

Atmospheric Administration;

• the U.S. Environmental Protection Agency; and

• the U.S. Department of Agriculture.

The following State agencies are designated natural resources Trustees under the OPA and 

are currently acting as Trustees for Deepwater Horizon oil spill:

• the State of Florida’s Department of Environmental Protection and Fish and 

Wildlife Conservation Commission;

• the State of Alabama’s Department of Conservation and Natural Resources 

Geological Survey of Alabama;

• the State of Mississippi’s Department of Environmental Quality;

• the State of Louisiana’s Coastal Protection and Restoration Authority, Oil Spill 

Coordinator’s Office, Department of Environmental Quality, Department of 

Wildlife and Fisheries, and Department of Natural Resources; and

• the Texas Parks and Wildlife Department, Texas General Land Office, and Texas 

Commission on Environmental Quality.

Each of the Federal and State co-Trustees participated as a cooperating agency pursuant to 

NEPA (40 CFR § 1508.5).

A great deal of scientific data regarding the potential short-term and long-term impacts of the 

Deepwater Horizon explosion, oil spill, and response on Gulf of Mexico resources has become 

available, and studies focusing on long-term effects are continuing. It could be many years before 

the information regarding the long-term effects becomes available via the Natural Resource Damage 

Assessment (NRDA) process, BOEM’s Environmental Studies Program, and numerous studies by 

other Federal and State agencies and academia. Nonetheless, the subject-matter experts who 

prepared this Programmatic EIS acquired and used new scientifically credible information that was 

available, determined that additional information was not available absent exorbitant expenditures or 

could not be obtained regardless of cost in a timely manner, and where gaps remained, exercised 
Gulf of Mexico G&G Activities Programmatic EIS 4-21

their best professional judgment to extrapolate baseline conditions and impact analyses using 

accepted methodologies based on credible information. This approach complies with the 

requirements of §1502.22 of the CEQ regulations regarding how agencies should address 

incomplete or unavailable information. Relevant baseline conditions, including creditable scientific 

information regarding the potential short-term and long-term impacts of the Deepwater Horizon

explosion, oil spill, and response on Gulf of Mexico resources that are relevant to the proposed 

action, have been incorporated in the appropriate resource chapters.

4.2 MARINE MAMMALS

4.2.1 Description of the Affected Environment

In the northern GOM, there are 22 marine mammal species likely to occur within the AOI, 

based on current distributional data (Davis and Fargion, 1996; Jefferson et al., 2008; Southall et al., 

2007; Waring et al., 2013, 2014, and 2015; Würsig et al., 2000). These species represent two 

taxonomic orders: Cetacea (whales and dolphins) and Sirenia (manatees) (Table 4.2-1). Cetacea 

is subdivided into two suborders: Mysticeti (baleen whales) and Odontoceti (toothed whales and 

dolphins). Seven additional cetacean species may occur within the GOM, but they are considered 

rare or extralimital within the region (i.e., their presence in the GOM would be outside of their normal 

distributional range) (Waring et al., 2014). These include six mysticete species (i.e., North Atlantic 

right whale [NARW], common minke whale, sei whale, blue whale, fin whale, and humpback whale] 

and one odontocete species (i.e., Sowerby’s beaked whale). Because these species are not regular 

inhabitants of the GOM and therefore are unlikely to be exposed to Gulf of Mexico G&G activities, 

they are not considered further in this analysis. 

A summary of information on these species is presented in Table 4.2-1, including distribution 

and abundance, habitat, behavior, vocalizations and hearing, and status (ESA/MMPA stock). 

Information details for each species are provided in Appendix E. Estimates of the relative 

abundance (or density) of each species, as presented in Tables 4.2-1 and 4.2-2 and in Appendix E, 

are derived from two sources: the Cetacean Density and Distribution Mapping Working Group 

(CetMap) database (Roberts et al., 2016) and the NMFS Stock Assessment Reports (SARs). 

CetMap data include species-specific spatial and temporal information to estimate density using 

predictive environmental factors from the Marine Geospatial Ecology Laboratory (Duke University) 

model (Roberts et al., 2016). The NMFS’ SARs are prepared annually by the NMFS in consultation 

with regional Scientific Review Groups (SRGs). Each report includes stock-specific information 

(when available) but does not provide spatial-temporal density information (Waring et al., 2014).

Data from shipboard cetacean surveys of the shelf-edge and oceanic northern GOM 

conducted from 1991 to 2001 were reviewed by Maze-Foley and Mullin (2006) to document habitat 

partitioning between species. From these studies, bottom depth and seafloor topography in the 

GOM showed the clearest indication of habitat partitioning in the areas surveyed. From these 

results, marine mammals within the GOM may generally be divided into two communities: a 

continental shelf community and an oceanic community. The continental shelf community included 

two cetacean species, the common bottlenose dolphin and the Atlantic spotted dolphin, with 
4-22 Description of the Affected Resources and Impact Analysis

occasional sightings of the Florida manatee in coastal and offshore (near-coastal) waters. The 

oceanic community included 19 cetacean species (Mullin et al., 1994; Hansen et al., 1996; Mullin 

and Hansen, 1999; Mullin and Hoggard, 2000; Fulling et al., 2003; Davis and Fargion, 1996). Most 

oceanic species were widely distributed across the GOM within broad or somewhat specific depth 

ranges of the continental slope. Sperm whales were widely distributed within the GOM. Based on 

satellite tracking studies conducted by Jochens et al. (2008), the GOM sperm whale’s home range 

(defined as an area over which an animal or group of animals regularly travels in search of food or 

mates and that may overlap with those of neighboring animals or groups of the same species) is 

broad, comprising nearly the entire GOM in waters deeper than 500 m (1,640 ft). By contrast, the 

GOM sperm whale’s composite core area (defined as a section of the home range that is utilized 

more thoroughly and frequently as primary locales for activities such as feeding) generally includes 

Mississippi Canyon, the Mississippi River Delta, and (to a lesser extent) the Rio Grande Slope 

(Jochens et al., 2008). These data support the fact that sperm whales aggregate in the Mississippi 

Canyon area, including the proposed closure area, but regularly move across the northern GOM

continental slope. Some oceanic species also showed a localized distribution (east or west) within a 

specific depth range. Most sightings of Bryde’s whales were concentrated along the northeastern 

shelf-edge in the De Soto Canyon area, within a very narrow water-depth range (199 to 302 m 

[653 to 991 ft]). Sightings of spinner and Clymene dolphins were at similar depths, east or west, 

respectively, of the Mississippi River. Most killer whales occurred in the central GOM in waters 

>700 m (2,297 ft). False killer whale sightings were uncommon, but nearly all occurred in the far 

eastern GOM in a wide range of depths.

Survey data suggest that species richness and abundance of oceanic cetaceans remain high 

throughout the year, with no common species vacating slope waters seasonally. Factors that may 

affect the distribution and abundance of cetaceans within the GOM (both spatially and temporally) 

include physicochemical and biotic variables such as seawater temperature and enhanced 

productivity from Mississippi River outflow and from the upwelling of nutrients from the Loop Current 

(LC) and anticyclonic eddies that are periodically shed from the LC (Maze-Foley and Mullin, 2006); 

Biggs and Ressler, 2001; Davis and Fargion, 1996).

All marine mammal species within U.S. waters are protected under the MMPA. Two species, 

the sperm whale (Northern Gulf of Mexico Stock) and the Florida subspecies of the West Indian 

manatee, are federally listed as endangered species and receive further protection under the ESA 

(Waring et al., 2010), although there is currently a proposed rule to reclassify the manatee as 

threatened based on review of best available scientific data (81 FR 999). Under the ESA, a species 

is considered endangered if it is “in danger of extinction throughout all or a significant portion of its 

range.” A species is considered threatened if it “is likely to become an endangered species within 

the foreseeable future throughout all or a significant portion of its range.”

In 2013, NOAA published a 90-day positive finding to list the sperm whales in the GOM as a 

Distinct Population Segment (DPS) under the ESA, and subsequently initiated a review of the sperm 

whale status in the GOM. That 90-day review resulted in NOAA determining that the action to 

designate a DPS was not warranted and its listing status remains endangered.
Gulf of Mexico G&G Activities Programmatic EIS 4-23

The Northern GOM stock of the Bryde’s whale is currently being considered for listing in the 

GOM under the ESA. A year-round Biologically Important Area (BIA) has been designated for the 

resident Bryde’s whale population in this area of the eastern GOM (LaBrecque et al., 2015; Širović 

et al., 2014; Maze-Foley and Mullin, 2006).

The MMPA prohibits, with certain exceptions, the “take” of marine mammals in U.S. waters 

and by U.S. citizens on the high seas, and the importation of marine mammals and marine mammal 

products into the U.S. “Take” is defined under the MMPA as “to harass, hunt, capture, or kill, or 

attempt to harass, hunt, capture, or kill any marine mammal” (16 U.S.C. § 1362). Harassment, 

under the 1994 Amendments to the MMPA, is further subdivided into two levels: Level A and 

Level B (USDOC, NOAA Fisheries, 2015). Level A harassment is defined as any act of pursuit, 

torment, or annoyance that has the potential to injure a marine mammal or marine mammal stock in 

the wild. Level B harassment has the potential to disturb a marine mammal or marine mammal 

stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, 

breathing, nursing, breeding, feeding, or sheltering but which does not have the potential to injure a 

marine mammal or marine mammal stock in the wild.

Some marine mammal stocks (defined as a group of nonspecific individuals that are 

managed separately [Wang, 2002]) may be designated as strategic under the MMPA, which requires 

the jurisdictional agency (NMFS or FWS) to impose additional protection measures. According to 

the MMPA, a stock is considered strategic if

• direct human-caused mortality exceeds its potential biological removal (PBR) 

level (defined as the maximum number of animals, not including natural mortality, 

that can be removed from the stock while allowing the stock to reach or maintain 

its optimum sustainable population [OSP] level);

• it is listed under the ESA;

• it is declining and likely to be listed under the ESA; or

• it is designated as depleted under the MMPA (USDOC, NMFS, 2015a).

The OSP is defined by the MMPA (Section 3[9]) as the number of animals within any 

population stock that will result in the maximum productivity of the population or the species, 

considering the carrying capacity of the habitat and the health of the ecosystem of which they are a 

part (16 U.S.C. § 1362(3)(9)). A depleted stock is defined by the MMPA (USDOC, NMFS, 2015a) as 

any case in which 

• the Secretary (of the Interior or Commerce, depending on the species), after 

consultation with the Marine Mammal Commission and the Committee of 

Scientific Advisors on Marine Mammals established under MMPA Title II, 

determines that a species or population stock is below its OSP;
4-24 Description of the Affected Resources and Impact Analysis

• a state, to which authority for the conservation and management of a species or 

population stock is transferred under Section 109, determines that such species 

or stock is below its OSP; or 

• a species or population stock is listed as an endangered species or a threatened 

species under the ESA.

The Deepwater Horizon explosion, oil spill, and response have impacted marine mammals 

that have come into contact with oil and remediation efforts (including use of dispersants). The 

NRDA process, evaluating the possible effects of the Deepwater Horizon explosion, oil spill, and 

response, focused the quantification efforts on bottlenose dolphins exposed to oiling. The Barataria 

Bay and Mississippi Sound stocks of the common bottlenose dolphin (Tursiops truncatus) were two 

of the best-studied populations and experienced some decline. Dolphins in the concentrated oiling 

locations have shown overall poor health and prevalence of poor body condition, disease, and 

abnormalities as compared with bottlenose dolphins in the Gulf of Mexico that were not exposed to 

oiling (Schwacke et al., 2013; Venn-Watson et al., 2015).

The types of impacts observed are consistent with both the known routes of exposure and 

the effects reported in the oil toxicity literature (in other mammals); however, very few studies have 

examined a dose-specific impact in marine mammals. The Final PDARP/PEIS concluded that, 

overall, 31 stocks of cetaceans were exposed to Deepwater Horizon oil (Deepwater Horizon Natural 

Resource Damage Assessment Trustees, 2016). While smaller percentages of the oceanic stocks 

were exposed to oil, these stocks still experienced mortality, reproductive failure, and adverse health 

effects (Schwacke et al., 2014).

An unusual mortality event (UME) for cetaceans that encompassed the northern GOM from 

the Florida panhandle west to the Louisiana-Texas border began in March 2010, prior to the 

Deepwater Horizon oil spill, and continued through July 2014 (USDOC, NMFS, 2016b). A UME is 

defined under the MMPA as “a stranding that is unexpected; involves a significant die-off of any 

marine mammal population; and demands immediate response.” The UME investigation and the 

Deepwater Horizon Natural Damage Resource Assessment have determined that the Deepwater 

Horizon oil spill resulted in the death of marine mammals and is the most likely explanation of the 

elevated stranding numbers in the northern Gulf of Mexico after the spill.

Additional information pertaining to this resource and NMFS’ determination of the effects of 

the Deepwater Horizon explosion, oil spill, and response may be found in the Final PDARP/PEIS 

(Deepwater Horizon Natural Resource Damage Assessment Trustees, 2016).

As stated above, a great deal of scientific data regarding the potential short-term and longterm impacts of the Deepwater Horizon explosion, oil spill, and response on GOM resources has 

become available. Conditions in the GOM, post- Deepwater Horizon, however, continue to change. 

As such, studies focusing on possible long-term effects are continuing. It could be many years 

before the information regarding the long-term effects becomes available via the Natural Resource 
Gulf of Mexico G&G Activities Programmatic EIS 4-25

Damage Assessment (NRDA) process. The Final PDARP/PEIS information is noted in this 

Programmatic EIS to simply provide all known best-available information regarding impacts to the 

GOM marine environment, as a whole, from the Deepwater Horizon explosion, oil spill, and 

response

Further, where information was incomplete or unavailable, BOEM complied with its 

obligations under NEPA to determine if the information was relevant to reasonably foreseeable 

significant adverse impacts; if so, whether it was essential to a reasoned choice among alternatives; 

and, if it is essential, whether it can be obtained and whether the cost of obtaining the information is 

exorbitant, as well as whether generally accepted scientific methodologies can be applied in its place 

(40 CFR § 1502.22). The most notable incomplete or unavailable information relates to some 

aspects of the effects from the Deepwater Horizon explosion, oil spill, and response. Nonetheless, 

BOEM’s subject-matter experts acquired and used newly available, scientifically credible 

information; determined that other additional information was not available absent exorbitant 

expenditures or could not be obtained regardless of cost in a timely manner; and where gaps 

remained, exercised their best professional judgment to extrapolate baseline conditions and impact 

analyses using accepted methodologies based on credible information. While incomplete or 

unavailable information could conceivably result in potential future shifts in baseline conditions of 

habitats that could affect BOEM’s decisionmaking, BOEM has determined that it can make an 

informed decision even without this incomplete or unavailable information. BOEM’s subject-matter 

experts can apply and have included other scientifically credible information using accepted 

theoretical approaches and research methods, such as information on related or surrogate species. 

Moreover, BOEM will continue to monitor these resources for effects caused by the Deepwater 

Horizon explosion, oil spill, and response, and will ensure that future BOEM environmental reviews 

take into account any new information that may emerge.

4.2.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, IPFs that may impact marine mammals within the AOI include 

(1) active acoustic sound sources (e.g., airguns; non-airgun HRG sources such as high-resolution 

boomers, sparkers, and CHIRP subbottom profilers; SBESs and MBESs; and side-scan sonars); 

(2) vessel and equipment noise; (3) vessel traffic (i.e., physical disturbance to and risk of collisions); 

(4) aircraft traffic and noise (e.g., helicopters, fixed-wing aircraft); (5) trash and debris (i.e., ingestion 

of and entanglement in); (6) entanglement (i.e., with acoustic buoy releases, tethered acoustic 

pingers, and nodal tethering lines); and (7) accidental fuel spills.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact-level categories. In contrast, the analysis 

of impacts associated with Alternatives B through G are organized by alternative-specific mitigation 

measures and how each of these measures may reduce impact levels when compared with

Alternative A. 
4-26 Description of the Affected Resources and Impact Analysis

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For marine 

mammals, the significance criteria below have been used to evaluate the level of impact for each 

IPF.

Nominal impacts to marine mammals include those where no potential measurable impacts 

to local populations are observed or expected. Nominal impacts are limited to potential minimal, 

short-term behavioral or other potential low level impacts on individuals (low numbers in relation to 

population [stock], low severity, and short duration). No potential mortalities or physical injuries are 

included, and no potential effects on individual fitness (e.g., reduction in reproductive success or 

survivorship) or on populations are expected.

Minor impacts to marine mammals include those that are not extensive or severe, and are 

expected to affect individuals or groups from local populations within the AOI. Minor impacts include 

potential limited behavioral disturbance and potential low numbers of non-fatal physical injuries in 

relation to population (stock). These potential effects include only a low likelihood of fitness impacts 

on a low number of individuals in relation to population (stock). No potential mortalities are included, 

and there are no impacts on population rates.

Moderate impacts to marine mammals at the local population (stock) level may be either 

extensive (potentially affecting large numbers of individuals [or percentage of the local stock] within 

regions of the AOI) but not severe, or may be severe but not extensive. Moderate impacts include 

potential significant behavioral disturbance and physical (including auditory) injuries of more than low 

numbers of individuals in relation to population (stock), including the likelihood of fitness effects on 

more than a low number of individuals in relation to population (stock). Moderate impacts also 

include potential mortality of individuals (but below that of Potential Biological Removal for the stock 

or species), including some negative population-level impacts to stable or increasing populations, 

but not outside of the existing known variation around measured population trend (i.e., the continued 

viability of the local population or stock is not threatened and the annual rates of recruitment or 

survival of the local population or stock are not seriously affected).

Major impacts to marine mammals would be extensive and severe if they actually occur. 

Impacts to marine mammals are considered major if they include potentially extensive levels of lifethreatening or debilitating injury or mortality in sufficiently high numbers (above that of Potential 

Biological Removal for the stock or species) that the continued viability of the population is 

threatened, including serious diminishment of annual rates of recruitment or survival. Declining 

species are considered to have major impacts if their population rates are potentially adversely 

affected at all, and stable or increasing species are considered to have major impacts if their 
Gulf of Mexico G&G Activities Programmatic EIS 4-27

population rates are potentially reduced beyond previously measured natural variation, as a result of 

mortality or adverse energetic or health impacts from severe behavioral disturbance or injury. If 

there is not enough data to assess trends, or populations are unknown, negative population-level 

effects equate to “major” impacts.

4.2.2.1 Impacts of Routine Activities

4.2.2.1.1 Characteristics of Active Acoustic Sound Sources

Active acoustic sound sources included in the proposed action are airguns and various 

electromechanical sources. Source characteristics are summarized in Table 3.3-2 and detailed 

characteristics and acoustic modeling assumptions are presented in Appendix D. The two major 

sound source groups (i.e., airgun and electromechanical) are discussed separately.

Airgun Survey Activities

Airguns would be used as sound sources during deep-penetration seismic airgun surveys as 

well as some shallow-penetration HRG surveys to support oil and gas surveys and renewable 

energy activities (Appendix F). Deep-penetration surveys include 2D and 3D towed-streamer 

surveys, 2D and 3D OBC and OBN surveys, WAZ and related multi-vessel surveys (e.g., coil), 

vertical cable surveys, and 4D surveys. Shallow-penetration airgun seismic surveys include the use 

of a single airgun with HRG equipment (electromagnetic activities described below).

For this Programmatic EIS, one large airgun array and one small airgun are used to 

represent general configurations and their potential impacts to marine mammals within the AOI 

(Appendix D). The situations simulated are complex and evolving. The time period evaluated was 

10 years of future survey efforts using representative surveys whose precise design, location, and 

time of performance are not known. There is presently a great of variety in survey and source 

configurations, and new configurations, sources, or use of sources are likely to be developed. The 

details of marine mammal density, distributions, and behavior patterns are imprecisely known and 

change as animal populations vary from year to year and location to location.

• Large Airgun Array (approximately 8,000 in3

) – This array is used to represent 

sound sources for deep-penetration seismic airgun surveys, including 2D, 3D, 

4D, WAZ, VSP, and other variations. 

• Small Airgun Array (90 in3

) – A single airgun is used to represent sound sources 

for some HRG airgun surveys to assess shallow hazards and benthic habitats at 

oil and gas exploration sites.

Representative broadband source levels are 248 dB zero-to-peak SPL re 1 μPa at 1 m 

measured broadside for the large airgun array and 228 dB zero-to-peak SPL re 1 μPa at 1 m for the 

small airgun array (Table 3.3-2). Although airguns typically have a frequency range between 10 and 

2,000 Hz, most of the acoustic energy is under 600 Hz.
4-28 Description of the Affected Resources and Impact Analysis

Electromechanical (Non-Airgun) Survey Activities

The HRG surveys use electromechanical acoustic sources to support projects or surveys in 

all three program areas (though they also may be used in conjunction with airguns). Typical nonairgun HRG surveys utilize one or more of the following high-frequency acoustic sources:

• pinger (2,000 Hz); 

• sparker (50 to 4,000 Hz); 

• boomer (300 to 3,000 Hz); 

• CHIRP subbottom profiler (4 to 24 kHz);

• side-scan sonar (16 to 1,500 kHz); 

• SBES (12 to 240 kHz); and

• MBES (50 to 400 kHz).

Details of each of these electromechanical sound sources and their applications are in 

Appendix F, Section 1.3. 

Background: Potential Effects of Noise on Marine Mammals

Underwater noise has been divided into two main types: (1) pulsed (or impulsive), which is 

divided into single or multiple pulses; and (2) continuous, non-pulsed sounds (Southall et al., 2007; 

Science Communication Unit, 2012). Impulsive noises are transient signals that arise as the result 

of a sudden release of energy (Hamernik and Hsueh, 1991). As such, they are characterized by

extremely rapid rise rates in amplitude over time (rise time), minimal duration, and a rapid decay in 

amplitude. Explosions, pile driving, and seismic surveys are examples of impulsive noise. 

Continuous noise has a longer duration, typically with slower rise and decay times. The sounds of 

an outboard boat engine or wind turbines are examples of non-pulsed, continuous-type noise.

Underwater noise sources in the proposed action include impulsive sound sources such as 

airguns, boomers, subbottom profilers, multibeam echosounders and side-scan sonars, as well as 

continuous sources such as vessel and aircraft noise, and geotechnical drilling. Chapter 3.3 and 

Appendix F provide a description of these noise sources. Overall, the potential for noise impacts 

from these sound sources on marine mammals is highly variable and depends on the specific 

circumstances of a given situation. Furthermore, the same sound source can propagate differently 

depending on the physical environment. How a sound from a specific source propagates through a 

particular environment depends on a variety of factors, including physical environment factors (e.g., 

salinity, temperature, bathymetry, seafloor type, and tow depth), sound characteristics associated 

with different sources (e.g., source level, directionality, source type, and duration for both impulsive 

or continuous signals), frequency (i.e., higher frequencies dissipate faster, lower frequencies may 

travel farther depending on water depth), and intensity (i.e., decibel level). A review of marine 

mammal hearing and sensitivity to acoustic impacts is presented in Appendix H. More information 
Gulf of Mexico G&G Activities Programmatic EIS 4-29

on acoustical properties and propagation of sound sources under the proposed action can be found 

in Appendix D. 

Past studies on the reactions of animals to noise have shown widely varied responses 

depending on the species as well as the individual’s age, gender, and the activity in which the animal 

was engaged in at the time of sound exposure (Gordon et al., 2003). Where there is an overlap 

between noise sources and the sound frequencies used and heard by marine life, there is the 

potential for sound to interfere with important biological functions. Noise, either natural or 

anthropogenic, can adversely affect marine life in various ways. Four zones of influence from noise 

are offered by Richardson et al. (1995) and summarized by Gordon et al. (2004):

(1) zone of audibility – the area in which the sound is above the animal’s hearing 

threshold and detectable above background noise; 

(2) zone of responsiveness – the region in which behavioral reactions in response 

to the sound occur; 

(3) zone of auditory masking – the area in which the sound may mask biologically 

significant sounds (e.g., sounds being heard and used for communication, 

navigation, or the location of conspecifics and prey); and 

(4) zone of hearing loss, discomfort, or injury – the area in which the sound level is 

sufficient to cause TTS or auditory injury permanent threshold shift (PTS) and 

potential physiological effects.

These zones of influence broadly define the nature of potential response and impact from 

acoustic exposure. The range of potential effects from noise, in order of decreasing severity and 

modified slightly from the four zones initially outlined by Richardson et al. (1995), includes death, 

non-auditory physiological effects, auditory injury/hearing threshold shift, masking, and stress and 

disturbance, including behavioral response (Richardson et al., 1995; NRC, 2003a and 2005; 

Nowacek et al., 2004; Southall et al., 2007). More severe potential effects (e.g., temporary or 

permanent hearing loss) could occur when exposure is close to a sound source (i.e., the magnitude 

and probability of some effects decrease with increasing distance from a sound source) and when 

duration of the exposure(s) is longer. Limited data on potential effects to manatees are available, 

with no mention of manatees in Southall et al. (2007) or the draft NOAA guidance (USDOC, NMFS, 

2015b). Given the coastal distribution of manatees, there is the potential for indirect impacts from 

activities in nearshore, State waters (e.g., vessel strikes), but no direct impacts of noise are 

expected.

Death and Non-Auditory Physiological Effects from Various Sound Sources

Direct physical injury, which could potentially result in death, may occur from exposure to 

high levels of sound or, more commonly, to shock waves associated with sound-producing events 

such as underwater blasting and airguns, where the velocity of expansion of the bubble causing the 

pulse is higher than the speed of sound in water. These shock wave pulses typically are short, with 
4-30 Description of the Affected Resources and Impact Analysis

peak pressures that have been hypothesized to possibly cause damage to internal organs or airfilled body cavities (e.g., lungs) (Yelverton et al., 1973; Goertner, 1982; Young, 1991). Data on 

direct physical injuries are limited to anecdotal or forensic investigations after accidental events 

because ethical considerations and legal mandates in the U.S. prevent direct empirical methods to 

measure such impacts in marine mammals. However, such observations (e.g., Todd et al., 1996; 

Danil and St. Leger, 2011) and modeling based on impact data for terrestrial animals (e.g., Fletcher 

et al., 1976; Bauman et al., 1997) and the human vestibular system (e.g., Clark et al., 1996), as well 

as other organs (e.g., lungs) for underwater sound exposures (e.g., Cudahy and Ellison, 2002), 

suggest that marine mammals could be susceptible to direct physical injury to particular organ 

systems and tissues following intense exposure (Ketten, 1995; Hildebrand, 2005). While there are 

no data that indicate that G&G activities have caused this level of injury, possible types of nonauditory physiological effects or injuries that could potentially occur include neurological effects, gas

embolisms (i.e., decompression sickness; Ketten, 2014), fat embolisms, resonance effects, and 

other types of organ or tissue damage (Tasker et al., 2010). However, a marine mammal would 

have to be very close to the source for direct physical injury to occur, and BOEM believes that

mitigation and monitoring measures would prevent marine mammals from being close to the source.

Exposure to intense underwater sound may not directly result in death or injury. However, it 

may be one of the indirect causative factors in death or injury to marine mammals. According to the 

U.S. Navy’s Atlantic Fleet Training and Testing Final EIS (U.S. Dept. of the Navy, 2013), “Sonar use 

during exercises involving U.S. Navy (most often in association with other nations’ defense forces) 

has been identified as a contributing cause or factor in five specific mass stranding events: Greece 

in 1996; the Bahamas in March 2000; Madeira Island, Portugal in 2000; the Canary Islands in 2002; 

and Spain in 2006. These five mass strandings resulted in approximately 40 known, scientifically 

verifiable sonar-related deaths among cetaceans consisting mostly of beaked whales.” Exposure to 

the noise from seismic surveys has been implicated in the deaths of two beaked whales in the Gulf 

of California in 2002 (Lamont-Doherty Earth Observatory survey), although no direct correlation has 

been proven (Cox et al., 2006). In these circumstances, exposure to impulsive acoustic energy has 

been considered to have been a potential indirect cause of the death of marine mammals (Cox et al., 

2006). While large airgun arrays have a similar RMS source level to U.S. Navy tactical sonars, there 

are substantial differences in duration, frequency, and mode of operation between these two classes 

of sound sources.

In September 2013, an International Scientific Review Panel released a report following an 

investigation of a 2008 mass stranding of approximately 100 melon-headed whales in the Loza 

Lagoon system in Madagascar (Southall et al., 2013). The development of this investigation and 

report was supported by the International Whaling Commission, Marine Mammal Commission, 

NOAA, BOEM, ExxonMobil, Wildlife Conservation Society, International Fund for Animal Welfare, 

and the Government of Madagascar. The International Scientific Review Panel determined that the 

use of a 12-kHz MBES system (i.e., Kongsberg EM 120 MBES with a source level of 236 to 246 dB 

re 1 μPa at 1 m, sound exposure level [SEL] per pulse of 218 to 224 dB re 1 μPa2

•s at 1 m, pulse 

rate of ≤5 Hz, and pulse duration of 2, 5, or 15 milliseconds [ms]) was “the most plausible and likely 

initial behavioral trigger of the stranding event, but that a variety of secondary factors contributed to 
Gulf of Mexico G&G Activities Programmatic EIS 4-31

or ultimately caused mortalities...” (Southall et al., 2013). According to the report, this was the first 

time that a relatively high-frequency mapping sonar system had been associated with a stranding 

event.

Given the predominant low-frequency sound sources, coupled with limited SPL durations, 

mode of operation, and directionality of large airgun arrays, and the mitigation and monitoring 

measures associated with Alternative A, it is not likely that geophysical survey activities would 

generate propagated SPLs strong enough to cause direct mortality (DNV Energy, 2007). However, 

as noted in the previous examples, there is the potential (albeit limited) for sound sources to lead to 

indirect mortality through strandings under certain circumstances. In addition, survey protocols and 

underwater noise mitigation procedures (Appendix B) would be implemented to decrease the 

potential for any marine mammal to be within the exclusion zone of an operating airgun array, 

thereby avoiding the highest SPLs and minimizing their exposure to these sound sources.

Auditory Injuries – Hearing Threshold Shift

The minimum sound source level an animal can hear at a specific frequency is called the 

hearing threshold at that frequency. Sounds above a hearing threshold are accommodated until a 

certain level of sound intensity or duration is reached, after which the ear’s hearing sensitivity 

decreases (the hearing threshold increases) (Southall et al., 2007). This process is referred to as a 

threshold shift, meaning that only sounds louder than a certain level will be heard within a certain 

frequency range. Threshold shifts can be temporary (TTS) or permanent (PTS) and are defined as 

follows (Southall et al., 2007; Au and Hastings, 2008):

• TTS – also known as auditory fatigue, the milder form of hearing impairment that 

is non-permanent and reversible, results from exposure to high-intensity sounds 

for short durations or lower intensity sounds for longer durations, both conditions 

of which are species-specific and leads to an elevation in the hearing threshold, 

which means it is more difficult for an animal to hear sounds. The TTS can last 

for minutes, hours, or days; the magnitude of the TTS depends on the level 

(frequency and amplitude), energy distribution, and duration of the noise 

exposure among other considerations. Because TTS is recoverable, it does not 

constitute an injury (Ward, 1997).

• PTS – a permanent elevation in the hearing threshold and permanent loss of 

hearing, which is considered an auditory injury. Because few direct data are 

currently available regarding noise levels that might induce PTS in marine 

mammals, PTS onset thresholds are inferred from TTS marine mammal data 

(USDOC, NMFS, 2013b). The PTS is attributed to exposure to very high peak 

pressures and short rise times or very prolonged or repeated exposures to noise 

strong enough to elicit TTS. Permanent damage to the inner ear, such as 

irreparable damage to the sensory hair cells in the cochlea, is associated with 

noise-induced PTS. The relationship between the onset of PTS and TTS is 

complex and not completely understood. Using psychophysical methods, Kastak 
4-32 Description of the Affected Resources and Impact Analysis

et al. (2008) did find that, after a harbor seal was exposed twice to a 4.1-kHz 

fatiguing sound, the animal exhibited PTS of 7 to 10 dB within 2 months.

Several factors relate to the type and magnitude of threshold shift, including exposure level, 

frequency content, duration, and temporal pattern of exposure. A range of mechanical effects (e.g., 

excessive vibrations of the inner ear stereocilia [organelles of hair cells that sense fluid motion] and 

hair cells may cause structural damage) and metabolic processes (e.g., inner ear hair cell 

metabolism such as energy production, protein synthesis, and ion transport) within the auditory 

system underlie TTS and PTS. An additional discussion of TTS and PTS is presented in 

Appendix H. 

Auditory impairment, either temporary or permanent, is a possibility when marine mammals 

are exposed to underwater noise. The minimum SPL (or SEL) necessary to cause PTS is higher 

than the level that induces TTS, although there are insufficient data to determine the precise 

differential. Data indicate that TTS onset in marine mammals is more closely correlated with the 

received SEL than with SPLrms and that received sound energy over time, not just the single 

strongest pulse, should be considered a primary measure of potential impact (Southall et al., 2007).

For cetaceans exposed to underwater acoustic sources, excluding tactical military sonar and 

explosives, NMFS currently uses the acoustic threshold of 180 dB re 1 μPa rms for cetaceans as the 

onset of PTS. This threshold has been in place for some time, and the available data on hearing 

and noise impacts are expanding rapidly. Southall et al. (2007) provided a comprehensive summary 

of noise exposure results and offered a series of new approaches to noise impact determinations for 

marine mammals, with the U.S. Navy (Finneran and Jenkins, 2012; Finneran, 2015) and draft NOAA 

guidance (USDOC, NMFS, 2015b) further refining the methodology, criteria, and thresholds of 

acoustic impact analyses for marine mammals. This is the second draft guidance from NOAA, which 

is still draft considerations and which was not available when the acoustic exposure analysis was 

conducted. New data and information continue to become available (e.g., Finneran and Schlundt, 

2011; Ellison et al., 2012; Kastelein et al., 2014; Tougaard et al., 2014), as this is an active area of 

scientific research.

Southall et al. (2007) segregated marine mammals into functional hearing groups 

(Table 4.2-3) and categorized sound sources based on their acoustic and temporal properties. 

Three sound source categories (i.e., single pulse, multiple pulses, and non-pulses [continuous]) 

were defined based on an understanding of sound exposure, auditory fatigue, and acoustic trauma 

in terrestrial mammals and applicable damage risk criteria in humans. They also devised dual metric 

criteria (peak pressure and SEL) for both TTS and PTS onsets, as well as the incorporation of 

frequency weighting functions (M-weighting) to account for the differential hearing abilities in the 

different functional hearing groups.

As in Southall et al. (2007), NOAA’s first and second draft underwater acoustic guidances 

(USDOC, NMFS, 2013b and 2015b) delineated the acoustic threshold levels for the onset of PTS 

and TTS and also recommended the use of the dual criteria metrics of SEL (specifically, cumulative 
Gulf of Mexico G&G Activities Programmatic EIS 4-33

SEL [SELcum]) and peak SPL (SPLpeak) as most appropriate for establishing the onset levels for TTS 

and PTS in marine mammals (USDOC, NMFS, 2013b and 2015b). The SPLpeak threshold would be 

applied to unweighted (unfiltered) sound levels, while the SELcum metric would be calculated using 

M-weighting. Thus, any received noise that exceeds the SPLpeak or SELcum criterion for injury is 

assumed to cause tissue injury in an exposed marine mammal.

The SEL takes into account the duration of the sound exposure as well as the sound’s 

source level. Southall et al. (2007) defined SEL as “...a measure of energy. Specifically it is the dB 

level of the time integral of the squared instantaneous sound pressure normalized to a 1-s period.” 

This definition of SEL normalizes a single sound exposure to a duration of 1 second. Southall et al. 

(2007) did not specify a time period to capture the energy for multiple transmissions, but the typical 

application of these thresholds at that time nominally employed a time period of minutes or tens of 

minutes around the maximum signal received for this calculation. Additionally, Southall et al. (2007) 

suggested a 24-hr “rest time,” which was subsequently interpreted to be the time period necessary 

for an animal to return to a naive state before it could be potentially impacted again. In their most 

recent draft acoustic guidance, the USDOC, NMFS (2015b) intended the SEL metric to account for 

the accumulated exposure over the duration of the activity or over a 24-hr period, whichever was 

shorter; thus, SELcum is used. The SEL metric is advantageous because it can account for 

cumulative sound exposure, sounds of differing duration, and multiple sound exposures. The SEL

metric also allows comparison between different sound exposures based on total energy (i.e., 

calculation of a single exposure “equivalent” value) (Southall et al., 2007). It is worthwhile to note 

that this application of the SELcum approach does not include the possibility of recovery of hearing 

between repeated exposures.

Represented by dual criteria (SELcum and SPLpeak), the lowest received levels of impulsive 

sounds that might elicit auditory injury (PTS) according to Southall et al. (2007) are 198 dB re 

1 μPa2

•s (SEL, which is now changed to SELcum) or 230 dB re 1 μPa (SPLpeak) in cetaceans 

(Southall et al., 2007) (Table 4.2-4). The USDOC, NMFS (2015b) further refined the dual onset 

criteria for PTS, deriving different criteria for low-, mid-, and high-frequency cetaceans (Table 4.2-4). 

The PTS onset for impulsive sounds is 230 dBpeak for low- and mid-frequency cetaceans and 

202 dBpeak for high-frequency cetaceans. The SELcum criteria are 192 dB, 187 dB, and 154 dB, 

respectively, for low-, mid-, and high-frequency cetaceans. At the time that the potential impact 

calculations were made for this Programmatic EIS (refer to Appendix D), these SELcum criteria were 

not yet available (they had not been published or officially released); therefore, the best available 

estimate of these values were 192 dB, 187 dB, and 161 dB, respectively, for low-, mid-, and highfrequency cetaceans. The current NOAA regulatory thresholds, however, are based on SPLrms

metrics (i.e., 180 dB re 1 μPa [rms] for injury; 160 dB re 1 μPa [rms] for behavioral disturbance); the 

SPLrms metrics cannot be directly compared with the SPLpeak metrics. However, the analysis in 

Appendix D also includes the stepped threshold function that was developed and presented in 

Finneran and Jenkins (2012) and Wood et al. (2012). Further discussion of the current noise 

exposure thresholds is provided in a subsequent section titled “Acoustic Exposure Criteria.” 
4-34 Description of the Affected Resources and Impact Analysis

Sound sources used during G&G activities produce sound levels sufficient to cause TTS or 

PTS in marine mammals present within the range of operational sound sources, with range to 

exposure thresholds dependent upon the size of the sound source and other factors. A summary of 

active acoustic sound source impacts is provided later in this chapter, with full descriptions included 

in Appendix D. The predicted sound exposures are evaluated with both the current NMFS criteria 

as well as those presented in Southall et al. (2007). The two NOAA draft criteria (USDOC, NMFS, 

2013b and 2015b) were not employed, as the 2015 criteria are still in the draft stage considerations. 

Survey protocols and underwater noise mitigation procedures (Appendix B) would be implemented 

to decrease the potential for any marine mammal to be within the exclusion zone of an operating 

airgun array or other sound source, thereby avoiding the highest sound levels. However, this does 

not imply that animals will not be exposed to sound that exceeds threshold levels and, therefore, 

animals may still experience TTS or PTS due to exposure to a sound produced by proposed 

activities.

Auditory Masking

Noise can affect hearing as well as partially or completely reduce an individual’s ability to 

effectively communicate; detect important predator, prey, and conspecific signals; and detect 

important environmental features associated with spatial orientation (Clark et al., 2009). Increases 

in ambient noise levels can result in auditory masking, which is the reduction in the detectability of a 

sound signal of interest (e.g., communication calls and echolocation) due to the presence of another 

sound, which is usually noise in the environment and often is at a similar frequency. Under normal 

circumstances, in the absence of high ambient noise levels, an animal would hear a sound signal 

because it is above its absolute hearing threshold. Auditory masking prevents part or all of a sound 

signal from being heard and decreases the distances that underwater sound can be detected by 

marine animals (i.e., reduction in communication space). These effects could cause a long-term 

decrease in a marine mammal’s efficiency at foraging, navigating, or communicating (International 

Council for the Exploration of the Sea, 2005). For some types of marine mammals, specifically 

bottlenose dolphins, beluga whales, and killer whales, empirical evidence confirms that the degree of 

masking depends strongly on the relative directions at which sound arrives and the characteristics of 

the masking noise (Penner et al., 1986; Dubrovskiy, 1990; Bain et al., 1993; Bain and Dahlheim, 

1994).

Ambient noise from natural and anthropogenic sources can cause masking in marine 

animals, effectively interfering with the ability of an animal to detect a sound signal that it otherwise 

would hear. Spectral, temporal, and spatial overlap between the masking noise and the 

sender/receiver determines the extent of interference; the greater the spectral and temporal overlap, 

the greater the potential for masking. Naturally occurring ambient noise is produced from various 

sources, including environmental sounds from wind, waves, precipitation, earthquakes; biological 

sounds produced by animals; and thermal noise resulting from molecular agitation (at frequencies 

above 30 kHz) (Richardson et al., 1995). Marine biota produce sounds that contribute to the 

ambient noise environment. Fish, for example, create low-frequency sounds (50 to 2,000 Hz, most 

often from 100 to 500 Hz) that can be a significant component of local ambient sound levels (Zelick 
Gulf of Mexico G&G Activities Programmatic EIS 4-35

and Mann, 1999). Ambient noise also can be generated by anthropogenic sources such as boats 

and ships, sonars (military and commercial), geophysical exploration, acoustic deterrent devices, 

construction noise, and scientific research sensors. Ambient noise is highly variable in the shallower 

waters over continental shelves (Desharnais et al., 1999) where many anthropogenic activities 

occur, effectively creating a high degree of variability in the range at which marine mammals can 

detect anthropogenic sounds. In coastal waters, noise from boats and ships, particularly commercial 

vessels, are the predominant source of anthropogenic noise (Parks et al., 2011). Snyder and Orlin 

(2007) noted that shipping noise dominated the low frequencies (25 to 400 Hz) of the ambient 

underwater noise environment of the GOM.

Over the past 50 years, commercial shipping, the largest contributor of masking noise 

(McDonald et al., 2008), has increased the ambient sound levels in the deep ocean at low 

frequencies by 10 to 15 dB (Hatch and Wright, 2007). This increase in low-frequency ambient noise 

coincides with a significant increase in the number and size of vessels making up the world’s 

commercial shipping fleet (Hildebrand, 2009). Tournadre (2014) estimated from satellite altimetry 

data that, globally, ship traffic grew by approximately 60 percent from 1992 to 2002, at a nearly 

constant rate of approximately 6 percent per year; however, after 2002, the rate at which shipping 

increased rose steadily to >10 percent by 2011, except in 2008 to 2009, when ship traffic remained 

steady. Globally, Tournadre (2014) estimated that shipping between 1992 and 2011 grew by a 

factor of four, with the highest growth in the Indian and western North Pacific Oceans, especially in 

the continental seas along China; growth in shipping in the Atlantic Ocean and Mediterranean Sea, 

however, decreased after 2008. Aguilar-Soto et al. (2006) reported that the noise from a passing 

vessel masked ultrasonic vocalizations of a Cuvier’s beaked whale and reduced the maximum 

communication range by 82 percent when exposed to a 15-dB increase in ambient sound levels at 

the vocalization frequencies; the effective detection distance of the Cuvier’s beaked whale’s 

echolocation clicks was reduced by 58 percent. Low-frequency noise (20 to 200 Hz) from large 

ships overlaps the frequency range of acoustic vocalizations of some mysticetes, and increased 

levels of underwater noise have been documented in areas with high shipping traffic, causing 

responses in some mysticetes that have included habitat displacement; changes in behavior; and 

alterations in the intensity, frequency, and intervals of their calls (Rolland et al., 2012).

Marine mammals are able to compensate, to a limited extent, for auditory masking through a 

variety of mechanisms, including increasing source levels (Lombard effect) or durations of their 

vocalizations or by changing spectral and temporal properties of their vocalizations (Parks et al., 

2010; Hotchkin and Parks, 2013). In the presence of ship noise, beluga whales produced whistles of 

higher frequency and longer duration (Lesage et al., 1999). Di Iorio and Clark (2010) found that blue 

whales increased their rate of social calling in the presence of seismic exploration sparkers (plasma 

sound sources), which presumably represented a compensatory behavior to elevated ambient noise 

levels from seismic surveys. Bowhead whales were found to increase their calling rate in response 

to seismic airgun signals at low levels (approximately 94 dB re 1μPa2

-s, CSEL; integrated over 

10 minutes). However, when those signals exceeded approximately 127 dB CSEL, their calling rate 

began to decrease, and when it reached approximately 160 dB CSEL, the bowheads stopped calling 

completely (Blackwell et al., 2015). Note that these received levels were measured at a recorder 
4-36 Description of the Affected Resources and Impact Analysis

within 2 km (1 mi) of the whales; therefore, the received levels at the whales are approximations. 

These examples of baleen whale responses to sound are informative, even though these species 

are not found in the GOM. Several marine mammal species are known to increase the source levels 

of their calls in the presence of elevated sound levels (Dahlheim, 1987; Au, 1993; Lesage et al., 

1999; Terhune, 1999). Holt et al. (2009) studied the effects of anthropogenic sound exposure on the 

endangered southern resident killer whales in Puget Sound, reporting that these whales increased 

their call amplitude by 1 dB SPL for every 1 dB SPL increase in background noise (1 to 40 kHz). 

Castellote et al. (2012) reported that male fin whales from two different subpopulations not only 

modified their song characteristics during increased ambient noise conditions but also left the area 

for an extended period during seismic airgun activity, not returning for 14 days. Castellote et al. 

(2012) hypothesized that the fin whales modified their acoustic communications to compensate for 

the increased background noise and that the animals had a lower tolerance for seismic airgun noise 

than for shipping noise, perhaps having become desensitized to the ambient shipping noise. Melcón 

et al. (2012) found that blue whales stopped calling in the presence of mid-frequency active sonar 

transmissions and conversely increased their vocalization rate when the sonar was transmitting.

Sound sources used during geophysical survey activities could mask marine mammal 

communication and monitoring of the environment around them if the hearing sensitivities of the 

marine mammals present coincide with the frequency of the sound source being used. As airgun 

signals propagate away from the source, their amplitude drops, which reduces their masking effect. 

However, the multipath effects of propagation increase the duration of the signals, which increases 

the proportion of time that they can potentially mask animal signals. Survey protocols and 

underwater noise mitigation procedures (Chapter 2.3.2), particularly shutdowns that are designed to 

reduce the potential for injury (PTS), may also decrease the potential risk for any marine mammal to 

experience auditory masking because the source would not operate when animals are close. In 

addition, area closures implemented in some alternatives would reduce the potential for auditory 

masking in selected areas.

Stress and Behavioral Responses

Stress and behavioral changes are the result of marine mammals responding to extreme or 

excessive disturbances in their environment, either of natural or anthropogenic origin. Stress 

responses typically are physiological changes in a marine mammal’s blood chemistry while 

behavioral responses involve changes in a marine mammal’s normal actions.

Stress is a change in the body’s equilibrium in response to an extreme environmental or 

physiological disruption. Marine mammals respond to environmental stress by releasing 

biochemicals into their blood streams. Thus, stress responses can be measured by changes in an 

animal’s blood chemistry. Stress responses in marine mammals are immediate, acute, and 

characterized by the release of the neurohormones such as norepinephrine, epinephrine, and 

dopamine (U.S. Dept. of the Navy, Office of Naval Research, 2009). The NRC (2003a) discussed 

acoustically induced stress in marine mammals, stating that one-time exposures to sound are less 

likely to have population-level effects than sounds that animals are exposed to repeatedly over 
Gulf of Mexico G&G Activities Programmatic EIS 4-37

extended periods of time. Various researchers have summarized the available evidence regarding 

stress-induced events (e.g., Romano et al., 2004; Cowan and Curry, 2008; Mashburn and Atkinson, 

2008; Eskesen et al., 2009). Romano et al. (2004) exposed a beluga whale to varying levels of an 

impulsive signal produced by a water gun and measured the levels of three stress-related blood 

hormones (i.e., norepinephrine, epinephrine and dopamine) after control, low-level sound (171 to 

181 dB SEL), and high-level sound (184 to 187 dB SEL) exposure; no significant differences in the 

hormone blood concentrations were found between the control and low-level sound exposure, but 

elevated levels of all three hormones were produced in response to high-level sound exposure. 

Furthermore, regression analysis demonstrated a linear trend for increased hormone level with 

sound level, and Romano et al. (2004) noted that no quantitative approach to estimating changes in 

mortality or fecundity due to stress has been identified but that qualitative effects may include 

increased susceptibility to disease and early termination of pregnancy. Rolland et al. (2012) showed 

that a 6-dB decrease in the ambient underwater noise level, including a significant reduction below 

150 Hz, was associated with decreased baseline levels of stress-related hormone metabolites in 

whales. This reduction in ambient noise levels associated with shipping was the first evidence that 

exposure to low-frequency noise from shipping may be associated with chronic stress in whales 

(Rolland et al., 2012).

Disturbances can also cause subtle to extreme changes in normal behavior, with some 

behavioral responses resulting in biologically significant consequences. Behavioral responses, 

including startle, avoidance (swim speed and direction changes), displacement, diving, and

vocalization alterations, have been observed in mysticetes, odontocetes, and pinnipeds, and in 

some cases, these have occurred at ranges of tens to hundreds of kilometers from the sound source 

(Gordon et al., 2004; Tyack, 2008; Miller et al., 2014). However, behavioral observations are 

variable, some findings contradictory, and the biological significance of the effects has not been 

measured (Gordon et al., 2004). Behavioral reactions of marine mammals to sound are difficult to 

predict because reactions depend on numerous factors, including the species being evaluated; the 

animal’s state of maturity, prior experience and exposure to anthropogenic sounds, current activity 

patterns, and reproductive state; time of day; and weather state (Wartzok et al., 2004), as well as the 

potential for individual differences within species (Castellote et al., 2014). If a marine mammal 

reacts to an underwater sound by changing its behavior or moving to avoid a sound source, the 

impacts of that change may not be important to the individual, stock, or species as a whole. 

However, if a sound source displaces marine mammals from an important feeding or breeding area, 

impacts on individuals and the population could be important.

Assessing the severity of marine mammal behavioral effects associated with anthropogenic 

sound exposure presents unique challenges associated with the inherent complexity of behavioral 

responses and the contextual factors affecting them, both within and between individuals and 

species. The severity of responses can vary depending on characteristics of the sound source (e.g., 

moving or stationary, number and spatial distribution of sound source[s], similarity to predator 

sounds, and other relevant factors) (Richardson et al., 1995; NRC, 2005; Southall et al., 2007; 

Bejder et al., 2009; Barber et al., 2010; Ellison et al., 2011).
4-38 Description of the Affected Resources and Impact Analysis

Many examples have been reported of individuals of the same species exposed to the same 

sound reacting differently (Nowacek et al., 2004), as well as different species reacting differently to 

the same sounds (Bain and Williams, 2006). Odontocetes, for instance, appear to exhibit a greater 

variety of reactions to man-made underwater noise than do mysticetes. Odontocete reactions can 

vary from approaching vessels (e.g., bow riding) to strong avoidance. Richardson et al. (1995) 

noted that most small- and medium-sized odontocetes exposed to prolonged or repeated 

underwater sounds are unlikely to be displaced unless the overall received level is at least 

140 dB re 1 μPa.

Research on the effects resulting from exposure to seismic survey noise on marine 

mammals is ongoing. Bain and Williams (2006) examined the effects of large airgun arrays 

(4,821 to 6,713 in3

) on six species of marine mammals (i.e., California sea lions, Steller sea lions, 

harbor seals, Dall’s porpoises, harbor porpoises, and gray whales) offshore British Columbia, 

Canada and Washington, U.S. at distances of 1 km to >70 km (0.6 to 43.5 mi). Visual and acoustic 

observations were made as part of a monitoring program conducted in conjunction with the USGS 

survey. The behavior is reported for those observations where the received sound level was 

measured. The maximum theoretical source level generated by this large airgun array was 

calculated to be on the order of 260 dB re 1 μPa at 1 m (Bain and Williams, 2006). Received noise 

levels near the observed marine mammals were measured and, although airguns concentrate 

energy at low frequencies, the airguns produced sound above ambient levels at all frequencies up to 

100 kHz, providing a mechanism to affect marine mammals with strong high-frequency hearing (Bain 

and Williams, 2006). All of the observed marine mammal species moved away from the airguns, but 

each species was observed in waters ensonified at varied received levels; the Dall’s porpoise was 

observed in waters ensonified at the highest exposure level of 181 dB moving at right angles away 

from the airgun source, while harbor porpoises were observed in waters with no higher exposure 

level than 155 dB (Bain and Williams, 2006). Observations of cetaceans during seismic airgun 

surveys in United Kingdom waters demonstrated that small odontocetes showed the strongest 

lateral spatial avoidance, mysticetes and killer whales showed more localized spatial avoidance, 

long-finned pilot whales only showed a change in orientation, and sperm whales did not show any 

significant avoidance response (Stone and Tasker, 2006). For impulsive sounds, there is evidence 

that the behavioral state of mysticetes, combined with their proximity to airgun sounds, affects how 

the whales react to the sounds (McCauley et al., 1998; Gordon et al., 2004). Several species of 

mysticetes showed avoidance behavior to sounds from seismic surveys (Richardson et al., 1995), 

including bowhead whales avoiding distant seismic airguns at received levels of 120 to 130 dB re 

1 μPa SPLrms during fall migration (Richardson et al., 1999).

Acoustic reactions of cetaceans to airgun activity may include increased and/or reduced 

vocalization rates (Goold, 1996; Blackwell et al., 2015), no vocal changes (Madsen et al., 2002), or 

cessation of singing (McDonald et al., 1995). Other short-term vocal adjustments observed across 

species exposed to elevated ambient noise levels include shifting call frequency, increasing call 

amplitude or duration, and ceasing to call (Nowacek et al., 2007). Traveling blue and fin whales 

exposed to seismic noise from airguns stopped emitting repeated songs (McDonald et al., 1995; 

Clark and Gagnon, 2004). By contrast, Di Iorio and Clark (2010) found that blue whales responded 
Gulf of Mexico G&G Activities Programmatic EIS 4-39

to seismic sparker operations by increasing their call production, likely to increase the probability that 

other blue whales would hear their calls in a higher ambient noise environment. As Di Iorio and 

Clark (2010) suggested, later supported by Ellison et al. (2012), the exposure context of the received 

seismic sparker sound strongly influenced the probability and type of behavioral response in the blue 

whales. Di Iorio and Clark (2010) suggested that it was advantageous for the blue whales to expend 

energy by increasing the rate of their vocalizations so that communication with nearby blue whales 

would not be lost. There were insufficient data to determine the relevance of the observed vocal 

adjustment to an individual whale’s well being. However, observations by Di Iorio and Clark (2009) 

were conducted in an important feeding area where blue whales acquire energy and where this 

wide-roaming, highly dispersed population congregates to engage in social interactions. Acoustic 

and behavioral changes by fin whales in response to shipping and airgun noise found that the 

acoustic features of fin whale 20-Hz song notes were affected in high-noise conditions. In these 

conditions, note that duration was shortened, bandwidth decreased, center frequency decreased, 

and peak frequency decreased. Similar results were obtained in 20-Hz song notes recorded during 

a 10-day seismic survey. This study provides evidence that male fin whales from two different 

subpopulations modify song characteristics under increased background noise conditions and that, 

under seismic airgun activity conditions, they leave an area for an extended period (Castellote et al., 

2012). Similar results were recorded for vocalizing humpback whales off Angola during seismic 

surveys (Cerchio et al., 2014). Other studies on humpback whales reported their avoidance of 

seismic surveys (McCauley et al., 2000a). Resting females diverted to remain 7 to 12 km (4 to 7 mi) 

away, although males occasionally were attracted to the sounds.

Few dedicated studies of the behavioral responses of GOM marine mammals have been 

conducted, especially to seismic activities. Mate et al. (1994) noted that sperm whales were 

displaced in the northern GOM off the Louisiana coast following seismic surveys in the area. Sperm 

whales were sighted at a rate of 0.092 whales per kilometer prior to the seismic survey, but the 

sperm whale abundance declined significantly within the seismic survey area after the survey began, 

to where none were detected for 5 consecutive days; only one group of four sperm whales was 

observed within 61 km (38 mi) of the seismic survey area (Mate et al., 1994). Sperm whale sightings 

during seismic surveys in the GOM showed a significant difference in the closest point of approach 

distance between times of airgun silence and full power, with greater distances from the source 

displayed during full power (Barkaszi et al., 2012). Miller et al. (2009) reported the lack of a 

behavioral response in eight tagged sperm whales in the GOM that were exposed to received levels 

of 111-147 dB rms from a large airgun array. The whales were at ranges from 1 to 13 km (0.6 to 

8.1 mi) from the vessel. The sperm whales did not change their resting or foraging behavior when 

the airguns started up or approached the whales, indicating that sperm whales in the GOM did not, 

in this instance, exhibit avoidance behavioral responses to airguns (Miller et al., 2009). However, 

Miller et al. (2009) suggested that, while the surface observations were indicative of no behavioral 

disruption, the lower pitch and buzz rates the tags recorded while the sperm whales were exposed to 

the airgun noise may have been indicative of impacts to feeding rates. The most closely 

approached of the eight tagged whales maintained a prolonged resting period while the airguns were 

operating, but they immediately resumed foraging dives when the airguns were turned off.
4-40 Description of the Affected Resources and Impact Analysis

There is significant species-specific contextual variability in the behavioral responses of 

marine mammals to noise exposure. Furthermore, variability can occur within a species at the 

individual level where hearing loss or prior experience with a certain sound type can influence 

whether or not an individual reacts (Castellote et al., 2014). There also is a broad spectrum of 

behavioral responses, each of which has varying importance to the individual. Recognizing these 

issues, Southall et al. (2007) concluded (1) that there are many more published accounts of 

behavioral responses to noise by marine mammals than of direct auditory or physiological effects; 

(2) available data on behavioral responses do not converge on specific exposure conditions resulting 

in particular reactions, nor do they point to a common behavioral mechanism; (3) study data 

obtained with substantial controls, precision, and standardized metrics indicate high variance in 

behavioral responses and in exposure conditions required to elicit a given response; and 

(4) distinguishing a significant behavioral response from an insignificant momentary alteration in 

behavior is difficult. Wartzok et al. (2005) suggested that a major scientific effort is required to

enable the prediction of long-term behavioral and physiological effects in marine mammal 

populations from anthropogenic noise. Sound sources used during geophysical survey activities can 

produce stress, disturbance, and behavioral responses in marine mammals if they are present within 

the range of the operational airgun array. Survey protocols and underwater noise mitigation 

procedures (Chapter 2), designed to prevent injury (PTS), may decrease the duration any marine 

mammal would be within the exclusion zone of an operating sound source, thereby reducing the 

level of behavioral disturbance and injury within defined zones near the sound source. Outside of 

the exclusion zone, behavioral responses may occur. As seismic airgun signals commonly occur in 

the GOM, it is possible that behavioral reactions to them may be reduced with time and repeated 

exposure, although there are no published data from the GOM to support this. The mechanism for 

such reduction could either be habituation or tolerance (Bejder et al., 2006). Habituation is “the 

relative persistent waning of a response as a result of repeated stimulation, which is not followed by 

any kind of reinforcement” (Thorpe, 1963). Thus, habituation occurs in response to a neutral 

stimulus. Tolerance is “the intensity of disturbance that an individual tolerates without responding” 

(Nisbet, 2000). If reduced behavioral response is observed, discerning if it represents habituation or 

tolerance is difficult without detailed study.

Reduction of Prey Availability

Sound may indirectly affect marine mammals through its effects on the abundance, behavior, 

or distribution of prey species such as crustaceans, cephalopods, and fish. These species are 

important prey for marine mammals and many are important commercial and recreational fishery 

species in the GOM. To better understand the effects of anthropogenic sound on invertebrates, 

fishes, and fisheries, about which less research has been conducted, BOEM funded a three-phase 

program consisting of a literature synthesis, workshop to discuss the state of knowledge, and a gap 

analysis. The literature compilation was completed prior to the 2012 workshop, with a 

summarization of the workshop and gap analysis published in December 2012, and focused on the 

U.S. Atlantic and Arctic OCS areas (Normandeau Associates, Inc., 2012).
Gulf of Mexico G&G Activities Programmatic EIS 4-41

There are limited data on hearing mechanisms and the potential effects of sound on marine 

mammal prey (i.e., crustaceans, cephalopods, and fish). These species have been increasingly 

researched and the results published as concern has grown. Invertebrates appear to be able to 

detect sounds (Pumphrey, 1950; Frings and Frings, 1967) and are most sensitive to low-frequency 

sounds (Packard et al., 1990; Budelmann and Williamson, 1994; Lovell et al., 2005; Mooney et al., 

2010). Of invertebrates, cephalopods are the most researched group to date.

Cephalopods (i.e., octopus and squid) and decapods (i.e., lobsters, shrimps, and crabs) are 

capable of sensing low-frequency sound. Packard et al. (1990) showed that three species of 

cephalopods were sensitive to particle motion, not sound pressure, with the lowest thresholds 

reported as 0.002 to 0.003 m/s2 at 1 to 2 Hz. Mooney et al. (2010) demonstrated that squid 

statocysts (sensory organs found in a wide range of aquatic invertebrates) act as an accelerometer 

through which particle motion of the sound field can be detected; Mooney et al. (2010) measured 

acceleration thresholds of -26 dB re 1 m/s2 between 100 and 300 Hz and a pressure threshold of 

110 dB re 1 μPa at 200 Hz. Lovell et al. (2005) found a similar sensitivity for prawn (Palaemon 

serratus), 106 dB re 1 μPa at 100 Hz, noting that this was the lowest frequency at which they tested 

and that the prawns might be more sensitive at lower frequencies. Hearing thresholds at higher 

frequencies have been reported, e.g., 134 dB re 1 μPa and 139 dB re 1 μPa at 1,000 Hz for the oval 

squid (Sepioteuthis lessoniana) and the common octopus (Octopus vulgaris), respectively (Hu et al., 

2009). McCauley et al. (2000a) reported that exposure of caged squid to seismic airguns showed 

behavioral response including inking. Wilson et al. (2007) exposed two groups of squid (Loligo 

pealeii) in a tank to 199- to 226-dB killer whale echolocation clicks, which resulted in no apparent 

behavioral effects or any acoustic debilitation. However, both the McCauley et al. (2000a) and 

Wilson et al. (2007) experiments used caged squid, so it is unclear how unconfined animals would 

react. André et al. (2011) exposed four cephalopod species (i.e., Loligo vulgaris, Sepia officinalis, 

Octopus vulgaris, and Ilex coindetii) to 2 hours of continuous sound from 50 to 400 Hz at received 

levels of 157 ± 5 dB re 1 μPa and reported lesions occurring on the statocyst’s sensory hair cells of 

the exposed animals that increased in severity with time, suggesting that cephalopods are 

particularly sensitive to low-frequency sound. Similar to André et al. (2011), Sóle et al. (2013a) 

conducted a low-frequency (50 to 400 Hz) controlled exposure experiment on two deep-diving squid 

species (i.e., Illex coindeti, and Loligo vulgaris), which resulted in lesions on the statolyst epithelia. 

Sóle et al. (2013a) described their findings as “morphological and ultrastructural evidence of a 

massive acoustic trauma induced by...low frequency sound exposure.” In experiments conducted 

by Samson et al. (2014), cuttlefish exhibited escape responses (inking and jetting) when exposed to 

sound frequencies between 80 and 300 Hz with sound levels above 140 dB re 1 μPa rms and 

0.01 m/s2

; the cuttlefish habituated to repeated 200-Hz sounds. The response intensity of the 

cuttlefish depended on the amplitude and frequency of the sound stimulus, suggesting that cuttlefish 

possess loudness perception with a maximum sensitivity of approximately 150 Hz (Samson et al., 

2014).

Several species of aquatic decapod crustaceans produce sounds; Popper et al. (2001) 

concluded that many are able to detect substratum vibrations at sensitivities sufficient to tell of the 

proximity of mates, competitors, or predators. Popper et al. (2003) reviewed behavioral, 
4-42 Description of the Affected Resources and Impact Analysis

physiological, anatomical, and ecological aspects of sound and vibration detection by decapod 

crustaceans and noted that many decapods also have an array of hair-like receptors within and upon 

the body surface that potentially respond to water- or substrate-borne displacements, as well as 

proprioceptive organs that could serve secondarily to perceive vibrations. However, the acoustic 

sensory system of decapod crustaceans remains poorly studied (Popper et al., 2003). Lovell et al. 

(2005) and Lovell (2006) reported that the prawn Palaemon serratus is capable of detecting lowfrequency sounds (100 to 3,000 Hz); however, there is no behavioral evidence of prawns responding 

to sounds to date.

Research on the hearing sensitivity of fishes, their responses to sound, and potential impacts 

of sound on fish and fisheries are somewhat limited due to the difficulty in experimentally quantifying 

sound fields, as fish are capable of sensing both sound pressure and particle motion. However, 

particle motion and SPL measurements typically have not been measured together, making it 

difficult to fully understand the hearing capabilities of fish. The workshop report (Normandeau 

Associates, Inc., 2012) contains a summary of research on fish hearing and physiology and presents 

audiograms for the fish that have been measured in the appropriate acoustic conditions.

It is likely that all species of fish can hear and that many fish species produce and use sound 

for communication. Hearing has been measured in <100 of the >32,000 species of fish, with the 

majority of freshwater fish species having been studied, although several elasmobranchs (i.e., 

sharks and rays) have been researched as well. Very little hearing research has been conducted on 

the >1,100 species of fish that occur in the GOM. Fish appear to be most sensitive to low-frequency 

sounds below 1,000 Hz. For the majority of fish for which data are available, the region of best 

hearing ranges from 100 to 200 Hz up to 800 Hz, with most species able to detect sounds to below 

100 Hz and some species even capable of detecting infrasound, i.e., sounds below 30 Hz (Karlsen, 

1992a and 1992b; Knudsen et al., 1992; Ross et al., 1995). Flatfish (Pleuronectiformes), of which 

numerous species occur in the GOM, have relatively narrow-band hearing, from 30 to 300 Hz 

(Casper and Mann, 2009). The GOM species such as the bay anchovy (Anchoa mitchilli) can detect 

sounds at frequencies of approximately 100 to 1,000 Hz (Mann et al., 2001). Popper (2005) 

reported that studies measuring responses of the ear using physiological methods suggest that a 

species of sturgeon likely is capable of detecting sounds from below 100 Hz to approximately 1 kHz, 

suggesting that sturgeon should be able to localize or determine the direction of origin of sound. 

Meyer and Popper (2002) recorded auditory-evoked potentials of varying frequencies and intensities 

for lake sturgeon (Acipenser fulvescens) and found that lake sturgeon can detect pure tones from 

100 to 2,000 Hz, with best hearing sensitivity from 100 to 400 Hz. Lovell et al. (2005), using a 

combination of morphological and physiological techniques, determined that lake sturgeon were 

responsive to sounds ranging in frequency from 100 to 500 Hz, with the lowest hearing thresholds 

acquired between 200 and 300 Hz; lake sturgeon were not sensitive to sound pressure. Data on 

shark hearing are limited, but elasmobranch species generally are able to detect low-frequency 

sounds (approximately 20 to 1,000 Hz), with similar thresholds for all measured species above 

100 Hz (Casper and Mann, 2009), and sound appears to be sensed solely through particle motion 

(Myrberg, 2001). Nelson and Gruber (1963) reported that free-ranging sharks, including 

hammerheads, were attracted to low-frequency sounds (<60 Hz) that were rapidly and irregularly 
Gulf of Mexico G&G Activities Programmatic EIS 4-43

pulsed, as these sounds likely represented the vibrations caused by struggling prey. Some actively 

swimming, fish-eating sharks such as lemon sharks (Negaprion brevirostris) and Atlantic sharpnose 

sharks (Rhizoprionodon terraenovae) have most hearing below 100 Hz, suggesting that hearing may 

be more important than other senses in the detection of prey for some species (Casper et al., 2012). 

Very sparse data on hearing in hammerhead sharks are available; Olla (1962) observed that 

hammerhead sharks were able to detect sounds below 750 Hz, with best sensitivity from 250 to 

275 Hz.

Several studies have demonstrated that anthropogenic sounds, specifically seismic surveys, 

might affect the behavior of some fish species, which could ultimately result in reduced foraging 

opportunities for fish-eating cetaceans. For example, field studies by Engås et al. (1996) reported a 

significant decline in commercial fishing catch rate of haddock (Melanogrammus aeglefinus) and 

Atlantic cod (Gadus morhua) during a 3-day seismic airgun array (5,000 in3 total volume) survey and 

for up to 5 days after seismic airguns stopped; after that time, the catch rate returned to normal. 

Slotte et al. (2004) found that pelagic species, including blue whiting (Micromesistius poutassou) and 

Norwegian spring spawning herring (Clupea harengus), descended to greater depths after exposure 

to airgun sounds (array volume = 3,090 in3

); the abundance of fish 30 to 50 km (19 to 31 mi) away 

from the area of airgun ensonification increased, suggesting that fish would not enter the zone of 

seismic activity. Other studies found minor responses during or following seismic surveys, using a 

28-gun array, such as a small decline in the abundance of lesser sand eels (Ammodytes marinus), 

with the abundance quickly returning to pre-seismic levels (Hassel et al., 2004), or no response in 

the behavior of the fish (Wardle et al., 2001). Wardle et al. (2001) used underwater video and an 

acoustic tracking system to examine the behavior of reef fishes in response to emissions from a 

single seismic airgun; startle responses and some changes in the movement patterns of fish were 

observed following exposure. Startle responses have been observed in several fish species 

exposed to airgun sounds (Pearson et al., 1992; Santulli et al., 1999; Hassel et al., 2004). The 

Santulli et al. (1999) study used a 16-gun array with a total volume of approximately 2,500 in3

, while 

the Pearson et al. (1992) study used a single 100-in3 airgun.

McCauley et al. (2003) reported some damage to sensory hair cells in the ears of pink 

snapper (Pagrus auratus) after exposure to sounds from a 20-in3 airgun. In studies of seismic 

exposure, fish were exposed to 5 or 20 shots from an 8-gun seismic array (total volume = 730 in3

), 

with a received sound level of >195 dB re 1 μPa (peak-to-peak) (Popper et al., 2005; Song et al., 

2008). After exposure, some temporary hearing loss occurred in only two species of fish, but no 

evidence of tissue damage to the swim bladder, other non-auditory tissues, or ear tissue was found 

(Song et al., 2008). Popper et al. (2005) suggested that the differences in tissue damage between 

their study and that of McCauley et al. (2003) may have been due to the very different acoustic 

environments of the studies. No mortality occurred to fish in any of these seismic studies. In an 

evaluation of the behavior of free-swimming fishes to noise from an 8-gun seismic array (total 

volume = 730 in3

) in the Mackenzie River in Northwest Territories, Canada, fishes did not exhibit a 

noticeable response even when SELs (single discharge) were on the order of 175 dB re 1 μPa2

•s 

and SPL0-peak were >200 dB re 1 μPa (Jorgenson and Gyselman, 2009; Cott et al., 2012).
4-44 Description of the Affected Resources and Impact Analysis

Acoustic Exposure Criteria

Since the mid-1990s, the USDOC, NMFS (2013b) has specified that cetaceans exposed to 

pulsed sounds with received SPLs exceeding 180 dB re 1 μPa (rms) would be considered as 

potentially injured under the MMPA and experience Level A harassment. The NMFS also considers 

that marine mammals exposed to pulsed sound levels >160 dB re 1 μPa (rms) are subject to MMPA 

Level B harassment (Table 4.2-5). Although NMFS is in the process of updating these criteria 

(USDOC, NMFS, 2013b and 2015b; discussed further below), the new criteria have not yet been 

finalized and published, so the existing acoustic threshold criteria were utilized as one set of criteria 

in the impact analyses presented herein.

Since development and application of the 160 dB and 180 dB re 1 μPa (rms) criteria, 

additional scientific research has been completed that further clarifies the best methodology for 

estimating potential impacts from acoustic exposure. To capture the best available data on acoustic 

exposure criteria, exposure to acoustic energy for MMPA Level B harassment is also considered 

using the Wood et al. (2012) methodology; MMPA Level A is also considered using the Southall 

et al. (2007) methodology. More details on the acoustic exposure criteria are provided in 

Appendix D.

Both the Wood et al. and Southall et al. methods include frequency weighting to account for 

animal hearing sensitivities. Sound is less likely to injure or disturb animals if it occurs at 

frequencies to which the animal is less sensitive. Based on a review of marine mammal hearing and 

on physiological and behavioral responses to anthropogenic sound, three functional hearing groups 

of cetaceans have been defined (Southall et al., 2007; Finneran and Jenkins, 2012):

• low-frequency cetaceans (mysticetes);

• mid-frequency cetaceans (some odontocetes); and 

• high-frequency cetaceans (some odontocetes).

Of the marine mammal species occurring in the GOM, the Bryde’s whale is the only lowfrequency cetacean and Kogia species (i.e., the dwarf sperm whale and pygmy sperm whale) are 

the only high-frequency cetaceans. Nineteen additional mid-frequency cetacean species occur in 

the GOM. Southall et al. (2007) defined Type I M-weighting functions for each functional hearing 

group, which is used in the MMPA Level B criteria of Wood et al. (2012). The Southall et al. (2007) 

Type I M-weighting was updated for MMPA Level A impacts for low-, mid-, and high-frequency 

cetaceans by Finneran and Jenkins (2012), termed Type II weighting. Because limited data exist for 

low-frequency cetaceans, the Type I M-weighting is used here with the Southall et al. (2007) Level A 

criteria, whereas the Type II weighting, updated with the best available research conducted since 

Southall et al. (2007) was published, is used for mid- and high-frequency cetaceans (Finneran and 

Jenkins, 2012).
Gulf of Mexico G&G Activities Programmatic EIS 4-45

The Wood et al. (2012) Level B criteria use a graded step function to acknowledge that most 

marine mammals exhibit varying responses between SPLrms of 140 dB and 180 dB re 1 μPa. For 

pulsed sounds, a graded probability of response with 10 percent response likelihood at an rms of 

140 dB re 1 μPa, 50 percent at an SPLrms of 160 dB re 1 μPa, and 90 percent at an SPLrms of 180 dB 

1 μPa was used for all species except beaked whales. Sensitive species, such as beaked whales, 

exhibit the likelihood of a 50 percent response at an SPLrms of 120 dB re 1 μPa and a 90 percent 

response at an SPLrms of 140 dB re 1 μPa (Wood et al., 2012; Appendix D, Table 6).

The Southall et al. (2007) Level A criteria acknowledge that there two mechanisms for an 

animal to experience Level A exposures, fatiguing of the sensory system measured with a 

cumulative sound exposure level (SEL) threshold and tissue damage measured with a peak SPL

threshold. The SEL criteria are frequency weighted (Type I M-weighting for Bryde’s whale; Type II 

weighting for all other species) and are 192, 187, and 161 dB re 1 μPa2

·second, respectively, for 

low-, mid-, and high-frequency cetaceans. The peak SPL criteria are not weighted and are 

230 dBpeak re 1 μPa for low- and mid-frequency cetaceans and 200 dBpeak re 1 μPa for highfrequency cetaceans (Southall et al., 2007; Appendix D, Table 5).

Therefore, there are two criteria used for Level B harassment: the traditional NMFS criteria 

(160 dB rms) and the step function of Wood et al. (2012). There are two criteria used for Level A 

harassment: the traditional NMFS criteria (180 dB rms) and the SEL and SPLpeak criteria of Southall 

et al. (2007).

As previously noted, updated criteria are under development by NMFS based on the 

advances in the understanding of the impacts of noise on marine mammals. A draft version was 

circulated for public comment in 2013 (USDOC, NMFS, 2013b), with a second draft version 

circulated in 2015 (USDOC, NMFS, 2015b). The current draft version (USDOC, NMFS, 2015b) uses 

dual criteria (SEL and peak SPL) similar to Southall et al. (2007) with refinements based on recent 

U.S. Navy research (Finneran, 2015, provided as Appendix A of the draft guidance). BOEM is 

aware of the ongoing reconsideration, which is a long and thoughtful process in which BOEM is 

engaged. Throughout the development of this Programmatic EIS, BOEM has worked closely with 

NOAA/NMFS on which acoustic criteria and numerical methods to include in this impact analysis. 

Based on the best science available as well as other considerations, such as the policies, the 

delivery and finalization dates for new acoustic criteria and calculation techniques, etc., this 

Programmatic EIS utilizes the best available approach to analyze the potential acoustic impacts from 

the proposed action. BOEM will implement any requirements or conditions of approval set out by 

NMFS in site-specific reviews and permits once the new acoustic guidance is finalized.

Marine Mammal Estimates of Potentially Occurring Exposures

A workshop was held in January 2014 where experts in sound propagation and exposure 

modeling came together to provide NMFS and BOEM with information to assess available methods 

for modeling marine mammal exposures at given levels of sound for seismic activities of the oil and 

gas industry in the GOM. During this workshop, participants discussed sound propagation modeling, 
4-46 Description of the Affected Resources and Impact Analysis

including approaches to modeling sound fields from airgun arrays and other active acoustic sources, 

and the integration of modeled sound fields with biological data to estimate marine mammal 

exposures. BOEM and NMFS used information from the workshop to determine the best exposure 

modeling approach to support MMPA and ESA regulatory requirements for G&G survey activities in 

the GOM.

It is important to note that BOEM and NMFS do not equate every exposure to sound as 

a “take” as defined by the Section 101(A)(5)(A-D) of the MMPA. Therefore, exposure estimates 

used in this Programmatic EIS are not necessarily the same as a “take” of an animal.. Where 

there is an overlap between noise sources and the frequencies of sound used by marine life, there 

may be concerns related to how such sound may interfere with important biological functions. 

Noise, either natural or anthropogenic, can adversely affect marine life in various ways, inducing 

alteration of behavior, reduction of communication ranges or orientation capability, temporary or 

permanent damage to the auditory or other systems; and/or, in extreme cases, habitat avoidance or 

even death (e.g., Richardson et al., 1995; NRC, 2003a and 2005; Nowacek et al., 2007; Southall 

et al., 2007). BOEM expects that the majority of exposures are likely to result in only minor 

behavioral impacts such as short-term disruption of behavioral patterns, abandonment of activities, 

and/or temporary displacement from discrete areas rather than long-term physiological effects such 

as permanent hearing loss. Noise impacts may also be additive or synergistic to those of other 

human stressors. While determining the biological significance of noise exposure impacts remains 

challenging (NRC, 2005), significant strides have been made in quantifying the effects of noise on 

marine mammals (USDOI, BOEM, 2014b). Additionally, accurate predictive modeling of potential 

acoustic impacts requires knowledge of (1) the specific source(s) that would be used at each site of 

survey operations, (2) the exact environmental acoustic conditions present at each site, (3) the 

timing and type of each survey, and (4) the marine animals present at each site.

As such, the exposure estimates presented in this Programmatic EIS were computed 

from modeled sound levels received by simulated (modeled) animals for several types of 

geophysical surveying. Animals and sources are constantly moving relative to the environment 

and each other. The sound fields generated by the sources are shaped by various physical 

parameters, and the sound levels ultimately received by an animal are a complex function of 

location and time. The basic modeling approach was to use acoustic models to compute the 3D 

sound fields and their variations in time. Simulated animals (animats) were modeled moving 

through these fields to sample the sound levels in a manner similar to how real animals would 

experience these sounds. This allows a history of exposures to be built of the received sound 

levels of all animats. The number of animals exposed to levels exceeding effects threshold 

criteria were determined and then adjusted by the number of animals expected in the area 

based on density information (which may not be an accurate representation of the marine 

mammal population). This creates an estimate of the potential number of animals exposed to 

the sounds. This estimate does not reflect an actual expectation that marine mammals will be 

injured or disturbed; it is an overly conservative estimate. Biological significance to marine 

mammals is left to interpretation by the SMEs. Using the model estimates most often requires 
Gulf of Mexico G&G Activities Programmatic EIS 4-47

accepting a worst-case scenario, which ultimately equates in some form the numbers of 

exposures to the number of “takes” under the MMPA.

The existing modeling largely does not account for uncertainty in the data inputs and 

also selects highly conservative data inputs. This bias often produces unrealistically high 

exposure numbers and “takes” that exponentially increase uncertainty throughout each step of 

the modeling. The modeling does not incorporate mitigation or risk reduction measures 

designed to limit exposure. The modeling is an overestimate and should be viewed with that 

understanding.

The acoustic modeling was divided into two phases. In Phase I, a WAZ survey was 

simulated at two locations within Mississippi Canyon. This was done based on the recommendation 

from the workshop that the modeling needs to represent real-world scenarios in that location (in this 

case, WAZ surveys occur frequently in Mississippi Canyon) and also to establish the basic 

methodological approach, and the results were used to evaluate scenarios that may influence 

exposure estimates. Results from the test scenarios were then used to guide the main modeling 

effort of Phase II. In Phase II, the AOI was divided into seven modeling zones, and each survey 

type was simulated in each zone to estimate the potential effects. Exposure statistics were 

determined by sampling numerically estimated acoustic fields for each operation using an animat 

model (Marine Mammal Movement and Behavior [3MB] model; Houser, 2006). Exposure estimates 

were determined for 24-hour periods within 7-day simulations in order to attain representative 

estimates of exposures associated with each operation. Using survey level-of-effort projections 

provided by BOEM, the 24-hour exposure estimates were used to calculate annual exposure 

estimates for each marine mammal species likely to be affected by airgun and selected HRG survey 

operations in the entire GOM for a 10-year period. The operations for which exposure estimates 

were calculated included the following:

• 2D surveys (single source vessel with 8,000-in3 airgun array); 

• 3D NAZ surveys (two source vessels, each with 8,000-in3 airgun array); 

• 3D WAZ surveys (four source vessels, each with 8,000-in3 airgun array);

• coil surveys (four source vessels, each with 8,000-in3 airgun array);

• 90-in3 airgun;

• boomers; and

• HRG surveys using side-scan sonar, subbottom profilers, and MBESs.

The results from each zone were summed to provide Gulfwide estimates of the effects on 

each marine mammal species for each survey type for each year, as well as 10-year totals for the 

activities. Despite uncertainty and variability in future actions (e.g., survey size, survey techniques, 

and timing and location of a survey predicted over the 10-year period), the employment of source 

and propagation models required numerous specific details during their calculations. Not all survey 
4-48 Description of the Affected Resources and Impact Analysis

configurations can be modeled, and the exact numbers of surveys that will occur during the 10-year 

period are not known. Therefore, this modeling effort represents BOEM’s predictions and industry 

input on reasonably foreseeable levels of activity, using the best information of current activity levels 

and trends. Calculations of acoustic exposures to marine mammals from airgun and 

electromechanical sound sources associated with the proposed action scenario are presented in 

Appendix D. The issue of realistic and reasonable parameter selection is stated and expanded 

upon in the modeling report (Appendix D). The modeled exposure estimates may not represent the 

actual takes that will occur during geophysical surveys in the GOM for a variety of reasons. The 

best estimate of exposures is based on conservative modeling parameters, which are further 

discussed in the Test Case Scenarios of Appendix D. Further, exposures do not necessarily qualify 

as take, as that term is defined under the MMPA. Despite uncertainty and variability in future 

actions, the use of models require numerous specific details to be identified and used during their 

calculations. For example, representative sound sources are modeled at highest sound levels and 

always at maximum power and operation; sound levels received by an animal are calculated at 

highest levels; and numbers generated by models do not include the effect of all mitigations in 

reducing the potential for actual take. Additional assumptions that add to the conservativeness of 

the models are discussed here and are further discussed in the JASCO modeling report 

(Appendix D).

In order to better explain how these results differ from actual in situ impacts, several of the 

most prominent conservative assumptions from Appendix D are listed here. Details of each 

assumption are provided in Appendix D. 

• Acoustic Source Specifications: There is a large variation in the size, 

configuration, and source level of the airgun arrays employed during surveys. 

Details of acoustic source modeling are provided in Appendix D, Section 5.1. 

Additionally, it was assumed that the modeled array was always at maximum 

power and that all airguns were fully operational for completed survey scenarios.

• Acoustic Source Modeling: For simplicity, the acoustic modeling replaces the 

actual predicted airgun array sound field with one produced by a point source 

(i.e., a single larger airgun versus a distributed airgun array) and a beam pattern. 

This is fairly accurate in the far-field (typically 100 to 300 m [328 to 984 ft] from 

the array center and outward) but, within this range (i.e., in the near-field), this 

can greatly overestimate the apparent source level and the subsequent impacts 

calculated. Simply replacing this conservative near-field approximation is 

feasible from a mathematical modeling point of view. However, because it is 

heavily dependent on the actual source parameters, it would be difficult to justify 

it in this Programmatic EIS, and it would greatly enlarge the modeling effort while 

not necessarily remaining conservative. Details of acoustic source modeling are 

provided in Appendix D, Section 5.1. 

• Acoustic Propagation Modeling: Typically, the acoustic parameters used in 

acoustic modeling (including sound velocity profile, surface wind and wave 
Gulf of Mexico G&G Activities Programmatic EIS 4-49

values, and seafloor sediment types/distributions/thicknesses/coefficients) are 

averaged seasonal values over reasonably sampled areas and time periods. For 

example, sea state greatly affects the propagation and it is often over estimated 

for that reason. These averaging processes remove most local variability while 

capturing the general effect of the sound speed on acoustic propagation. In 

some cases, this can underestimate the transmission loss and therefore 

overestimate the received levels at all ranges. Actual in situ propagation typically 

displays much more fading and disruption of the signal, especially for signals 

shorter than 1 second (i.e., airguns).

• Acoustic Modeling of the Multipath: When a signal propagates through the 

ocean, it typically follows many pathways between the source and a receiver. 

For example, one path may be directly between the source and receiver, while 

others may reflect off of the ocean surface or seafloor before arriving at the 

receiver. For most of the models used in acoustic propagation analyses, the 

model assumes that the signals continue until all of the significant paths have 

arrived at the receiver, then the energy from these different pathways is summed 

to derive a final received value. This is a conservative approach for short signals 

such as airgun pulses, and the spreading of a signal (and its energy) generally 

increases as range increases. This is not a simple or easy correction to make as 

it can be heavily dependent on the receiver’s position in range and depth. The 

assumption is that, for very short duration signals, the modeling assumes that 

arrival of the multipath is added together for a total received signal level, but the 

reality is that, for very short duration signals like for airguns, the signal is spread 

out in time and is additive together at one peak pressure. Details of acoustic 

propagation modeling are provided in Appendix D, Section 5.2. 

• Marine Mammal Congregations: Marine mammals, especially dolphins, often 

occur in groups and occasionally in mixed-species aggregations. When this 

occurs, the actual density near that group can be greater than those used in 

these calculations, but the corresponding reduction of density for much of the

surrounding areas has been decreased. Statistically, this averages out for 

multiple model runs that are not accounting for this.

• Mitigation: The inclusion of mitigation in the modeling was discussed during the 

January 2014 modeling workshop and was considered in the modeling project. A 

test case was run to determine the effectiveness of mitigation in the modeling 

(Appendix D) to reduce cumulative exposure levels. Incorporation of mitigation 

measures and mitigation effectiveness into the modeling is discussed in Test 

Scenario 3 (but not incorporated in the Phase II overall modeling effort) of the 

Modeling Report. This is because the effectiveness at reducing marine mammal 

exposure to potentially injurious sound levels with this commonly used approach 

cannot be quantified with confidence at this time. Mitigation effectiveness, as 

measured by the percent reduction in exposure estimates, is predominantly a 
4-50 Description of the Affected Resources and Impact Analysis

function of animal detection probability during a seismic survey. The greater the 

detection probability, the greater the effectiveness of shutdown mitigation, which 

reduces the duration of the exposure. From this test, the inclusion of mitigation 

procedures in the simulations reduced the numbers of exposures based on 

SPLpeak and SPLrms criteria for five out of six species and detection probabilities 

considered, even though an extension in the survey period due to line re-shoot 

was taken into account. The percent reduction in exposures for species with 

relatively high detection probability (e.g., common bottlenose dolphins, shortfinned pilot whales, and sperm whales) was higher than the percentage reduction 

for species with relatively low detection probability (e.g., Cuvier’s beaked whales 

and dwarf sperm whales). Bryde’s whales had no exposures in the test case 

with or without mitigation. The numbers of exposures based on the SEL criteria 

were zero for most species (even without mitigation), except for dwarf sperm 

whales. Considering the results of the test case, however, it was determined that 

the overall modeling should not include mitigation because detection probability 

can vary due to several factors that cannot be forecasted with any certainty. The 

calculations included here do not include any mitigation effects that would reduce 

the potential for exposure. Therefore, the modeled exposure estimates are likely 

to overestimate potential actual takes that will occur during geophysical surveys 

in the GOM. Details of mitigation effectiveness are provided in Appendix D, 

Section 6.5.3. 

The assessment of acoustic exposures to marine mammals within the AOI from various 

active sound sources projected in the scenario (Chapter 4.2.2) was partially based on speciesspecific spatial and temporal distribution and density information, as detailed in Appendix D. These 

numbers represent a conservative best estimate. CetMap density data for each species were 

estimated within seven modeling zones within the AOI during four seasons (Appendix D, 

Figure 110). The species density estimates within each modeling zone were then used to estimate 

potential acoustic exposures to marine mammal species from proposed acoustic survey activities. 

These estimates are provided in Appendix D, Tables 62 through 68. As discussed previously, the 

issue of realistic and reasonable parameter selection is stated and expanded upon in the source and 

exposure estimate modeling report (Appendix D). However, it must be emphasized that each of 

these typical assumptions accumulate throughout the analysis and result in fairly conservative 

exposure estimates.

Lastly, some of the marine mammal exposure estimates provided in this chapter, which are 

referenced from Appendix D, include a decimal; these numbers are expected to be rounded up to 

the next whole number.

4.2.2.1.2 Analysis of Active Acoustic Sound Sources

Active acoustic sound sources associated with proposed G&G activities include airguns and 

electromechanical sources. Airguns are commonly used to characterize the shallow and deep 
Gulf of Mexico G&G Activities Programmatic EIS 4-51

structure of the continental shelf, continental slope, and deepwater ocean environments. Details of 

airguns and seismic survey types that utilize airguns are discussed in Chapter 3 and include oil and 

gas exploration and development surveys (e.g., deep-penetration seismic airgun surveys) and some 

HRG surveys of oil and gas leases). The HRG site surveys are conducted to investigate the shallow 

subsurface for geohazards and soil conditions in a specific location or over a broad area and to 

identify potential benthic biological communities and archaeological resources. The HRG surveys 

use several techniques, including airgun(s) and/or electromechanical sources, such as side-scan 

sonars, shallow- and medium-penetration subbottom profilers, SBESs, and MBESs. For this 

analysis, shallow-penetration airgun seismic surveys used for HRG site surveys are discussed 

separately from electromechanical source (non-airgun) surveys. The HRG surveys and related 

equipment are discussed in Chapter 3. 

Deep-Penetration Seismic Airgun Survey Activities

Level A Estimates of Potentially Occurring Exposures

Deep-penetration seismic airgun seismic surveys include 2D, 3D, and 4D OBS, WAZ, and 

VSP. To estimate the number of exposures that may potentially occur, modeling was conducted for 

2D, 3D NAZ, 3D WAZ, coil, and VSP survey activities during the 10-year time period covered by this

Programmatic EIS. Summaries of the potential exposures to the acoustic criteria outlined above are 

provided below. Appendix D provides more detail regarding the modeling and estimates of 

exposures that would potentially occur.

Annual estimates of exposures that potentially may occur were calculated for proposed 

deep-penetration seismic airgun 2D, 3D NAZ, 3D WAZ, and coil survey activities during the time 

period covered by this Programmatic EIS for each survey type are presented in Appendix D. Total 

decadal, deep-penetration airgun seismic survey Level A estimates of exposures that may 

potentially occur using these metrics for each survey type are presented in Appendix D, Tables 76 

through 79. For review, an overview of the Level A estimates of exposures that may potentially 

occur is provided for each survey type.

Deep-penetration 2D airgun seismic surveys are anticipated to be conducted in the EPA and 

CPA, primarily in continental shelf and slope waters. This type of survey activity is projected to 

occur in six of the 10 years, with decreasing levels of activity expected for two to three of those years 

(Appendix D, Table 75). For the decadal period, Kogia are estimated to have the highest number 

of exposures that may potentially occur, with 695.3 and 54.8 potential exposures for the SPLpeak and 

SEL criteria, respectively (Appendix D, Table 76). At an annual level, the highest numbers of 

potentially occurring Kogia exposures are estimated as 237.9 and 18.8, respectively, for the SPLpeak

and SEL criteria. Bryde’s whales are the only low-frequency specialist. An estimated 0.1 and 

1.6 Bryde’s whales for the SPLpeak and SEL criteria, respectively, are predicted during the decadal 

period, with annual maxima of <0.1 and 0.5 exposures that may potentially occur, respectively. For 

the endangered sperm whale, it is estimated that 5.3 and 0.5 exposures may potentially occur for the 

SPLpeak and SEL criteria, respectively, during the decadal period, with annual maxima of 1.7 and 

0.2 exposures that may potentially occur, respectively.
4-52 Description of the Affected Resources and Impact Analysis

Deep-penetration 3D NAZ airgun seismic surveys are anticipated to be conducted on the 

continental shelf in the CPA (modeling Zone 2), a small amount on the WPA continental shelf 

(modeling Zone 3), but mostly in the western, central, and eastern slope regions (modeling Zones 4, 

5, 6, and 7; Appendix D, Table 75). No surveys are projected to occur on the EPA continental shelf 

(modeling Zone 1), and slightly decreasing levels of activity are expected in deeper waters. For the 

decadal period, bottlenose dolphins and Kogia are estimated to have the highest number of 

exposures that may potentially occur, with 20,841.3 and 3,033.6 potentially occurring exposures for 

the SPLpeak and SEL criteria, respectively. At an annual level, the highest numbers of bottlenose 

dolphin and Kogia potentially occurring exposures are estimated as 2,513.7 and 376.1, respectively,

for the SPLpeak and SEL criteria. An estimated 1.9 and 80.1 Bryde’s whale exposures may 

potentially occur for the SPLpeak and SEL criteria, respectively, during the decadal period, with 

annual maxima of 0.2 and 10.1 potential exposures, respectively. For the endangered sperm whale, 

it is estimated that 209.8 and 9.9 exposures may potentially occur for the SPLpeak and SEL criteria, 

respectively, during the decadal period, with annual maxima of 26.8 and 1.5 potential exposures, 

respectively.

Deep-penetration 3D WAZ airgun seismic surveys are anticipated to be conducted on the 

continental shelf in the CPA (modeling Zone 2) and on the WPA and EPA continental shelf and 

slope (modeling Zones 4, 6, and 7), but mostly in the CPA slope regions (modeling Zones 5 and 7; 

Appendix D, Table 75). No surveys are projected to occur in certain areas within the WPA and 

EPA continental shelf (modeling Zones 1 and 3). For the decadal period, Kogia are estimated to 

have the highest number of exposures that may potentially occur, with 17,564.6 and 328.7 potential 

exposures for the SPLpeak and SEL criteria, respectively. At an annual level, the highest number of 

potentially occurring Kogia exposures are estimated as 2,149.2 and 40.1, respectively, for the 

SPLpeak and SEL criteria. An estimated 0.4 and 8.0 exposures of Bryde’s whales may potentially 

occur for the SPLpeak and SEL criteria, respectively, during the decadal period, with annual maxima 

of 0.1 and 1.1 exposures potentially occurring, respectively. For the endangered sperm whale, it is 

estimated that 70.2 and 0.5 exposures may potentially occur for the SPLpeak and SEL criteria, 

respectively, during the decadal period, with annual maxima of 8.4 and 0.2 potentially occuring 

exposures, respectively.

Deep-penetration coil seismic surveys are anticipated to be conducted on the continental 

shelf in the CPA (modeling Zone 2) and on the WPA and EPA continental shelf and slope (modeling 

Zones 4, 6, and 7), but mostly in the CPA slope regions (modeling Zones 5 and 7; Appendix D, 

Table 75). No surveys are projected to occur in certain areas within the WPA and EPA continental 

shelf (modeling Zones 1 and 3). For the decadal period, pantropical spotted dolphins and Kogia are 

estimated to have the highest number of exposures that may potentially occur, with 5,027.9 and 

925.4 potential exposures, respectively, for the SPLpeak and SEL criteria. At an annual level, the 

highest number of pantropical spotted dolphin and Kogia exposures that may potentially occur are 

estimated as 603.6 and 113.2, respectively, for the SPLpeak and SEL criteria. An estimated 0.7 and 

28.1 potentially occurring exposures of Bryde’s whales for the SPLpeak and SEL criteria, respectively, 

are predicted during the decadal period, with annual maxima of 0.1 and 3.7 potential exposures, 

respectively. For the endangered sperm whale, it is estimated that 65.3 and 5.5 exposures may 
Gulf of Mexico G&G Activities Programmatic EIS 4-53

potentially occur for the SPLpeak and SEL criteria, respectively, during the decadal period, with 

annual maxima of 8.2 and 0.7 potentially occurring exposures, respectively.

Level B Estimates of Potentially Occurring Exposures

Level B (160 dB SPLrms and the step function criteria) exposure estimates were calculated 

for 21 cetacean species from proposed 2D, 3D NAZ, 3D WAZ, and coil survey activities during the 

10-year time period covered by this Programmatic EIS. Annual estimates of potentially occurring 

exposures for these taxa are presented in Appendix D. Total decadal, deep-penetration airgun 

seismic survey Level B estimates of potentially occurring exposures for each survey type are 

presented in Appendix D, Tables 76 through 79. For review, an overview of the Level B potentially 

occurring exposure estimates using NMFS’ 160 dB SPLrms metric is provided for each survey type.

Deep-penetration 2D airgun seismic surveys are anticipated to be conducted in the EPA and 

CPA, primarily in continental shelf and slope waters. This type of survey activity is projected to 

occur in six of the 10 years, with decreasing levels of activity expected for two to three of those years 

(Appendix D, Table 75). Over the decadal period, the highest number of 160 dB SPLrms exposures 

that may potentially occur are expected for pantropical spotted dolphins (233,759.0; Appendix D, 

Table 76), with the highest annual estimate of exposures that may potentially occur for this species 

at 78,810.7 in 2019 (Appendix D, Table F 33). Bryde’s whales are the only low-frequency 

specialist. An estimated 206.9 potentially occurring exposures of Bryde’s whales at received SPLrms

>160 dB are predicted during the decadal period, with an annual maximum of 68.5 potentially 

occurring exposures. For the endangered sperm whale, it is estimated that 17,049.9 exposures may 

potentially occur at received SPLrms >160 dB during the decadal period, with an annual maximum of 

5,749.3 potentially occurring exposures.

Deep-penetration 3D NAZ airgun seismic surveys are anticipated to be conducted on the 

continental shelf in the CPA (modeling Zone 2), a small amount on the WPA continental shelf 

(modeling Zone 3), but mostly in the western, central, and eastern slope regions (modeling Zones 4, 

5, 6, and 7; Appendix D, Table 75). No surveys are projected to occur in certain areas within the 

EPA continental shelf (modeling Zone 1), and slightly decreasing levels of activity are expected in 

deeper waters (Appendix D, Table 75). Over the decadal period, the highest number of 160 dB 

SPLrms exposures that may potentially occur are expected for bottlenose dolphins (8,897,488.1; 

Appendix D, Table 77), with the highest annual estimate for this species at 1,058,083 exposures 

that may potentially occur in 2019 (Appendix D, Table F-34). An estimated 4,136.5 potentially 

occurring exposures of Bryde’s whales at received SPLrms >160 dB are predicted during the decadal 

period, with an annual maximum of 534.2 potentially occurring exposures. For the endangered 

sperm whale, it is estimated that 440,333.7 exposures may potentially occur at received SPLrms

>160 dB during the decadal period, with an annual maximum of 59,889.8 exposures potentially 

occurring.

Deep-penetration 3D WAZ airgun seismic surveys are anticipated to be conducted on the 

continental shelf in the CPA (modeling Zone 2) and on the WPA and EPA continental shelf and 
4-54 Description of the Affected Resources and Impact Analysis

slope (modeling Zones 4, 6, and 7), but mostly in the CPA slope regions (modeling Zones 5 and 7; 

Appendix D, Table 75). No surveys are projected to occur in certain areas within the WPA and 

EPA continental shelf (modeling Zones 1 and 3). Over the decadal period, the highest number of 

160 dB SPLrms exposures that may potentially occur are expected for pantropical spotted dolphins 

(2,233,856.1; Appendix D, Table 78), with the highest annual estimate of potentially occurring 

exposures for this species at 274,838.2 in 2016 (Appendix D, Table F-14). An estimated 

1,778.4 potentially occurring exposures of Bryde’s whales at received SPLrms >160 dB are predicted 

during the decadal period, with an annual maximum of 229.3. For the endangered sperm whale, it is 

estimated that 182,929.6 exposures may potentially occur at received SPLrms >160 dB during the 

decadal period, with an annual maximum of 23,183.1.

Deep-penetration coil seismic surveys are anticipated to be conducted on the continental 

shelf in the CPA (modeling Zone 2) and on the WPA and EPA continental shelf and slope (modeling 

Zones 4, 6, and 7), but mostly in the CPA slope regions (modeling Zones 5 and 7; Appendix D, 

Table 75). No surveys are projected to occur in certain areas within the WPA and EPA continental 

shelf (modeling Zones 1 and 3). Over the decadal period, the highest number of 160 dB SPLrms

exposures that may potentially occur are expected for pantropical spotted dolphins (473,365.5; 

Appendix D, Table 79), with the highest annual estimate for this species at 58,113.2 in 2016 

(Appendix D, Table F-15). An estimated 365.1 potentially occurring exposures of Bryde’s whales at 

received SPLrms >160 dB are predicted during the decadal period, with an annual maximum of 46.9. 

For the endangered sperm whale, it is estimated that 40,181.5 exposures may potentially occur at 

received SPLrms >160 dB during the decadal period, with an annual maximum of 5,157.4.

Fitness Level Consequences of Level A and Level B Exposures

The deep-penetration seismic airgun survey activities have the potential to impact marine 

mammals more substantially than other activities included in the proposed action. Individual 

summaries of the potential exposures from each type of seismic airgun survey (i.e., 2D, 3D NAZ, 

3D WAZ, and coil) on an annual and decadal basis are provided above. These exposures are 

based on modeling of 24 hours of survey activities, which is then scaled by line-miles for each 

annual projection of activity level. There is insufficient information at this time to generalize a 

nominal duration for each survey type or estimate the number of each type of survey that may occur; 

the finest temporal resolution of activity level that can be projected is an annual estimate of the 

length of line-miles that would likely be surveyed based on historical trends. These projected activity 

levels have been spatially divided among seven zones representing shallow and deep waters of the 

EPA, CPA, and WPA, in addition to a deepwater zone spanning the three planning areas.

With the given 24-hour duration data, there is no mechanism to account for an individual 

animal being exposed more than once across multiple days of survey activity. To reasonably 

estimate the number of animals that may be exposed at any one time during a specific survey, the

exposure estimates must be considered within the context of the size of a nominal survey, the 

acoustic footprint of the sources, and the behavior patterns of the species in the given region.
Gulf of Mexico G&G Activities Programmatic EIS 4-55

Nominal 2D, 3D NAZ, and 3D WAZ surveys were estimated to cover an area of 

approximately 6,960 km2 (2,029 nmi2

; 2,687 mi2) (Appendix D, Table 47). A nominal coil survey is 

expected to cover an area of approximately 3,364 km2 (980.8 nmi2

; 1,298.8 mi2). If nominal offshore 

density estimates for a coastal and offshore dolphin species, the endangered sperm whale, the 

Bryde’s whale (a low-frequency specialist), and Kogia (a high-frequency specialist) are considered 

from the CPA (Zones 5 and 7 (Appendix D, Tables 66 and 68), which is the region projected to 

encompass the majority of deep-penetration airgun seismic survey activities (Appendix D, 

Table 75), approximately 399 bottlenose dolphins, 238 Clymene dolphins, 50 sperm whales, 

1 Bryde’s whale, and 51 Kogia would occur within the modeled survey area in Zone 5, and 

2 bottlenose dolphins, 183 Clymene dolphins, 33 sperm whales, 0 Bryde’s whales (amended after 

the JASCO modelling when Duke adjusted density estimates), and 24 Kogia would occur within the 

modeled survey area in Zone 7 for each 2D, 3D NAZ, and 3D WAZ survey.

The next component to consider is the acoustic footprint of the 8,000-in3 airgun array for 

each exposure criteria. Using the ranges to specific thresholds as calculated in Appendix D, the 

acoustic footprint was calculated as the two-dimensional circular area around the airgun array. For 

the SPLpeak criteria, low-frequency and mid-frequency cetaceans would be exposed within a 

0.0010 km2 (3.8610 mi2

) acoustic footprint; high-frequency cetaceans (Kogia) would exposed within 

a 1.04 km2 (0.40 mi2

) acoustic footprint. For the SEL criteria and the 95 percent ranges, lowfrequency, mid-frequency, and high-frequency cetaceans would be exposed within 0.045 km2

(1.737 mi2

), 0.008 km2 (3.089 mi2), and 3.80 km2 (1.47 mi2) acoustic footprints, respectively. 

Considering the same offshore density estimates from the CPA (Zones 5 and 7), no (0.00) 

bottlenose dolphins, Clymene dolphins, sperm whales, or Bryde’s whales would occur within the 

SPLpeak or SEL acoustic footprints; only 0.01 and 0.03 Kogia would be in SPLpeak or SEL acoustic 

footprints, respectively, in Zone 5; and 0.00 and 0.01 Kogia would be in SPLpeak or SEL acoustic 

footprints, respectively, in Zone 7. For the 160 dB SPLrms and the 95 percent ranges, the acoustic 

footprint for all species is 706.86 km2 (272.93 mi2

). Approximately 40 bottlenose dolphins, 

24 Clymene dolphins, 5 sperm whales, 0.1 Bryde’s whales, and 5 Kogia would occur within the 

160 dB footprint in Zone 5, and 2 bottlenose dolphins, 183 Clymene dolphins, 33 sperm whales, and 

0 Bryde’s whales would occur within the acoustic footprint in Zone 7.

The behavioral patterns of the species are detailed in Appendix D, but in general, the travel 

sub-models specifying horizontal movement (travel direction and rate) are fairly uniform. Species 

are expected to exhibit random walks, in which there is no directional preference, because there is 

no migratory behavior for species within the GOM. Travel rate varies slightly around the median 

value of 1.5 m/s. Therefore, though there are distributional habitat preferences reflected in the 

density estimates, there are no behavioral patterns that would restrict an animal to remain within the 

acoustic footprint or the survey area of deep-penetration airgun seismic survey activities.

To evaluate the potential for fitness impacts to an individual from potential Level A exposures 

(onset PTS), the number of animals within the acoustic footprint is compared with the number of 

animals within a nominal deep-penetration seismic survey area. Because of the small area of the 

Level A acoustic footprints, there is a vanishingly small potential for a low-frequency or mid-
4-56 Description of the Affected Resources and Impact Analysis

frequency hearing specialist animal to be within the acoustic footprint at any one time, and thus an 

even smaller probability of experiencing multiple exposures to Level A (onset PTS) acoustic energy. 

Because of the predicted higher sensitivity of high-frequency specialists (Kogia), the acoustic 

footprint is slightly larger; however, there is still a very small potential for an animal to be in the 

acoustic footprint (0.01 and 0.03 for SPLpeak and SEL criteria), thus an even smaller probability of 

experiencing multiple exposures to Level A (onset PTS) acoustic energy. It is not anticipated that 

any animal would experience fitness-level impacts from Level A exposures.

Level B exposures may result in animals experiencing temporary disturbance that might 

result in them either leaving the area or staying in the area and exhibiting behavioral changes, both 

conditions that could affect their metabolic rate (daily energy expenditures). Very limited research 

has been conducted on the basic energetic expenditures of cetaceans or how specific behavioral 

activities affect daily energy requirements. Metabolic rates are influenced by age, body size, growth, 

reproductive status, activity level, and environmental conditions (Noren, 2011). The swimming costs 

of minke whales and common dolphins were estimated from model parameters at ranges of 

2-3.5 and 2-4 times basal metabolic rate (Hind and Gurney, 1997). It is more appropriate to 

consider the energetic cost of swimming within a normal activity budget rather than comparing with

basal metabolic rates. Field metabolic rates calculated from daily activity budgets of resident killer 

whales were estimated at 5-7 times that of predicted basal metabolic rates (Noren, 2011). Of the 

activities that killer whales performed on a daily basis, traveling was the least demanding, whereas 

foraging required over 10 times more energy to be expended. Examining bottlenose dolphins, 

Williams et al. (1993) found that they exhibited a minimum cost of transport at their routine cruising 

speeds, but when trained to perform workload-bearing exercises, they could exhibit maximum 

oxygen consumption rates that were 7-11 times greater than standard metabolic rates. A similar 

result was determined for killer whales, in which the minimum cost of transport occurred at an 

optimal swim speed of 2.6-3 m/s (Williams and Noren, 2009); however, the average swimming 

speed (1.6 m/s) was lower than the predicted optimal swim speed. Given the range to the 

behavioral threshold is 15,000 m (49,213 ft), an animal swimming at 3 m/s (10ft/s) would need 

83.3 minutes or 1.4 hours to move out of the acoustic footprint. Using the daily activity budget 

calculated for killer whales (Noren, 2011) as a proxy for other species, this would double the time 

devoted to traveling, resulting in an additional 4.2 percent energy requirement. It is not anticipated 

that this additional energy requirement would result in potential fitness consequences to an 

individual; therefore, the energetic costs due to a behavioral reaction of leaving the acoustic footprint 

are estimated to be minimal.

If an animal decides to remain in the area of the deep-penetration seismic survey, it may 

exhibit vocal responses to the increased noise, such as signaling louder, longer, or more often. Only 

one study has experimentally measured the energetic consequences of vocal modifications in a 

marine mammal, the bottlenose dolphin (Holt et al., 2015). The study found that metabolic rates 

during the vocal period were, on average, 1.2-1.5 times resting metabolic rate. Given the radial 

range to the behavioral threshold is 15,000 m (49,213 ft) (thus the diameter of the zone of influence 

[ZOI] would be 30,000 m [98,425 ft]), and the modeled vessel speed of a deep-penetration seismic 

airgun survey was 4 kn (4.6 mph) (2.06 m/s [4.76 ft/s]; Appendix D), it would take 242.7 minutes or 
Gulf of Mexico G&G Activities Programmatic EIS 4-57

4.05 hours for the acoustic footprint to transit past a stationary marine mammal. It is unlikely that an 

animal would continuously vocalize for that entire period, but even if it did, considering the potential 

energetic costs, the effect on an individual’s fitness level would be quite small.

While a single exposure has the potential for effects to an individual as stated in Chapter 3, 

the proposed action has the potential to result in repeated exposures to individual or groups or pods 

over multiple sequential days or in the form of repeated exposures throughout the year (refer to the

modeling results in Appendix D). However, there are multiple factors that indicate that the potential 

for repeated exposures are unlikely to result in reduced fitness in individuals or populations. First, 

G&G surveys have been on-going in the northern GOM for many years, with no direct information 

indicating reduced fitness in individuals or populations. Additionally, most surveys are mobile, as are 

the marine mammals in the GOM. This makes it unlikely that any single action or area will result in 

increased noise levels that prevent marine mammals from exploiting an area for a period of time. 

Additionally, marine mammals have some ability to avoid impacts by moving away from the source 

of the disturbance. Minimum survey spacing will ensure that marine mammals will have areas 

where sound levels will not meet the threshold of harassment, and are therefore, better able to fully 

exploit these areas for feeding, migration, rearing, etc. Lastly, time area closures (for the 

appropriate alternative) will be especially protective of areas where marine mammals are for critical 

life history stages, and will therefore avoid effects to these animals when they are more likely to 

experience harassment that would cause impacts at times when they are less able to cope with 

those impacts.

Conclusions

Based on the understanding of the best available scientific data and estimated exposure 

modeling results, sounds produced during deep-penetration seismic airgun survey activities will 

impact individuals and groups of marine mammals within the AOI, including the ESA-listed 

(endangered) sperm whale and other whale and dolphin species on the continental shelf, shelf edge, 

and slope. The only baleen whale species that was modeled for exposure estimates, based on its 

distribution and relative density within the GOM, was the Bryde’s whale.

Using the SPLpeak and SEL criteria to estimate Level A exposures and the 160 dB SPLrms

criterion for Level B exposures, marine mammal species with the highest exposure estimates are the 

delphinids, all of which are mid-frequency specialists that are relatively insensitive to low-frequency 

sounds. Despite their low sensitivity to deep-penetration seismic airgun survey noise, the relatively 

high-density estimates for delphinids, such as the pantropical spotted dolphin and the bottlenose 

dolphin, result in large numbers of Level A and Level B exposures that may potentially occur. 

However, when considered within their estimated population sizes, the percentage of the population 

potentially exposed each year are 0.05 and 0.00 percent for pantropical spotted dolphins and 

bottlenose dolphins, respectively, to the SPLpeak threshold and 0.00 percent for pantropical spotted 

dolphins and bottlenose dolphins to the SEL threshold. The highest percentages of annual Level A 

exposures that may potentially occur relative to population size were for Kogia at 3.11 and 

0.25 percent for the SPLpeak and SEL criteria, respectively. The highest percentages of populations 
4-58 Description of the Affected Resources and Impact Analysis

potentially experiencing Level B exposures were the sperm whale (80.12%) and beaked whales 

(49.74%); most delphinid species are estimated at 30-40 percent of the population on an annual 

basis. The relatively high percentages levels of Level B exposures potentially occurring for sperm 

whales and beaked whales in the AOI may be attributed to the relatively high proportion of deeppenetration seismic airgun activities planned in deepwater environments within the CPA, including 

both the area within Mississippi Canyon and the GOM deepwater area >2,000 m (6,562 ft) that 

support relatively high densities of sperm and beaked whales.

The direct impact of any actual Level A harassment to marine mammals within the AOI from 

deep-penetration seismic airgun activities would only include hearing (auditory) injury onset, 

specifically the onset of PTS impairment to individual or small groups of whales and dolphins. The 

PTS onset injury is likely to be measured in a few dB loss in hearing sensitivity, not profound loss, 

because most predicted incidents of auditory injury would occur at greater rather than closer range 

to the source. The effects of hearing (auditory) injury to marine mammals could cause some 

reduction in communication and foraging ability.

The onset of TTS, part of MMPA Level B harassment, might also occur in individuals or small 

groups. The TTS also has the potential to decrease the range over which socially significant 

communication takes place (e.g., communication between competing males, between males and 

females during mating season, and between mothers and calves). The effect of Level B harassment 

to marine mammals beyond the immediate behavioral response is a matter of ongoing investigation, 

but an attempt to estimate the potential fitness consequence to an individual is included in the 

section above. Given the estimated densities of local whale and dolphin populations, large survey 

areas, (Table 4.2-1) and duration of some G&G activities (Table 3.2-8), it is likely that individual 

animals may experience multiple days of exposure to airgun noise causing TTS each year during the 

10-year time period covered by this Programmatic EIS.

Potential behavioral harassment was estimated using the current NMFS Level B MMPA 

criterion (160 dB rms). Estimates of potential exposure suggest that large numbers of individual 

cetaceans could experience non-injurious impacts from seismic airgun surveys during the project 

period. Given the estimated stock sizes of local cetacean populations (Table 4.2-1) and projected 

level of activities (Table 3.2-8), individual animals might experience multiple exposures to airgun 

noise during the 10-year time period covered by this Programmatic EIS. Studies do demonstrate 

disturbance of activities or avoidance or temporary displacement from seismic surveyed areas, both 

at long ranges within the acoustic footprint of the seismic airgun array and at short ranges as 

received levels increase (Miller et al., 2009). Behavioral responses of marine mammals to acoustic 

stimuli vary depending on the species, the context of the animals’ activities at the time of 

ensonification (e.g., feeding, migrating, calving, etc.), the properties of the stimuli, and prior exposure 

of the animals (Wartzok et al., 2004; Nowacek et al., 2007). Species-related response to 

anthropogenic noise may vary between taxonomic groups that have different hearing and sensitivity 

frequencies (NRC, 2005). Studies suggest that anthropogenic sounds such as seismic airgun 

surveys may affect behaviors of vocalizing baleen whales at distances greater than what is presently 

calculated, based on sound source characteristics and sound propagation modeling (Risch et al., 
Gulf of Mexico G&G Activities Programmatic EIS 4-59

2012). Furthermore, the acoustic response to seismic sounds can be more complex than initially 

thought (Blackwell et al., 2015).

There are no data on the response of Bryde’s whales to seismic sound. Širović et al. (2014) 

suggest that a representative source level for Bryde’s whale vocalizations is 152 dB re 1 μPa at 1 m 

(3 ft) for the 100-Hz band based on the broadband source level for Bryde’s moans of 155 dB re 

1 μPa at 1 m (3 ft). Intermediate range communication between individuals, therefore, cannot be 

ruled out and may be impacted for short durations during deep-penetration seismic airgun surveys. 

(Refer to Appendix K for further discussion on cumulative and chronic effects from airgun noise in 

the GOM with a particular emphasis on assessing the potential loss of Bryde’s whale communication 

space.)

Seismic airgun surveys associated with the proposed activity would occur in open ocean 

areas following standard survey lines where highly mobile whales and dolphins are able to move 

freely to avoid the acoustic footprint of the relatively slow-moving sound source, thus potentially 

avoiding exposure to injurious sound levels. Because these surveys will occur within the open 

GOM, there are no physical features that would restrict the movement of animals and it is not likely 

that a survey vessel would entrap animals between a sound source and shore. It is presumed that 

exposure to elevated sound for any given survey would be limited to some distance outside of a 

survey plot (and not Gulfwide at any given time) and somewhat temporary in duration. In summary, 

the best available information, while providing evidence for concern and a basis for continuing 

research, does not, at this time, provide grounds to conclude that these surveys would disrupt 

behavioral patterns with more than negligible population-level impacts.

The Seismic Airgun Survey Protocol (Appendix B, Attachment 1) required under 

Alternative A specifies mitigation measures for marine mammals that are meant to decrease and 

reduce the potential for Level A and Level B exposures. This includes an exclusion zone, ramp-up 

requirements, visual monitoring by PSOs, and airgun array shutdown requirements for specific 

whale species (i.e., Bryde’s, beaked, sperm, or dwarf and pygmy sperm whales). Even with these 

mitigation measures in place, airgun surveys have the potential to expose animals in survey areas. 

Although the duration of potential exposure on any given day is assumed to be limited, vessels may 

remain in the foraging range of animals for days or weeks. Any affected individuals might remain in 

a particular area for varying lengths of time (i.e., they may have different residency patterns). The 

model output predicts the number of potentially occurring exposures on a 24-hour basis, which is 

then scaled to annual and decadal exposures based on historical use trends. In the “Fitness Level 

Consequences of Level A and Level B Exposures” section above, an attempt is made to estimate 

the potential for repeated exposure of an individual.

This analysis uses the upper limit of potential exposures provided in the modeled estimates, 

applies what is known about the likelihood of species in the AOI reacting to seismic airgun noise, 

and considers the range of responses from animals that may occur, thereby limiting the potential for 

Level A exposure and reducing the potential for Level B exposure. With the implementation of 

mitigation measures for all marine mammals providing additional protection not considered in the 
4-60 Description of the Affected Resources and Impact Analysis

modelling, the effects of project-related seismic airgun survey noise on marine mammals within the 

AOI, considering the upper limits of estimated potential exposures, are expected to be moderate

depending on the population (stock), as potential exposures of marine mammals are expected to be 

extensive (potentially affecting large numbers of individuals within areas of the AOI) but not severe 

(the definition of severe is a life-threatening or debilitating injury or mortality in sufficiently high 

numbers that the continued viability of the population is threatened). The likelihood of fitness effects 

to individuals from potential exposures would be minor depending on the population (stock); 

however, a large percentage of several species may potentially experience exposures that could 

induce behavioral reactions. Potential injurious impacts to individual species of marine mammals 

would include PTS in low enough numbers such that the continued viability of the local populations 

or stocks will not be threatened if actual impacts were to occur, and the annual rates of recruitment 

or survival of the local populations or stocks will not be seriously affected.

General human activity, including shipping and distant seismic surveys, has raised the 

ambient noise level in the GOM, chronically reducing the communication space of marine animals 

(Clark et al., 2009). Non-injurious potential impacts resulting from a change in acoustic habitat 

(Merchant et al., 2015) would be dependent on the level of seismic activity present in an animal’s 

acoustic habitat, including the frequency and duration of survey activity. For example, in areas 

where seismic activity is more limited, effects might include temporary displacement of individuals 

potentially from preferred areas in some cases. In these instances, animals are expected to return 

to these areas following the distancing of the sound source, which would occur after approximately 

4 hours as calculated in the “Fitness Level Consequences of Level A and Level B Exposures” 

section above, or the cessation of survey activities. In areas where seismic noise is more chronic, 

animals may be displaced longer term from important biological areas, communication between 

individuals may be hampered, and greater energetic consequences may result. (Refer to 

Appendix K for further discussion on cumulative and chronic effects from airgun noise in the GOM 

with a particular emphasis on assessing the potential loss of Bryde’s whale communication space.)

4.2.2.1.3 HRG Survey Activities

The HRG site surveys are conducted to investigate the shallow subsurface for geohazards 

and soil conditions in a specific location or over a broad area and to identify potential benthic 

biological communities and archaeological resources. The HRG surveys and related equipment are 

discussed in Appendix F. The HRG surveys use several techniques, including airguns and 

electromechanical sources such as side-scan sonars, shallow- and medium-penetration subbottom 

profilers, and SBESs or MBESs. For this analysis, shallow-penetration seismic airgun surveys used 

for HRG site surveys are discussed separately from electromechanical source (non-airgun) surveys, 

though these sources may be used together. In such a scenario, the airgun sources are the 

dominant sound producers.

Shallow-Penetration Seismic Airgun Survey Activities 

Airgun sources (typically 1 or 2 airguns) used for shallow-penetration seismic airgun surveys 

are smaller (typically 20 to 100 in3

), and the interval between airgun shotpoints are shorter than for 
Gulf of Mexico G&G Activities Programmatic EIS 4-61

conventional deep-penetration 2D and 3D airgun seismic surveys. For this study, a single 90-in3

airgun was modeled (Appendix D). Shallow-penetration seismic airgun surveys are anticipated to 

be conducted on the continental shelf and slope in the CPA (modeling Zones 2 and 5) and in deep

water in all three planning areas (modeling Zone 7) (Appendix D, Table 75).

Level A Estimates of Potentially Occurring Exposures

Total decadal estimates of potentially occurring exposures for proposed shallow-penetration 

airgun seismic surveys over the 10-year time period covered by this Programmatic EIS using the 

SEL and SPLpeak criteria are presented in Appendix D, Table 80. Annual estimates of potentially 

occurring exposures are provided in Appendix F of Appendix D. Level A estimates of potential 

exposure were not predicted for any species for five of the 10 years because no shallow-penetration 

seismic airgun survey activity is projected during that time (Appendix D, Table 75). When 

considering the SPLpeak and SEL criteria for the decadal period, no SEL potential exposures are 

predicted and the only 0.1 SPLpeak potentially occurring exposures are predicted for Kogia

(Appendix D, Table 80). At an annual level, the 0.1 Kogia potential exposures are estimated to 

occur in only one of the 10 years (Appendix D, Table F-44). No potential Level A exposures of 

Bryde’s whale, the only mysticete in the GOM, or the endangered sperm whale are anticipated.

Level B Estimates of Potentially Occuring Exposures

Level B (NMFS 160 dB SPLrms) estimates of potentially occurring exposures were calculated 

for proposed HRG airgun (shallow-penetration seismic) survey activities conducted over the 10-year 

period. Total Level B potential exposure estimates for the period of 10 years are presented in 

Appendix D, Table 80. The highest number of 160 dB SPLrms potential exposures is expected for 

bottlenose dolphins (353.6), with the highest annual estimate for this species at 95.7 potentially 

occurring exposures in one of the projected years (Appendix D, Table F-37). Bryde’s whales are 

the only low-frequency specialist. No potentially occurring exposures of Bryde’s whales at received 

SPLrms >160 dB are predicted during the decadal period because no surveys are projected for the 

EPA. For the endangered sperm whale, it is estimated that 4.6 exposures would potentially occur at 

received SPLrms >160 dB during the decadal period, with these potential exposures occurring in one 

of the projected years (Appendix D, Table F-44).

Conclusions

Noise from shallow-penetration seismic airgun surveys may impact individual marine 

mammals within the AOI. As for other survey types previously analyzed in this Programmatic EIS, 

no lethal impacts are predicted to potentially occur during shallow-penetration airgun surveys. When 

considering the SPLpeak and SEL criteria for the decadal period, no SEL exposures are predicted to 

potentially occur for any species. The only decadal SPLpeak potential exposures are predicted for 

Kogia at 0.1. Level B potential exposure estimates for shallow-penetration airgun surveys predicted 

using NMFS’ 160 dB SPLrms criteria were also very low for the 10-year project period, with the 

highest estimated potentially occurring exposures for bottlenose dolphins (353.6), Atlantic spotted 
4-62 Description of the Affected Resources and Impact Analysis

dolphins (104.1), and pantropical spotted dolphins (25.3) over the 10-year period; <5 potential 

exposures to any other species are expected.

Shallow-penetration seismic airgun surveys associated with the proposed action are planned 

to occur in open ocean areas where highly mobile cetaceans may move freely to avoid the relatively 

slow-moving sound source, thus potentially reducing or minimizing any potential exposure to 

injurious sound levels and reducing the potential to receive sound at levels that may affect behavior. 

In addition, the Seismic Airgun Survey Protocol required under Alternative A includes mitigation 

measures such as an exclusion zone, ramp-up requirements, visual monitoring by PSOs, and 

shutdown requirements for specific whale species (i.e., Bryde’s, beaked, sperm, or dwarf and pygmy 

sperm whales). These single airgun surveys would be performed in relatively small areas (72.5 km2

; 

28.0 mi2

) and conducted in a systematic and predictable fashion along closely spaced, pre-plotted 

transects; therefore, exposure to elevated sound is presumed to be localized and temporary in 

duration.

Based on the output (source level) of the single airgun used in shallow-penetration seismic 

airgun surveys, estimates of potential exposure of marine mammals within the AOI are low or zero; 

therefore, these impacts are considered neither extensive nor severe. Potential impacts to marine 

mammals would include temporary auditory injuries (TTS); temporary disruptions of communication 

or echolocation (auditory masking); behavioral disruptions of individual or localized groups of marine 

mammals; and limited, localized, and short-term displacement of individuals of any species, 

including strategic stocks, from project-related areas of ensonification. No mortality and very limited 

potential for physical injury (PTS) to any individual marine mammal would be expected to occur. No 

fitness impacts to any species are expected. Based on the expected impacts described above and 

the impact significance criteria listed in Chapter 4.2.2.1, the effects of project-related, shallowpenetration seismic airgun survey noise on marine mammals within the AOI would be minor. 

Non-Airgun HRG Survey Activities

Equipment and methods associated with acoustic non-airgun HRG surveys are discussed in 

Appendix F, Section 1.3. Projected non-airgun HRG survey levels are discussed in Chapter 3.2

and listed in Table 3.2-8. Electromechanical (non-airgun) equipment that is commonly used in 

acoustic HRG surveys includes shallow- or medium-penetration subbottom profilers (e.g., pingers, 

sparkers, boomers, and CHIRP subbottom profilers), side-scan sonars, and SBESs or MBESs. 

These electromechanical sources are adjustable in terms of main operating frequency bands; 

however, they can be considered narrow band sources, as the acoustic energy emitted outside the 

main operating frequency band is nominal. Electromechanical sources can be highly directive, with 

beam widths as narrow as a few degrees or less.

Several electromechanical sound sources, including a 400-kHz side-scan sonar, 200-kHz 

CHIRP subbottom profiler, and 240-kHz MBES, would operate within a frequency range that is 

inaudible to cetaceans within the AOI. Frequency outputs from other electromechanical sources 

would be audible to marine mammals in the AOI, including a 0.3- to 3-kHz boomer, 16-kHz side-
Gulf of Mexico G&G Activities Programmatic EIS 4-63

scan sonar, and 4- and 24-kHz CHIRP subbottom profilers. Appendix F provides more discussion 

regarding the application of non-airgun HRG surveys and their impacts to marine mammals due to 

operational frequencies.

This analysis of potential impacts of non-airgun HRG surveys associated with the proposed 

action to marine mammals within the AOI are based on modeled estimates of total Level A and 

Level B exposures from proposed boomer surveys and other non-airgun HRG surveys within the 

AOI. In this analysis, other non-airgun HRG surveys assume the use of side-scan sonars, 

subbottom profilers, and MBESs. Methods for the estimation of the acoustic field of each non-airgun 

HRG survey sound source and subsequent estimations of incidental exposure are provided in 

Appendix D. These non-airgun HRG electromechanical sound sources may be used in 

combination with airgun sources. In such cases, exposures from the airgun sources will dominate 

over potential exposures from the HRG electromagnetic sources.

Boomer Survey Activities

The representative boomer system modeled was the Applied Acoustics AA301 Boomer 

system, based on a single plate with an approximate baffle diameter of 40 cm (15.7 in) 

(Appendix D). Because the boomer plate has a circular piston surrounded by a rigid baffle, it has 

acoustic directivity and cannot be considered a point-like source (Verbeek and McGee, 1995). The 

beam pattern of a boomer plate shows directivity for frequencies above 1 kHz. The input energy for 

the AA301 boomer plate is up to 350 joules (J) per pulse or 1,000 J per second. The width of the 

pulse is 0.15 to 0.4 milliseconds (ms). The parameters of the AA301 boomer used for modeling 

were as follows:

• operating frequency (wide band): 100 Hz to 10 kHz;

• beams: 1;

• beam width: omnidirectional -11°;

• beam direction: vertically down;

• maximum energy input (per shot): 350 J;

• SPLrms: 198 dB re 1 μPa at 1 m, TrmsSPL = 0.2 ms (estimated from field 

measurements; Martin et al., 2012); and

• per pulse SEL: 171 dB re 1 μPa2

•s at 1 m (estimated from field measurements; 

Martin et al., 2012).

Boomer survey activities are anticipated to be conducted on the continental shelf and slope 

in the CPA (modeling Zones 2 and 5) and in deep water in all three planning areas (modeling 

Zone 7) (Appendix D, Table 75). Boomer survey activities are projected to occur only in two of the 

10 years.
4-64 Description of the Affected Resources and Impact Analysis

Level A Estimates of Potentially Occurring Exposures

Total decadal estimates of potentially occurring exposures for proposed boomer activity 

during the time period covered by this Programmatic EIS using the SEL and SPLpeak criteria are 

presented in Appendix D, Table 81. Level A potential exposure estimates were not predicted for 

any species for 5 of the 10 years because no boomer activity is projected (Appendix D, Table 75). 

When considering the SPLpeak and SEL criteria for the decadal period, no SEL potentially occurring 

exposures are predicted and the only SPLpeak potentially occurring exposures are predicted for 

Kogia, with 0.1 potential exposures (Appendix D, Table 81). At an annual level, the 0.1 Kogia

potential exposures are estimated to occur in one of the projected years. No Level A potential 

exposures of Bryde’s whale, the only mysticete in the GOM, or the endangered sperm whale are 

anticipated.

Level B Estimates of Potentially Occurring Exposures

Level B (NMFS 160 dB SPLrms) estimates of potentially occurring exposures were calculated 

for proposed boomer activities projected to occur over the 10-year period. Total decadal Level B 

potentially occurring exposure estimates are presented in Appendix D, Table 81. Over the decadal 

period, the highest number of 160 dB SPLrms potential exposures is expected for bottlenose dolphins 

(51.0; Appendix D, Table 81), with the highest annual estimate for this species at 48.1 potential 

exposures (Appendix D, Table F-38). Bryde’s whales are the only low-frequency specialist. No 

exposures of Bryde’s whales at received SPLrms >160 dB are predicted to potentially occur during 

the decadal period because no surveys are projected for the EPA. For the endangered sperm 

whale, it is estimated that 3.1 exposures at received SPLrms >160 dB may potentially occur during 

the decadal period, with these potential exposures occurring during one of the projected years 

(Appendix D, Table F-45).

Other Non-Airgun HRG (Electromechanical) Survey Activities

Other non-airgun HRG electromechanical survey equipment considered for this modeling 

effort included an MBES, side-scan sonar, and a subbottom profiler (Appendix D). All three sources 

were considered to operate simultaneously. The towing depth was considered to be 4 m (13 ft) 

below the sea surface if the water depth was <100 m (328 ft) and 40 m (131 ft) above the seafloor in 

the areas with water depths >100 m (328 ft).

For the MBES, the operational parameters producing the greatest acoustic impact were 

modeled. In this case, the Simrad EM2000 MBES was modeled at the operational frequency of 

200 kHz, with a maximum source level of 203 dB re 1 μPa at 1 m and pulse length of 1.3 ms.

The representative side-scan sonar (EdgeTech 2200 IM) was modeled at two operational 

frequencies: 120 and 410 kHz. The SPLrms was estimated based on the peak source levels of 

207 and 213 dB re 1 μPa at 1 m for the 120- and 410-kHz center frequencies, respectively. The 

SEL was estimated based on the SPLrms values and the pulse lengths to derive SEL source levels of 

186 and 187 dB re 1 μPa2

•s for the 120- and 410-kHz center frequencies, respectively.
Gulf of Mexico G&G Activities Programmatic EIS 4-65

The representative CHIRP subbottom profiler was the EdgeTech 2200 IM, DW-424. The 

EdgeTech 2200 IM system was modeled at a single frequency (14 kHz). The SPLrms source level 

was 200 dB re 1 μPa at 1 m. The SEL source level was estimated based on the SPLrms and the 

pulse length to derive a SEL source level of 180 dB re 1 μPa2

•s. The beam width was estimated at 

20° at the center frequency.

Other non-airgun HRG electromagnetic survey activities are anticipated to be conducted on 

the continental shelf in the WPA, CPA, and EPA (modeling Zones 1, 2, and 3) and on the WPA, 

CPA, and EPA continental shelf, slope, and deep waters (modeling Zones 4, 5, 6, and 7; 

Appendix D, Table 75). No surveys are projected to occur on the EPA continental shelf (modeling 

Zone 1) after the first 3 years (Appendix D, Table 75).

Level A Estimates of Potentially Occurring Exposures

Total decadal estimates of potentially occurring exposures for proposed non-airgun HRG 

electromagnetic activities during the time period covered by this Draft Programmatic EIS using the 

SEL and SPLpeak criteria are presented in Appendix D, Table 82. Further, Appendix F of 

Appendix D provides annual potentially occurring exposure tables for all species by each survey 

type for each year. Level A potential exposures are provided using the SEL, SPLpeak, and SPL

(180dB) threshold criteria. When considering the SPLpeak and SEL criteria for the decadal period, no 

SPLpeak potential exposures are predicted. The highest decadal SEL potentially occurring exposures 

are predicted for bottlenose dolphins, with 95.2 potential exposures (Appendix D, Table 82). The 

highest annual bottlenose dolphin potentially occurring exposure is predicted at 11.0 potential 

exposures in one of the projected years (Appendix D, Table F-46), though similar numbers of 

potentially occurring exposures are predicted for three additional years (Appendix F of 

Appendix D). No Level A potential exposures of Bryde’s whale, the only mysticete in the GOM, are 

anticipated. For the endangered sperm whale, 0.3 SEL potential exposures are predicted for the 

decadal period (Appendix D, Table 82), with all annual estimates being <0.1 potential exposures.

Level B Estimates of Potentially Occurring Exposures

Level B (NMFS 160 dB SPLrms) estimates of potentially occurring exposures were calculated 

for proposed other non-airgun HRG electromagnetic activities projected to occur over the 10-year 

period. Total decadal Level B potential exposure estimates are presented in Appendix D, Table 82. 

Over the decadal period, the highest number of 160 dB SPLrms potentially occurring exposures are 

expected for bottlenose dolphins (68.5; Appendix D, Table 82), with the highest annual estimate for 

this species at 8.3 potential exposures (Appendix D, Table F-18), though similar numbers of 

potential exposures are predicted for three additional years. Bryde’s whales are the only lowfrequency specialist. No potentially occurring exposures of Bryde’s whales or sperm whales at 

received SPLrms >160 dB are predicted during the decadal period.
4-66 Description of the Affected Resources and Impact Analysis

Conclusions

Noise from non-airgun HRG electrometrical surveys utilizing boomers and other selected 

acoustic HRG survey equipment (i.e., MBES, side-scan sonar, and subbottom profiler) may impact 

individual marine mammals within the AOI. Similar to other survey types previously analyzed in this 

Programmatic EIS, no lethal impacts are predicted for HRG electromechanical surveys. When 

considering the SPLpeak and SEL criteria for the decadal period, the only decadal SPLpeak potentially 

occurring exposures are predicted for Kogia at 0.1. The highest decadal SEL potential exposures 

are predicted for bottlenose dolphins, with 95.2 potential exposures (Appendix D, Table 82). The 

next highest species are Atlantic spotted dolphins and striped dolphins with 8.2 potentially occurring 

exposures; seven other species have potential exposures <0.7. Total Level B potentially occurring 

exposure estimates for boomer and other HRG electromechanical surveys using NMFS’ 160 dB 

SPLrms criteria were also very low for the 10-year project period, with the highest estimated potential 

exposures for bottlenose dolphins (119.5) and Atlantic spotted dolphins (26.4) over the 10-year 

period.

Based on the results of this analysis, the effects of HRG electromechanical survey noise on 

marine mammals within the AOI are expected to be minor. Potential impacts from potentially 

occurring exposures over the project period include limited behavioral impacts and low (limited) 

number of physical injuries (PTS). The behavioral impacts may include temporary disruption of 

communication or echolocation from auditory masking; behavior disruptions of individual or localized 

groups of marine mammals; and limited, localized, and short-term displacement of individuals from 

the area of ensonification. None of these effects are expected to result in fitness impacts to any 

species.

4.2.2.1.4 Vessel and Equipment Noise

Proposed G&G activities would generate vessel and equipment noise that could disturb 

marine mammals. The types of sounds produced by these sources are classified as non-pulsed, or 

continuous. As discussed in Chapter 3.4.1.2.1, vessel noise is a combination of narrow band (tonal) 

and broadband sound (Richardson et al., 1995). Tones typically dominate up to approximately 

50 Hz, whereas broadband sounds may extend to 100 kHz. Analyses of radiated sound from ships 

have revealed that they are the dominant source of underwater noise at frequencies below 300 Hz in 

many areas (Okeanos, 2008).

Vessel and equipment noise from G&G vessels, including survey and support vessels 

associated with activities described in Alternative A, would produce sound levels typically <190 dB 

rms re 1 μPa at 1 m of underwater noise. The current acoustic threshold established by NMFS for 

sub-injurious exposure to a continuous noise source is 120 dB re 1 μPa (rms). This threshold was 

based on avoidance responses observed in whales, specifically from research on migrating gray 

whales and bowhead whales (Malme et al., 1983, 1984, and 1988; Richardson et al., 1986 and

1990; Dahlheim and Ljunblad, 1990; Richardson and Malme, 1993). As discussed in Chapter 

4.2.2.1, the one mysticete that occurs within the AOI, Bryde’s whales is especially vulnerable to 

impacts from vessel noise because they produce and perceive low-frequency sounds (Southall,
Gulf of Mexico G&G Activities Programmatic EIS 4-67

2005). Broadband propulsion source levels for vessel types that would include seismic survey 

vessels and vessels for drilling of COST wells or shallow test wells are anticipated to be in the range 

of 170 to 180 dB re 1 μPa at 1 m and source levels for smaller boats are in the range of 150 to 170 

dB re 1 μPa at 1 m (Richardson et al., 1995). These noise and frequency levels are within the 

audible range for all GOM cetacean species (including Bryde’s whales) and, near these sources, 

exceed NMFS’ threshold for potential Level B harassment by continuous sound sources (120 re 1 

μPa at 1 m dB received level). In the open ocean deepwater environment where spherical 

spreading conditions apply, an attenuation of 60 re 1 μPa at 1 m dB (e.g., reduction from a source 

level of 180 dB re 1 μPa at 1 m to the 120-dB continuous noise threshold) would occur within 1 km 

(0.6 mi) of the source. Where modified spherical spreading conditions may apply, the distance from 

source to the 120-dB threshold would be greater.

As discussed in Appendix F, vessels conducting deep-penetration seismic airgun surveys 

(i.e., 2D, 3D, and 4D surveys) are large in size (60 to 90 m [197 to 295 ft] in length) and would 

account for most of the proposed survey miles traveled, and (under Alternative A) these surveys 

could occur anywhere within the AOI. Most seismic surveys, however, will occur in deepwater areas 

of the CPA throughout the project period (Table 3.2-2). The WAZ surveys generally involve multiple 

vessels operating in concert in a variety of vessel geometries (Appendix F, Section 1.1.4). Vessel 

and helicopter traffic associated with the proposed activities is described in Chapters 3.3.1.3 and 

3.3.1.4, and the level of activity is estimated in Table 3.2-7. 

Vessels conducting sampling activities for HRG surveys would be smaller and operate 

mainly at specific sites (consisting of one or more OCS lease blocks) and along potential cable 

routes to shore. Survey vessels for nearshore projects are expected to make daily round-trips to 

their shore base.

Many marine mammal species may be vulnerable to impacts from vessel noise because 

marine mammals produce and perceive low- to mid-frequency sounds. Most of the acoustic energy 

radiated from commercial vessels is below 1 kHz; however, other sources of sound often dominate 

ambient noise at frequencies >300 Hz. In addition to direct disturbance, an additional effect of 

increased ambient noise on marine mammals is the potential for that noise to mask biologically 

significant sounds (Chapter 4.2.2.2).

Studies of vessel noise on GOM sperm whales indicated a significant decrease in the total 

number of acoustic clicks detected as a tanker ship approached an area (Azzara et al., 2013). 

Individuals of several small-toothed whale and dolphin species have been observed to avoid boats 

when they are within 0.5 to 1.5 km (0.3 to 0.9 mi), with occasional reports of avoidance at greater 

distances (Richardson et al., 1995). Most beaked whales tend to avoid vessels (Würsig et al., 1998; 

Aguilar-Soto et al., 2006) and may dive for an extended period of time when approached by a vessel 

(Kasuya, 1986). Dolphins may tolerate boats of all sizes, often approaching and riding the bow and 

stern waves (Shane et al., 1986; Barkaszi et al., 2012). At other times, dolphin species that typically 

are attracted to boats will avoid them. Such avoidance is often linked to previous boat-based 

harassment of the animals (Richardson et al., 1995). Coastal bottlenose dolphins that are the object 
4-68 Description of the Affected Resources and Impact Analysis

of whale-watching activities have been observed to swim erratically (Acevedo, 1991), remain 

submerged for longer periods of time (Janik and Thompson, 1996; Nowacek et al., 2001), display 

less cohesiveness among group members (Cope et al., 1999), whistle more frequently (Scarpaci 

et al., 2000), and display restless behavior (Constantine et al., 2004) when boats are nearby.

Marine geophysical vessels are designed to operate relatively quietly to minimize potential 

sources of interference to collected seismic data (International Association of Geophysical 

Contractors, 2002; Polarcus, 2011). From these reports, it is conservative to assume that noise 

associated with G&G survey vessels associated with the proposed action but not actively surveying 

may elicit behavioral changes in marine mammals that are in close proximity to the vessels. As 

discussed previously, behavioral changes range from evasive maneuvers (such as diving or 

changes in swimming direction or speed) to attraction to the moving vessel (bow riding). Because 

these vessels are generally quiet, machinery and other propulsion-related noise is transitory and 

does not propagate great distances from the vessel. For the majority of time that seismic vessels 

are underway within the AOI, they would be operating airguns or other active acoustic sound 

sources; under these conditions, estimates of potential acoustic disturbance or harassment (Level B 

exposure), numbers already have been accounted for. When non-airgun HRG seismic vessels are 

operating, or when seismic vessels are not actively surveying, the potential for behavioral impacts 

from vessel and equipment noise remains.

Under Alternative A, all authorizations for G&G surveys would include guidance for 

maintaining safe distances between G&G vessels and protected species during transit to minimize 

potential impacts from vessel noise with these protected species (NTL 2016-BOEM-G01), which 

incorporates NMFS’ “Vessel Strike Avoidance Measures and Reporting for Mariners,” addressing 

protected species identification, vessel strike avoidance, and injured/dead protected species 

reporting. Mitigation measures are listed in Chapter 2.1.2 and detailed in Appendix B, Section 1. 

For this analysis, it is expected that the proposed additional volume of vessel traffic 

associated with Alternative A would not constitute a significant increase to existing vessel traffic 

within the AOI. Based on the proposed volume of vessel traffic (Table 3.2-7) and the presumption 

that individual or groups of marine mammals within the AOI are familiar with various and common 

vessel-related noises, particularly within trafficked areas of the continental shelf and frequented 

shipping lanes, the effects of project-related vessel and equipment noise on marine mammals within 

the AOI would be nominal to minor. Impacts to marine mammals from project-related vessel and 

equipment noise are expected but are not extensive or severe, and would include temporary 

disruption of communication or echolocation from auditory masking; behavior disruptions of 

individual or localized groups of marine mammals; and limited, localized, and short-term 

displacement of individuals of any species, including strategic stocks, from localized areas around 

the vessels.
Gulf of Mexico G&G Activities Programmatic EIS 4-69

4.2.2.1.5 Drilling-Related Noise

In addition to the ship and dynamic positioning noise discussed above, drilling-related noises 

anticipated during the time period of this Programmatic EIS include the completion of one possible 

COST well and up to two shallow test wells in the AOI. The COST wells are funded by industry 

consortia; are drilled off structure so as not to encounter hydrocarbons; and are intended to provide 

information about regional stratigraphy, the existence and potential quality of reservoir beds, and the 

existence of potential hydrocarbon source rocks. Drilling is done by conventional rotary drilling 

equipment from a drilling rig. Noise generated by COST well completions includes drilling noise and 

rig positioning noise (specifically, noise from dynamic positioning [DP] equipment).

Noise from drilling operations includes strong tonal components at low frequencies 

(<500 Hz), including infrasonic frequencies in at least some cases (Richardson et al., 1995). 

Machinery noise can be continuous or transient, and variable in intensity. Noise levels vary with the 

type of drilling rig and the water depth. Drilling-related noise from bottom-founded platforms is 

continuous and generally of very low frequencies (near 5 Hz); therefore, it is expected to be within 

the audible range of only baleen whales. Sound source levels of drilling from jack-up platforms may 

range from 119 to 127 dB re 1 μPa at near-field locations (Richardson et al., 1995). Drilling-related 

noises from semisubmersible platforms in deeper waters range in frequency from 10 to 4,000 Hz, 

and therefore is audible to all cetacean species within the AOI. Drilling sound source levels from 

semisubmersible platforms are estimated at 154 dB re 1 μPa-m. Source levels for drillships have 

been reported to be as high as 191 dB re 1 μPa during drilling. Noise levels from drillships generally 

are higher than semisubmersibles, as the drillships have a large hull area that is well coupled to the 

water, and sound paths of vessel and drill machinery to the water are direct as compared with

semisubmersibles, where sound and vibration paths are through the air or through risers 

(Richardson et al., 1995).

It is assumed that drilling rigs used for COST well operations will be jack-up or 

semisubmersible rigs in deepwater areas. The latter may use DP to keep the rig in place. Studies 

on drillships using DP recorded noise between 20 and 35 kHz (at close range to the drillship). 

Source levels recorded for the vessel were 190 dB re 1 μPa (rms) during maintenance work and 

184 dB re 1 μPa (rms) during drilling (Kyhn et al., 2011).

It is expected that marine mammals would detect drilling-related noises within a radius of 

audibility. The range of audibility radii is based on the sound source level and local attenuation from 

factors such as water depth and seafloor characteristics. Based on predominantly low-frequency 

sounds produced by drilling, it is expected that jack-up drilling operations would only affect 

mysticetes (Richardson et al., 1995). From Gales (1982), measurements of received levels of the 

low-frequency tones (199 to 127 dB re 1 μPa) were recorded only at near-field measurement 

locations. Based on the 120 dB re 1 μPa (rms) acoustic sub-injurious threshold established by 

NMFS for continuous sounds, potential impacts to cetaceans would be limited to alterations in 

behavior that are limited to exposures close to the platform, and semisubmersible rigs would affect 

all marine mammal species within the 120-dB acoustic radii. For semisubmersible platforms, the 
4-70 Description of the Affected Resources and Impact Analysis

120-dB radius would be 50 m (164 ft) under conditions where spherical spreading applies. In the 

instances where a drillship will be employed (i.e., in deep water where seafloor anchoring is not 

feasible), drilling noise may be expected to attenuate under spherical spreading conditions in most 

circumstances; the 120-dB radius would extend 3.5 km (2.2 mi) from the drillship. In project-specific 

cases where drilling operations are proposed, and the sound source and propagation may be of 

concern, BOEM will consider the acoustic effects from these activities, along with other IPFs specific 

to these activities. It is expected that these sources of noise would elicit alterations of behavior such 

as changes in swimming direction or speed. However, studies indicate that the sensitivity of marine 

mammals to drilling sound varies among and within species (Richardson et al., 1990).

Considering the low number of proposed drilling operations and the continuous nature of 

sounds produced during drilling operations, it is expected that impacts from noise associated with 

drilling operations would be nominal to minor. 

4.2.2.1.6 Vessel Traffic

Marine mammals may be vulnerable to physical disturbance from or collisions (ship strike) 

with moving vessels (Laist et al., 2001; Douglas et al., 2008; Pace, 2011). Most reports of collisions 

involve large whales, but collisions with smaller species have been reported as well (van Waerebeek 

et al., 2007). Laist et al. (2001) provided records of the vessel types associated with collisions with 

whales. These include (in descending order) tanker/cargo vessels, whale watch vessels, passenger 

liners, ferries, Naval vessels, recreational vessels, USCG vessels, fishing vessels, research vessels, 

dredges, and pilot boats. From these records, most severe and lethal whale injuries involved large 

ships of lengths >80 m (262 ft). Vessel speed was found to be a significant factor as well, with 

89 percent of the records involving vessels moving at 14 kn (16 mph) or greater.

Marine mammals at risk in the GOM for possible ship strikes include slow-moving species 

and deep-diving species while on the surface (e.g., Bryde’s whales, sperm whales, pygmy/dwarf 

sperm whales, and beaked whales). However, certain fast-moving cetacean species, including 

several delphinids such as the bottlenose dolphin and Stenella spp., actively approach vessels to 

swim within the pressure wave produced by the vessel’s bow and are at lower risk of possible ship 

strike. Only four confirmed large whale ship strikes have been reported in the GOM (Cole and 

Henry, 2015; Laist et al., 2001; Jensen and Silber, 2004; Glass et al., 2009).

Vessels directly associated with survey operations included in Alternative A will travel at 

relatively slow speeds during active surveys. Seismic vessels, which account for most of the projectrelated vessel traffic associated with Alternative A activities, survey at a speed of approximately 

4.5 kn (5.2 mph). In addition, waters surrounding survey vessels while on survey would be visually 

monitored (during daylight hours) by PSOs for the presence of marine mammals. During transit to 

and from shore bases, seismic vessels and other G&G survey vessels are expected to travel at 

greater speeds (generally <10 to 12 kn [12 to 14 mph]). Support vessels associated with the 

proposed activities travel at faster speeds, which may have higher potential for collisions with marine 

mammals; support vessels are estimated to include up to 19,689 vessel trips over the 10-year time 
Gulf of Mexico G&G Activities Programmatic EIS 4-71

period (Table 3.4-2). All authorizations for shipboard surveys would include guidance for vessel 

strike avoidance (i.e., NTL 2016-BOEM-G01), which incorporates NMFS “Vessel Strike Avoidance 

Measures and Reporting for Mariners” addressing protected species identification, vessel strike 

avoidance, and injured/dead protected species reporting. Furthermore, 33 CFR § 164.46(a) requires 

that vessels be outfitted with an USCG “type-approved” and “properly installed” AIS. The AIS 

provides vessel information, including the vessel’s identity, type, position, course, speed, 

navigational status, and other safety-related information automatically to appropriately equipped 

shore stations, other ships, and aircraft; automatically receives such information from similarly fitted 

ships; monitors and tracks ships; and exchanges data with shore-based facilities (U.S. Dept. of 

Homeland Security, 2015).

In this analysis, the likelihood of a collision between a project-related vessel during surveys 

and a marine mammal within the AOI is considered low because of several factors: preponderance 

of higher speed vessel activity taking place in shelf waters; relatively low vessel speeds once on a 

survey site; the presence of visual observers (including vessel officers and crew) on board survey 

vessels; and adherence to vessel strike avoidance measures (i.e., NTL 2016-BOEM-G01) for all 

vessels operating in the Gulf of Mexico OCS. Under these conditions and with the limited number of 

project-specific support vessel transits (19,689 over the 10-year period, Table 3.2-7), vessel 

collisions with marine mammals are likely to be avoided and impacts would be nominal. 

Furthermore, when considering the level of commercial traffic in the GOM (Tables 3.4-7 through 

3.4-9) and oil and gas traffic (over a million trips in a 10-year period, Table 3.4-2), the proposed 

activities do not contribute considerably to the overall traffic. Interactions between marine mammals 

attracted to project-related vessel traffic are not considered to affect several individuals. However, in 

the unlikely event a collision did occur, it could result in a mortality resulting in a moderate impact; 

therefore, overall, the impacts from vessel traffic would range from nominal to moderate. 

4.2.2.1.7 Aircraft Traffic and Noise

Aircraft traffic and noise would result from remote-sensing surveys (aeromagnetic surveys) 

and helicopter support. BOEM anticipates that one aeromagnetic survey may be conducted in the 

AOI during the time period covered by this Programmatic EIS (Table 3.2 2). The aeromagnetic 

survey would be conducted by fixed-wing aircraft flying at speeds of approximately 135 kn (155 mph)

(Reeves, 2005). Most offshore aeromagnetic surveys are flown at altitudes between 61 and 152 m 

(200 and 500 ft). Line spacing depends on the objectives, but typical grids are 0.5 to 1.0 mi 

(0.8 × 1.6 km) or 1.0 × 1.0 mi (1.6 × 1.6 km). It is expected that a typical aeromagnetic survey may 

require 1 to 3 months to complete.

Helicopter support is necessary during the drilling of COST wells, shallow test wells 

(Chapter 3.3.1.4), and support and service during deep-penetration seismic airgun surveys. 

Helicopter flights will be used to conduct crew changes for larger seismic vessels; the number of 

anticipated transits is provided in Table 3.2-7 and discussed in Chapter 3.3.1.4. Helicopters are a 

potential source of aircraft noise during drilling of COST and shallow test wells. During seismic 

surveys, helicopters are often used for crew shift changes, emergency medical evacuation, and light 
4-72 Description of the Affected Resources and Impact Analysis

re-supply activities as well. Most of the larger survey vessels are equipped with integrated helicopter 

landing pads to facilitate such airborne support, while smaller vessels may use vessel-to-vessel crew 

transfer or may need to return to shore for crew changes and resupply.

Potential IPFs to marine mammals from aircraft include noise and physical (visual) 

disturbances. Noise generated by project-related aircraft that are directly relevant to marine 

mammals include airborne sounds to individuals resting on the sea surface and underwater sounds 

from air-to-water transmission from passing aircraft. Helicopters and fixed-wing aircraft generate 

noise from their engines, airframes, and propellers. The sound sources from both types of aircraft 

are classified as continuous with dominant tones below 500 Hz (Richardson et al., 1995); therefore, 

these sources are within the auditory range of all marine mammals in the GOM (Appendix H). The 

current acoustic threshold established by NMFS for continuous sounds is 120 dB re 1 μPa (rms) for 

sub-injurious behavioral modification. Richardson et al. (1995) reported received in-water SPLs 

(receiver depths between 3 and 18 m [9.8 and 59 ft]) from aircraft flying at altitudes of 152 m (500 ft) 

were 109 dB re 1 μPa for a helicopter (Bell 212) and 101 dB re 1 μPa for a small, fixed-wing aircraft 

(B-N Islander). Generally, helicopters are approximately 10 dB louder than fixed-wing aircraft of 

similar size (Richardson et al., 1995). Penetration of aircraft noise into the water is greatest directly 

below the aircraft; at angles >13° from the vertical, much of the sound is reflected and does not

penetrate into the water (Richardson et al., 1995). The duration of underwater sound from passing 

aircraft is much shorter in water than air; for example, a helicopter passing at an altitude of 152 m 

(500 ft) that is audible in air for 4 minutes may be detectable underwater for only 38 seconds at 3 m 

(10 ft) depth and for 11 seconds at 18 m (59 ft) depth (Richardson et al., 1995). Levels of noise 

received underwater from passing aircraft depend on the aircraft’s altitude, the aspect (direction and 

angle) of the aircraft relative to the receiver, receiver depth, water depth, and seafloor type 

(Richardson et al., 1995). Received level diminishes with increasing receiver depth when an aircraft 

is directly overhead, but it may be stronger at mid-water than at shallow depths when an aircraft is 

not directly overhead (Richardson et al., 1995). Because of the relatively high expected airspeed 

(135 kn; 155 mph) and these physical variables, aircraft-related noise (including both airborne and 

underwater noise) is expected to be very brief in duration.

The physical presence of low-flying aircraft can disturb marine mammals, particularly 

individuals resting on the sea surface. Observations made from low-altitude aerial surveys report 

behavioral responses of marine mammals are highly variable and range from no observable reaction 

to diving or rapid changes in swimming speed or direction (Efroymson et al., 2001; Smultea et al., 

2008).

Only one aeromagnetic survey and drilling of one COST and two shallow test wells are

associated with Alternative A. Seismic survey crew changes and other service runs are assumed in 

this analysis to be relatively infrequent (estimated every 5 weeks), and the locations for these visits 

are variable based on survey design. Aircraft noise SPLs are moderate at the sea surface and 

underwater based on the relative distance of the sound sources (operational altitudes) and the short 

duration of potential exposure (operational airspeeds). It is expected that impacts from aircraft traffic 
Gulf of Mexico G&G Activities Programmatic EIS 4-73

will be slight or not measureable and limited to only to temporary behavioral disruptions. Potential 

impacts from this activity are expected to be nominal. 

4.2.2.1.8 Trash and Debris

Marine debris (here termed trash and debris) is defined as any persistent solid material that 

is manufactured or processed and directly or indirectly, intentionally or unintentionally disposed of or 

abandoned into the marine environment (USDOC, NOAA, 2015b). Trash and debris relative to G&G 

activities is described in Chapter 3.3.1.7. Survey operations generate trash made of paper, plastic, 

wood, glass, and metal that could be accidentally lost overboard.

Impacts to marine mammals from trash and debris include entanglement and ingestion. 

Although not all G&G activity related, derelict nets, ropes, line, or other fishing gear; packing bands; 

rubber bands; balloon string; six-pack rings; and a variety of other debris can become entangled with 

marine life, including marine mammals. Global entanglement records with trash and debris for 

marine mammals show that entanglement is most common in pinnipeds, less common in mysticetes, 

and rare among odontocetes (Laist et al., 1999). Entanglement data for mysticetes may reflect a 

high interaction rate with active fishing gear rather than with discarded trash and debris (Laist, 1996). 

Entanglement records for odontocetes that are not clearly related to bycatch in active fisheries are 

almost absent (Laist, 1996).

Marine mammals have been known to ingest trash and debris. Debris items may be 

mistaken for food and ingested, or the debris item may have been ingested accidentally with other 

food. Debris ingestion can lead to loss of nutrition, internal injury, intestinal blockage, starvation, and 

even death (USDOC, NOAA, 2015b). However, records suggest that entanglement is a far more 

likely cause of mortality to marine mammals than ingestion related interactions (Laist et al., 1999).

The MARPOL is the main international convention covering prevention of pollution of the 

marine environment by ships from operational or accidental causes. The MARPOL includes 

regulations aimed at preventing and minimizing pollution from ships (accidental and that from routine 

operations) and currently includes six technical Annexes. Special areas with strict controls on 

operational discharges are included in most Annexes. Annex V (“Prevention of Pollution by Garbage 

from Ships”) deals with different types of trash and debris, specifying the distances from land and the 

manner in which they may be disposed of; the most important feature of Annex V is the complete 

ban imposed on the disposal into the sea of all forms of plastics. The revised Annex V prohibits the 

discharge of all trash and debris into the sea, except as provided otherwise. All other trash and 

debris must be returned to shore for proper disposal with municipal and solid waste.

The G&G survey operations associated with Alternative A will generate trash made of paper, 

plastic, wood, glass, and metal that may be accidentally lost overboard. In addition to adherence to 

revised provisions of MARPOL Annex V, USCG and USEPA regulations require operators to 

become proactive in avoiding accidental loss of solid waste items by developing waste management 

plans, posting informational placards, manifesting trash sent to shore, and using special precautions 
4-74 Description of the Affected Resources and Impact Analysis

such as covering outside trash bins to prevent accidental loss of solid waste. Under the proposed 

action, all authorizations for offshore G&G activities would include guidance for the handling and 

disposal of trash and debris as required in NTL 2015-BSEE-G03 and as described in Appendix B. 

Taking into account the USCG and USEPA regulations, as well as BSEE guidance, it is 

unlikely that significant amounts of trash and debris from G&G activities would be released into the 

marine environment. For example in 2012, 889,200 lb of debris was recovered along 1,373 mi 

(2,210 km) of GOM coastline (Ocean Conservancy’s International Coastal Cleanup, 2012). 

Therefore, debris entanglement and ingestion impacts on marine mammals are expected to be 

nominal. 

4.2.2.1.9 Entanglement

Entanglement that may impact marine mammals within the AOI as a result of the proposed 

action include placement of anchors, nodes, cables, sensors, or other equipment on or in the 

seafloor for various activities included in the three program areas. Acoustic buoy releases, tethered 

acoustic pingers, and nodal tethering lines pose an entanglement risk to marine mammals and other 

marine life (i.e., sea turtles). Entanglement has occurred in the past with OBC/OBN surveys and 

other activities where rope tethers were used (e.g., anchors and buoys), which are discussed in 

Chapter 3.3.1.8 and Appendix F, Section 1.1.3. The deployment of nodes and cables is 

accomplished by an ROV, by dropping nodes on a tether, or by laying cables off the back of a layout 

boat. There was one recent (2014) report of a fatal marine mammal entanglement incident during a 

nodal seismic survey in the GOM.

There is a risk of entanglement any time gear, particularly lines and cables, is put in the 

water. Authorizations for surveys that use nodes and cables would include guidance for 

implementing the following best management practices: (1) shortening the acoustic buoy line and 

tethered acoustic pinger line to the shortest length practical using only a single line rather than a 

loop; (2) replacing the line with wire, clasps, or shackles to connect directly to the OBN; 

(3) maximizing the tension on acoustic buoy release lines; and (4) minimizing the time between 

release of the acoustic buoy and retrieval. Additional measures include the requirement of a PSO 

on-board each vessel during tethered node retrieval operations. The PSOs will document any 

entanglement of marine species in the nodal gear, specifically noting the location where 

entanglement occurred (e.g., pinger tether and acoustic buoy line). The PSO will contact NMFS to 

report the incident and condition of the marine mammal and will request additional instructions to 

reduce risk of injury or mortality, including rehabilitation and salvage techniques. 

The OBC/OBN (nodal) survey locations and projected levels are not estimated (they are 

included in the modeling for 3D surveys); however, nodal surveys are relatively uncommon and are 

typically used in shallow waters. Given the scope and limited spatial extent of nodal surveys 

associated with Alternative A (only one documented entanglement incident) and the implementation 

of mitigation measures specific for nodal and cable G&G surveys implemented to minimize the 
Gulf of Mexico G&G Activities Programmatic EIS 4-75

potential for marine mammal entanglement (described above), impacts to marine mammals from 

entanglement during cable/nodal surveys are expected to be nominal. 

4.2.2.1.10 Routine Activities Impact Conclusions

This analysis considered the significance criteria, the AOI, and the 10-year timeframe. As 

outlined in Chapter 2.1 and detailed in Appendix B, mitigation measures that are associated with 

Alternative A that may reduce impacts to marine mammals include the following: 

• guidance for vessel strike avoidance;

• guidance for marine debris awareness;

• avoidance of sensitive benthic resources;

• guidance for shallow hazards survey and reporting;

• guidance for activities in or near NMSs; 

• guidance for avoidance of historic and prehistoric sites; 

• guidance for military coordination;

• guidance for ancillary activities (oil and gas program only);

• implementation of PSO program (oil and gas program only); and

• implementation of the Seismic Airgun Survey Protocol.

As discussed above in routine activities, the degree to which proposed mitigation measures 

(collectively) will affect or change the levels of impact to marine mammals from each is presented 

below:

• deep-penetration airgun survey noise – moderate; 

• HRG airgun survey noise – minor; 

• non-airgun HRG electromechanical survey noise – minor; 

• vessel and equipment noise – nominal to minor; 

• vessel traffic – nominal – moderate; 

• aircraft traffic and noise – nominal; 

• trash and debris – nominal; and

• entanglement – nominal. 

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1. 
4-76 Description of the Affected Resources and Impact Analysis

Implementation of mitigation measures described under Alternative A may reduce potential 

impacts from the IPFs listed above to individuals and groups of marine mammals within the AOI. 

Impact ratings by IPF were determined using impact significance criteria discussed in Chapter 4.2.2, 

and each impact level was determined by considering effects to marine mammals within the AOI 

collectively.

4.2.2.2 Impacts of Accidental Events

This analysis considered an accidental release of 1.2 to 7.1 bbl of diesel fuel caused by a 

vessel collision or an accident during fuel transfer. As discussed in Chapter 3.3.2, diesel fuel spilled 

at the ocean surface would readily disperse and weather. Diesel fuel is most often a light, refined 

petroleum product that is classified by the American Petroleum Institute (API) as a Group 1 class of 

oil based on its specific gravity and density, and is not persistent within the marine environment 

(Biliardo and Mureddu, 2005).

When spilled on water, diesel oil spreads very quickly to a thin sheen, except for marine 

diesel, which may form a thicker film of dull or dark colors. Because diesel oil is much lighter than 

water (specific gravity is between 0.83 and 0.88, compared with 1.03 for seawater), it is not possible 

for the oil to sink and accumulate on the seafloor as pooled or free oil unless adsorption occurs with 

sediment. However, it is possible for the diesel oil that is dispersed by wave action to form droplets 

that are small enough be kept in suspension and moved by the currents (USDOC, NOAA, 2015c). 

As the diesel spreads on the sea surface, the lighter components of the oil begin to evaporate. 

Evaporation rate increases in conditions of high winds, sea state, and atmospheric and sea surface 

temperatures (API, 1999; Biliardo and Mureddu, 2005; USDOC, NOAA, 2015c). Small diesel spills 

(11.9 to 119 bbl) usually evaporate and disperse naturally within a day (USDOC, NOAA, 2015c).

Marine mammals could be affected by spilled diesel fuel. Effects of spilled oil on marine 

mammals are discussed by Geraci and St. Aubin (1980, 1982, 1985, and 1990) as well as Lee and 

Anderson (2005) and within spill-specific study results (e.g., Exxon Valdez; Frost and Lowry, 1994; 

Paine et al., 1996; Hoover-Miller et al., 2001; Peterson et al., 2003). Quantities of diesel fuel on the 

sea surface may directly affect marine mammals through various pathways: surface contact of the 

fuel with skin and mucous membranes of eyes and mouth; inhalation of concentrated petroleum 

vapors; or ingestion of the fuel (direct ingestion or by the ingestion of oiled prey).

As discussed in Chapter 3.3.2.1, the likelihood of a fuel spill during G&G activities is 

considered remote (Chapter 3.3.2), and the potential for contact with and impacts to marine 

mammals would depend heavily on the size and location of the spill, as well as weather and sea 

conditions at the time of the spill. For this scenario, it is assumed that fuel spilled on the sea surface 

would rapidly spread to a thin layer and break into narrow bands or windrows that are aligned in 

parallel with the wind direction. Lighter volatile components of the fuel would evaporate to the 

atmosphere almost completely in a few days. It is assumed that the accidental spill of fuel would 

occur during a vessel collision or during fuel transfer operations. Seismic support vessels usually 

transfer fuel to the survey vessel at slow speed or while stopped, so it is reasonable to assume that 
Gulf of Mexico G&G Activities Programmatic EIS 4-77

groups of marine mammals, such as dolphins, would not be attracted to these vessels during fueling 

operations because of their relative slow speeds.

Because of the thickness of the slick and rapid weathering, it is not likely that many individual 

animals would come into contact with the fuel on the surface. Potential impacts are assumed to be 

limited to minor mucous membrane irritation and behavioral alteration (temporary displacement) 

from the affected area. The spilled fuel, therefore, is expected to result in nominal to minor impacts 

to marine mammals within the AOI, depending on the numbers of individuals coming into contact 

with the spilled fuel and their exposure time as well as the exposure of federally listed species to the 

spilled fuel.

4.2.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for marine mammals are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI.

There is potential for impacts from routine activities or accidental events to be greater on 

individuals or populations already impacted by other OCS oil- and gas-related or non-OCS oil- and 

gas-related impact-producing factors. However, within the GOM, there is a long-standing and welldeveloped OCS Program (more than 50 years) and there are no data to suggest that activities from 

the previous OCS Program are significantly impacting marine mammal populations.

4.2.2.3.1 Noise

Primary sources of noise associated with the cumulative scenario that may impact marine 

mammals include active acoustic sound sources, vessel and equipment, and aircraft. Each source 

is discussed in separate sections below.

Active Acoustic Sound Sources

All G&G survey activities associated with all three program areas (i.e., oil and gas, 

renewable energy, and marine mineral) are included in the proposed action; therefore, G&G 

activities are not included in the cumulative analysis but instead are addressed in the proposed 

action impact analysis (Chapter 4.2.2.1). Cumulative impacts are assessed in this analysis for the 

cumulative activities that produce active acoustic sound sources, including State waters’ oil and gas, 

commercial fishing, cable installation, military, and scientific research activities (Table 3.4-1). 

Certain oil- and gas-, renewable energy-, and marine mineral-related activities such as drilling noise, 
4-78 Description of the Affected Resources and Impact Analysis

trenching noise, pile-driving, and decommissioning are discussed below under vessel and 

equipment noise because they are not active acoustic sounds, but rather related to equipment.

From the analysis provided in Chapter 4.2.2.1, it is expected that surveys using active sound 

sources would contribute to ambient acoustic noise levels in the northern Gulf of Mexico OCS on a 

transient and intermittent basis over the 10-year period. No deaths to marine mammals from active 

acoustic sound source impacts are predicted for this analysis. It is assumed that impacts may 

include PTS auditory injuries, as well as TSS effects, auditory masking, and short-term disruption of 

behavioral patterns or displacement of individual marine mammals from localized areas within the 

AOI. Although G&G activities are spatially limited to selected survey areas, some large surveys may 

take months to complete.

Proposed OCS Program G&G activities utilizing active acoustic sound sources are predicted 

for both continental shelf and deepwater regions; however, activities will be highest within deepwater 

environments of the CPA and WPA (Figure 3.4-1). Projected levels of oil and gas program activities 

in the EPA are very small (Table 3.2-1). Other survey activities, such as marine mineral- and 

renewable energy-related surveys are projected to occur on the continental shelf in shallower 

waters.

Oil and gas activities in State waters would produce active acoustic sounds in shelf waters, 

whereas scientific research, military activities, and commercial fishing activities (using sonar) could 

contribute active acoustic sound throughout the AOI. In addition, within the southern GOM, beyond 

the U.S. EEZ (and beyond the boundaries of the AOI), Mexico exploration and development 

activities occur within several fields offshore Campeche, Tabasco, and Tampico (Index Mundi, 2015; 

USDOI, GS, 2015); these activities would also contribute active acoustic sound sources . It is not 

expected that activities in the cumulative scenario would overlap spatially with the proposed G&G 

activities; however, temporal overlap may occur.

The level of proposed activities represent an incrementally significant addition to similar 

activities within the GOM, especially within deepwater environments of the CPA and WPA. Airgun 

noise from activities may, in some cases, propagate into State waters and would combine with 

activities occurring in State waters. Due to distance, it is assumed that the intensity of active 

acoustic source sounds associated with the proposed activity entering State waters will be 

significantly attenuated from source levels, and the effects to marine mammals will range from no 

observable effect to some behavioral disturbances. The contribution of proposed noise associated 

with deep-penetration, shallow-penetration airgun and non-airgun HRG survey activities to current 

conditions under the cumulative scenario will result in a moderate incremental increase in active 

acoustic noise.

Vessel and Equipment Noise

Cumulative activities associated with vessel and equipment noise are listed in Table 3.4-1. 

Vessel traffic is a major contributor to ambient noise levels within the GOM, particularly in the low-
Gulf of Mexico G&G Activities Programmatic EIS 4-79

frequency bands (Snyder, 2007). Vessel noise is contributed by all of the cumulative scenario 

activities (Table 3.4-1). As discussed in Chapter 4.2.2.1, noise from vessel traffic is generated from 

vessel propulsion systems and internal machinery (the latter also termed equipment noise) and is 

the dominant source of underwater noise at frequencies below 300 Hz in many areas. Table 3.2-7

provides the number of estimated vessels required by survey type and by program area for the 

proposed action, which includes 19,689 trips for support vessels and 1,008 for survey vessels. For 

cumulative vessel traffic, Table 3.4-2 provides a summary of projected support vessel operations 

anticipated for the oil and gas program, and estimates that support vessel trips will range from 

828,000 to 1,096,000 for the 10-year span of the cumulative scenario. Tables 3.4-7 and 3.4-8

provide vessel trip data for all vessels in the GOM. Exact numbers of cumulative vessel traffic 

associated with renewable energy- and marine mineral-related support activities are not known, but 

they are expected to be relatively small and spatially and temporally limited. Oil and gas program 

support vessel traffic projected in the cumulative scenario is expected to be most concentrated 

within the WPA and CPA, as would the proposed action vessel traffic. Vessel traffic within the AOI is 

expected to be somewhat concentrated in lanes and channels near major service centers such as 

Port Fourchon, Louisiana; Port of Morgan City and Port of Iberia, Louisiana; and Port of Galveston, 

Texas (Figure 3.4-1) (Jayawardana and Hochstein, 2004).

Generally, vessels produce underwater noise (originating from vessel propulsion machinery, 

hull movement through the water, and other machinery), and potential impacts to marine mammals 

are expected but are not extensive or severe. Impacts may include disruption of communication or 

echolocation from auditory masking; behavior disruptions of individual or localized groups of marine 

mammals; and limited, localized, and short-term displacement of individuals of any species, 

including strategic stocks, from localized areas around the vessels and equipment. Further, noise 

from vessels may add to existing ambient level conditions, including natural and human-produced 

sources (e.g., seismic airguns, shipping), and these effects may result in a greater cumulative impact 

on affected animals. Further, noise from vessels may add to existing ambient level conditions, 

including natural and human-produced sources (e.g., seismic airguns, shipping), and these effects 

may result in a greater cumulative impact on affected animals.

Historically, support vessel traffic associated with oil and gas activities within State waters 

and the OCS originated from several ports inshore of the CPA and WPA. Consequently, noise 

associated with vessel traffic primarily affected shelf species such as the bottlenose dolphin, Atlantic 

spotted dolphin, and manatees (individuals that travelled from Florida into central and western GOM 

State waters during warmer weather months). Currently, noise-related impacts from oil and gas 

activities in State waters and other activities in coastal waters are largely limited to these species. 

As oil and gas exploration and development moved into deepwater environments in the 1960s, 

exposure to and impacts from noise affected a much larger suite of shelf edge and oceanic species. 

Today, oil and gas service activities for deepwater oil and gas operations have been centralized at 

Port Fourchon, Louisiana, which services approximately 90 percent of all deepwater rigs and 

platforms in the GOM; therefore, a large percentage of supply, service, and construction vessel 

traffic associated with oil and gas activities utilizes this port and travels through various shipping 
4-80 Description of the Affected Resources and Impact Analysis

lanes that funnel into the port. Consequently, noise produced by these vessels is concentrated 

within this area.

Waterborne commerce in the GOM relies heavily on the regional ports for the import and 

export of both foreign and domestic goods. A survey conducted in 2009 ranked 13 of the top 

20 U.S. ports, by tonnage, in the GOM region (including ports in Mississippi, Louisiana, and Texas) 

(USDOC, NOAA, 2012a). South Louisiana was ranked as the leading port in tonnage in 2009. Also, 

from this survey, three of the top six commercial fishing ports in the U.S. (by pounds) were in the 

GOM region (Louisiana and Mississippi) (USDOC, NOAA, 2012). Spatially, vessel traffic utilizes all 

areas of the GOM, though levels are generally concentrated within shipping channels near major 

ports (Figure 3.4-1). Overall levels of commercial shipping have increased over time, along with 

vessel-related noise. Past research shows that this increase in shipping worldwide has historically 

lead to an increase in ambient noise level of 3-5dB per decade. Military use areas in the GOM are 

shown in Figure 3.4-1. It is assumed that military exercises involving one or several vessels may 

occur within these areas on the continental shelf and deepwater regions; however, specific locations 

and times cannot be projected. Commercial fishing vessel-related noise may affect marine 

mammals in all parts of the GOM (Andrew et al., 2002). Overall, when compared with the combined 

vessel noise within the GOM, a minor incremental increase in vessel traffic from G&G operations 

would be expected.

Sources of equipment noise associated with the cumulative scenario includes drilling and 

production activities, pipeline trenching and placement, decommissioning of offshore structures, piledriving associated with renewable energy installations, dredging noise from marine mineral activities, 

military activities, channel dredging, and coastal restoration activities. Sources of equipment noise 

from the proposed action include drilling noise from a limited number of test wells and noise from DP 

and jack-up vessels (Chapter 3.3.1.2).

Decommissioning under the cumulative scenario, as described in Chapter 3.4.1.2, may 

utilize explosives for removal. These operations are generally undertaken following lease expiration 

if the well or facility is no longer economically viable or if the physical condition of the structure 

becomes unsafe or a navigational hazard. In 2005, MMS (BOEM’s predecessor) prepared a 

Programmatic EA to determine the potential impacts that may result from decommissioning activities 

related to the explosive and nonexplosive severing of seafloor obstructions (i.e., wellheads, 

caissons, casing strings, platforms, mooring devices, etc.) and the subsequent salvage and siteclearance operations that may be employed (USDOI, MMS, 2005). Impact mitigation measures for 

these activities were refined from previous regulations such as 67 FR 49869. From this analysis it 

was determined that impacts to marine mammals from underwater detonations associated with 

proposed decommissioning activities may injure marine mammals. With specific mitigation 

measures in place, no deaths or serious injuries were projected, and the Programmatic EA resulted 

in a Finding of No Significant Impact (FONSI). The 2005 Programmatic EA is in the process of being 

updated by BOEM and will serve as the basis for a new Bureau of Safety and Environmental 

Enforcement MMPA petition to NMFS and will support new rulemaking for decommissioning 

activities.
Gulf of Mexico G&G Activities Programmatic EIS 4-81

The contribution of decommissioning of offshore structures using explosive severance 

methods to noise in the GOM is projected under the cumulative scenario in Table 3.4-2. From the 

distribution of active platforms within the AOI, most occur on the continental shelf within the CPA and 

WPA. Consequently, noise associated with explosive removal activities may affect primarily shelf 

species such as the bottlenose dolphin and Atlantic spotted dolphin. Temporally, most operators 

conduct removal projects from June to December (USDOI, MMS, 2005).

Underwater noise associated impacts to marine mammals from offshore drilling operations 

are summarized in Chapter 4.2.2.1. Drilling noise includes strong tonal components at low 

frequencies and infrasonic frequencies in at least some cases (Richardson et al., 1995; USDOI, 

MMS, 2000). Other sources of drilling-related sounds include for example, riser rotation, DP 

thrusters, and ROV operations. Production wells are drilled using MODUs, and the type of 

production platform installed will depend on the water depth and other factors, and may be fixed, 

floating, or subsea (only in deep water). As discussed in Chapter 4.2.2.1, noise levels from drilling 

operations vary with the type of drilling rig and the water depth. Drilling-related noises anticipated 

during the time period of this Programmatic EIS include the completion of one possible COST well 

and up to two shallow test wells in the AOI, using jack-up rigs or semisubmersible rigs (in deepwater 

areas). Based on this level of activity, noise from drilling operations associated with the proposed 

action will contribute a nominal incremental increase, however relatively small and minor, compared 

with ongoing drilling operations in the OCS (and State waters).

Other activities included within the cumulative scenario that generate equipment noise 

include dredging and pile-driving operations. Dredging is projected during dredged material disposal 

operations (Chapter 3.4.3.4), maintenance dredging operations (Chapter 3.4.3.8), coastal 

restoration programs (Chapter 3.4.3.9), Mississippi River hydromodification and subsidence 

operations (Chapter 3.4.3.10), renewable energy development (Chapter 3.4.1.5), and marine 

minerals operations (Chapter 3.4.1.6). Figure 3.4-1 shows the spatial distribution of cumulative 

activities, indicating that most of the cumulative activities are concentrated in shallow shelf waters. 

Other similar equipment noise includes plowing, jetting, or trenching operations conducted during the 

installation of new submarine cable systems (Chapter 3.4.3.5). Dredging activities produce strong 

levels of continuous sounds (primarily at low frequencies) in coastal and inner shelf waters. Due to 

the rapid attenuation of low-frequency sound in shallow water, dredge noise is usually undetectable 

at ranges beyond 20 to 25 km (12 to 16 mi) from the source (Richardson et al., 1995). Dredging 

activities within the northern GOM have occurred for decades.

Pile driving activities are also likely to occur, including during renewable energy development 

activities under the cumulative scenario (Chapter 3.4.1.5). Underwater pile-driving operations 

produces extremely high sound levels in the surrounding air and underwater environments that are 

known to produce deleterious effects on both fish and marine mammals (Reinhall and Dahl, 2011; 

Madsen et al. 2006).

Overall, the minimal level of equipment noise associated with the proposed action (i.e., 

drilling noise from a limited number of test wells, noise from DP and jack-up vessels) would produce 
4-82 Description of the Affected Resources and Impact Analysis

a nominal incremental increase in equipment noise impacts to marine mammals under the 

cumulative scenario.

Aircraft Noise

Aircraft noise in the cumulative scenario is associated with oil and gas exploration and 

development on the OCS and in State waters, military operations, and scientific research (Table 

3.4-1). The use of rotary-winged aircraft (helicopters) for offshore oil and gas support operations (as 

an alternate personnel transportation option) began in the 1950s (American Oil and Gas Historical 

Society, 2015). Today, helicopters are regularly used for operations within State waters and OCS 

waters for a wide variety of tasks.

Impacts to marine mammals from fixed-wing and rotary-wing (helicopter) aircraft traffic and 

noise associated with the proposed action is described in Chapter 4.2.2.1. Under the proposed 

action, possibly one aeromagnetic survey using fixed-wing aircraft is projected. Projections for 

helicopter operations supporting G&G activities within the AOI over the 10-year project period are 

estimated to be a minimum of 7,497 transits (Table 3.2-7). The cumulative scenario estimates that 

7,178,000 to 13,901,000 helicopter trips would occur over the 10-year period (Table 3.4-2) to 

support oil and gas activities. There are no helicopter operations expected for renewable energy or 

marine minerals because G&G activities would occur close to shore and it is expected that only daily 

trips would occur.

The contribution of total helicopter support operations for G&G surveys anticipated over the 

10-year project period (7,497 round-trips) represents 0.1 percent of the minimum projected 

(7,178,000) for the 10-year cumulative scenario. For the proposed action, helicopter flights are 

primarily associated with the installation of the estimated one COST well installation, with airborne 

and marine gravity surveys, and for crew changes during extended deep-penetration seismic airgun 

surveys.

Aeromagnetic surveys are conducted at speeds of approximately 135 kn (155 mph) and at 

altitudes between 61 and 152 m (200 and 500 ft). Typical operational altitudes for helicopters in the 

GOM are higher than 229 m (750 ft), except when the aircraft are within the vicinity of platforms. 

Levels of noise received underwater from passing aircraft depend on the aircraft’s altitude, the 

aspect (direction and angle) of the aircraft relative to the receiver, receiver depth, water depth, and 

seafloor type (Richardson et al., 1995). Because of the relatively high expected airspeeds and these 

physical variables, aircraft-related noise (including airborne and underwater noise) is expected to be 

very brief in duration (i.e., few seconds in duration) at any given point. Although projected levels of 

aircraft noise from G&G operations under the proposed action would increase existing aircraft noise 

levels within the AOI, it is expected that this increase would produce a nominal incremental increase 

in impact to marine mammals under the cumulative scenario.
Gulf of Mexico G&G Activities Programmatic EIS 4-83

4.2.2.3.2 Vessel and Aircraft Traffic

Vessel traffic is an IPF associated with all components of the cumulative scenario and is 

included in the proposed action. Aircraft traffic (physical presence) may disturb groups of marine 

mammals on or near the sea surface; noise impacts are discussed above. The G&G survey and

support vessel traffic associated with the proposed action under Alternative A is discussed in 

Chapter 3.3.1.3. 

As discussed above, vessel and aircraft traffic associated with oil and gas program activities 

will originate from selected ports in the CPA and WPA, and will cross State waters to reach fields 

within the OCS. This discussion of vessel traffic draws from the discussion on vessel noise above, 

with respect to projected and historical oil and gas program vessel traffic levels and other cumulative

vessel traffic levels. As discussed in Chapter 4.2.2.1, underway vessels could collide with marine 

mammals, particularly individuals that rest on the sea surface between dives. In addition, the 

physical presence of these vessels and aircraft may disturb individuals or groups of marine 

mammals on or near the sea surface.

Table 3.2-7 provides the number of estimated vessels required by survey type and by 

program area for the proposed action, and it includes 19,689 trips for support vessels and 1,008 trips 

for survey vessels for cumulative vessel traffic. Table 3.4-2 provides a summary of projected 

support vessel operations anticipated for the oil and gas program and estimates that support vessel 

trips will range from 828,000 to 1,096,000 trips for the 10-year span of the cumulative scenario. 

Tables 3.4-7 and 3.4-8 provide vessel trip data for all vessels in the GOM. Exact numbers of 

cumulative vessel traffic associated with renewable energy- and marine mineral-related support 

activities are expected to be relatively small and spatially and temporally limited, mostly during 

construction or dredging activities, respectively. Other sources of vessels associated with the 

cumulative scenario include those associated with oil and gas activities in State waters, drilling and 

production activities (within both State and OCS waters), commercial shipping, commercial and 

recreational fishing, military activities, scientific research, offshore construction activities, 

maintenance dredging of Federal channels and dredged material disposal, coastal restoration 

programs, and Mississippi River hydromodification and subsidence issues (Table 3.4-1). Vessel 

traffic associated with oil and gas activities in State waters was not available for this analysis. NonOCS Program vessel traffic traveling through the GOM is diverse in vessel type and high in 

numbers. Available information on commercial vessel traffic (which passes through State waters) 

from MARAD (Table 3.4-7) estimated approximately 27,000 calls in Gulf Coast State ports during 

2012. In addition, there were an estimated 309,000 vessel trips recorded by vessels equipped with 

AIS during 2012 (Table 3.4-8). There were also approximately 410 to 540 cruise ships departing 

GOM ports between 2008 and 2011 (Table 3.4-9). The G&G vessel traffic associated with the 

proposed action is expected to be most concentrated within the WPA and CPA. As vessels pass 

through State waters, they are expected to be somewhat concentrated in (although not limited to) 

lanes and channels near major oil and gas service centers such as Port Fourchon, Port of Morgan 

City, Port of Iberia, and Port of Galveston. Because of the wide distribution of projected vessel 

activities within the AOI and State waters, it is likely that individuals from all species of marine 
4-84 Description of the Affected Resources and Impact Analysis

mammals within the northern GOM may encounter vessel traffic during the 10-year project period. 

Overall, when compared with cumulative vessel traffic in the GOM, the contribution of G&G vessel 

traffic to the cumulative scenario is minor.

The physical presence of low-flying aircraft can disturb marine mammals, particularly 

individuals resting on the sea surface. Fixed-wing and rotary-wing (helicopter) aircraft traffic and 

noise associated with Alternative A are described in Chapter 4.2.2.1. For the proposed action, 

helicopter flights are primarily associated with the installation of the estimated one COST well, with 

airborne and marine gravity surveys, and for crew change outs during extended deep-penetration 

seismic airgun surveys. However, as described above, the helicopter traffic contributed by the 

proposed action represents 0.1 percent of the cumulative vessel traffic over the 10-year time period. 

All of these operations will originate from heliports along the coast. Other aircraft traffic over the 

GOM associated with the cumulative scenario includes helicopters associated with oil and gas 

operations within State waters, survey aircraft in near coastal waters, military aircraft, and scientific 

research (Table 3.4-1). Estimates of the exact numbers of these aircraft traffic were not available for 

this analysis; however, it is expected that oil and gas contribute the majority of helicopter traffic in the 

cumulative scenario (7 to 13 million trips over the 10-year period). Helicopter traffic associated with 

oil and gas operations in the GOM have historically been concentrated along the continental shelf of 

the CPA and WPA. 

In all cases, it is assumed that helicopters will ascend to service altitudes after takeoff from 

coastal facilities and maintain altitudes over water until their destination is reached. Typical 

operational altitudes for helicopters in the GOM are higher than 229 m (750 ft), except when the 

aircraft are within the vicinity of platforms. Consequently, it is likely that their transits over State and 

OCS waters will only infrequently disturb marine mammals.

It is not anticipated that these aircraft would affect large numbers of marine mammals and 

that all interactions would be short term. Projected levels of helicopter traffic from G&G operations 

under the proposed action would increase existing traffic levels within the AOI. These activities 

would be concentrated within deepwater areas of the CPA and, to a lesser degree the WPA, 

because projected G&G activities requiring helicopters (i.e., deep-penetration surveys) are highest 

there (Table 3.2-1). Although projected levels of aircraft traffic from G&G operations under the 

proposed action would increase existing aircraft traffic levels within the AOI, it is expected that this 

increase would produce a nominal incremental increase in impact to marine mammals under the 

cumulative scenario.

4.2.2.3.3 Trash and Debris

Trash and debris (Chapter 3.3.1.7) is defined as any persistent solid material that is 

manufactured or processed and directly or indirectly, intentionally or unintentionally disposed of or 

abandoned into the marine environment (USDOC, NOAA, 2015b). Derelict nets, ropes, line, or other 

fishing gear; packing bands; rubber bands; balloon string; six-pack rings; and a variety of other 

debris can become entangled with marine life, including marine mammals. Marine mammals have 
Gulf of Mexico G&G Activities Programmatic EIS 4-85

also been known to ingest trash and debris. The G&G survey operations associated with the 

proposed action will generate trash made of paper, plastic, wood, glass, and metal that could be 

accidentally lost overboard. In addition to adherence to revised provisions of MARPOL Annex V, 

survey operations will adhere to USCG and USEPA regulations by developing waste management 

plans, posting informational placards, manifesting trash sent to shore, and using special precautions 

such as covering outside trash bins to prevent accidental loss of solid waste. Under the proposed 

action, all new authorizations for offshore G&G activities would include guidance for the handling 

and disposal of trash and debris (NTL 2015-BSEE-G03).

Trash and debris may originate from diverse activities, both onshore and offshore. All 

mariners’ operating vessels in the GOM are expected to comply with MARPOL 73/78 for 

management of waste in inland, coastal, and offshore waters. Therefore, trash and debris that may 

be discarded offshore would be only accidental and minimal in volume. However, trash and debris 

may also originate from areas outside of the U.S. and drift into the AOI via local currents. Prior to 

the development of MARPOL guidelines, as well as USCG and USEPA regulations, it is probable 

that the volume of trash and debris deliberately discarded into coastal and offshore waters was 

significant. Overall, discarded trash and debris generated by the proposed action would result in a 

nominal incremental increase in impact to marine mammals under the cumulative scenario.

4.2.2.3.4 Entanglement

Offshore seismic surveys associated with the proposed activity that involve placement of 

acoustic buoy releases, tethered acoustic pingers, and nodal tethering lines pose an entanglement 

risk to marine mammals and other marine resources. Preventative measures to reduce or remove 

the probability of entanglement of marine mammals in these equipment types are discussed BOEM’s 

2013 Site-Specific Environmental Assessment for G&G Surveys (USDOI, BOEM, 2013e). Activities 

associated with the cumulative scenario that may deploy equipment that may pose entanglement 

risks to marine mammals within the AOI include State waters’ oil and gas activities, commercial and 

recreational fishing, and scientific research. Sources of entanglement include anchors, cables, 

sensors, fishing gear, or other equipment moored or tethered to the seafloor either permanently or 

temporarily, as well as any type of line extending from the surface or subsurface to the seafloor. 

Given the use of the preventative measures, combined with number of G&G activities in the AOI that 

involve deployment of line tethered to the seafloor, the incremental increase in the cumulative 

impacts to marine mammals from seafloor disturbance (i.e., entanglement in lines) during G&G 

activities are reasonably expected to result in a nominal incremental increase in impacts to marine 

mammals.

4.2.2.3.5 Cumulative Impact Conclusions

Based on the non-Federal impacts discussed in this chapter, the existing baseline 

conditions, and the proposed actions, BOEM has determined that the cumulative effects of all of 

these potential impacts to marine mammals are not greatly exacerbated by the proposed action. 

This determination is justified because the impacts are spread out both temporally and spatially in a 

manner that makes it extremely unlikely that marine mammals will be exposed to multiple stressors 
4-86 Description of the Affected Resources and Impact Analysis

simultaneously or sequentially in a manner that would reduce their individual fitness, survival, 

reproductive success, or in a manner that would result in an appreciable change in population 

growth rates.

Proposed activities associated with the proposed action would increase levels of noise and 

vessel and aircraft traffic within the AOI, resulting in sporadic increases in ambient noise levels 

during proposed G&G operations. Noise levels of some operations could exceed Level A and 

Level B harassment thresholds resulting in PTS, TTS, or behavioral changes in marine mammals. 

Sources of noise associated with the cumulative scenario that may affect marine mammals of the 

AOI include active acoustic sound, vessel and equipment, and aircraft. Other IPFs that may affect 

marine mammals include vessel and aircraft traffic, trash and debris, entanglement, and accidental 

fuel spills. Many of these IPFs may occur simultaneously during some projected operations under 

the OCS Program. For example, during deep-penetration seismic airgun, shallow-penetration 

seismic airgun, and non-airgun HRG survey operations, IPFs such active acoustic sound, vessel and 

equipment noise, vessel traffic, and aircraft noise and traffic (during some survey activities) will occur 

together. Entanglement of marine mammals in ocean bottom cable/nodal surveys and the release of 

trash and debris or fuel into offshore waters are not routine and, therefore, represent accidental 

occurrences during the 10-year project period.

The spatial distribution of activities projected under the proposed action during the project 

period are most concentrated within deepwater regions of the CPA and WPA and are less 

concentrated within continental shelf waters (Table 3.2-1). Very little activity is projected to occur 

within the EPA. Temporally, activity levels associated with the proposed action vary by activity type 

and year (Tables 3.2-1 through 3.2-5). From this analysis, impacts to marine mammals from 

proposed routine activities include moderate impacts (from active acoustic sound associated with 

deep-penetration seismic airgun surveys), minor impacts (from active acoustic sound associated 

with shallow-penetration airgun and non-airgun HRG surveys, and vessel and equipment noise), and 

nominal (from vessel, equipment, and aircraft noise; vessel and aircraft traffic; trash and debris; and 

entanglement).

The contribution of active acoustic sound proposed under the proposed action to ambient 

noise levels in the GOM is moderate, specifically within the CPA and WPA. Because these 

operations may occur within both continental shelf and slope waters, it is probable that individuals 

from all cetacean species that occur within the AOI may be affected by proposed operations during 

the 10-year project period. The contribution of project-related vessel and aircraft noise and traffic to 

current environment of the GOM is nominal in all planning areas based on current levels of similar 

(non-OCS) sources, such as oil and gas activities in State waters and waters of the southern GOM, 

and commercial shipping, commercial and recreational fishing, and military activities throughout the 

GOM. Although operations associated with the OCS Program are limited to waters of the OCS, 

there are some IPFs that may also occur within adjacent State waters. For example, survey vessels 

and aircraft will transit through State waters while travelling to and from coastal ports and heliports, 

and related IPFs (noise and physical presence issues) may impact marine mammals within these 

waters. In addition, if projected OCS surveys occur near the State water boundaries, it is possible 
Gulf of Mexico G&G Activities Programmatic EIS 4-87

that noise from active acoustic sound sources (primarily deep-penetration seismic airguns) may 

travel into State waters and impact individual or groups of marine mammals.

Based on the assumption that all operators engaged in OCS Program activities will adhere to 

current regulations and guidelines regarding the disposal of wastes in the marine environment 

(Chapter 4.2.2.1), potential impacts to marine mammals from entanglement and the release of trash 

and debris during proposed OCS operations is nominal, and the contribution of this IPF to ambient 

conditions in the GOM is nominal. Impacts to marine mammals from a potential accidental fuel spill, 

described in Alternative A, are described in Chapter 4.2.2.3 as nominal to minor, based on the type 

(diesel fuel) and volume (small spill classification) of the spill. No information was provided on the 

location of the spill or season when the spill may occur. It was assumed that the spill would occur 

within open ocean conditions of the OCS. Although individuals from all cetacean species that occur 

within the AOI may encounter the spilled fuel, it was assumed that the fuel would rapidly spread and 

weather and impacts are nominal to minor. The contribution of impacts from this projected spill to 

ambient conditions within the GOM is nominal.

When compared with historic levels of activities within the GOM, proposed activities do not 

represent a significant incremental increase to activities under the cumulative scenario. Surveys 

utilizing active acoustic sound sources have occurred within the GOM for decades, including within 

State waters and continental shelf and deepwater regions of the OCS. Commercial, military, and 

recreational vessel traffic has also occurred in the GOM, including the AOI for many years. In some 

cases, such as large commercial vessels, traffic is and has been more concentrated along Gulfwide 

shipping lanes that funnel into major coastal ports. Commercial and recreational fishing vessels 

have utilized broad areas of the northern GOM, but primarily on the continental shelf and shelf edge. 

It is assumed that military vessels have traveled through all areas of the GOM, though it is assumed 

that most, if not all, exercises have occurred within the U.S. Navy GOMEX Range Complex 

OPAREAs, including Panama City, Pensacola, New Orleans, and Corpus Christi (Atlantic Fleet 

Training and Testing [AFTT], 2015). Vessel traffic associated with the proposed activity will occur. 

The projected fuel spill associated with the proposed activity is relatively small and impacts to marine 

mammals are nominal to minor. When compared with historic spill events, the contribution of this 

projected spill is nominal.

In conclusion, activities associated with Alternative A are more concentrated within 

deepwater regions of the CPA and WPA and less concentrated on the continental shelf of these 

planning areas. In addition, projected levels of activities will vary over the 10-year project period. 

When compared with historic, present, and future activities, including similar non-OCS Program 

activities (Figure 3.4-1), the cumulative effects of all IPFs to marine mammals within the AOI over 

the 10-year period would result in nominal to minor incremental increases in impacts.

4.2.2.3.6 Accidental Fuel Spills

An accidental fuel spill scenario was evaluated for Alternative A and consisted of the release 

of 1.2 to 7.1 bbl of diesel fuel from a vessel collision or spillage during at-sea fuel transfer operations 
4-88 Description of the Affected Resources and Impact Analysis

(Chapter 3.3.2.1). This volume of spilled fuel is considered a “small diesel spill” by the NOAA Office 

of Response and Restoration (USDOC, NOAA, 2015c), and characteristics of this type of spill are 

described in Chapter 3.3.2.1. The likelihood of a fuel spill occurring during G&G surveys or 

activities was considered remote (Chapter 4.2.2.3). Collisions between vessels transiting within 

both State and OCS waters could result in the overboard loss of fuel. However, it is improbable that 

an accidental fuel spill would occur within State waters; rather, operations involving vessel transfers, 

including fuel transfers, would occur on the OCS. However, spilled fuel could drift into State waters. 

The OCS Program activities projected for the period of interest are outlined in Chapter 3.4.1. Based 

on historical records and excluding the Deepwater Horizon explosion, oil spill and response, OCSrelated offshore oils spills are anticipated to be a release of 2,200 bbl, but they have a low probability 

of occurring (USDOI, BOEM, 2012).

The incremental increase of a 1.2- to 7.1-bbl fuel spill as reasonably foreseeable as a result 

of the proposed action to the cumulative scenario is expected to be nominal. Potential to marine 

mammals of the AOI are expected to remain nominal to minor, depending on the numbers of 

individuals coming into contact with the spilled fuel and their exposure time. These impacts may 

affect individuals within OCS and State waters, depending on the location of the spill and local 

surface circulation patterns.

4.2.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.2.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative B on marine mammals. Additional mitigation measures 

include seasonal restriction in Federal coastal waters of the GOM, which would temporarily minimize 

the potential for impacts from active acoustic sources, vessel equipment, and aircraft noise and 

vessel traffic on individual members of the BSE stocks during their calving season, as well as 

coastal stocks of bottlenose dolphins, Atlantic spotted dolphins, and individual manatees that may 

occur in Federal coastal and inshore waters.

4.2.3.1 Impacts of Routine Activities 

4.2.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to April 30)

Alternative B includes a seasonal restriction in Federal coastal waters of the GOM shoreward 

of the 20-m (65-ft) isobath between January 1 and April 30 (Figure 2.2-1 [Area 3]) as defined in the 

Settlement of the Areas of Concern (Chapter 1.1.4). No airgun surveys would be authorized within 

the closure area during this time. This coastal seasonal restriction is designed to protect northern 

Gulf of Mexico BSE stocks of the common bottlenose dolphin during the time of their reproductive 

activity peak, as well as some coastal stocks of bottlenose dolphins (Appendix E, Section 2). The 

31 BSE stocks are listed in Table 4.2 2, and their relative distributions along the Gulf Coast are 

shown in Figure 4.2-4. All of the bays, estuaries, and sounds that support these stocks along the 

Gulf Coast have been designated as Biologically Important Areas (BIA). The BIAs are defined as 

reproductive areas, feeding areas, migratory corridors, and areas in which small and resident 
Gulf of Mexico G&G Activities Programmatic EIS 4-89

populations are concentrated (Ferguson et al., 2015). Residency patterns of BSE dolphins in the 

GOM range from transient to seasonally migratory to stable resident communities (LaBrecque et al., 

2015). Only the BSE dolphins are known to have small and resident populations that fulfill BIA 

criteria. In addition, areas in Louisiana, Mississippi, Alabama, and the western Florida Panhandle 

have been impacted by a UME of unprecedented size and duration (began February 1, 2010, and 

closed May 26, 2016) (USDOC, NMFS, 2016b).

The seasonal restriction on airgun surveys in Federal coastal waters under Alternative B 

would temporarily minimize the potential for impacts from active acoustic sound sources, vessel, 

equipment, and aircraft noise, and vessel traffic on individual members of the BSE stocks during 

their calving season as well as coastal stocks of bottlenose dolphins, Atlantic spotted dolphins, and 

individual manatees that may occur in Federal coastal and inshore waters (embayments and 

estuaries). Geological surveys and non-airgun HRG surveys would still be permitted or authorized 

within the seasonal restriction area from January 1 to April 30. Thus, this seasonal restriction 

mitigation measure would not alter the effects from non-airgun HRG or geological surveys, trash and 

debris, or entanglement that are reasonably foreseeable under Alternative; therefore, these IPFs are 

not repeated in this chapter, and the impact analysis for these IPFs are incorporated by reference 

from Alternative A.

The seasonal restriction of Federal coastal waters to seismic airgun surveys between 

January 1 and April 30 would reduce potential auditory impacts to individual dolphins, manatees, 

and any other potentially occurring marine mammals within these waters. Between January 1 and 

April 30, it is likely that the distribution of manatees within the AOI will be largely restricted to inshore 

coastal (State) waters of peninsular Florida. Overall, the auditory impacts on coastal marine 

mammals on an annual basis in the seasonal restricted area of the AOI is unlikely to be significantly 

affected by the implementation of this mitigation measure, as the overall number of airgun surveys 

annually will not be reduced in coastal waters and, thus, the associated auditory impact level on 

each species would not be reduced. The key positive and important benefit associated with this 

mitigation measure is the removal of a level of environmental stress during a biologically critical 

period when many coastal common bottlenose dolphins are reproducing (calving). This protection of 

their reproductive (calving) environment provides fitness level consequences to both individuals and 

populations of the potentially occurring coastal species, resulting in the probability for increased 

success in reproduction and survival of each species.

Although this measure would not affect individuals outside of the coastal area, it would 

provide a degree of protection to all marine mammals that may occur within the restricted area from 

January 1 and April 30 and increases the fitness values of the reproducing species (i.e., common 

bottlenose dolphins, manatees, and Atlantic spotted dolphins), which promotes the survival and 

reproductive success of the populations as a whole. Therefore, this measure will not reduce the 

overall impact level discussed in Alternative A (moderate) for all marine mammals in the AOI from 

seismic airgun activities.
4-90 Description of the Affected Resources and Impact Analysis

This seasonal restriction for Federal coastal waters under Alternative B would not only 

reduce the number of airgun surveys in the seasonal coastal restriction area but also would reduce 

project-related seismic survey vessel traffic and associated vessel and equipment noise in these 

restricted coastal areas between January 1 and April 30. To provide an idea of the benefit of 

implementing this mitigation measure under Alternative B and attempt to bound how much survey 

activity might be reduced, the following very broad-scale but quantitative assessment is provided. 

Over a 10-year period, a 2 month per year restriction of no airgun surveys would result in 20 months 

or 1.6 years of no airgun surveys in these coastal closure waters. Over the 10-year period 

considered in this Programmatic EIS, that would mean 18 fewer airgun surveys would occur in the 

seasonal restriction closure area or 51,231 line miles less that would not be surveyed by airgun 

surveys. This is determined by considering that 891 airgun surveys would take place in the entire 

AOI area over 10 years (Table 3.2-8); over 1.6 years, 142.6 airgun surveys would take place over 

the entire AOI. Considering that the seasonal coastal closure area represents 12.88 percent of the 

total areal extent of the AOI, the percentage of airgun surveys that would take place in the seasonal 

closure area, assuming equal survey coverage over the AOI, would be 18 surveys. In terms of line 

miles that would not be surveyed in the seasonal coastal closure area, of the 2,485,992 line miles of 

total airgun surveys over 10 years, 397,758.7 line miles would normally occur over 1.6 years. The 

seasonal closure area represents 12.88 percent or 51,231.3 line miles that would not be surveyed in 

the seasonal closure area. It is understood that survey distribution across the AOI is not, however, 

uniform, especially in coastal waters. As discussed in Alternative A (Chapter 4.2.2.1), impacts of 

vessel traffic and vessel noise on marine mammals are expected to be nominal to moderate (and 

at the moderate end of the range, if a collision occurred) and nominal to minor, respectively. This 

mitigation measure would effectively remove potential vessel disturbance and possible vessel strike 

of marine mammals within the restricted area between January 1 and April 30. While 

implementation of this mitigation measure may reduce the impacts of vessel disturbance and 

possible vessel strikes to potentially occurring localized marine mammals in Federal coastal waters, 

the overall potential impacts to marine mammals in the AOI from vessel traffic and noise are 

expected to remain unchanged from Alternative A determinations because the overall reduction in 

the number of surveys or line miles surveyed during the period of seasonal restriction are not 

sufficient to reduce the overall impact levels to all marine mammal species in the AOI. Vessels 

associated with proposed activities are relatively few in number, are transient within the AOI, and 

travel at relatively slow speeds. Although it is likely that individual marine mammals within Federal 

coastal waters of the AOI have previously been exposed to the sounds and physical presence of 

recreational and commercial vessel traffic (including oil and gas support vessels), particularly in 

shipping lanes and near populated areas, it is yet unknown as to whether these prior exposures 

have or have not resulted in animals being less affected (or reactive) to these sound sources.

The additional seasonal restriction for Federal coastal waters under Alternative B would not 

affect scheduling of the potential aeromagnetic survey or the drilling of two shallow test wells and a 

COST well within the AOI. Support helicopters used for seismic airgun surveys; however, would 

only transit at operational altitudes in these areas between January 1 and April 30. Typical 

operational altitudes for helicopters in the GOM are as follows:
Gulf of Mexico G&G Activities Programmatic EIS 4-91

• field operations (i.e., within the vicinity of platforms) – 500 ft or lower; and

• en route operations

− eastbound: 750 ft, 1,750 ft, and 2,750 ft; and

− westbound: 1,250 ft and 2,250 ft (Farley, 2015).

As in the case of vessel traffic, it is likely that individual marine mammals within Federal 

coastal waters of the AOI have previously been exposed to the sound and physical presence of 

fixed-wing aircraft and helicopter traffic within the AOI, particularly over inner shelf and coastal 

waters. However, as with vessel traffic and noise, it is yet unknown as to whether these prior 

exposures have or have not resulted in animals being less affected (or reactive) to these sound 

sources. It is expected that the impacts to marine mammals from aircraft traffic and noise would 

remain unchanged from those detailed already for Alternative A and would be nominal with the 

time-area closure under Alternative B.

4.2.3.1.2 Expanded PSO Program 

The expansion of the PSO Program under Alternative B will include the same mitigation for 

manatees as provided for specific whale species (Bryde’s, beaked, sperm, or dwarf and pygmy 

sperm whales) and will apply to all deep-penetration seismic airgun surveys in the GOM regardless 

of water depth (Chapter 2; Appendix B, Section 1.3.2). All airguns will be shut down any time a 

whale (Bryde’s, beaked, sperm, or dwarf and pygmy sperm whales) or manatee is detected entering 

or within the established exclusion zone, and, as it is in Alternative A, ramp-up of airguns and 

recommencement of seismic activities may occur only when the exclusion zone has been visually 

inspected for at least 30 minutes to ensure the absence of all marine mammals and sea turtles.

The implementation of this expanded PSO Program under Alternative B would reduce the 

potential for impacts to marine mammals and sea turtles from exposure to active acoustic sound 

sources within the AOI because this preventative measure would then apply to all deep-penetration 

seismic airgun surveys regardless of water depth, increasing the protection provided should whale 

species (Bryde’s, beaked, sperm, or dwarf and pygmy sperm whales) or manatees be detected in 

the exclusion zone, resulting in a shutdown of the seismic source and reducing exposure of those 

animals within the exclusion zone. It is expected that inclusion of the expanded PSO Program would 

provide protection for the whale species (Bryde’s, beaked, sperm, or dwarf and pygmy sperm 

whales) and manatees that these measures are designed to protect in addition to the other regularly 

occurring GOM marine mammal species. Continued implementation of this exclusion zone 

shutdown measure will likely reduce the localized impacts to all potentially occurring marine mammal 

species, including whale species as defined (Bryde’s, beaked, sperm, or dwarf and pygmy sperm 

whales) or manatees, from exposure to the deep-penetration seismic airgun surveys. The potential 

for impacts to manatees from exposure to airgun noise would largely be limited to operations 

conducted in shallower continental shelf or nearshore waters where this species is most likely to 

occur. Adherence to protocols specified in the expanded PSO Program (Appendix B, Section

1.3.2) would likely reduce localized acoustic impacts (primarily behavioral disturbances) to those 
4-92 Description of the Affected Resources and Impact Analysis

manatees potentially occurring only in the survey area. However, while likely providing localized 

reduction in sound exposure and associated impacts, those reductions in exposure are not sufficient 

to alter the overall impacts to marine mammals, including whales (Bryde’s, beaked, sperm, or dwarf 

and pygmy sperm whales) and manatees, throughout the entire AOI from exposure to deeppenetration seismic airgun surveys, and thus, the impact level would not change from that of 

Alternative A (moderate). Implementation of this mitigation measure is not relevant to other IPFs 

such as vessel and equipment noise, aircraft traffic and noise, trash and debris, and entanglement, 

and thus will not influence potential effects associated with those IPFs; thus, these IPFs will not be 

discussed further in this chapter. 

4.2.3.1.3 Minimum Separation Distances

Under Alternative B, when operating in the Areas of Concern (Figure 2.2-1 [Areas 1 

through 4]), simultaneous deep-penetration seismic airgun surveys (separate surveys) must 

maintain a separation distance of 40 km (25 mi) between active sound sources (airgun arrays). 

When outside the Areas of Concern, the separation distance will be 30 km (19 mi). This separation 

requirement does not apply to multiple ships operating in a coordinated survey such as a WAZ 

survey and need not be maintained if unsafe or due to weather conditions.

This measure was designed to mitigate possible effects of multiple man-made underwater 

sounds from multiple seismic operations on marine mammals, including the effects of interacting and 

repeated sounds. This mitigation measure; however, will not affect potential impacts from other IPFs 

such as fixed-wing aircraft noise (during aeromagnetic surveys), drilling noise, trash and debris, and 

entanglement, as discussed in Alternative A (Chapter 4.2.2.1). These IPFs are not discussed 

further in this chapter. 

The separation distance between surveys may be modified based on newly available 

information and in consideration of any other surveys requested or authorized to operate 

concurrently. For example, new information suggests that, in some circumstances, airgun noise can 

be detected at great distances from the sound source, such as across ocean basins (Nieukirk et al., 

2012), yet it is unknown if detection of sound at these distances has any effect on marine species. 

Therefore, BOEM will consider the value of this approach at the site-specific NEPA and 

environmental analysis level, and with review of new information. The subsequent evaluations also 

will consider any potential aggregate effects from existing permitted surveys.

BOEM concludes that there is incomplete or unavailable information (40 CFR § 1502.22) for 

all marine mammals with respect to: the hearing range, the basic biology of specific species and 

their physiology for underwater hearing, and the effects of noise. All of these species-specific and 

population variables may be relevant to reasonably foreseeable adverse impacts on marine 

mammals that are subject to active acoustic sound sources, i.e., airguns. However, what is known 

about the biology and hearing physiology of representative species, in combination with 

observations of behavioral response to stimuli, allows inferences and conclusions about reasonably 

foreseeable adverse impacts on marine mammals to be understood with an adequate degree of 
Gulf of Mexico G&G Activities Programmatic EIS 4-93

certainty. BOEM has therefore determined that the data or information on marine mammal biology, 

hearing physiology, seasonal abundances, and population stock in the AOI identified as incomplete 

or unavailable is not essential to a reasoned choice among the alternatives, including the No Action 

alternative.

Moreover, a more complete knowledge base for all types of marine mammals that use the 

AOI and that bear on the factors listed above is not available and the acquisition of such information 

cannot be acquired without exorbitant cost. Such information certainly cannot be acquired in a 

timeframe to make it available for this evaluation. While there will never be complete scientific 

information on marine mammals that live in OCS waters, a body of biological and physiological data 

and information about the underwater hearing of representative marine mammals is available to us. 

These data are sufficient to draw inferences and conclusions about the types of marine mammals 

that are less well understood. Thus, while BOEM reports where limited data and insufficient 

knowledge challenge our ability to understand how and when specific types of marine mammal 

species use the AOI and how that bears on the factors listed above, incomplete or unavailable 

information does not affect our ability to understand and assign impacts or design mitigation 

strategies. BOEM is able to draw basic conclusions despite incomplete or unavailable information, 

discuss results using available scientifically credible information, and apply that information using 

accepted scientific methodologies.

Implementing minimum separation distances between concurrent seismic airgun surveys 

under Alternative B could change the timing of these surveys in certain areas. The specific 

geographic locations cannot be predicted in advance and would depend on the schedule, planned 

coverage of individual surveys, and ports to be used for support activities. Under this Alternative B 

and execution of survey separation distances in certain areas (e.g., Areas of Concern), possible 

localized decreases in impacts to potentially occurring marine mammals may result as exposure to 

sound levels are minimized. However, as detailed in Chapter 2.13.2, the efficacy of this mitigation 

measure is not certain due to the complexity of how sound propagates in varying environmental 

conditions. As discussed under Alternative A (Chapter 4.2.2.1), impacts to marine mammals in the 

AOI from airgun sound sources used in deep-penetration seismic airgun surveys are estimated to be 

moderate, and this impact level for all marine mammals within the AOI are expected to remain 

unchanged by implementation of this mitigation measure under Alternative B.

Impacts from vessel traffic and the associated vessel and equipment noise are expected to 

range from nominal to moderate (if a collision occurred) and nominal to minor, respectively. 

Limits, such as maintaining minimum separating distances, on concurrent seismic airgun surveys 

within the Areas of Concern or other areas or changes in survey timing due to these imposed limits 

would not alter the overall impacts from active acoustic sound sources, vessel traffic, vessel and 

equipment noise, or aircraft traffic and noise on marine mammals in the AOI under Alternative B 

because the effects of this mitigation measure are of limited geographic scope and would not affect 

all marine mammals throughout the AOI.
4-94 Description of the Affected Resources and Impact Analysis

4.2.3.1.4 Seismic Restrictions in the Areas of Concern within the EPA

Additional restrictions under Alternative B include the year-round prohibition of deeppenetration seismic airgun surveys within the portion of the Areas of Concern falling within the EPA

(Figure 2.2-1 [portions of Areas 2 and 3, and all of Area 4]), due to the biological importance of 

these waters to certain species of marine animals (such as Bryde’s whales). This restriction does 

not apply to currently leased blocks, any portion of the area encompassed by EPA Lease Sale 226, 

or neighboring OCS lease blocks adjacent to permitted survey areas but within an otherwise off-limit 

area selected areas of concern. This measure may affect potential impacts to marine mammals 

from deep-penetration seismic airgun surveys as well as survey-related vessel and aircraft noise. 

This mitigation measure will not affect ratings of impacts from other IPFs such as HRG airgun and 

electromechanical sound source surveys (minor), fixed-wing aircraft noise (during aeromagnetic 

surveys) (nominal to minor), drilling noise (minor), trash and debris (nominal), and entanglement 

(nominal) as discussed in Alternative A (Chapter 4.2.2), as the year-round prohibition only applies 

to deep-penetration seismic airgun surveys. Because the HRG airgun, electromechanical sound, 

and aeromagnetic surveys would still occur unabated and because this mitigation measure would 

not affect the amount of drilling noise or trash/debris produced in the AOI, there could be no effect 

from this mitigation measure in the EPA to the impacts from other IPFs. For this reason, these IPFs 

are not discussed further in this chapter. 

The restriction of seismic airgun surveys within Area of Concern 2 may afford additional 

protection to the small population of geographically and genetically distinct Bryde’s whales in the 

GOM (Rosel and Wilcox, 2014), as their exposure to sound-producing impact factors will be 

lessened. However, indirect impacts of sound from surveys in adjacent areas traveling into Area of 

Concern 2 may still affect Bryde’s whales and their associated prey to a degree. As discussed in 

Appendix E, Bryde’s whales found in the northern GOM represent a resident stock that is under 

consideration for ESA listing. The waters offshore of western Florida and the Florida Panhandle 

shoreward of the 20-m (65-ft) isobath (Settlement Area of Concern 3) provide diverse shallow-water 

habitats for multiple resources such as marine mammals, sea turtles, fishes, and sensitive benthic 

habitats. This seasonal restriction area will provide protection not only to numerous BIAs, but it also 

affords protection directly for the potentially occurring BSE stocks of bottlenose dolphins, individual 

coastal stocks bottlenose dolphins and Atlantic spotted dolphins, and manatees in these waters.

Area of Concern 4 is an area west of the Florida Keys and Tortugas, defined as limited to the 

area bounded by the 200-m (656-ft) isobath to the north, the 24° N. latitude line to the south, the 

83°30' W. longitude to the west, and the 81°30' W. longitude line to the east (Figure 2.2-1). It is 

understood that beaked whale and sperm whale numbers may be very dense in this area; and 

therefore, protection will be afforded to those species located within the Area of Concern 4.

Seismic survey restrictions under Alternative B may provide additional protection to 

potentially occurring marine mammals within these restricted areas from the IPFs associated with 

deep-penetration seismic airgun surveys. One of the positive effects of this mitigation measure, 

reduced exposure to potentially impactful sound fields, would be significant for Bryde’s whales in the 
Gulf of Mexico G&G Activities Programmatic EIS 4-95

AOI (Area of Concern 2), individual marine mammals that move through the inner shelf waters within 

the coastal closure area (particularly manatees and individuals from coastal and BSE stocks of 

bottlenose dolphins), and individual beaked whales and sperm whales within Area of Concern 4, in 

addition to all other regionally occurring marine mammals. These designated closure areas 

represent key important habitats for the designated species or stock. Although deep-penetration 

seismic airgun surveys may still occur outside of these closure areas and therefore expose 

individuals occurring outside of these areas, the implementation of these closures would likely afford 

important protections to key habitat areas and biological behaviors (e.g., calving grounds). It is, 

therefore, anticipated that overall impacts to marine mammals at the stock level from the IPFs 

associated with active acoustic sources (deep-penetration seismic airgun surveys) would be reduced 

from the impacts listed in Alternative A (moderate). Additionally, although there are restrictions for 

deep-penetration seismic airgun surveys in the Areas of Concern waters of the EPA, other types of 

surveys may occur in these waters where Bryde’s whales reside, meaning that Bryde’s whales may 

still be exposed to other active acoustic source transmissions. These restrictions in Area of 

Concern 2 may reduce potential impacts for the Bryde’s whale, as it is assumed that the restrictions 

in this area would prevent or reduce injurious (Level A) and behavioral or TTS (Level B) harassment 

associated with exposure to deep-penetration seismic sources.

4.2.3.1.5 Use of PAM Required

Alternative B specifies the required use of PAM for all seismic surveys occurring during 

periods of reduced visibility, as detailed in Appendix B, Section 1.3.5, in GOM areas with water 

depths >100 m (328 ft) to detect vocalizing marine mammals. This is in contrast to Alternative A, in 

which the use of PAM is optional. The mitigation measure was stipulated to reduce impacts to 

marine mammals from active acoustic sound sources. The use of PAM allows operators to ramp-up 

sound sources and start or resume a seismic survey during times of reduced visibility (e.g., 

darkness, fog, or rain) in water depths >100 m (328 ft) if no marine mammals are detected. The use 

of PAM prior to and during seismic surveys may also assist or improve the detection of vocalizing 

marine mammals within the 180-dB rms (Level A) exclusion zone, particularly under conditions when 

visual monitoring is not possible. During times of reduced visibility, use of PAM is an effective 

protective measure for marine mammals relative to underwater sound IPFs such as active acoustic 

sources because marine mammals are able to be detected even when submerged, as long as the 

animals are vocalizing. Because the overall effect of this measure is that seismic surveys can occur 

at night or other times when visibility is reduced after PAM has indicated no marine mammals are 

present, this measure would have no effect or relevance to IPFs such as aircraft traffic and noise, 

trash and debris, or entanglement; these IPFs are therefore not discussed further in this chapter. 

The required use of PAM under Alternative B may affect the vessel traffic or noise IPF because 

more vessels could be operating at night or during other periods of reduced visibility than would 

otherwise be occurring. Thus, under this measure, the impact on vessel traffic and noise may 

increase in limited areas of the AOI, but the overall impact to marine mammals in the AOI in general 

would be unchanged.
4-96 Description of the Affected Resources and Impact Analysis

An overview of PAM systems may be found in Chapter 2.13.5, as is information about the 

mitigation effectiveness of both acoustic and visual mitigation (Chapter 2.12). Because existing 

PAM systems were not designed specifically for monitoring and mitigation for offshore industrial 

application, no single technical approach has the ability to satisfy all or even most of the marine 

mammal monitoring and mitigation requirements of the offshore industry; therefore, an integrated 

approach is necessary. Additionally, PAM systems are unable to simultaneously listen to all species 

in an area due to the wide range of frequencies of marine mammal vocalizations. The effectiveness 

of PAM depends on the ability to properly identify species specific vocalizations (when those marine 

mammals are vocalizing) in the presence of ambient noise and other noise sources (Ward et al., 

2011). In their overview of PAM techniques, Mellinger et al. (2007) noted that acoustic surveys 

detect 1 to 10 times as many cetacean groups as visual surveys. Although the technology for 

detecting and locating underwater sounds and their sources in general is well developed, hardware 

and software systems using passive acoustics specifically designed to locate and track marine 

mammals as mitigation integrated with seismic airguns are relatively new and have only been 

commercially available since approximately 2011 (Azem et al., 2011).

As discussed in Chapter 4.2.2.1 under Alternative A, potential impacts to marine mammals 

from active acoustic sources is rated as moderate, assuming the possibility of some acoustic injury 

(PTS), but it is in low enough numbers such that the continued viability of the local population or 

stock is not threatened and the annual rates of recruitment or survival of the local population or stock 

are not seriously affected. Although the success of towed PAM as a mitigation tool during seismic 

surveys is proven, studies point out that, because PAM systems only detect marine mammals that 

are vocalizing, PAM is not 100 percent effective at detecting all marine mammals that may enter 

project-specific “acoustic zones of hearing loss, discomfort, or injury” as described in Richardson 

et al. (1995). Consequently, it is possible that some numbers of individuals or groups of cetaceans 

may experience PTS injuries during surveys conducted within the AOI during the project duration as 

PAM may not detect all marine mammals in the localized area. It is also assumed that PAM surveys 

would not prevent temporary behavioral alterations, such as displacement of individuals from areas 

of ensonification. While the use of PAM prior to ramp-up or initiation of seismic surveys during 

reduced visibility periods would decrease impacts to a portion of any potentially occurring marine 

mammals in the surveyed area, not all marine mammals would necessarily be detected. Thus, even 

in a localized area, a decrease in potential impacts associated with exposure to active acoustic 

sources for all potentially occurring marine mammals would not be assured by use of PAM. 

Therefore, protection provided to marine mammals under Alternative B with the required use of PAM 

during periods of reduced visibility would not change the impact on all marine mammals within the 

AOI or alter the overall impact level associated with exposure to airgun sound sources. Therefore, 

the implementation of PAM during seismic surveys within the AOI under Alternative B would reduce 

impacts to marine mammals. However, the use of PAM during seismic surveys will require 

additional monitoring that may lead to additional shutdowns and therefore afford additional 

protections to marine mammals. However, it does not alter the overall impact level from the IPFs 

listed for Alternative A (moderate).
Gulf of Mexico G&G Activities Programmatic EIS 4-97

4.2.3.1.6 Routine Activities Impact Conclusions

Under Alternative B, G&G activities would include implementation of existing mitigation 

requirements discussed under Alternative A, as well as the following mitigation measure 

requirements outlined in the Settlement Agreement for Civil Action No. 2:10-cv-01882 dated 

June 25, 2013 (Appendices B and C; Figure 2.2-1):

• required use of PAM for all seismic surveys occurring during periods of reduced 

visibility in areas with water depths >100 m (328 ft);

• time-area closure for airgun surveys in Federal coastal waters of the GOM 

shoreward of the 20-m (65-ft) isobath between January 1 and April 30; 

• expanded PSO Program to include same mitigation to manatees as provided for 

whales for all water depths;

• a 40-km (25-mi) separation distance between simultaneously operating deeppenetration seismic airgun surveys within designated closure areas (Areas of 

Concern); 

• a 30-km (19-mi) separation distance between simultaneously operating deeppenetration seismic airgun surveys outside of the Areas of Concern

• year-round prohibition of deep-penetration seismic airgun surveys in the portion 

of Areas of Concern falling within the EPA; and 

• implementation of the Seismic Airgun Survey Protocol.

As discussed in Chapter 4.2.3.1, the degree to which these mitigation measures 

(collectively) will affect or change the levels of impact to marine mammals from each project-related 

IPF (including routine activities and accidental events) is presented below:

• deep-penetration airgun survey noise – moderate; 

• HRG airgun survey noise – minor; 

• non-airgun HRG electromechanical survey noise – minor; 

• vessel and equipment noise – nominal to minor; 

• vessel traffic – nominal to moderate; 

• aircraft traffic and noise – nominal; 

• trash and debris – nominal; and

• entanglement – nominal. 

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1. 
4-98 Description of the Affected Resources and Impact Analysis

Overall, the mitigation measures described under Alternative B may reduce potential impacts 

from the IPFs listed above to individuals and groups of marine mammals within the AOI. These 

measures may also significantly reduce impacts from certain IPFs (such as seismic airgun noise) to 

selected management stocks of marine mammals within the GOM (e.g., Bryde’s whale and sperm 

whale). Research is limited as to the extent to which these measures would reduce impacts, but 

these areas are known to have higher aggregations of each of these species. While there may be 

localized benefits from additional mitigation measures, overall impact ratings by IPF for all marine 

mammal species across the AOI over a 10-year period would remain the same as Alternative A.

4.2.3.2 Impacts of Accidental Events

Under Alternative B, impacts of an accidental fuel spill on marine mammals would be very 

similar to those analyzed in Chapter 4.2.2.2 for Alternative A. The analysis concluded that a small 

spill at the sea surface would result in nominal to minor impacts, depending on the numbers of 

individuals adversely affected by the spilled fuel and the exposure of federally listed species to the 

spilled fuel.

Alternative B would change the timing of certain surveys because of time area closures and 

limits on concurrent seismic airgun surveys. Additionally, certain surveys will not be allowed within 

portions of the EPA. Spills from survey and support vessels could occur within areas outside the 

closure period, and spills from other survey type vessels could occur during the closure period or in 

the EPA depending on the frequency of the HRG source used. A change in survey timing or type 

because of limits on concurrent seismic airgun surveys or on survey type would not substantially 

change the risk of a small fuel spill in the long term. Therefore, the risk of a small fuel spill and its 

potential impacts on marine mammals within the AOI would be the same as under Alternative A 

(nominal to minor), depending on the numbers of individuals adversely affected by the spilled fuel.

4.2.3.3 Cumulative Impacts

The G&G activities have been ongoing in the GOM for at least the past 30 years and it is 

reasonable to assume requests to conduct such activities will continue into the future; however, for 

the purpose of this Programmatic EIS, the cumulative analysis assesses a 10-year timeframe to 

coincide with the proposed action because it is expected that most impacts from G&G activities will 

be of short duration and limited to the time period of the active survey and thus not extend beyond 

the 10-year timeframe of this Programmatic EIS.

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for marine mammals are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 
Gulf of Mexico G&G Activities Programmatic EIS 4-99

by IPF and provides a conclusion of the cumulative incremental increase within the AOI. Impact 

analyses presented in Chapters 4.2.3.1 and 4.2.3.2 determined that activities projected to occur 

under Alternative B would result in nominal to moderate impacts to marine mammals, depending 

on the IPF.

Mitigation measures for the proposed action under Alternative B are described in 

Chapter 2.2 and summarized in Chapter 4.2.3.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.2.2.3).

Mitigation measures under Alternative B would not change the extent of most activities in the 

proposed action. Minimum separation distances between concurrent surveys may, however, reduce 

the potential severity of ensonification from multiple seismic survey sound sources within discrete 

areas of the AOI. Areas selected for closure from deep-penetration seismic airgun survey activities 

were designed to focus on mitigation of deep-penetration seismic impacts to a single species or 

select group of species. Mitigation measures under Alternative B that would change the timing and 

extent of activities in the proposed action include a seasonal restriction for operation of airguns in 

Federal coastal waters, which was designed to protect coastal stocks of the bottlenose dolphin 

during their reproductive peak.

The cumulative impact analysis identified nominal to minor contributions in impacts from all 

IPFs under Alternative A compared with the cumulative impact as a whole. Alternative B would 

implement seasonal restrictions for seismic airgun surveys in Federal coastal waters, seismic airgun 

surveys, and exclude certain areas from seismic airgun surveys during the 10-year period of interest. 

These mitigation measures (including additional or revised procedural measures and spatial 

restrictions of seismic airgun activities) would reduce potential impacts to specific species or stock 

within the AOI as it would restrict surveys in biologically important habitat areas for these species or 

stocks (e.g., calving grounds). Although survey activities in all other areas of the AOI (or in areas 

adjacent to the closure areas) may continue to potentially impact individual marine mammals during 

the project period, these closure areas may reduce impacts at key life stages and during critically 

important biological behaviors. When considering all potential auditory impacts to marine mammals 

within the AOI from proposed seismic airgun activities along with established impact significance 

criteria provided in Chapter 4.2.2, these mitigation measures will not appreciably change the levels 

of impacts contributed by Alternative A to all marine mammals within the AOI to the cumulative 

impact as a whole. The comparative contribution of Alternative B would not differ significantly from 

the comparative contribution of Alternative A under the cumulative impact assessment even with the 

additions of the mitigation measures included in Alternative B, though there may be slight reductions 

identifiable in the AOI.

4.2.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.2.2). Additional mitigation measures in Alternative C differ from those in 
4-100 Description of the Affected Resources and Impact Analysis

Alternative B and include different months for seasonal restrictions in Federal coastal waters, 

additional PAM requirements to include PAM operations at night and at all times when in the 

Mississippi and De Soto Canyons, and non-airgun HRG survey protocols. The following discussion 

outlines the effects of the additional mitigation measures included in Alternative C on marine 

mammals.

4.2.4.1 Impacts of Routine Activities

4.2.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to May 31)

Alternative C includes a seasonal restriction for operation of airguns or airgun arrays in 

coastal waters of the entire AOI (20-m [65.6-ft] isobath to shore) from February 1 to May 31. Effects 

of this seasonal restriction mitigation measure for project-related IPFs result in the same overall level 

of potential impact to marine mammals in the AOI, nominal to moderate, as those discussed in 

Chapter 4.2.3.1 for Alternative B.

Seasonal Restriction for Coastal Waters

The Seasonal Restriction for Coastal Waters (Figure 2.6-1) had different effects in the three 

different coastal zones (Zones 1, 2 and 3; Appendix D, Figure 110). The bottlenose dolphin was 

the only species to show decreased density ratio in all three coastal zones. For all other species, in 

Zones 1 and 2, the density ratios were greater than 1.0 (Table 4.2-6), indicating a likely overall 

increase in the exposure estimates (Appendix D) as a result of this seasonal restriction. In Zone 3, 

the closure had varying effects on the other species. The density ratio for the Clymene and spinner 

dolphins decreased the most due to the Seasonal Restriction for Coastal Waters, though since these 

species are not found within coastal waters, their densities are very small under both conditions and 

the difference is not significant. The Atlantic spotted dolphin, false killer whale, Fraser’s dolphin, 

killer whale, and striped dolphin all showed an increased density ratio (Table 4.2-6) indicating a 

likely overall increase in the exposure estimates (Appendix D) as a result of this seasonal 

restriction. The remaining species all exhibited density ratios close to 1, which correlates to little or 

no change from the original density estimate.

4.2.4.1.2 Expanded PSO Program

The expanded PSO Program will apply to manatees as well as whales (Bryde’s, beaked, 

sperm, or dwarf and pygmy sperm whales), requiring all airguns shut down any time a specific whale 

species (Bryde’s, beaked, sperm, or dwarf and pygmy sperm whales) or manatee is detected 

entering or within the exclusion zone in all water depths. Effects of this mitigation measure to marine 

mammals within the AOI for project-related IPFs are the same as those discussed in Chapter

4.2.3.1 for Alternative B, and range from nominal to moderate. 

Under Alternative A, all authorizations for seismic airgun surveys (those involving airguns as 

an acoustic source) in depths >200 m (656 ft) in the WPA and CPA and in all water depths in the 

EPA would include the Seismic Airgun Survey Protocol that specifies mitigation measures for 

protected species including ramp-up requirements, an exclusion zone, shutdown requirements, and 
Gulf of Mexico G&G Activities Programmatic EIS 4-101

visual monitoring by PSOs and PAM. For Alternatives B and C, the required use of PSOs and 

exclusion zone monitoring includes all water depths throughout the GOM. Therefore, this expansion 

would add these protective measures to survey activities conducted within continental shelf waters 

of the GOM.

It is assumed that the implementation of these operational mitigation measures during deeppenetration seismic airgun survey activities would reduce but not eliminate possible auditory 

threshold shift (PTS) injuries of marine mammals because the exposures to impact-producing sound 

would decrease. Similarly, survey mitigation measures are not likely to eliminate or significantly 

reduce behavioral responses, including Level B harassment of marine mammals. Based on the 

uncertainties of the effectiveness of these mitigation measures, particularly during nighttime 

operations and during periods of poor visibility and inclement weather, impacts to marine mammals 

within the AOI from deep-penetration seismic airgun surveys would not change from that detailed for 

Alternative A (moderate).

The expansion of the requirements for use of PSOs and exclusion zone monitoring in all 

water depths throughout the GOM and the already slow speeds of G&G survey vessels may further 

protect marine mammals from vessel collisions due to the increase in visual observer effort. 

However, cetacean species that are regular inhabitants of shelf waters in the GOM include two 

dolphin species (i.e., the common bottlenose dolphin and Atlantic spotted dolphin) that are agile 

swimmers and are known to approach moving and stationary vessels. Manatees may receive some 

additional protection by the added PSO effort, particularly in areas on the shelf. The implementation 

of this mitigation measure under Alternative C would not affect the level of impacts to marine 

mammals within the AOI from vessel collisions as described in Alternative A (nominal to moderate

[if a collision occurred]).

Impacts to marine mammals from aircraft traffic and noise, drilling noise, trash and debris, 

and entanglement would not be affected by the expansion of seismic survey mitigation measures 

and the PSO Program associated with Alternative C, and impacts would remain nominal. 

4.2.4.1.3 Use of PAM Required 

Under Alternative C, the use of PAM is required for seismic surveys occurring at night and 

during periods of reduced visibility in waters deeper than 100 m (328 ft) and required at all times 

when operating in Mississippi and De Soto Canyons. The requirement for PAM surveys within the 

AOI is designed to provide additional means to detect and thus protect diving whale species not 

visible at all times to visual mitigation observers, including endangered sperm whales and Bryde’s 

whales, during seismic survey mitigation protocols. Sperm whales are concentrated in continental 

slope waters of the Mississippi Canyon lease block area while Bryde’s whales principally occur in a 

restricted area of the northeastern GOM between the 100- and 400-m (328- and 1,312-ft) isobaths 

from approximately 87.5° W. longitude to 27.5° N. latitude and from 100- to 300-m (328- and 984-ft)

isobaths farther south to off Tampa, Florida (Maze-Foley and Mullin, 2006; Waring et al., 2013; 

Rosel and Wilcox, 2014) (the middle of “The Elbow” leasing area). Sperm whales are vocally active, 
4-102 Description of the Affected Resources and Impact Analysis

making them easy to detect acoustically, particularly during long dives (Mellinger et al., 2003). Their 

emitted sounds are wideband clicks that usually occur in certain timing patterns (Jaquet et al., 2001), 

are distinctive, and are easily distinguishable and localized as the clicks have a sharp onset and 

offset and so provide good material for determining the time-of-arrival differences used in many 

acoustic localization methods. Bryde’s whales produce low-frequency tonal and swept calls similar 

to the calls of other balaenopterid baleen whales. It is quite likely that towed PAM equipment can 

detect and possibly determine the location of a calling Bryde’s whale (Oleson et al., 2003), but the 

ability of any PAM system to identify a Bryde’s whale is limited by the associated autodetection 

software’s capability to detect and identify the low-frequency signal emitted by a Bryde’s whale and 

potential masking by the low-frequency seismic signals and vessel noise.

As discussed in Chapter 2.13, the use of towed PAM to locate and identify marine mammals 

has some limitations, such as limited directional capabilities, challenges of both sound sources and 

receivers being mobile, short time coverage, limited detection range, and a tendency towards 

masking problems from tow vessel noise, flow noise, and seismic source noise, including airgun 

reverberation in shallow water (Bingham, 2011). While the use of PAM prior to ramp-up or initiation 

of seismic surveys during reduced visibility periods would decrease impacts to a portion of the 

marine mammals potentially occurring in the surveyed area, not all marine mammals would 

necessarily be detected unless they were vocalizing. Thus, even in a localized area, a decrease in 

potential impacts associated with exposure to active acoustic sources for all potentially occurring 

marine mammals would not be assured by use of PAM. While the implementation of PAM during 

seismic surveys within the AOI under Alternative C would not eliminate but will reduce impacts to 

marine mammals, it does require additional monitoring, which may lead to additional shutdowns and 

therefore afford additional protections to marine mammals. While the additional measures afford 

some localized temporal and spacial protections to marine species, it does not alter the overall 

impact level listed for Alternative A over the entire AOI and 10-year time period (moderate). Under 

Alternative C, potential impacts are anticipated to be limited to minor TTS impacts or temporary 

behavioral changes with no expectation of physical (auditory) injuries anticipated. The expansion of 

PAM requirements under Alternative C would not affect potential impacts from other IPFs for marine 

mammals within the AOI. Impact ratings would remain the same as those specified under 

Alternative A and range from nominal to minor. 

4.2.4.1.4 Non-Airgun HRG Survey Protocol

Non-Airgun HRG Survey Protocol mitigation measures included under Alternative C are 

discussed together in this chapter for clarity. Non-airgun HRG surveys in which one or more active 

acoustic sound sources will be operating at frequencies <200 kHz in all water depths throughout the 

AOI will require a pre-survey clearance of all marine mammals (and sea turtles) for a period of 

30 minutes before start-up or after a shutdown for all marine mammals except dolphins. Non-airgun 

HRG surveys using sound sources <200 kHz must use at least one trained PSO to visually monitor a 

200-m (656-ft) exclusion zone during daylight hours. The exclusion zone for HRG surveys would be 

a 200-m (656-ft) radius zone around the sound source. Immediate shut down of the sound source(s) 

would occur if any sperm, Bryde’s, beaked, Kogia whale(s) or manatee(s) are detected entering or 
Gulf of Mexico G&G Activities Programmatic EIS 4-103

within the exclusion zone. Subsequent restart of the equipment may only occur following a 

confirmation that the exclusion zone is clear of all marine mammals and sea turtles for a period of 

30 minutes. It is anticipated that the implementation of these mitigation measures will reduce 

potential acoustic injuries (Level A) and behavioral disturbances to potentially occurring localized 

marine mammals in proximity of the proposed HRG (<200 kHz) surveys. However, while PSO and 

visual monitoring methods are effective, they are only efficacious during daylight and periods of good 

weather and visibility. Thus, while acoustic impacts to potentially occurring localized whale and 

manatee species associated with non-airgun HRG surveys may be reduced by employing PSOs and 

visually surveying prior and during the non-airgun HRG surveys, those possible reductions are only 

possible in optimal sighting conditions (i.e., daylight and good weather). Also, this mitigation 

measure provides no protection for other marine species. Therefore, overall impacts to all marine 

mammals in the AOI associated with exposure to non-airgun HRG sound sources would not change 

significantly from that already presented for Alternative A (minor).

The requirement for visual monitoring surveys by PSOs before and during HRG surveys 

(<200 kHz) under Alternative C would not affect potential impacts from other IPFs such as vessel 

and equipment noise, aircraft traffic and noise, trash and debris, and entanglement from 

Alternative A, and impacts associated with these IPFs as discussed above would range from 

nominal to minor. Visual monitoring by PSOs would provide additional protection to marine 

mammals from collisions with project-related vessel traffic by notifying vessel crew of potential 

collisions in a timely manner. However, survey vessels will be operated at relatively slow speeds, 

and it is unlikely that whales or dolphins will be in danger of collisions. Consequently, the increase in 

detectability provided by PSOs during non-airgun HRG survey activities will not affect the overall 

level of impact to all marine mammals within the AOI from active acoustic sound sources.

4.2.4.1.5 Routine Activities Impact Conclusions

Under Alternative C, G&G activities would include implementation of existing mitigation 

requirements discussed under Alternative A, as well as the additional mitigation measures for all 

seismic airgun and non-airgun HRG surveys. Additional mitigation measures for seismic airgun 

surveys include the following: 

• expanded PSO Program to include same mitigation to manatees as provided for 

whales for all water depths;

• required use of PAM for all seismic surveys occurring during periods of reduced 

visibility in areas with water depths >100 m (328 ft) and at all times within the 

Mississippi Canyon and De Soto Canyon lease blocks;

• time-area closure for airgun surveys in Federal coastal waters of the GOM 

shoreward of the 20-m (65-ft) isobath between February 1 and May 31; and 

• implementation of the Seismic Airgun Survey Protocol.
4-104 Description of the Affected Resources and Impact Analysis

Additional mitigation measures for non-airgun HRG surveys include the following: 

• non-airgun HRG surveys operating at frequencies <200 kHz in all water depths 

throughout the AOI will require a pre-survey clearance of all marine mammals

(and sea turtles) before start-up or after a shutdown; and

• implementation of the Non-Airgun HRG Survey Protocol.

As discussed in Chapter 4.2.4.1, the degree to which these mitigation measures 

(collectively) will affect or change the levels of impact to marine mammals from each project-related 

IPF (including routine activities and accidental events) is presented below:

• deep-penetration airgun survey noise – moderate; 

• HRG airgun survey noise – minor; 

• non-airgun HRG electromechanical survey noise – minor; 

• vessel and equipment noise – nominal to minor; 

• vessel traffic – nominal to moderate; 

• aircraft traffic and noise – nominal; 

• trash and debris – nominal; and

• entanglement – nominal. 

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1. 

Overall, the mitigation measures described under Alternative C may reduce potential impacts 

from the IPFs listed above to individuals and groups of marine mammals within the AOI. The 

additional mitigation measures analyzed in this alternative would provide localized benefits to marine 

mammal species. However, from impact significance criteria discussed in Chapter 4.2.2, overall 

impact ratings by IPF for all marine mammal species across the AOI over a 10-year period would 

remain substantially the same as Alternative A.

4.2.4.2 Impacts of Accidental Events

Under Alternative C, impacts of an accidental fuel spill on marine mammals would be very 

similar to those analyzed in Chapter 4.2.2.2 for Alternative A. The analysis concluded that a small 

spill at the sea surface would result in nominal to minor impacts, depending on the numbers of 

individuals adversely affected by the spilled fuel.
Gulf of Mexico G&G Activities Programmatic EIS 4-105

4.2.4.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for marine mammals are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI. Impact 

analyses presented in Chapters 4.2.4.1 and 4.2.4.2 determined that activities projected to occur 

under Alternative C would result in nominal to moderate impacts to marine mammals, depending 

on the IPF.

Mitigation measures for the proposed action under Alternative C are described in 

Chapter 2.3 and summarized in Chapter 4.2.4.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.2.2.3). As discussed in Chapter 4.2.4.1, 

most mitigation measures under Alternative C would not change the extent, severity, or timing of 

activities in the proposed action; thus, the resultant impacts to marine mammals also would not 

change. Under Alternative C, the mitigation measure that would change the timing and extent of 

activities in the proposed action is a seasonal restriction for operation of airguns in Federal and State 

coastal waters between February 1 and May 31. The implementation of mitigation measures 

outlined in Alternative C (Chapter 2.3.2) would reduce potential auditory impacts from proposed 

activities on individuals or groups of marine mammals within the AOI. Specifically, this mitigation 

measure provides additional protections for coastal stocks of bottlenose dolphins, which are of 

particular concern. However, these measures would not significantly reduce the predicted 

moderate (from Alternative A) impact level for all marine mammals within or outside of the AOI, 

based on impact level criteria (Chapter 4.2.2).

The cumulative impact analysis identified nominal to minor incremental increases in 

impacts from all IPFs discussed under Alternative A. The cumulative scenario would remain similar 

for Alternative C and the associated impacts would likewise be similar. Alternative C would change 

the timing of seismic airgun surveys in certain areas; however, this seasonal restriction and 

operational mitigation measures would not appreciably change the cumulative impacts determined 

under Alternative A.

4.2.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative D are the same as for 

Alternative A (Chapter 4.2.2). Mitigation measures in Alternative D are the same as those 

discussed in Alternative C with the exception of additional shutdowns. The following discussion 

outlines the effects of the additional mitigation measures included in Alternative D on marine 

mammals.
4-106 Description of the Affected Resources and Impact Analysis

4.2.5.1 Impacts of Routine Activities

4.2.5.1.1 Expanded PSO Program with Additional Shutdowns

Seismic survey mitigation measures included in Alternative D are modified from Alternative C 

mitigation measures, which require the use of PSOs and exclusion zone monitoring in all water 

depths throughout the GOM, required use of PAM for all seismic surveys in water depth >100 m 

(328 ft) and at all times in the Mississippi Canyon and De Soto Canyon lease blocks, and seasonal 

coastal restrictions from February 1 to May 31 (Chapter 4.2.4.1). Under Alternative D, sound source 

shutdowns would be required for all marine mammals and sea turtles with the exception of bowriding dolphins (i.e., dolphins bow riding or actively approaching G&G operations). The dolphin 

species in the GOM that bow-ride on the pressure wave of ships include common bottlenose, 

Fraser’s, Risso’s, Clymene, rough-toothed, striped, spinner, Atlantic spotted, and pantropical spotted 

dolphins. Information on the behavioral reactions of bow-riding dolphins is detailed in 

Chapter 4.2.2.1. Visual mitigation with PSOs is implemented for Alternative D, including the 

associated relevant shutdown procedures as detailed previously.

Overall, it is assumed that mitigation measures described in Alternative D, including the 

Seismic Airgun Survey Protocol (Chapter 2.4 and Appendix B, Attachment 1), would reduce the 

extent of, but not prevent, behavioral responses and potential Level B exposure occurring for marine 

mammals within the AOI. While the execution of the Alternative D mitigation measures would likely 

lessen the impacts to localized marine mammals, except bow-riding dolphins, and since additional 

shutdowns may require additional survey time (ultimately avoiding Level A exposure potentially 

occurring with the potential for occurrence of Level B exposure), the overall impacts to marine 

mammals within the AOI associated with deep-penetration seismic airgun sources would not change 

significantly from that already detailed for Alternative A (moderate). The effects on the AOI marine 

mammals due to the addition of shutdown for all marine mammals, except bow-riding dolphins, 

under Alternative D would not affect potential impact levels from other IPFs (non-airgun HRG 

acoustic surveys, vessel and equipment noise, aircraft traffic and noise, trash and debris, and 

entanglement) presented in Alternatives A, B, or C (Chapter 4.2.4), which ranged from nominal to 

minor, or for vessel traffic which ranged from nominal to moderate (if a collision occurred).

4.2.5.1.2 Routine Activities Impact Conclusions

Under Alternative D, G&G activities would include implementation of existing mitigation 

requirements discussed under Alternative C, as well as the following additional mitigation measure 

requirements measures for seismic airgun and non-airgun HRG surveys. Mitigation measures for 

seismic airgun surveys include the following: 

• expanded PSO Program to include same mitigation to manatees as provided for 

whales for all water depths;

• sound source shutdowns for all marine mammals except bow-riding dolphins 

(i.e., bottlenose, Fraser’s Clymene’s, rough-toothed, striped, spinner, Atlantic 

spotted, pantropical, and Risso’s dolphins);
Gulf of Mexico G&G Activities Programmatic EIS 4-107

• required use of PAM for all seismic surveys occurring during periods of reduced 

visibility in areas with water depths >100 m (328 ft) and at all times within the 

Mississippi Canyon and De Soto Canyon lease blocks;

• time-area closure for airgun surveys in Federal coastal waters of the GOM 

shoreward of the 20-m (65-ft) isobath between February 1 and May 31; and 

• implementation of the Seismic Airgun Survey Protocol.

Mitigation measures for non-airgun HRG surveys include the following: 

• non-airgun HRG surveys operating at frequencies >200 kHz in all water depths 

throughout the AOI will require a pre-survey clearance of all marine mammals 

(and sea turtles) before start-up or after a shutdown; and

• implementation of the Non-Airgun HRG Survey Protocol.

As discussed in Chapter 4.2.5.1, the degree to which these mitigation measures 

(collectively) will affect or change the levels of impact to marine mammals from each project-related 

IPF (including routine activities and accidental events) is presented below:

• deep-penetration airgun survey noise – moderate; 

• HRG airgun survey noise – minor; 

• non-airgun HRG electromechanical survey noise – minor; 

• vessel and equipment noise – nominal to minor; 

• vessel traffic – nominal to moderate; 

• aircraft traffic and noise – nominal; 

• trash and debris – nominal; and

• entanglement – nominal. 

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1. 

Overall, the mitigation measures described under Alternative D may reduce potential impacts 

from the IPFs listed above to individuals and groups of marine mammals within the AOI. However, 

from impact significance criteria discussed in Chapter 4.2.2, the overall impact level by IPF for all 

marine mammal species within the AOI would remain the same as Alternative A.
4-108 Description of the Affected Resources and Impact Analysis

4.2.5.2 Impacts of Accidental Events

Under Alternative D, impacts of an accidental fuel spill on marine mammals would be the 

same as those analyzed in Chapter 4.2.2.2 for Alternative A. The analysis concluded that a small 

spill at the sea surface would result in nominal to minor impacts, depending on the numbers of 

individuals adversely affected by the spilled fuel.

4.2.5.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for marine mammals are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI. Impact 

analyses presented in Chapters 4.2.2.2 and 4.2.2.3 determined that activities projected to occur 

under Alternative D would result in nominal to moderate impacts to marine mammals, depending 

on the IPF.

Mitigation measures for the proposed action under Alternative D are described in 

Chapter 2.4 and summarized in Chapter 4.2.5.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.2.2.3). The mitigation measures are the 

same as described for Alternative C with the addition of shutdown protocols during seismic 

operations for all marine mammals except bow-riding dolphins (i.e., bottlenose, Fraser’s Clymene’s, 

rough-toothed, striped, spinner, Atlantic spotted, pantropical, and Risso’s dolphins). The addition of 

shutdown protocols for all marine mammals, except bow-riding dolphins, under Alternative D would 

not change the extent, severity, or timing of activities in the proposed action; thus, the resultant 

impacts to marine mammals also would not change. Under Alternative D, the mitigation measure 

that would change the timing and extent of activities in the proposed action is a seasonal restriction 

between February 1 and May 31 for the operation of airguns in coastal waters (Federal and State) 

(Appendix B, Section 1.3.6).

The cumulative impact analysis identified nominal to minimal incremental increases in 

impacts from all IPFs under Alternative A. The cumulative scenario would remain similar for 

Alternative D, and the associated impacts would remain the same. Since portions of surveys may 

need to be re-shot due to shutdowns (ultimately avoiding Level A harassment with the potential for 

further Level B harassment), while Alternative D would change the timing of seismic airgun surveys 

in certain areas, these time area closures and restrictions (which aim at further reducing injury to 

marine animals) would not appreciably change the contributions to the cumulative impacts noted 

under Alternative A.
Gulf of Mexico G&G Activities Programmatic EIS 4-109

4.2.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.2.2). Mitigation measures in Alternative E are the same as those 

discussed in Alternative C with the exception of reduced activity levels. The following discussion 

outlines the effects of the additional mitigation measures included in Alternative E on marine 

mammals.

4.2.6.1 Impacts of Routine Activities

4.2.6.1.1 Reduced Level of Activity

For this mitigation measure under Alternative E, BOEM would authorize a reduced level of 

activity and would include the mitigation measures described in Alternative C (Chapter 4.2.4). 

There are two options:

• Alternative E1 – a reduction of deep-penetration, multi-client activities (in line 

miles) by 10 percent from the estimated levels in a calendar year (Table 2.5-1); 

and

• Alternative E2 – a reduction of deep-penetration, multi-client activities (in line 

miles) by 25 percent from the estimated levels in a calendar year (Table 2.5-2).

Current projected oil and gas exploration deep-penetration seismic activity levels are 

provided in Table 3.2-2. A 10 percent reduction of deep-penetration, multi-client activities as 

proposed in Alternative E1 is provided in Table 2.5-1, and a 25 percent reduction is provided in 

Table 2.5-2 for Alternative E2. Activities could be conducted in any of the planning areas. When the 

maximum exploration survey activities have been authorized for a calendar year, no additional 

authorization of deep-penetration, multi-client seismic oil and gas exploration activities would be 

issued for the remainder of the calendar year. In both sub-alternatives, the extent of seismic surveyrelated sound sources, vessel and equipment noise, vessel traffic, aircraft traffic and noise, and 

trash and debris would be incrementally reduced within the AOI, thus incrementally decreasing 

impacts from these IPFs on marine mammals.

Overall, the implementation of either of the two sub-alternatives for the reduction of deeppenetration, multi-client activities would not modify the predicted minor to moderate (from 

Alternative A) impact level for all marine mammals within the AOI from seismic airgun activities even 

though the area of potential impacts is reduced due to activity reduction. Based on impact level 

criteria (Chapter 4.2.2), these activity reduction options would both reduce but not eliminate 

potential auditory injury to marine mammals within the AOI both annually and over the duration of 

the proposed action. As with Alternative A, no lethal injuries are expected from exposure to 

proposed active sound sources. Anticipated numbers of potential auditory injuries (PTS) would 

remain sufficiently low such that, if actual injuries at this level were to occur, they would not affect the 

continued viability or annual rates of recruitment or survival of all local populations or stocks of 

marine mammals. The locations in which the activity reduction levels would occur could not be 
4-110 Description of the Affected Resources and Impact Analysis

definitively predicted, but if the reductions occurred in geographic regions within the AOI that are 

biologically important, such as a closure area, Settlement Areas of Concern, or BIA, then greater 

fitness benefits may be derived by the species in those areas than for other marine mammals in 

other regions of the AOI. Without being able to predict the locations or time of year in which the 

reductions may occur in the GOM, the reasonable assumption is that the fitness consequences are 

similar to those associated with Alternative A.

Reductions of deep-penetration, multi-client activity under Alternative E would not affect 

potential impacts on marine mammals associated with the other IPFs such as vessel and equipment 

noise, aircraft traffic and noise, trash and debris, and entanglement, which are the same as those 

predicted for Alternative A and which range from nominal to minor. 

4.2.6.1.2 Routine Activities Impact Conclusions

Under Alternative E, G&G activities would include implementation of existing mitigation 

requirements discussed under Alternative C, as well as a reduced level of activity for G&G surveys 

associated with the oil and gas, renewable energy, or the marine minerals programs. Mitigation 

measures for seismic airgun surveys under Alternative E include the following: 

• expanded PSO Program to include same mitigation to manatees as provided for 

whales for all water depths;

• sound source shutdowns for all marine mammals except bow-riding dolphins 

(i.e., bottlenose, Fraser’s, Clymene’s, rough-toothed, striped, spinner, Atlantic 

spotted, pantropical, and Risso’s dolphins);

• required use of PAM for all seismic surveys occurring during periods of reduced 

visibility in areas with water depths >100 m (328 ft) and at all times within the 

Mississippi Canyon and De Soto Canyon lease blocks;

• time-area closure for airgun surveys in Federal coastal waters of the GOM 

shoreward of the 20-m (65-ft) isobath between February 1 and May 31; and 

• implementation of the Seismic Airgun Survey Protocol.

Mitigation measures for non-airgun HRG surveys include the following: 

• non-airgun HRG surveys operating at frequencies >200 kHz in all water depths 

throughout the AOI will require a pre-survey clearance of all marine mammals 

(and sea turtles) before start-up or after a shutdown; and

• implementation of the Non-Airgun HRG Survey Protocol.

Additional mitigation measures associated with Alternative E include two options: a 

reduction of G&G activity levels in line miles by 10 percent in a calendar year (Alternative E-1) or by 

25 percent in a calendar year (Alternative E-2).
Gulf of Mexico G&G Activities Programmatic EIS 4-111

As discussed above, the degree to which these mitigation measures (collectively) will affect 

or change the levels of impact to marine mammals from each project-related IPF (including routine 

activities and accidental events) is presented below:

• deep-penetration airgun survey noise – minor to moderate; 

• HRG airgun survey noise – minor; 

• non-airgun HRG electromechanical survey noise – minor; 

• vessel and equipment noise – nominal to minor; 

• vessel traffic – nominal to moderate; 

• aircraft traffic and noise – nominal; 

• trash and debris – nominal; and

• entanglement – nominal. 

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1. 

Overall, the mitigation measures described under Alternative E may reduce potential impacts 

from the IPFs listed above to individuals and groups of marine mammals within the AOI depending 

on where the reduction in activities takes place. These reductions in deep-penetration airgun 

surveys may lower the impacts to marine life from moderate impacts (in Alternative A) to minor to 

moderate impacts. However, from impact significance criteria discussed in Chapter 4.2.2, overall 

impact ratings by all other IPFs for all marine mammal species within the AOI would remain the 

same as Alternative A.

4.2.6.2 Impacts of Accidental Events

Under Alternative E, impacts of an accidental fuel spill on marine mammals would be very 

similar to those analyzed in Chapter 4.2.2.2 for Alternative A. The analysis concluded that a small 

spill at the sea surface would result in nominal to minor impacts, depending on the location of the 

spill and if threatened and endangered species found within the AOI were adversely affected.

4.2.6.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for marine mammals are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 
4-112 Description of the Affected Resources and Impact Analysis

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI. Impact 

analyses presented in Chapters 4.2.6.1 and 4.2.6.2 determined that activities projected to occur 

under Alternative E would result in nominal to moderate impacts to marine mammals, depending 

on the IPF.

Mitigation measures for the proposed action under Alternative E are described in 

Chapter 2.5 and summarized in Chapter 4.2.6.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.2.2.3). The reduction of deeppenetration, multi-client activities by 10 percent (Alternative E1) or 25 percent (Alternative E2) would 

reduce the extent, severity, and timing of active acoustic sound sources, vessel and equipment 

noise, vessel traffic, aircraft traffic and noise, and trash and debris. As discussed in Chapter

4.2.6.1, the implementation of either of the two alternatives for the reduction of deep-penetration, 

multi-client activities would not reduce the predicted moderate (from Alternative A) impact level for 

all marine mammals within the AOI from seismic airgun activities. Based on impact level criteria 

(Chapter 4.2.2), these activity reduction options would both reduce but not eliminate potential 

auditory injury to marine mammals within the AOI both annually and over the duration of the 

proposed action.

While the impacts from deep-penetration seismic surveys would decline, the impacts from 

the other IPFs would remain unchanged. The cumulative impact analysis identified nominal to 

minor incremental increases in impacts from all IPFs under Alternative A. The contributions to 

cumulative impacts would remain similar for Alternative E, and the associated impacts would remain 

the same.

4.2.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.2.2). Mitigation measures in Alternative F are the same as those discussed 

in Alternative C with the exception of area closures. The following discussion outlines the effects of 

the additional mitigation measures included in Alternative F on marine mammals.

4.2.7.1 Impacts of Routine Activities

4.2.7.1.1 Closure Areas 

Alternative F includes four area closures (i.e., Flower Gardens Closure Area, CPA Closure 

Area, EPA Closure Area, and Dry Tortugas Closure Area) (Figure 2.6-1). The selection of these 

closure areas was based on relative densities of target species within the AOI and expert opinion 

regarding the biological importance of these geographic areas. Target species include the sperm 

whale (endangered), Bryde’s whale (the only resident mysticete within the AOI), and beaked whales, 

as well as reef and pelagic fishes associated with the FGBNMS.
Gulf of Mexico G&G Activities Programmatic EIS 4-113

The Flower Gardens Closure Area was designed to protect marine resources (primarily reef 

and pelagic fishes) associated with the FGBNMS. This closure area was not selected for additional 

protection for cetacean species within the AOI; however, this closure would provide benefit to any 

marine animal in the closure area. The marine mammals that are common in this closure area 

include, but are not limited to, the beaked whale (Mesoplodon sp.), Atlantic spotted dolphin, and 

bottlenose dolphin.

The CPA Closure Area was derived by combining Settlement Area of Concern 1 and the 

western part of Area of Concern 2 (to the boundary of the CPA) and redrawing the southern 

boundary to encompass additional sperm and beaked whale occurrence records (however, the 

closure would provide benefit to any marine animal in the closure area). The waters of the 

CPA Closure Area support relatively high densities of sperm and beaked whales. Satellite tracking 

studies conducted by Jochens et al. (2008) indicate that the home range of tagged sperm whales 

within the northern GOM is broad, encompassing waters deeper than 500 m (1,640 ft). Home range 

is defined as an area over which an animal or group of animals regularly travels in search of food or 

mates and that may overlap with those of neighboring animals or groups of the same species. By 

contrast, the composite core area for GOM sperm whales generally includes the Mississippi Canyon, 

Mississippi River Delta, and, to a lesser extent, the Rio Grande Slope (Jochens et al., 2008). The 

composite core area is a section of the home range that is utilized more thoroughly and frequently 

for activities such as feeding. Satellite tagging data of sperm whale movements in the northern 

GOM show that sperm whales aggregate in the Mississippi Canyon area, including the proposed 

CPA Closure Area, but regularly move through the waters over the northern GOM continental slope. 

Movement patterns or seasonal migrations of beaked whales in the GOM are not known, though it is 

likely that their distributional patterns depend on the movement of mesoscale hydrographic features 

and their prey (USDOC, NOAA, 2015a).

Bryde’s whales that inhabit the northern GOM represent a resident GOM stock and have 

only been observed in a limited area of the northeastern GOM between the 100- and 400-m 

(328- and 1,312-ft) isobaths from south of Pensacola, Florida, to 27.5° N. latitude and between the 

100- and 300-m (328- and 984-ft) isobaths from 27.5° N. latitude south to around Tampa, Florida, 

based on sighting surveys and recent sighting records (Maze-Foley and Mullin, 2006; Waring et al., 

2013; Rosel and Wilcox, 2014). Under Alternative F, the EPA Closure Area was refined and 

expanded from the boundaries of the year-round BIA for the small, resident population of Bryde’s 

whales in the GOM (LaBrecque et al., 2015). The boundaries of the EPA Closure Area were 

expanded from that of the Bryde’s whale BIA, where from 87.5° W. longitude to 27.5° N. latitude

along the western boundary of the BIA, the EPA Closure Area’s boundary was extended to the 400-

m (1,312-ft) isobath. While the EPA Closure Area was selected based on the biological importance 

to the Bryde’s whale, the closure would provide benefit to any marine animal in the closure area.

The Dry Tortugas Closure Area includes waters bounded by the 200- and 2,000-m (656- and 

6,562-ft) isobaths (or U.S. EEZ) from the northern border of BOEM’s Howell Hook leasing area to 

81.5° W. longitude. Sighting data indicate that beaked whale and sperm whale numbers are very 

dense in this area. In addition, based on unpublished observations and passive acoustic recordings 
4-114 Description of the Affected Resources and Impact Analysis

data, it is possible that sperm whales may use this area for calving based on the number of calves 

sighted (Hildebrand et al., 2012). As with the CPA Closure Area, the Dry Tortugas Closure Area 

also likely supports a segment of the sperm whale stock’s home range or perhaps at least 

represents a separate core area. While the Dry Tortugas Closure Area was selected based on the 

sightings and densities of beaked whales and sperm whales, the closure area would provide benefit 

to any marine animal in the closure area.

Closure of the EP, Flower Garden, CP, and Dry Tortugas Closure Areas from airgun surveys 

would provide potential refuge to the associated Bryde’s, sperm, and beaked whale species in 

addition to other deepwater cetacean species of the GOM during the 10-year period. However, with 

exception of the Bryde’s whale whose distribution appear to be limited to the waters of northeastern 

GOM, cetacean species regularly move outside of the boundaries of the closure areas. Thus, 

protection afforded to these individuals by area closures would be limited to biologically important 

periods and geographic locations (such as feeding behaviors and locations), while their movements 

would expose them to potential impacts from airgun survey activities. Mitigation provided by the 

implementation of these closure areas would reduce but not prevent the potential for occurrence of 

injurious auditory impacts (Level A) to marine mammals of the AOI.

Selection of Alternative F with its associated area closures to seismic surveys during 

biologically important periods would result in a reduced level of exposure to the active acoustic 

source IPF, particularly for specific regions of the AOI, thus resulting in an overall incrementally 

reduced impact to the marine mammals within these areas of the AOI from deep-penetration seismic 

sound sources. Compared with the impact level of Alternative A (nominal to moderate), the impact 

level of Alternative F may be incrementally reduced to nominal to minor. 

Quantitative Assessment of Alternative F

The closure areas included in Alternative F were chosen to provide protective measures to 

the target species identified above. The areas themselves were selected based on modified 

Plaintiffs’ Area of Concern (the original AOCs are described further in Alternative B) and on the basis 

of expert opinion. To estimate the level of protection provided by the closure areas, a quantitative 

assessment was conducted. Since the final exposure estimates are the multiplicative product of the 

modeled exposures and animal density estimates, an extension of this logic was used to assess the 

effect of the area closures on the predicted exposure estimates. Specifically, animal densities were 

determined for each modeling area, with and without individual closures, and then cumulatively for 

those instances in which multiple closures exist within a modeling zone (Appendix D, Figure 110). 

Since the Seasonal Restriction for Coastal Waters is not permanent a closure, but includes a 

temporal dimension, the duration of the Seasonal Restriction for Coastal Waters was also accounted 

for in the calculations. The ratio of these two density values provides the percentage of impact of 

that closure on the species-specific exposure estimates. These density ratios (Table 4.2-6) provide 

an indication of the magnitude of the effect of the closure areas upon predicted exposure values 

(Appendix D). Those density ratios <1.0 indicate that there would likely be a reduction in the 

predicted exposure estimates, whereas a density ratio >1.0 indicates that there would likely be an 
Gulf of Mexico G&G Activities Programmatic EIS 4-115

increase in the predicted exposure estimates. To fully calculate modified exposure numbers is more 

involved than simply multiplying these ratios by the final decadal take numbers included in 

Appendix D, since the density ratios are calculated for each modeling zone separately, and the 

level of effort through the 10-year period is not uniform across zones or time. Therefore, these 

density ratios provide an indication, or sense, for the effect of the individual and collective closure 

areas on the exposure estimates, but the density ratios cannot be used in direct multiplication 

against the decadal exposure estimates.

Implicit in this evaluation is the assumption that the level of exploratory effort (i.e., the 

number of kilometers of seismic survey effort within a zone) will remain constant, even though the 

closure areas would not be available. Therefore, more survey effort would occur in non-closure 

areas within the zone to compensate for the area lost by the closure. Thus, the Alternative F 

exposure estimates under this analysis represent the minimum mitigative effect of the closures. If 

the level of survey effort were to be reduced due to the reduction in available area within the 

modeling zone, then exposure estimates would be reduced below the density ratios included in 

Table 4.2-6. The seasonal coastal closures are unlikely to affect the level of survey effort since the 

survey effort would likely shift to those seasons in which the coastal areas are available for 

exploration. However, the permanent closures reduce the total area available for exploration, which 

might lead to a reduction in survey effort within that modeling zone. If so, then the ratios of zonal 

areas with and without permanent closures could be used as an additional proxy to estimate the 

level of survey effort reduction, which would ultimately result in additional exposure reduction.

While the overall take numbers with and without closure areas is informative to this analysis, 

it is also important to understand what protection these areas may provide to a specific species or 

stock. These closure areas represent important biological habitat, such as for calving and nursing or 

where high densities of a species or stock are generally found. Although individuals may still be 

exposed outside of these areas, protection within these areas is likely more biologically meaningful 

to these specific species or stock than other areas within the AOI. Therefore, the difference in 

impact levels must be ascertained not only by looking at reductions in take numbers but also at the 

value of protection to the species or stock as a whole within these specified closure areas.

Seasonal Restriction for Coastal Waters

The Seasonal Restriction for Coastal Waters (Figure 2.6-1) had different effects in the three 

different coastal zones (Zones 1, 2 and 3; Appendix D, Figure 110). The bottlenose dolphin was 

the only species to show decreased density ratio in all three coastal zones. For all other species, in 

Zones 1 and 2, the density ratios were greater than 1.0 (Table 4.2-6), indicating a likely overall 

increase in the exposure estimates (Appendix D) as a result of this seasonal restriction. In Zone 3, 

the closure had varying effects on the other species. The density ratio for the Clymene and spinner 

dolphins decreased the most due to the Seasonal Restriction for Coastal Waters, while though since 

these species are not found within coastal waters, their densities are very small under both 

conditions and the difference is not significant. The Atlantic spotted dolphin, false killer whale, 

Fraser’s dolphin, killer whale, and striped dolphin all showed an increased density ratio (Table 
4-116 Description of the Affected Resources and Impact Analysis

4.2-6), indicating a likely overall increase in the exposure estimates (Appendix D) as a result of this 

seasonal restriction. The remaining species all exhibited density ratios close to 1, which correlates 

to little or no change from the original density estimate.

CPA Closure Area

The CPA Closure Area (Figure 2.6-1) occurs in Zones 5 and 7 (Appendix D, Figure 110), 

and this closure area focuses on the protection of sperm whales and beaked whales. The sperm 

whales in Zone 5 exhibited a decrease in density ratio of 0.827 and beaked whales in this area 

exhibited a decrease in density ratio of 0.982 (Table 4.2-6). The spinner dolphin in Zone 5 exhibited 

the greatest decrease in density ratio of 0.157 (Table 4.2-6). All of the other species in Zone 5 had 

either a decrease or no change in density ratios, except for the Atlantic spotted dolphin, Bryde’s 

whale, Clymene dolphin, and the short-finned pilot whale (Table 4.2-6), indicating likely no 

significant change in the exposure estimates as a result of this closure area (Appendix D).

The spinner dolphin also had the lowest density ratio in Zone 7 due to the CPA Closure 

Area. In this zone, all of the other species had density estimates close to 1, which means that they 

were unchanged from the original estimates, indicating likely no significant change in the exposure 

estimates (Appendix D) from this closure area.

EPA Closure Area

The EPA Closure Area (Figure 2.6-1) had a greater reduction on the density ratio in Zone 1 

as compared with those in Zone 4 (Appendix D, Figure 110). This closure area focuses on the 

restricting activities around Bryde’s whales. The Bryde’s whale exhibited a decrease in density 

ratios in both Zones 1 and Zone 4, which are 0.442 and 0.584, respectively (Table 4.2-6). All of the 

species had a lower density ratio in Zone 1 than in Zone 4, except for the bottlenose dolphin, which 

showed an increased ratio in Zone 1. The striped dolphin had the lowest density ratio in Zone 1 of 

0.191, while the bottlenose dolphin had the highest density ratio of 1.051 (Table 4.2-6) likely 

indicating a wide range of potential changes in the exposure estimates (Appendix D) from this 

closure area. The Atlantic spotted dolphin had an increased density ratio, while all of the remaining 

species has decreased or unchanged density ratios as a result of this closure area (Table 4.2-6).

In Zone 4, the species with the lowest density ratio is the Bryde’s whale (Table 4.2-6). The 

other species with ratios less than 1 include the Atlantic spotted dolphin, bottlenose dolphin, false 

killer whale, and Fraser’s dolphin. All of the other species exhibit ratios greater than 1, indicating a 

likely resulting increase in exposure estimates (Appendix D) as a result of this closure area.

Dry Tortugas Closure Area

The Dry Tortugas Closure Area (Figure 2.6-1) in Zone 4 (Appendix D, Figure 110) 

produced and focuses on the protection of Bryde’s whales. The Bryde’s whale exhibited a decrease 

in density ration in Zone 4, which is 0.625 (Table 4.2-6). This closure produced notable decreases 

in density ratio for the beaked whale, bottlenose dolphin, killer whale, Kogia, pantropical spotted 
Gulf of Mexico G&G Activities Programmatic EIS 4-117

dolphin, pygmy killer whale, Risso’s dolphin, short finned pilot whale, and the sperm whale, 

indicating a likely decrease in the exposure estimates (Appendix D) as a result of this closure area. 

The striped dolphin shows the greatest increase in density ratio due to this closure area, along with 

the Bryde’s whale and Clymene dolphin (Table 4.2-6). All of the other species have density ratios 

close to 1 and, therefore, can be considered unchanged from the original density and likely resulting 

in unchanged exposure estimates (Appendix D) as a result of this closure area.

Mitigative Effects of Closure Areas

In Zone 1 (Appendix D, Figure 110), the EPA Closure Area and Seasonal Restriction for 

Coastal Waters were combined. In the case when both this closure area and seasonal restriction 

would be implemented, the Atlantic spotted dolphin is the only species that demonstrates an 

increase in density ratio (Table 4.2-6), likely resulting in an increase in the exposure estimates 

(Appendix D). The bottlenose and rough-toothed dolphin both have density ratios close to 1 and, 

therefore, would be unchanged, while all of the other species show a decrease in density ratios, 

likely resulting in a decrease to the exposure estimates (Appendix D) resulting from these collective 

restrictions. Combining these two areas (EPA Closure Area and Seasonal Restriction for Coastal 

Waters) produces an overall decrease in density ratios, with a likely decrease in the exposure 

estimates (Appendix D) when compared with the Seasonal Restriction for Coastal Waters alone.

In Zone 4 (Appendix D, Figure 110), the Dry Tortugas and EPA Closure Areas were 

combined. With these closure areas combined, the density ratios for the Clymene dolphin, melonheaded dolphin, and the striped dolphin all increased dramatically from each closure area 

implemented separately. The Atlantic spotted dolphin, short-finned pilot whale, and spinner dolphin 

also showed increased ratios, while the remaining species had either unchanging or decreased 

ratios (Table 4.2-6). The combination of these two closure areas resulted in more density ratios 

(Table 4.2-6) consistent with the original density estimate (near 1) than if either of the two closure 

areas were implemented alone, likely resulting in minimal changes in the exposure estimates 

(Appendix D). The estimates due to the EPA Closure Area were generally larger than those 

resulting from the combined closure areas.

Since an area may be closed based on its biological importance to one or more species, a 

reduction in not only exposures but also in avoidance of a biologically important area is also an 

important measure. The reduction of impacts to an area of biological importance may have more 

benefit to marine animals than may be implied through this quantitative analysis. A reduction of 

impacts in an area of biological importance may have more benefit to the species than quantified 

through the number of exposures avoided. Therefore, the benefit to the species may be greater 

than quantified in this analysis.

4.2.7.1.2 Routine Activities Impact Conclusions

Under Alternative F, BOEM would continue to authorize activities and include the mitigation 

measures, monitoring, reporting, survey protocols, and guidance that are currently in place (as per 

Alternative A), as well as additional mitigation measures including the Seismic Airgun Survey 
4-118 Description of the Affected Resources and Impact Analysis

Protocol and Non-Airgun HRG Survey Protocol, as applicable (Alternative C), and four area closures 

to provide additional protection for certain cetacean species and other resources: CPA Closure 

Area; EPA Closure Area; Dry Tortugas Closure Area; and Flower Gardens Closure Area. Under

Alternative F, these areas are closed to all activities except non-airgun HRG surveys in which one or 

more active acoustic sound sources will be operating at frequencies >200 kHz. Mitigation measures 

for seismic airgun surveys include the following: 

• expanded PSO Program to include same mitigation to manatees as provided for 

whales for all water depths;

• required use of PAM for all seismic surveys occurring during periods of reduced 

visibility in areas with water depths >100 m (328 ft) and at all times within the 

Mississippi Canyon and De Soto Canyon lease blocks;

• time-area closure for airgun surveys in Federal coastal waters of the GOM 

shoreward of the 20-m (65-ft) isobath between February 1 and May 31; 

• implementation of the Seismic Airgun Survey Protocol; and

• closure for all new seismic airgun and non-airgun HRG surveys in the CP, EP, 

Dry Tortugas, and Flower Garden Banks closure areas.

Additional mitigation measures for non-airgun HRG surveys include the following: 

• non-airgun HRG surveys operating at frequencies >200 kHz in all water depths 

throughout the AOI will require a pre-survey clearance of all marine mammals 

(and sea turtles) before start-up or after a shutdown; and

• implementation of the Non-Airgun HRG Survey Protocol.

As discussed above, the degree to which these mitigation measures (collectively) will affect 

or change the levels of impact to marine mammals from each project-related IPF (including routine 

activities and accidental events) is presented below:

• deep-penetration airgun survey noise – minor; 

• HRG airgun survey noise – minor; 

• non-airgun HRG electromechanical survey noise – minor; 

• vessel and equipment noise – nominal to minor; 

• vessel traffic – nominal to moderate; 

• aircraft traffic and noise – nominal; 

• trash and debris – nominal; and

• entanglement – nominal. 
Gulf of Mexico G&G Activities Programmatic EIS 4-119

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1.

Overall, the mitigation measures described under Alternative F may reduce potential impacts 

from the IPFs listed above to individuals and groups of marine mammals within the AOI as 

discussed above. In addition, Alternative F with its associated area closures to seismic surveys 

during biologically important periods (coastal waters seasonal restrictions) would result in a reduced 

level of exposure to the active acoustic source IPF, particularly for specific regions of the AOI, thus 

resulting in an overall incrementally reduced impact to the potentially occurring marine mammals 

within the AOI from deep-penetration seismic sound sources. Impact ratings for other IPFs would 

remain about the same as Alternative A.

4.2.7.2 Impacts of Accidental Events 

Under Alternative F, impacts of an accidental fuel spill on marine mammals would be very 

similar to those analyzed in Chapter 4.2.2.2 for Alternative A, but they would potentially reduce the 

risk that such a spill would occur in the closure areas because there would be reduced activities in 

these areas. The analysis concluded that a small spill at the sea surface would result in nominal to 

minor impacts, depending on the location of the spill and if threatened and endangered species 

found within the AOI were adversely affected.

4.2.7.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for marine mammals are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI. Mitigation 

measures for the proposed action under Alternative F are described in Chapter 2.6 and summarized 

in Chapter 4.2.7.1. A detailed impacts assessment under the cumulative scenario is provided in 

Alternative A (Chapter 4.2.2.3). Mitigation measures under Alternative F are to the same as 

Alternative C with the addition of area closures in four areas: the CPA Closure Area; the EPA 

Closure Area; the Dry Tortugas Closure Area; and the Flower Gardens Closure Area. Areas 

selected for closure from deep-penetration seismic airgun survey activities were designed to focus 

on mitigation of deep-penetration seismic impacts to a single species or select group of species.

Mitigation measures under Alternative F that would change the timing and extent of activities 

in the proposed action include a seasonal restriction for operation of airguns in Federal and State 

coastal waters, which was designed to protect coastal stocks of the bottlenose dolphin during their 

reproductive peak. As discussed in Chapter 4.2.7.1, the implementation of area closures to seismic 
4-120 Description of the Affected Resources and Impact Analysis

surveys during biologically important periods (e.g., coastal waters seasonal restrictions) would result 

in an overall incrementally reduced impact (nominal to minor) to the potentially occurring marine 

mammals within the AOI from deep-penetration seismic sound sources.

The cumulative impact analysis identified nominal to minor incremental increases in 

impacts to marine mammals from all IPFs described under Alternative A. Since activity level would 

remain the same in this alternative, the overall cumulative scenario would remain mostly unchanged 

for Alternative F, and the associated overall impacts would remain similar (nominal to minor). 

However, there would be reductions to cumulative impacts within closure areas.

4.2.8 Impacts – Alternative G (No New Activity Alternative)

Since Alternative G is no new activity for oil and gas G&G activities, any existing permitted 

activity and ancillary activities would be ongoing and the mitigation measures would be the same as 

Alternative A. Activity level would then slowly decline over a period of several years. For this 

reason, IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.2.2), except the IPF of entanglement is not included as part of Alternative G 

because no OBC/nodal surveys would occur. Mitigation measures included in Alternative G are the 

same as included in Alternative A.

4.2.8.1 Impacts of Routine Activities

4.2.8.1.1 Active Acoustic Sources

Oil and gas G&G survey activities would slowly decline to zero over a period of several 

years. No new on-lease G&G activities related to renewable energy development could be 

conducted, and no new G&G activities related to marine minerals would be authorized by BOEM for 

survey activities located in Federal waters that require BOEM’s authorization. The only survey 

activities that would continue to occur under this alternative are geophysical surveys associated with 

drilling activities (VSPs), which puts less acoustic energy in the environment. Appendix F, Section

1.1.5 provides descriptions of these surveys, which include the use of airgun active acoustic 

sources. Source characteristics are summarized in Table 4.1-1, and detailed characteristics and 

acoustic modeling assumptions are presented in Appendix D. The potential impacts of VSPs and 

SWD surveys are the same as those described for these types of surveys above in Alternative A 

(Chapter 4.2.2.1), however, at greatly reduced impact levels commensurate with the reduction in 

survey effort (Table 2.7-1). Effects of project-related seismic airgun survey noise on marine 

mammals within the AOI are expected to be reduced to minor and would decline to no impact as 

activities ended, as impacts to marine mammals would be limited to individuals or groups and not be 

extensive or severe, are expected to affect individuals or groups from local populations within the 

AOI, and would be limited to behavioral harassment and small (limited) numbers of physical injuries. 

However, there is the slight potential for onset injury (PTS) to occur. Potential non-injurious impacts 

would include temporary displacement of individuals, possibly including displacement from preferred 

habitats in some cases. Animals are expected to return to these habitats following the distancing of 

the sound source or the cessation of survey activities.
Gulf of Mexico G&G Activities Programmatic EIS 4-121

4.2.8.1.2 Vessel and Equipment Noise

The G&G activities that would continue under Alternative G would generate vessel and 

equipment noise that could disturb marine mammals. The potential impacts are the same type as 

those described under Alternative A (Chapter 4.2.2.1), however at greatly reduced impact levels 

commensurate with the level of ongoing activities (Table 2.7-1). Based on the existing vessel traffic 

within the AOI, the effects of project-related vessel and equipment noise on marine mammals within 

the AOI would be nominal to minor and would decline to no impact. Impacts to marine mammals 

from project-related vessel and equipment noise are expected but are not extensive or severe, and 

would include temporary disruption of communication or echolocation from auditory masking; 

behavior disruptions of individual or localized groups of marine mammals; and limited, localized, and 

short-term displacement of individuals of any species, including strategic stocks, from localized 

areas around the vessels.

Drilling-related noises anticipated under Alternative G include the completion of one possible 

COST well and up to two shallow test wells in the AOI (Table 2.7-1). The potential impacts are the 

same as those that would occur with Alternative A (Chapter 4.2.2.1), with the same impact 

significance (nominal to minor) due to the low number of proposed drilling operations and the 

continuous nature of the sounds, but would decline to no impact as activities ended.

4.2.8.1.3 Vessel Traffic

Although the vessel traffic associated with Alternative G would be greatly reduced, the 

potential impacts (physical disturbance from or collision with moving vessels) are the same as those 

that would occur with Alternative A (Chapter 4.2.2.1), with the same impact level (nominal to 

moderate [if a collision occurred]), and would decline to no impact. 

4.2.8.1.4 Aircraft Traffic and Noise

Although the aircraft traffic and associated noise would decrease under Alternative G, the 

potential impacts (noise and physical disturbance) are the same as those that would occur with 

Alternative A (Chapter 4.2.2.1), with the same impact level (nominal), and would decline to no 

impact. 

4.2.8.1.5 Trash and Debris

The potential impacts from trash and debris are the same as those that would occur with 

Alternative A (Chapter 4.2.2.1), with the same impact level (nominal), and would decline to no 

impact. 

4.2.8.1.6 Routine Activities Impact Conclusions

Under Alternative G, BOEM would cease issuing permits or authorizations for new G&G 

surveys and would not approve G&G surveys proposed under exploration or development plans. 

However, G&G activities previously authorized under an existing permit or authorization or lease 
4-122 Description of the Affected Resources and Impact Analysis

would proceed. Mitigation measures for the existing ongoing permitted and ancillary oil and gas 

G&G activities that are associated with Alternative G include the following: 

• guidance for vessel strike avoidance;

• guidance for marine debris awareness;

• avoidance of sensitive benthic resources;

• guidance for shallow hazards survey and reporting;

• guidance for activities in or near National Marine Sanctuaries (NMS); 

• guidance for avoidance of historic and prehistoric sites; 

• guidance for military coordination;

• guidance for ancillary activities (oil and gas program only);

• implementation of PSO program (oil and gas program only); and

• implementation of the Seismic Airgun Survey Protocol.

As discussed above, the degree to which these mitigation measures (collectively) will affect 

or change the levels of impact to marine mammals from each project-related IPF (including routine 

activities and accidental events) is presented below:

• deep-penetration airgun survey noise – minor declining to no impact; 

• HRG airgun survey noise – minor declining to no impact; 

• non-airgun HRG electromechanical survey noise – minor declining to no 

impact; 

• vessel and equipment noise – nominal to minor declining to no impact; 

• vessel traffic – nominal to moderate declining to no impact; 

• aircraft traffic and noise – nominal declining to no impact; 

• trash and debris – nominal declining to no impact. 

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1. 

Overall, the removal of all new G&G survey activities within the AOI, as described under 

Alternative G, would reduce potential impacts from the IPFs listed above to individuals and groups of 

marine mammals within the AOI. However, G&G activities previously authorized under an existing 

permit/authorization or lease would proceed under Alternative G. From impact significance criteria 

discussed in Chapter 4.2.2, overall impact ratings by IPF from these surveys for all marine mammal 
Gulf of Mexico G&G Activities Programmatic EIS 4-123

species within the AOI would remain the same as Alternative A but would decline to no impacts as 

G&G activities ended.

4.2.8.2 Impacts of Accidental Events

The accidental events considered under Alternative A (accidental release of 1.2 to 7.1 bbl of 

diesel fuel caused by a vessel collision or an accident during fuel transfer; Chapter 4.2.2.2) are the 

same as those that would occur with Alternative G. Although there would be reduced vessel traffic 

and therefore a reduction in the potential for an accidental fuel spill, the same analysis and impact 

level (nominal to minor) would be estimated for Alternative G as for Alternative A, but they would 

decline to no impacts as G&G activities ended.

4.2.8.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for marine mammals are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI.

A detailed impacts assessment under the cumulative scenario is provided in Alternative A 

(Chapter 4.2.2.3). The cumulative impact analysis identified nominal to minor incremental 

increases in impacts from all IPFs under Alternative A. The cumulative scenario would remain 

unchanged for Alternative G, except that no additional impacts to the IPF of entanglement would 

occur, and the associated impacts would remain the same. Therefore, there are nominal to minor

changes to the cumulative impacts determined under Alternative A, which would then decline to no 

impacts as G&G activities ended.

4.3 SEA TURTLES

4.3.1 Description of the Affected Environment

Five species of sea turtles, i.e., loggerhead (Caretta caretta), green (Chelonia mydas), 

Kemp’s ridley (Lepidochelys kempi), hawksbill (Eretmochelys imbricata), and leatherback 

(Dermochelys coriacea), occur at least seasonally in the northern GOM; all are listed as threatened 

or endangered under the ESA (Figure 4.3-1; Table 4.3-1). Detailed information about the 

distribution, population, life history and natural ecology, threats, and status of the five species of sea 

turtles may be found in Appendix E, Section 3. Under the ESA, NMFS has divided the populations 

of loggerhead sea turtles into distinct population segments (DPSs). A DPS is a population of a 

species that is discrete from other populations of the species and significant in relation to the entire 

species. Loggerhead sea turtles that occur in the GOM are assumed to be part of the Northwest 
4-124 Description of the Affected Resources and Impact Analysis

Atlantic Ocean DPS, which is listed as threatened under the ESA. Within the most recent Recovery 

Plan for the Northwest Atlantic population of the loggerhead sea turtle, NMFS has identified five 

recovery units, four of which are located in U.S. waters (USDOC, NMFS and USDOI, FWS, 2008) 

(Figure 4.3-2). Critical habitat has been designated under the ESA in the GOM for the Northwest 

Atlantic Ocean DPS of loggerhead sea turtles (79 FR 39856). Three types of critical habitat are 

found in the northern GOM: nearshore reproductive habitat, Sargassum habitat, and breeding 

habitat (Figure 4.3-3). Breeding critical habitat in the GOM is restricted to the waters extending from 

the Florida Strait to the Dry Tortugas. Nearshore reproductive critical habitat is located in the State 

waters of Mississippi, Alabama, and Florida, and Sargassum critical habitat is located in the oceanic 

waters of the AOI (Figure 4.3-3). Critical habitat for loggerheads is also designated onshore for 

nesting beaches in Mississippi, Alabama, and Florida (79 FR 39755). In March 2015, NMFS 

published a proposed rule to remove the current range-wide listing for green sea turtles and to 

replace it with eight DPSs as threatened and three as endangered. Green sea turtles found in the 

GOM are part of the threatened North Atlantic DPS (80 FR 15272). The NMFS is currently 

compiling comments on the proposed rule, with a final rule expected to be published in late 2016.

All five of the sea turtle species nest on beaches along the coast of at least one state 

bordering the northern GOM (Figure 4.3-1; Table 4.3-1). With the exception of Florida, sea turtle 

nesting in the northern GOM is often not systematically documented. Texas beaches support 

significant nesting by Kemp’s ridley sea turtles, mostly on North and South Padre Islands. An 

average of 136 Kemp’s ridley nests per year were documented from Texas from 2010 through 2014 

(Shaver, official communication, 2015). In Louisiana and Mississippi, no regular surveys are 

conducted, so nesting reports are anecdotal. Louisiana supports low levels of nesting by loggerhead 

and possibly Kemp’s ridley sea turtles, mostly on Breton and Chandeleur Islands and in Grand Isle. 

In 2015, two loggerheads nested on Grand Isle beach (Lauritsen, official communication). 

Mississippi beaches support low levels (0 to 15 nests per year) from loggerheads and possibly 

Kemp’s ridley sea turtles, primarily on Petit Bois and Horn Islands (Lauritsen, official communication, 

2015). Alabama has documented an average of 68 loggerheads and 1 Kemp’s ridley nest per year 

from 2002 through 2014 (Ingram, official communication, 2015). The loggerhead sea turtle is the 

most widespread sea turtle in the GOM, occurring throughout the GOM and nesting on beaches of 

nearly every state, but principally in western Florida. As many as 906 loggerhead nests per year 

were reported for the northern GOM (not including peninsular Florida) from 1995 through 2007 

(USDOC, NMFS and USDOI, FWS, 2008). In 2014, 11,050 loggerhead sea turtle nests were 

reported for western Florida (State of Florida, Fish and Wildlife Conservation Commission, 2015).

Hawksbill, green, and leatherback sea turtle nesting in the northern GOM is very infrequent. 

Hawksbill nests have been documented on the Atlantic Coast of Florida and in the Florida Keys and 

once in Texas in 1998. Alabama recorded one green sea turtle nest in 2012, and a single 

leatherback nest was documented in Louisiana in 1989. Although there are no more recent reports 

of nesting in some states along the GOM, all five species of sea turtles in the AOI occur year-round 

in the coastal, nearshore, and offshore waters of the GOM in at least one of their life history stages. 

Each of the species has a juvenile stage thought to be distributed almost exclusively in offshore 

pelagic habitats. These juvenile stages, which include post-hatchlings leaving nesting beaches and 
Gulf of Mexico G&G Activities Programmatic EIS 4-125

small oceanic-stage juveniles, are most often found in close association with Sargassum drift algae 

habitats, which they use as developmental habitat before making a transition to shallow-water 

habitats at 1-3 years of age (Bolten, 2003). Witherington et al. (2012) conducted vessel-based 

transect surveys from five Florida ports from Pensacola to Key West extending up to 120 km (75 mi) 

offshore to evaluate the abundance, species composition, and behavior of oceanic-stage juvenile 

sea turtles in the eastern GOM. They found that 89 percent of all sea turtle observations occurred 

within 1 m (3 ft) of floating Sargassum and that sea turtle density estimates in Sargassum habitats 

were nearly 100 times higher than in open-water areas where Sargassum was not present. Ninety 

captures of oceanic-stage juvenile sea turtles revealed a species composition dominated by green 

sea turtles (49%) and Kemp’s ridleys (42%) and lower abundances of hawksbills (7%) and 

loggerheads (2%). In addition, large numbers of post-hatchling sea turtles were observed, but only 

during hatching season on the adjacent Florida nesting beaches (July-October). On a broader 

scale, Putman et al. (2013) generated predicted distributions for the distribution of oceanic-stage 

Kemp’s ridley sea turtles throughout the GOM basin using simulated particle dispersal with ocean 

circulation models. They found that the predicted highest abundance for Kemp’s ridley oceanicstage juveniles was in the far western GOM, with 50 percent of the individuals expected to remain 

west of 90° W. longitude.

Following the oceanic stage, sea turtles (with the exception of leatherbacks) transition to 

shallow coastal waters (generally <30-m [98-ft] depth), where there is appropriate developmental 

habitat for larger juvenile, sub-adult, and adult life history stages. In deeper waters, some sea turtles 

and in particular loggerheads, are often seen associated with man-made structures (e.g., platforms). 

Eaton et al. (2008) provide a summary of data on sea turtle distribution, abundance, and species 

composition in nearshore waters from 12 sites on the western coast of Florida. Few in-water studies 

of sea turtle populations have been conducted in the nearshore waters of the GOM outside Florida. 

McDaniel et al. (2000) conducted aerial surveys for sea turtles over a broad area of the eastern 

GOM nearshore zone. Although the aerial surveys were unable to differentiate between species and 

likely missed smaller individuals, they found a pattern of increasing sea turtle abundance in 

nearshore waters as they moved from the northern GOM offshore of Louisiana and Mississippi 

(0.05-0.10 sea turtle observations per transect kilometer [obs/km]) to the Florida coastal waters, with 

the highest abundance recorded in the waters offshore of the Florida Keys (0.35-1.0 obs/km). 

Inwater Research Group, Inc. (2014) conducted 2,300 km (1,429 mi) of vessel-based transect 

surveys for sea turtles in the near coastal waters of eastern Louisiana. These surveys were able to 

differentiate between species and estimated overall sea turtle abundance at 0.27 obs/km. 

Observations were dominated by Kemp’s ridleys (0.12 obs/km) and loggerheads (0.11 obs/km), with 

considerably lower numbers of leatherbacks (0.04 obs/km) and green sea turtles (0.006 obs/km). 

Offshore protected species surveys conducted during seismic operations collected sea turtle sighting 

data between 2002 and 2008 in the GOM. There were 579 sighting records of sea turtles 

representing all five species (Barkaszi et al., 2012). The percentage of each species represented in 

the records was as follows: loggerhead (40.2%); green (22%); leatherback (16.1%); Kemp’s ridley 

(9.5%); hawksbill (3.1%); and unidentified Chelonid sea turtle (%). The water depths for these 

sightings ranged from 13 to 4,380 m (43 to 14,370 ft) with an average depth of 1,366 m (4,482 ft). In 

278 (48%) sightings records, the sea turtle was identified as a juvenile.
4-126 Description of the Affected Resources and Impact Analysis

The Deepwater Horizon explosion, oil spill, and response have impacted sea turtles that 

have come into contact with oil and remediation efforts (including use of dispersants). The Final 

PDARP/PEIS estimates between 4,900 and up to 7,600 large juvenile and adult sea turtles (i.e., 

Kemp’s ridleys, loggerheads, and unidentified hard-shelled sea turtles) and between 55,000 and 

160,000 small juvenile sea turtles (Kemp’s ridleys, green, loggerheads, hawksbills, and hard-shelled 

sea turtles not identified to species) mortalities by exposure to the Deepwater Horizon oil spill and 

response. Necropsy results from many of the stranded turtles indicated mortality due to forced 

submergence, which is commonly associated with fishery interactions (one of the main sea turtle 

threats). Hatchling sea turtles (i.e., loggerheads, Kemp’s ridleys, and green) and associated habitats 

were also impacted by response activities (Deepwater Horizon Natural Resource Damage 

Assessment Trustees, 2016).

Data on nearshore and offshore sea turtle distribution in the northern GOM was collected 

following the Deepwater Horizon oil spill in 2010. A summary of the effects of the Deepwater 

Horizon oil spill on sea turtles of the GOM was documented in the Final PDARP/PEIS (Deepwater 

Horizon Natural Resource Damage Assessment Trustees, 2016).

4.3.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, the IPFs that may impact sea turtles within the AOI include 

(1) active acoustic sound sources (e.g., airguns; non-airgun HRG sources such as high-resolution 

boomers, sparkers, and CHIRP subbottom profilers; SBESs and MBESs; and side-scan sonars); 

(2) vessel and equipment noise; (3) vessel traffic (i.e., physical disturbance to and risk of collisions); 

(4) aircraft traffic and noise (e.g., helicopters, fixed-wing aircraft); (5) trash and debris (i.e., ingestion 

of and entanglement in); (6) entanglement and entrapment (i.e., with acoustic buoy releases, 

tethered acoustic pingers, nodal tethering lines and towed equipment); and (7) accidental fuel spills.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact level. In contrast, the analysis of impacts 

associated with Alternatives B through G are organized by alternative-specific mitigation measures 

and how each of these measures may reduce impact levels.

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27), based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For sea turtles, the 

below significance criteria have been used to evaluate the level of impact for each IPF.

Nominal impacts to sea turtles include those where no measurable impacts to local 

populations are observed or expected. Nominal impacts are limited to minimal short-term behavioral 

or other low-level impacts on individuals (low numbers, low severity, and short duration). No 
Gulf of Mexico G&G Activities Programmatic EIS 4-127

mortalities or physical injuries are included, and there are no effects on individual fitness (e.g., 

reduction in reproductive success or survivorship) or on populations.

Minor impacts to sea turtles include those that are not extensive or severe, and are 

expected to affect individuals or groups from local populations within the AOI. Minor impacts include 

limited behavioral harassment and small (limited) numbers of physical injuries. These effects 

include only a low likelihood of fitness impacts on a low number of individuals. No mortalities are 

included, and there are no impacts on population rates.

Moderate impacts to sea turtles may be either extensive at the local population level 

(potentially affecting large numbers of individuals within regions of the AOI) but not severe, or they 

may be severe but not extensive. Moderate impacts include significant behavioral harassment and 

physical (including auditory) injuries of more than a low number of individuals, including the 

likelihood of fitness effects on more than a low number of individuals. Moderate impacts also include 

mortality of individuals, including some negative population-level impacts to stable or increasing 

populations, but not outside of the existing known variation around measured population trends (i.e., 

the continued viability of the local population is not threatened and the annual rates of recruitment or 

survival of the local population are not seriously affected). Moderate impacts may include 

(1) mortalities or mortal injuries (i.e., immediate or delayed death [Popper et al., 2014]) in low 

enough numbers that the continued viability of the population is not threatened; (2) disruption of 

critical, time-sensitive behaviors such as nesting, breeding, or the emergence and dispersion of 

hatchlings; and (3) protracted displacement of individual sea turtles from critical habitat.

Major impacts to sea turtles would be extensive and severe. Major impacts would include 

extensive levels of life-threatening or debilitating injury or mortality in sufficiently high numbers that 

the continued viability of the population is threatened, including serious diminishment of annual rates 

of recruitment or survival. Population rates of declining species would be adversely affected, and

population rates of stable or increasing species would be reduced beyond previously measured 

natural variation as a result of mortality or energetic/health impacts from severe behavioral 

harassment and/injury. If there is not enough data to assess trends, or populations are unknown, 

negative population-level effects equate to “major” impacts.

4.3.2.1 Impacts of Routine Activities

4.3.2.1.1 Characteristics of Active Acoustic Sound Sources

Active acoustic sound sources included in the proposed action are airguns and various 

electromechanical sources such as boomers, subbottom profilers, side-scan sonars, and SBESs and 

MBESs. Sound source characteristics are summarized in Table 3.4-2, and detailed characteristics 

and acoustic modeling assumptions are presented in Appendix D. 

Airguns would be used as sound sources during the following oil and gas program activities: 

deep-penetration seismic airgun surveys; VSPs/borehole seismic surveys; and HRG surveys. The 
4-128 Description of the Affected Resources and Impact Analysis

HRG surveys using only electromechanical acoustic sources would be used to support projects or 

surveys in all three program areas.

For this Programmatic EIS, one large airgun array and one small airgun are used to 

represent general configurations and their potential impacts to sea turtles within the AOI 

(Appendix D):

• large airgun array (8,000 in3

) – this array is used to represent sound sources for 

deep-penetration seismic airgun surveys, including 2D, 3D, 4D, WAZ, VSP, and 

other variations; and

• small airgun (90 in3

) – a single airgun is used to represent sound sources for 

some HRG airgun surveys to assess shallow hazards, and benthic habitats at oil 

and gas exploration sites.

Representative broadband source levels are 248 dB zero-to-peak SPL re 1 μPa at 1 m 

measured broadside for the large airgun array and 228 dB zero-to-peak SPL re 1 μPa at 1 m for the 

small array (Table 3.3-2). Although airguns typically have a frequency range between 10 and 

2,000 Hz, most of the acoustic energy is under 600 Hz.

Non-Airgun HRG Survey Activities

Detailed acoustic characteristics of electromechanical sources, including side-scan sonars, 

subbottom profilers, and echosounders, are presented in Appendix D. Sound from 

electromechanical sources other than the boomer and sparker subbottom profilers are not likely to 

be detectable by sea turtles. Boomers have an operating frequency range of 300 to 3,000 Hz and 

may be audible to sea turtles; however, boomers transmit very short pulses of sound (120, 150, or 

180 microsecond [μs]) and at very low source levels. The sound transmitted by boomers typically 

has a 180 dB source level radius of <5 m (16 ft).

Details of each of these electromechanical sound sources and their applications can be 

found in Appendix F, Section 1.3. 

Background: Potential Effects of Noise on Sea Turtles

Few studies have examined the role of acoustic cues in relation to sea turtle ecology 

(Mrosovsky, 1972; Cook and Forrest, 2005; Samuel et al., 2005; Nelms et al., 2016). Sea turtles 

may use sound for navigation, locating prey, avoiding predators, and environmental awareness 

(Dow Piniak et al., 2012a). The few vocalizations described for sea turtles are restricted to the 

grunts and gular (throat) pumps of nesting females, which are low-frequency sounds and are 

relatively loud when compared with ambient noise, leading to speculation that nesting females may 

use these sounds to communicate within species (Mrosovsky, 1972; Cook and Forrest, 2005). 

There are few data on the extent to which sea turtles use their auditory environment (“soundscape”) 

for navigation, environmental assessment, or identification of predators and prey. The ambient 
Gulf of Mexico G&G Activities Programmatic EIS 4-129

acoustic environment for sea turtles changes with each developmental habitat shift. For example, 

the inshore ambient biotic environment where juvenile and adult sea turtles generally reside is 

dominated by low-frequency sound and is noisier than the open ocean environment where 

hatchlings reside (Hawkins and Myrberg, 1983). Moreover, in highly trafficked inshore areas, nearly 

constant low-frequency noises from shipping, recreational boating, and seismic surveys increase the 

potential for acoustic impact (Hildebrand, 2005 and 2009) and may prevent an animal from hearing 

biologically important sounds (Fay, 2009).

Electrophysiological studies on hearing have been conducted on juvenile and subadult green 

sea turtles (Ridgway et al., 1969; Bartol and Ketten, 2006; Dow Piniak et al., 2012a); post-hatchling, 

juvenile, and adult loggerhead sea turtles (Bartol et al., 1999; Lavender et al., 2012 and 2014; Martin 

et al., 2012a); hatchling leatherback sea turtles (Dow Piniak et al., 2012b); and juvenile Kemp’s 

ridley sea turtles (Bartol and Ketten, 2006). Available data (detailed in Appendix I) indicate that 

adult sea turtles in water can hear frequencies ranging from 50 Hz to 1,200 Hz and that juvenile sea 

turtles can hear frequencies up to 1,600 Hz, a range that overlaps with the main energy output from 

seismic airguns (Figure 4.3-4). Reported hearing ranges and thresholds differ somewhat among 

species and life stages but the data are too limited to be definitive because of the low numbers of 

individuals tested.

BOEM concludes that there is incomplete or unavailable information (40 CFR § 1502.22) for 

all sea turtles with respect to (1) seasonal abundances; (2) stock or population size; (3) population 

trends, whether they are increasing, stable, or decreasing; (4) the hearing range; (5) their physiology 

for underwater hearing; and (6) potential impacts from noise. All of these species-specific and 

population variables may be relevant to reasonably foreseeable adverse impacts on sea turtles that 

are subject to active acoustic sound sources, i.e., airguns. However, what is known about the 

biology and hearing physiology of representative species, in combination with observations of 

behavioral response to stimuli, allows inferences and conclusions about reasonably foreseeable 

adverse impacts on sea turtles to be understood with an adequate degree of certainty. BOEM has 

therefore determined that the data or information on sea turtle biology, hearing physiology, seasonal 

abundances, and population stock in the AOI identified as incomplete or unavailable is not essential 

to a reasoned choice among the alternatives, including the No Action alternative.

Moreover, a more complete knowledge base for all types of sea turtles that use the AOI and

that bear on the factors listed above is not available and the acquisition of such information cannot 

be acquired without exorbitant cost. Such information certainly cannot be acquired in a timeframe to 

make it available for this evaluation. While there will never be complete scientific information on sea 

turtles that live in OCS waters, a body of biological and physiological data and information about the 

underwater hearing of representative sea turtles is available to us. These data are sufficient to draw 

inferences and conclusions about the types of sea turtles that are less well understood. Thus, while 

we report where limited data and insufficient knowledge challenge our ability to understand how and 

when specific types of sea turtle species use the AOI and that bear on the factors listed above, 

incomplete or unavailable information does not affect our ability to understand and assign impacts or 

design mitigation strategies. We are able to draw basic conclusions despite incomplete or 
4-130 Description of the Affected Resources and Impact Analysis

unavailable information, discuss results using available scientifically credible information, and apply 

that information using accepted scientific methodologies.

Of the active acoustic sources included in this Programmatic EIS, only airguns, boomers, 

and sparkers produce sounds that are expected to be within the hearing range of sea turtles 

(approximately 50 to 1,200 Hz for adults and up to 1,600 Hz for juveniles; refer to Appendix I). 

Based on the source levels and the reported hearing thresholds of sea turtles in water, these sounds 

could be audible many kilometers away from the source. Other active acoustic sources such as 

side-scan sonars, CHIRP subbottom profilers, and MBESs are not expected to be audible to sea 

turtles and have nominal potential for acoustic impacts. Five categories of effects are discussed 

here: (1) death or auditory injury (including PTS); (2) TTS; (3) auditory masking; (4) behavioral 

responses; and (5) entanglement risk (gear interaction).

Death or Auditory Injury (Including Permanent Threshold Shift)

Death or injury can occur from exposure to high levels of impulsive sound (Popper et al., 

2014). Sea turtle deaths and injuries have been documented in proximity to underwater explosions 

(Klima et al., 1988; Gitschlag and Herczeg, 1994; Viada et al., 2008), but those impacts are 

attributed primarily to barotrauma resulting from exposure to the high energy of the shock wave 

generated by underwater explosions. Based on an extensive review of current scientific literature 

and studies, no sea turtle deaths or injuries are known to have been caused by seismic airguns or 

any of the other active acoustic sources analyzed in this Programmatic EIS. Because of their rigid 

external anatomy, it is possible that sea turtles may be protected to some degree from the impacts of 

lower energy impulsive sounds (Ketten et al., 2005; Popper et al., 2014).

On exposure to noise, the ear’s sensitivity level will decrease to protect the ear from 

damage, a process referred to as hearing threshold shift. Hearing threshold shifts are decreases in 

hearing sensitivity within a certain frequency range (Yost, 2000). Hearing sensitivity normally 

increases and, unless damage to ear structures has occurred, returns to normal over time after 

cessation of noise exposure. Threshold shifts can be temporary (TTS) or permanent (PTS) and can 

consist of a variety of physiological, chemical, and neural phenomena that may or may not recover 

following noise exposure. Several factors influence the type and magnitude of hearing loss, 

including exposure level, frequency content, duration, and temporal pattern of exposure. Several 

mechanical stress or damage (e.g., supporting cell structure fatigue) and metabolic (e.g., inner ear 

hair cell metabolism such as energy production, protein synthesis, and ion transport) processes 

within the auditory system underlie TTS and PTS (Kryter, 1994; Ward, 1997; Yost, 2000). Intense 

sound exposure often results in changes in mechanical processes, whereas prolonged exposure 

typically results in metabolic changes (e.g., Saunders et al., 1985).

Popper et al. (2014) made a distinction between “mortal injury” and “recoverable injury,” with 

the latter defined as an injury that is not likely to result in mortality, such as sensory hair cell 

damage, minor internal or external hematoma, etc. Their definition of “recoverable injury” implicitly 

includes PTS due to permanent inner-ear hair cell damage because the term “recoverable injury” is 
Gulf of Mexico G&G Activities Programmatic EIS 4-131

defined as any injury that is not a mortal injury. Therefore, PTS could be considered a threshold for 

injury, as it has been used for marine mammals (USDOC, NMFS, 2013b).

There are no data upon which to base mortality or injury criteria for sea turtles exposed to 

seismic airgun noise. Popper et al. (2014) concluded that sea turtle hearing is better represented by 

data from fishes than from marine mammals. There are few data on hearing abilities of sea turtles, 

their uses of sound, and their vulnerability to sound exposure; the rationale of Popper et al. (2014) is 

that the hearing range for sea turtles much more approximates that of fishes than of any marine 

mammal, and the functioning of the inner ear of sea turtles (basilar papilla) is dissimilar to that of 

mammals (cochlea). Popper et al. (2014) used data from fishes exposed to pile driving (an 

impulsive source that is not included in this Programmatic EIS) to develop criteria for death or mortal 

injury of sea turtles exposed to airguns. The dual injury criteria were a peak SPL of 207 dB re 1 μPa 

or an SEL of 210 dB re 1 μPa2

•s. The SEL criteria proposed by Popper et al. (2014) and Finneran 

and Jenkins (2012) cannot be directly compared because Popper et al. (2014) did not specify 

frequency weighting. However, the SPL criterion proposed by Popper et al. (2014) is much lower 

(more conservative) even though it is intended to represent a more severe impact (i.e., death or 

mortal injury rather than PTS).

Popper et al. (2014) stated that a “high” risk of recoverable injury in sea turtles would be 

limited to the near field, within tens of meters of an airgun source. The broadband source levels for 

the two representative airgun arrays included in this Programmatic EIS are 231 dB re 1 μPa peak 

SPL for the large airgun array and 210 dB re 1 μPa peak SPL for the small array (refer to 

Chapter 3.3.1.1.1).

Temporary Threshold Shift

The TTS is a temporary reduction in hearing sensitivity caused by exposure to intense sound 

(Popper et al., 2014). It results from temporary changes in sensory hair cells of the inner ear or 

damage to auditory nerves innervating the ear (Liberman, 2015). It is unknown if sea turtles are able 

to regenerate hair cells (Warchol, 2011). When the hair cells cannot be regenerated, PTS occurs.

There are limited TTS data for sea turtles. Lenhardt (2002) exposed captive loggerhead sea 

turtles to airgun pulses in a large net enclosure and measured a TTS of >15 dB in one animal, with 

recovery 2 weeks later. Moein et al. (1995) tested the hearing of 11 loggerhead sea turtles exposed 

to a few hundred pulses from a single airgun and concluded that 5 sea turtles exhibited some 

change in their hearing when tested within 24 hours after exposure; hearing had reverted to normal 

when tested 2 weeks later. The results are consistent with TTS, but unfortunately the received

levels of sound to which the sea turtles were exposed were not reported.

Due to the lack of data on sea turtle hearing and auditory impacts, no quantitative TTS 

criteria have been developed for them. Some previous environmental analyses have applied 

cetacean TTS criteria to sea turtles (U.S. Dept. of the Navy, 1998, 2001, and 2008; USDOI, BOEM, 

2014a). Finneran and Jenkins (2012) developed TTS criteria for sea turtles based on criteria for 
4-132 Description of the Affected Resources and Impact Analysis

low-frequency cetaceans, with the inclusion of an auditory weighting function for sea turtles. No 

criteria were developed for airguns; however, for explosives (the only impulsive source considered), 

dual TTS thresholds for sea turtles consist of a (Type I) weighted SEL of 172 dB re 1 μPa2

•s or a 

peak SPL of 224 dB re 1 μPa.

As in the case for PTS, Popper et al. (2014) did not adopt marine mammal TTS criteria, 

instead concluding that sea turtle hearing is better represented by data from fishes. Although 

Popper et al. (2014) did not define quantitative TTS criteria for sea turtles, they indicated that a 

“high” risk of TTS in sea turtles would be limited to the near field within tens of meters of an airgun 

source, based on predictions derived from effects of impulsive sounds as there are no quantified 

data for the effects of seismic airgun sound on sea turtle hearing.

BOEM concludes that there is incomplete or unavailable information (40 CFR § 1502.22) for 

all sea turtles with respect to (1) seasonal abundances; (2) stock or population size; (3) population 

trends, whether they are increasing, stable, or decreasing; (4) the hearing range; (5) their physiology 

for underwater hearing; and (6) potential impacts from noise. All of these species-specific and 

population variables may be relevant to reasonably foreseeable adverse impacts on sea turtles that 

are subject to active acoustic sound sources, i.e., airguns. However, what is known about the 

biology and hearing physiology of representative species, in combination with observations of 

behavioral response to stimuli, allows inferences and conclusions about reasonably foreseeable 

adverse impacts on sea turtles to be understood with an adequate degree of certainty. BOEM has 

therefore determined that the data or information on sea turtle biology, hearing physiology, seasonal 

abundances, and population stock in the AOI identified as incomplete or unavailable is not essential 

to a reasoned choice among the alternatives, including the No Action alternative.

Moreover, a more complete knowledge base for all types of sea turtles that use the AOI and 

that bear on the factors listed above is not available and the acquisition of such information cannot 

be acquired without exorbitant cost. Such information certainly cannot be acquired in a timeframe to 

make it available for this evaluation. While there will never be complete scientific information on sea 

turtles that live in OCS waters, a body of biological and physiological data and information about the 

underwater hearing of representative sea turtles is available to us. These data are sufficient to draw 

inferences and conclusions about the types of sea turtles that are less well understood. Thus, while 

we report where limited data and insufficient knowledge challenge our ability to understand how and 

when specific types of sea turtle species use the AOI and that bear on the factors listed above, 

incomplete or unavailable information does not affect our ability to understand and assign impacts or 

design mitigation strategies. We are able to draw basic conclusions despite incomplete or 

unavailable information, discuss results using available scientifically credible information, and apply 

that information using accepted scientific methodologies.

Masking

Masking is a reduction in the detectability of a given sound (signal) as a result of the 

simultaneous occurrence of another sound (noise) (Popper et al., 2014). In general, it is recognized 
Gulf of Mexico G&G Activities Programmatic EIS 4-133

that anthropogenic noise “may affect the reception of sound by sea turtles and potentially interfere 

with their communication, to such a degree that it has a negative effect on hatchling survivorship and 

adult communication” (Ferrara et al., 2013). However, the potential for masking impacts on sea 

turtles is difficult to evaluate because the role of sound in their ecology is not known. As described 

in Appendix I, sea turtles can hear low-frequency sounds and have some ability to make sounds. It 

has been hypothesized that the natural sounds of the surf zone may help nesting sea turtles find 

their nesting site (Nunny et al., 2008) and that grunts made by nesting sea turtles may be for 

communication (Cook and Forrest, 2005). Ferrara et al. (2014) identified four types of sounds in 

leatherback sea turtle nests during incubation and hypothesized that sounds are used to coordinate 

group behavior in hatchlings. Recent studies of a freshwater turtle species identified 11 types of 

sounds that are used to synchronize behavior among hatchlings and coordinate the movements of 

hatchlings and adult females (Ferrara et al., 2013).

Electromechanical sources such as side-scan sonars, CHIRP subbottom profilers, and 

MBESs that use frequencies above the estimated hearing ranges of sea turtles are not expected to 

be audible and are expected to have a nominal potential for masking.

Most of the available data on the potential ecological roles of sound for sea turtles are from 

the nesting environment. It is difficult to measure sea turtle sounds offshore and even more difficult 

to infer their ecological roles. The usefulness of sound for communication, and therefore the 

potential for significant masking effects, likely would be limited to areas where multiple individuals 

are present, such as on nesting beaches, in nearshore waters adjacent to nesting beaches, or in 

Sargassum mats inhabited by hatchlings.

Based on the previous discussion, the potential for masking from airguns or 

electromechanical sources using frequencies within sea turtle hearing ranges cannot be 

quantitatively evaluated.

Behavioral Responses

Behavioral responses to seismic airguns, including avoidance, agitation, and diving, have 

been observed for sea turtles in several studies, and are described in detail in Appendix I. Popper 

et al. (2014) provided a qualitative assessment of the behavioral responses of sea turtles to airguns. 

Based on observations of sea turtle response to impulsive sound, they predicted a “high” risk 

(likelihood) of behavioral responses in the near field (tens of meters), a “moderate” risk at 

intermediate distances (hundreds of meters), and a “low” risk in the far field (thousands of meters) of 

impulsive sound sources.

Experimental studies by O’Hara and Wilcox (1990) and Moein et al. (1995) investigated the 

use of airguns to repel sea turtles from hopper dredges. O’Hara and Wilcox (1990) reported that sea 

turtles maintained a distance of 30 m (98 ft) from a single operating airgun. The received level of 

sound generated by the airguns at a distance of 30 m (98 ft) was not determined; McCauley et al. 

(2000a) later estimated it to be 175 to 176 dB re 1 μPa peak SPL. However, actual sound levels 
4-134 Description of the Affected Resources and Impact Analysis

received by the sea turtles may have been slightly <175 to 176 dB because calculations by 

McCauley et al. (2000a) did not consider the shallow airgun depth (NSF and USDOI, GS, 2011). 

Moein et al. (1995) exposed loggerhead sea turtles to received levels of 175, 177, and 179 dB re 

1 μPa, and avoidance behavior was observed upon first exposure; however, after three separate 

exposures to the airguns, the sea turtles stopped responding (i.e., avoidance behavior was no longer 

observed).

McCauley et al. (2000a) examined the response of caged sea turtles (1 green sea turtle and 

1 loggerhead sea turtle) as a single airgun approached and departed. The sea turtles showed a 

noticeable increase in swimming behavior when the received level was higher than 166 dB re 1 μPa 

rms and became erratic and increasingly agitated at received levels >175 dB re 1 μPa. Because 

these animals were caged, avoidance behavior could not be monitored. However, the researchers 

speculated that avoidance would occur at 175 dB re 1 μPa rms (McCauley et al., 2000a).

Lenhardt (2002) exposed captive loggerhead sea turtles contained within a large net 

enclosure to airgun pulses. At received levels of 151 to 161 dB re 1 μPa, the sea turtles were found 

to increase swimming speeds, and an avoidance response was observed initially near a received 

level of approximately 175 dB re 1 μPa.

Avoidance of airgun impulsive sound by sea turtles has also been inferred from field 

observations of sea turtle behavior during seismic surveys (Holst et al., 2007; Weir, 2007; DeRuiter 

and Doukara, 2012). Holst et al. (2007) analyzed monitoring data from 11 seismic surveys and 

found that, for large-scale surveys, the nearest point of approach for sea turtles was closer during 

periods of airgun silence (139 m [456 ft]) than when the airguns were firing (228 m [748 ft]). Weir 

(2007) reported that fewer sea turtles were observed near airgun arrays when they were firing than 

when they were not firing; however, there was no obvious behavioral avoidance (e.g., swimming 

away) and the increase in the level of impulsive sound during approach of the vessel may have 

contributed to the response. DeRuiter and Doukara (2012) observed that basking loggerhead sea 

turtles exhibited a startle response (rapid dive) at a median distance of 130 m (427 ft) in response to 

the approach of an airgun array. The maximum distance at which a sea turtle dove was 839 m 

(2,753 ft), corresponding to a received level of 175 dB re 1 μPa peak. Although the approach of the 

ship may have been a factor, the analysis strongly suggested that airgun impulsive sound was the 

cause of the response.

Behavioral responses of sea turtles to airgun pulses may not be limited to the avoidance, 

agitation, and diving behavior that have been observed so far. The range of behaviors is limited in 

controlled experiments, and shipboard visual observers during seismic surveys cannot see the 

movements of submerged sea turtles. DeRuiter and Doukara (2012) speculated that startle 

responses could have negative fitness consequences for individual sea turtles if it interfered with 

thermoregulation, caused inhabitual energy expenditures, or excluded sea turtles from optimal 

habitat. The greatest potential for significant effects of behavioral disruption would be during nesting 

or hatchling emergence in nearshore reproductive habitat adjacent to nesting beaches.
Gulf of Mexico G&G Activities Programmatic EIS 4-135

Based on the best available data, it is assumed that sea turtle behavioral responses to 

airgun impulsive sound may occur at a received level between 166 and 179 dB re 1 μPa. The 

broadband source levels of airguns used for sound field modeling to analyze potential impacts to 

resources are 248 dB re 1 μPa at 1 m0-peak for a large airgun array (8,000 in3

) and 228 dB re 1 μPa 

at 1 m0-peak for the single airgun (90 in3

) (refer to Table 3.4-2).

In addition to airguns, boomers are the only other active acoustic source that may be audible 

to sea turtles. Electromechanical sources such as side-scan sonars, CHIRP subbottom profilers, 

and MBESs that use frequencies above the estimated hearing ranges of sea turtles are not expected 

to be audible and are expected to have a nominal potential for behavioral effects. Boomers have 

very short pulse lengths and a low source level (refer to Appendix D). Therefore, the potential for 

behavioral responses, if they occurred, probably would be limited to very near the source.

Entanglement Risk

Albeit small, the risk for gear interaction is present. Sea turtles can become entangled in 

some types of lines associated with G&G activities. The G&G permit applications and site-specific 

environmental assessment set conditions of approval with each activity that would minimize specific 

impacts caused by gear interactions. With the implementation of mitigations, impacts would be 

expected to be nominal. 

4.3.2.1.2 Analysis of Active Acoustic Sound Sources

Deep-Penetration Seismic Airgun Survey Activities

Based on the scope of the proposed action, seismic airgun surveys could affect individuals 

from all sea turtle species within the AOI. Surveys conducted within Federal coastal waters could 

affect all species and greater numbers of individuals than deepwater surveys. Deepwater surveys 

are likely to affect fewer individual sea turtles, with impacts generally limited to adult leatherback and 

loggerhead sea turtles as well as hatchlings and oceanic stage juveniles that are associated with 

floating Sargassum mats and other flotsam. Surveys conducted during summer sea turtle nesting 

periods within Federal coastal waters may affect greater numbers of adult sea turtles, particularly 

loggerhead, green, and Kemp’s ridley sea turtles, than surveys conducted during non-nesting 

periods. Designated critical habitat for hatchling loggerhead turtles (“Sargassum Habitat”) is shown 

in Figure 4.3-3 and includes offshore waters of the EPA as well as most of the CPA and WPA. The 

spatiotemporal distribution and density of Sargassum mats and weed lines in the GOM is dynamic 

and may vary seasonally and annually (79 FR 39856). Therefore, it is difficult and impractical to use 

the entire designated Sargassum critical habitat as an area to protect from project-related IPFs.

Subadult and adult sea turtles may be more likely to be affected by seismic airgun noise than 

hatchling and juvenile sea turtles because of the greater time that adults and subadults spend 

submerged and at depth. Hatchling and oceanic stage juvenile sea turtles generally reside at or 

very near the sea surface and dive to shallow depths (Salmon et al., 2004; Witherington et al., 

2012), so they may be less likely to be injured by the sound field produced by an airgun array during 
4-136 Description of the Affected Resources and Impact Analysis

a survey because of the destructive interference of waterborne seismic signals at the sea surface 

due to the “Lloyd mirror” (image interference) effect (Urick, 1983). However, the reflection of 

impulsive sound at the sea surface is complex and any sound exposure benefit to animals located

near the surface will be hard to accurately predict. The close association of hatchling and oceanic 

stage juvenile sea turtles with dense Sargassum may also provide some absorption and attenuation 

of impulsive sound.

Alternative A includes operational mitigation measures that, as described in Chapter 2.1.2 

and Appendix B, would be implemented during seismic airgun surveys. These measures include 

the establishment of a 500-m (1,640-ft) exclusion zone, visual monitoring by qualified PSOs, and 

ramp-up requirements (implementation of PSO Program and the Seismic Airgun Survey Protocol). 

The purpose of the mitigation measures is to prevent serious injury to sea turtles (and marine 

mammals) by providing a warning and giving them the opportunity to move from the area where 

sound levels will be high or to avoid exposing them to high-intensity impulsive sounds when they are 

present within an established exclusion zone around an airgun array. However, under Alternative A, 

these measures are required only for seismic airgun surveys in water depths >200 m (656 ft) in the 

WPA and CPA and in all water depths in the EPA. Most sea turtle species (with the exception of 

leatherback, hatchling loggerhead, and possibly Kemp’s ridley sea turtles) within the AOI are 

distributed within the waters of the continental shelf (i.e., at depths <200 m [656 ft]). This mitigation 

measure would benefit leatherback sea turtles in areas with depths >200 m (656 ft). It is not likely 

that hatchling and oceanic stage juvenile sea turtles would be sighted by PSOs. Therefore, most 

sea turtles within the WPA and CPA that are distributed on the continental shelf do not benefit from 

this mitigation measure, but impacts to those life stages may be reduced by their epipelagic habits 

and close association with Sargassum as discussed above.

Although these mitigation measures require clearance of the exclusion zone for sea turtles 

prior to start-up, they do not require shutdown for sea turtles; consequently, some individual sea 

turtles may be exposed to sound levels that could lead to TTS or PTS. In areas where the measures 

will be used, it is assumed that there will be little potential for deaths or life-threatening injuries from 

airgun activities. The protocols, however, would not prevent auditory injury or behavioral 

disturbances to sea turtles at distances beyond the exclusion zone. As noted previously, avoidance 

reactions by sea turtles to seismic signals have been observed at received SPLs between 166 and 

179 dB re 1 μPa (Moein et al., 1995; McCauley et al., 2000b).

Under Alternative A, it is estimated that, over the 10-year time period (Table 3.2-1), a total of 

561 VSP surveys will be conducted within the AOI: 128 in the WPA (annual mean = 12.8); 419 in 

the CPA (annual mean = 41.9); and 14 in the EPA (annual mean = 1.4). The estimated number of 

VSP surveys was highest for deepwater areas of the WPA and CPA. Estimates for the number of 

surveys that might be conducted during a 40-year period were not available for this analysis.

Active acoustic sources used for VSP surveys operate at frequencies between 10 and 

2,000 Hz, with most energy generated at frequencies below 200 Hz (Table 3.3-2). As discussed in 

Appendix F, Section 1.1.5, the defining characteristic of a VSP survey (of which there are several 
Gulf of Mexico G&G Activities Programmatic EIS 4-137

types) is that the energy source is deployed near a borehole that contains seismic receivers. During 

the survey, the sound source is stationary or operated from a limited number of discrete locations 

from the borehole and, therefore, the acoustic footprint of a VSP survey is restricted to an area 

surrounding a borehole. In addition, VSP surveys usually are short in duration and are often 

completed in less than a few days, the exception being SVWD VSP surveys. It is expected that VSP 

surveys will contribute to ambient acoustic noise levels encountered by sea turtles in the AOI, 

although noise from expected G&G operations would be survey- or activity-based, occurring on a 

transient and intermittent basis over the 10-year period of interest.

Detection of sea turtles by visual monitoring during seismic airgun surveys can be difficult, 

even for experienced observers. Sighting rates for all sea turtles during seismic mitigation surveys 

was low (0.003 sea turtle sightings per survey hour), which likely reflects both the lower densities of 

sea turtles and the sighting difficulty for many of the species (Barkaszi et al., 2012). Most life stages 

of sea turtles likely to be found in the AOI tend to aggregate in mats or weedlines of floating 

vegetation (e.g., Sargassum) and in other flotsam within or near zones of ocean current 

convergence; however, because of their small size and cryptic coloration, it is unlikely that their 

presence would be detected by PSOs during seismic surveys. It is uncertain if sea turtles would 

move away from an approaching seismic source during a survey or during ramp-up of an array prior 

to initiation of a survey. Observations of sea turtle behavior in response to impulsive sound 

generated by seismic airguns off Angola by Weir (2007) were not adequate to draw conclusions 

about the behavioral response of sea turtles to airgun impulsive sound. There was some indication 

that fewer sea turtles were seen during full-array survey activity, but there was no obvious behavioral 

avoidance of the airgun array by sea turtles. Weir (2007) claimed that sea turtles observed basking 

on the surface may not have been able to move away rapidly (on the sea surface) from approaching 

airguns even if motivated to do so because their responses to approaching objects while resting on 

the sea surface are normally slow. From the observer records in Barkaszi et al. (2012), 25 percent 

of the recorded behaviors in sea turtles showed a dive response to the vessel or equipment. A sea 

turtle’s response could include diving to depths below the airgun array, which could increase the 

likelihood of possible auditory impacts. It has long been assumed that early life history stages of sea 

turtles associated with Sargassum habitats were largely or entirely passive drifters, with little 

potential for directed movements towards or away from stimuli. Recent work by Putman and 

Mansfield (2015) has demonstrated active dispersal of early life stages in the GOM, which 

demonstrates at least a potential for active swimming to avoid adverse stimuli.

Based on this discussion, the most likely impacts to sea turtles would be short-term 

behavioral responses of individuals in closer proximity to operating airgun arrays. In cases where 

individual sea turtles cannot or do not avoid airgun arrays and are not detected by visual observers, 

TTS or PTS auditory injuries could occur, but the potential for mortality or life-threatening injuries is 

unlikely and would be limited to the very near field. Seismic airgun surveys proposed under 

Alternative A would not be expected to result in long-term or permanent displacement of sea turtles 

from any areas within the AOI, including open ocean habitats and preferred coastal habitats such as 

seagrass beds, nearshore or inshore hard substrate habitats, or embayments.
4-138 Description of the Affected Resources and Impact Analysis

Seismic airgun surveys conducted offshore of heavily used nesting beaches during the 

nesting season within the AOI (April through July or August) could temporarily displace breeding and 

nesting adult sea turtles and disrupt time-critical activities. Within the AOI, these include nesting 

habitats for Kemp’s ridley sea turtles along the Texas coast and west coast of Florida, and for 

loggerhead and potentially Kemp’s ridley and green sea turtles along the Mississippi, Alabama, and 

northwest Florida coasts (WIDECAST, 2015). Critical habitat for hatchling loggerhead sea turtles 

within the AOI is shown in Figure 4.3-3 and includes discrete “Nearshore Reproductive Habitats” in 

Florida (Florida Keys to the Gulf Island National Seashore), Alabama, and Mississippi, and 

“Sargassum Habitat,” which includes a large percentage of the AOI. Many adult females linger near 

the nesting beaches before and between nesting events, resting under rocky ledges and outcrops, 

or partially burying themselves in soft sediments within inner shelf waters for weeks. Depending on 

many factors, including (1) the distance of the survey from shore, (2) local factors such as seafloor 

topography and seafloor substrate that affect the propagation of underwater sound, and (3) the 

duration and intensity of survey effort in this area, it is possible that breeding adults, nesting adult 

females, and hatchlings could be exposed to airgun seismic survey-related sound exposures. 

Because of the potential for propagation of higher levels of impulsive sound into shallower water, 

individual sea turtles could be exposed to higher levels of sound. Potential impacts could include 

auditory injuries to and dispersion of breeding or nesting adults, as well as the possibility of some 

auditory impacts to hatchlings.

Overall, the potential impacts to sea turtles within the AOI from airgun noise are not expected 

to result in substantial changes to behavior, growth, survival, annual reproductive success, or 

lifetime reproductive success (fitness). Due to limited seismic survey protocols within the AOI (i.e., 

no protocols required within shelf waters of the WPA and CPA), it is assumed that most impacts 

would consist primarily of behavioral disturbances, as well as some TTS- and PTS-level auditory 

impacts. No lethal impacts or population-level impacts from PTS auditory injuries are likely or 

expected. Because of the distance of operations from nesting beaches, disruption of critical timesensitive behaviors such as nesting, breeding, or the emergence and dispersion of hatchlings, and 

protracted displacement of individual sea turtles from critical habitat are not expected. From this 

analysis, the mitigation measures that would be implemented, and considering the impact 

significance criteria (Chapter 4.3.2), seismic airgun survey impacts to sea turtles would be minor. 

Non-Airgun HRG Survey Activities

Non-airgun HRG survey activities that are associated with Alternative A would use only 

electromechanical sources such as boomer, sparker, and CHIRP subbottom profilers; side-scan 

sonar; and MBESs. As discussed in Appendix F, Section 1.3, the frequency ranges of these 

sources used for this analysis are as follows: 

• pinger (2,000 Hz);

• sparker (50 to 4,000 Hz);

• boomer (300 to 3,000 Hz);
Gulf of Mexico G&G Activities Programmatic EIS 4-139

• CHIRP subbottom profiler (4 to 24 kHz);

• side-scan sonar (usually 16 to 1,500 kHz);

• SBES (12 to 240 kHz); and

• MBES (50 to 400 kHz).

According to the ScOT report results (Appendix G), acoustic outputs from electromechanical 

sources other than the boomer and sparker are not likely to be detectable by sea turtles, whose best 

hearing is below 1,200 Hz for adults and 1,600 Hz for juveniles (Appendix I). If these sources are 

used and operated at a frequency within the hearing range of sea turtles, there could be soundrelated impacts (mostly behavioral effects and perhaps some TTS-related impacts). However, the 

use of these active sound sources with outputs outside of the adult sea turtle hearing range of 50 to 

1,200 Hz (up to 1,600 Hz for juvenile sea turtles) during the proposed activity is expected to have no 

impact to sea turtles within the AOI.

Boomer or sparker subbottom profilers have operating frequency ranges of 300 to 3,000 Hz 

and 50 to 4,000 Hz, respectively, and so may be audible to sea turtles; however, they have very 

short pulse lengths (120, 150, or 180 μs) and at very low source levels. Under Alternative A, there 

are no mitigation measures that include non-airgun HRG survey protocols.

The potential impacts from electromechanical sources using frequencies within the hearing 

ranges of sea turtles are not expected to result in changes to behavior, growth, survival, annual 

reproductive success, or lifetime reproductive success (fitness) to most individuals. Most impacts 

would likely be limited to behavioral disturbances and TTS level auditory impacts. Individual sea 

turtles may experience long-term auditory injuries (PTS), but they would have to be very close to the 

electromechanical source to experience sound levels capable of causing PTS injuries. In the case 

of non-airgun HRG survey activities using electromechanical sources within the hearing range of sea 

turtles, no lethal impacts and no population-level impacts from PTS auditory injuries are expected. 

From this analysis, non-airgun HRG survey impacts to sea turtles are expected to range from 

nominal to minor. 

4.3.2.1.3 Vessel and Equipment Noise

Underwater noise generated by G&G vessels could disturb sea turtles or contribute to 

auditory masking during the project period. As discussed in Chapter 3.3.1.3, vessel noise is a 

combination of narrow band (tonal) and broadband sound (Richardson et al., 1995). Narrow band 

tones typically dominate up to 50 Hz, whereas broadband sounds may extend to 100 kHz. The 

dominant source of underwater noise generated by vessels is from propulsion gear, primarily 

propeller operation. The intensity of this noise is largely related to vessel size and speed. Vessel 

and equipment noise from G&G vessels, including survey and support vessels associated with 

activities described in the proposed action, would produce low levels of noise. Broadband source 

levels for most small ships (a category that would include seismic survey vessels and support 

vessels for drilling of COST wells or shallow test wells) are anticipated to be in the range of 170 to 
4-140 Description of the Affected Resources and Impact Analysis

180 dB re 1 μPa at 1 m, and source levels for smaller boats (a category that would include survey 

vessels for renewable energy and marine minerals sites) are in the range of 150 to 170 dB re 1 μPa 

at 1 m (Richardson et al., 1995).

Vessels associated with various activities under the proposed action are discussed in 

Chapters 3.2 and 3.3 and listed in Table 3.2-7. Vessels conducting oil and gas G&G deeppenetration seismic airgun surveys (2D, 3D, and 4D surveys) are approximately 100 m (328 ft) in 

length and would account for most of the proposed survey miles traveled. Other oil and gas activity 

vessels range from 20 to 100 m (66 to 328 ft) in length. Renewable energy activity vessels range 

from 20 to 100 m (66 to 328 ft) in length, and marine mineral activity vessels range from 20 to 30 m 

(66 to 98 ft) in length. Under Alternative A, deep-penetration seismic airgun surveys could occur 

anywhere within the AOI. Most seismic airgun surveys, however, will occur in deepwater areas of 

the CPA throughout the project period (Table 3.2-2). One to three diesel-powered survey and 

support vessels are expected to be associated with conventional 2D and 3D NAZ surveys. The 

WAZ surveys generally involve multiple vessels operating in concert in a variety of vessel 

geometries, and each WAZ vessel would have several support vessels (Appendix F, Section

1.1.4). In general, large seismic vessels will remain offshore for weeks or months, receiving fuel, 

supplies, and crew via smaller support vessels and helicopters. Traffic associated with support 

vessels and helicopters is provided in Table 3.2-7. 

The most likely effects of vessel and equipment noise on sea turtles would include 

behavioral changes and auditory masking. Vessel and equipment noise is transitory and generally 

does not propagate great distances from the vessel, and the source levels are too low to cause 

death or injuries such as auditory threshold shifts. Based on existing studies on the role of hearing 

in sea turtle ecology, it is unclear whether masking resulting from vessel and equipment noise would 

impact sea turtles. Behavioral responses to vessels have been observed but are difficult to attribute 

exclusively to noise rather than to visual or other cues. Nevertheless, it is conservative to assume 

that noise associated with G&G survey and support vessels may elicit behavioral changes in 

individual sea turtles near the vessels. It is assumed that these behavioral changes would be limited 

to evasive maneuvers such as diving, changes in swimming direction, or changes in swimming 

speed to distance themselves from vessels. This evasive behavior is not expected to adversely 

affect these individuals or local populations; impacts under Alternative A would be nominal. 

Geotechnical surveys include measuring conductivity, pressure, and temperature; geologic 

coring; and grab sampling. Sediment sampling and testing locations for geotechnical surveys are 

guided by geophysical data and maps generated during HRG surveys. The acoustic characteristics 

of these sources are discussed in Appendix D and are expected to be outside the hearing range of 

sea turtles. Noise produced during use of these devices is not expected to affect sea turtles in the 

AOI.

Other sound sources associated with geotechnical surveys under Alternative A include the 

drilling of potentially one COST well and up to two shallow test wells in AOI during the time period of 

this Programmatic EIS. As discussed in Chapter 3.3.1.2.2, noise from drilling operations includes 
Gulf of Mexico G&G Activities Programmatic EIS 4-141

strong tonal components at low frequencies (<500 Hz), including infrasonic frequencies in at least 

some cases (Richardson et al., 1995). Machinery noise can be continuous or transient and can be 

variable in intensity. Noise levels vary with the type of drilling rig (as shown below) and water depth 

(Wyatt, 2008).

Equipment Bandwidth 

(kHz)

Source Level 

(dB re 1 μPa)

Jack-up platform 0.005 119-127

Semisubmersible platform 0.01-10 154

Drillship 0.01-1 125-195

Because of the very low sound frequencies produced by drilling equipment operated from 

jack-up platforms, it is likely that drilling activities from these platforms may be inaudible to sea 

turtles because the drilling equipment is not directly coupled with the water. In contrast, it is likely 

that drilling-related sounds from semisubmersible drilling vessels would be audible to sea turtles.

Dynamic positioning (DP) is a computer-controlled system to automatically maintain a 

vessel’s position and heading by using its propellers and thrusters. Vessel types that employ DP 

include ships and semisubmersible mobile offshore drilling units. The DP thrusters produce 

broadband noise (e.g., 137 dB rms at 405 m) at bandwidths between 100 Hz and 10 kHz (McCauley, 

1998). Drilling and DP-related noise is continuous, and it is expected that the sound generated by 

DP use may elicit behavioral responses in sea turtles, such as temporary avoidance or displacement 

of individual sea turtles from some radius around the drilling area. Studies of sea turtles in the 

proximity of platforms are not conclusive on whether the sea turtles may habituate to the continuous 

sound source. During the timeframe of this Programmatic EIS, it is anticipated that very few drilling 

activities will occur (potentially only 1 COST well and up to 2 shallow test wells). Therefore, impacts 

to sea turtles from drilling-related noises associated with the proposed activity would be nominal. 

4.3.2.1.4 Vessel Traffic

As presented in Table 3.2-7, 19,689 support vessel trips and 993 survey vessel trips are 

estimated for proposed operations within the AOI over the 10-year period. Most trips will occur 

within the CPA and WPA because the highest level of activity is projected there (Table 3.2-1). Very 

few vessel trips are expected to occur within the EPA during the 10-year period. The G&G survey 

vessels could strike and injure or kill sea turtles because it is difficult for PSOs to detect sea turtles 

under the best observational conditions, much less when the water surface is rough or other 

conditions occur that inhibit visual detection of smaller animals such as sea turtles. In addition, it is 

difficult to maneuver a survey vessel towing airgun arrays to avoid sea turtles that may be detected. 

Propeller and hull collision injuries to sea turtles resulting from interactions with boats and ships are 

common, and the problem of vessel strikes on sea turtles is an increasing concern, especially in 

certain areas (such as the southeastern U.S.) where increased development along the coasts is 

likely to result in increased recreational boat traffic (Hazel and Gyuris, 2006; Hazel et al., 2007). 

From 1997 to 2005, 14.9 percent of all stranded loggerhead turtles in the U.S. Atlantic Ocean and 

GOM were documented as having sustained some type of propeller or vessel collision injury. This 
4-142 Description of the Affected Resources and Impact Analysis

study, however, did not indicate what proportion of observed injuries were post- or ante-mortem 

(USDOC, NMFS and USDOI, FWS, 2008).

Sea turtles may be able to actively maneuver within the water column to avoid collisions with 

approaching slow-moving (4.5 kn; 5.2 mph) survey vessels; however, support vessels travel at much 

faster speeds, and sea turtles may not be able to avoid them. Based on knowledge of their sensory 

biology (Bartol and Musick, 2003; Levenson et al., 2004; Bartol and Ketten, 2006a; Moein-Bartol and 

Ketten, 2006), sea turtles may detect objects such as vessels, prey, and predators in the water 

column by means of auditory and visual cues. However, research examining the ability of sea turtles 

to avoid collisions with vessels shows they may rely more on visual than auditory cues (Hazel et al., 

2007). There have been no documented sea turtle collisions with vessels that supported offshore 

operations during the past 40 years of OCS oil and gas operations (USDOC, NMFS, 2007). It is 

likely that collisions with small or submerged sea turtles, or during nighttime or periods of poor 

visibility, may go undetected and undocumented. Mortalities from vessel collisions outside shallow 

coastal and inshore waters are poorly documented, as sea turtles are negatively buoyant and 

remains sinking in deep water are very unlikely to be recovered (Stacy, official communication, 

2015). Under Alternative A, all authorizations for shipboard surveys would include guidance for 

vessel strike avoidance (i.e., NTL 2016-BOEM-G01), which applies to all existing and future oil and 

gas operations on the Gulf of Mexico OCS. The guidance protocols are discussed in Appendix B, 

Section 1. However, during nighttime and because of the relatively small size of sea turtles, some 

individuals will go unobserved and may be struck by a vessel. Seismic vessels, which account for 

most of the project-related vessel traffic associated with Alternative A activities, survey at a speed of 

approximately 4.5 kn (5.2 mph), a speed at which all life stages of turtles present in the AOI, except 

hatchlings, would have the ability to avoid collision. In addition, waters surrounding survey vessels 

would be monitored by PSOs during daylight operations for the presence of sea turtles. It is 

anticipated that collisions between seismic survey vessels (when collecting data) and sea turtles 

during daylight hours would be unlikely.

Seismic vessels and survey support vessels (e.g., supply vessels and chase boats) usually 

operate at higher speeds (~10 to 12 kn; 12 to 14 mph) during transits than when collecting data 

during surveys. The potential for collisions between these vessels and sea turtles, particularly at 

night and during inclement weather, would be unlikely but possible, and a few individual sea turtles 

are expected to be at risk of injury or mortality over the duration of the action. While mortality from 

vessel collision is frequently documented in sea turtle stranding data, the issue is most prevalent in 

shallow inshore and near coastal waters with high densities of high-speed vessel traffic (Singel et al., 

2007). Considering the above analysis, it is expected that potential impacts to sea turtles within the 

AOI from vessel traffic would be nominal; however, in the unlikely event a sea turtle is struck and 

injury or mortality occurs, impacts would be moderate. 

4.3.2.1.5 Aircraft Traffic and Noise

Aircraft traffic and noise would result from remote-sensing surveys (aeromagnetic surveys) 

and helicopter support during drilling of COST wells, shallow test wells (Chapter 3.2.1), and support 
Gulf of Mexico G&G Activities Programmatic EIS 4-143

and service during deep-penetration seismic airgun surveys. BOEM anticipates that one 

aeromagnetic survey may be conducted in the AOI during the time period covered by this

Programmatic EIS (Chapter 3.2.1.2). Helicopter flights will be used to conduct crew changes for 

larger seismic vessels; the number of anticipated transits is provided in Table 3.2-7 and discussed in 

Chapter 3.3.1.4. Remote-sensing surveys associated with oil and gas exploration and development 

activities would include aeromagnetic surveys (Appendix F, Section 1.5). The surveys would be 

conducted by fixed-wing aircraft flying at speeds of approximately 135 kn (155 mph) (Reeves, 2005). 

Most offshore aeromagnetic surveys are flown at altitudes between 61 and 152 m (200 and 500 ft). 

It is expected that a typical aeromagnetic survey may require 1 to 3 months to complete. Potential 

impacts to sea turtles from aircraft traffic include noise and physical (visual) disturbance.

Noises generated by project-related survey aircraft that are directly relevant to sea turtles 

include both airborne sounds to individuals on the sea surface and underwater sounds from air-towater transmission from passing aircraft. Both helicopters and fixed-wing aircraft generate noise 

from their engines, airframe, and propellers. The dominant tones for both types of aircraft generally 

are below 500 Hz (Richardson et al., 1995) and within the auditory range of sea turtles (Appendix I). 

The transmission of aircraft noise into water depends on aircraft altitude, the aspect (direction and 

angle) of the aircraft relative to the receiver, and sea surface conditions. The level and frequency of 

transmitted sounds propagating through the water column are affected by water depth and seafloor 

type (Richardson et al., 1995). Because of the expected airspeeds and these physical variables, 

noise (airborne and underwater) generated by G&G survey aircraft is expected to be brief in 

duration.

The physical presence of low-flying aircraft can disturb sea turtles, particularly those on the 

sea surface. Behavioral responses to flying aircraft include diving or abrupt changes in swimming 

speed or direction. It is projected that 7,497 helicopter trips would occur over the 10-year period. 

Considering the relatively small number of aeromagnetic surveys, COST wells, and shallow test 

wells associated with the proposed activity, along with the short duration of potential exposure of 

aircraft-related noise and physical disturbance to sea turtles because of aircraft airspeed, it is 

expected that potential impacts to sea turtles within the AOI from this activity would be nominal. 

4.3.2.1.6 Trash and Debris

While the release of trash and debris are not considered routine activities, the potential for 

release is considered as a part of routine activities. Trash and debris poses two types of negative 

impacts to sea turtles: (1) entanglement and (2) ingestion. Entanglement in trash and debris, 

particularly buoyant trash and debris, can pose a significant hazard to sea turtles. The USDOC, 

NMFS and USDOI, FWS (2008) noted that loggerhead sea turtles have been found entangled in a 

wide variety of materials, including steel and monofilament line, synthetic and natural rope, plastic 

onion sacks, and discarded plastic netting. From 1997 to 2005, 1.6 percent of stranded loggerhead 

sea turtles found on Atlantic and GOM beaches were entangled in fishing gear. Monofilament line 

appears to be the principal source of entanglement for loggerhead sea turtles in U.S. waters (0.9%; 

1997 to 2005 average), followed by pot/trap line (0.4%; 1997 to 2005 average) and fishing net 
4-144 Description of the Affected Resources and Impact Analysis

(0.3%; 1997 to 2005 average). Less than 1 percent of stranded sea turtles in 2005 were found 

entangled in other trash and debris (USDOC, NMFS, unpublished data, as cited in USDOC, NMFS 

and USDOI, FWS, 2008).

In addition, debris item(s) may be mistaken for food and ingested, or debris items may be 

ingested accidentally with other food. Debris ingestion may lead to loss of nutrition, internal injury, 

intestinal blockage, starvation, and death (USDOC, NOAA, 2015b). The habitat association of 

oceanic phase juvenile sea turtles with Sargassum makes them particularly vulnerable to impacts 

from the ingestion of trash and debris. The oceanic convergence zones that concentrate Sargassum

also concentrate other buoyant materials, notably including plastics and tar (Thiel and Gutow, 2005). 

Dietary samples collected by esophageal lavage from 42 oceanic-stage juvenile Kemp’s ridley, and 

green sea turtles associated with Sargassum in the GOM revealed that 67 percent of the sea turtles 

sampled contained plastics and that plastics averaged 13 percent of the total dry weight of collected 

samples (Witherington et al., 2012).

The MARPOL is the main international convention covering prevention of pollution of the 

marine environment by ships from operational or accidental causes. The MARPOL includes 

regulations aimed at preventing and minimizing pollution from ships (both accidental pollution and 

from routine operations) and currently includes six technical Annexes. Special Areas with strict 

controls on operational discharges are included in most Annexes. Annex V (Prevention of Pollution 

by Garbage from Ships) addresses different types of garbage and specifies the distances from land 

and the manner in which they may be disposed; the most important feature of the Annex is the 

complete ban imposed on the disposal of all forms of plastics into the sea. The revised Annex V 

prohibits the discharge of all garbage into the sea, except as provided otherwise. All other trash and 

debris must be returned to shore for proper disposal with municipal and solid waste.

The G&G survey operations associated with Alternative A will generate trash made of paper, 

plastic, wood, glass, and metal. In addition to adherence to the revised provisions of MARPOL 

Annex V, USCG and USEPA regulations require operators to become proactive in avoiding 

accidental loss of solid waste items by developing waste management plans, posting informational 

placards, manifesting trash sent to shore, and using special precautions such as covering outside 

trash bins to prevent accidental loss of solid waste. Under Alternative A, all authorizations for 

offshore G&G activities would include guidance for the handling and disposal of trash and debris 

(NTL 2015-BSEE-G03).

Taking into account the USCG and USEPA’s regulations, as well as BSEE guidance, trash 

and debris from G&G activities released into the marine environment will be minimized. Debris 

would consist only of isolated items that were accidentally lost overboard. Therefore, debris 

entanglement and ingestion impacts on sea turtles are expected to be nominal. 
Gulf of Mexico G&G Activities Programmatic EIS 4-145

4.3.2.1.7 Entanglement/Entrapment

Sources of entanglement hazards in the proposed action that may impact sea turtles within 

the AOI include placement of anchors, nodes, cables, sensors, or other equipment on or in the 

seafloor for various activities within the oil and gas program.

Acoustic buoy releases, tethered acoustic pingers, and nodal tethering lines pose an 

entanglement risk to sea turtles and other marine life. Entanglement is possible with OBC surveys, 

which are discussed in Appendix F, Section 1.1.3. The deployment of nodes and cables is 

accomplished using an ROV, by dropping nodes on a tether, or by laying cables off the back of a 

layout boat. According to BOEM (USDOI, BOEM, 2013e), as of 2013, there was only one reported 

sea turtle entanglement incident during a seismic survey nodal survey.

According to BOEM (USDOI, BOEM, 2013e), risks of entanglement to sea turtles may be 

reduced by implementing the following measures: (1) shortening acoustic buoy and tethered 

acoustic pinger lines to the shortest length practical; and (2) replacing tether rope lines <0.25 inches 

in diameter with a thicker more rigid tether line or modifying the line by tying knots along its length to 

increase the diameter and rigidity. Additional measures include having a PSO on board vessels 

during tethered node retrieval operations. The PSOs will document any entanglement of marine 

species in the nodal gear, specifically noting the location where entanglement occurred (e.g., pinger 

tether, acoustic buoy line). The PSO must also contact the sea turtle stranding network State 

coordinator to report the incident and condition of the sea turtle, and request additional instructions 

to reduce risk of injury or mortality, including rehabilitation and salvage techniques.

Towed seismic equipment for 2D, 3D, 4D and WAZ surveys pose an entrapment risk to sea 

turtles. Due to the large footprint of the towed equipment and the general low maneuverability of sea 

turtles, these configurations can potentially entrap sea turtles who may subsequently be injured or 

drowned. Entrapment impacts are only applicable to sea turtles. There are no published data 

regarding actual numbers of sea turtle entrapments in towed gear, and much is speculated regarding 

the interaction between sea turtles and seismic gear (Nelms et al., 2016). In the GOM, there were 

no documented cases of sea turtle entrapment of towed gear between the 2002 and 2008 sighting 

reports. However, it is highly possible that entrapments go unnoticed and that sea turtles (live or 

dead) are freed during the recovery process due to the changes in equipment position and tension.

The OBC/OBN (nodal) survey locations and projected levels are not estimated; however, 

nodal surveys are relatively uncommon and are typically used in shallow waters. Given the scope 

and transitory nature of OBC/OBN surveys associated with Alternative A, and the implementation of 

risk-reducing measures described previously, debris entanglement and equipment entrapment 

impacts on sea turtles are expected to be nominal. 

4.3.2.1.8 Routine Activities Impact Conclusions

This analysis considered the significance criteria, the AOI, and the 10-year timeframe. 

Mitigation measures that are associated with Alternative A are outlined in Chapter 2.1 and detailed 
4-146 Description of the Affected Resources and Impact Analysis

in Appendix B. As discussed above, the degree to which these mitigation measures (collectively) 

will affect the levels of impact to sea turtles from each project-related IPF (including routine activities) 

is presented below:

• deep-penetration airgun survey noise – minor; 

• non-airgun HRG electromechanical survey noise – nominal to minor; 

• vessel and equipment noise – nominal; 

• vessel traffic – nominal to moderate; 

• aircraft traffic and noise – nominal; 

• trash and debris – nominal; and

• entanglement/entrapment – nominal. 

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1. 

Implementation of mitigation measures described under Alternative A may reduce potential 

impacts from the IPFs listed above to individuals within the AOI. Impact levels by IPF were 

determined using impact significance criteria discussed in Chapter 4.3.2, and each impact level was 

determined by considering effects to sea turtles within the AOI as a whole.

4.3.2.2 Impacts of an Accidental Fuel Spill

This analysis considered an accidental release of 1.2 to 7.1 bbl of diesel fuel from a vessel 

collision or during fuel transfer. As described in Chapter 3.3.2, a spill of this size and nature is 

considered very unlikely but still reasonably foreseeable. Data from BSEE showed that there were a 

total of 77 petroleum spills from OCS oil and gas activities ranging from 1 to 9 bbl between 2009 and 

2013 (USDOI, BSEE, 2014a). In addition, the NSF and USDOI, GS (2011) noted in their 

programmatic analysis of impacts associated with seismic research that there has never been a 

recorded oil/fuel spill during >100,000 km (62, 137 mi; 54,000 nmi) of NSF-funded seismic surveys. 

Due to the extensive existing network of commercial shipping lanes/fairways in the GOM, traffic 

coordination and regulation by USCG, and regulation of structures on the OCS under the OCSLA, 

vessel to-vessel collisions and vessel-to-structure collisions have been minimal in comparison to the 

extent of existing vessel traffic and movement. According to BSEE’s Incident Statistics and 

Summary Reporting (USDOI, BSEE, 2015b) from 2007 to 2014, 137 collisions (a vessel striking 

another vessel and striking a stationary vessel or object such as a platform) occurred within the 

GOM.

As discussed in Chapter 3.3.2, diesel fuel spilled at the ocean surface would readily 

disperse and weather. Diesel fuel is most often a light, refined petroleum product that is classified 

by the API as a Group 1 class of oil, based on its specific gravity and density, and is not persistent 
Gulf of Mexico G&G Activities Programmatic EIS 4-147

within the marine environment (Biliardo and Mureddu, 2005). When spilled on water, diesel oil 

quickly spreads to a thin film of rainbow and silver sheens, except for marine diesel, which may form 

a thicker film of dull or dark colors. Because diesel oil is lighter than water (specific gravity is 

between 0.83 and 0.88, compared with 1.03 for seawater), it is not possible for this oil to sink and 

accumulate on the seafloor as pooled or free oil unless adsorption occurs with sediment. However, 

it is possible for the diesel oil that is dispersed by wave action to form droplets that are small enough 

be kept in suspension and moved by the currents (USDOC, NOAA, 2015c). As diesel spreads on 

the sea surface, evaporation of the lighter components of the oil occurs. Evaporation rates increase 

in conditions of high winds and sea state as well as high atmospheric and sea surface temperatures 

(Biliardo and Mureddu, 2005; API, 1999; USDOC, NOAA, 2006d). Small diesel spills usually 

evaporate and disperse naturally within a day.

Sea turtles could be affected by an accidental diesel fuel spill during G&G activities. Effects 

of spilled oil on sea turtles are discussed by Geraci and St. Aubin (1987), Lutcavage et al. (1995 and

1997), Milton et al. (2003) and Shigenaka et al. (2010), and are summarized in this chapter. 

Ingested diesel fuel, particularly the lighter fractions, can be acutely toxic to sea turtles. Oil, 

including refined diesel fuel, may affect sea turtles through various pathways such as direct contact, 

inhalation of the fuel and its volatile components, and ingestion (directly or indirectly through the 

consumption of fouled prey species) (Geraci and St. Aubin, 1987). Several aspects of sea turtle 

biology and behavior place them at risk, including lack of avoidance behavior, indiscriminate feeding 

in convergence zones, and inhalation of large volumes of air before dives (Milton et al., 2003). The 

severity, rate, and effects of exposure to oil varies by life stage. For example, hatchling and oceanic 

stage juvenile sea turtles (including juveniles associated with Sargassum) exposed to spilled oil or 

fuel in open ocean environments would be subject to the same oil exposure hazards as adults, 

which are at risk when they surface to breathe or rest on the sea surface, but because hatchlings 

and oceanic stage juveniles spend a greater proportion of their time at the sea surface than adults, 

their risk of exposure to floating oil slicks or oiled Sargassum is increased (Shigenaka et al., 2010). 

Sargassum is further discussed in Chapters 4.1.5.7 and 4.8. Oil and diesel fuel can adhere to sea 

turtle skin and shells. Studies have shown that direct exposure of sea turtle sensitive tissues (e.g., 

eyes, nares, and other mucous membranes) and soft tissues to diesel fuel or volatile hydrocarbons 

may produce irritation and chemical burns, which may lead to secondary infections. Sea turtles 

surfacing within or near a diesel release would be expected to inhale petroleum vapors, causing 

respiratory stress. Ingesting oil or fuel may cause injury to the gastrointestinal tract, which may 

affect the animals’ ability to absorb or digest foods. Toxic chemicals in oil or fuel that are inhaled or 

ingested may damage organs, impair brain function, cause anemia and immune suppression, or 

lead to reproductive failure or death (Shigenaka et al., 2010).

A small, accidental diesel fuel spill from a G&G survey vessel would be expected to disperse 

quickly in the open ocean; small diesel spills usually will evaporate and disperse within a day, even 

in cold water (USDOC, NOAA, 2006d). It is assumed that the spilled fuel would rapidly spread to a 

layer of varying thickness and break up into narrow bands or windrows parallel to the wind direction. 

The rate at which the oil spreads would be determined by the prevailing conditions (e.g., 

temperature, water currents, tidal streams, and wind speeds). The fuel spill is not likely to result in 
4-148 Description of the Affected Resources and Impact Analysis

the death or life-threatening injury of individual sea turtles or hatchlings, or the long-term 

displacement of adult sea turtles from preferred feeding, breeding, or nesting habitats or migratory 

routes. It is unlikely that a small diesel fuel spill in the ocean would reach sea turtle nests, which 

usually are positioned above the high tide line. Therefore, potential impacts to sea turtles within the 

AOI are expected to range from nominal (if the fuel does not contact individual sea turtles) to minor

(if individual sea turtles encounter the dispersed windrows of the surface slick).

4.3.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for sea turtles are compared with the IPFs from each 

of the cumulative scenario components in order to focus this cumulative analysis on those activities 

that coincide spatially and temporally with the proposed action (Table 3.4-1). Figure 3.4-1 shows 

the spatial distribution of cumulative activities, indicating that most of the cumulative activities are 

concentrated in shallow shelf waters. The G&G activity IPFs that are included in the cumulative 

assessment are the same as those assessed under routine activities and accidental events. All 

conclusions that are made in this analysis are based on the expectation of adherence to all 

regulations and mitigations. The following analysis evaluates the incremental increase by IPF and 

provides a conclusion of the cumulative incremental increase within the AOI.

4.3.2.3.1 Noise

Primary sources of noise associated with the cumulative scenario that may impact sea turtles 

include active acoustic sound sources, vessel and equipment, and aircraft. Each source is 

discussed in separate sections below.

Active Acoustic Sound Sources

Cumulative impacts are assessed in this analysis for the cumulative activities that produce 

active acoustic sound sources, including State waters oil and gas, commercial fishing, cable 

installation, military, and scientific research activities (Table 3.4-1). Certain oil and gas-, renewable 

energy-, and marine minerals-related activities such as drilling noise, trenching noise, pile-driving, 

and decommissioning are discussed below under “Vessel and Equipment Noise” because they are 

not active acoustic sounds but rather are related to equipment.

Overall, Chapter 4.3.2.1 determined there would be increases in ambient noise levels within 

specific portions of the AOI during G&G operations but nominal to minor impacts to sea turtles from 

the proposed action. Proposed OCS G&G activities utilizing active acoustic sound sources are 

predicted for both continental shelf and deepwater regions; however, activities will be highest within 

deepwater environments of the CPA and WPA; projected levels of activities in the EPA are very 

small (Table 3.2-1). The majority of the cumulative activities occur in shallow shelf waters (Figure 
Gulf of Mexico G&G Activities Programmatic EIS 4-149

3.4-1). Other survey activities, such as marine mineral- and renewable energy-related surveys, are 

projected to occur on the continental shelf in shallower waters.

Oil and gas activities in State waters would produce active acoustic sounds in shelf waters, 

whereas scientific research, military activities, and commercial fishing activities (using sonar) could 

contribute active acoustic sound throughout the AOI. It is not expected that activities in the 

cumulative scenario would overlap spatially with the proposed G&G activities due to spatial 

avoidance of activities; however, temporal overlap may occur.

The level of proposed activities represent an incrementally significant addition to similar 

activities within the GOM, especially within deepwater environments of the CPA and WPA. Airgun 

noise from activities may, in some cases, propagate into State waters and would combine with 

activities occurring in State waters. Due to distance, it is assumed that the intensity of active 

acoustic source sounds associated with the proposed activity entering State waters will be 

significantly attenuated from source levels, and effects to sea turtles will range from no observable 

effect to some behavioral disturbances. The contribution of proposed noise associated with deeppenetration and HRG survey activities to current conditions under the cumulative scenario will result 

in an increase in active acoustic noise and would produce a nominal to minor incremental increase 

in active acoustic sound impacts to sea turtles under the cumulative scenario.

Vessel and Equipment Noise

Vessel noise is a major contributor to ambient noise levels within the GOM, particularly in the 

low-frequency bands (Snyder, 2007). Vessel noise is contributed by all of the cumulative scenario 

activities (Table 3.4 1). As discussed in Chapter 4.3.2.1, noise from vessel traffic is generated from 

vessel propulsion systems and internal machinery (the latter also termed equipment noise), and is 

the dominant source of underwater noise at frequencies below 300 Hz in many areas. Commercial 

ships and smaller vessels have been increasing in number and size, and generate increasing 

amounts of underwater noise as a by-product of their operation. The contribution of shipping to 

ambient noise is especially high near major ports and heavily travelled shipping lanes. Table 3.2-7

provides the number of estimated vessels required by survey type and by program area for the 

proposed action, and include 19,689 trips for support vessels and 1,008 for survey vessels. For 

cumulative vessel traffic, Table 3.4-2 provides a summary of projected support vessel operations 

anticipated for the oil and gas program, and estimates that support vessel trips will range from 

828,000 to 1,096,000 for the 10-year span of the cumulative scenario. Tables 3.4-7 and 3.4-8

provide vessel trip data for all vessels in the GOM. Exact numbers of cumulative vessel traffic 

associated with renewable energy- and marine mineral-related support activities are not known, but

they are expected to be relatively small and spatially and temporally limited. Oil and gas program 

support vessel traffic projected in the cumulative scenario is expected to be most concentrated 

within the WPA and CPA, as would the proposed action vessel traffic. Vessel traffic within the AOI is 

expected to be somewhat concentrated in lanes and channels near major service centers such as 

Port Fourchon, Louisiana. The amount of vessel and equipment noise generated by the proposed 

action is very small compared with what exists under the cumulative scenario.
4-150 Description of the Affected Resources and Impact Analysis

Sources of equipment noise associated with the cumulative scenario includes drilling and 

production activities, pipeline trenching and placement, decommissioning of offshore structures, piledriving associated with renewable energy installations, dredging noise from marine mineral activities, 

military activities, channel dredging, and coastal restoration activities. Sources of equipment noise 

from the proposed action include drilling noise from a limited number of test wells and noise from DP 

and jack-up vessels (Chapter 3.3.1.2).

The most likely effects of vessel and equipment noise on sea turtles would be behavioral 

changes and auditory masking. Vessel and equipment noise is transitory and generally does not 

propagate to great distances from the vessel, and the source levels are too low to cause death or 

injuries such as auditory threshold shifts. Based on existing studies on the role of hearing in sea 

turtle ecology (Chapter 4.3.2.1; Appendix I), it is unclear whether masking would have any 

ecological effect on sea turtles. Behavioral responses to vessels have been observed but are 

difficult to attribute exclusively to noise rather than to visual or other cues. Nevertheless, it is 

conservative to assume that noise associated with G&G survey and support vessels may elicit 

behavioral changes in individual sea turtles near the vessels. It is assumed that these behavioral 

changes will be limited to evasive maneuvers such as diving, changes in swimming direction, or 

changes in swimming speed to distance themselves from the vessels.

Proposed activities associated with Alternative A would increase levels of vessel and 

equipment noise within the AOI, resulting in increases in ambient noise levels within discrete 

geographical areas during G&G operations (primarily the WPA and CPA). The proposed action 

would produce a nominal incremental increase in equipment noise impacts to sea turtles under the 

cumulative scenario for Alternative A.

Aircraft Noise

Aircraft traffic and noise would result from remote-sensing surveys (aeromagnetic surveys) 

and helicopter support during the drilling of COST wells, shallow test wells, and support and service 

during deep-penetration seismic airgun surveys. BOEM anticipates that one aeromagnetic survey 

may be conducted in the AOI during the time period covered by this Programmatic EIS 

(Chapter 3.2.1.2). Helicopter flights will be used to conduct crew changes for larger seismic 

vessels, the number of anticipated transits is provided in Table 3.2-7 and discussed in Chapter

3.3.1.4. Projections for helicopter operations supporting G&G activities within the AOI over the 

10-year project period are estimated to be a minimum of 7,497 trips (Table 3.2-7). The cumulative 

scenario estimates that 7,178,000 to 13,901,000 helicopter trips would occur over the 10-year period 

(Table 3.4-2) to support oil and gas activities.

Helicopters and fixed-wing aircraft generate noise from their engines, airframe, and 

propellers. The dominant tones for both types of aircraft generally are below 500 Hz (Richardson 

et al., 1995) and within the auditory range of sea turtles (Appendix I). Aeromagnetic surveys are 

conducted at speeds of approximately 135 kn (155 mph) and at altitudes between 61 and 152 m 

(200 and 500 ft). Typical operational altitudes for helicopters in the GOM are higher than 229 m 
Gulf of Mexico G&G Activities Programmatic EIS 4-151

(750 ft), except when in the vicinity of platforms. Levels of noise received underwater from passing 

aircraft depend on the aircraft’s altitude, the aspect (direction and angle) of the aircraft relative to the 

receiver, receiver depth, water depth, and seafloor type (Richardson et al., 1995). Because of the 

relatively high expected airspeeds and these physical variables, aircraft-related noise (including 

airborne and underwater noise) is expected to be very brief in duration at any given point.

The physical presence of low-flying aircraft can disturb sea turtles, particularly individuals 

resting on the sea surface. It is expected that impacts from aircraft traffic under Alternative A will be 

limited to behavioral disruptions. As discussed in Chapter 4.3.2.2, observations made from lowaltitude aerial surveys report that behavioral responses of sea turtles are highly variable and range 

from no observable reaction to diving or rapid changes in swimming speed or direction. Although 

projected levels of aircraft traffic from G&G operations under Alternative A would increase existing 

traffic levels within the AOI, it is expected that this increase would produce a nominal incremental 

increase in impacts to sea turtles under the cumulative scenario.

4.3.2.3.2 Vessel and Aircraft Traffic

Vessel traffic is an IPF associated with all components of the cumulative scenario and is 

included in the proposed action. Aircraft traffic (physical presence) may disturb sea turtles on or 

near the sea surface; noise impacts are discussed above. The G&G survey and support vessel 

traffic associated with the proposed action under Alternative A is discussed in Chapter 3.3.1.3. 

As discussed above, vessel and aircraft traffic associated with OCS Program activities will 

originate from selected ports in the CPA and WPA, and will cross State waters to reach fields within 

the OCS. This discussion of vessel traffic draws from the discussion on vessel noise above, with 

respect to projected and historical OCS Program vessel traffic levels and other cumulative vessel 

traffic levels. As discussed in Chapter 4.3.2.1, underway vessels could collide with sea turtles, 

particularly individuals that rest on the sea surface between dives. In addition, the physical presence 

of these vessels and aircraft may disturb individuals on or near the sea surface.

Table 3.2-7 provides the number of estimated vessels required by survey type and by 

program area for the proposed action, and includes 19,689 trips for support vessels and 1,008 trips 

for survey vessels. For cumulative vessel traffic, Table 3.4-2 provides a summary of projected 

support vessel operations anticipated for the oil and gas program and estimates that support vessel 

trips will range from 828,000 to 1,096,000 trips for the 10-year span of the cumulative scenario. 

Tables 3.4-7 and 3.4 8 provide vessel trip data for all vessels in the GOM. Exact numbers of 

cumulative vessel traffic associated with renewable energy- and marine mineral-related support 

activities are not known, but they are expected to be relatively small and spatially and temporally 

limited. Other sources of vessels associated with the cumulative scenario include those associated 

with oil and gas activities in State waters, drilling and production activities (within both State waters 

and OCS waters), commercial shipping, commercial and recreational fishing, military activities, 

scientific research, offshore construction activities, maintenance dredging of Federal channels and 
4-152 Description of the Affected Resources and Impact Analysis

dredged material disposal, coastal restoration programs, and Mississippi River hydromodification 

and subsidence issues (Table 3.4-1).

As discussed in Chapter 4.3.2.2, sea turtles may be vulnerable to physical disturbance from 

or collision (ship strike) with moving vessels. Propeller and hull collision injuries to sea turtles, 

particularly to the most abundant species in the GOM, i.e., the loggerhead turtle, arising from 

interactions with boats and ships are fairly common (Alderson, 2009). The physical presence of lowflying aircraft can disturb sea turtles, particularly individuals resting on the sea surface, although it is 

difficult to separate effects from physical disturbance and noise. Based on the projected level of 

G&G activity under the Alternative A scenario, impacts to sea turtles from vessel and aircraft traffic 

were determined to be limited to behavioral disturbances and were classified as nominal. Additional 

vessel and aircraft traffic from G&G operations under the proposed action would be substantive but 

would not represent a significant increase to existing vessel traffic from cumulative operations within 

the AOI (Tables 3.4-7 and 3.4-8). Therefore, G&G activities associated with Alternative A would 

produce a nominal incremental increase in impacts from vessel and aircraft traffic to sea turtles 

under the cumulative scenario.

4.3.2.3.3 Trash and Debris

The Federal oil and gas program in the GOM has approximately 2,634 existing structures 

conducting production activities, including drilling operations. The operation of these structures, 

including staff, and the activities conducted have the potential to generate trash and debris 

comprising paper, plastic, wood, glass, and metal (Chapter 3.3.1.7). Oil and gas operations in the 

Gulf of Mexico OCS are required to adhere to provisions of MARPOL Annex V, as well as to USCG 

and USEPA regulations and NTL 2015-BSEE-G03. By adhering to these requirements, it is 

anticipated that trash and debris impacts, including entanglement and ingestion, from the cumulative 

scenario activities would be reduced.

Potential impacts from discarded trash and debris associated with Alternative A on sea 

turtles is discussed in Chapter 4.3.2.2. Impacts from discarded trash and debris on sea turtles from 

G&G survey vessels, sampling activities, the drilling of shallow or COST wells, and other activities 

would result in a nominal incremental increase in the impact to sea turtles under the cumulative 

scenario.

4.3.2.3.4 Entanglement and Entrapment

Sources of entanglement in the proposed action that may impact sea turtles within the AOI 

include placement of anchors, nodes, cables, sensors, or other equipment on or in the seafloor. 

Acoustic buoy releases, tethered acoustic pingers, and nodal tethering lines pose an entanglement 

risk to sea turtles, particularly deep-diving species such as leatherback sea turtles. Activities 

associated with the cumulative scenario that may deploy equipment that may pose entanglement 

risks to sea turtles within the AOI include State waters oil and gas activities, commercial and 

recreational fishing, and scientific research. Sources of entanglement include anchors, cables, 
Gulf of Mexico G&G Activities Programmatic EIS 4-153

sensors, fishing gear, or other equipment moored or tethered to the seafloor either permanently or 

temporarily, as well as any type of line extending from the surface or subsurface to the seafloor.

Activities associated with coastal development, restoration, or maintenance such as dredging 

of channels, shoreline and beach restoration, Mississippi River hydromodification, and remediation 

of subsidence would occur in State coastal zones and waters, which is outside of BOEM’s 

jurisdiction. These types of activities would not be associated with entanglement for sea turtles but 

would impact the quality, at least temporarily, of nearshore habitat that is critical to sea turtles for 

reproduction, foraging, and life stage development. These coastal habitats are so important to sea 

turtles that areas of the nearshore shallow waters of Florida, Alabama, and Mississippi recently were 

designated as reproductive critical habitat for the loggerhead sea turtle (79 FR 39856).

Risks of entanglement to sea turtles may be reduced for the proposed action by shortening 

the length of line tethering buoys or acoustic pingers to the shortest length practical and by replacing 

tether rope lines that are <0.25 inches in diameter with a thicker, more rigid tether line or modifying 

the line by tying knots along its length to increase the diameter and rigidity (USDOI, BOEM, 2013e). 

Having a PSO monitoring for sea turtles during tethered node and retrieval operations will also lead 

to fewer sea turtle entanglements in tethered lines. Given the scope of OBC and OBN surveys in 

the AOI in addition to the implementation of preventative measures during activities involving 

deploying tethered or mooring lines, a nominal incremental increase in impacts under the 

cumulative scenario is expected.

4.3.2.3.5 Cumulative Impact Conclusions

Overall, proposed activities associated with the proposed action would increase levels of 

noise and vessel and aircraft traffic within the AOI, resulting in sporadic increases in ambient noise 

levels during proposed G&G operations. Sources of noise associated with the cumulative scenario 

that may affect sea turtles of the AOI include active acoustic sound, vessel and equipment, and 

aircraft. Other IPFs that may affect sea turtles include vessel and aircraft traffic, trash and debris, 

entanglement/entrapment, and accidental fuel spills. Many of these IPFs may occur simultaneously 

during some projected operations under the OCS Program. For example, during deep-penetration 

seismic, shallow-penetration seismic, and non-airgun HRG survey operations, IPFs such active 

acoustic sound, vessel and equipment noise, vessel traffic, and aircraft noise and traffic (during 

some survey activities) will occur together. Entanglement of sea turtles in ocean bottom cable or 

entrapment in towed equipment, and the release of trash and debris or fuel into offshore waters are 

not routine and, therefore, represent accidental occurrences during the 10-year project period.

The spatial distribution of activities projected under the proposed action during the project 

period are most concentrated within deepwater regions of the CPA and WPA, and less concentrated 

within continental shelf waters (Table 3.2-1). Very little activity is projected to occur within the EPA. 

Temporally, activity levels associated with the proposed action vary by activity type and year (Tables 

3.2-1 through 3.2-5). From this analysis, impacts to sea turtles from proposed routine activities 

include moderate impacts (from active acoustic sound associated with deep-penetration seismic 
4-154 Description of the Affected Resources and Impact Analysis

airgun surveys), minor impacts (i.e., active acoustic sound associated with shallow-penetration 

airgun and non-airgun HRG surveys, and vessel and equipment noise), and nominal impacts (i.e., 

vessel, equipment, and aircraft noise, vessel and aircraft traffic, trash and debris, and 

entanglement/entrapment).

When compared with historic levels of activities within the GOM, proposed activities do not 

represent a significant incremental increase to activities under the cumulative scenario. Surveys 

utilizing active acoustic sound sources have occurred within the GOM for decades, including within 

State waters and the continental shelf and deepwater regions of the OCS. Commercial, military, and 

recreational vessel traffic has also occurred in the GOM, including the AOI for many years. In some 

cases, such as large commercial vessels, traffic is and has been more concentrated along Gulfwide 

shipping lanes that funnel into major coastal ports. Commercial and recreational fishing vessels 

have utilized broad areas of the northern GOM, but primarily on the continental shelf and shelf edge. 

It is assumed that military vessels have traveled through all areas of the GOM, though it is assumed 

that most, if not all, exercises have occurred within the U.S. Navy GOMEX Range Complex 

OPAREAs, including Panama City, Pensacola, New Orleans, and Corpus Christi (AFTT, 2015).

While the impact-producing factors associated with the proposed action could potentially 

impact sea turtles if unmitigated, the incremental contribution to cumulative impacts on sea turtles, 

even when taking into consideration the potential impacts of the Deepwater Horizon explosion, oil 

spill, and response, non-OCS oil- and gas-related factors and the minimization of OCS oil- and gasrelated impacts through lease stipulations and regulations, would be expected to be nominal to 

minor as a result of the proposed action. Within the GOM, there is a long-standing and welldeveloped OCS Program (more than 50 years), and population-level impacts to sea turtles are not 

anticipated.

When compared with historic, present, and future activities, including similar non-OCS 

Program activities (Figure 3.4-1), the cumulative effects of all IPFs to sea turtles within the AOI over 

the 10-year period would result in nominal to minor incremental increases in impacts.

4.3.2.3.6 Accidental Fuel Spills

For the proposed action and alternatives, an accidental spill scenario was evaluated 

(Chapter 3.3.2) and the likelihood of a small fuel spill occurring during G&G activities is considered 

remote, but reasonably foreseeable. In the event of a spill occurring within coastal waters, such as 

inland waterways, it is anticipated that the fuel would travel along wind-driven and tidal currents, and 

spread into coastal areas by storm surge. For Alternative A, it was assumed fuel would be spilled 

offshore and would rapidly spread to a thin layer before breaking into narrow bands or windrows. 

The spread of the spilled fuel on the sea surface would augment weathering processes, and lighter 

volatile components of the fuel would evaporate almost completely in a few days.

Potential impacts to sea turtles from a 1.2- to 7.1-bbl diesel fuel spill would depend greatly on 

the location of the spill, meteorological conditions at the time, and the speed with which cleanup 
Gulf of Mexico G&G Activities Programmatic EIS 4-155

plans and equipment could be employed. For Alternative A (Chapter 4.3.2.2), it was assumed that 

the spilled fuel would rapidly spread to a thin layer; subsequently, this layer would break into narrow 

bands or windrows. The spread of the spilled fuel on the sea surface would augment weathering 

processes, and lighter volatile components of the fuel would evaporate almost completely in a few 

days. Because of the thickness of the slick and rapid weathering, it is not likely that many animals 

would come into contact with the surface fuel or oiled Sargassum. Potential impacts were assumed 

to be limited to minor mucous membrane irritation and possibly behavioral alteration (in this case, 

temporary displacement from the affected area). No mortalities of sea turtles are expected from the 

spill. Potential impacts to sea turtles associated with a small diesel fuel spill under Alternative A are 

expected to be variable, ranging from nominal to minor. 

The proposed action would slightly increase vessel traffic activity in the AOI and the risk of 

collision and a resultant spill. The G&G vessel activities under the proposed action would produce a 

nominal incremental increase in impacts to sea turtles from a vessel collision- or fuel transfer-based 

spill under the coastal developments component of the cumulative scenario due to the relatively 

small volume of the spill and the remote possibility of the spill’s occurrence.

4.3.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.3.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative B on sea turtles.

4.3.3.1 Impacts of Routine Activities

4.3.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to April 30)

Alternative B includes a seasonal restriction in Federal coastal waters of the GOM shoreward 

of the 20-m (66-ft) isobath between January 1 and April 30. No airgun surveys would be authorized 

within the area during this time. This seasonal restriction was designed to protect the northern Gulf 

of Mexico BSE stocks of the common bottlenose dolphin as discussed in Chapter 4.2.3.1. The time 

period for the area closure (January 1 to April 30) corresponds with the peak calving season for 

these stocks.

As discussed in Chapter 4.3.2, applicable routine IPFs for sea turtles include active acoustic 

sound sources, vessel traffic and associated vessel and equipment noise, aircraft traffic and noise, 

trash and debris, and entanglement/entrapment. The seasonal restriction for Federal coastal waters 

under Alternative B would remove the potential for impacts from active acoustic sound sources from 

airgun surveys during a 2-month time period. Active acoustic sources from non-airgun HRG and 

geological surveys; survey-related vessel, aircraft, and equipment noise; and survey-related vessel 

and aircraft traffic on sea turtles within inner shelf and coastal areas during the months of March and 

April would still occur. This measure will not influence effects from active acoustic sources from nonairgun HRG and geological surveys drilling noise, disturbance from fixed-wing aircraft during 
4-156 Description of the Affected Resources and Impact Analysis

aeromagnetic surveys, and trash and debris. These IPFs are not discussed further in this chapter

but are summarized above under Alternative A (refer to Chapter 4.3.2.2).

Based on the scope of the proposed action, seismic airgun surveys could affect individuals of 

all sea turtle species within the AOI. It is anticipated that surveys conducted within Federal coastal 

waters may affect all species and greater numbers of individuals than surveys that are conducted in 

deepwater (outer shelf and slope) environments. Deepwater surveys are likely to impact primarily 

adult leatherback sea turtles and loggerhead sea turtles as well as hatchlings and juveniles that are 

associated with mats of floating Sargassum, weedlines, and other flotsam. Surveys conducted 

during summer sea turtle nesting periods within Federal coastal waters may affect greater numbers 

of adult sea turtles, particularly loggerhead and Kemp’s ridley sea turtles, than those conducted 

during non-nesting periods. Designated critical habitat for young loggerhead sea turtles 

(“Sargassum Habitat”) is shown in Figure 4.3-3 and includes offshore waters of the EPA and almost 

all of the WPA and CPA. 

Implementation of this seasonal restriction would remove stress and potential auditory 

injuries from airgun surveys to sea turtles within Federal coastal waters from January 1 to April 30. 

The time period for this restriction coincides with the beginning of sea turtle nesting activities on 

nesting habitats within the GOM. This measure may be effective for the protection of early nesting 

activities (e.g., selection and use of nesting areas) and breeding activities in inner shelf waters. 

However, under Alternative B, seismic activities will be permitted to resume within Federal coastal 

waters after April 30, which is during peak nesting season. Overall, this measure will not affect sea 

turtles within outer shelf and slope waters, and may only protect early nesting and breeding activities 

within Federal coastal waters. Therefore, it is not likely that the measure will reduce the overall 

impact level (minor) for sea turtles in the AOI from seismic airgun activities.

The seasonal restriction would reduce project-related seismic survey vessel traffic and 

associated vessel and equipment noise in coastal areas during this time period. As discussed in 

Chapter 4.3.2.1, impacts of vessel traffic would remain nominal to moderate and impacts from 

vessel and equipment noise on sea turtles are expected to remain nominal. This additional 

mitigation measure may temporarily decrease the potential vessel disturbance to and vessel strikes 

with individual sea turtles in coastal areas during the closure. However, cable laying for OBCs, for 

example, is not restricted (based on the requirements in the Settlement); thus, impacts from 

entanglement would remain nominal as described in Chapter 4.3.2.1. In addition, non-airgun HRG 

and geological surveys are not restricted; therefore, the potential for striking a sea turtle is not 

completely removed. Potential impacts to sea turtles from vessel traffic and noise are expected to 

remain unchanged with this mitigation measure because the additional closure is probably not of 

sufficient duration to significantly reduce impact levels. The additional seasonal restriction for 

Federal coastal waters under Alternative B would not remove the potential aeromagnetic survey or 

the drilling of two shallow test wells and a COST well within the AOI. In addition, helicopters used 

for seismic airgun survey support would not operate in these areas during the closure. It is likely that 

individual sea turtles within Federal coastal waters of the AOI are accustomed to the sounds and 

physical presence of oil and gas industry helicopter traffic within the AOI. Therefore, it is expected 
Gulf of Mexico G&G Activities Programmatic EIS 4-157

that the impacts from aircraft traffic and noise would remain unchanged (nominal under 

Alternative A) for the additional coastal seasonal restriction under Alternative B.

4.3.3.1.2 Expanded PSO Program

Alternative A includes operational mitigation measures, as described in Chapter 2.1.2 and 

Appendix B, Section 1 that would be implemented during seismic airgun surveys. These measures 

include the establishment of a 500-m (1,640-ft) exclusion zone, visual monitoring by qualified PSOs, 

and ramp-up requirements (implementation of PSO Program and the Seismic Airgun Survey 

Protocol). Under Alternative B, the requirements of the expanded PSO Program require the same 

mitigation measures for manatees as for whales and are required for all deep-penetration seismic 

airgun surveys in the GOM regardless of water depth. Mitigation measures for sea turtles remain 

the same as under Alternative A.

The purpose of this operational measure (i.e., exclusion zone) is to prevent serious injury to 

sea turtles (and marine mammals) by ensuring that they are not present within an established 

exclusion zone around the airgun array. Under Alternative B, these measures are required for all 

deep-penetration seismic airgun surveys throughout the AOI. Because this measure is expanded to 

include deep-penetration seismic survey operations in all water depths within the AOI, it would 

benefit subadult and adult stages of all sea turtle species within the AOI during daylight seismic 

survey operations (these measures are conducted only during daylight hours). Because of their size 

and cryptic nature within weedlines and mats of flotsam, it is not likely that hatchling sea turtles 

would be sighted by PSOs during monitoring surveys.

As discussed in Chapter 4.3.2.2, although these mitigation measures require clearance of 

the exclusion zone for sea turtles prior to start-up, they do not require shutdown for sea turtles; 

consequently, some individual sea turtles may be exposed to sound levels that lead to TTS or PTS 

auditory injuries. With ramp-up requirements, it is assumed that there will be no deaths or lifethreatening injuries from airgun activities, even during nighttime (this is based on the assumption 

that sea turtles would move away from the sound source during ramp-up). It has long been 

assumed that early life history stages of sea turtles associated with Sargassum habitats were largely 

or entirely passive drifters, with little potential for directed movements towards or away from stimuli. 

Recent work by Putman and Mansfield (2015) has demonstrated active dispersal of early life stages 

in the GOM, which demonstrates at least a potential for active swimming to avoid adverse stimuli. 

Most of the effects from active acoustic sound sources would consist of behavioral alterations (e.g., 

avoidance, evasive actions, and temporary displacement from the area around the sound source), 

along with some non-life-threatening auditory injuries (e.g., threshold shift). Overall, effects of this 

mitigation measure under Alternative B would not reduce potential active acoustic impacts discussed 

under Alternative A (minor for airgun survey activities and nominal to minor for non-airgun HRG 

survey activities using boomers and sparkers). This mitigation does not apply to the other projectrelated IPFs and would not alter the impacts to sea turtles from vessel and equipment noise, aircraft 

traffic and noise, trash and debris, or entanglement/entrapment; all impacts would remain nominal. 
4-158 Description of the Affected Resources and Impact Analysis

As discussed in Chapter 4.3.2.1, impacts of vessel traffic would remain nominal to moderate (if a 

collision occurred).

4.3.3.1.3 Minimum Separation Distances

Alternative B would establish a 40-km (25-mi) separation distance between simultaneously 

operating, deep-penetration seismic airgun surveys within the areas of concern (areas within 

Mississippi and De Soto Canyons, Federal coastal waters shoreward of the 20-m [66-ft] isobath, and 

areas west of the Florida Keys and Dry Tortugas) (Chapter 2.2.2). These areas of concern are 

shown in Figure 2.2-1. When outside the designated areas of concern, the separation distance will 

be 30 km (19 mi). This minimum separation distance requirement does not apply to operations with 

multiple vessels in a single survey, such as WAZ surveys, or in conditions of inclement weather or 

other unsafe conditions. This measure was designed to mitigate possible effects of anthropogenic 

underwater sounds from multiple seismic operations on resources such as marine mammals and 

sea turtles, including the effects of interacting and repeated sounds. This measure may affect 

potential impacts from active acoustic sources as well as survey-related vessel and aircraft noise. 

This mitigation measure will not affect potential impacts from other IPFs, such as fixed-wing aircraft 

noise (during aeromagnetic surveys), drilling noise, and trash and debris. These IPFs are discussed 

further in Chapter 4.3.2.1. 

Limits on concurrent seismic airgun surveys under Alternative B could change the timing of 

surveys in certain areas. The specific locations cannot be predicted in advance and would depend 

on the schedule, planned coverage of individual surveys, and ports to be used for support activities. 

New information suggests that, in some circumstances, airgun noise can be detected at great 

distances from the sound source, such as across ocean basins (Nieukirk et al., 2012); however, it is 

unknown if detection of sound at these distances has any effect on marine species, making this 

mitigation measure difficult to evaluate. Therefore, specific details regarding potential impacts in 

certain areas and time periods is not possible for this analysis. BOEM concludes that there is 

incomplete or unavailable information (40 CFR § 1502.22) for all sea turtles with respect to effects 

from seismic airgun surveys and concurrent surveys. However, what is known about the biology and 

hearing physiology of representative species, in combination with observations of behavioral 

response to stimuli, allows inferences and conclusions about reasonably foreseeable adverse 

impacts on sea turtles to be understood with an adequate degree of certainty. BOEM has therefore 

determined that the data or information on sea turtle biology, hearing physiology, seasonal 

abundances, and population stock in the AOI identified as incomplete or unavailable is not essential 

to a reasoned choice among the alternatives, including the No Action alternative.

Moreover, a more complete knowledge base for all types of sea turtles that use the AOI and 

that bear on the factors listed above is not available, and the acquisition of such information cannot 

be acquired without exorbitant cost. Such information certainly cannot be acquired in a timeframe to 

make it available for this evaluation. While there will never be complete scientific information on sea 

turtles that live in OCS waters, a body of biological and physiological data and information about the 

underwater hearing of representative sea turtles is available to us. These data are sufficient to draw 
Gulf of Mexico G&G Activities Programmatic EIS 4-159

inferences and conclusions about the types of sea turtles that are less well understood. Thus, while 

we report where limited data and insufficient knowledge challenge our ability to understand how and 

when specific types of sea turtle species use the AOI and that bear on the factors listed above, 

incomplete or unavailable information does not affect our ability to understand and assign impacts or 

design mitigation strategies. We are able to draw basic conclusions despite incomplete or 

unavailable information, discuss results using available scientifically credible information, and apply 

that information using accepted scientific methodologies.

A change in survey location and timing because of limits on concurrent seismic airgun 

surveys would not alter the impacts from active acoustic sources on sea turtles within the AOI. 

Impacts would be similar to those discussed in Chapter 4.3.2.1 under Alternative A (minor for 

airgun survey activities and nominal to minor for HRG survey activities using boomers and 

sparkers). A change in survey location and timing because of limits on concurrent seismic airgun 

surveys would not alter the impacts to sea turtles from vessel traffic, vessel and equipment noise, 

aircraft traffic and noise, trash and debris, or entanglement; all impacts would remain nominal. As 

discussed in Chapter 4.3.2.1, impacts of vessel traffic would remain nominal to moderate (if a 

collision occurred).

4.3.3.1.4 Seismic Restrictions in the Areas of Concern within the EPA

Additional restrictions under Alternative B include prohibiting deep-penetration seismic airgun 

surveys in the Areas of Concern (Chapter 2.2.2) falling within the EPA. This restriction does not 

apply to surveys related to currently leased blocks, any portion of the area encompassed by EPA 

Lease Sale 226, or neighboring OCS lease blocks adjacent to permitted survey areas but within an 

otherwise off limit area. Restricted areas include the portions of Area of Concern 2 within the EPA, 

waters offshore of western Florida and the Florida Panhandle shoreward of the 20-m (66-ft) isobath 

(portions of Area of Concern 3), and an OCS lease block south of the Dry Tortugas and Florida Keys 

(Area of Concern 4, Figure 2.2-1).

Closure of Area of Concern 2 would provide protection from airgun-related impacts to 

individual sea turtles, such as adult loggerhead sea turtles, and hatchling sea turtles (primarily 

loggerhead and perhaps Kemp’s ridley) within these offshore waters. Area of Concern 4 would 

provide protection for individual sea turtles in offshore waters of the Florida Straits, whereas portions 

of Area of Concern 3 (shoreward of the 20-m [66-ft] isobath) would provide protection for most sea 

turtle species in the AOI. However, seismic survey activities associated with Alternative B likely 

would occur outside of the boundaries of the protected areas and within the majority of the AOI. 

Although this mitigation measure likely would protect most sea turtles within the Areas of Concern, 

as well as numerous individuals that may occur along the inner continental shelf of western Florida, 

it would not reduce the overall impacts to sea turtles within the AOI. Therefore, it is expected that 

the impacts to sea turtles from seismic airgun activities would remain unchanged from Alternative A 

(minor for airgun survey activities and nominal to minor for HRG survey activities using boomers 

and sparkers) for the additional area of closure under Alternative B.
4-160 Description of the Affected Resources and Impact Analysis

This mitigation measure would remove threats from vessel traffic (collisions), vessel and 

equipment noise, and seismic survey-related aircraft noise within areas of the EPA. Though this 

closure of seismic activity may result in a localized reduction of vessel traffic, overall impacts to sea 

turtles would be expected to remain nominal to moderate (if a collision occurred) because the 

reduction of vessel traffic would be localized and relatively small compared with the AOI. As 

discussed in Chapter 4.3.2.1, impacts of vessel noise would remain nominal. Effects of this 

mitigation measure under Alternative B would not alter the impacts to sea turtles from trash and 

debris or entanglement/entrapment and would remain nominal. 

4.3.3.1.5 Routine Activities Impact Conclusions

This analysis considered the significance criteria, the AOI, and the 10-year timeframe. 

Mitigation measures that are associated with Alternative B are outlined in Chapter 2.2 and detailed 

in Appendix B. As discussed above, the degree to which these mitigation measures (collectively) 

will affect or change the levels of impact to sea turtles from each project-related IPF (including 

routine activities) is presented below:

• deep-penetration airgun survey noise – minor; 

• non-airgun HRG electromechanical survey noise – nominal to minor; 

• vessel and equipment noise – nominal; 

• vessel traffic – nominal to moderate; 

• aircraft traffic and noise – nominal; 

• trash and debris –nominal; and

• entanglement and entrapment – nominal. 

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1. 

Implementation of mitigation measures described under Alternative B may reduce potential 

impacts from the IPFs listed above to individuals within the AOI. Impact levels by IPF were 

determined using impact significance criteria discussed in Chapter 4.3.2.1, and each impact level 

was determined by considering effects to sea turtles within the AOI as a whole.

4.3.3.2 Impacts of an Accidental Fuel Spill

Under Alternative B, impacts of an accidental fuel spill on sea turtles would be very similar to 

those analyzed in Chapter 4.3.2.2 for Alternative A. The analysis concluded that a small spill at the 

sea surface would result in nominal to minor impacts, depending on the number of individuals 

adversely affected by the spilled fuel and the exposure of federally listed species to the spilled fuel.
Gulf of Mexico G&G Activities Programmatic EIS 4-161

Alternative B would change the timing of certain surveys because of additional coastal 

seasonal restrictions and limits on concurrent seismic airgun surveys. Additionally, certain surveys 

will not be conducted within portions of the EPA. The closure of coastal waters along the west coast 

of Florida could effectively protect individuals from all species of sea turtles within the AOI, including 

nesting sea turtles. This closure area and the Dry Tortugas/Florida Keys closure area would protect 

significant nesting habitats of loggerhead, green, Kemp’s ridley, and turtles within the AOI. 

However, spills from survey-related vessels could occur within coastal seasonal restriction areas 

outside of the closure period, and spills from non-airgun HRG survey vessels (except those using 

boomer or sparker subbottom profilers) could occur during the closure period or in the EPA. A 

change in survey timing or type because of limits on concurrent seismic airgun surveys or on survey 

type would not substantially change the risk of a small fuel spill. Therefore, the risk of a small fuel 

spill and its potential impacts on sea turtles within the AOI would be the same as under 

Alternative A, i.e., nominal (if the fuel does not contact individual sea turtles) to minor (if individual 

sea turtles encounter the dispersed windrows of the surface slick) impacts, depending on the 

numbers of individuals adversely affected by the spilled.

4.3.3.3 Cumulative Impacts

Impact analyses presented in Chapters 4.3.3.1 and 4.3.3.2 determined that activities 

projected to occur under Alternative B would result in nominal to moderate impacts to sea turtles, 

depending on the IPF.

The cumulative assessment for Alternative A in Chapter 4.3.2.3 compared with historic, 

present, and future activities, including similar non-OCS Program activities, evaluated cumulative 

activities with similar IPFs to the proposed activities, spatial and temporal occurrence, and 

concluded that the cumulative effects of all IPFs to sea turtles within the AOI over the 10-year period 

would result in nominal to minor incremental increases in impacts.

Mitigation measures under Alternative B would not significantly change the extent of 

activities in the proposed action. Minimum separation distances between concurrent surveys would, 

however, reduce the potential severity of ensonification from multiple seismic survey sound sources 

within discrete areas of the AOI. Areas selected for closure from deep-penetration seismic airgun 

survey activities were designed to focus on mitigation of deep-penetration seismic airgun impacts to 

a single species or select group of species. Mitigation measures under Alternative B that would 

change the timing and extent of activities in the proposed action include a seasonal restriction for 

operation of airguns in Federal coastal waters. However, survey activities in all other areas of the 

AOI (or in areas adjacent to the closure areas) may potentially impact individual sea turtles during 

the project period. When considering all potential auditory impacts to sea turtles within the AOI from 

proposed seismic airgun activities, along with established impact significance criteria provided in 

Chapter 4.3.2, the mitigation measures included in Alternative B will not appreciably change the 

levels of impacts contributed by Alternative A within the AOI to the cumulative impact as a whole. 

When compared with historic, present, and future activities, including similar non-OCS Program 
4-162 Description of the Affected Resources and Impact Analysis

activities, the cumulative effects of all IPFs to sea turtles within the AOI over the 10-year period 

would result in nominal to minor incremental increases in impacts under Alternative B.

4.3.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.3.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative C on sea turtles. The mitigation measure requiring the 

use of PAM would provide no benefit for sea turtles because sea turtles do not vocalize; therefore, it 

is not discussed further in Alternative C.

4.3.4.1 Impacts of Routine Activities

4.3.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to May 31)

This mitigation measure is described under Alternative B for Federal waters shoreward of the 

20-m (66-ft) isobath (Chapter 4.3.3.1); airgun surveys are not permitted. Under Alternative C, this 

seasonal restriction extends all the way to the shoreline and includes Federal waters from the 20-m 

(66-ft) isobath for a longer season, i.e., from February 1 to May 31 (Figure 2.3-1). Overall, effects of 

this mitigation measure under Alternative C would not reduce potential active acoustic impacts 

discussed under Alternative B (minor for airgun survey activities and nominal to minor for nonairgun HRG survey activities using boomers and sparkers). This mitigation would not alter the 

impacts to sea turtles from vessel and equipment noise, aircraft traffic and noise, trash and debris, or 

entanglement/entrapment; all impacts would remain nominal, while impacts from vessel traffic 

would remain nominal to moderate (if a collision occurred). Though, overall, the chance of impacts 

would decrease by the reduction of activity within coastal waters by 17 percent for the entire 10-year 

period.

4.3.4.1.2 Expanded PSO Program

For Alternative C, the expanded PSO Program will apply to manatees as well as whales 

requiring all airguns will be shut down any time a specific whale species or manatee is detected 

entering or is within the exclusion zone in all water depths. It is assumed that the expansion of this 

operational mitigation measure would reduce the extent of, but not entirely prevent, potential PTS 

auditory injuries to a significant population of sea turtles within the AOI. As discussed in 

Chapter 4.3.3.1, this mitigation measure is expanded to include deep-penetration seismic survey 

operations in all water depths within the AOI and would benefit subadult and adult stages of all sea 

turtle species within the AOI during daylight seismic survey operations (these measures are 

conducted only during daylight hours). Because of their size and cryptic nature within weedlines and 

mats of flotsam, it is not likely that hatchling sea turtles would be sighted by PSOs during monitoring 

surveys. In addition, although these mitigation measures require clearance of the exclusion zone for 

sea turtles prior to start-up, they do not require shutdown for sea turtles; consequently, some 

individual sea turtles may be exposed to sound levels that lead to TTS or PTS auditory injuries. With 

ramp-up requirements, it is assumed that there will be no deaths or life-threatening injuries from 
Gulf of Mexico G&G Activities Programmatic EIS 4-163

airgun activities, even during nighttime ramp-ups (this is based on the assumption that sea turtles 

would move away from the sound source during ramp-up). Most of the effects from active acoustic 

sound sources would consist of behavioral alterations (e.g., avoidance, evasive actions, and 

temporary displacement from the area around the sound source), along with some non-lifethreatening auditory injuries (e.g., threshold shift). Overall, effects of this mitigation measure under 

Alternative C would not reduce potential impacts from project-related IPFs discussed under 

Alternative A (minor for airgun survey activities and nominal to minor for non-airgun HRG survey 

activities using boomers and sparkers). The expansion of the requirements for use of PSOs and 

exclusion zone monitoring in all water depths throughout the GOM may further protect sea turtles 

(during daylight hours) from potential vessel collisions due to the increase in visual observer effort. 

The expansion of PSO monitoring activities to include all water depths within the AOI would reduce 

potential collisions between project vessel traffic and sea turtles. However, the reduction in impacts 

is not expected to change the overall level of impacts from vessel strikes (vessel traffic) for the entire 

AOI, which would remain nominal to minor (if a collision occurred).

Impacts to sea turtles from vessel and equipment noise, aircraft traffic and noise, trash and 

debris, and entanglement, would not be affected by the expansion of seismic survey mitigation 

measures and the PSO Program associated with Alternative C; impacts would remain nominal. 

4.3.4.1.3 Non-Airgun HRG Survey Protocol

Non-Airgun HRG Survey Protocol mitigation measures included under Alternative C include 

pre-survey clearance surveys and shutdowns, as well as the use of PSOs and reporting 

requirements (Appendix B, Attachment B). The measures are linked and are discussed together 

in this chapter. 

Under Alternative C, non-airgun HRG surveys in which one or more active acoustic sound 

sources will be operating at frequencies <200 kHz in all water depths throughout the AOI will require 

a pre-survey clearance of all sea turtles (and marine mammals) for a period of 30 minutes before 

start-up or after a shutdown for all cetaceans (excluding dolphins) or manatees that are within the 

exclusion zone. These surveys must use at least one trained PSO to visually monitor an exclusion 

zone during daylight hours. The exclusion zone would be a 200-m (656-ft) or larger radius zone 

around the sound source. Immediate shutdown of the active acoustic sound source(s) would occur 

if selected marine mammal species (discussed previously) are detected entering or are within the 

exclusion zone. However, sea turtles are not included in this shutdown protocol and therefore could 

still be exposed to the sound levels if seen inside the exclusion zone. Subsequent restart of the 

equipment after shutting down for a marine mammal may only occur following confirmation that the 

exclusion zone is clear of all sea turtles (and marine mammals) for a period of 30 minutes. Overall, 

the implementation of these mitigation measures during non-airgun HRG surveys would reduce 

potential active sound source impacts to sea turtles, particularly during daylight operations. 

However, these measures are designed to protect sea turtles from the start-up of these sources only 

(no shutdowns for sea turtles are required).
4-164 Description of the Affected Resources and Impact Analysis

As discussed in Chapter 4.3.2.2, results from the ScOT report (Appendix G) indicate that 

acoustic outputs from electromechanical sources other than the boomer and sparker are not likely to 

be detectable by sea turtles, whose best hearing is below 1,200 Hz for adults and 1,600 Hz for 

juveniles (Appendix I). If these sources are used and operated at a frequency that is within the 

hearing range of the sea turtle, there could be sound-related impacts (mostly behavioral effects and 

perhaps some TTS-related impacts). Active sound sources with outputs outside of the sea turtle 

hearing range of 50 to 1,200 Hz for adults and up to 1,600 Hz for juveniles (refer to the previous list) 

are not expected to impact sea turtles within the AOI. Boomer or sparker subbottom profilers have 

operating frequency ranges of 300 to 3,000 Hz and 50 to 4,000 Hz, respectively, and so may be 

audible to sea turtles; however, they have very short pulse lengths (120, 150, or 180 μs) and very 

low source levels. Because of expected small 180-dB radius area from the source, potential impacts 

from non-airgun HRG surveys of electromechanical sources using frequencies within the hearing 

ranges of sea turtles would be expected to affect only a few individuals. Impacts would include 

behavioral disturbances and TTS-level auditory impacts. Individual sea turtles may experience longterm auditory injuries (PTS), but they would have to be very close to the electromechanical source to 

experience sound levels capable of PTS injuries. No lethal or population-level impacts from PTS 

auditory injuries are expected. From this analysis, the effects of the Non-Airgun HRG Survey 

Protocol are not expected to reduce overall potential impacts to sea turtles from active acoustic 

sound sources due to daylight limitations and no shutdown protocols. Therefore, non-airgun HRG 

survey impacts to sea turtles are expected to remain the same under Alternative C (nominal to 

minor) and airgun survey impacts would remain minor. 

The requirement for HRG Survey Protocol under Alternative C would not affect potential 

impacts from other IPFs such as vessel and equipment noise, aircraft traffic and noise, trash and 

debris, and entanglement/entrapment; all impacts would remain nominal. The presence of PSOs 

on-board survey vessels could provide additional protection to sea turtles from collisions with 

project-related vessel traffic during daylight hours (it is assumed that PSOs would notify vessel 

operators if a collision is possible). However, PSOs are not expected to maintain watches for sea 

turtles or marine mammals when vessels are not actively collecting data (such as transits), and 

PSOs are not required or effective during nighttime transits or operations. Overall, the increase in 

detectability provided by PSOs during non-airgun HRG surveys will not affect the overall level of 

impact to sea turtles within the AOI from vessel traffic, as discussed under Alternative A (nominal to 

moderate [if a collision occurred]).

4.3.4.1.4 Routine Activities Impact Conclusions

This analysis considered the significance criteria, the AOI, and the 10-year timeframe. 

Mitigation measures that are associated with Alternative C are outlined in Chapter 2.3 and detailed 

in Appendix B. As discussed above, the degree to which these mitigation measures (collectively) 

will affect or change the levels of impact to sea turtles from each project-related IPF (including 

routine activities) is presented below:
Gulf of Mexico G&G Activities Programmatic EIS 4-165

• deep-penetration airgun survey noise – minor; 

• non-airgun HRG electromechanical survey noise – nominal to minor; 

• vessel and equipment noise – nominal; 

• vessel traffic – nominal to moderate; 

• aircraft traffic and noise – nominal; 

• trash and debris – nominal; and

• entanglement and entrapment – nominal. 

These determinations are further outlined and compared against other alternatives in 

Table 2.10-1. 

Implementation of mitigation measures described under Alternative C may reduce potential 

impacts from the IPFs listed above to individuals within the AOI. Impact levels by IPF were 

determined using impact significance criteria discussed in Chapter 4.3.2, and each impact level was 

determined by considering effects to sea turtles within the AOI collectively.

4.3.4.2 Impacts of an Accidental Fuel Spill

Under Alternative C, impacts of an accidental fuel spill on sea turtles would be very similar to 

those analyzed in Chapter 4.3.2.2 for Alternative A. The analysis concluded that a small spill at the 

sea surface would result in nominal (if the fuel does not contact individual sea turtles) to minor (if 

individual sea turtles encounter the dispersed windrows of the surface slick) impacts.

4.3.4.3 Cumulative Impacts

Impact analyses presented in Chapters 4.3.2.1 and 4.3.2.2 determined that activities 

projected to occur under Alternative B would result in nominal to moderate impacts to sea turtles, 

depending on the IPF.

The cumulative assessment for Alternative A in Chapter 4.3.2.3 compared with historic, 

present, and future activities, including similar non-OCS Program activities, evaluated cumulative 

activities with similar IPFs to the proposed activities and spatial and temporal occurrence, and it 

concluded that the cumulative effects of all IPFs to sea turtles within the AOI over the 10-year period 

would result in nominal to minor incremental increases in impacts.

Mitigation measures under Alternative C would not change the extent of activities in the 

proposed action. One measure would change the timing of activities in the proposed action by 

means of a seasonal restriction for operation of airguns in Federal and State coastal waters. 

Alternative C would change the timing of seismic airgun surveys in certain areas; however, the 

seasonal restriction and operational mitigation measures would not appreciably change the 

cumulative impacts determined under Alternative A, resulting in nominal to minor incremental 
4-166 Description of the Affected Resources and Impact Analysis

increases in impacts. Though incrementally, the reduction could be considered to have nominal

impacts. 

4.3.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative D are the same as for 

Alternative A (Chapter 4.3.2). The additional mitigation measure under Alternative D would not 

reduce potential active acoustic impacts discussed under Alternatives A and C (Chapters 4.3.2.1 

and 4.3.4.1).

4.3.5.1 Impacts of Routine Activities

The additional mitigation measure under Alternative D, exclusion of bow-riding dolphins from 

shutdown protocols, would not change the extent, severity, or timing of IPFs outlined in 

Alternatives A and C for sea turtles. Impacts would remain as under Alternatives A to C, i.e,,

nominal to minor for non-airgun HRG survey activities and minor for airgun survey activities. This 

mitigation would not alter the expected impact levels to sea turtles from vessel and equipment noise, 

aircraft traffic and noise, trash and debris, or entanglement/entrapment, and would remain nominal, 

while impacts from vessel traffic would remain nominal to moderate (if a collision occurred).

4.3.5.2 Impacts of an Accidental Fuel Spill

Under Alternative D, impacts of an accidental fuel spill on sea turtles would be similar to 

those analyzed in Chapter 4.3.2.2 for Alternative A. The risk of a small fuel spill and its potential 

impacts on sea turtles within the AOI would be the same as under Alternative A, i.e., nominal (if the 

fuel does not contact individual sea turtles) to minor (if individual sea turtles encounter the dispersed 

windrows of the surface slick) impacts, depending on the numbers of individuals adversely affected 

by the spill.

4.3.5.3 Cumulative Impacts

Impact analyses presented in Chapters 4.3.5.1 and 4.3.5.2 determined that activities 

projected to occur under Alternative D would result in nominal to moderate impacts to sea turtles, 

depending on the IPF.

The cumulative assessment for Alternative A in Chapter 4.3.2.3 compared with historic, 

present, and future activities, including similar non-OCS Program activities, evaluated cumulative 

activities with similar IPFs to the proposed activities, spatial and temporal occurrence, and 

concluded that the cumulative effects of all IPFs to sea turtles within the AOI over the 10-year period 

would result in nominal to minor incremental increases in impacts.

Mitigation measures for the proposed action under Alternative D are the same as described 

for Alternative C, with the addition of shutdown protocols during seismic operations for all marine 

mammals (except bow-riding dolphins). The addition of shutdown protocols for all marine mammals, 

except bow-riding dolphins, under Alternative D would not change the extent, severity, or timing of 
Gulf of Mexico G&G Activities Programmatic EIS 4-167

activities in the proposed action, resulting in nominal to minor incremental increases in cumulative 

impacts to sea turtles under Alternative D.

4.3.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.3.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative E on sea turtles.

4.3.6.1 Impacts of Routine Activities

4.3.6.1.1 Reduced Level of Activity

Alternative E includes a reduction of G&G activity levels by 10 percent (Alternative E1) or 

25 percent (Alternative E2). This measure is not restricted to any specific area of the AOI; therefore, 

it is not practicable in this analysis to assess areas that maximize impact mitigation for sea turtles 

(such as areas that are offshore of known coastal nesting habitats for certain species). The overall 

reduction in activities would proportionately reduce impacts to sea turtles from active acoustic sound 

sources, but the impact levels over the AOI over the 10-year period would not be significantly 

reduced.

Alternative E1 specifies a 10 percent reduction and Alternative E2 specifies a 25 percent 

reduction of deep seismic activities, which would both proportionately reduce potential impacts from 

seismic survey IPFs to sea turtles in the AOI. This would reduce the extent, severity, and timing of 

seismic survey-related sound sources, vessel and equipment noise, vessel traffic, support helicopter 

traffic and noise, and trash and debris within the AOI and proportionately decrease impacts from 

these IPFs on sea turtles. However, with no information regarding the area(s) where activity would 

be restricted, proposed deep-penetration survey activities may occur within open areas of the AOI, 

and individual sea turtles may still be at risk from potential impacts from these IPFs. Impacts to sea 

turtles within the AOI under Alternatives E1 and E2 from project-related IPFs range from nominal to 

minor for airgun survey activities and non-airgun HRG survey activities using boomers and 

sparkers, nominal to moderate (if a collision occurred) for vessel traffic, and nominal for vessel and 

equipment noise, aircraft traffic and noise, trash and debris, and entanglement/entrapment.

4.3.6.2 Impacts of an Accidental Fuel Spill

Under Alternative E, impacts of an accidental fuel spill on sea turtles would be very similar to 

those analyzed for Alternative A in Chapter 4.3.2.2. The risk of a small fuel spill and its potential 

impacts on sea turtles within the AOI would be the same as under Alternative A, i.e., nominal (if the 

fuel does not contact individual sea turtles) to minor (if individual sea turtles encounter the dispersed 

windrows of the surface slick) impacts, depending on the numbers of individuals adversely affected 

by the spill.
4-168 Description of the Affected Resources and Impact Analysis

4.3.6.3 Cumulative Impacts

Impact analyses presented in Chapters 4.3.6.1 and 4.3.6.2 determined that activities 

projected to occur under Alternative E would result in nominal to moderate impacts to sea turtles, 

depending on the IPF. The cumulative assessment for Alternative A in Chapter 4.3.2.3 compared 

with historic, present, and future activities, including similar non-OCS Program activities, evaluated 

cumulative activities with similar IPFs to the proposed activities, spatial and temporal occurrence, 

and concluded that the cumulative effects of all IPFs to sea turtles within the AOI over the 10-year 

period would result in nominal to minor incremental increases in impacts.

Mitigation measures for the proposed action under Alternative E would reduce the extent, 

severity, and timing of active acoustic sound sources, vessel and equipment noise, vessel traffic, 

aircraft traffic and noise, trash and debris, and entanglement/entrapment; therefore, impacts for 

these IPFs would be proportionately decreased under Alternative E. The reduction in survey line 

miles would not appreciably change the cumulative impacts noted under Alternative A and would 

result in nominal to minor incremental increases in impacts.

4.3.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.3.2). Some mitigation measures associated with Alternative F, such as 

PAM requirements and the expanded PSO Program to include protective measures for manatees, 

do not apply to sea turtles (as discussed in Chapter 4.3.1.4) and are not discussed in this analysis. 

The following discussion outlines the effects of the additional mitigation measures included under 

Alternative F that may affect sea turtles.

4.3.7.1 Impacts of Routine Activities

4.3.7.1.1 Closure Areas

Alternative F includes four area closures: the CPA Closure Area; the EPA Closure Area; the 

Dry Tortugas Closure Area; and the Flower Gardens Closure Area. These areas are shown in 

Figure 2.6-1. Historic survey data collected along the continental shelf edge and slope of the GOM 

suggest that adults of a few sea turtle species occur within these environments, primarily 

leatherback and loggerhead sea turtles (Lohoefener et al., 1990; Davis et al., 2000). These areas 

also support hatchling sea turtles in the GOM.

While there may be some reduction of impacts to sea turtles within the closure areas, overall 

the additional mitigation measures under Alternative F would not change the extent or severity of the 

IPFs in the majority of the AOI; consequently, the effects of this mitigation measure would not reduce 

potential active acoustic impacts (i.e., minor for airgun survey activities and nominal to minor for 

non-airgun HRG survey activities using boomers and sparkers). Impacts from vessel traffic would 

remain nominal to moderate (if a collision occurred). This mitigation would not alter the impacts to 

sea turtles from vessel and equipment noise, aircraft traffic and noise, trash and debris, or 

entanglement/entrapment; all impacts would remain nominal. 
Gulf of Mexico G&G Activities Programmatic EIS 4-169

4.3.7.2 Impacts of an Accidental Fuel Spill

Under Alternative F, impacts of an accidental fuel spill on sea turtles would be similar to 

those analyzed in Chapter 4.3.2.2 for Alternative A. The risk of a small fuel spill and its potential 

impacts on sea turtles within the AOI would be the same as under Alternative A, i.e., nominal (if the 

fuel does not contact individual sea turtles) to minor (if individual sea turtles encounter the dispersed 

windrows of the surface slick) impacts, depending on the numbers of individuals adversely affected 

by the spill.

4.3.7.3 Cumulative Impacts

Impact analyses presented in Chapters 4.3.7.1 and 4.3.7.2 determined that activities 

projected to occur under Alternative F would result in nominal to moderate impacts to sea turtles, 

depending on the IPF. The cumulative assessment for Alternative A in Chapter 4.3.2.3 compared 

with historic, present, and future activities, including similar non-OCS Program activities, evaluated 

cumulative activities with similar IPFs to the proposed activities, spatial and temporal occurrence, 

and concluded that the cumulative effects of all IPFs to sea turtles within the AOI over the 10-year 

period would result in nominal to minor incremental increases in impacts.

Mitigation measures under Alternative F are similar to Alternative C with the addition of area 

closures in four areas: the CPA Closure Area; the EPA Closure Area; the Dry Tortugas Closure 

Area; and the Flower Gardens Closure Area. Alternative F would change the timing of seismic 

airgun surveys in certain areas (the coastal seasonal restrictions) and restrict new airgun and nonairgun HRG surveys in portions of the AOI; however, these restrictions would not appreciably 

change the cumulative impacts noted under Alternative A, resulting in nominal to minor incremental 

increases in impacts.

4.3.8 Impacts – Alternative G (No New Activity Alternative)

Since Alternative G is no new activity, any existing permitted activity and ancillary activities 

would be ongoing, and the mitigation measures would be the same as for Alternative A. The activity 

level would then slowly decline over a period of several years. For this reason, IPFs and impact 

significance criteria applied for Alternative G are the same as for Alternative A (Chapter 4.3.2), 

except that the IPF of entanglement/entrapment is not included as part of Alternative G because no 

OBC/nodal surveys are part of the alternative.

4.3.8.1 Impacts of Routine Activities

4.3.8.1.1 Active Acoustic Sound Sources

The only survey activities that would occur under this alternative are VSP and SWD surveys. 

Appendix F, Section 1.1.5 provides descriptions of these surveys, which include the use of airgun 

active acoustic sources. Sound source characteristics are summarized in Table 3.4-2, and detailed 

characteristics and acoustic modeling assumptions are presented in Appendix D. The potential 

impacts of zero-offset and walkway VSP and SWD surveys are the same as those that would occur 
4-170 Description of the Affected Resources and Impact Analysis

with Alternative A (Chapter 4.3.2.1), however, at greatly reduced impact levels commiserate with the 

reduction in survey effort (Table 2.7-1). No impacts to local populations are expected; impacts 

would be limited to minimal short-term behavioral or other low-level impacts on individuals (low 

numbers, low severity, and short duration). Therefore, effects of project-related seismic airgun 

survey noise on sea turtles within the AOI are expected to be reduced from Alternative A (nominal

to minor) to nominal declining to no impact under Alternative G.

4.3.8.1.2 Vessel and Equipment Noise

The G&G activities that would continue under Alternative G would generate vessel and 

equipment noise that could disturb sea turtles. The potential impacts are the same as those that 

would occur with Alternative A (Chapter 4.3.2.1), however, at greatly reduced impact levels 

commiserate with the level of ongoing activities (Table 2.7-1). Based on the existing vessel traffic 

within the AOI, the effects of the project-related vessel and equipment noise on sea turtles within the 

AOI would be nominal declining to no impact. As described previously, minimal drilling related to 

G&G activities is projected to occur under Alternative G and would include drilling only one COST 

well; therefore, minimal to no equipment noise impacts will occur from drilling.

4.3.8.1.3 Vessel Traffic

The potential impacts (physical disturbance from or collision with moving vessels) are the 

same as those that would occur with Alternative A (Chapter 4.3.2.1), with the same impact level 

(nominal to moderate) but would then decline to no impact. When considering the impact 

significance criteria, if a collision occurs, it would result in a death or injury; therefore, impacts would 

be minor declining to no impact. 

4.3.8.1.4 Aircraft Traffic and Noise

The potential impacts (noise and physical disturbance) are the same as those that would 

occur with Alternative A (Chapter 4.3.2.1), with the same impact level (nominal) but would then 

decline to no impact. 

4.3.8.1.5 Trash and Debris

The potential impacts from trash and debris are the same as those that would occur with 

Alternative A (Chapter 4.3.2.1), with the same impact level (nominal) but would then decline to no 

impact. 

4.3.8.1.6 Routine Activities Impact Conclusions

Overall, the removal of all new G&G survey activities within the AOI, as described under 

Alternative G, would reduce potential impacts from the IPFs listed above to sea turtles within the 

AOI. However, G&G activities previously authorized under an existing permit/authorization or lease 

would proceed under Alternative G. Impacts from active acoustic sound sources are reduced from 

Alternative A to nominal declining to no impact due to the reduction in activities. Impact levels 
Gulf of Mexico G&G Activities Programmatic EIS 4-171

from vessel traffic would remain nominal to moderate (if a collision occurred) but would then 

decline to no impact. The impact level for vessel and equipment noise, aircraft traffic and noise, 

and trash and debris would remain nominal. These determinations are further outlined and 

compared against other alternatives in Table 2.10-1. 

4.3.8.2 Impacts of Accidental Events

Under Alternative G, impacts of an accidental fuel spill on sea turtles would be similar to 

those analyzed in Chapter 4.3.2.2 for Alternative A. The risk of a small fuel spill and its potential 

impacts on sea turtles within the AOI would be the same as under Alternative A, i.e., nominal (if the 

fuel does not contact individual sea turtles) to minor (if individual sea turtles encounter the dispersed 

windrows of the surface slick) impacts, depending on the numbers of individuals adversely affected 

by the spill, but this would decline to no impact as activities ended.

4.3.8.3 Cumulative Impacts

A detailed impacts assessment under the cumulative scenario is provided in Alternative A 

(Chapter 4.3.2.3). The cumulative impact analysis identified nominal to minor incremental 

increases in impacts from all IPFs under Alternative A. The cumulative scenario would remain 

unchanged for Alternative G, except that no additional impacts to the IPF of entanglement would 

occur, and the associated impacts would remain the same. Therefore, there is no appreciable 

change to the cumulative impacts determined under Alternative A, resulting in a nominal

incremental increases in impacts.

4.4 FISH RESOURCES AND ESSENTIAL FISH HABITAT

4.4.1 Description of the Affected Environment

The AOI covers a broad geographic and bathymetric region ranging from the shoreline to the 

open ocean and features a mix of fish resources that includes estuarine, coastal, and oceanic 

species associated with demersal (defined in Appendix E, Section 4) and pelagic (the open water 

environment) habitats. Distributions vary in species-specific fashion relative to major environmental 

factors such as water depth, salinity, temperature, and habitat type. Fish resources covered in this 

chapter include threatened and endangered species managed by NMFS and FWS as part of the 

ESA, as well as EFH and species managed under the Magnuson-Stevens Fishery Conservation Act 

by the GMFMC and the NMFS Highly Migratory Species Division of the Office of Sustainable 

Fisheries. Many federally managed fish species spend all or part of their life cycle in the AOI, 

resulting in the majority of the AOI designated as EFH. The EFH is defined as “those waters and 

substrate necessary to fish for spawning, breeding, feeding or growth to maturity” [16 U.S.C. § 

1801(10)]. “Fish” includes “finfish, mollusks, crustaceans, and all other forms of marine animal and 

plant life other than marine mammals and birds,” whereas “spawning, breeding, feeding or growth to 

maturity” covers the complete life cycle of those species of interest. The EFH is further described in 

detail in Appendix E, Section 4. 
4-172 Description of the Affected Resources and Impact Analysis

The proposed AOI includes critical habitat for two endangered fish species that are managed 

by NMFS and FWS as part of the ESA. Smalltooth sawfish (Pristis pectinata) (68 FR 15674) 

distribution in the AOI is limited to the waters of southwest Florida and Florida Bay, primarily within 

the jurisdictional boundaries of Everglades National Park (Simpfendorfer and Wiley, 2005; USDOC, 

NMFS, 2009) (Figure 4.4-1). Gulf sturgeon (Acipenser oxyrinchus desotoi) (68 FR 13370) reside 

primarily in estuaries and rivers, and enter the AOI only seasonally in western Florida (Figure 4.4-1). 

Nassau grouper (Epinephelus striatus) (81 FR 42268) is listed as threatened and, although occurring 

in the AOI, is typically replaced by red grouper (Epinephelus morio) north of Key West and is 

considered transient or rare in the northern and northwestern GOM. Species that are candidates for 

becoming listed as threatened or endangered species include the dusky shark (Carcharhinus 

obscurus) (78 FR 29100), and great hammerhead shark (Sphyrna mokarran) (78 FR 24701). 

Species of concern, as defined under the ESA, in the AOI include the Alabama shad (Alosa 

alabamae), dusky shark, sand tiger shark (Carcharias taurus), speckled hind (Epinephelus 

drummondhayi), and Warsaw grouper (Epinephelus nigritus) (USDOC, NMFS, 2015c).

The demersal or bottom-dwelling fish fauna of the continental shelf separates broadly into 

soft bottom and hard bottom assemblages. The EPA (west Florida shelf) shelf has vast areas of soft 

bottom composed mostly of carbonate sediment interspersed with stands of seagrasses and 

macroalgae, which attract diverse assemblages of fishes including herrings, pipefishes, snappers, 

grunts, porgies, drums, gobies, smooth puffers, and filefishes. In the CPA and WPA, sedimentary 

bottom covers most of the shelf and upper slope. Sediments are muddy on the inner shelf, 

particularly in the CPA, and coarse along the outer shelf. Soft bottom fish assemblages in these 

areas are characterized by croakers, drums, sea robins, porgies, and flatfishes. Soft bottom habitats 

are designated EFH for penaeid shrimps (Chapter 4.5.1) and red drum by the GMFMC (2004).

Hard bottom habitat is most extensive in the EPA where relatively low-relief (<1 m [3 ft]) rock 

characterizes much of the west Florida shelf and is composed of a mosaic of coral reefs and 

epibenthic communities (Jaap, 2015). Low-relief hard bottom on the inner shelf in the CPA and 

WPA is very limited when compared with that known for the EPA. These inner shelf reefs, which 

exist in water depths ranging from nearshore to approximately 30 m (98 ft), support snappers, 

porgies, grunts, damselfishes, groupers, sea basses, and other reef fish species. In water depths 

exceeding 30 m (98 ft) where reduced light penetration excludes most plants and herbivores, a 

distinctive “mesophotic” hard bottom assemblage occurs (Koenig et al., 2000; Weaver et al., 2002

and 2006). Mesophotic reef systems colonized by sponges, hydrozoan, soft corals, and tunicates 

are found in all planning areas. Fish assemblages on mesophotic reefs are composed of snappers, 

groupers, sea basses, wrasses, bigeyes, butterflyfishes, angelfishes, jacks, and other reef-dwelling 

species, and are found on the continental shelf edge of all planning areas (Dennis and Bright, 1988;

Koenig et al., 2000; Continental Shelf Associates, Inc. and Texas A&M University, 2001; Weaver 

et al., 2002). Table 4.4-1 provides information on hard bottom species with EFH identified within the 

AOI. Hard bottom habitats represent EFH for members of the reef fish management (snappers, 

groupers, tilefishes, jacks, triggerfishes, and wrasses) unit overseen by the GMFMC. The GMFMC 

also manages corals and coral EFH, which are discussed in Chapter 4.5.1. 
Gulf of Mexico G&G Activities Programmatic EIS 4-173

Fishes (e.g., red snapper) that inhabit hard bottom in the GOM may also associate with 

artificial habitat, including oil and gas structures, artificial reefs, shipwrecks, and other debris (refer to 

Szedlmayer and Lee, 2004; Gallaway et al., 2009). Artificial structures create an environment 

conducive to the settlement (and attraction) of shallow-water tropical reef fishes in the upper water 

column and mesophotic species in depths >30 m (98 ft) (Stanley and Wilson, 2000) (refer to

Chapter 4.3.1.2). While these are not considered EFH, they present habitats where fish can 

concentrate near structures and be impacted by IPFs under the proposed scenario.

The primary water column fish assemblage found in coastal and shelf waters of the GOM is 

termed coastal pelagic. Major coastal pelagic fishes occurring in the GOM are sharks, rays, ladyfish, 

anchovies, herrings, mackerels, little tunny, jacks, mullets, bluefish, and cobia. Individual species 

(king mackerel, Spanish mackerel, and cobia) managed jointly by the GMFMC and South Atlantic 

Fishery Management Council (SAFMC) are termed coastal migratory pelagic species. In addition to 

these species, coastal sharks managed by NMFS’ Highly Migratory Species Division of the Office of 

Sustainable Fisheries have EFH designated within the AOI. Tables 4.4-2 and 4.4-3 provide 

information on coastal migratory pelagic species with EFH identified within the AOI.

Epipelagic fishes inhabit the upper 200 m (656 ft) of the water column and include several 

sharks, billfishes, tunas, dolphins, flyingfishes, halfbeaks, opahs, oarfishes, jacks, remoras, 

pomfrets, butterfishes, molas, and triggerfishes. Epipelagic fishes including sharks, tunas, 

swordfish, and other billfishes are managed by NMFS’ Highly Migratory Species Division of the 

Office of Sustainable Fisheries. Tables 4.4-3 and 4.4-4 provide information on highly migratory and 

shark species, respectively with EFH identified within the AOI. Several highly migratory species 

such as dolphinfish (Coryphaena hippurus and C. equisetis), sailfish (Istiophorus platypterus), white 

marlin (Kajikia albida), blue marlin (Makaira nigricans), and tunas (Thunnus spp.) are important to 

commercial and/or recreational fisheries. Most of these species associate with offshore structures in 

transient fashion, usually in response to the availability of prey. Floating seaweed (Sargassum), 

jellyfishes, siphonophores, and logs and other debris attract juvenile and adult epipelagic fishes. 

Most fish associated with Sargassum are temporary residents, such as juveniles of species that 

reside in shelf or coastal waters as adults (e.g., jacks, triggerfishes, and filefishes). However, 

several larger species of recreational or commercial importance, including dolphinfish, yellowfin 

tuna, blackfin tuna, skipjack tuna, Atlantic bonito, little tunny, and wahoo, feed on the small fishes 

and invertebrates attracted to Sargassum (Dooley, 1972; Bortone et al., 1977; Wells and Rooker, 

2004a and 2004b).

Below the epipelagic zone, the water column may be layered into mesopelagic (200 to 

1,000 m [656 to 3,280 ft]) and bathypelagic (>1,000 m [3,280 ft]) zones, known as the midwater 

area. Lanternfishes are small silvery fishes that can be extremely abundant. No EFH is designated 

for any members of the mesopelagic group, but many are important prey for other managed species.

Demersal fishes are those that are either in direct contact with the substrate or hover above 

it from the shelf-slope transition down to the abyssal plain. The deep-sea demersal fish fauna in the 

GOM includes approximately 300 species.
4-174 Description of the Affected Resources and Impact Analysis

4.4.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, the IPFs that may impact fish resources and EFH within the AOI 

include (1) active acoustic sound sources (e.g., airguns; non-airgun HRG sources such as highresolution boomers, sparkers, and CHIRP subbottom profilers; SBESs and MBESs; and side-scan 

sonars); (2) vessel and equipment noise; (3) trash and debris; (4) seafloor disturbance; (5) drilling 

discharges; (6) entanglement (i.e., with acoustic buoy releases, tethered acoustic pingers, and nodal 

tethering lines); and (7) accidental fuel spills.

There is little specific information on any of these IPFs in relation to fish resources or EFH in 

the AOI. However, based on studies of fish (individual and population) from other waterbodies, it is 

likely that members of the regional fish community discussed in Chapter 4.1 could be affected to 

some degree by G&G activities. Thus, impact levels were developed based on available literature 

and studies on the effects of the IPFs to individual fish and populations of fish from other 

waterbodies.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact level. In contrast, the analysis of impacts 

associated with Alternatives B through G are organized by alternative-specific mitigation measures 

and how each of these measures may reduce impact levels.

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For fish resources 

and EFH, the significance criteria below have been used to evaluate the level of impact for each IPF.

Nominal impacts to fish resources and EFH would include those where little to no 

measurable impacts are observed or expected. There would not be any adverse effects on a 

federally managed fish species or EFH.

Minor impacts to fish resources and EFH would include those that are detectable but are 

neither severe nor extensive. Minor impacts to fish resources and EFH would include temporary 

displacement or disruption of important behavioral patterns of federally managed fish species. Minor 

impacts would include physical injuries or mortalities of a small (limited) number of individuals. 

Minor impacts also would include spatially limited impact to EFH.

Moderate impacts to fish resources and EFH would be detectable and extensive but not 

severe. Moderate impacts to fish resources and EFH would include some degree of population-level 

physiological/anatomical damage to, population-level mortality to, or extended displacement of large 

numbers of (i.e., population-level) a federally managed fish species. Moderate impacts also would 
Gulf of Mexico G&G Activities Programmatic EIS 4-175

include extensive damage (quantifiable loss depending on the habitat type) to EFH and extensive 

disruption of behavioral patterns (including spawning, feeding, or ontogenetic [age-related] 

migrations) that may adversely affect a species.

Major impacts to fish resources and EFH would be detectable, extensive, and severe. Major 

impacts to fish resources and EFH would include a high level of physiological/anatomical damage to, 

mortality to, or long-term displacement of a federally managed fish species. Major impacts would 

also include extensive, long-term damage (quantifiable loss depending on the habitat type) to EFH, 

or extensive, chronic disruption of behavioral patterns (including spawning, feeding, or ontogenetic 

migrations) that would adversely affect a species.

4.4.2.1 Impacts of Routine Activities

4.4.2.1.1 Background: Potential Effects of Noise on Fishes

There are no studies on the impacts of sound to species of fish, fish populations, or EFH in 

the AOI. There are studies that investigate the effects of sound on species from other waterbodies, 

and these studies are discussed in this chapter in order to provide a framework for inferring impacts 

expected in the AOI. This chapter focuses on the most common and likely direct effects from active 

acoustic sound sources. Before considering these direct effects, it is important to realize that sound 

plays a major role in the lives of all fishes and is used to perform many life-sustaining functions, e.g., 

prey capture and foraging, predator avoidance, mating, spawning, or territorial disputes (Zelick et al., 

1999). Fish utilize the soundscape and components of sound in their environment to perform these 

functions (Fay, 2009). Depending on their hearing anatomy and peripheral sensory structures, 

which vary among species, fishes hear sounds using pressure and particle motion sensitive 

capabilities and detect the motion of surrounding water (Popper et al., 2008). Information on the 

physics of underwater sound, mechanics of fish hearing, and auditory anatomy and physiology is 

discussed in Appendix J. Fishes hear within a frequency range of 25 Hz to 3kHz, with sharks and 

rays (including smalltooth sawfish) at the lower end of this range and herrings, which have 

specialized anatomy (connection between gas-filled swim bladder and the inner ear) that enhances 

their ability to hear high-frequencies, at the higher end. This hearing range overlaps with the 

frequency ranges of several G&G-related noise sources—seismic airguns range from 1 to 100 Hz. 

A fish’s ability to detect a biologically relevant sound will decrease in the presence of a background 

noise in the same frequency range. The potential direct effects depend not only on this overlapping 

frequency range but also on the distance of an organism from a sound source, water depth of 

exposure, and species-specific hearing sensitivity, anatomy, and physiology. In order of increasing 

likelihood with decreasing distance from a sound source, the key impacts include the following: 

• behavioral responses;

• masking;

• TTS (hearing loss);
4-176 Description of the Affected Resources and Impact Analysis

• barotrauma (pressure-related injuries); and

• mortality.

Behavioral responses (e.g., fleeing or avoidance) to active acoustic sound sources are the 

most likely direct effects for the majority of fish resources exposed to sound within the AOI. Fewtrell 

and McCauley (2012) found that fish exhibited alarm responses to airgun noise at levels exceeding 

147 to 151 dB re 1 μPa2

•s SEL. Wardle et al. (2001) also noted that fish elicited an alarm response 

to seismic airgun sounds, but no overall change in fish behavior was observed. Reaction of fish to 

seismic airguns is species specific and may depend on the physiological state of the fish. For 

example, Peña et al. (2013) noted schools of feeding herring did not react to seismic airgun sounds. 

Masking (auditory masking) occurs when sounds in the environment are in the same 

frequency range as a sound of biological relevance to the animal or within the hearing range of the 

fishes. The potential for masking or behavioral response may exist at a distance of many kilometers 

from a sound source, depending on the ambient background sound level and the frequency and 

amplitude characteristics of the propagated sound. Fish species in the candidate and non-listed 

categories described in Chapter 4.4.1 and Appendix E, including some federally managed species, 

utilize sound to some extent for sensing their environment (which includes other sound-producing 

species), calling to mates, sensing predators, or warding off aggressors (Rountree et al., 2006). 

Demersal soft bottom species best known for their use of sound in reproductive signaling are the 

drums (Sciaenidae), including the federally managed red drum. Because most species of this family 

(weakfish, black drum, silver perch, and Atlantic croaker) engage in species-specific chorusing 

during spawning periods, passive acoustic instruments have been used to identify spawning areas 

inside bays and estuaries (Mok and Gilmore, 1983; Rountree et al., 2006; Luczkovich et al., 2008). 

It is reasonable to assume that some sciaenid taxa use sound to coordinate spawning activities in 

coastal and shelf waters of the AOI (Holt, 2008). Other demersal families known to produce sounds 

include stargazers, cusk-eels, and hakes. Several hard bottom demersal taxa such as groupers, 

drums, grunts, porgies, squirrelfishes, damselfishes, toadfishes, grenadiers, and gobies produce 

sounds that may be ecologically important (Myrberg and Fuiman, 2002; Rountree et al., 2006). 

Some pelagic species, particularly herrings, have a very broad range of hearing, which may allow 

them to detect the ultrasonic clicks from cetacean predators (Mann et al., 1997).

The TTS occurs following overstimulation from sound, which results in damage to auditory 

hair cells and decreased hearing sensitivity. Fish are more susceptible to TTS within their most 

sensitive hearing range (refer to Appendix J). In some cases, the sensory cells lining the auditory 

system of fishes have been damaged by sounds produced by airguns (McCauley et al., 2003). 

Popper (2005) and Wardle et al. (2001) noted that the potential for pathological damage (i.e., to

hearing structures) depends on the energy level of the received sound, its rise time, and the specific 

hearing characteristics of the species of interest. Few studies have assessed the pathological 

effects of seismic sound on fishes; available exposure study results also carry notable caveats (i.e., 

repetitive sound exposures are greater than would be realized by fishes during a seismic survey). 

McCauley et al. (2003) found that exposure to airgun sounds (i.e., peak to peak SPL of 
Gulf of Mexico G&G Activities Programmatic EIS 4-177

approximately 223 dB re 1 μPa; exposure to 600 pulses) produced observable anatomical damage 

to the auditory maculae (region containing specialized cells) of pink snapper (Sparidae). In most fish 

species, hair cells in the ear continuously regenerate, and loss of auditory function is likely restored 

when damaged cells are replaced with new cells. Such impacts would be most severe when the 

individual is close to the source and when the duration of exposure is long.

Barotrauma caused by decompression is the mechanism of injury. Injuries can potentially 

range from slight to severe or can cause death if the organism’s fitness is compromised. Refer to

Appendix J for a detailed explanation of barotrauma and the effects of decompression to fish. 

Several controlled impulsive pile-driving studies (a proxy for airgun signals) showed swim bladder 

damage in Chinook salmon and documented barotrauma injuries in other species (Halvorsen et al., 

2012a and 2012b; Casper et al., 2013a). However, Casper et al. (2012, 2013a, and 2013b) showed 

recovery rates of approximately 10 days for multiple species held in the laboratory. If injury were to 

occur, fish without swim bladders would be significantly less susceptible and fish with swim bladders 

or other gas-filled chambers would be more susceptible to barotrauma and mortality from G&G 

activities. Additionally, with increasing depth and range from the source, a pressure change caused 

by sound poses less risk of barotrauma to fish (refer to Appendix J, Section 5.4). In most seismic 

airgun surveys, the sound source is constantly moving. The assumption is that adult or juvenile fish 

would not be exposed to sounds intense enough to cause physiological or anatomical damage 

because they would swim away from the sound source during its approach. During typical seismic 

airgun surveys, source vessels travel at 4.5 to 6 kn (5.2 to 7 mph) so that the towed airgun array 

moves on the order of 37 to 49 m (121 to 161 ft) between seismic pulses, assuming that the airgun 

array is fired every 10 to 15 seconds (Richardson et al., 1995). Thus, given the assumed fish 

avoidance behavior, ramp-up protocols for airgun surveys, the mobile nature of the seismic surveys, 

the potential for regeneration of damaged hair cells, and the low likelihood of conditions for 

barotrauma, impulsive sound from airguns would cause a minor impact to fish at the population 

level.

Mortality may occur in close proximity to a sound source (e.g., from seismic airguns) when 

there is a rapid rise and the peak pressures (positive or negative) differ substantially from the 

ambient pressure at the receiver’s location. Outside the near vicinity of seismic sound sources at 

shallower depths, the potential for barotrauma and mortality is less. There is only limited data on 

mortality in response to anthropogenic noises, particularly from airguns, and it is not clear whether 

death or injury only occurs in close proximity to a sound source (Hawkins et al., 2014). Overall, it is 

more likely that fish will experience sublethal impacts that increase the possibility for delayed 

mortality (Hawkins et al., 2014). Because G&G sound sources produce low-frequency sounds that 

are within the sensitive hearing range of most fish, the potential for fish to experience TTS, masking, 

and behavioral impacts are a higher likelihood.

Few studies have investigated the effects of airgun noise on fish eggs and larvae, and the 

results are equivocal (Popper and Hastings, 2009). Eggs and larvae are passive or have limited 

motion and so may be effectively considered as stationary objects with regard to a moving sound 

source. Results indicate that mortality to eggs may occur close to airguns (within 1.4 m [4.6 ft]) but 
4-178 Description of the Affected Resources and Impact Analysis

that effects of seismic airgun noise on fish eggs and larvae were indistinguishable from natural 

variability (Booman et al., 1996; Saetre and Ona, 1996). Cox et al. (2012) indicated that mortality of 

trout eggs to a single airgun exposure was 100 percent at 0.1 m (0.3 ft) but not significantly different 

than the control group at 2.7 m (8.6 ft). A study found that common sole (Solea solea) larvae 

exposed to impulsive pile-driving sounds did not experience a significant increase in mortality (Bolle 

et al., 2012).

4.4.2.1.2 Analysis of Active Acoustic Sound Sources

Active acoustic sound sources in the proposed action include two general types: airguns 

and non-airgun HRG (electromechanical) sources (Chapter 3.3.1.1). Operating frequencies and 

sound source levels for airguns and electromechanical sources are presented in Table 3.3-2. 

Deep-Penetration Seismic Airgun Survey Activities

Airguns are used as the seismic source for deep-penetration seismic airgun surveys and 

HRG surveys for oil and gas exploration. Other non-airgun HRG surveys use boomers, sparkers, 

CHIRP subbottom profilers, side-scan sonar, and MBESs. The HRG and VSP activities are 

expected to have the highest number of events, whereas deep-penetration 3D and 4D surveys are 

expected to have the longest durations and scale of activity (Table 3.2-8). For example, 3D and 4D 

surveys cover large areas during relatively long operational periods (2 to 12 months); HRG surveys 

focus on individual or groups of OCS lease blocks. Thus, with HRG surveys, the area exposed to 

airgun noise would be smaller, survey trackline density would be higher, and survey duration would 

be shorter (days rather than months) than deep-penetration surveys. Longer duration, deeppenetration surveys over large areas would have a high likelihood of temporarily exposing fishes to 

impulsive seismic sound. Depending on water depth, these fish would include coastal pelagic, 

epipelagic, and demersal hard bottom species. The HRG surveys using airguns that are focused on 

smaller areas could expose smaller number of fishes to higher levels of sound than could deeppenetration surveys. Long duration but widespread versus short duration over small areas presents 

different sound exposure situations, both of which could result in adverse impacts to fishes. 

Repeated passes by a seismic survey vessel conducting an HRG site-specific survey could displace 

or disrupt spawning behavior of federally managed grouper and snapper species and other fishes. 

According to Slabbekoorn et al. (2010), no studies have been conducted to assess the effect of 

seismic sound on the spawning activity of fish. Some data exist on the effect of approaching vessel 

traffic on spawning behavior for some fish species and are discussed in Chapter 4.4.2.1. 

Fishes exposed to sound might move away from the sound source, experience TTS (hearing 

loss), experience masking of biologically relevant sounds, or show no obvious direct effects. 

Mortality is unlikely for reasons stated previously. Surveys using towed airgun arrays move through 

an area relatively quickly, limiting the exposure of fishes to multiple impulsive sounds. For large 

deep-penetration airgun surveys, exposure would be highest in terms of the level and number of 

impulsive sounds; conversely, for HRG surveys using smaller airguns or non-airgun sound sources, 

transect lines would be more closely spaced and shorter so that fishes might experience exposure to 

more sequences of impulsive sound. During VSP surveys where the sound source remains in a 
Gulf of Mexico G&G Activities Programmatic EIS 4-179

single location or is moved short distances, sound exposure could be high for fishes that do not 

leave the survey location but low for those that avoid the sound. In all cases, sound levels would 

return to ambient once a survey ends and the noise source is shut down. When exposure to sound 

ends, behavioral responses by fishes are expected to end also (McCauley et al., 2000a and 2000b). 

While accounting for the potential to disrupt spawning aggregations or schools of important prey 

species, the mobile and temporary nature of most surveys using active sound sources, the small 

area of the seafloor (relative to the overall AOI) affected during the surveys, and the possibility of 

fishes to temporarily move away from noise that is affecting them suggest that the impacts from 

airguns to fish resources generally and EFH would be minor under Alternative A.

No data are available for the hearing of smalltooth sawfish; however, the hearing of other 

elasmobranchs (sharks and rays) has been studied. In elasmobranchs and most likely smalltooth 

sawfish, hearing is limited to a low-frequency range (600 to 800 Hz) and relies on water particle 

motion to sense these sounds (Myrberg et al., 1976; Myrberg, 2001; Casper et al., 2003; Casper and 

Mann, 2006). Therefore, sounds from airguns are likely within the hearing range of the smalltooth 

sawfish but probably only very near the source where the particle motion component of a sound 

would be more intense. With the exception of boomer and sparker subbottom profilers, 

electromechanical sound sources generate sound much higher in frequency than do airguns 

(Table 3.3-2) that are outside the hearing range of smalltooth sawfish. The behavioral response of 

sawfish to G&G sound would be of most concern if it affects the behavior of individuals involved in 

reproduction or foraging. Sound particle motion is greatest very close to a sound source and 

attenuates rapidly with increasing range from a source (Appendix J; Normandeau Associates, Inc., 

2012). Smalltooth sawfish distribution in the AOI is limited to the waters of southwest Florida and 

Florida Bay (Figure 4.4-1). Seismic surveys are not expected within shallower waters where 

smalltooth sawfish may be present. Because of the rapid attenuation of sound particle motion with 

distance from a sound source and the expectation that higher energy sound sources will not be 

operated in the proximity of smalltooth sawfish, impacts of active acoustic sound on smalltooth 

sawfish are expected to be nominal under Alternative A.

Little is known about the hearing of Gulf sturgeon. Studies of other sturgeon species indicate 

that their hearing is most sensitive at very low frequencies (<800 Hz) (Lovell et al., 2005; Meyer 

et al., 2010). Some sturgeon species produce sounds prior to reproduction at frequencies (2 kHz) 

above their known hearing range (Johnston and Phillips, 2003). Gulf sturgeon may communicate 

using sounds produced by jumping during spawning (Sulak et al., 2002). It is likely that the 

frequency range of sound heard by Gulf sturgeon includes that of the impulsive sound generated by 

airguns and subbottom profilers (Appendix D). The severity of impacts caused by airguns (i.e., 

sound pressure and particle motion) would depend on the level of sound produced by the airgun or 

airgun array and the distance of exposed fish from the source. The most likely effects of active 

acoustic sound on Gulf sturgeon would be temporary hearing loss, masking, and behavioral 

changes. Because most individual Gulf sturgeon reside primarily within estuaries and rivers outside 

of the AOI, any effects would be limited in space and time. A small portion of the Gulf sturgeon 

population enters seasonally into the coastal ocean in western Florida (Figure 4.4-1). Seismic 

airgun surveys conducted in shallow-water areas close to critical habitat have the highest potential to 
4-180 Description of the Affected Resources and Impact Analysis

impact Gulf sturgeon. However, the extent of seismic surveys within shallower waters where Gulf 

sturgeon may be present is expected to be small relative to the overall seismic survey effort. 

Therefore, the effect of active acoustic sound sources noise on Gulf sturgeon is expected to be 

nominal under Alternative A.

Non-Airgun HRG Survey Activities

Electromechanical sources, with the exception of sparker and boomer subbottom profilers, 

are considered mid- or high-frequency sources. For these sources, the acoustic energy emitted 

outside a main operating frequency band is nominal; therefore, these are considered narrow-band 

sources (refer to Table 3.4-2 for frequency and source levels). High-frequency electromechanical 

sources can be highly directive, with transmit beam widths as narrow as a few degrees or less.

Very little information is available for the direct effects of mid- and high-frequency sound 

sources on fishes, and available studies that have been conducted are for species and in 

environments that differ from the AOI. Nevertheless, it is possible that noise from non-airgun HRG 

surveys may temporarily affect the behavior of some fish species within the AOI, particularly those 

capable of hearing in the high-frequency range (25 to 135 kHz), such as herrings, menhaden, and 

anchovies (Mann et al., 1997; Popper et al., 2004). It is thought that the ability to perceive such 

high-frequency sounds evolved as a means of sensing the presence of echolocating predators such 

as bottlenose dolphins, which are primary predators of these fish in coastal oceans (Popper et al., 

2004). Experimental tests conducted with blueback herring in the Savannah River (Georgia/South 

Carolina border) confirmed avoidance reactions to high-frequency sound (Nestler et al., 1992). 

Results determined a maximum avoidance response to sounds ranging from 124.6 to 130.9 kHz at 

187 to 200 dB re 1 μPa emitted by a single electromechanical transducer positioned 60 m (197 ft) 

from the fish. Comparative trials using lower frequency sounds resulted in limited or no reaction 

from test subjects (Nestler et al., 1992).

The direct effects of mid- to high-frequency sonar on the physiology and hearing abilities of 

fish are also not well understood. Halvorsen et al. (2012) tested the effect of mid-frequency sonar 

on the hearing of two fish species. Rainbow trout (Oncorhynchus mykiss) and channel catfish 

(Ictalurus punctatus) were exposed to sweeps of 2.8 to 3.8 kHz sonar and 3.3 kHz tones for a 

cumulative exposure of 220 dB re 1 μPa2

•s SELcum. Cumulative exposure did not cause a shift in 

the hearing threshold of rainbow trout. However, channel catfish hearing shifted by 4 to 6 dB at 

2.3 kHz, a frequency that overlaps with the upper end of the species’ hearing threshold. The catfish 

recovered from TTS within 24 hours. Other studies tested the effect of low-frequency sonar on 

hearing thresholds and found that results vary by species (Popper et al., 2007; Halvorsen et al., 

2013). Popper et al. (2007) found that rainbow trout exposed to sonar had TTSs of approximately 

20 dB at 400 Hz. Halvorsen et al. (2013) found no TTS in largemouth bass (Micropterus salmoides) 

and yellow perch (Perca flavescens). Very small threshold shifts (9 dB or less) were found in 

channel catfish, and the threshold shift returned to normal at 24 hours. In both studies, fishes were 

exposed at high intensities (193 and 195 dB re 1 μPa SPLrms), considerably higher than the fish are 
Gulf of Mexico G&G Activities Programmatic EIS 4-181

expected to be exposed to during G&G activities. Popper et al. (2007) and Kane et al. (2010) found 

no evidence of physiological damage to auditory and non-auditory body tissues from sonar.

These results confirm that high-frequency sounds emitted by active electromechanical 

acoustic operations in the AOI could affect the behavior of herrings and other high-frequency 

sensitive fish resources in a detectable way. Changes in behavior, particularly in spawning fish, 

could affect reproductive potential or feeding activity. In addition, temporary displacement of prey 

species could indirectly affect feeding activities of predatory fishes. Because the use of 

electromechanical sources for HRG surveys would be mostly from moving vessels and because 

individual surveys would be temporary and spatially limited, the impacts on these fishes and 

populations are expected to be nominal under Alternative A.

4.4.2.1.3 Vessel and Equipment Noise

Most of the G&G survey activity described in Chapter 3.3.1.1 would be conducted from 

vessels. Vessel noise is a combination of narrow band (tonal) and broadband sound (Richardson

et al., 1995). Frequency ranges and source levels for vessels and other machinery is described in 

Chapter 3.3.1.2. Drilling from fixed platforms and artificial islands produces predominantly low- to 

mid-frequency noise (700 to 1,400 Hz) at maximum source levels of 184 dB re 1μPa at 1 m 

(Blackwell et al., 2004). Noise of these levels falls within the general range of hearing in fishes 

(Amoser et al., 2004; Appendix J).

Research indicates that the direct effects of vessel and equipment noise will not cause 

mortality or barotraumatic injuries in adult fish (Hawkins et al., 2014). Vessel and equipment sound 

source levels have been shown to cause several different effects in behavior, TTS, auditory 

masking, and blood chemistry. The most common behavioral responses are avoidance, alteration of 

swimming speed and direction, and alteration of schooling behavior (Vabø et al., 2002; Handegard 

and Tjøstheim, 2005; Sarà et al., 2007; Becker et al., 2013). Laboratory and field studies have 

demonstrated several other behaviors that are influenced by vessel noise. For example, several 

studies have noted changes in time spent burrowing or using refuge, time spent defending or 

tending to nests and eggs (Picciulin et al., 2010; Bruintjes and Radford, 2013), intraspecific 

aggression and territoriality interactions (Sebastianutto et al., 2011; Bruintjes and Radford, 2013), 

foraging behavior (Purser and Radford, 2011; Bracciali et al., 2012; Voellmy et al., 2014a and 

2014b), vocalization patterns (Picciulin et al., 2008 and 2012), and overall frequency of movement 

(Buscaino et al., 2009). These studies also demonstrated that the behavioral changes generally 

were temporary or that fish habituated to the sounds. Some studies noted changes in the blood 

chemistry of several fish species (e.g., European sea bass, gilthead seabream, red drum, and 

spotted sea trout) in response to vessel noise (Buscaino et al., 2009; Spiga et al., 2012).

Auditory masking and TTS in fish exposed to vessel noise has been demonstrated in a few 

studies. Auditory thresholds have been shown to increase by as much as 40 dB when fish are 

exposed to vessel noise playbacks (Wysocki and Ladich, 2005; Vasconcelos et al., 2007; Codarin 

et al., 2009). The degree of auditory masking or TTS generally depends on the hearing sensitivity of 
4-182 Description of the Affected Resources and Impact Analysis

the fish, the frequency, and the noise levels tested (Wysocki and Ladich, 2005). The impact of 

auditory masking and TTS indicate that vessel sounds can lower the ability of fish to detect 

biologically relevant sounds. However, the effects were found to be temporary and hearing abilities 

returned to normal.

Very little is understood regarding the effect of vessel noise on the eggs and larvae of fish. 

Bruintjes and Radford (2014) demonstrated that egg hatching success and larval development of the 

cichlid Neolamprologus pulcher was not affected by exposure to vessel noise playback. Holles et al. 

(2013), however, reported that the behavior of coral reef larvae could be disrupted by the sound of 

vessel noise, indicating that the noise could decrease the ability of coral reef larvae to navigate and 

settle on suitable adult habitat. These studies indicate that developmental success and survival 

could be impacted from vessel noise but that the impacts (e.g., positive, negative, and neutral) vary 

widely.

Currently, there are G&G activities being conducted throughout the AOI. As such, vessel 

and equipment noise would continue in the AOI as a result of the proposed action scenario. 

Negative effects on fish behavior are expected to be short term and localized to areas where activity 

is concentrated. In many cases, effects (e.g., TTS) are considered temporary as fish hearing 

abilities recover. Additionally, there are few areas within the AOI that do not experience vessel noise 

of some kind, and regional fishes may have habituated to this noise (Lobel, 2009; Popper et al., 

2014). For these reasons, the impacts of vessel and equipment noise on fish resources and EFH 

are expected to be minor under Alternative A.

The G&G activities would introduce vessel and equipment noise throughout the AOI. 

Smalltooth sawfish could be adversely affected by vessel and equipment noise, but because of 

limited geographical distribution and abundance within the AOI, as well as the fact that they are 

bottom dwellers situated away from the source, exposures to such noise would be rare. The 

impacts of vessel and equipment noise on smalltooth sawfish individuals in the AOI would be 

nominal under Alternative A.

Gulf sturgeon could be adversely affected by vessel and equipment noise generated by G&G 

operations if individuals were concentrated in areas of G&G vessel activity. However, it is not likely 

that Gulf sturgeon would be subjected to vessel and equipment noise associated with the G&G 

activity scenario because of their distribution and habitat preference. The species generally occurs 

in estuaries and rivers adjacent to, and occasionally in, the coastal and shelf waters of the AOI. The 

Gulf sturgeon is a bottom dweller; individuals would be far from vessel and equipment noise 

produced by G&G vessels and, therefore, in the far field of the sound sources. Given these factors, 

impacts of vessel and equipment noise on Gulf sturgeon would be nominal under Alternative A.

4.4.2.1.4 Trash and Debris

All survey vessels performing work within U.S. jurisdictional waters are required to comply 

with Federal regulations and MARPOL 73/78. Within MARPOL Annex V, “Regulations for the 
Gulf of Mexico G&G Activities Programmatic EIS 4-183

Control of Pollution by Garbage from Ships,” as implemented by 33 CFR part 151, are requirements 

designed to protect the marine environment from various types of garbage generated on-board 

vessels. In addition, all authorizations for shipboard surveys would include guidance for marine 

debris awareness (NTL 2015-BSEE-G03).

Certain types of trash and debris produced by the proposed G&G activities (Chapter 3.3.1.7) 

could be accidentally lost overboard, with subsequent effects to smalltooth sawfish. Plastic lines, 

cables, rope, and other trash and debris generated by survey vessels could directly impact individual 

smalltooth sawfish if accidentally lost overboard. Because of their long, toothed rostrum, smalltooth 

sawfish are susceptible to entanglement in various discarded material (Seitz and Poulakis, 2006). In 

compliance with existing Federal regulations, the amount of trash and debris dumped offshore would 

be minimal as only accidental loss of trash and debris is anticipated, some of which could sink to the 

seafloor. Because of the disposal restrictions in place to reduce trash and debris and the fact that 

smalltooth sawfish are very sparsely distributed in the AOI, impacts to smalltooth sawfish from trash 

and debris would be minimized and would be nominal. Trash and debris is not expected to be a 

concern for Gulf sturgeon, other fish resources, or EFH under Alternative A. Overall, in analyzing all 

fish and EFH resources, potential impacts to would be nominal for Alternative A.

4.4.2.1.5 Seafloor Disturbance

Sources of seafloor disturbance that may result from G&G activities are bottom sampling 

(cores and grabs); placement of anchors, nodes, cables, or other bottom-founded equipment; COST 

and shallow test well drilling; and placement of anchored monitoring buoys (Table 3.2-8). The 

primary concern is the potential for direct physical damage to demersal hard bottom and hard 

bottom-associated fish resources. Similarly, EFH (coral, coral reefs, and live/hard bottom habitats) 

and federally managed species, such as spiny lobster and members of the snapper/grouper 

complex, could be directly affected by physical damage to hard bottom. Placement of equipment on 

the seafloor could damage areas where direct contact with the seafloor occurs. On soft bottom, the 

damage can mean loss of small patches of epifauna (living on the seafloor surface) and infauna 

(living in seafloor sediment); on hard bottom, contact can crush epibiota (organisms that live on the 

surface of other organisms) and damage the structure of the founding hard bottom. Damage to 

unknown or unseen hard bottom could occur, but because of the small area covered by most 

bottom-founded equipment and existing regulations (Chapter 4.5), such impacts are expected to be 

nominal. Soft bottom areas where deployments are made could lose benthic organisms (because 

of burial and crushing), and bottom-feeding fishes would be temporarily displaced from feeding 

areas.

The projected area of seafloor disturbance from G&G activities is an extremely small 

percentage of the planning areas (refer to Table 3.2-8). Given these estimates of minimal seafloor 

disturbance by projected G&G activities, the impacts to fishery resources and EFH are expected to 

be nominal under Alternative A. For the threatened and endangered fishes, seafloor disturbance 

could affect bottom-feeding species (smalltooth sawfish and Gulf sturgeon) by displacing individuals 

from feeding areas and by reducing the available benthic prey organisms. These potential impacts 
4-184 Description of the Affected Resources and Impact Analysis

to bottom feeders and their prey would be nominal under Alternative A for smalltooth sawfish and 

Gulf sturgeon because they mainly occur outside of the AOI.

4.4.2.1.6 Drilling Discharges

Discharges from COST and shallow test wells consist of drilling fluids and cuttings that would 

affect limited portions of the water column and seafloor surrounding individual wells. Drilling 

discharges can temporarily affect infaunal communities through alteration of benthic community 

structure, similar to impacts associated with seafloor disturbances that were noted previously. The 

proposed action described in Chapter 3.3.1.9 indicates the types of drilling discharges and the total 

volumes generated from exploratory drilling. The projected area of seafloor disturbance from G&G 

activities is an extremely small percentage of the planning areas (refer to Table 3.2-8). Because of 

the small areas affected by proposed G&G well drilling activities, the impacts to fish resources and 

EFH, including smalltooth sawfish and Gulf sturgeon, from drilling discharges are expected to be 

nominal under Alternative A.

4.4.2.1.7 Entanglement

Sources of entanglement hazards in the proposed action that may impact fish resources 

within the AOI include placement of anchors, nodes, cables, sensors, or other equipment on or in the 

seafloor for OBC/OBN (nodal) surveys within the oil and gas program.

Acoustic buoy releases, tethered acoustic pingers, and nodal tethering lines pose an 

entanglement risk to fish and other marine life. Entanglement is possible with OBC surveys, which 

are discussed in Appendix F, Section 1.1.3. The deployment of nodes and cables is accomplished 

by using an ROV, by dropping nodes on a tether, or by laying cables off the back of a layout boat. 

Risks of entanglement to marine life are reduced by the application of mitigations and conditions of 

approval. BOEM and cooperating agencies, using an applied adaptive management philosophy, 

have developed several standard mitigations and conditions to protect marine resources, such as 

(1) shortening acoustic buoy and tethered acoustic pinger lines to the shortest length practical and 

(2) replacing tether rope lines less than 0.25 inches in diameter with a thicker, more rigid tether line 

or modifying the line by tying knots along its length to increase the diameter and rigidity. The 

OBC/OBN (nodal) survey locations and projected levels are not estimated; however, nodal surveys 

are relatively uncommon and are typically used in shallow waters. As of 2013, there was only one 

reported manta ray entanglement incident during a tethered nodal seismic survey. Given the scope 

and transitory nature of OBC/OBN surveys associated with Alternative A and the implementation of 

risk-reducing measures described previously, entanglement impacts on fish resources and EFH are 

expected to be nominal. 

4.4.2.1.8 Routine Activities Impact Conclusions

This analysis considered the significance criteria, the AOI, and the 10-year timeframe. 

Mitigation measures that are associated with Alternative A are outlined in Chapter 2.1 and detailed 

in Appendix B. As discussed above, the degree to which these mitigation measures (collectively) 
Gulf of Mexico G&G Activities Programmatic EIS 4-185

will affect or change the levels of impact to fish resources and EFH from each project-related IPF 

(including routine activities) is presented below:

• deep-penetration airgun survey noise – nominal to minor; 

• non-airgun HRG electromechanical survey noise – nominal; 

• vessel and equipment noise – nominal to minor; 

• trash and debris – nominal; 

• seafloor disturbance – nominal; 

• drilling discharges – nominal; and

• entanglement – nominal. 

Implementation of mitigation measures described under Alternative A may reduce the 

potential impacts from the IPFs listed above to individuals within the AOI. Impact levels by IPF were 

determined using impact significance criteria discussed in Chapter 4.2.2.1, and each impact level 

was determined by considering effects to fish resources and EFH within the AOI as a whole.

4.4.2.2 Impacts of an Accidental Fuel Spill

An accidental event could result in the release of fuel or diesel by a survey vessel. Based on 

USCG spill statistics, a spill scenario was developed in Chapter 3.3.2 that assumes a diesel spill 

volume of 1.2 to 7.1 bbl. Diesel is acutely toxic to algae, invertebrates, and fishes, and any contact 

with a diesel spill can result in death. However, small spills in open water, such as the one 

described in Chapter 3.3.2, rapidly disperse and volatile components evaporate, making fish kills 

rare events. For the duration of such a spill, species and life stages residing in the upper water 

column are most at risk for contact with the spilled fuel. Coastal pelagic and epipelagic adults 

(Chapter 4.4.1 and Appendix E, Section 4) that forage at the ocean surface would be most likely to 

encounter a surface spill. Species known to feed at the ocean surface, including Spanish mackerel, 

king mackerel, little tunny, and yellowfin tuna, are at the greatest risk of exposure but would likely 

swim away from a small diesel spill. Planktonic early life stages (i.e., eggs of demersal and pelagic 

species) would be unable to avoid a spill and, therefore, are most vulnerable to toxic properties of 

diesel (Mos et al., 2008).

Numerous federally managed species described previously (refer to Chapter 4.4.1 and 

Appendix E, Section 4) have pelagic eggs and larvae that would be at risk if they encountered a 

diesel spill. The EFH most at risk from a small diesel spill would be pelagic Sargassum habitat. 

Drifting in windrows or mats, Sargassum supports two fish species permanently (Sargassumfish and 

Sargassum pipefish) and several fish species as juveniles (e.g., jacks, triggerfishes, and filefishes). 

Additionally, larger species of recreational or commercial importance feed on the small fishes and 

invertebrates attracted to Sargassum habitat (Dooley, 1972; Bortone et al., 1977; Wells and Rooker, 

2004a and 2004b) (Chapter 4.8). Exposure of spilled diesel fuel on early life stages of fish and on 
4-186 Description of the Affected Resources and Impact Analysis

Sargassum habitat is expected to last for less than a day and have limited spatial extent. 

Furthermore, if an accidental fuel spill occurs, it is anticipated that the spill size would be relatively 

small and the area of impact would be a small portion of the AOI; the type and severity of impacts to 

pelagic fish, as well as buoyant eggs and larvae in localized areas, would depend on the location of 

the event but are expected to range from nominal to minor under Alternative A.

Because of their life histories, neither smalltooth sawfish nor Gulf sturgeon would have 

sensitive eggs or larvae in the water column of the AOI where they would be exposed to accidentally 

spilled diesel fuel. Therefore, the expected impact of an accidental diesel fuel spill is expected to be 

nominal for both species under Alternative A.

4.4.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for fish resources and EFH are compared with the 

IPFs from each of the cumulative scenario activities in order to focus this cumulative analysis on 

those activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The 

G&G activity IPFs that are included in the cumulative assessment are the same as those assessed 

under routine activities and accidental events. The following analysis evaluates the incremental 

increase by IPF and provides a conclusion of the cumulative incremental increase within the AOI.

The G&G activities have been ongoing in the GOM for at least the past 30 years and it is 

reasonable to assume they will continue into the future; however, for the purpose of this 

Programmatic EIS, the cumulative analysis assesses a 10-year timeframe to coincide with the 

proposed action because it is not expected that G&G activities will have lasting effects or extend 

beyond the 10-year timeframe of this Programmatic EIS.

4.4.2.3.1 Noise

Active Acoustic Sound Sources

The impacts from active acoustic sound sources from the proposed action are discussed in 

Chapter 4.4.2.1. Overall, Chapter 4.4.2.1 determined that there would be increases in ambient 

noise levels within specific portions of the AOI during G&G operations, but with nominal to minor

impacts to smalltooth sawfish, Gulf sturgeon, and all other fish resources and EFH.

All G&G survey activities associated with the OCS Program are included in the proposed 

action; therefore, G&G activities on the OCS are not included in the cumulative analysis but instead 

are addressed in the proposed action impact analysis. Certain OCS Program-related activities such 

as drilling noise, trenching noise, pile-driving, and decommissioning are discussed below under 

“Vessel and Equipment Noise” because they are not active acoustic sounds, but rather related to 

equipment. Active acoustic sound sources related to oil and gas development have been ongoing in 
Gulf of Mexico G&G Activities Programmatic EIS 4-187

the GOM for decades and are likely to be used in the future. As discussed in Chapter 4.4.2.1, such 

sounds may impact fish resources and EFH, but only temporarily and in localized areas around the 

sound sources.

The G&G activities associated with the proposed action will not be conducted within State 

waters. However, other agencies can permit G&G activities that can include active sound sources 

(e.g., seismic airguns and side-scan sonars for oil and gas activities in State waters). Although G&G 

activities associated with the proposed action will not be conducted in State waters, sound produced 

by G&G activities within Federal waters may propagate into State waters. The source of such 

sounds generally will be distant from State waters and greatly reduced in intensity by the time they 

reach State waters. Behavioral responses or masking are possible impacts to fish or invertebrates if 

the sound source is loud enough and in the hearing range of the organism, or the organisms may 

exhibit no response (Chapter 4.4.2.1).

Other major factors that contribute active acoustic sound sources are shown in Table 3.4-1. 

Impacts from similar sound sources under the G&G proposed action (e.g., seismic airguns) are 

discussed in Chapter 4.4.2.1. Studies have shown that military sonars do not cause mortality or 

physiological damage to auditory and non-auditory tissues (Popper et al., 2007; Kane et al., 2010), 

and they are not likely to lead to population consequences for Atlantic herring (Sivle et al., 2015). 

Active acoustic sound sources from G&G activities considered in cumulative impacts assessment 

have been ongoing in the AOI for multiple decades and are likely to continue in the future. 

Anthropogenic sounds levels in the marine environment are increasing, and impacts like masking 

and behavioral changes to fish and invertebrates is likely (Slabbekoorn et al., 2010; Radford et al., 

2014). Yet, it is difficult to assess overall increases in sound because of the lack of baseline data 

from individual sound sources and the ambient sound conditions (Hawkins et al., 2014). Therefore, 

it is expected that there would be a nominal to minor incremental increase in impacts to fish 

resources and EFH from active acoustic sound sources under the proposed alternative.

Vessel and Equipment Noise

The impacts from vessel and equipment noise from the proposed action are discussed in 

Chapter 4.4.2.1. Overall, Chapter 4.4.2.1 determined that there would be nominal to minor

impacts to smalltooth sawfish, Gulf sturgeon, and all other fish resources and EFH.

Support vessel traffic, drilling, and other development activities are key parts of most OCS 

Program activities; as such, vessel and equipment noise is generated (Chapter 3.4). Very little 

drilling will occur as part of the proposed activities and will therefore add little to the cumulative 

impacts (Table 3.2-8). Vessel and equipment noise in the AOI may negatively affect the behavior of 

fish resources (Chapter 4.4.2.1). Vessels and equipment associated with G&G and OCS Program 

activities have been conducted in the AOI for decades and will likely continue in the future. Offshore 

facility decommissioning, including platform and caisson removal, typically use one of two primary 

methods to sever structures attached to the seafloor: mechanical severance or explosive 

severance. Explosive charges generally are placed inside the platform legs or conductors 4.6 to 
4-188 Description of the Affected Resources and Impact Analysis

7.6 m (15 to 25 ft) below the seafloor. Historical structure-removal permit applications and numbers 

of structures removed in the GOM between 2002 and 2013 are summarized in Tables 3.4 3 and

3.4-4. The underwater detonation of explosives results in a shockwave and acoustic energy that can 

kill or harm fish. Gitschlag et al. (2000) found that the most severely impacted fish species at 

explosive structure removals (in order of abundance) were Atlantic spadefish (Chaetodipterus faber), 

blue runner, red snapper, and sheepshead (Archosargus probatocephalus). Govoni et al. (2008) 

indicated that explosives can cause mortality to fish larvae, but that is unlikely to affect fishes at the 

population level. Proposed activities would increase levels of vessel noise and decommission within 

the AOI, resulting in increases in ambient noise levels within discrete geographical areas during 

G&G operations (primarily the WPA and CPA).

Vessels and equipment needed to support proposed G&G activities may travel through State 

waters, but this will be temporary and would be similar to existing traffic in the region. Behavioral 

responses or masking are possible impacts to fish and invertebrates if the sound source is loud 

enough and in the hearing range of the organism, or the organisms may exhibit no response 

(Chapter 4.4.2.1). Therefore, sounds from vessels and equipment generated in the AOI will be 

greatly reduced if they propagate into State waters. Such sounds will be temporary and will not 

cause significant increases in sound levels impacts to fish and EFH.

Other major factors that contribute vessel and equipment noise are shown in Table 3.4-1. 

The majority of these noise-producing activities results in continuous sound (e.g., vessel and 

dredging noise) that may result in impacts, such as behavioral responses and masking in fish and 

invertebrates (Chapter 4.4.2.1). Pile-driving sounds are impulsive and are likely to have similar 

impacts to seismic airguns. Mortality or physiological damage may be possible within a very small 

range of the sound source, but behavioral responses and impacts to hearing are more likely 

throughout the AOI. Vessel and equipment noise from G&G activities considered in cumulative 

impacts assessment have been ongoing in the AOI for multiple decades and are likely to continue in 

the future. Anthropogenic sounds levels in the marine environment are increasing, and impacts like 

masking and behavioral changes in fishes is likely (Slabbekoorn et al., 2010; Radford et al., 2014). 

Yet, it is difficult to assess overall increases in sound because of the lack of baseline data from 

individual sound sources and the ambient sound conditions (Hawkins et al., 2014).

Overall, compared with the combined vessel noise within the GOM, it is expected that there 

would be a nominal incremental increase in impacts to fish resources and EFH from vessel and 

equipment noise under the proposed alternative.

4.4.2.3.2 Trash and Debris

Certain types of trash and debris could be accidentally lost overboard, some of which could 

sink to the seafloor and potentially cause entanglement of smalltooth sawfish (Chapter 4.4.2.1). 

However, there are no reports of smalltooth sawfish or other fish resources being entangled from the 

OCS Program or oil and gas activities in State waters. In compliance with existing Federal 

regulations, the amount of trash and debris dumped offshore would be minimal, as only accidental 
Gulf of Mexico G&G Activities Programmatic EIS 4-189

loss of trash and debris is anticipated. All authorizations for shipboard surveys would include 

guidance for marine debris awareness (NTL 2015-BSEE-G03). Because of the disposal restrictions 

in place to reduce trash and debris, guidance for marine debris awareness, and the fact that 

smalltooth sawfish are very sparsely distributed in the AOI and are limited to State waters in the 

EPA, impacts to smalltooth sawfish from entanglement in trash would be minimized and nominal. 

Considering the small contribution of trash and debris from activities under the proposed action, a 

nominal incremental increase in impacts from trash and debris is expected.

4.4.2.3.3 Seafloor Disturbances

The impacts from seafloor disturbances from the proposed action are discussed in 

Chapter 4.4.2.1. Overall, Chapter 4.4.2.1 determined that there would be nominal impacts to 

smalltooth sawfish, Gulf sturgeon, and all other fish resources and EFH.

Seafloor-disturbing activities associated with the proposed action over the 10-year period are 

included in Table 3.2-8. The cumulative scenario includes activities that disturb the seafloor by 

anchoring, trenching, coring, trawling and bottom sampling from OCS Program activities, 

decommissioning, and the renewable and marine minerals programs. In addition, other activities in 

the AOI, such as State waters oil and gas, commercial fishing, dredging and material disposal 

activities, cable installation, military activities, and scientific research, can cause seafloor 

disturbances (Table 3.4-1). Bottom-disturbing activities may affect fish resources and EFH 

temporarily by disrupting feeding by soft bottom species or elevating turbidity that would impair 

feeding by visually oriented plankton feeders. The projected area of seafloor disturbance is a very 

small fraction of the AOI and represents a limited area when compared with projected bottom 

disturbance from oil and gas program activities during the 10-year period (Table 3.4-2). Because of 

the likely wide separation, the risk of cumulative impacts associated with the proposed action with 

similar cumulative activities will be nominal. While small numbers of bottom samples may be 

clustered in an area, the seafloor disturbed by each sample is small and the areas investigated using 

bottom samples likely will be widely spaced. In addition, the time required for each bottom sample is 

very short. The potential impacts of seafloor disturbance to benthic resources, which includes 

corals, spiny lobster, and shrimp, are considered in Chapter 4.5. 

The number of seafloor disturbances expected under the proposed action do not occur 

homogenously over the entire AOI nor homogenously over the 10-year period; thus, they are 

spatially and temporally limited and their impacts are not likely to increase over time. Considering 

the small contribution of seafloor disturbance from activities under the proposed action, a nominal

incremental increase in impacts is expected.

4.4.2.3.4 Drilling Discharges

The impacts from drilling discharges from the proposed action are discussed in 

Chapter 4.4.2.1. Overall, Chapter 4.4.2.1 determined that there would be nominal impacts to 

smalltooth sawfish, Gulf sturgeon, and all other fish resources and EFH.
4-190 Description of the Affected Resources and Impact Analysis

Oil and gas program activities over the next 10 years are projected to include drilling that will 

result in discharges from several activities (refer to Table 3.4-2). Drilling discharges can temporarily 

increase turbidity, bury soft bottom communities, and exclude bottom-feeding fishes from small 

areas of the seafloor (Chapter 4.4.2.1). Seafloor-disturbing activities and the projected area of 

seafloor disturbance associated with G&G activities under the proposed action can be found in 

Table 3.2-8. Assuming the wells to be drilled under the proposed action will be similar to wells to be 

drilled under the OCS Program, the incremental increase in drilling discharges from well drilling 

under the proposed action will be very small, impacting a small portion of the seafloor. It is unlikely 

that wells drilled under the OCS Program and those drilled under the proposed alternative would be 

close enough in time or space that drilling discharges from one well might contribute to the possible 

impacts from another.

The G&G activities under the proposed action will not occur within State waters, which are 

outside of BOEM’s jurisdiction. Oil and gas activities in State waters will contribute drilling 

discharges and also impacts to fish and EFH. It is extremely unlikely that IPFs from the proposed 

action will enter State waters and result in additional incremental impacts to similar activities.

Therefore, the cumulative impact under the proposed action is limited to a small increase in 

the seafloor area impacted by drilling discharge and would be separated from drilling discharges in 

the cumulative scenario in space and time. Drilling discharges will not occur homogenously over the 

entire AOI nor homogenously over the 10-year period; thus, they are spatially and temporally limited 

and their impacts are not likely to increase over time. Therefore, it is expected that there would be a 

nominal incremental increase in impacts to fish resources and EFH from drilling discharges under 

the proposed alternative. The potential impacts of drilling discharges to benthic resources, which 

includes corals, spiny lobster, and shrimp, are considered in Chapter 4.5. 

4.4.2.3.5 Entanglement

Chapter 4.4.2.1 determined that there would be nominal impacts to smalltooth sawfish, Gulf 

sturgeon, and all other fish resources and EFH from the proposed action under Alternative A. The 

EFH for corals, spiny lobster, and shrimp are considered in the analysis of benthic resources in 

Chapter 4.5. 

Other major factors that contribute to entanglement are shown in Table 3.4-1. Such 

activities have the potential to cause entanglement from trash, debris, fishing gear, or sampling gear. 

Entanglement risk of sawfish is highest for active or discarded commercial and recreational fishing 

gear, and the risk of entanglement by other potential entanglement debris is very low (Seitz and 

Poulikis, 2006). The OBC/OBN (nodal) surveys locations and projected levels are not estimated; 

however, nodal surveys are relatively uncommon and are typically used in shallow waters. Given 

the scope and transitory nature of OBC/OBN surveys associated with Alternative A and the 

implementation of risk-reducing measures described previously, entanglement impacts on fish 

resources and EFH are expected to result in a nominal incremental increase in impacts under the 

cumulative scenario.
Gulf of Mexico G&G Activities Programmatic EIS 4-191

4.4.2.3.6 Cumulative Impact Conclusions

The spatial distribution of activities projected under the proposed action during the project 

period are most concentrated within deepwater regions of the CPA and WPA, and less concentrated 

within continental shelf waters (Table 3.2-1). Very little activity is projected to occur within the EPA. 

Temporally, activity levels associated with the proposed action vary by activity type and year (Tables 

3.2-1 through 3.2-5). Fish resources are likely habituated (familiar with) to sound levels within the 

AOI, and impacts from sound are likely to be minimal, temporary, and localized. Seismic surveys 

and activities that generate vessel and equipment noise are not conducted homogenously over the 

entire AOI nor homogenously over the 10-year period; thus, they are spatially and temporally limited 

and their impacts are not likely to increase over time.

When compared with historic levels of activities within the GOM, proposed activities do not 

represent a significant incremental increase to activities under the cumulative scenario. Surveys 

utilizing active acoustic sound sources have occurred within the GOM for decades, including within 

State waters and the continental shelf and deepwater regions of the OCS. Commercial, military, and 

recreational vessel traffic has also occurred in the GOM, including the AOI for many years. In some 

cases, such as large commercial vessels, traffic is and has been more concentrated along shipping 

lanes that funnel into major coastal ports. Commercial and recreational fishing vessels have utilized 

broad areas of the northern GOM, but primarily on the continental shelf and shelf edge. It is 

assumed that military vessels have traveled through all areas of the GOM, though it is assumed that 

most, if not all, exercises have occurred within the U.S. Navy GOMEX Range Complex OPAREAs.

When compared with historic, present, and future activities, including similar non-OCS 

Program activities (Figure 3.4-1), the cumulative effects of all IPFs to fish resources and EFH within 

the AOI over the 10-year period would result in nominal to minor incremental increases in impacts.

4.4.2.3.7 Accidental Fuel Spills

The impacts from accidental fuel spills from the proposed action are discussed in 

Chapter 4.4.2.2. Overall, Chapter 4.4.2.2 determined that if an accidental fuel spill occurs, impacts 

would range from nominal to minor. 

As discussed in Chapter 3.4, the AOI includes an extensive system of offshore oil and gas 

production facilities. The potential for fuel spills from vessels involved in the OCS Program would be 

higher than that expected under the proposed action because of the magnitude of vessel activity in 

the AOI and the high number of vessel transits. However, the potential for collision and product 

transfer fuel spills from vessels involved in the cumulative activities scenario is considered remote 

because of the small number of vessels, the type of vessels and required fuels, the standards and 

protocols for management of vessel fuels, and the aids to navigation and crew training for vessels 

likely to be used under the proposed alternative. With the use of AIS on large sea-going vessels, 

radar, and licensing of vessel captains, the potential of a vessel collision occurring is low, and the 

potential for a resultant spill is even lower. Fuel and diesel used for the operation of support vessels 

is light and would float on the sea surface where is it subjected to weathering, dispersion, and 
4-192 Description of the Affected Resources and Impact Analysis

dissolution. Heavier fuels may be used in larger commercial vessels involved in marine 

transportation. Thus, the increase in potential for accidental fuel spills arising from vessel collision 

during G&G activities would be considered extremely small.

The G&G activities associated with the proposed action will not be conducted within State 

waters; however, vessels involved with G&G activities may transit through State waters. Because 

the majority of the activities associated with proposed action will not occur in State waters, there is a 

low probability of a G&G activity-related fuel spill from oil and gas activities in State waters or that 

fuel spilled in Federal waters would be transported into State waters. Thus, the potential for spills 

from vessels involved in the cumulative activities scenario is remote, and it is anticipated that, if a 

spill occurred, the spill size would be relatively small, the type of fuel that would likely be spilled 

would rapidly dissipate, and the area impacted would be a small.

Accidental fuel spills are possible from vessels associated with other cumulative activities 

(Table 3.4 1). As discussed, the potential for collision and product transfer fuel spills from vessels 

involved in the cumulative activities scenario is considered remote. Fuel and diesel used for the 

operation of support vessels is light and would float on the sea surface where is it subjected to 

weathering, dispersion, and dissolution. Heavier fuels may be used in larger commercial vessels 

involved in marine transportation. The potential for fuel spills from vessels involved in the activities 

assessed under the cumulative scenario would be higher than that expected under the proposed 

action because of the magnitude of vessel activity in the AOI and the high number of vessel transits. 

Thus, the increase in potential for accidental fuel spills arising from vessel collision during G&G 

activities would be considered extremely small.

Activities associated with all cumulative scenario activities have the potential to cause an 

accidental fuel spill (Table 3.4-1). If accidental fuel spills from the cumulative scenario activities 

coincided spatially and temporally with an accidental fuel spill from G&G vessels, then cumulative 

impacts to fish and EFH could be exacerbated. Impacts from G&G vessels are most likely to be 

cumulative with OCS Program activities because of the higher number of vessels and greater spatial 

overlap between activities. Fuel and diesel used for the operation of support vessels is light and 

would float on the sea surface where is it subjected to weathering, dispersion, and dissolution. 

There are also several mitigation measures in place to avoid vessel collisions. Therefore, impacts 

from accidental fuel spills from G&G activities will be spatially and temporally limited and would 

result in a nominal incremental increase in impacts to fish resources and EFH under the cumulative 

scenario.

4.4.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.4.2.1). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative B on fish resources and EFH.
Gulf of Mexico G&G Activities Programmatic EIS 4-193

4.4.3.1 Impacts of Routine Activities

Additional mitigation measures under Alternative B, including the expansion of NTL 2012-

JOINT-G02 (inclusion of manatees and application to all deep-penetration seismic airgun surveys in 

all water depths) and the expanded use of PAM, are not relevant to fish resources and EFH and, 

therefore, would not change the level of impact to fish resources and EFH. As such, those mitigation 

measures will not be addressed in the following discussion.

4.4.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to April 30)

Seasonal restrictions for airgun operations in coastal waters under Alternative B would 

change when active acoustic sound sources and vessel equipment and noise could occur in Federal 

coastal waters of the GOM compared with Alternative A. Seismic airgun usage associated with the 

surveys would not be authorized in Federal coastal waters of the GOM shoreward of the 20-m (66-ft) 

isobath between January 1 and April 30 (Figure 2.2-1). The impacts of active acoustic sound 

sources and vessel and equipment noise from seismic airgun surveys would be reduced, but only 

within coastal waters between January 1 and April 30. The purpose of this mitigation measure is to 

provide protection to marine mammals within these seasonally restricted areas from the IPFs 

associated with deep-penetration seismic airgun surveys. This mitigation measure would provide an 

ancillary benefit to some coastal fish species (Tables 4.4-1, 4.4-2, and 4.4-4), as the effects on fish 

hearing and behavior (discussed in detail in Chapter 4.4.2.1) will be reduced in the seasonally 

restricted areas. However, seismic surveys will still occur outside this area, the closure timeframe is 

temporary, and the closure area is small compared with the AOI. Therefore, the overall impacts 

from the IPFs in Alternative B will not change. The impacts of active acoustic sound sources from 

seismic airguns are expected to be nominal for smalltooth sawfish and Gulf sturgeon, and minor for 

fish resources and EFH under Alternative B. The mitigation measure does not apply to sound 

sources from non-airgun HRG surveys; therefore, the impact from electromechanical sources will 

remain nominal for fish resources and EFH under Alternative B. Impacts of vessel equipment and 

noise are expected to be nominal for smalltooth sawfish and Gulf sturgeon, and minor for fish 

resources and EFH under Alternative B. This mitigation does not apply to the other project-related 

IPFs and would not alter the impacts to fish resources and EFH from trash and debris, seafloor 

disturbance, drilling discharges, or entanglement; impacts would remain nominal. 

4.4.3.1.2 Minimum Separation Distances

Alternative B would establish a 40-km (25-mi) separation distance between simultaneously 

operating deep-penetration seismic airgun surveys within the Areas of Concern and a 30-km (19-mi) 

separation distance outside the Areas of Concern (Chapter 2.2.2).

Applicable routine IPFs for fish resources and EFH are active acoustic sound sources and 

vessel equipment and noise. Limits on concurrent seismic airgun surveys under Alternative B could 

change the timing of seismic surveys in certain areas. The locations cannot be predicted in 

advance, but this would depend on the schedule, planned coverage of individual surveys, and ports 

to be used for support activities. Seismic surveys will still be conducted; therefore, a change in the 
4-194 Description of the Affected Resources and Impact Analysis

survey timing because of limits on concurrent seismic airgun surveys would not alter the impacts 

from active acoustic sound sources and vessel and equipment noise on fish and EFH. Therefore, 

under Alternative B, impacts of active acoustic sound sources are expected to be nominal for 

smalltooth sawfish and Gulf sturgeon, minor for fish resources and EFH affected by airguns, and 

nominal for fish resources and EFH affected by electromechanical sounds. Impacts of vessel and 

equipment noise are expected to remain minor for fish resources and EFH, and nominal for 

smalltooth sawfish and Gulf sturgeon under Alternative B. This mitigation does not apply to the 

other project-related IPFs and would not alter the impacts to fish resources and EFH from trash and 

debris, seafloor disturbance, drilling discharges, or entanglement; impacts would remain nominal. 

4.4.3.1.3 Seismic Restrictions in the Areas of Concern within the EPA

Additional restrictions under Alternative B include the prohibition of deep-penetration seismic 

airgun surveys within the portion of the Areas of Concern (Chapter 2.2.2) falling within the EPA. 

This restriction does not apply to surveys related to currently leased blocks, any portion of the area 

encompassed by EPA Lease Sale 226, or neighboring OCS lease blocks adjacent to permitted 

survey areas but within an otherwise off limit area.

A restriction on seismic surveys within a portion of the AOI could result in reduced impacts 

from active acoustic sound sources and vessel equipment and noise due to the reduced area of 

activity. The purpose of this mitigation measure is to provide protection to marine mammals within 

these seasonally restricted areas from the IPFs associated with deep-penetration seismic airgun 

surveys. This mitigation measure would provide an ancillary benefit to some oceanic fish species 

(Appendix E) in the seasonally restricted area, as the effects on fish hearing and behavior 

(discussed in detail in Chapter 4.4.2.1) will be reduced in that region. The impacts of active acoustic 

sound sources and vessel and equipment noise from seismic airgun surveys would be reduced, but 

only in the portion of the Areas of Concern falling within the EPA. The size of the closure area is 

small compared with the size of the AOI, and the majority of deep-penetration seismic airgun 

surveys will occur in the WPA and CPA where seismic surveys will not be restricted. Thus, there will 

not be a substantial reduction in seismic survey activity in the AOI and the overall impacts on fish 

resources and EFH would not change under Alternative B. Therefore, impacts of airgun active 

acoustic sound sources are expected to be nominal for smalltooth sawfish and Gulf sturgeon, and 

minor for fish resources and EFH. This mitigation measure does not apply to sound sources from 

non-airgun HRG surveys; therefore, the impact from electromechanical sources will be nominal for 

fish resources and EFH under Alternative B. Impacts of vessel equipment and noise are expected to 

be nominal for smalltooth sawfish and Gulf sturgeon, and minor for fish resources and EFH under 

Alternative B. This mitigation does not apply to the other project-related IPFs and would not alter the 

impacts to fish resources and EFH from trash and debris, seafloor disturbance, drilling discharges, 

or entanglement; impacts would remain nominal. 

4.4.3.1.4 Routine Activities Impact Conclusions

This analysis considered the significance criteria, the AOI, and the 10-year timeframe. 

Mitigation measures that are associated with Alternative B are outlined in Chapter 2.2 and detailed 
Gulf of Mexico G&G Activities Programmatic EIS 4-195

in Appendix B. As discussed above, the degree to which these mitigation measures (collectively) 

will affect or change the levels of impact to fish resources and EFH from each project-related IPF 

(including routine activities) is presented below:

• deep-penetration airgun survey noise – nominal to minor; 

• non-airgun HRG electromechanical survey noise – nominal; 

• vessel and equipment noise – nominal to minor; 

• trash and debris – nominal; 

• seafloor disturbance – nominal; 

• drilling discharges – nominal; and

• entanglement – nominal. 

Implementation of mitigation measures described under Alternative A may reduce potential 

impacts from the IPFs listed above to individuals within the AOI. Impact levels by IPF were 

determined using impact significance criteria discussed in Chapter 4.4.2.1, and each impact level 

was determined by considering effects to fish resources and EFH within the AOI as a whole.

4.4.3.2 Impacts of an Accidental Fuel Spill

Under Alternative B, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. Alternative B would change the timing of certain surveys because of additional coastal 

seasonal restrictions. However, spills from seismic survey vessels could occur in the closure areas 

during times outside the closure period, and spills from other survey vessels could occur during the 

closure period. A change in survey timing would not substantially change the risk of a small fuel 

spill. Therefore, the impacts of the IPFs would be very similar to those analyzed for Alternative A in 

Chapter 4.4.2.2. If an accidental fuel spill occurs, it is anticipated that the spill size would be 

relatively small and that the area of impact would be a small portion of the AOI; the type and severity 

of impacts to pelagic fish as well as buoyant eggs and larvae in localized areas would depend on the 

location of the event but the impacts are expected to range from nominal to minor. 

4.4.3.3 Cumulative Impacts

Impact analyses presented in Chapters 4.4.3.1 and 4.4.3.2 determined that activities 

projected to occur under Alternative B would result in nominal to minor impacts to fish resources 

and EFH, depending on the IPF.

Mitigation measures for the proposed action under Alternative B are described in 

Chapter 2.2 and summarized in Chapter 4.4.3.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.4.2.3). Most of the mitigation measures 

under Alternative B would not change the extent, severity, or timing of activities in the proposed 

action, and therefore would not change the resultant impacts to fish resources and EFH. Mitigation 
4-196 Description of the Affected Resources and Impact Analysis

measures under Alternative B that would change the timing and extent of activities in the proposed 

action include a seasonal restriction for operation of airguns in Federal coastal waters, a minimum 

separation distance requirement for simultaneous seismic operations, and the prohibiting of deeppenetration seismic airgun surveys within portions of the EPA (Chapter 2.2.2).

The proposed action activities considered in assessment of cumulative impacts are the same 

for Alternatives A and B. Seasonal restriction of airgun operation in Federal coastal water under 

Alternative B may cause a shift in schedules for seismic surveys using airguns but not necessarily a 

reduction in the number and extent of surveys conducted in Federal coastal waters. Prohibition of 

deep-penetration seismic airgun surveys using airguns in the EPA also will not appreciably impact 

the number and extent of such surveys under Alternative B because almost all seismic exploration 

activity to be conducted during the analysis period will be conducted in the WPA and CPA, (Table 

3.2-1). Because there is little to no change in proposed action activities considered between 

Alternatives A and B and the limited effect of Alternative B mitigation measures on the occurrence 

and extent of IPFs, EFH and fish resources would not be impacted by additional measures in 

Alternative B beyond that described for Alternative A. Therefore, for Alternative B, there would be a 

nominal to minor incremental cumulative increase in impacts to fish resources and EFH.

4.4.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.4.2.1). The following discussion outlines the effects of the additional 

mitigation measures included under Alternative C on fish resources and EFH.

4.4.4.1 Impacts of Routine Activities

Additional mitigation measures under Alternative C that would not change the extent, 

severity, or timing of G&G activities and, therefore related impacts to fish resources and EFH, 

include the expanded use of PAM for seismic airgun surveys, the expanded use of PSOs for seismic 

airgun surveys and HRG surveys, expansion of NTL 2012-JOINT-G02 (inclusion of manatees) for 

seismic airgun surveys, expansion of NTL 2012-JOINT-G02 to include HRG surveys using airguns, 

and a pre-survey clearance period for HRG surveys. As such, those mitigation measures will not be 

addressed in the discussion provided in the following chapters. 

4.4.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to May 31)

Alternative C would require seasonal restrictions for seismic airgun survey operations in 

coastal waters of the GOM shoreward of the 20-m (66-ft) isobath between February 1 and May 31 

(Figure 2.3-1). The impacts of active acoustic sound sources and vessel and equipment noise from 

seismic airgun surveys would be reduced, but only within coastal waters between February 1 and 

May 31. The purpose of this mitigation measure is to provide protection to marine mammals within 

these closure areas from the IPFs associated with deep-penetration seismic airgun surveys. This 

mitigation measure would provide an ancillary benefit to some coastal fish species (Tables 4.4-1, 
Gulf of Mexico G&G Activities Programmatic EIS 4-197

4.4-2, and 4.4-4) as the effects on fish hearing and behavior (discussed in detail in Chapter 4.4.2.1) 

will be reduced due to the seasonal restriction. However, seismic surveys will still occur outside this 

area, the closure duration is seasonal, and the closure area is small compared with the size of the 

AOI. Therefore, the overall impacts from the IPFs under Alternative C would not change 

substantially for most fish.

4.4.4.1.2 Routine Activities Impact Conclusions

The impacts of active acoustic sound sources from airguns are expected to be nominal for 

smalltooth sawfish and Gulf sturgeon, and minor for fish resources and EFH under Alternative C. 

The mitigation measure does not apply to sound sources from non-airgun HRG surveys; therefore, 

the impact from electromechanical sources will be nominal for fish resources and EFH under 

Alternative C. Impacts of vessel equipment and noise are expected to be nominal for smalltooth 

sawfish and Gulf sturgeon, and minor for fish resources and EFH. This mitigation does not apply to 

the other project-related IPFs and would not alter the impacts to fish resources and EFH from trash 

and debris, seafloor disturbance, drilling discharges, or entanglement; impacts would remain 

nominal. 

4.4.4.2 Impacts of an Accidental Fuel Spill

Under Alternative C, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. Similar to Alternative B, a change in survey timing would not substantially change the risk 

of a small fuel spill because spills from seismic survey vessels could occur in the closure areas 

during times outside the closure period and because spills from other survey vessels could occur 

during the closure period. Therefore, the impacts of the IPFs would be very similar to those 

analyzed for Alternative A in Chapter 4.4.2.2. If an accidental fuel spill occurs, it is anticipated that 

the spill size would be relatively small and the area of impact would be a small portion of the AOI; 

the type and severity of impacts to pelagic fish, as well as buoyant eggs and larvae in localized 

areas, would depend on the location of the event but are expected to range from nominal to minor

under Alternative C.

4.4.4.3 Cumulative Impacts

Impact analyses presented in Chapters 4.4.4.1 and 4.4.4.2 determined that activities 

projected to occur under Alternative C would result in nominal to minor impacts to fish resources 

and EFH, depending on the IPF. Mitigation measures for the proposed action under Alternative C 

are described in Chapter 2.3. A detailed impacts assessment under the cumulative scenario is 

provided in Alternative A (Chapter 4.4.2.3). Most of the mitigation measures under Alternative C, 

including seasonal restrictions, would not change the extent, severity, or timing of activities in the 

proposed action and, therefore, would not change the resultant impacts to fish resources and EFH.

Alternative C does not change the cumulative outcomes described in Alternative A; there 

would be a nominal to minor incremental increase in impacts to fish resources and EFH under 

Alternative C.
4-198 Description of the Affected Resources and Impact Analysis

4.4.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative D are the same as for 

Alternative A (Chapter 4.4.2.1). The additional mitigation measure under Alternative D, which 

includes shutdowns for marine mammals, would not change the extent, severity, or timing of IPFs 

outlined in Alternatives A and C.

4.4.5.1 Impacts of Routine Activities

The additional mitigation measure under Alternative D would not reduce potential active 

acoustic impacts discussed under Alternatives A and C (Chapters 4.4.2.1 and 4.4.4.1). The 

impacts of active acoustic sound sources from airguns are expected to be nominal for smalltooth 

sawfish and Gulf sturgeon, and minor for fish resources and EFH under Alternative D. The 

mitigation measure does not apply to sound sources from non-airgun HRG surveys; therefore, the 

impact from electromechanical sources will be nominal for fish resources and EFH under 

Alternative D. Impacts of vessel equipment and noise are expected to be nominal for smalltooth 

sawfish and Gulf sturgeon, and minor for fish resources and EFH. This mitigation does not apply to 

the other project-related IPFs and would not alter the impacts to fish resources and EFH from trash 

and debris, seafloor disturbance, drilling discharges, or entanglement; impacts would remain 

nominal. 

4.4.5.2 Impacts of an Accidental Fuel Spill

Alternative D would not add additional mitigation measures that would reduce risk of an 

accidental fuel spill. Therefore, the impacts of the IPFs would be very similar to those analyzed for 

Alternatives A and C in Chapter 4.4.2.2. If an accidental fuel spill occurs, it is anticipated that the 

spill size would be relatively small and the area of impact would be a small portion of the AOI; the 

type and severity of impacts to pelagic fish as well as buoyant eggs and larvae in localized areas 

would depend on the location of the event but are expected to range from nominal to minor. 

4.4.5.3 Cumulative Impacts 

Impact analyses presented in Chapters 4.4.5.1 and 4.4.5.2 determined that activities 

projected to occur under Alternative D would result in nominal to minor impacts to fish resources 

and EFH, depending on the IPF. Mitigation measures for the proposed action under Alternative D 

are described in Chapter 2.4 and summarized in Chapter 4.4.5.1. A detailed impacts assessment 

under the cumulative scenario is provided in Alternative A (Chapter 4.4.2.3). The mitigation 

measures are the same as described for Alternative C with the addition of shutdown protocols during 

seismic operations for all marine mammals (except bow-riding dolphins). The shutdown protocols 

would not change the extent, severity, or timing of activities in the proposed action; thus, the 

resultant impacts to fish resources and EFH also would not change. Because proposed action 

activities conducted under Alternative D do not change the cumulative outcomes described in 

Alternatives A and C, there would be a nominal to minor incremental increase in impacts to fish 

resources and EFH from activities under the proposed action for Alternative D.
Gulf of Mexico G&G Activities Programmatic EIS 4-199

4.4.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.4.2.1). The following discussion outlines the effects of the additional 

mitigation measures included under Alternative E on fish resources and EFH.

4.4.6.1 Impacts of Routine Activities

4.4.6.1.1 Reduced Level of Activity

The reduction of deep-penetration, multi-client activities by 10 percent or 25 percent would 

reduce the extent, severity, and timing of active acoustic sound sources, vessel and equipment 

noise, trash and debris, seafloor disturbance, drilling discharges, and entanglement as compared 

with Alternative A. The analysis of Alternative A concluded that the impacts would range from 

nominal to minor; however, the reduction in activity would not change the overall impact level 

determinations for these IPFs under Alternatives E1 and E2.

Under Alternatives E1 and E2, there would be a 10 percent or 25 percent reduction in 

activities, respectively, for deep-penetration, multi-client activities. A reduction in activities under 

Alternatives E1 and E2 could reduce the impacts of acoustic sound sources on fish resources and 

EFH. However, seismic airgun surveys will still be conducted throughout the AOI and the majority of 

fish resources will still be impacted by airguns. The effects will likely still include extended 

displacement, extensive damage (quantifiable loss depending on the habitat type) to EFH, and 

extensive disruption of behavioral patterns (including spawning, feeding, or ontogenetic migrations) 

that may adversely affect a species.

Minor impacts to fish resources and EFH affected by airguns would still be expected under 

Alternatives E1 and E2. There is no reduction in non-airgun HRG surveys under Alternatives E1 and 

E2; therefore, the overall impacts to smalltooth sawfish, Gulf sturgeon, fish resources, and EFH 

affected by electromechanical sound sources would be nominal. Under Alternatives E1 and E2, a 

reduction of deep-penetration, multi-client activities by 10 percent or 25 percent, respectively, for 

deep-penetration, multi-client activities would reduce the overall vessel and equipment noise and 

may reduce the risk of entanglement. However, negative effects on fish behavior are still expected 

to be short term and localized in areas where activity is concentrated. For this reason, impacts of 

vessel and equipment noise are expected to be nominal for smalltooth sawfish and Gulf sturgeon, 

and minor for fish resources and EFH under Alternatives E1 and E2. Impacts from entanglement 

would remain nominal. 

This mitigation does not apply to the other project-related IPFs and would not alter the 

impacts to fish resources and EFH from trash and debris, seafloor disturbance, or drilling 

discharges; impacts would remain nominal. 
4-200 Description of the Affected Resources and Impact Analysis

4.4.6.2 Impacts of an Accidental Fuel Spill

Under Alternatives E1 and E2, impacts of accidental fuel spills on fish resources and EFH 

would be very similar to those analyzed for Alternative C in Chapter 4.4.4.2. Alternatives E1 and E2 

would reduce the number of surveys and vessels conducting deep-penetration, multi-client surveys 

by 10 percent or 25 percent, respectively, but this reduction would not substantially change the risk 

of a small fuel spill because the majority of activities will continue to take place. A small diesel spill 

is expected to disperse rapidly and volatile components are expected to evaporate. If an accidental 

fuel spill occurs, it is anticipated that the spill size would be relatively small and the area of impact 

would be a small portion of the AOI; the type and severity of impacts to pelagic fish, as well as 

buoyant eggs and larvae in localized areas, would depend on the location of the event but are 

expected to range from nominal to minor. 

4.4.6.3 Cumulative Impacts

Impact analyses presented in Chapters 4.4.6.1 and 4.4.6.2 determined that activities 

projected to occur under Alternative E would result in nominal to minor impacts to fish resources 

and EFH, depending on the IPF. Mitigation measures for the proposed action under Alternative E 

are described in Chapter 2.5 and summarized in Chapter 4.4.6.1. A detailed impacts assessment 

under the cumulative scenario is provided in Alternative A (Chapter 4.4.2.3). The reduction of deeppenetration, multi-client activities (in line miles) by 10 percent (Alternative E1) or 25 percent 

(Alternative E2) would reduce the extent, severity, and timing of active acoustic sound sources, 

vessel and equipment noise, and entanglement; therefore, impacts for these IPFs would be 

incrementally decreased under Alternative E. Reductions in the line miles of deep-penetration,

multi-client activities would result in a net reduction of sound in the AOI. However, the changes 

under Alternative E do not change the impact level to the cumulative outcomes described in 

Alternative A. Therefore, there would be a nominal to minor incremental increase in impacts to fish 

resources and EFH under Alternative E.

4.4.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.4.2.1). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative F on fish resources and EFH.

4.4.7.1 Impacts of Routine Activities

4.4.7.1.1 Closure Areas

Alternative F would require area closures in the CPA Closure Area, the EPA Closure Area, 

the Dry Tortugas Closure Area, and the Flower Gardens Closure Area (Figure 2.6-1). The closures 

apply to all G&G activities, which would reduce the impacts of active acoustic sound sources, vessel 

equipment and noise, trash and debris, seafloor disturbance, drilling discharges, and entanglement 

on fish resources and EFH compared with Alternative A.
Gulf of Mexico G&G Activities Programmatic EIS 4-201

The purpose of this mitigation measure is to provide protection to marine mammals within 

the closure areas. This mitigation measure would provide an ancillary benefit to some coastal and 

pelagic fish species (Tables 4.4-1 through 4.4-4), as the effects on fish hearing and behavior 

(discussed in detail in Chapter 4.4.2.1) will be reduced following a reduction in active acoustic sound 

sources (e.g., seismic airgun and electromechanical sounds) and vessel and equipment noise. 

However, active acoustic sound sources and vessel and equipment noise will still be produced by 

G&G activities throughout the rest of AOI. Additionally, while activities may not be conducted within 

the closure areas, sound from seismic surveys, vessels, and equipment can propagate into the 

closure areas, which could have effects on fish behavior and hearing. The closure areas are small 

compared with the size of the AOI, and impacts to fish resources and EFH, smalltooth sawfish, and 

Gulf sturgeon will not be reduced outside the closure areas. Under Alternative F, there will be a 

reduction in seafloor disturbance, drilling discharges, and risk of entanglement from trash and debris 

in the closure areas. However, impacts from these IPFs are still possible outside the closure areas. 

Although reduced, overall impact levels under Alternative F would remain unchanged from the 

analysis in Alternatives A and C.

The impacts of active acoustic sound sources from airguns are expected to be nominal for 

smalltooth sawfish and Gulf sturgeon, and minor for fish resources and EFH under Alternative F. 

The mitigation measure does not apply to sound sources from non-airgun HRG surveys; therefore, 

the impact from electromechanical sources will be nominal for fish resources and EFH under 

Alternative F. Impacts of vessel equipment and noise are expected to be nominal for smalltooth 

sawfish and Gulf sturgeon, and minor for fish resources and EFH. This mitigation does not apply to 

the other project-related IPFs and would not alter the impacts to fish resources and EFH from trash 

and debris, seafloor disturbance, drilling discharges, or entanglement; impacts would remain 

nominal. 

4.4.7.2 Impacts of an Accidental Fuel Spill

Under Alternative F, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. Alternative F would change the location where G&G activities could be conducted; 

however, spills from seismic airgun surveys, non-airgun HRG surveys, and other G&G activities 

could still occur within the AOI. The closure area is small compared with the size of the AOI, and 

impacts will be reduced only within the closure areas. If an accidental fuel spill occurs, it is 

anticipated that the spill size would be relatively small and the area of impact would be a small 

portion of the AOI; the type and severity of impacts to pelagic fish, as well as buoyant eggs and 

larvae in localized areas, would depend on the location of the event but are expected to range from 

nominal to minor. 

4.4.7.3 Cumulative Impacts

Impact analyses presented in Chapters 4.4.7.1 and 4.4.7.2 determined that activities 

projected to occur under Alternative F would result in nominal to minor impacts to fish resources 

and EFH, depending on the IPF. Mitigation measures for the proposed action under Alternative F 

are described in Chapter 2.6 and summarized in Chapter 4.4.7.1. A detailed impacts assessment 
4-202 Description of the Affected Resources and Impact Analysis

under the cumulative scenario is provided in Alternative A (Chapter 4.4.2.3). Mitigation measures 

under Alternative F are similar to Alternative C with the addition of area closures in four areas: the 

CPA Closure Area; the EPA Closure Area; the Dry Tortugas Closure Area; and the Flower Gardens 

Closure Area. Most mitigation measures under Alternative F would not substantially change the 

extent, severity, or timing of activities in the proposed action; thus, the resultant impacts to fish 

resources and EFH also would not change. Mitigation measures under Alternative F that would 

change the timing and extent of activities in the proposed action are a seasonal restriction for 

operation of airguns in Federal and State coastal waters from February 1 through May 31, the 

prohibition of deep-penetration seismic airgun surveys within portions of the EPA (Chapter 2.2.2), 

and the four area closures for seismic airgun surveys. Overall, exposure of fish and EFH in the 

closure areas to sound would be reduced by the Alternative F closure areas; there would be a 

nominal to minor incremental increase in impacts to fish resources and EFH under Alternative F.

4.4.8 Impacts – Alternative G (No New Activity Alternative)

The IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.4.2.1) except that the IPF of entanglement is not included as part of 

Alternative F because no OBC surveys are part of the alternative.

4.4.8.1 Impacts of Routine Activities

Under Alternative G, no new permit/authorizations will be issued for G&G activities. 

Previously authorized activities would still occur under existing agreements or permits/authorizations 

but would drop off quickly. The VSP (2D only) and SWD surveys would continue at the level of 

activity in Table 2.7-1. The VSP surveys cover much shorter distances and use less sound energy 

(Appendix F, Section 1.1.5). Thus, noise levels from active acoustic sound sources, vessels, and 

equipment would not change immediately but would decrease over time. Impacts from other routine 

activities would also decrease over time.

Impacts from routine activities on smalltooth sawfish, Gulf sturgeon, fish resources, and EFH 

would remain similar to Alternatives A and C in the immediate term (nominal to minor) but then 

decline to no impact. A substantial reduction in non-VSP activities would likely reduce impacts 

from all routine activities on smalltooth sawfish, Gulf sturgeon, fish resources, and EFH to nominal. 

4.4.8.2 Impacts of Accidental Fuel Spills

The potential remains for spills to occur within the AOI following a reduction in activity. If an 

accidental fuel spill occurs, it is anticipated that the spill size would be relatively small and the area 

of impact would be a small portion of the AOI; the type and severity of impacts to pelagic fish, as well 

as buoyant eggs and larvae in localized areas, would depend on the location of the event but are 

expected to range from nominal to minor. 
Gulf of Mexico G&G Activities Programmatic EIS 4-203

4.4.8.3 Cumulative Impacts

Impact analyses presented in Chapters 4.4.8.1 and 4.4.8.2 determined that activities 

projected to occur under Alternative G would result in nominal to minor impacts to fish resources 

and EFH, depending on the IPF. The proposed activities under Alternative G are described in 

Chapter 2.7. The cease of activity for future G&G surveys requiring a permit/authorization from 

BOEM would substantially decrease the cumulative impacts from all IPFs. However, VSP and SWD 

surveys are expected to continue under Alternative G. Therefore, following cessation of the majority 

of activities, there would be a nominal incremental increase in impacts to fish and EFH from active 

acoustic sound sources, vessel and equipment noise, trash and debris, seafloor disturbances, 

drilling discharges, entanglement, and accidental fuel spills.

4.5 BENTHIC COMMUNITIES

4.5.1 Description of the Affected Environment

The benthic environment of the AOI is complex, with varied geological and geophysical 

features (Rowe and Kennicutt, 2009) in water depths ranging from <200 to 3,500 m (656 to 

11,483 ft). The benthic faunal assemblages of the GOM continental shelf in depths >200 m (656 ft) 

include deposit-feeding polychaete worms, crabs, lobsters, shrimps, clams, scallops, and oysters 

(USDOI, BOEM, 2012, 2013c, and 2013d). The GOM continental slope consists largely of fine, 

muddy sediments and includes numerous low-density, high-diversity faunal assemblages (Rowe and 

Kennicutt, 2001). Fishes, snails, sea stars, sand dollars, sea cucumbers, and polychaete worms 

(bristle worms) are all common on the continental slope of the GOM (USDOI, BOEM, 2013c and 

2013d). The majority of the benthic habitats within the AOI are within the abyssal zone (>1,000 m 

[3,280 ft]) and have biological assemblages that consist of more invertebrates and fewer fishes than 

the shelf and slope habitats. In AOI waters depths >2,300 m (7,546 ft), sea stars, sand dollars, and 

sea cucumbers are the dominant fauna (Rowe and Kennicutt, 2001) (USDOI, BOEM, 2013bc and 

2013d).

Although the GOM is dominated by soft bottom communities (Chapter 4.5.1.1), hard bottom 

and chemosynthetic communities occur throughout. Refer to Chapter 4.5.1.2 for a more detailed 

discussion of hard bottom communities in the GOM and Chapter 4.5.1.3 for a discussion of 

chemosynthetic communities in the GOM. Chapter 4.5.1.4 provides a discussion of species listed 

under the ESA as threatened or endangered and candidate species (i.e., species being assessed for 

listing under the ESA). Detailed discussion of benthic communities can be found in Appendix E, 

Section 5. 

As detailed in the Final PDARP/PEIS (Deepwater Horizon Natural Resource Damage 

Assessment Trustees, 2016), the Deepwater Horizon oil spill had an impact to some of the benthic 

communities in the CPA and therefore warrants brief mention here as part of this benthic 

communities’ “Description of the Affected Environment” section. However, potential future oil-spill 

impacts are not included in the IPFs considered in Chapter 4.3.2 of this Programmatic EIS since 

such spills are not a part of the proposed action.
4-204 Description of the Affected Resources and Impact Analysis

The Deepwater Horizon oil and dispersants came into direct contact with the seafloor by 

physical means, including sinking after release, settling of carbon ash after burning, biologically 

mediated sinking, and/or current transport into shallower waters.

In the deep sea, the Final PDARP/PEIS documented a footprint of over 2,000 km2 (770 mi2

) 

of impacts to benthic habitat surrounding the wellhead. Valentine et al. (2014) identified a 3,200-km2

region around the Macondo well calculated to represent 4-31 percent of the total Deepwater Horizon

oil sequestered in the deep ocean. Concentrations generally decreased with distance from the well. 

Within 3 km (2 mi) of the well, reductions in diversity of sediment-dwelling macrofauna and 

meiofauna were documented. At four separate known deepwater coral communities occurring at 

varying distances as far as 25 km (16 mi) from the well, varying degrees of impacts have been 

documented, including mortality of coral polyps, colonization of injured coral branches by 

opportunistic hydroid overgrowth, and branch loss (White et al., 2012; Hsing et al., 2013). 

In the shallower waters of the continental shelf, contact with some benthic communities, 

including sea-fan colonies and other soft corals in ~16-km2 (6-mi2

) area of the Pinnacle Trend 

(specifically at sites named Roughtongue Reef and Alabama Alps), occurred following submersion of 

oil/dispersant mixture. Surface waters containing oil and dispersants were likely pushed unusually 

deep as a result of Tropical Storm Bonnie’s strong meteorological conditions. Additional information 

pertaining to this resource and NMFS’ determination of the effects of the Deepwater Horizon

explosion, oil spill, and response may be found in the Final PDARP/PEIS (Deepwater Horizon

Natural Resource Damage Assessment Trustees, 2016).

4.5.1.1 Soft Bottom Communities

The continental shelf portions of the GOM have substrates that are primarily sandy 

sediments in the eastern GOM and sand, silt, and clay in the central and western GOM (Jenkins, 

2011). Benthic fauna in these areas include mollusks, crustaceans, and polychaetes. Vittor (2000) 

divided the northern GOM continental shelf into four assemblages based on the type of sediments 

and associated benthic fauna (Appendix E, Section 5.1). In the GOM, EFH for shrimp within the 

AOI extends from the U.S.-Mexico border east to Fort Walton Beach, Florida; shrimp EFH also 

extends into estuarine waters not covered in the AOI. Shrimp EFH is found in water depths ranging 

from 9 to 594 m (30 to 1,949 ft) and extends across all four assemblages as defined by Vittor (2000). 

The continental slope is a complex transitional zone characterized by varying ranges of productivity 

and faunal assemblages. Faunal assemblages of the continental slope and abyssal zone are 

described in the 2012-2017 WPA/CPA Multisale EIS (USDOI, BOEM, 2012) and in Appendix E. 

4.5.1.2 Hard Bottom Communities

While less common than ubiquitous soft bottom environments in the GOM, hard bottom 

environments are scattered across the GOM (Figure 4.5 1). This chapter focuses on deepwater 

hard bottom benthic communities; for a discussion of benthic chemosynthetic communities in the 

GOM, refer to Chapter 4.5.1.3. 
Gulf of Mexico G&G Activities Programmatic EIS 4-205

The GMFMC manages GOM corals through a coral management unit that considers 

142 species of stony and soft corals, including fire corals, stony corals, and black corals. The EFH 

for the coral management unit includes the total distribution of coral species and life stages 

throughout the GOM, including coral reefs in the North and South Tortugas Ecological Reserves, 

East and West FGBs, McGrail Bank, and the southern portion of Pulley Ridge. Additionally, EFH 

includes hard bottom areas on scattered pinnacles and banks from Texas to Mississippi, the shelf 

edge at the Florida Middle Grounds, the southwest tip of the Florida Reef Tract, and ephemeral hard 

bottom offshore of Florida from approximately Crystal River south to the Florida Keys (GMFMC, 

2005).

4.5.1.2.1 Deepwater Coral Communities

Some hard bottom carbonate substrate within the deepwater benthic environment of the 

GOM supports ahermatypic (non-reef building) corals. Moore and Bullis (1960) first described a 

deepwater coral community in the GOM comprised predominantly of the deepwater branching coral, 

Lophelia pertusa. BOEM has examined seismic data to identify areas of high acoustic reflectivity 

and have identified >28,000 areas that indicate possible hard bottom where deepwater reefs could 

exist (Shedd et al., 2012). Although only a small number of hard bottom habitats have been visually 

investigated, studies suggest that many of the deepwater hard bottom areas in the GOM have been 

colonized by chemosynthetic communities (Shedd et al., 2012). Colonies of L. pertusa are most 

commonly found in the upper shelf, but colonies have been found as deep as 3,000 m (9,842 ft) 

(USDOI, BOEM, 2012, 2013c, and 2013d). These findings suggest that suitable hard bottom areas 

exist throughout the AOI that could support deepwater coral communities. On September 10, 2015, 

the GMFMC released an online coral web mapper showing locations of black coral, octocoral, sea 

pen, soft coral, sponge, and stony coral in the GOM (GMFMC, 2015). The web mapper can be 

found on NOAA’s website (USDOC, NOAA, 2016).

4.5.1.2.2 Live Bottoms (Pinnacle Trend)

Variable relief, hard bottom features with extensions up to 20 m (66 ft) above the surrounding 

seafloor and up to 500 m (1,640 ft) in diameter were reported by Ludwick and Walton (1957) and 

Thompson et al. (1999) offshore Louisiana/Alabama. These “pinnacles” are known to exist in 

74 OCS lease blocks in a 103 x 26 km (64 x 16 mi) area of the northeastern CPA, particularly in 

portions of the Main Pass, Viosca Knoll, and Destin Dome lease areas. The Pinnacle Trend consists 

of several hard bottom habitats (USDOI, BOEM, 2012) including patch reefs, flat top reefs, reef-like 

mounds, ridges, scarps, and depressions. The pinnacles are located in depths from 74 to 120 m 

(243 to 394 ft). The relatively steep sides and tops of the pinnacles provide exposed hard bottom 

habitat for sponges, octocorals (Gittings et al., 1992), fishes (Weaver et al., 2002), and ahermatypic 

corals (Continental Shelf Associates, Inc., 1992). 

The biological diversity of the fauna in the Pinnacle Trend is directly related to the height of 

the pinnacle features (Gittings et al., 1992; Thompson et al., 1999) and distance from the Mississippi 

River Delta (Gittings et al., 1992). Biological diversity is higher on the tops and along the sides of 

higher relief pinnacles (Continental Shelf Associates, Inc., 1992). Near the seafloor along the base 
4-206 Description of the Affected Resources and Impact Analysis

of the hard bottom features, a relatively persistent nepheloid (turbidity) emanating from the 

Mississippi River outflow impedes the colonization of most sessile organisms. Only a few upright 

invertebrate species such as sea whips and sea fans can withstand the high turbidity (Weaver et al., 

2002).

4.5.1.2.3 Live Bottoms (Low Relief)

Low-relief hard bottom habitats are found in the EPA, CPA, and WPA. Low-relief live bottom 

habitats are found in the extreme northeastern corner of the CPA and are much more broadly 

distributed in the EPA. Low-relief hard bottom is characterized by features with <5 m (16 ft) of 

vertical relief above the surrounding seafloor. BOEM has instituted a Live Bottom (Low Relief) 

Stipulation to protect low-relief hard bottom habitats from impact by OCS energy exploration 

activities. BOEM conducts case-by-case reviews of plans, pipeline applications, structure removal 

applications, and ancillary activity applications in order to prevent routine bottom-disturbing activities 

from affecting live bottom (low-relief) areas. Habitats considered in the Live Bottom Stipulation 

include coral and spiny lobster EFHs. For a discussion on live bottom areas throughout the GOM, 

refer to Appendix E. 

4.5.1.2.4 Topographic Features

In the GOM, the term “topographic features” specifically refers to the 37 submerged banks 

that are protected from oil and gas activities and described in NTL 2009-G39 as “isolated areas of 

moderate to high relief that provide habitat for hard bottom communities of high biomass and 

diversity and large numbers of plant and animal species, and support, either as shelter or food, large 

numbers of commercially and recreationally important fisheries.” These banks are located in both 

the WPA (21 banks) and CPA (16 banks) (Table 4.5-1; Figure 4.5-2). The topographic feature 

formations are a result of protrusions of rock layers projected above the seafloor by the thick stratum 

of salt present beneath the GOM seafloor or represent fossilized shorelines (USDOI, BOEM, 2012). 

BOEM has mandated “No Activity Zones” around major topographic features in the GOM (refer to 

USDOI, MMS, 2008) to protect these submerged banks from anchoring and other disturbances that 

may occur during oil and gas exploration and production activities. Detailed descriptions of 

topographic features that are managed areas, such as the East and West Flower Garden Banks, 

Alderdice Bank, Bright Bank, Geyer Bank, McGrail Bank, Stetson Bank, and Sonnier Bank are 

presented in Chapter 4.7 and in USDOI, BOEM (2012, 2013c, and 2013d). Most of the banks 

support diverse and abundant fauna, including hermatypic and ahermatypic corals, coralline algae, 

octocorals, sponges, and fish.

4.5.1.2.5 Artificial Reefs

In addition to natural hard bottom habitats, artificial reefs provide substrate for the 

proliferation of live bottom communities (SAFMC, 2009) and associated fish assemblages. 

Figure 4.5-3 shows the locations of artificial reefs in the AOI. The USDOI’s Rigs-to-Reefs policy, 

implemented by BSEE and BOEM, is a process by which operators of decommissioned oil and gas 

platforms donate the material to coastal States for use as artificial reefs. Recreational diving and 
Gulf of Mexico G&G Activities Programmatic EIS 4-207

fishing and commercial fisheries benefit from the artificial reefs, which provide an additional option 

for conserving, managing, and/or developing fishery resources and can provide potential habitats for 

endangered or threatened species. As of 2013, there are >500 sites that have been approved by 

BSEE as artificial reef sites on the OCS (USDOI, BSEE, 2013) (Figure 4.5-3). Artificial reefs 

created by existing and future oil and gas infrastructure may contribute alternative habitat for corals 

and associated reef fauna by creating a complex habitat in a mostly featureless, soft bottom 

seafloor.

Artificial reefs are typically composed of material that provide hard surfaces such as metal, 

wood, and concrete that can support algae, barnacles, sponges, tubeworms, hydroids, anemones, 

oysters, and tunicates (Steimle and Figley, 1996; Steimle and Zetlin, 2000). The communities 

supported by artificial reefs are often similar to those occurring on natural hard bottoms, though the 

size, composition, location, and age of the reefs affect the structure and habitat value (Steimle and 

Zetlin, 2000; Wilson et al., 2003).

4.5.1.3 Chemosynthetic Communities

Chemosynthetic organisms are unique in that they use a carbon source rather than the 

photosynthesis-based food webs that support all other life on earth. Chemosynthetic bacteria have 

the ability to oxidize the chemicals present in seafloor vents (often hydrogen sulfide, hydrogen gas, 

or ammonia) into organic molecules used to produce biomass (often sugars). Since they were first 

discovered in the GOM in 1983 (Paull et al., 1984) at the base of the Florida Escarpment, 

>70 chemosynthetic communities have been found in the GOM (USDOI, BOEM, 2012, 2013c, and 

2013d) and it is likely that many more exist (Figure 4.5-1). All known chemosynthetic communities 

in the GOM are found in deep water (>300 m [984 ft]), well beyond the boundary of the continental 

shelf (USDOI, BOEM, 2012). Most hydrocarbon seeps are in areas where there is little sediment 

cover over underlying strata (USDOI, BOEM, 2012, 2013c, and 2013d) where hydrocarbons can 

vertically migrate through faults or other conduits to the surface. Many areas that fit these general 

descriptions have been seismically surveyed (Shedd et al., 2012), some of which have been proven 

to harbor chemosynthetic communities (USDOI, BOEM, 2013c, and 2013d).

Chemosynthetic communities have been classified into four general types based on the 

dominant seep organism: (1) vestimentiferan tubeworms; (2) mytilid mussels; (3) vesicomyid clams; 

and (4) infaunal lucinid or thyasirid clams (MacDonald et al., 1990). Each of the dominant organisms 

creates unique seep communities based on differing faunal density, chemical usage, and associated 

heterotrophic (non-carbon fixing) fauna (USDOI, BOEM, 2012). Growth rates of many organisms in 

these communities are extremely slow (Fisher, 1995), leading to both long-lived individuals and 

communities. Powell (1995) noted that many sites stayed biologically and geologically stable for 

500 to 4,000 years, with most communities showing no evidence of change in the dominant faunal 

organisms over time.
4-208 Description of the Affected Resources and Impact Analysis

4.5.1.4 Listed, Candidate, and Species of Concern

Two coral species were listed under the ESA as threatened in 2006: elkhorn coral (Acropora 

palmata) and staghorn coral (A. cervicornis). Following a petition in 2009 from the Center for 

Biological Diversity (2009) to list 83 species of reef-building corals under the ESA, NMFS issued a 

Final Rule (79 FR 67356) listing five additional Caribbean corals as threatened under the ESA: pillar 

coral (Dendrogyra cylindrus); lobed star coral (Orbicella annularis); mountainous star coral (Orbicella 

faveolata); star coral (Orbicella franksi); and rough cactus coral (Mycetophyllia ferox). This brings 

the total number of ESA-listed coral species in the Caribbean to seven. All of the threatened species 

of coral are found within the AOI (Puglise and Kelty, 2007), but they are mostly limited to the patch 

reefs surrounding the Florida Keys and off the southwest coast of Florida, with some occurring on 

the West and East FGBs (USDOC, NOAA, 2013a and 2013b), McGrail Bank, 18 Fathom, and Bright 

Bank reefs in the northwestern GOM (Rezak et al., 1983 and 1990). Small colonies of elkhorn coral 

were documented at the West and East FGBs in 2003 and 2005, respectively (Zimmer et al., 2006).

4.5.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, the IPFs that may impact benthic communities within the AOI 

include (1) active acoustic sound sources (e.g., airguns; non-airgun HRG sources such as highresolution boomers, sparkers, and CHIRP subbottom profilers; SBESs and MBESs; and side-scan 

sonars); (2) trash and debris, (3) seafloor disturbance, (4) drilling discharges, and (5) accidental fuel 

spills.

In considering the potential impacts to the associated benthic communities, it is important to 

make the distinction between the AOI and the planning areas. The total AOI area of 689,166 km2

(266,089 mi2

) includes 45,630 km2 (17,618 mi2) of State waters outside of the planning area 

boundaries; therefore, the total planning areas in Federal waters considered for benthic communities 

is 643,536 km2 (248,471 mi2

). The potential direct impacts considered here include the planning 

areas only and do not include State waters that extend to 3 nmi (3.5 mi; 5.6 km) offshore Louisiana, 

Mississippi, and Alabama, and 9 nmi (10.4 mi; 16.7 km) offshore Texas and Florida, which are 

beyond OCS lease block area boundaries and where the proposed BOEM-authorized G&G activities 

would not occur. This distinction is important because the EPA does not include the Florida Keys 

and other sensitive shallow-water habitats within State waters 3 or 9 nmi from shore. In these areas 

outside of the planning areas but within the AOI, only potential indirect impacts propagating into the 

area from proposed activities are considered to benthic communities.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact level. In contrast, the analysis of impacts 

associated with Alternatives B through G are organized by alternative-specific mitigation measures 

and how each these measures may reduce impact levels.
Gulf of Mexico G&G Activities Programmatic EIS 4-209

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For benthic 

communities, the significance criteria, as presented below, have been used to evaluate the level of 

impact for each IPF.

Nominal impacts to benthic communities would include impacts to soft bottom communities 

that might produce extremely small changes in abundance of individual species but no overall 

changes in species composition, community structure, and/or ecological functioning of soft bottom 

communities.

Minor impacts to benthic communities would include those that are detectable but not 

severe. Soft bottom communities showing a minor impact are expected to realize limited changes in 

species composition, community structure, or ecological functioning beyond that of normal variability.

Moderate impacts to benthic communities would include measurable, extensive, but not 

severe damage to sensitive communities, including live/hard bottom communities, deepwater corals, 

and chemosynthetic communities. For soft bottom communities, moderate impacts would include 

changes in species composition, community structure, and/or ecological functioning that are locally 

or spatially extensive, but not severe. Under the moderate impact category, some impacts may be 

irreversible.

Major impacts to benthic communities would include localized but long-lasting (decades) 

severe damage or short-term (<1 year) but spatially extensive severe damage to sensitive 

communities, including hard/live bottom communities, deepwater corals, and chemosynthetic 

communities. For soft bottom communities, major impacts also would encompass extensive and 

severe changes in species composition, community structure, and ecological functioning with 

measurable change in species composition or abundance beyond that of normal variability, or 

ecological function within a species range. Major impacts may be irreversible.

4.5.2.1 Impacts of Routine Activities

4.5.2.1.1 Active Acoustic Sound Sources

The impacts to benthic communities from impulsive sound generated by active acoustic 

sound sources (e.g., airguns and HRG surveys) are not well documented. There are only limited 

data on high anthropogenic sound levels and corresponding physiological effects on invertebrates. 

Potentially relevant data are limited to results from a study on the effects of seismic exploration on 

snow crabs on the Atlantic Coast of Canada (Boudreau et al., 2009) and controlled exposure of 
4-210 Description of the Affected Resources and Impact Analysis

cephalopods to low-frequency sound. Results from Boudreau et al. (2009) showed no short-term or 

long-term effects of seismic exposure in adult or juvenile crabs or crab eggs.

There is a dearth of data concerning sensitivity of aquatic invertebrates to sound. 

Cephalopods all have a specialized structure inside the cephalic (head) region called a statocyst 

(specialized sensory organ), which is thought to help an animal determine its position in space 

(orientation) and maintain balance (Budelmann, 1992). Available data suggest that cephalopods are 

capable of sensing the particle motion of sounds and detect low frequencies up to between 

1,000 and 1,500 Hz, depending on the species (Kaifu et al., 2008; Hu et al., 2009; Mooney et al., 

2010; Samson et al., 2014). There are few data indicating if and how invertebrates may use sound 

in behavior; although several species make sounds and may communicate with these sounds (e.g., 

Budelmann, 1992; Popper et al., 2001; Hawkins et al., 2014). Cephalopods have exhibited 

behavioral responses including inking, locomotor responses, body pattern changes, and changes in 

respiratory rates when exposed to low-frequency sounds under 1 kHz (Kaifu et al., 2008; Samson 

et al., 2014). Additionally, cephalopods exposed to sounds have exhibited damage to statocyst hair 

cells and other structures (i.e., damage to kinocilia, lesions on the epithelium, and ruptured plasma 

membranes) (André et al., 2011; Solé et al., 2013a and 2013b). There are no published data that 

indicate whether masking or TTS occurs in invertebrates, and there is little data to suggest whether 

sounds from seismic surveys would have any substantial impact on invertebrate behavior (Hawkins 

et al., 2014). Andriguetto-Filho et al. (2005) investigated the effects of seismic exploration on the 

economically important southern white shrimp (Litopenaeus schmitti), southern brown shrimp 

(Farfantepenaeus subtilis), and Atlantic seabob (Xyphopenaeus kroyeri) in northeastern Brazil. The 

study found no behavioral effects or damage to the hepatopancreas (glandular structure), gills, or 

gonads from exposures to sound with a source level of approximately 196 dB re 1 μPa at 1 m 

SPLrms. Payne et al. (2007 and 2008) also found no mortality or evidence of disorientation between 

control and experimental groups of American lobster (Homarus americanus) exposed to sounds at 

202 and 227 dB re 1 μPa SPLp-p. 

Some invertebrates may be especially sensitive to substratum vibrations. André et al. (2011) 

conducted controlled exposure experiments on four cephalopod species (i.e., Loligo vulgaris, Sepia 

officinalis, Octopus vulgaris, and Illex coindetii), subjecting them to low-frequency sound. Exposure 

to low-frequency sounds resulted in permanent and substantial alterations of the sensory hair cells 

of the statocysts. Several aquatic decapod crustaceans produce sounds, and many are able to 

detect vibration through the substrate and the water at sensitivities sufficient to determine the 

proximity of other organisms. However, it remains uncertain if these invertebrates respond to 

propagated sound waves farther from the source (Normandeau Associates, Inc., 2012).

There are four potential types of impacts to marine invertebrates from exposure to seismic 

survey noise (e.g., airguns): pathological; physiological; behavioral; and soundscape orientation 

associated with larval settlement. Pathological effects include lethal or permanent sublethal injury to 

organisms. Physiological effects include temporary and permanent primary and secondary stress 

responses (e.g., changes in levels of enzymes and proteins). Behavioral effects include temporary 

or permanent changes in behavior (e.g., feeding, startle, and avoidance behavior). Temporary 
Gulf of Mexico G&G Activities Programmatic EIS 4-211

acoustic soundscape changes could impact acoustic orientation used for larval settlement. Very few 

specific data are available regarding seismic sound impacts that may cause pathological or 

physiological effects on invertebrates, and these data are limited to a small number of invertebrate 

species and life stages. Most studies address behavioral responses to sound. McCauley et al. 

(2000a) studied caged squid, with results showing a strong startle and avoidance response from 

exposure to an airgun. With the use of ramp-up, the strong startle response was not observed, but 

the avoidance response was noted (i.e., individuals stayed close to the water surface during airgun 

operations), indicating that behavioral changes and avoidance to an operating airgun by squid may 

occur. André et al. (2011) indicated that captive giant squid exposed to short sweeps of relatively 

low-intensity, low-frequency sound between 50 and 400 Hz for 2 hours resulted in permanent and 

substantial alterations in the sensory hair cells of the statocysts. However, it is recognized that 

exposure parameters included long-term, confined exposure (i.e., the study was performed in a 

laboratory setting with specimens in small tanks). Observations obtained in such experimental 

settings are difficult to apply to open field conditions where sound propagation and attenuation may 

be very different, as are the conditions of exposure to animals.

All of the more serious effects of intense seismic survey signals occur close to the array, and 

configuration of airguns arrays focus the sound energy downward, so the highest energy would be 

directly beneath the seismic source (McCauley, 1994). Seismic airgun arrays produce a sound field 

that is directive at longer distances (tens of meters) from the array, characterized by a main beam 

directed down through the water into the seafloor with side lobes that radiate significant amounts of 

sound energy horizontally away from the array. As discussed previously, active acoustic sound 

sources from seismic activities have not been determined to have significant impacts to benthic 

communities within the planning areas; propagation of sound outside of the planning areas would 

have lower potential for producing impacts. Therefore, impacts to all benthic communities from 

active acoustic sound sources would be nominal. 

4.5.2.1.2 Trash and Debris

The G&G activities for oil and gas, marine minerals, and renewables will include vessel and 

platform acoustic surveys; non-acoustic HRG surveys, including gravity and magnetic surveys; 

airborne and passive remote surveys; and a wide variety of geotechnical surveys, including bottom 

sampling; and shallow test drilling. Many of these operations require multiple levels of vessel 

support (Table 3.2-7). Any of these operations could be on location for a few weeks to a few of 

months and are expected to occur throughout the projected 10-year timeframe. Due to the 

prolonged presence of G&G activities, there is the potential for accidental releases of trash and 

debris that could impact benthic communities by forceful contact, entanglement, and/or burial.

The effects of debris lost overboard from offshore drilling operations in the U.S. GOM have 

been addressed by several authors (e.g., Shinn et al., 1989 and 1993; Dustan et al., 1991; Shinn 

and Lidz, 1992). These studies have evaluated operations in variable water depths (i.e., 21 to 149 

m [69 to 489 ft]) over different substrates and at variable times following the completion of drilling. 
4-212 Description of the Affected Resources and Impact Analysis

Survey, sampling, and test well drilling operations generate trash, which is comprised of paper, 

plastic, wood, glass, and metal (Chapter 3.3.1.7).

All survey vessels performing work within U.S. jurisdictional waters are expected to comply 

with Federal regulations and MARPOL, as amended by the 1978 Protocol (MARPOL 73/78) 

(Chapter 3.3.1.7). In addition, all authorizations for shipboard surveys would include guidance for 

marine debris awareness covered under NTL 2015-BSEE-G03 (Appendix B). Because operators 

must comply with Federal regulations and would be expected to follow the guidance provided by 

BOEM, the amount of trash and debris accidentally lost offshore would be minimal, some of which 

could sink to the seafloor. Therefore, impacts from trash and debris on benthic communities, as 

generated by seismic survey vessels, sampling, shallow well drilling, and other G&G-related 

activities, would be nominal. 

4.5.2.1.3 Seafloor Disturbance

There are several G&G activities that could cause seafloor disturbance, including sampling 

(e.g., bottom sampling, shallow coring, jet probing), placement and removal of equipment on the 

seafloor (e.g., OBCs, anchors, receivers, monitoring buoys), and the installation of up to two drill test 

wells (Chapter 3.3.1.8). Soft and hard/live bottom communities could be affected by these G&G 

activities.

Proposed activities under Alternative A include bottom sampling in all three program areas, 

including CPT samples, core samples, grab samples, vibracores, and jet probes (Table 3.2-8). The 

total of all bottom samplings is 2,238 samplings in all three program areas. Collection of each 

sample is estimated to disturb an area of approximately 10 m2 (108 ft2

), although the actual area of 

the core or grab extracted may be much smaller. The maximum total area disturbed by bottom 

sampling is expected to be approximately 22,380 m2 (240,896 ft2

) (Table 3.2-8).

Proposed activities also include the installation of drill test wells and one COST well that 

could impact benthic resources. For this impact analysis, the area of seafloor disturbance is 

assumed to average approximately 20,000 m2 (215,278 ft2

) per well (Table 3.2-8). If the two drill 

test wells and one COST well in the proposed action scenario were drilled, the total seafloor 

disturbance would be approximately 60,000 m2 (645,835 ft2

) (Table 3.2-8), which is an extremely 

small portion of the total seafloor area of the planning areas. 

There is the potential for the installation of two bottom-founded monitoring buoys as part of 

the renewable energy program. An anchor for boat-shaped or discus-shaped buoys is expected to 

produce a footprint of approximately 0.56 m2 (6 ft2

) and an anchor sweep of approximately 3.4 ha 

(8.4 ac) (Chapter 3.3.1.8). If both buoys were installed, the total impact area would be would be 

6.8 ha (17 ac), including a 1.2-m2 (13-ft2

) footprint for the anchors and 6.8 ha (17 ac) for the sweep 

area, which is an extremely small portion of the seafloor within the planning areas. The anchor 

sweep impacts are caused by the anchor chains or lines dragging across the soft bottom substrate; 

sediments are not removed and only the surficial sediments and associated soft bottom communities 
Gulf of Mexico G&G Activities Programmatic EIS 4-213

are impacted. No overall changes in species composition, community structure, or ecological 

functioning of soft bottom communities are expected (Grannis, 2005).

Certain surveys in oil and gas exploration, such as 3D, 4D, and WAZ, require placement of 

anchors, nodes, cables, sensors, and other equipment on or in the seafloor. The OBC and OBN 

surveys, vertical cable surveys, CSEM surveys, and MT surveys involve placement of sensors and 

anchors on the seafloor. In VSPs, receivers are placed in well boreholes in the seafloor. Each of 

these activities would temporarily affect a small area of seafloor. After a survey is completed, the 

sensors are removed and anchors are either removed or left in place (if biodegradable). The OCS 

lease blocks where these surveys would be conducted could be anywhere within the planning areas. 

Locations and projected levels are not estimated; however, nodal surveys are relatively uncommon 

and are typically used in shallow waters. The total area of seafloor disturbed by survey cables, 

sensors, and anchors has not been calculated.

As outlined in NTLs 2009-G39 and 2009-G40, BOEM would require site-specific information 

regarding potential sensitive benthic communities (including hard/live bottom areas, deepwater coral 

communities, and chemosynthetic communities) prior to approving any G&G activities involving 

seafloor-disturbing activities or the placement of bottom-founded equipment (e.g., OBCs, anchors, 

and receivers) or structures in the AOI (Appendix B). In addition, as detailed in NTLs 2009-G39 

and 2009-G40, setbacks from sensitive bottom communities apply to seafloor-disturbing activities. 

These setbacks would include distancing seafloor-disturbing activity at least 500 ft (152 m) from a 

No Activity Zone surrounding a topographic feature; at least 100 ft (30 m) from any shallow-water 

hard bottom, pinnacle, live bottom, or Potentially Sensitive Biological Features; and 250 ft (76 m) 

from a deepwater benthic community (i.e., chemosynthetic communities and deepwater corals). In 

addition, BOEM does not allow wells to be drilled within 2,000 ft (610 m) of a deepwater benthic 

community. Site-specific plans will be reviewed individually and will likely apply similar setbacks as 

default buffer zones when G&G activities take place in the planning areas. BOEM’s renewable 

energy program has developed guidelines for these site-specific surveys. All authorizations for 

seafloor-disturbing activities would be subject to restrictions to protect corals, hard/live bottom, and 

deepwater benthic communities; may include requirements for mapping and avoidance in areas 

where these communities are known or suspected; and may require photographic or video surveys 

of areas where bottom-founded instrumentation and appurtenances are to be deployed.

BOEM would use this site-specific information and these setbacks to ensure that physical 

impacts to sensitive benthic communities are avoided; deepwater coral systems, chemosynthetic 

communities, and hard/live bottom habitats within the planning areas would be protected through 

distancing requirements from proposed bottom sampling activities. These distancing requirements 

will minimize or prevent potential impacts to hard/live bottom, chemosynthetic communities, and 

deepwater coral systems from seafloor sampling. In considering all projected activities over the 

10-year time period, a total of 150,381 m2 (1,618,688 ft2

) (Table 3.2-8) of seafloor would be 

disturbed, and the potential impacts to benthic communities under this alternative would be nominal. 
4-214 Description of the Affected Resources and Impact Analysis

As discussed in the introduction to this chapter (Chapter 4.5.2), BOEM’s jurisdiction includes 

the planning areas but not the areas of the AOI within State waters. Excluded from seafloordisturbing activities would be the hermatypic coral reefs of the Florida Keys, Dry Tortugas National 

Park, Tortugas Ecological Reserve, the East and West FGBs, McGrail Bank, and Pulley Ridge. No 

BOEM-authorized G&G activities would occur in these areas; therefore, seafloor-disturbing activity 

impacts were not evaluated for hermatypic coral reefs. In addition, as detailed in NTLs 2009-G39 

and 2009-G40, setbacks from sensitive bottom communities apply to seafloor-disturbing activities for 

potential sensitive benthic communities.

4.5.2.1.4 Drilling Discharges

The oil and gas scenario assumes that up to two test wells and one COST well would be 

drilled in the planning areas during the time period of this Programmatic EIS. The test wells are 

drilled using conventional rotary drilling techniques, which is the same as routinely used for drilling 

oil and gas exploration and development wells. During the process, drilling fluid and cuttings would 

be discharged, dispersed in the water column, and accumulated on the seafloor (Chapter 3.3.1.9). 

Impacts to the benthic environment would include changes in sediment grain size and benthic 

community effects because of burial and smothering, anoxia, and sediment toxicity.

The average exploration well in the GOM is approximately 3,674 m (12,054 ft) below mudline 

(USDOI, MMS, 2007b). Each well discharges approximately 7,000 to 9,700 bbl of WBF and 1,500 to 

2,500 bbl of cuttings (USEPA, 1993 and 2000). Assuming an average of 2,000 bbl of cuttings and 

8,350 bbl of drilling fluid discharged per well, the total volumes for one COST wells and two test 

wells would range from 2,000 to 6,000 bbl of cuttings and from 8,350 to 25,050 bbl of drilling fluid.

The typical drilling fluids in widespread use on the OCS are WBFs or synthetic-based fluids 

(SBFs). Only WBF, WBF solids, and treated SBF cuttings may be discharged directly into the 

ocean. During well intervals when WBF systems are used; cuttings and adsorbed WBF solids are 

discharged to the ocean at a rate of 0.2 to 2.0 m3

/hr (Neff, 1987). Overboard discharge of WBF 

results in increased turbidity in the water column, alteration of sediment characteristics because of 

coarse material in cuttings, and elevated concentrations of some trace metals (NRC, 1983; Neff, 

1987). In shallow environments, WBFs disperse rapidly in the water column immediately after 

discharge and quickly descend to the seafloor; in deeper water, however, fluids discharged at the 

sea surface are dispersed over a wider area (Neff, 1987).

Discharges of WBF and cuttings with trace amounts of adhering SBF from the rig may affect 

benthic communities, primarily within several hundred meters of each wellsite. The fate and effects 

of WBF discharges have been reviewed by the NRC (1983) and Neff (1987); impacts of SBF 

cuttings discharges have been summarized by Neff et al. (2000). In general, cuttings with adhering 

SBF tend to clump together and form cuttings accumulations close to the drill site. Areas of SBF 

cuttings deposition may develop elevated organic carbon concentrations and anoxic conditions 

(Continental Shelf Associates, Inc., 2006). Where SBF cuttings have been discharged from a series 

of wells, cuttings tend to accumulate and concentrations have exceeded 1,000 mg/kg; benthic 
Gulf of Mexico G&G Activities Programmatic EIS 4-215

infaunal communities may be adversely affected by the toxicity of the base fluid and organic 

enrichment (with resulting anoxia) (Neff et al., 2000). In these instances, infaunal numbers may 

increase and diversity may decrease as opportunistic species that tolerate low oxygen and high 

hydrogen sulfide (H2S) predominate (Continental Shelf Associates, Inc., 2006). The localized and 

limited drilling activity proposed under the G&G activity scenario strongly suggests that sizable 

cuttings accumulations and associated impacts would not occur.

Detectable drilling fluid and cuttings deposits may persist for 5 years or more around well

sites, particularly in areas where multiple wells have been drilled (Continental Shelf Associates, Inc., 

2006). Recovery of affected benthic communities typically begins as soon as a discharge ceases 

(Neff et al., 2005) and relies on recruitment of new fauna from planktonic larvae and immigration into 

disturbed areas from adjacent undisturbed sediments. The precise timing of recovery depends on a 

series of factors: the nature of the benthic community (e.g., species composition, reproductive 

triggers, larval mode); the physical characteristics of the benthic environment; and the chemical 

characteristics of the benthic environment (Neff et al., 2005). Neff et al. (2000) indicate that within 

3 to 5 years of the cessation of SBF cuttings discharges, a complete recovery of the benthic 

community is possible; such recovery requires that the concentrations of SBF components (e.g., 

organics) in the sediments decrease to sufficiently low levels and that sediment oxygen 

concentrations increase to levels that can support benthic infauna. 

The areal extent of impacts from drilling discharges during the proposed action would be 

relatively small. Assuming a typical effect radius of 500 m (1,640 ft), the affected area around each 

wellsite would represent approximately 3 percent of the seafloor within an OCS lease block 

(approximately 9 mi2 [23 km2

]). Soft bottom communities are ubiquitous regionally, and the impact 

on soft bottom communities would be nominal within the AOI. Given BOEM’s requirement for sitespecific information regarding potential sensitive benthic communities and the application of 

setbacks from these resources as discussed in Chapter 2.1.2, impacts from drilling discharges on 

hard/live bottom areas, deepwater coral communities, and chemosynthetic communities of the AOI 

are expected to be nominal. 

4.5.2.1.5 Routine Activities Impact Conclusions

Active acoustic sound sources from seismic activities have not been determined to have 

significant impacts to benthic communities, and impacts are expected to be nominal. Impacts from 

trash and debris are expected to be nominal due to the existing requirements in place to prevent 

and minimize accidental loss. Based on the limited spatial extent of proposed bottom-disturbing 

activities and the requirements in place to minimize impacts to sensitive benthic communities, 

impacts are expected to be nominal for seafloor disturbance and drilling discharges.

4.5.2.2 Impacts of an Accidental Fuel Spill

An accidental spill event could result in the release of diesel or other fuel by a survey vessel. 

Based on USCG spill statistics, a spill scenario was developed in Chapter 3.3.2 that assumes a 

diesel spill volume of 1.2 to 7.1 bbl. Spills occurring at the ocean surface would disperse and 
4-216 Description of the Affected Resources and Impact Analysis

weather. Volatile components of the fuel would evaporate. Diesel and other fuels used for operation 

of survey vessels are light and would float on the ocean surface. There is the potential for a small 

proportion of the heavier fuel components to adhere to particulate matter (PM) in the upper portion of 

the water column and sink. The PM contaminated with diesel fuel eventually would reach the 

benthos within or outside the AOI, depending on spill location, water depth, ambient currents, and 

sinking rate. However, given the relatively small size of the spill and the loss of most spilled fuel 

through evaporation and dispersion, a small diesel fuel spill would be expected to result in nominal

impacts to benthic communities.

4.5.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for benthic communities are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI.

The G&G activities have been ongoing in the GOM for at least the past 30 years and it is 

reasonable to assume they will continue into the future; however, for the purpose of this 

Programmatic EIS, the cumulative analysis assesses a 10-year timeframe to coincide with the 

proposed action because it is not expected that G&G activities will have lasting effects or extend 

beyond the 10-year timeframe of this Programmatic EIS. Impact analyses presented in Chapters 

4.5.2.1 and 4.5.2.2 determined that activities projected to occur under Alternative A would result in 

nominal impacts to benthic communities.

4.5.2.3.1 Active Acoustic Sound Sources

Active acoustic sound sources, including airguns and electromechanical sources from State 

waters’ oil and gas activities, vessel and equipment noise, as well as sonar and echolocation 

sources on fishing and commercial vessels, projected under the proposed action are described in 

Chapter 3.4.1. Scientific research vessels and other non-survey vessel activities would be expected 

to have similar types of active acoustic sound sources. Active acoustic sound sources associated 

with military activities in the GOM (Chapter 3.4.3.6) could involve military operations testing of 

air-to-air and air-to-surface operations as well as underwater explosives such as mines. The active 

acoustic sound sources under the proposed action would contribute to noise levels within the AOI. 

Noise from G&G operations would be survey or activity based, occurring on a transient and 

intermittent basis over the 10-year period of interest. The cumulative contribution of the active 

acoustic sound sources from the proposed action (Chapter 4.5.2.1) would be an increase in ocean 

noise for these activities of the cumulative scenario.
Gulf of Mexico G&G Activities Programmatic EIS 4-217

Overall, Chapter 4.5.2.1 determined there would be increases in ambient noise levels within 

specific portions of the AOI during G&G operations; the impacts associated with the proposed action 

would result in a nominal incremental increase in noise impacts to benthic communities under the 

cumulative scenario.

4.5.2.3.2 Trash and Debris

A point source investigation was conducted for oil and gas activities on the OCS (USDOI, 

MMS, 1996), indicating that the offshore oil and gas industry contributed 13 percent of all debris 

collected. Because of this study, the offshore oil and gas industry’s adherence to the laws and 

regulations has greatly reduced their share of the trash and debris deliberately jettisoned into the 

GOM.

Trash and debris from the cumulative activities would include stationary facilities associated 

with oil and gas exploration and development, oil and gas support vessel operations, renewable 

energy development, and marine minerals use. Future activities would be required to follow 

MARPOL 73/78 and marine debris awareness covered under NTL 2015-BSEE-G03. Because 

operators must comply with Federal regulations and would be expected to follow the guidance 

provided by BOEM, the amount of trash and debris offshore would be minimal as only accidental 

loss of trash and debris is anticipated, some of which could sink to the seafloor and harm benthic 

communities. As discussed in Chapter 4.5.2.1, the proposed activities under Alternative A would 

follow the same regulations and guidance, resulting in nominal impacts. Therefore, a nominal

incremental increase in impacts from trash and debris to benthic communities under the cumulative 

scenario is expected.

4.5.2.4 Seafloor Disturbances

Seafloor-disturbing activities associated with the oil and gas program over the next 10 years 

will include the construction and installation of a maximum of 8,233 exploration and production wells, 

the installation of a maximum of 507 production structures (e.g., caissons and multi-leg platforms), 

and a maximum of 17,437 km (10,835 mi) of pipelines (Table 3.4-2). Production structures can 

range from small caissons impacting hundreds of square feet of seafloor to much larger multiple-leg 

platforms to support multi-level production facilities with associated larger seafloor-impacting 

footprints, each impacting tens of thousands of square feet of seafloor (LGL Limited Environmental 

Research Associates and Science Applications International Corporation, 1998). Offshore facility 

decommissioning, including platform and caisson removal, typically use one of two primary methods 

to sever structures attached to the seafloor: mechanical severance or explosive severance. 

Explosive charges generally are placed inside the platform legs or conductors at a depth of 4.6 to 

7.6 m (15 to 25 ft) below the seafloor, which disturbs the seafloor adjacent to the legs. Historical 

structure-removal permit applications for the GOM between 2002 and 2013 are summarized in 

Tables 3.4-3 and 3.4-4. Because there are limited renewable energy activities projected, seafloor 

disturbances from such activities would be localized and evaluated to minimize seafloor 

disturbances near benthic communities, if they occur.
4-218 Description of the Affected Resources and Impact Analysis

Seafloor disturbances associated with the other major factors would include commercial and 

recreational fishing activities; dredge material disposal; existing, planned, and new cable 

infrastructure; military activities; scientific research; and cumulative vessel activity levels. Seafloor 

disturbances associated with marine mineral uses would be in pre-determined OCS sand resource 

areas (Chapters 3.2.3 and 3.4.1.4) for use in coastal restoration. Projected volumes of sand 

material from sand borrow projects over the 10-year period are provided in Table 3.2-5. The sand 

resource areas would be selected for the desired sand sediment qualities, and seafloor disturbances 

would be localized to the sand resource area. Seafloor-disturbing activities associated with the 

proposed alternative activities over the projected 10-year period would include a maximum of 

3 wells, 2 bottom-founded monitoring buoys, and 2,238 bottom samplings (Table 3.2-8). The 

cumulative seafloor-disturbing activity impacts would result from the placement of material covering 

the seafloor, anchoring, bottom fishing gear, and bottom sampling; however, these activities must 

avoid known benthic communities and are required to minimize direct impacts. One renewable 

energy development is being considered under the proposed action scenario, and it would be 

required to minimize benthic community impacts from seafloor disturbances. The proposed action 

was determined to result in nominal impacts to benthic communities (Chapter 4.5.1.4) and, due to 

the minimal associated impacts overall, would result in a nominal incremental increase in impacts 

from seafloor disturbances.

4.5.2.4.1 Drilling Discharges

Impacts to benthic communities from drilling discharges associated with two shallow test 

wells and a single COST well projected for the proposed action activities would be insignificant when 

compared incrementally to the cumulative impacts associated with the 8,233 oil and gas exploration 

and production wells projected in the OCS (Chapter 3.4.1.1). Therefore, a nominal incremental 

increase in impacts from drilling discharges to benthic communities is expected under the cumulative 

scenario.

4.5.2.4.2 Cumulative Impact Conclusions

Increases in ambient noise levels within specific portions of the AOI are expected during 

G&G operations; however, the impacts associated with the proposed action would result in a 

nominal incremental increase in noise impacts to benthic communities under the cumulative 

scenario. Seafloor disturbances associated with the cumulative scenario would include OCS 

activities, oil and gas decommissioning, renewable energy development, marine minerals, and

commercial and recreational fishing activities; dredge material disposal; trash and debris; existing, 

planned, and new cable infrastructure; military activities; scientific research; and cumulative vessel 

activity levels. When compared with historic levels of activities within the GOM, proposed activities 

do not represent a significant incremental increase to effects under the cumulative scenario. 

Impacts to benthic communities are nominal and when compared with historic spill events, the 

contribution of this projected spill is nominal. 
Gulf of Mexico G&G Activities Programmatic EIS 4-219

4.5.2.4.3 Accidental Fuel Spills

As discussed in Chapter 3.4, the AOI includes an active commercial shipping and marine 

transportation system, recreational vessel traffic, and an extensive system of offshore oil and gas 

production facilities. However, the potential for collision and product transfer fuel spills from vessels 

involved in the cumulative activities scenario is considered remote. Diesel and other fuel used for 

operation of support vessels is light and would float on the sea surface where is it subjected to 

weathering, dispersion, and dissolution. Heavier fuels may be used in larger commercial vessels 

involved in marine transportation. Heavier fuels (i.e., Bunker C) have specific gravities similar to 

seawater and so can float, suspend in the water column, or sink, depending on small changes in 

water density.

With the use of AIS on large sea-going vessels, radar, and licensing of vessel captains, the 

potential of a vessel collision occurring is low, and the potential for a resultant spill is even lower. An 

accidental fuel spill from a support or fishing vessel could occur, but the likelihood of such an event 

is remote. Accidental fuel spills from vessels associated with maintenance dredging of Federal 

channels and coastal restoration programs would be limited to shallower coastal areas where 

dredging is required and where coastal restoration programs would be located. If an accidental fuel 

spill occurs, it is anticipated that the spill size would be relatively small and the area of impact would 

be a small portion of the AOI; the type and severity of impacts to benthic communities would depend 

on the location of the event but are expected to be nominal (Chapter 4.5.2.2).

The potential for fuel spills from vessels involved in the cumulative scenario would be higher 

than that expected under the proposed action because of the magnitude of vessel activity in the AOI 

and the high number of vessel transits. However, the increase in the potential for accidental fuel 

spills arising from vessel collision during G&G activities would be considered extremely small. The 

impacts associated with the proposed action and the low probability of a G&G activity-related fuel 

spill would result in a nominal incremental increase in benthic community impacts under the 

cumulative scenario.

4.5.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.5.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative B on benthic communities.

4.5.3.1 Impacts of Routine Activities

4.5.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to April 30)

As evaluated in Alternative A (Chapter 4.5.2.1), impacts to benthic communities were 

determined to be nominal. Most of the additional mitigation measures (such as expanded PSO, the 

minimum separation distance, and use of required PAM) included in Alternative B would not reduce 

impacts to benthic communities. The additional mitigation measures included in Alternative B do not 

include additional restrictions that would change benthic community impacts from seafloor 
4-220 Description of the Affected Resources and Impact Analysis

disturbances. The seasonal restriction in Federal coastal waters from January 1 to April 30 would 

reduce active acoustic impacts from airgun surveys to benthic communities, but it would still result in 

nominal impacts over the rest of the year.

4.5.3.1.2 Seismic Restrictions in the Areas of Concern within the EPA

The impacts to benthic communities from deep-penetration seismic airgun surveys would be 

reduced in the EPA due to the restriction in Alternative B and would still result in nominal impacts to 

benthic communities across the rest of the AOI.

4.5.3.1.3 Routine Activities Impact Conclusions

Active acoustic sound sources from seismic activities have not been determined to have 

significant impacts to benthic communities, and impacts are expected to be nominal. Impacts from 

trash and debris, bottom-disturbing activities, and drilling discharges would not be affected by the 

mitigations in Alternative B and would remain nominal. 

4.5.3.2 Impacts of an Accidental Fuel Spill

Impacts from accidental fuel spills on benthic communities are evaluated for Alternative A in 

Chapter 4.5.2.2. Because of the relatively small volume of fuel and the rapid weathering and 

dissipation qualities of the fuel in water, an accidental diesel fuel spill would be expected to result in 

nominal impacts to benthic communities. Area closures and restrictions included in the additional 

mitigation of Alternative B would result in restricted vessel activities, further reducing the potential 

impacts from accidental fuel spills to benthic communities. Impacts would remain nominal. 

4.5.3.3 Cumulative Impacts

Impact analyses presented in Chapters 4.5.3.1 and 4.5.3.2 determined that activities 

projected to occur under Alternative B would result in nominal impacts to benthic communities. 

Mitigation measures for the proposed action under Alternative B are described in Chapter 2.2 and 

summarized in Chapter 4.5.3.1. A detailed impacts assessment under the cumulative scenario is 

provided in Alternative A (Chapter 4.5.2.3). Multiple mitigation measures under Alternative B would 

not change the extent, severity, or timing of activities in the proposed action; thus, the resultant 

impacts to benthic communities would not change.

Some of the additional mitigation measures included in Alternative B, while reducing impacts 

to other resources, would have no effect on the associated impacts to benthic communities, such as 

the expansion of the PSO Program and PAM requirement during periods of reduced visibility. Other 

mitigation associated with this alternative, seasonal coastal water restrictions for surveying, and 

additional airgun seismic survey restricted areas will reduce vessel activities within portions of the 

AOI, resulting in reductions in the potential impacts from active acoustic sound sources, trash and 

debris, and accidental fuel spills. The Alternative B mitigation of increasing vessel separation 

distances during simultaneous airgun seismic surveys could reduce the cumulative impacts common 

to benthic community IPFs from active acoustic sound sources. While these mitigation measures 
Gulf of Mexico G&G Activities Programmatic EIS 4-221

would reduce the cumulative impacts from the associated IPFs, it would not significantly change the 

degree of impacts from the proposed action. Incremental increase in impacts to benthic 

communities from active acoustic sound sources, trash and debris, seafloor disturbances, drilling 

discharges, and accidental fuel spills would be nominal for Alternative B.

4.5.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.5.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative C on benthic communities.

4.5.4.1 Impacts of Routine Activities

4.5.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to May 31)

As evaluated in Alternative A (Chapter 4.5.2.1), impacts on benthic communities were 

determined to be nominal. Most of the additional mitigation measures included in Alternative C 

would not reduce impacts to benthic communities. The additional mitigation measures included in 

Alternative C do not include additional restrictions that would change benthic community impacts 

from seafloor disturbances or drilling discharges. The seasonal restriction in Federal coastal waters 

from February 1 to May 31 would reduce active acoustic impacts from airgun surveys to benthic 

communities and would still result in nominal impacts.

4.5.4.1.2 Routine Activities Impact Conclusions

Active acoustic sound sources from seismic activities have not been determined to have 

significant impacts to benthic communities, and impacts are expected to be nominal. Impacts from 

trash and debris, bottom-disturbing activities, and drilling discharges would not be affected by the 

mitigations in Alternative C and would remain nominal. 

4.5.4.2 Impacts of an Accidental Fuel Spill

Impacts from accidental fuel spills on benthic communities are evaluated for Alternative A in 

Chapter 4.5.2.2. Due to the relatively small volume of fuel and the rapid weathering and dissipation 

of the fuel in water, an accidental diesel fuel spill would be expected to result in nominal impacts to 

benthic communities. Area closures and restrictions included in the additional mitigation of 

Alternative C would result in restricted vessel activities, further reducing the potential impacts from 

accidental fuel spills on benthic communities; therefore, impacts would be nominal. 

4.5.4.3 Cumulative Impacts

Impact analyses presented in Chapters 4.5.4.1 and 4.5.4.2 determined that activities 

projected to occur under Alternative C would result in nominal impacts to benthic communities. 

Mitigation measures for the proposed action under Alternative C are described in Chapter 2.3 and 

summarized in Chapter 4.5.4. A detailed impacts assessment under the cumulative scenario is 
4-222 Description of the Affected Resources and Impact Analysis

provided in Alternative A (Chapter 4.5.2.3). Most mitigation measures under Alternative C would not 

change the extent, severity, or timing of activities in the proposed action; thus, the resultant impacts 

to benthic communities also would not change.

Some of the additional mitigation measures included in Alternative C, while reducing impacts 

to other resources, would have no effect on the associated impacts to benthic communities. The 

seasonal coastal water restrictions for surveying will reduce vessel activities within portions of the 

AOI, resulting in associated reductions in the potential impacts of common benthic community IPFs 

from active acoustic sound sources, trash and debris, seafloor disturbances, drilling discharges, and 

accidental fuel spills. While this mitigation measure would reduce the cumulative impacts from the 

associated IPFs, it would not significantly change the degree of incremental impacts from the 

proposed action. Incremental increase in impacts to benthic communities from active acoustic 

sound sources, trash and debris, seafloor disturbances, drilling discharges, and accidental fuel spills 

would be nominal for Alternative C.

4.5.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative D are the same as for 

Alternative A (Chapter 4.5.2). The additional mitigation measure under Alternative D, which 

includes shutdowns for marine mammals, would not reduce potential active acoustic impacts 

discussed under Alternatives A and C (Chapters 4.5.2.1 and 4.5.4.1) on benthic communities, and 

impacts would therefore remain nominal. This mitigation would not alter the impact levels to benthic 

communities from trash and debris, seafloor disturbance, or drilling discharges, and would remain 

nominal. Under Alternative D, impacts of an accidental fuel spill on benthic communities would be 

as described for Alternatives A and C (Chapters 4.5.2.2 and 4.5.4.2) and would remain nominal. 

4.5.5.1 Impacts of Routine Activities

As evaluated in Alternatives A and C (Chapters 4.5.2.1 and 4.5.4.1), impacts on benthic 

communities were determined to be nominal. The additional mitigation measure included in 

Alternative D would not reduce impacts to benthic communities; therefore, impacts to benthic 

communities would remain nominal. 

4.5.5.2 Impacts of an Accidental Fuel Spill

Impacts from accidental fuel spills on benthic communities are evaluated for Alternative A in 

Chapter 4.5.2.2. Due to the relatively small volume of fuel and the rapid weathering and dissipation 

of the fuel in water, an accidental diesel fuel spill would be expected to result in nominal impacts to 

benthic communities. Area closures and restrictions included in the additional mitigation measures 

of Alternative D would result in restricted vessel activities, further reducing the potential impacts from 

accidental fuel spills on benthic communities; therefore, impacts would be nominal. 
Gulf of Mexico G&G Activities Programmatic EIS 4-223

4.5.5.3 Cumulative Impacts

Impact analyses presented in Chapters 4.5.5.1 and 4.5.5.2 determined that activities 

projected to occur under Alternative D would result in nominal impacts to benthic communities. 

Mitigation measures for the proposed action under Alternative D are described in Chapter 2.4 and 

summarized in Chapter 4.5.5. A detailed impacts assessment under the cumulative scenario is 

provided in Alternative A (Chapter 4.5.2.3). The mitigation measures are the same as described for 

Alternative C, with the addition of shutdown protocols during seismic operations for all marine 

mammals (except bow-riding dolphins). The addition of shutdown protocols for all marine mammals 

except bow-riding dolphins under Alternative D would not change the extent, severity, or timing of 

activities in the proposed action; thus, the resultant impacts to benthic communities also would not 

change. Incremental increase in impacts to benthic communities, as in Alternatives A and C, would 

remain nominal for Alternative D.

4.5.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.5.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative E on benthic communities.

4.5.6.1 Impacts of Routine Activities

4.5.6.1.1 Reduced Level of Activity

As evaluated in Alternatives A and C (Chapters 4.5.2.1 and 4.5.4.1), impacts on benthic 

communities were determined to be nominal. The additional mitigation measures included in 

Alternative E would result in survey line mile reductions but not additional mitigation measures that 

would reduce benthic community impacts from seafloor disturbances or drilling discharges. The 

additional mitigation measure included in Alternative E would reduce acoustic impacts to benthic 

communities from deep-penetration, multi-client surveys and may reduce the amount of trash and 

debris due to the reduction of these surveys; impacts to benthic communities would be nominal. 

4.5.6.1.2 Routine Activities Impact Conclusions

Active acoustic sound sources from seismic activities have not been determined to have 

significant impacts to benthic communities, and impacts are expected to be nominal. Impacts from 

trash and debris, bottom-disturbing activities, and drilling discharges would not be affected by the 

mitigations in Alternative E and would remain nominal. 

4.5.6.2 Impacts of an Accidental Fuel Spill

Impacts from accidental fuel spills on benthic communities are evaluated for Alternative A in 

Chapter 4.5.2.2. Due to the relatively small volume of fuel and the rapid weathering and dissipation 

of the fuel in water, an accidental diesel fuel spill would be expected to result in nominal impacts to 

benthic communities. Area closures and restrictions and seismic activity reductions included in the 

additional mitigation of Alternative E would result in less survey vessel activities, further reducing the 
4-224 Description of the Affected Resources and Impact Analysis

potential impacts from accidental fuel spills on benthic communities; therefore, impacts would still be 

nominal. 

4.5.6.3 Cumulative Impacts

Impact analyses presented in Chapters 4.5.6.1 and 4.5.6.2 determined that activities 

projected to occur under Alternative E would result in nominal impacts to benthic communities, 

depending on the IPF. Mitigation measures for the proposed action under Alternative E are 

described in Chapter 2.5 and summarized in Chapter 4.5.6.1. A detailed impacts assessment 

under the cumulative scenario is provided in Alternative A (Chapter 4.5.2.3). The reduction of deeppenetration, multi-client activities (in line miles) by 10 percent (Alternative E1) or 25 percent 

(Alternative E2) would reduce the extent, severity, and timing of active acoustic sound sources, 

vessel and equipment noise, vessel traffic, aircraft traffic and noise, and trash and debris; therefore, 

impacts for these IPFs would be decreased under Alternative E. Overall, the incremental increase in 

impacts to benthic communities, as in Alternatives A and C, would remain nominal for Alternative E.

4.5.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.5.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative F on benthic communities.

4.5.7.1 Impacts of Routine Activities

4.5.7.1.1 Closure Areas

As evaluated in Alternatives A and C (Chapters 4.5.2.1 and 4.5.4.1), impacts on benthic 

communities were determined to be nominal. Most of the additional mitigation measures included 

in Alternative F would not reduce impacts to benthic communities since much of the diverse and 

abundant areas fall mostly outside the areas considered for closure under this alternative. The 

additional mitigation measures included in Alternative F do not include additional restrictions that 

would change benthic community impacts from seafloor disturbances or drilling discharges. The 

closure areas would reduce active acoustic impacts from airgun surveys to benthic communities in 

those areas, still resulting in nominal impacts. 

4.5.7.1.2 Routine Activities Impact Conclusions

Active acoustic sound sources from seismic activities have not been determined to have 

significant impacts to benthic communities, and impacts are expected to be nominal. Impacts from 

trash and debris, bottom-disturbing activities, and drilling discharges would not be affected by the 

mitigations in Alternative F and would remain nominal. 

4.5.7.2 Impacts of an Accidental Fuel Spill

Impacts from accidental fuel spills on benthic communities are evaluated for Alternative A in 

Chapter 4.5.2.2. Due to the relatively small volume of fuel spilled and the rapid weathering and 
Gulf of Mexico G&G Activities Programmatic EIS 4-225

dissipation qualities of the fuel in water, an accidental diesel fuel spill would be expected to result in 

nominal impacts to benthic communities. Area closures and restrictions included in the additional 

mitigation of Alternative F would result in restricted vessel activities, further reducing the potential 

impacts from accidental fuel spills on benthic communities; therefore, impacts still would be 

nominal. 

4.5.7.3 Cumulative Impacts

Impact analyses presented in Chapters 4.5.7.1 and 4.5.7.2 determined that activities 

projected to occur under Alternative F would result in nominal impacts to benthic communities, 

depending on the IPF. Mitigation measures for the proposed action under Alternative F are 

described in Chapter 2.6 and summarized in Chapter 4.5.7.1. A detailed impacts assessment 

under the cumulative scenario is provided in Alternative A (Chapter 4.5.2.3). Mitigation measures 

under Alternative F are similar to Alternative C, with the addition of area closures in four areas: the 

CPA Closure Area; the EPA Closure Area; the Dry Tortugas Closure Area; and the Flower Gardens 

Closure Area. Most mitigation measures under Alternative F would not change the extent, severity, 

or timing of activities in the proposed action; thus, the resultant impacts to benthic communities also 

would not change. Mitigation measures under Alternative F that would change the timing and extent 

of activities in the proposed action are a seasonal restriction for operation of airguns in Federal and 

State coastal waters from February 1 through May 31, the prohibition of deep-penetration seismic 

airgun surveys within portions of the EPA (Chapter 2.2.2), and the four area closures listed 

previously for seismic airgun surveys. While this mitigation measure would reduce the cumulative 

impacts from the associated IPFs, it would not significantly change the degree of impacts from the 

proposed action. Incremental increase in impacts to benthic communities would be nominal for 

Alternative F.

4.5.8 Impacts – Alternative G (No New Activity Alternative)

The IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.5.2).

4.5.8.1 Impacts of Routine Activities

As evaluated in Alternative A (Chapter 4.5.2.1), impacts on benthic communities were 

determined to be nominal. Under Alternative G, a limited number of VSP and SWD surveys would 

occur and no bottom-disturbing activities are projected (Table 2.7-1). If no new bottom-disturbing 

activities occur under Alternative G, then no impact will occur to the benthic communities from 

bottom disturbance or drilling discharges. However, geophysical surveys using active acoustic 

sound sources will still occur in the near term; therefore, impacts to benthic communities would 

range from no impact to nominal. 

4.5.8.2 Impacts of Accidental Fuel Spill

Impacts from accidental fuel spills on benthic communities are evaluated for Alternative A in 

Chapter 4.5.2.2. Due to the relatively small volume of fuel spilled and the rapid weathering and 
4-226 Description of the Affected Resources and Impact Analysis

dissipation qualities of the fuel in water, an accidental diesel fuel spill would be expected to result in 

nominal impacts to benthic communities. Because Alternative G would not have the involvement of 

vessels, fuel spills would be less likely to occur; therefore, impacts would range from no impact to 

nominal. 

4.5.8.3 Cumulative Impacts

Impact analyses presented in Chapters 4.5.8.1 and 4.5.8.2 determined that activities 

projected to occur under Alternative G would result in nominal to no impact to benthic communities, 

depending on the IPF. Alternative G is described in Chapter 2.7. A detailed impacts assessment 

under the cumulative scenario is provided in Alternative A (Chapter 4.5.2.3). The cease of activity 

for future G&G surveys requiring a permit/authorization from BOEM would not be adding a 

substantial increase to the cumulative impacts. Overall, no impact to nominal incremental 

increases in impacts to benthic communities would be expected for Alternative G.

4.6 MARINE AND COASTAL BIRDS

4.6.1 Description of the Affected Environment

The GOM supports a diverse avifauna, both resident and migratory species, and includes a 

variety of coastal habitats that are important to the ecology of coastal and marine bird species. The 

status, general ecology, general distribution, migratory movements, and abundance of these birds 

are discussed in Appendix E and summarized in the following subsections. Also, information on 

bird conservation regions (BCR) and important bird areas (IBA) is provided in Appendix E. 

Three distinct ecological groups of birds, within 17 families, occur within the AOI: seabirds; 

waterfowl; and shorebirds (refer to Appendix E and Table 4.6-1). Bird species within a family share 

common physical and behavioral characteristics. Because of these commonalities, birds will be 

presented by family rather than individual species, as the potential for exposure to G&G activities will 

be similar for species within a family. Within the AOI, there are three bird species listed under the 

ESA that will be discussed separately. No ESA candidate or species of concern have been 

identified within the AOI.

4.6.1.1 Unlisted Species

Seabirds

Seabirds within the AOI include members from five taxonomic orders (i.e., Charadriiformes, 

Gaviiformes, Pelecaniformes, Podicipediformes, and Procellariiformes) that live in the marine 

environment and feed at sea (Schreiber and Burger, 2002). Some seabirds can be generally 

categorized by the marine zones in which they tend to forage. For example, pelagic seabirds (e.g., 

shearwaters) forage away from the coastal zone and in the open ocean while shorebirds (e.g., 

sandpipers, godwits) forage in coastal waters. However, there are seabirds that have less 

restrictive, wide foraging practices and use both nearshore and pelagic zones (Michel, 2013). 

Modes of prey acquisition include picking from the sea surface, shallow diving below the sea 
Gulf of Mexico G&G Activities Programmatic EIS 4-227

surface, and diving to depths of several meters (Shealer, 2002). Species that dive below the sea 

surface may be exposed to underwater noise produced during G&G surveys. Seabird species from 

the Procellariidae (petrels and shearwaters), Pelecanidae (pelicans) Sulidae (gannets and boobies), 

Phalacrocoracidae (cormorants), and Laridae (gulls and terns) families occur within the AOI and 

regularly dive below the sea surface. Some seabirds (e.g., cormorants) are known to deep dive for 

relatively long durations.

Surveys within the northern GOM (Hess and Ribic, 2000) reported that terns (Sterna spp.), 

storm petrels (Hydrobatidae), shearwaters (Puffinus spp.), and jaegers (Stercorarius spp.) were the 

most frequently sighted seabirds in deepwater areas. Additionally, the distribution and relative 

densities of seabird species within the deepwater areas of the GOM vary temporally (i.e., 

seasonally) and spatially, based on hydrographic features such as Loop Current eddies, the 

presence of Sargassum lines, upwellings, convergence zones, thermal fronts, salinity gradients, and 

areas of high planktonic productivity (Ribic et al., 1997; Hess and Ribic, 2000).

Waterfowl

Waterfowl such as sea ducks (i.e., diving ducks) and dabbling ducks (Order Anseriformes)

feed and rest within coastal (nearshore and inshore) waters outside of their breeding seasons. 

Members of the order Gaviiformes (loons) may also be present in coastal waters. Waterfowl that 

may occur within coastal and inshore waters of the AOI include species within the subfamilies 

Aythyinae (diving ducks) and Merginae (sea ducks) (Sibley, 2000). Diving ducks include the 

Canvasback (Aythya valisineria), Ring-necked Duck (Aythya collaris), scaups (Aythya affinis and 

A. marila), Bufflehead (Bucephala albeola), and Common Goldeneye (Bucephala clangula). Hooded 

Mergansers (Lophodytes cucullatus) are the primary sea duck species that may occur within the 

AOI. Similar to diving seabirds, sea ducks and some diving ducks may be vulnerable to underwater 

noise produced during G&G activities because they dive beneath the water surface in coastal waters 

for feeding. However, most diving ducks and sea ducks are located in bays and estuaries, which are 

outside of the AOI.

Shorebirds

Shorebirds utilize coastal environments for nesting, feeding, resting, and migration stopover. 

The Gulf Coast is of particular significance to beach-nesting birds, species that breed on beaches, 

flats, dunes, bars, barrier islands, and similar nearshore habitats. The northern Gulf Coast, from the 

Mississippi River Delta of Louisiana to the Florida Panhandle, represents 18 percent of the 

southeastern U.S. coastline and supports a disproportionately high number of beach-nesting bird

species. Shorebirds found primarily along the coastline of the AOI include species within four 

families: Charadriidae (plovers); Haematopodidae (oystercatchers); Recurvirostridae (avocets and 

stilts); and Scolopacidae (sandpipers). Fifty-three species of shorebirds regularly occur in the U.S. 

(Brown et al., 2001), with 43 species occurring during migration or wintering periods in the AOI. Six 

shorebird species, i.e., the American Oystercatcher (Haematopus palliates), Snowy Plover 

(Charadrius alexandrines), Wilson’s Plover (Charadrius wilsonia), Willet (Catoptrophorus 

semipalmatus), Killdeer (Charadrius vociferous), and Black-necked Stilt (Himantopus mexicanus), 
4-228 Description of the Affected Resources and Impact Analysis

breed in the GOM (Helmers, 1992). The Lower Mississippi/western Gulf Coast region is rich with a 

variety of shorebird habitats, and the Gulf Coast has some of the most important shorebird habitat in 

North America, particularly the Laguna Madre ecosystem along the south Texas coast (Brown et al., 

2001; Withers, 2002). Resident shorebirds primarily rely on the shorelines adjacent to the AOI for 

their life functions, while some migrants overwinter along shorelines adjacent to the AOI. Some 

shorebird species cross and stop over in the AOI during their annual migration.

4.6.1.2 Listed Species

Under the ESA, there are three threatened species of marine and coastal birds present 

within the AOI: Piping Plover (Charadrius melodus) (50 FR 50726); Roseate Tern (Sterna dougallii) 

(52 FR 42064); and Red Knot (Calidris canutus rufa) (79 FR 73705). Piping Plover and Red Knot 

are shorebirds that are unlikely to come into contact with G&G activities. Roseate Terns are more 

likely to come into contact with G&G activities, as they forage offshore and feed by plunge-diving, 

often submerging completely when diving for fish. Appendix E, Section 6 provides life history 

information of marine and coastal birds occurring in the AOI. While there are additional threatened, 

endangered, or candidate species that occur in the coastal areas of the AOI (e.g., Red-cockaded 

Woodpecker [Picoides borealis], Wood Stork [Mycteria americana], Mississippi Sandhill Crane [Grus 

canadensis pulla], Sprague’s Pipit [Anthus spragueii], interior subpopulation of the Least Tern 

[Sternula antillarum], and Whooping Crane [Grus americana]), they either are not considered marine 

or coastal birds based on their reliance on more terrestrial habitats or they are not documented in 

the AOI. Therefore, these species were not analyzed further because they are not likely to be

affected by G&G activities.

4.6.1.3 Baseline Populations and the Deepwater Horizon Explosion, Oil Spill, and 

Response

At present, the estimates of avian mortality associated with the Exxon Valdez oil spill far 

exceed current estimates of avian mortality associated with the Deepwater Horizon explosion, oil 

spill, and response even though the Deepwater Horizon oil-spill volume/size far exceeds that of the 

Exxon Valdez oil spill. This is because of the nearshore location of the Exxon Valdez oil spill, where 

bird diversity and abundance were high, where oil was released suddenly (impairing cleanup), and 

where oil accumulated. The Final PDARP/PEIS documented large-scale and pervasive impacts to 

birds in the northern GOM because of the Deepwater Horizon oil spill (Deepwater Horizon Natural 

Resource Damage Assessment Trustees, 2016). At least 93 resident and migratory bird species 

across all five Gulf Coast States were exposed to Deepwater Horizon oil in multiple habitats, 

including offshore/open waters, island waterbird colonies, barrier islands, beaches, bays, and 

marshes (early USDOI, FWS [2011a] efforts estimated 102 species).

The quantified impacts summarized above captured only a portion of the overall impact to 

birds. The Deepwater Horizon oil penetrated into marshes, which serve as important bird habitat. A 

study by Tran et al. (2014) reviewed an FWS dataset of 7,229 dead birds to investigate the location 

and species of birds along the Gulf Coast that were most impacted by the spill. The largest 

concentration of birds was found along the coastlines of Louisiana, Alabama, and the Florida 
Gulf of Mexico G&G Activities Programmatic EIS 4-229

Panhandle, and the laughing gull (Larus atricilla) and brown pelican (Pelecanus occidentalis) were 

the species most often mortally impacted by the spill. Although full exposure and mortality of interior 

marsh birds was not estimated, given densities of key species, meaningful injury to marsh birds was 

very likely to have occurred (Deepwater Horizon Natural Resource Damage Assessment Trustees, 

2016). Similarly, island waterbird colonies were occupied by hundreds of thousands of breeding 

birds at the time of the spill. Although some mortality in colonies was included in the numbers stated 

above, the Final PDARP/PEIS recognizes that these methods were inadequate to assess fully the 

magnitude of impacts at these colonies.

Mortality from the Deepwater Horizon explosion, oil spill, and response was sufficient to 

cause a small negative shift in baseline abundances for seabirds. Total seabird mortality seaward of 

25 mi (40 km) from shore due to the Deepwater Horizon explosion, oil spill, and response was 

estimated at 200,000 birds (Haney et al., 2014a). Estimates of breeding population sizes were 

60,000-15,000,000 for four procellariiform (shearwaters and related) species, 9,000 for one 

pelecaniform (pelican and related) species, and 96,000-500,000 for three charadriiform (gulls and 

related) species (Haney et al., 2014a). Total bird mortality landward of 25 mi (40 km) from shore 

was estimated as 600,000 birds using one model and 800,000 birds using another model (Haney 

et al., 2014b). In perspective, in three analyzed species of seabirds, estimated losses due to the 

Deepwater Horizon explosion, oil spill, and response were 12 percent or more of the total population 

estimated present in the northern GOM (Haney et al., 2014b). This new information estimates a 

small negative shift in baseline numbers. Incremental impacts caused by the negative shift in 

baseline numbers were not sufficient to change the conclusions for the impact analysis of a 

proposed action. The shift was extrapolated from the increased mortality due to the Deepwater 

Horizon explosion, oil spill, and response. However, these changes to the baseline did not identify 

any species whose population was likely to be impacted by a proposed action or alternatives.

Recovery (NRDA) data have become available since the analyses by Haney et al. (2014a 

and 2014b). Total nearshore mortality was determined in six recent NRDA final reports on the 

Deepwater Horizon explosion, oil spill, and response as 54,099 to 100,134 waterbirds (USDOI, 

FWS, 2015a-e; Industrial Economics 2015b). Total offshore mortality was determined in one NRDA 

final report on the Deepwater Horizon explosion, oil spill, and response as 2,317 to 3,141 birds 

(Industrial Economics, 2015a).

The ecosystem ramifications of these impacts are not limited to the northern GOM. Many 

birds that occur in the spill-affected region migrate to areas across North, Central, and South 

America, where their impaired performance or reduction in numbers could have radiating effects on 

ecosystems similar to those described above. Two studies (not funded by NRDA) on the Deepwater

Horizon explosion, oil spill, and response have addressed this. Franci et al. (2014) found no 

confirmed impacts of oil on the endocrine status and no evidence of exposure to oil of Northern 

Gannets that migrated to eastern Canada after overwintering in the northern GOM in the winter of 

2010-2011. Seegar et al. (2015) found evidence in fall of 2010 of polycyclic aromatic hydrocarbon 

(PAH) contamination of blood of migrant Tundra Peregrine Falcons that probably were exposed to 

Deepwater Horizon PAHs in oil, but blood of migrant Tundra Peregrine Falcons found later in spring 
4-230 Description of the Affected Resources and Impact Analysis

and fall of 2011 was probably not contaminated with PAHs from Deepwater Horizon oil. Additional 

information pertaining to this resource and NMFS’ determination of the effects of the Deepwater

Horizon explosion, oil spill, and response may be found in the Final PDARP/PEIS (Deepwater 

Horizon Natural Resource Damage Assessment Trustees, 2016).

4.6.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, the IPFs that may impact marine and coastal birds within the AOI 

include (1) active acoustic sound sources (e.g., airguns; non-airgun HRG sources such as highresolution boomers, sparkers, and CHIRP subbottom profilers; SBESs and MBESs; and side-scan 

sonars), (2) vessel and equipment noise, (3) vessel traffic (i.e., physical disturbance to and risk of 

collisions), (4) aircraft traffic and noise (e.g., helicopters, fixed-wing aircraft), (5) trash and debris 

(i.e., ingestion of and entanglement in), and (6) accidental fuel spills. As all G&G survey activities 

are performed using vessels, all activities could impact marine and coastal birds. Active acoustic 

sound sources, including airgun noise and non-airgun HRG (electromechanical) sources, could 

impact marine and coastal birds that may be present in the survey area via sound exposure. Vessel 

traffic and its associated noise, as well as equipment noise, are discussed together as they can 

disrupt marine and coastal birds and displace them from the survey area. The potential for impacts 

from the release of trash and debris to marine and coastal birds is also discussed. The accidental

spill scenario is presented in detail in Chapter 3.3.2 and considers a spill of 1.2 to 7.1 bbl of fuel, 

which has the potential to adversely affect marine and coastal birds.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact level categories. In contrast, the analysis 

of impacts associated with Alternatives B through G are organized by alternative-specific mitigation 

measures and how each of these measures may reduce impact levels.

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For marine and 

coastal birds, the below significance criteria have been used to evaluate the level of impact for each 

IPF.

Nominal impacts to marine and coastal birds would include those where little to no 

measurable impacts to local populations are observed or expected. No mortality or serious injury to 

any individual marine or coastal bird is expected to occur. Nominal impacts are limited to minimal 

short-term behavioral or other low-level impacts on individuals (i.e., small numbers, low severity, and 

short duration). No mortalities or physical injuries are included.
Gulf of Mexico G&G Activities Programmatic EIS 4-231

Minor impacts to marine and coastal birds would include those that are detectable but not 

extensive or severe and that are expected to affect individuals or groups within the AOI. Minor 

impacts include limited short-term displacement of any species from preferred feeding, breeding, or 

nursery grounds or migratory routes (including critical habitat for listed species); short-term 

disruption of behavioral patterns that may adversely affect a marine or coastal bird species; or 

mortality or life-threatening injury of individuals (other than listed species) in small numbers that 

would not adversely affect the population.

Moderate impacts to marine and coastal birds at the population level may be either 

extensive (potentially affecting large numbers of individuals within regions of the AOI) but not severe 

or they may be severe but not extensive. Moderate impacts to marine and coastal birds would 

include limited levels of serious injury or mortality to listed or non-listed species but in low enough 

numbers that the continued viability of the population is not threatened. Moderate impacts also 

would include extended displacement of a coastal bird species from preferred feeding, breeding, or 

nursery grounds or migratory routes (including critical habitat for listed species); extensive damage 

to critical habitat for listed marine and coastal birds; and extensive disruption of behavioral patterns 

that may adversely affect a marine or coastal bird species. The viability or continued existence of 

affected marine and coastal bird populations would not be threatened, although some impacts may 

be irreversible.

Major impacts to marine and coastal birds would be extensive and severe. Major impacts to 

marine and coastal birds would include mortality or life-threatening injury of individuals of a listed 

(endangered/threatened) species or non-listed species, either of which would be in sufficient 

numbers to adversely affect the population. Major impacts to marine and coastal birds also would 

include mortality or permanent (or long-term) displacement of a coastal bird species from preferred 

feeding, breeding, or nesting grounds or migratory routes (including critical habitat for listed species) 

to the extent that the long-term survivability of the species may be adversely affected; extensive, 

long-term damage to critical habitat for marine and coastal birds; and chronic disruption of 

behavioral patterns that may adversely affect a marine or coastal bird species.

4.6.2.1 Impacts of Routine Activities

4.6.2.1.1 Active Acoustic Sound Sources

The primary potential for impact to marine and coastal birds from airguns and active acoustic 

non-airgun HRG sources (i.e., electromechanical) is the birds that dive below the water surface and 

are exposed to underwater noise (Turnpenny and Nedwell, 1994). The listed (i.e., threatened) 

shorebird species, the Piping Plover and Red Knot, are unlikely to come into contact with G&G 

activities. Diving species (e.g., grebes, loons, and some diving ducks, also Roseate Terns) are more 

likely to come into contact with G&G activities because they forage offshore and feed by plungediving, often submerging completely when diving for fish. Species that plunge-dive are at risk of 

exposure to active acoustic sound sources because seismic sources are directive with a main beam 

directed down through water to the seafloor and side lobes that project sound horizontally. The 

sound energy projected horizontally from the array is much less intense than that projected 
4-232 Description of the Affected Resources and Impact Analysis

vertically. In addition, active acoustic sound sources such as side-scan sonar and subbottom 

profilers (electromechanical sources) are highly directive (e.g., downward), with beam widths as 

narrow as a few degrees and with most (except subbottom profilers) operating at frequencies 

>12 kHz; this directivity, frequency of operation, and narrow beam width diminishes the risk to bird 

species, including plunge-diving species. Because of these factors, other species of seabirds, 

waterfowl, and shorebirds would not be affected by active acoustic sound sources and are not 

discussed further for this IPF.

Active acoustic sound sources include airguns and non-airgun HRG (electromechanical) 

sources, which produce similar impacts to seabirds and waterfowl that dive below the water surface, 

such as members of the Procellariidae, Pelecanidae, Sulidae, Phalacrocoracidae, and Laridae 

families. Birds have a relatively restricted hearing range, from a few hundred Hz (roughly 300 Hz) to 

approximately 10 kHz (Dooling and Popper, 2000). However, this hearing range is for airborne 

noise; there are limited data regarding birds’ hearing range for underwater noise, and there is no 

evidence that birds use underwater sound.

Proposed G&G activities include the use of airguns as seismic sources during deeppenetration seismic airgun surveys for oil and gas exploration and for HRG surveys of oil and gas 

leases. Electromechanical sources typically would be used during HRG surveys for renewable 

energy development and sand source evaluation in the marine minerals program, where a highresolution boomer, sparker, or CHIRP subbottom profiler, SBES, MBES, or side-scan sonar is used 

to delineate near surface geologic strata and features. The AUV surveys for oil and gas leases 

include a similar equipment suite. These sources may operate simultaneously with the airguns 

during deep-penetration seismic airgun surveys. The VSP surveys, which utilize airguns as sound 

sources and sensor strings deployed down boreholes, are conducted to support well drilling. The 

VSP survey airgun arrays will generate impulsive sound similar to that of other G&G surveys that 

use airguns.

Active acoustic sound levels are expected to reach 248 dB re 1 μPa at 1 m0-peak for a large 

airgun array (8,000 in3

). Most energy from a large airgun array is produced at frequencies below 

500 Hz (Appendix D). Active acoustic sound levels are expected to reach 228 dB re 1 μPa at 

1 m0-peak for a small airgun (90 in3

). Most energy from a small airgun is produced at frequencies 

below 600 Hz (Appendix D). Electromechanical sources vary in terms of operating frequency and 

sound levels and are expected to range from 195 to 213 dB re 1 μPa at 1 m0-peak (refer to 

Table 3.4-2).

Airgun pulses are directional, with the majority of the sound energy directed towards the 

seafloor and lower sound energy levels projected lateral to the airgun array. Other survey 

equipment produces higher frequencies. Electromechanical sources usually have one or two 

(sometimes three) main operating frequencies. The low-frequency underwater noise generated by 

airguns would fall within the airborne hearing range of birds, as does one type of survey equipment 

(i.e., subbottom profilers), whereas the operating frequency of other types of survey equipment (e.g., 

side-scan sonar and echosounders) and the sound they produce is outside of their airborne hearing 
Gulf of Mexico G&G Activities Programmatic EIS 4-233

range and should be inaudible to birds. Therefore, if birds can hear within the same range for 

underwater noise as their airborne hearing range, the G&G survey activities that could impact diving 

seabirds and waterfowl are deep-penetration seismic airgun surveys, as well as HRG surveys that 

may use airguns.

Some seabirds and waterfowl, including members of the families Laridae, Rhyncopidae, 

Pelecanidae, Fregatidae, and Anatidae, rest on the water surface or make short, shallow dives. 

Other species (e.g., long-tailed duck and loon) dive to deeper depths (up to 60 m [197 ft]) and spend 

more time submerged than on the surface. Because airgun array pulses are directional, with the 

majority of the sound energy directed towards the seafloor and lower sound energy levels lateral to 

the airgun array, only birds that dive (shallow or deep) could come in contact with active acoustic 

sounds. These species may come into contact with the active acoustic sounds from airguns and 

HRG equipment. The short exposure time to deep-diving species if they dive below airgun arrays, 

along with relatively lower lateral sound energy level exposures to airgun arrays if they are near but 

to the side of the apparatus, would result in a nominal impact to diving birds.

Diving seabirds and waterfowl such as members of the families Gaviidae, Phaethontidae, 

Phalacrocoracidae, Sulidae, Hydrobatidae, Procellariidae, Podicipedidae, and Anatidae could be 

susceptible to active acoustic sounds generated from seismic airgun surveys, especially species that 

would probably dive rather than fly away from a vessel (e.g., grebes, loons, and some diving ducks). 

However, seismic pulses are directed downward and, while energy is projected laterally by an array, 

it is much reduced in energy from that directed downward; therefore, there is a much more reduced 

direct impact from lateral exposure. No mortality or injury is anticipated. Impacts would be limited to 

short-term displacement or avoidance. Therefore, the potential impact from the low-frequency noise 

associated with G&G seismic airgun surveys to affect diving birds is nominal. In addition, active 

acoustic electromechanical sound sources such as side-scan sonar and subbottom profilers are 

highly directive, with beam widths as narrow as a few degrees; the ramifications of this directionality 

include a lower risk of high-level exposure to diving birds that may forage close to (but not beneath) 

a seismic vessel.

Investigations into the effects of airguns on seabirds are extremely limited; however, studies 

performed by Stemp (1985) and Lacroix et al. (2003) did not observe any mortality to the several 

species of seabirds exposed to seismic survey noise. These studies did not observe any differences 

in distribution or abundance of the seabird species as a result of seismic survey activity. Based on 

the directionality of the sound generated from seismic airgun arrays, as well as low-frequency 

equipment used for non-airgun HRG surveys and the limited study results available, mortality or lifethreatening injury is not expected and little disruption of behavioral patterns or other non-injurious 

effects is expected, resulting in a nominal direct impact for seabirds that are exposed to HRG sound 

sources. 

As discussed in Appendix E, there are four BCRs within the AOI that include coastal waters 

and are important feeding areas for seabirds and waterfowl. Underwater noise generated from 

active acoustic sound sources (airguns or other survey equipment) would attenuate significantly prior 
4-234 Description of the Affected Resources and Impact Analysis

to reaching nearshore waters. This sound attenuation, or transmission loss, is the reduction in 

sound intensity between the source and another point in the field. In deepwater operations, this 

impulsive sound spreads in all directions (i.e., spherical spreading). In shallow waters (<50 m 

[164 ft]), transmission losses are higher, which results in a smaller potentially affected area 

(Turnpenny and Nedwell, 1994); therefore, most of the underwater noise will attenuate significantly 

prior to reaching coastal BCRs. The sound produced during seismic airgun surveys and non-airgun 

HRG surveys may cause the temporary displacement of seabirds and waterfowl from small portions 

of the BRCs due to the displacement of their prey species during survey activities. If prey species 

exhibit avoidance of the area in which a survey is performed, it is expected to be limited to a very 

small portion of a bird’s foraging range. Therefore, temporary displacement of coastal and marine 

bird species from a portion of their feeding areas during non-migration seasons is possible, resulting 

in nominal indirect impacts from airgun and HRG surveys. However, if seismic airgun survey 

activities and the potential associated temporary displacement of species from a portion of preferred 

feeding areas occurred during bird species migration, then the impact would be considered minor

because these individuals may have a higher energy demand for finding an alternative food source.

As provided in Appendix E, there are several coastal, nearshore, or offshore IBAs, as well 

as 24 NWRs that include coastal habitat within the AOI. The area contained within these IBAs 

continues offshore into open water where G&G surveys could occur. These IBAs and NWRs are 

important foraging grounds for many species of marine and coastal birds. The sound produced 

during seismic airgun surveys and non-airgun HRG surveys may cause an indirect impact on 

seabirds and waterfowl that use these areas if the sound causes their prey species to be temporarily 

displaced from portions of the IBAs and NWRs during survey activities. Depending on the season in 

which a survey takes place, as well as the duration of the survey, this could result in additional 

energetic requirements for the migrating birds to find additional or different locations for foraging. 

However, these IBAs are large (e.g., the Barataria Terrebonne IBA is close to 3 million ac

[1,214,057 ha]) and it is unlikely that bird prey species would be affected by seismic airgun survey 

activities to a level that would affect foraging success. If prey species exhibit avoidance of the area 

in which the survey is performed, it is expected to be limited to a very small portion of a bird’s 

foraging range. Therefore, there is the potential for temporary displacement of marine and coastal 

bird species from a portion of preferred feeding grounds during migration and from locations of noncritical activities during non-migration seasons, resulting in nominal indirect impacts from airgun and 

HRG surveys. However, if airgun and HRG surveys and the potential associated with temporary 

displacement of species from a portion of preferred feeding areas occurred during bird species 

migration, then the impact would be considered minor. 

4.6.2.1.2 Vessel and Equipment Noise and Vessel Traffic

The primary potential direct impacts to marine and coastal birds from vessel traffic and noise 

are from underwater sound generated by vessels and equipment, with secondary direct impacts 

from attraction to vessels and subsequent collision or entanglement. Potential indirect impacts 

include disturbance to nesting or roosting, and disturbance to feeding or modified prey abundance 

(Schwemmer et al., 2011). Under Alternative A, all G&G survey activities are performed from 
Gulf of Mexico G&G Activities Programmatic EIS 4-235

vessels, with the exception of remote sensing conducted via aircraft and satellites; most survey 

activities could impact marine and coastal birds from vessel traffic and the associated vessel and 

equipment noise (Chapter 3.3.1.3). Projected levels of vessel trips for survey and support vessels is 

provided in Table 3.2 7. 

Underwater Noise

The sound generated from individual vessels can contribute to overall ambient noise levels in 

the marine environment on variable spatial scales. Survey vessels would contribute to the overall 

noise environment in the AOI by transmitting noise through air and water. Underwater noise 

produced by vessels is a combination of narrow band (tonal) and broadband sound. Tones typically 

dominate up to 50 Hz, whereas broadband sounds may extend to 100 kHz. According to Southall 

(2005) and Richardson et al. (1995), vessel noise typically falls within the range of 100 to 200 Hz. 

Noise levels decrease quickly with distance from the vessel. The underwater noise generated from 

the survey vessels would decrease prior to reaching the coastline and shore/beach habitats of birds, 

including threatened and endangered species present in the AOI (i.e., Piping Plover, Roseate Tern, 

and Red Knot). Because of the attenuation of underwater noise from survey vessels prior to 

reaching the shore/beach, it is expected that underwater noise would produce nominal impacts to 

bird species, including Piping Plover and Red Knot.

Seabirds and waterfowl that rest on the water surface, skim the water surface, or make 

shallow dives for short durations would not come in contact with underwater noise generated by 

vessels and equipment, or the contact would be for such a short time that it would result in little 

disruption of behavioral patterns or in other non-injurious effects. Therefore, impacts to these 

seabirds and waterfowl from vessel and equipment noise would be nominal. 

Diving seabirds and waterfowl could be susceptible to underwater noise generated from 

survey vessels and equipment. The number of vessels typically involved in a G&G survey can range 

between one and six, depending on the type of survey being performed. This level of vessel activity 

per survey event is not a significant increase in the existing vessel and equipment noise present in 

the GOM, the vessels are typically moving at slow speeds, and noise levels decrease quickly with 

distance. In addition, drilling-related noise associated with the installation of up to one COST well 

and two shallow test wells associated with oil and gas exploration G&G activities is continuous and 

generally at low frequencies (<500 Hz), including infrasonic frequencies (<15 Hz) in at least some 

cases (Richardson et al., 1995). Machinery noise can be continuous or transient and variable in 

intensity. Noise levels vary with the type of drilling rig and the water depth. Drilling-related noise 

from jack-up platforms is continuous and generally of very low frequencies (near 5 Hz). Drillingrelated noises from semisubmersible platforms range in frequency from 10 to 4,000 Hz, with 

estimated sound levels of 154 dB re 1 μPa-m. Source levels for drillships have been reported as 

high as 191 dB re 1 μPa during drilling. Therefore, most underwater noise from drilling operations 

would be expected to be within the hearing range of most diving seabirds and waterfowl. Because 

most of this noise would decrease rapidly with distance from the source, only a small area of the AOI 

would experience vessel and equipment noise and potential associated disruption. Because the 
4-236 Description of the Affected Resources and Impact Analysis

potential for interaction between noise-producing activities and the occurrence of diving seabirds and 

waterfowl individuals or flocks is very low, impacts of underwater noise from survey vessels and 

equipment to diving seabirds and waterfowl are expected to be nominal. 

The four BCRs within the AOI are important feeding areas for seabirds and waterfowl. Most 

of the underwater noise generated from survey vessels would decrease prior to reaching the 

nearshore waters of the BCRs; therefore, impacts to marine and coastal birds using the BCRs are 

expected to be nominal. 

Furthermore, there are five IBAs off the coast of Louisiana and three off the coast of Florida. 

The area contained within these IBAs continues offshore into open water where G&G surveys could 

occur. These IBAs are important foraging grounds for many species of marine and coastal birds. 

There is the potential for the terns and some diving seabirds and waterfowl that use these areas to 

be exposed to survey vessel and equipment noise. However, because of underwater noise 

attenuation with distance, only a very small area of the IBAs would experience vessel and equipment 

noise. Again, the potential for interaction of noise-generating activities and occurrence of waterfowl 

within an IBA would likely be low. Therefore, impacts to seabirds and waterfowl present within 

offshore IBAs from the underwater noise made by survey vessels and equipment are expected to be 

nominal. However, if G&G activities and the associated underwater noise occurred during migration 

season, there would be the potential to affect preferred feeding grounds of these birds from 

disturbance to feeding or modified prey abundance. Migrating waterfowl have higher energy 

demands than non-migratory species, and thus any additional energy expenditure required for 

seeking alternative food sources would impact the health of the bird. Under such circumstances, 

this indirect impact would be considered minor for diving seabirds and waterfowl.

Vessel Attraction

The number of vessels typically involved in a G&G survey can range between one and six, 

depending on the type of survey being performed (i.e., grab sampling, geologic coring, or vibracoring 

surveys require a single vessel; 3D, 4D, and WAZ seismic surveys require 3 to 6 vessels). This 

level of vessel traffic is not a significant increase to existing vessel traffic in nearshore and offshore 

waters of the GOM. In addition, vessels perform surveys at relatively slow speeds (4 to 6 kn [5 to 

7 mph]), which permits marine and coastal birds to easily move out of the way of survey vessels.

The potential for bird strikes on a rig or vessel is not expected to be significant at the 

population level. However, many seabird species, including members of the Procellariidae, 

Pelecanididae, and Laridae families, are attracted to offshore rigs and vessels due to light attraction 

at night (Montevecchi et al., 1999; Wiese et al., 2001; Black, 2005; Montevecchi, 2006). Some birds 

engage in ship-following as a foraging strategy, especially with commercial or recreational fishing 

vessels. In addition, in an open environment like the ocean, objects are easy to detect and birds 

locate vessels easily from long distances and approach to investigate. Bird mortality has been 

documented as a result of light-induced attraction and subsequent collision with vessels at night 

(Black, 2005).
Gulf of Mexico G&G Activities Programmatic EIS 4-237

Historically, BOEM has directed vessels to have down shielded work lighting to minimize the 

potential attraction and collision with birds. If terns or birds within the Procellariidae and 

Pelecanididae families were attracted to the survey vessels or were to dive near a survey vessel, 

there is a very low potential for vessel collision or entanglement because the vessels are moving 

relatively slowly (4 to 6 kn [5 to 7 mph]) and the seismic gear is towed from 1 to 3.5 m (3 to 11.5 ft) 

below the surface. There is no empirical evidence indicating that these types of marine and coastal 

birds could become entangled in seismic survey gear (e.g., hydrophone streamers) in spite of the 

potential for attraction to vessel lighting. Given the low potential for collision or gear entanglement, 

the impacts are expected to result in a nominal direct impact to seabirds.

Shorebirds, including the Piping Plover and Red Knot, are not known to be attracted to 

vessels. However, these birds may fly in a lower altitude pattern during inclement weather 

conditions during trans-GOM migrations, which may increase the potential for a vessel strike. 

Therefore, while the potential for impacts exists, they are expected to be nominal. 

The IBAs are important foraging grounds for many species of marine and coastal birds and 

often support large bird populations. Loons or similar low-flying waterfowl would be susceptible to 

injury due to a collision with a vessel. However, even if seabirds and waterfowl were attracted to the 

survey vessels, there is a very low potential for collision or entanglement with vessels or equipment 

because of the vessels’ slow speed and depth of gear. Given the low potential for collision or gear 

entanglement, impacts are not expected to result in significant mortality or serious injury to bird 

populations, resulting in a nominal direct impact to seabirds and waterfowl within the IBAs from 

vessel attraction.

Disturbance to Nesting or Roosting

There is the potential for impact to marine and coastal birds from disturbance of breeding 

colonies by airborne noise from vessels (including helicopters) and equipment (Turnpenny and 

Nedwell, 1994). Most marine and coastal bird species nest and roost along the shore and on 

coastal islands. Survey vessels for nearshore, non-airgun HRG projects are expected to make daily 

round-trips to their shore base, whereas the larger seismic vessels performing airgun surveys can 

remain offshore for weeks or months and are likely to remain offshore for most of a survey’s 

duration. Seismic vessels may be supported by supply vessels operating from ports along the Gulf 

Coast. For this analysis, two primary ports have been identified that support G&G survey activities 

(Port Fourchon, Louisiana, and the Port of Galveston, Texas), but 48 additional ports have also been 

identified that can support OCS activities (Dismukes, 2011). Additionally, for conducting crew 

changes, helicopters will be used to support seismic survey activities. Projected levels of helicopter 

traffic are provided in Table 3.2-7. 

Vessels/helicopters could cause a disturbance to breeding birds, and possibly decrease 

nesting success, if they come too close to a breeding colony. The G&G surveys would not occur 

close enough to land for vessel traffic to affect marine and coastal bird breeding colonies during 

survey activities. However, survey vessels for nearshore projects typically would make daily round-
4-238 Description of the Affected Resources and Impact Analysis

trips from a shore base to offshore work areas. The expectation is that this daily vessel transit would 

occur at one of the shore bases identified, or at other established ports, which have established 

ingress and egress vessel traffic transiting routes within nearshore areas. Because of this existing 

vessel traffic, it is not anticipated that marine and coastal birds would typically roost in adjacent 

areas. If they do roost nearby the shore base, the addition of G&G-related survey vessels would not 

significantly increase the existing vessel traffic and potential for disruption to the roosting birds. In 

addition, noise generated offshore from the survey vessels and equipment typically would attenuate 

prior to reaching the coastline and the nesting habitats of coastal birds. Birds that have decided to 

roost or nest within hearing range of vessel routes would likely have adapted and not be stressed by 

the noise. Impacts of airborne vessel, helicopter, and equipment noise to nesting or roosting marine 

and coastal birds would be nominal. 

Many shorebirds are ground nesters. As discussed previously, these bird species would not 

nest in areas that would be disturbed by survey vessels transiting from port to offshore or coastal 

locations; therefore, there would be no impact to the nesting of these particular shorebird species.

There are four BCRs within the AOI that include coastal waters. However, G&G surveys 

would not occur close enough to land to affect marine and coastal bird breeding colonies during 

survey activities. In addition, the potential daily transits for survey vessels would occur at 

established ports that have existing vessel traffic. The addition of G&G-related survey vessels would 

not significantly increase the vessel traffic in these areas. Therefore, impacts of vessel and 

equipment noise to nesting or roosting marine and coastal birds in the BCRs from G&G activities 

would be nominal. 

The area contained within the eight IBAs continues offshore into open water where G&G 

survey activities could occur. These IBAs include important foraging grounds for many species of 

marine and coastal birds; however, the coastal areas of the IBAs where nesting and roosting take 

place would not experience the same potential impacts from vessel traffic as offshore areas. 

Therefore, the impact of vessel and equipment noise to nesting or roosting marine and coastal birds 

within IBAs would be nominal. However, if a G&G survey were to take place within an IBA during 

offshore foraging activities, the impact from vessel and equipment noise in these sensitive areas 

would be of short duration and would be minor. 

Disturbance to Feeding or Modified Prey Abundance

Marine and coastal birds have specialized feeding habitat requirements (Kushland et al., 

2002). Survey vessel and equipment noise could cause pelagic bird species, including members of 

the families Laridae, Stercorariidae, Pelecanidae, Phaethontidae, Sulidae, Fregatidae, Hydrobatidae, 

and Procellariidae, to be disturbed, forcing relocation to alternative feeding areas. Alternative areas 

used as a result of this localized, temporary displacement and disruption of feeding may not provide 

food sources (prey) or habitat requirements similar to that of the original (preferred) habitat; this 

could result in additional energy expenditures by the birds and diminished foraging efficiency. 

However, it is expected that, if these species temporarily moved out of impacted areas, the area 
Gulf of Mexico G&G Activities Programmatic EIS 4-239

would be limited to a very small portion of a bird’s foraging range. It would be unlikely that this 

temporary relocation would affect foraging success or result in long-term effects. Impacts to pelagic 

birds from disturbance associated with vessel and equipment noise would be nominal. 

Many marine and coastal birds, as well as terrestrial birds, use the Mississippi Flyway, and 

many terrestrial birds migrating to the tropics take a shortcut across the GOM (Appendix E). Marine 

and coastal birds have specialized habitat requirements for nesting and/or feeding, and IBAs contain 

these specialized habitats (Kushland et al., 2002). During their annual migrations, several marine 

and coastal birds have very specific coastal stopover locations for species-specific foraging to 

accumulate fat reserves (Brown et al., 2001; McWilliams and Karasov, 2005). Noise produced from 

survey vessels may result in indirect impacts to marine and coastal birds by impacting prey 

abundance and distribution within stopover locations. An alteration of prey abundance and 

distribution will result in additional energy requirements (increased foraging effort) for migrating 

birds. However, it is unlikely that bird prey species would be affected by survey vessels to a level 

that would affect foraging success. As noted previously, surveys would not take place within coastal 

nearshore areas or bays. If prey species exhibit avoidance of the area in which a survey is 

performed, it is expected to be limited to a very small portion of a bird’s foraging range and for a 

limited time. Therefore, there is the potential for temporary displacement of marine and coastal bird 

species from a portion of preferred feeding grounds during migration and from location of non-critical 

activities during non-migration seasons, resulting in nominal impacts. 

4.6.2.1.3 Aircraft Traffic and Noise

Aircraft traffic and noise would result from remote-sensing surveys (aeromagnetic surveys) 

and helicopter support during drilling of COST wells and shallow test wells (Chapter 3.2.1), and 

support and service during deep-penetration seismic airgun surveys. BOEM anticipates that one 

aeromagnetic survey may be conducted in the AOI during the 10-year time period covered by this

Programmatic EIS (Chapter 3.2.1.2). Helicopter flights will be used to conduct crew changes for 

larger seismic vessels; the number of anticipated transits is provided in Table 3.2-7 and discussed in 

Chapter 3.3.1.4. 

The aeromagnetic surveys would be conducted by fixed-wing aircraft flying at speeds of 

approximately 135 kn (155 mph) (Reeves, 2005). Most offshore aeromagnetic surveys are flown at 

altitudes of 61 to 152 m (200 to 500 ft). In addition, helicopters are a potential source of aircraft 

noise during the drilling of COST and shallow test wells, and for crew change out during extended 

seismic surveys. It is expected that up to one COST wells and two shallow test wells would be 

drilled in the planning areas during the time period of this Programmatic EIS. Helicopters would be 

used to conduct crew changes in support of airgun survey activities (Table 3.2-7). Potential direct 

impacts to marine and coastal birds from aircraft traffic include noise disturbance and collision.

Noises generated by project-related survey aircraft that are directly relevant to birds include 

airborne sounds from passing aircraft for birds on the sea surface and birds in flight. Helicopters and 

fixed-wing aircraft generate noise from their engines, airframes, and propellers. The dominant tones 
4-240 Description of the Affected Resources and Impact Analysis

for both types of aircraft generally are below 500 Hz (Richardson et al., 1995) and within the airborne 

auditory range of birds. The amount of aircraft noise entering the water depends on aircraft altitude, 

the aspect (direction and angle) of the aircraft relative to the receiver, and sea surface conditions. 

The level and frequency of sounds propagating through the water column are affected by water 

depth and seafloor type (Richardson et al., 1995). Because of the expected airspeed (135 kn

[155 mph]), noise generated by survey aircraft is expected to be brief in duration, and birds may 

return to pre-disturbance behavior within 5 minutes of the overflight (Komenda Zehnder et al., 2003); 

however, birds can be disturbed up to 1 km (0.6 mi) away from an aircraft (Efroymson et al., 2000).

The physical presence of low-flying aircraft can disturb marine and coastal birds, including 

those on the sea surface and those in flight. Behavioral responses to flying aircraft include flushing 

from the sea surface into flight or rapid changes in flight speed or direction. These behavioral 

responses can result in collision with the survey aircraft. However, Efroymson et al. (2000) reported 

that the potential for bird collision decreases for aircraft flying at speeds >81 kn (93 mph). In 

addition, the FAA recommends that aircraft fly at a minimum altitude of 610 m (2,000 ft) or more 

above ground over noise sensitive areas such as National Parks, NWRs, Waterfowl Production 

Areas, and Wilderness Areas (USDOT, FAA, 2004).

Considering the relatively low number of planned aeromagnetic surveys (1), COST wells (1), 

and shallow test wells (2), as well as helicopter traffic for crew change-out and the short exposure 

periods expected to aircraft-related noise, physical disturbance, and collisions, it is expected that 

potential impacts from this activity would range from nominal during the non-migration season to 

minor during the migration season (because of the greater numbers and higher densities of 

migrants crossing the GOM).

4.6.2.1.4 Trash and Debris

Plastic is found in the surface waters of all the world’s oceans and poses a potential hazard 

to most marine life, including seabirds, through entanglement and ingestion (Laist, 1987). The 

ingestion of plastic by marine and coastal birds can cause obstruction and ulceration of the 

gastrointestinal tract, which can result in mortality. In addition, accumulation of plastic in seabirds 

has been shown to be correlated with the body burden of polychlorinated biphenyls (PCBs), which 

can cause lowered steroid hormone levels and result in delayed ovulation and other reproductive 

problems (Pierce et al., 2004).

The G&G survey activities generate trash comprised of paper, plastic, wood, glass, and 

metal that may be accidentally lost overboard. Over the last several years, companies operating 

offshore have developed and implemented trash and debris reduction and improved handling 

practices to reduce the amount of offshore trash that could be introduced into the marine 

environment. These changes have resulted in a reduction of accidental loss of trash and debris. In

addition, all authorizations for shipboard surveys would include guidance for marine debris 

awareness (NTL 2015-BSEE-G03) (Appendix B).
Gulf of Mexico G&G Activities Programmatic EIS 4-241

All survey vessels performing work within U.S. jurisdictional waters are required to comply 

with Federal regulations and implement MARPOL 73/78. Within MARPOL Annex V, “Regulations for 

the Control of Pollution by Garbage from Ships,” as implemented by 33 CFR part 151, are 

regulations designed to protect the marine environment from various types of garbage generated 

on-board vessels. Therefore, the amount of trash and debris dumped offshore would be expected to 

be minimal, as only accidental loss of trash and debris is anticipated, some of which would float on 

the water surface. Therefore, impacts on marine and coastal birds from trash and debris generated 

by survey vessels or sampling, shallow or COST well drilling, and other G&G-related activities would 

be nominal. 

4.6.2.1.5 Routine Activities Impact Conclusions

There is the potential for temporary displacement of marine and coastal bird species from a 

portion of preferred feeding grounds during migration and from locations of non-critical activities 

during non-migration seasons, resulting in nominal indirect impacts from airgun and HRG surveys. 

However, if airgun and HRG surveys and the potential associated temporary displacement of 

species from a portion of the preferred feeding areas occurred during bird species migration, then 

the impact would be considered minor. Impacts from vessel and equipment noise, vessel traffic, 

and aircraft traffic and noise are expected to be nominal in most circumstances, but if spatial and 

temporal conditions of proposed activities coincide with biologically important areas or activities, 

impacts could be minor. Impacts from trash and debris would be nominal. 

4.6.2.2 Impacts of an Accidental Fuel Spill

An accidental event could result in the release of diesel or other fuel by a survey vessel. 

Based on USCG spill statistics, a spill scenario was developed in Chapter 3.3.2.1; this scenario

finds that a diesel spill volume of 1.2 to 7.1 bbl is reasonably foreseeable. Diesel and other fuel 

used for operation of survey vessels is light and would float on the water surface, disperse, and 

weather. Volatile components of the fuel would quickly evaporate. An accidental fuel spill could 

occur offshore or nearshore, and the marine and coastal bird species affected and the type of effect 

would vary depending on the location of the fuel spill (Wiese and Jones, 2001; Castege et al., 2007). 

If the accident occurred in nearshore waters, including the BCRs, shorebirds, waterfowl, and coastal 

seabirds such as members of the Laridae, Rhyncopidae, Gaviidae, Pelecanidae, Phalacrocoracidae, 

Fregatidae, Ardeidae, Rallidae, and Podicipedidae families, could be impacted directly or indirectly. 

Direct impacts would include physical oiling of individuals. The potential effects of oil spills on 

coastal and marine birds include tissue and organ damage from oil ingested and inhaled during 

feeding and grooming, as well as interference with food detection, predator avoidance, homing of 

migratory species, disease resistance, growth rates, reproduction, and respiration. Indirect effects 

could include oiling of nesting and foraging habitats, as well as displacement of affected birds to 

secondary locations.

The likelihood of a vessel collision is quite low and the potential for a resultant fuel spill even 

lower (Chapter 3.3.2). Although unlikely, a small spill (1.2 to 7.1 bbl) could result in the release of 

diesel or other fuel. This areal coverage of the spill would represent only a very small portion of the 
4-242 Description of the Affected Resources and Impact Analysis

AOI. Therefore, an accidental fuel spill within nearshore waters would not be expected to result in 

significant impacts to coastal and marine birds. Direct impacts to birds from accidents are unlikely; 

however, if an accident occurs, it is possible that there could be indirect impacts on prey species 

(food supply). Impacts to shorebirds, waterfowl, and seabird species would range from nominal to 

minor depending on timing and location of the spill. A small spill of 1.2 to 7.1 bbl would quickly 

dissipate through spreading, evaporation, etc. It is unlikely that more than a small number of birds 

would come into contact with the spill regardless of the season. This would not lead to population 

level effects for non-listed species. Populations of listed species are already in peril, so an 

accidental fuel spill affecting any individuals of these species or their food supply would result in 

moderate impacts. 

If a fuel spill event occurred in offshore waters, diesel and other fuel would float on the water 

surface for several days. Dispersal, weathering, and evaporation would rapidly reduce the amount 

of fuel remaining on the sea surface. There is a potential for oceanic and pelagic seabirds, such as 

members of the Sulidae, Phaethontidae, Hydrobatidae, and Procellariidae families, to be directly and 

indirectly affected by a spill. Direct impacts could include oiling of plumage and ingestion of oil (from 

preening) or displacement from important feeding or nesting habitat. Indirect impacts could include 

oiling of prey and prey habitats. The likelihood of a vessel collision occurring is quite low, and the 

potential for a resultant fuel spill even lower. Because of the anticipated small fuel spill size (1.2 to 

7.1 bbl), the area of impact would be relatively small. Impacts to oceanic and pelagic birds from a 

fuel spill incident involving survey vessels within offshore waters would range from nominal to 

minor. 

Within IBAs, there is expected to be a greater presence of marine and coastal birds. If a 

diesel spill were to occur within or adjacent to an IBA, there would be a greater potential for impact 

to oceanic and pelagic birds. Impacts from accidental spill incidents involving survey vessels within 

IBAs would range from nominal to minor, depending on spill timing and location.

4.6.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for marine and coastal birds are compared with the 

IPFs from each of the cumulative scenario components in order to focus this cumulative analysis on 

those activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The 

G&G activity IPFs that are included in the cumulative assessment are the same as those assessed 

under routine activities and accidental events. The following analysis evaluates the incremental 

increase by IPF and provides a conclusion of the cumulative incremental increase within the AOI.

The G&G activities have been ongoing in the GOM for at least the past 30 years and it is 

reasonable to assume they will continue into the future; however, for the purpose of this 

Programmatic EIS, the cumulative analysis assesses a 10-year timeframe to coincide with the 
Gulf of Mexico G&G Activities Programmatic EIS 4-243

proposed action because it is not expected that G&G activities will have lasting effects or extend 

beyond the 10-year timeframe of this Programmatic EIS.

4.6.2.3.1 Noise

Active Acoustic Sound Sources

The primary potential for impact to marine and coastal birds from airguns and other active 

acoustic non-airgun HRG sources (electromechanical) is to seabirds and waterfowl that dive below 

the water surface and are exposed to underwater noise (Turnpenny and Nedwell, 1994). Sound 

sources from the cumulative scenario are generated by activities as part of commercial and 

recreational fishing, military activities, scientific research, and cumulative vessel activity levels. 

Noise generated under this component is from echosounders, subbottom profilers, side-scan sonars, 

and naturally occurring noise from biological or physical processes. The active acoustic sound 

sources under the proposed action (airgun and electromechanical sound sourced) are described in 

Chapter 3.3.1.1. At present, three of the Gulf Coast Sates (i.e., Alabama, Louisiana, and Texas) 

produce oil and gas in State waters, with Louisiana and Texas having the highest production rates 

(Table 3.4-6). Overall, Chapter 4.6.2.1 determined that there would be increases in ambient noise 

levels within specific portions of the AOI during G&G operations but nominal to minor impacts to 

marine and coastal birds from the proposed activities depending on the location and timing of the 

activities. State waters are outside the permitting jurisdiction of BOEM; therefore, G&G activities 

under the proposed action will not be permitted to occur within State waters, which will reduce the 

cumulative impact of the proposed action.

Active acoustic sound sources, including airguns and non-airgun HRG sources 

(electromechanical), projected under the proposed action are shown in Table 3.2-1, which provides 

the number of surveys and line miles for all acoustic G&G activities. Under the cumulative scenario, 

impacts from the proposed action would be not result from direct ensonification but from noise from 

G&G activities (airgun and electromechanical sound sources used during survey activities) in deeper 

waters that propagates into shallower State waters. Therefore, the proposed action would produce a 

nominal incremental increase in impacts to marine and coastal birds from active acoustic sound 

sources under the cumulative scenario.

Vessel and Equipment Noise

The potential direct impacts to marine and coastal birds from vessel and equipment noise 

are from both above- and below-water sound generated by vessels and equipment, while potential 

indirect impacts include disturbance to feeding or modified prey abundance (Schwemmer et al., 

2011). Underwater noise from vessel traffic and other anthropogenic sources within the AOI is 

increasing, and vessel traffic is a major contributor to ambient noise levels, particularly in the lowfrequency bands. According to Southall (2005), vessel noise typically falls within the range of 100 to 

200 Hz, and noise levels dissipate quickly with distance from the vessel; therefore, based on the 

airborne hearing range of birds (refer to Chapter 4.6.2.1), some vessel noise would be below the 

hearing range of birds and should be inaudible to them.
4-244 Description of the Affected Resources and Impact Analysis

Survey vessel and equipment noise could cause pelagic seabird species to be disturbed, 

forcing relocation to alternative areas. Alternative areas used as a result of this localized, temporary 

displacement and disruption of feeding may not provide food sources (prey) or habitat requirements 

similar to that of the original preferred habitat; this could result in additional energetic requirements 

of the birds due to diminished foraging efficiency.

Another potential for noise impacts to birds under the cumulative scenario would be from 

offshore platform decommissioning. Offshore facility decommissioning, including platform and 

caisson removal, typically use one of two primary methods to sever structures attached to the 

seafloor: mechanical severance or explosive severance (the latter results in a shockwave and 

release of acoustic energy). Explosive charges generally are placed inside the platform legs or 

conductors 4.6 to 7.6 m (15 to 25 ft) below the seafloor. Historical structure-removal permit 

applications for the GOM between 2002 and 2013 are summarized in Table 3.4 2. 

Furthermore, marine and coastal birds have specialized habitat requirements for nesting 

and/or feeding, and IBAs contain these specialized habitats (Kushland et al., 2002). During their 

annual migrations, several marine and coastal birds have very specific stopover locations for species 

specific foraging to accumulate fat reserves (Brown et al., 2001; McWilliams and Karasov, 2005). 

Noise produced from survey vessels may result in indirect impacts to marine and coastal birds by 

directly impacting prey abundance and distribution. An alteration of prey abundance and distribution 

will result in additional energy expenditure (increased foraging time) for the migrating birds.

Table 3.4-2 provides the number of support vessel trips anticipated under the cumulative 

scenario within the oil and gas program component and will range from 828 to 1,096,000 trips for the 

10-year span of the cumulative scenario. Survey vessels required for the proposed action will range 

from one to six vessels dependent upon survey type. Table 3.2-7 provides the projected number of 

vessels required by survey type for the proposed action. The amount of vessel and equipment noise 

generated by the proposed activities is very small when compared with what exists under the OCS 

Program component and because underwater noise from vessels conducting G&G activities as part 

of the proposed action were determined to cause nominal or minor impacts to marine and coastal 

birds, depending on the location and timing (season) (Chapter 4.6.2.1).

Overall, underwater noise from vessel traffic quickly dissipates and becomes inaudible to 

bird species. It is expected that, if feeding seabirds are temporarily displaced from preferred areas, 

it would be limited to a very small portion of a bird’s foraging range and it is unlikely to affect foraging 

success. Additionally, if prey species abundance and distribution is altered by underwater noise 

from vessel traffic, it is unlikely to be affected at a level that would affect foraging success. If prey 

species exhibit avoidance of the area in which a survey is performed, it is expected to be limited to a 

very small portion of a bird’s foraging range and for a limited time. 

The proposed activity represents a short-term, incremental increase in the overall level of 

noise generated by vessels and equipment within the AOI; therefore, the impacts associated with the 
Gulf of Mexico G&G Activities Programmatic EIS 4-245

proposed action would result in a nominal incremental increase in noise impacts to marine and 

coastal birds under the cumulative scenario.

Aircraft Noise

The potential direct impacts to marine and coastal birds from aircraft noise include 

disturbance to feeding, nesting, or roosting. Detailed information on noise generated by aircraft and 

its relevance to bird impacts is provided in Chapter 4.2.6.1. BOEM anticipates that one 

aeromagnetic survey may be conducted in the AOI during the time period covered by this

Programmatic EIS. In addition, helicopters are a potential source of aircraft noise for crew change 

out during extended seismic surveys (Chapter 3.3.1.4). It is expected that that up to one COST 

wells and two shallow test wells would be drilled in the planning areas during the time period of this

Programmatic EIS. Noise from G&G operations would be survey or activity based, occurring on a 

transient and intermittent basis over the period of interest. Aircraft noise from G&G activities was 

determined to cause a nominal or minor impact to marine and coastal birds, depending on the 

location and timing (season) of the G&G activities (Chapter 4.6.2.1).

The proposed action would cause an increase in the overall level of aircraft noise within the 

AOI under the Offshore Developments component, resulting in increases in ambient noise levels

within specific portions of the AOI during G&G operations. However, the incremental increase is not 

significant when compared with the level of aircraft traffic that exists under the cumulative scenario. 

Therefore, it is expected that impacts associated with aircraft noise in the AOI will be nominal, and 

there would be a nominal incremental increase in aircraft traffic and noise impact to marine and 

coastal birds from the proposed action under the cumulative scenario.

4.6.2.3.2 Vessel and Aircraft Traffic

The potential impacts to marine and coastal birds from vessel traffic are from attraction to 

vessels and subsequent collision or entanglement and disturbance to nesting, roosting, and foraging 

sites (Schwemmer et al., 2011). Many seabird species are attracted to offshore rigs and vessels, 

but shorebirds, including the Piping Plover and Red Knot, are not known to be attracted to vessels; 

however, they may fly in a lower altitude pattern in response to inclement weather conditions during 

trans-GOM migrations, which may increase the potential for a vessel strike. Birds are attracted to 

vessel lighting and some species engage in ship-following. No empirical evidence exists indicating 

impacts to birds from seismic survey gear (e.g., airgun arrays and hydrophone streamers). Impacts 

from vessel traffic resulting from the proposed action are discussed in Chapter 4.6.2.1 and range 

from nominal to minor, depending on the location and timing (season) of the activities.

Vessel and aircraft traffic associated with OCS Program activities will originate from selected 

ports in the CPA and WPA, and will cross State waters to reach fields within the OCS. This 

discussion of vessel traffic draws from the discussion on vessel noise above, with respect to 

projected and historical OCS Program vessel traffic levels and other cumulative vessel traffic levels. 

Table 3.2-7 provides the number of estimated vessels required by survey type and by program area 

for the proposed action, and includes 19,689 trips for support vessels and 1,008 trips for survey 
4-246 Description of the Affected Resources and Impact Analysis

vessels. For cumulative vessel traffic, Table 3.4-2 provides a summary of projected support vessel 

operations anticipated for the oil and gas program, and estimates that support vessel trips will range 

from 828,000 to 1,096,000 trips for the 10-year span of the cumulative scenario. Tables 3.4-7 and 

3.4-8 provide vessel trip data for all vessels in the GOM. Exact numbers of cumulative vessel traffic 

associated with renewable energy- and marine mineral-related support activities are not known, but 

they are expected to be relatively small and spatially and temporally limited. Other sources of 

vessels associated with the cumulative scenario include those associated with oil and gas activities 

in State waters, drilling and production activities (within both State waters and OCS waters), 

commercial shipping, commercial and recreational fishing, military activities, scientific research, 

offshore construction activities, maintenance dredging of Federal channels and dredged material 

disposal, coastal restoration programs, and Mississippi River hydromodification and subsidence 

issues (Table 3.4-1).

The cumulative scenario could include the presence of structures in the AOI, some for short 

durations (e.g., drill rigs and LNG vessels offloading cargo) and others that may be long-term or 

permanent (e.g., platform), to which members of these marine bird families would be attracted. 

Table 3.4-2 provides a summary of oil and gas exploration and development activities in the GOM 

under the cumulative scenario showing that 359 to 507 production structures are anticipated to be 

installed during the 10-year time period analyzed in this Programmatic EIS. In contrast, during the 

same time period, it is anticipated that there would be drilling of one COST well and up to two 

shallow test wells with associated short-term structures under the proposed action scenario. 

Overall, G&G activities would produce a nominal incremental increase in impact from vessel traffic 

to marine and coastal birds under the cumulative scenario.

The potential direct impact to marine and coastal birds from aircraft traffic is bird strikes. 

Helicopter traffic would result from oil and gas exploration activities in the OCS Program portion of 

the cumulative scenario as they often are used to transport personnel to offshore oil rigs. A 

summary of aircraft operations (helicopter operations) in support of oil and gas exploration and 

development activities is provided in Table 3.2-7, showing that 7,497 helicopter flights are 

anticipated during the 10-year period of analysis.

Aircraft traffic would result from remote-sensing surveys, including aeromagnetic surveys, 

and helicopter traffic supporting G&G surveys (Chapter 3.3.1.4). Under the proposed action, aircraft 

traffic would increase as a result of G&G activities (e.g., aeromagnetic survey activities and oil and 

gas support activities), but the increase relative to the anticipated aircraft traffic under the cumulative 

scenario (Table 3.4-2) is small. Additional aircraft traffic from G&G operations under the proposed 

action would not represent a significant increase to existing aircraft traffic from cumulative operations 

within the AOI under the cumulative scenario. Therefore, G&G activities would produce a nominal

incremental increase in impact from aircraft traffic to marine and coastal birds under the cumulative 

scenario.
Gulf of Mexico G&G Activities Programmatic EIS 4-247

4.6.2.3.3 Trash and Debris 

Survey activities associated with the proposed action generate trash comprised of paper, 

plastic, wood, glass, and metal (Chapter 3.3.1.7) that may be accidentally lost overboard. As 

discussed in Chapter 4.6.2.1, impacts from trash and debris on marine and coastal birds, as 

generated by the proposed action, would be nominal because all activities would be required to 

follow existing requirements for marine debris and elimination, such as NTL 2015-BSEE-G03 and 

MARPOL 73/78. Despite these regulations, unknown quantities of plastics and other materials are 

discarded and lost in the marine environment, and so remain a threat to individual birds (Azzarello 

and van Vleet, 1987). The amount of trash and debris dumped offshore from OCS G&G activities 

would be minimal as only accidental loss of trash and debris is anticipated, some of which could float 

on the water surface. Therefore, impacts from trash and debris on marine and coastal birds, as 

generated by the proposed action, would result in a nominal incremental increase in impacts to 

marine and coastal birds under the cumulative scenario.

4.6.2.3.4 Cumulative Impact Conclusions

Overall, proposed activities associated with the proposed action would increase levels of 

noise and vessel and aircraft traffic within the AOI, resulting in sporadic increases in ambient noise 

levels during proposed G&G operations. Sources of noise associated with the cumulative scenario 

that may affect marine and coastal birds of the AOI include active acoustic sound, vessel and 

equipment, and aircraft. Other IPFs that may affect sea turtles include the presence of vessel and 

aircraft traffic, trash and debris, and accidental fuel spills. Many of these IPFs may occur 

simultaneously during some projected operations under the OCS Program. For example, during 

deep-penetration seismic, shallow-penetration seismic, and HRG survey operations, IPFs such 

active acoustic sound, vessel and equipment noise, vessel traffic, and aircraft noise and traffic 

(during some survey activities) will occur together.

The spatial distribution of activities projected under the proposed action during the project 

period are most concentrated within deepwater regions of the CPA and WPA, and less concentrated 

within continental shelf waters (Table 3.2-1). Very little activity is projected to occur within the EPA. 

Temporally, activity levels associated with the proposed action vary by activity type and year (Tables

3.2-1 through 3.2-5).

When compared with historic levels of activities within the GOM, proposed activities do not 

represent a significant incremental increase to activities under the cumulative scenario. Surveys 

utilizing active acoustic sound sources have occurred within the GOM for decades, including within 

State waters and continental shelf and deepwater regions of the OCS. Commercial, military, and 

recreational vessel traffic has also occurred in the GOM, including the AOI for many years. In some 

cases, such as large commercial vessels, traffic is and has been more concentrated along Gulfwide 

shipping lanes that funnel into major coastal ports. Commercial and recreational fishing vessels 

have utilized broad areas of the northern GOM, but primarily on the continental shelf and shelf edge. 

It is assumed that military vessels have traveled through all areas of the GOM. The projected fuel 
4-248 Description of the Affected Resources and Impact Analysis

spill associated with the proposed activity is relatively small and when compared with historic spill 

events, the contribution of this projected spill is nominal. 

In conclusion, activities associated with Alternative A are more concentrated within 

deepwater regions of the CPA and WPA and less concentrated on the continental shelf of these 

planning areas. In addition, projected levels of activities will vary over the 10-year project period. 

When compared with historic, present, and future activities, including similar non-OCS Program 

activities (Figure 3.4-1), the cumulative effects of all IPFs to marine and coastal birds within the AOI 

over the 10-year period would result in a nominal incremental increase in impacts.

4.6.2.3.5 Accidental Fuel Spills

With the use of AIS on large sea-going vessels, radar, and licensing of vessel captains, the 

likelihood of a vessel collision is quite low, and the potential for a resultant fuel spill is even lower. 

Spills would more likely result during material transfer or maintenance activities. Whether from 

vessel collision or maintenance activity, the possibility of vessel-related fuel spills involved in the 

cumulative activities scenario is considered remote.

For the proposed action, a fuel spill scenario was evaluated (Chapter 3.3.2) and the 

likelihood of a fuel spill occurring during G&G surveys or other G&G activities is considered remote 

(Chapter 4.6.2.2); impacts associated with a small diesel fuel spill are expected to be variable. 

Impacts to shorebirds, waterfowl, and coastal seabirds would range from nominal to minor. The 

populations of listed species already are in peril; therefore, any direct and indirect impacts to these 

species from an accidental fuel spill would result in a moderate impact.

The proposed action would slightly increase vessel traffic activity in the AOI and the risk of 

collision and a resultant fuel spill. The G&G vessel activities under the proposed action would 

produce a nominal incremental increase in impacts to marine and coastal birds from a collisionbased fuel spill under the cumulative scenario.

4.6.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.6.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative B on marine and coastal birds.

4.6.3.1 Impacts of Routine Activities

Additional mitigation measures under Alternative B that would not change the extent, 

severity, or timing of G&G activities, and therefore related impacts to marine and coastal birds, 

include the expansion of NTL 2012-JOINT-G02 (inclusion of manatees and the NTL shall apply to all 

deep-penetration seismic airgun surveys in the GOM regardless of water depth) and the expanded 

use of PAM. As such, those mitigation measures will not be addressed in the following discussion.
Gulf of Mexico G&G Activities Programmatic EIS 4-249

4.6.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to April 30)

Alternative B would include a seasonal restriction in Federal coastal waters of the GOM 

shoreward of the 20-m (66-ft) isobath between January 1 and April 30. No airgun surveys would be 

authorized within the closure area during this time.

The additional seasonal restriction for Federal coastal waters under Alternative B would 

change the timing of seismic airgun surveys in certain areas. As discussed in Chapter 4.6.2.1, 

impacts of active acoustic sound sources on marine and coastal birds are expected to be nominal to 

minor depending on the location. A change in survey timing in the additional closure area would 

temporarily alter the impacts of active acoustic noise from seismic airgun surveys on marine and 

coastal birds; however, a change in the timing of airgun surveys does not reduce the overall impact 

of active acoustic sound sources, and impacts are still expected to range from nominal to minor

because the additional closure is probably not of sufficient length to significantly reduce impact 

levels.

The additional seasonal restriction for Federal coastal waters under Alternative B would 

reduce the vessel traffic and associated vessel and equipment noise from seismic airgun surveys in 

the coastal areas during certain times of the year compared with Alternative A. As discussed in 

Chapter 4.6.2.1, impacts of vessel traffic and noise on marine and coastal birds are expected to be 

nominal to minor depending on the location. A change in survey timing in the closure area could 

reduce the exposure to vessel traffic and noise from seismic airgun surveys on some groups of 

marine and coastal birds (e.g., shorebirds), as these surveys would not occur within coastal waters 

between January 1 and April 30. However, the impacts to marine and coastal birds from vessel 

traffic and noise would still be expected to be nominal to minor because the additional closure is 

probably not of sufficient length to significantly reduce impact levels.

The additional seasonal restriction for coastal areas under Alternative B would not affect the 

potential for one aeromagnetic survey to occur or for the drilling of two shallow test wells and a 

COST well to occur. Therefore, it is expected that the impacts from aircraft traffic and noise would 

remain unchanged (nominal to minor) for the additional coastal seasonal restriction under 

Alternative B.

Under Alternative B, none of the additional mitigation measures would affect the potential 

impacts to marine and coastal birds from trash and debris. Through required compliance with USCG 

and USEPA regulations and BSEE guidance, impacts of trash and debris to marine and coastal 

birds are expected to be nominal. 

4.6.3.1.2 Minimum Separation Distances

Alternative B would establish a 40-km (25-mi) separation distance between simultaneously 

operating deep-penetration seismic airgun surveys within the Areas of Concern (Chapter 2.2.2) to 

limit ensonification of specific areas of the AOI at the same time. When outside the Areas of 

Concern, the separation distance will be 30 km (19 mi). However, the separation distance 
4-250 Description of the Affected Resources and Impact Analysis

requirement does not apply to multiple ships operating in a coordinated survey such as a WAZ 

survey, and it need not be maintained if unsafe or due to weather conditions.

Limits on concurrent seismic airgun surveys under Alternative B could change the timing of 

these surveys in certain areas and limit the ensonification of specific areas from multiple airgun 

surveys, but they would not alter the extent of survey types or the aerial coverage of surveys in the 

AOI. The locations that benefit from the limit on ensonification cannot be predicted in advance and 

would depend on the schedule, planned coverage of individual surveys, and ports to be used for 

support activities. As discussed in Chapter 4.6.2.1, impacts of active acoustic sound sources, 

vessel traffic, and the associated vessel and equipment noise on marine and coastal birds are 

expected to range from nominal to minor, depending on location, time of year (migratory seasons), 

and bird species. A change in survey timing because of limits on concurrent seismic airgun surveys 

would not alter the overall impacts from active acoustic sound, vessel traffic, vessel and equipment 

noise, or aircraft traffic and noise on marine and coastal birds; however, limiting the ensonification of 

areas from multiple airgun surveys would reduce active acoustic sound source impacts from airguns, 

which make up the bulk of the survey line miles in the proposed action. However, the potential to 

impact listed species would still exist, resulting in no substantial change from the impact level 

estimated for Alternative A (nominal to minor). As discussed in Chapter 4.6.2.1, impacts of trash 

and debris on marine and coastal birds are expected to be nominal through required compliance 

with USCG and USEPA regulations, as well as BSEE guidance, and impacts would be largely 

unchanged by limits on concurrent seismic airgun surveys.

4.6.3.1.3 Seismic Restrictions in the Areas of Concern within the EPA

Additional restrictions under Alternative B include the prohibition of deep-penetration seismic 

airgun surveys within the portion of the Areas of Concern (Chapter 2.2.2) within the EPA. This 

restriction does not apply to surveys related to currently leased blocks, any portion of the area 

encompassed by EPA Lease Sale 226, or neighboring OCS lease blocks adjacent to permitted 

survey areas but within an otherwise off limit area.

A restriction on deep-penetration seismic airgun surveys within portions of the AOI (Federal 

coastal waters from January 1 through April 30 and the portion of the Areas of Concern falling within 

the EPA) would change the location and timing of these airgun surveys in certain areas, but the 

surveys would still likely occur elsewhere. As discussed in Chapter 4.6.2.1, impacts of active 

acoustic sound sources on marine and coastal birds are expected to be nominal to minor, 

depending on location. A restriction on seismic surveys within portions of the AOI would reduce 

impacts from active acoustic sound sources within specific areas of the EPA and for 2 months within 

Federal coastal waters, but it would not alter the impacts of other active acoustic sound sources from 

other equipment types in those areas. While restrictions on airgun surveys would reduce impacts in 

those specific areas, overall impacts from active acoustic sound sources would remain unchanged 

from Alternative A because listed species, IBAs, and prey abundance could still be impacted, as 

described in Chapter 4.6.2.1; therefore, impacts of active acoustic sound sources on marine and 

coastal birds are expected to remain nominal to minor under Alternative B.
Gulf of Mexico G&G Activities Programmatic EIS 4-251

Under Alternative B, a restriction of seismic airgun surveys within portions of the EPA and in 

Federal coastal waters would result in a decrease of vessel traffic and associated vessel and 

equipment noise from these surveys. Implementation of a minimum separation distance within the 

Areas of Concern would result in a reduction of airgun sound in these areas compared with

Alternative A. As discussed in Chapter 4.6.2.1, impacts of vessel traffic and noise on marine and 

coastal birds are expected to be nominal to minor depending on location. Restricting seismic 

activity within Federal coastal waters for 2 months and within portions of the EPA under Alternative B 

could result in a localized reduction of vessel traffic and noise for some groups of marine and coastal 

birds (e.g., shorebirds); however, overall impacts from vessel traffic and noise would be expected to 

remain nominal to minor because the reduction of vessel traffic and noise would be localized and 

temporary within coastal waters.

The restriction of seismic surveys within Federal coastal waters and portions of the EPA

under Alternative B would not affect the potential for one aeromagnetic survey to occur or for the 

drilling of two shallow test wells and a COST well to occur and would not reduce the need for 

helicopter crew transfers. Therefore, it is expected that the impacts from aircraft traffic and noise 

would remain unchanged (nominal to minor) for the additional airgun survey restrictions under 

Alternative B.

Impacts of trash and debris to marine and coastal birds are expected to be nominal through 

required compliance with USCG and USEPA regulations, as well as BSEE guidance, and therefore, 

impacts would be unchanged under Alternative B.

4.6.3.1.4 Routine Activities Impact Conclusions

There is the potential for temporary displacement of marine and coastal bird species from a 

portion of preferred feeding grounds during migration and from locations of non-critical activities 

during non-migration seasons, resulting in nominal indirect impacts from airgun and HRG surveys. 

However, if airgun and HRG surveys and the potential associated temporary displacement of 

species from a portion of preferred feeding areas occurred during bird species migration, then the 

impact would be considered minor. Impacts from vessel and equipment noise, vessel traffic, and 

aircraft traffic and noise are expected to be nominal in most circumstances, but if spatial and 

temporal conditions of proposed activities coincide with biologically important areas or activities, 

impacts could be minor. Impacts from trash and debris would be nominal. 

4.6.3.2 Impacts of an Accidental Fuel Spill

Under Alternative B, impacts of an accidental fuel spill on marine and coastal birds would be 

very similar to those analyzed in Chapter 4.6.2.2 for Alternative A. The analysis concluded that 

impacts to shorebirds, waterfowl, and seabird species would range from nominal to minor

depending on timing and location. Populations of listed species are already in peril; therefore, an 

accidental fuel spill that affected any of these species or their food supply would cause moderate 

impacts. Alternative B would change the timing of certain surveys because of a seasonal restriction 

and limits on concurrent seismic airgun surveys. Additionally, certain surveys will not be conducted 
4-252 Description of the Affected Resources and Impact Analysis

within portions of the EPA. However, fuel spills from seismic survey vessels could occur in the 

closure areas during times outside of the closure period. Also, fuel spills from other survey vessels 

could occur during the closure period or in the EPA depending on the frequency of the HRG sound 

source used. A change in survey timing or type because of limits on concurrent seismic airgun 

surveys or on survey type would not substantially change the risk of a small fuel spill. Overall, the 

risk of a small fuel spill and the potential impacts on marine and coastal birds would be the same as 

under Alternative A (nominal to moderate) depending on the spill location and whether listed bird 

species within the AOI are affected by the spill.

4.6.3.3 Cumulative Impacts

Impact analyses presented in Chapters 4.6.3.1 and 4.6.3.2 determined that activities 

projected to occur under Alternative B would result in nominal, minor, or moderate impacts to 

marine and coastal birds, depending on the IPF. Mitigation measures for the proposed action under 

Alternative B are described in Chapter 2.2 and summarized in Chapter 4.6.3.1. A detailed impacts 

assessment under the cumulative scenario is provided in Alternative A (Chapter 4.6.2.3). Mitigation 

measures under Alternative B would not appreciably change the extent, severity, or timing of 

activities in the proposed action; thus, the resultant impacts to marine and coastal birds would not 

change.

The cumulative impact analysis identified nominal incremental increases in impacts from all 

IPFs under Alternative A (Chapter 4.6.2) and would remain under Alternative B.

4.6.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.6.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative C on marine and coastal birds.

4.6.4.1 Impacts of Routine Activities

Additional mitigation measures under Alternative C that would not change the extent, 

severity, or timing of G&G activities, and therefore related impacts to marine and coastal birds, 

include the expanded use of PAM for seismic airgun surveys, the expanded use of PSOs for seismic 

airgun surveys and HRG surveys, expansion of NTL 2012-JOINT-G02 (inclusion of manatees) for 

seismic airgun surveys, a pre-survey clearance period for HRG surveys, and expansion of NTL 

2012-JOINT-G02 to include HRG surveys using airguns. As such, those mitigation measures will 

not be addressed in the following discussion.

4.6.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to May 31)

Alternative C would include a seasonal restriction in all Federal coastal waters of the GOM 

shoreward of the 20-m (66-ft) isobath between February 1 and May 31. No airgun surveys would be 

authorized within the closure area during this time.
Gulf of Mexico G&G Activities Programmatic EIS 4-253

As discussed in Chapter 4.6.2, applicable routine IPFs for marine and coastal birds are 

active acoustic sound sources, vessel traffic and associated vessel and equipment noise, aircraft 

traffic and noise, and trash and debris. Chapter 4.6.2.1 states that impacts of active acoustic sound 

sources on marine and coastal birds are expected to range from nominal to minor depending on 

location, timing, and species impacted.

Restricting seismic airgun surveys in Federal and State coastal waters of the GOM from 

February 1 through May 31 would result in reduced impacts from acoustic sound sources within the 

seasonal restriction area for a period of 4 months. This restriction would reduce impacts to bird 

species migrating in the spring; however, the seasonal restriction would only alter the timing of these 

surveys in the closure area. A change in the timing of seismic airgun surveys would not alter the

overall impacts of active acoustic noise from seismic airgun surveys on marine and coastal birds. 

Therefore, impacts of active acoustic sound sources on marine and coastal birds under Alternative C 

are expected to remain nominal to minor depending on location, timing, and bird species.

The seasonal restriction of Federal and State coastal waters under Alternative C would 

reduce the vessel traffic and associated noise from seismic airgun surveys in the coastal area during 

a 4-month period; however, the 4-month restriction would only change the timing of seismic airgun 

surveys in coastal areas and would not reduce the amount of survey line miles. As discussed in 

Chapter 4.6.2.1, impacts of vessel traffic and vessel and equipment noise on marine and coastal 

birds are expected to be nominal to minor depending on location. A change in survey timing in the 

coastal closure area could reduce the impacts of vessel traffic and noise from seismic airgun 

surveys on some groups of marine and coastal birds (e.g., shorebirds) for a period of time. 

However, the impacts to marine and coastal birds from vessel traffic and noise still would be 

expected to be nominal to minor because the additional closure does reduce overall impact levels 

but only by shifting the timing of the impacts.

The additional seasonal restriction for coastal areas under Alternative C would not affect the 

potential for one aeromagnetic survey to occur or for the drilling of two shallow test wells and a 

COST well to occur. Therefore, it is expected that the impacts from aircraft traffic and noise would 

remain unchanged (e.g., nominal to minor) for the additional coastal seasonal restriction under 

Alternative C.

Impacts of trash and debris to marine and coastal birds are expected to be nominal through 

required compliance with USCG and USEPA regulations as well as BSEE guidance; therefore, 

impacts would be unchanged under Alternative C.

4.6.4.1.2 Routine Activities Impact Conclusions

There is the potential for temporary displacement of marine and coastal bird species from a 

portion of preferred feeding grounds during migration and from locations of non-critical activities 

during non-migration seasons, resulting in nominal indirect impacts from airgun and HRG surveys. 

However, if airgun and HRG surveys and the potential associated temporary displacement of 
4-254 Description of the Affected Resources and Impact Analysis

species from a portion of preferred feeding areas occurred during bird species migration, then the 

impact would be considered minor. Impacts from vessel and equipment noise, vessel traffic, and 

aircraft traffic and noise are expected to be nominal in most circumstances, but if spatial and 

temporal conditions of proposed activities coincide with biologically important areas or activities, 

impacts could be minor. Impacts from trash and debris would be nominal. 

4.6.4.2 Impacts of an Accidental Fuel Spill

Under Alternative C, impacts of an accidental fuel spill on marine and coastal birds would be 

very similar to those analyzed in Chapter 4.6.2.2 for Alternative A. The analysis concluded that 

impacts to shorebirds, waterfowl, and seabird species would range from nominal to minor

depending on timing and location. The populations of listed species are already in peril, so an 

accidental fuel spill that affected any of these species or their food supply would cause moderate 

impacts. Alternative C would change the timing of seismic surveys because they would be restricted 

in coastal waters for 4 months. The change in timing of the seismic surveys would slightly reduce 

the likelihood of an accidental event during the closure period. However, fuel spills from seismic 

survey vessels could occur in the closure areas during times outside the closure period (February 1 

through May 31) and fuel spills from other survey vessels could occur within the closure area during 

the closure period. A change in survey timing would not substantially change the risk of a small fuel 

spill. Overall, the risk of a small fuel spill and the potential impacts on marine and coastal birds 

would be the same as under Alternative A and would range from nominal to moderate, depending 

on the spill location and whether listed bird species within the AOI are affected by the spill.

4.6.4.3 Cumulative Impacts

Impact analyses presented in Chapters 4.6.4.1 and 4.6.4.2 determined that activities 

projected to occur under Alternative C would result in nominal, minor, or moderate impacts to 

marine and coastal birds depending on the IPF. Mitigation measures for the proposed action under 

Alternative C are described in Chapter 2.3 and summarized in Chapter 4.6.4.1. A detailed impacts 

assessment under the cumulative scenario is provided in Alternative A (Chapter 4.6.2.3). Most 

mitigation measures under Alternative C would not change the extent, severity, or timing of activities 

in the proposed action; thus, the resultant impacts to marine and coastal birds would not change.

The cumulative impact analysis identified nominal incremental increases in impacts from all 

IPFs under Alternative A. The cumulative scenario would remain unchanged for Alternative C and 

the associated impacts would remain the same. Alternative C would change the timing of seismic 

airgun surveys in certain areas and decrease impacts to marine and coastal birds during the closure; 

however, the coastal seasonal restriction would not appreciably change the cumulative impacts 

noted under Alternative A. While a coastal seasonal restriction is effective in decreasing impacts 

during the restriction period, it will not result in a substantial decrease in the overall activities, and 

any resultant incremental increase in impacts would remain nominal. 
Gulf of Mexico G&G Activities Programmatic EIS 4-255

4.6.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative D are the same as for 

Alternative A (Chapter 4.6.2). The additional mitigation measure, i.e., shutdowns for marine 

mammals, under Alternative D would not reduce potential active acoustic impacts discussed under 

Alternatives A and C (Chapters 4.6.2.1 and 4.6.4.1), and impacts would remain nominal from 

airgun and HRG surveys to minor if airgun and HRG surveys occurred during species migration. 

This mitigation would not alter the impact levels to marine and coastal birds from vessel and 

equipment noise, aircraft traffic and noise, or trash and debris, and impacts would remain nominal

to minor. Under Alternative D, impacts of an accidental fuel spill on marine and coastal birds would 

be as described for Alternatives A and C (Chapters 4.6.2.2 and 4.6.4.2) and would remain nominal

to moderate. 

4.6.5.1 Impacts of Routine Activities

Mitigation measures under Alternative D include all measures provided under Alternatives A 

and C, with the addition of shutdown protocols for all marine mammals, except bow-riding dolphins, 

during seismic surveys. Therefore, as discussed under Alternatives A and C (Chapters 4.6.2.1 and 

4.6.4.1), all of the mitigation measures provided under Alternative D, except for the seasonal 

restriction for the operation of airguns in coastal waters, would not change the extent or severity of 

G&G activities and, consequently, the associated impacts to marine and coastal birds. As such, 

those mitigation measures will not be addressed in the following discussion.

As discussed in Chapter 4.6.2, applicable routine IPFs for marine and coastal birds are 

active acoustic sound sources, vessel traffic and associated vessel and equipment noise, aircraft 

traffic and noise, and trash and debris. As discussed in Chapter 4.6.2.1, impacts of active acoustic 

sound sources on marine and coastal birds are expected to be nominal to minor depending on 

location, timing, and bird species. As discussed in Chapter 4.6.2.1, impacts of vessel traffic and 

vessel and equipment noise on marine and coastal birds are expected to be nominal to minor

depending on location. It is expected that the impacts from aircraft traffic and noise would remain 

unchanged (e.g., nominal to minor) for the additional coastal seasonal restriction under 

Alternative D. Impacts of trash and debris to marine and coastal birds are expected to be nominal

through required compliance with USCG and USEPA regulations as well as BSEE guidance and, 

therefore, impacts would be unchanged under Alternative D.

4.6.5.2 Impacts of an Accidental Fuel Spill

Under Alternative D, impacts of an accidental fuel spill on marine and coastal birds would be 

very similar to those analyzed in Chapter 4.6.2.2 for Alternative A. The analysis concluded that 

impacts to shorebirds, waterfowl, and seabird species would range from nominal to minor

depending on timing and location. Populations of listed species are already in peril; therefore, an 

accidental fuel spill that affected any of these species or their food supply would cause moderate 

impacts. 
4-256 Description of the Affected Resources and Impact Analysis

Alternative D would change the timing of certain surveys because of the coastal seasonal 

restriction. However, fuel spills from seismic survey vessels could occur in the closure area during 

times outside the closure period. Also, fuel spills from other survey vessels could occur within the 

closure area during the closure period. A change in survey timing would not substantially change 

the risk of a small fuel spill. Overall, the risk of a small fuel spill and the potential impacts on marine 

and coastal birds would be the same as under Alternative A (nominal to moderate), depending on 

the spill location and whether listed bird species within the AOI are affected by the spill.

4.6.5.3 Cumulative Impacts 

Impact analyses presented in Chapters 4.6.5.1 and 4.6.5.2 determined that activities 

projected to occur under Alternative D would result in nominal, minor, or moderate impacts to 

marine and coastal birds depending on the IPF.

Mitigation measures for the proposed action under Alternative D are described in 

Chapter 2.4 and summarized in Chapter 4.6.5.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.6.2.3). The mitigation measures are the 

same as described for Alternative C, with the addition of shutdown protocols during seismic 

operations for all marine mammals (except bow-riding dolphins). The addition of shutdown protocols 

for all marine mammals except bow-riding dolphins under Alternative D would not change the extent, 

severity, or timing of activities in the proposed action; thus, the resultant impacts to marine and 

coastal birds would not change.

The cumulative impact analysis identified nominal incremental increases in impacts from all 

IPFs under Alternative A. The cumulative scenario would remain unchanged for Alternative D, and 

the associated impacts would remain the same.

4.6.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.6.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative E on marine and coastal birds.

4.6.6.1 Impacts of Routine Activities 

The reduction of deep-penetration, multi-client activities by 10 or 25 percent under 

Alternatives E1 and E2, respectively, would reduce the extent and severity of active acoustic sound 

sources, vessel and equipment noise, vessel traffic, aircraft traffic and noise, and trash and debris 

associated with these surveys; therefore, impacts for these IPFs would be incrementally decreased 

under Alternatives E1 and E2.

4.6.6.1.1 Reduced Level of Activity

Active acoustic sound sources associated with deep-penetration, multi-client activities under 

Alternative E would decrease by 10 and 25 percent for Alternatives E1 and E2, respectively, thereby 
Gulf of Mexico G&G Activities Programmatic EIS 4-257

decreasing the potential for associated impacts to marine and coastal birds. The deep-penetration,

multi-client seismic surveys, such as 2D, 3D, WAZ, and 4D surveys, make up the majority of G&G 

survey activity in the proposed action (Table 3.2-2).

As presented in Chapter 4.6.2.1, the impacts to marine and coastal birds from Alternative A 

from active acoustic sound sources were determined to be nominal or minor, depending on the 

location of the survey and the equipment being used.

Active acoustic sound sources under Alternatives E1 and E2 include reduced deeppenetration, multi-client surveys based on a 10 percent or 25 percent reduction in line miles. 

Seabirds and waterfowl that rest on the water surface or make shallow dives for short durations 

would reduce the interactions of marine and coastal birds with active acoustic sounds generated 

from deep-penetration, multi-client surveys; therefore, impacts from active acoustic sources would 

be reduced to nominal for these birds. Because electromechanical sources from HRG surveys are 

not reduced in this alternative, impacts would remain as described Alternative A (nominal to minor).

Even at reduced levels under Alternatives E1 and E2, BCRs, IBAs, and NWRs may be 

indirectly impacted through temporary prey displacement, resulting in temporary displacement of 

coastal and marine bird species from important feeding areas. The reduction of activity under 

Alternatives E1 and E2 would not significantly reduce the likelihood of coastal and marine bird 

species being temporarily displaced; in considering the level of impact and significance criteria, 

impacts from active acoustic sound sources under Alternatives E1 and E2 would remain nominal to 

minor. 

Similar to Alternative A, the primary potential impacts to marine and coastal birds from vessel 

traffic and noise are from underwater vessel and equipment noise, attraction to vessels and 

subsequent collision or entanglement, disturbance to nesting or roosting, and disturbance to feeding 

or modified prey abundance. Under Alternatives E1 and E2, because of a reduction in survey line 

miles, vessel traffic and noise would result in a reduction in overall impacts; however, in considering 

the level of impact and significance criteria, impacts from vessel traffic and vessel and equipment 

noise under Alternatives E1 and E2 would remain nominal to minor. 

Helicopters will be used to support deep-penetration, multi-client activities by transporting 

crew to and from vessels. A 10 or 25 percent reduction (Alternative E2) in deep-penetration, multiclient activities (compared with Alternative A) will reduce the number of flights required to support 

these surveys. The reduction of deep-penetration seismic survey activity under Alternatives E1 and 

E2 would decrease the number of helicopter flights necessary to support these surveys; however, 

because the timing of the reduction is not known, potential impacts from this activity would range 

from nominal during the non-migration season to minor during the migration season (because of 

the greater numbers and higher densities of migrants crossing the GOM).
4-258 Description of the Affected Resources and Impact Analysis

Impacts of trash and debris to marine and coastal birds are expected to be nominal through 

required compliance with USCG and USEPA regulations as well as BSEE guidance and, therefore, 

impacts would be unchanged under Alternative E.

4.6.6.1.2 Routine Activities Impact Conclusions

Impacts from active acoustic sounds would be reduced to nominal due to the reduction of 

activity; electromechanical sources from HRG surveys are not reduced in this alternative, so impacts 

would remain as described Alternative A (nominal to minor). Impacts from other IPFs, including 

vessel and equipment noise, vessel traffic, aircraft traffic and noise, and trash and debris, would 

remain unchanged (nominal to minor).

4.6.6.2 Impacts of an Accidental Fuel Spill

Under Alternative E, impacts of an accidental fuel spill on marine and coastal birds would be 

very similar to those analyzed for Alternatives A and C (Chapters 4.6.2.2 and 4.6.4.2). The analysis 

concluded that impacts to common species would range from nominal to minor depending on 

timing and location. An accidental fuel spill that affected any listed species or their food supply 

would cause moderate impacts.

Alternative E would not substantially change the risk of a small fuel spill. Overall, the risk of 

a small fuel spill and the potential impacts on marine and coastal birds would be the same and would 

range from nominal to moderate for Alternatives E1 and E2, depending on the spill location and 

whether listed bird species within the AOI are affected by the spill.

4.6.6.3 Cumulative Impacts

Impact analyses presented in Chapters 4.6.6.1 and 4.6.6.2 determined that activities 

projected to occur under Alternative E would result in nominal, minor, or moderate impacts to 

marine and coastal birds depending on the IPF. Mitigation measures for the proposed action under 

Alternative E are described in Chapter 2.5 and summarized in Chapter 4.6.6.1. The reduction of 

deep-penetration, multi-client activities (in line miles) by 10 percent (Alternative E1) or 25 percent 

(Alternative E2) would reduce the extent, severity, and timing of active acoustic sound sources, 

vessel and equipment noise, vessel traffic, aircraft traffic and noise, and trash and debris; therefore, 

impacts for these IPFs would be incrementally decreased under Alternative E.

The cumulative scenario would remain the same for Alternatives E1 and E2 as with 

Alternative A, and the associated impacts would remain the same.

4.6.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.6.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative F on marine and coastal birds.
Gulf of Mexico G&G Activities Programmatic EIS 4-259

4.6.7.1 Impacts of Routine Activities

The additional mitigation measures under Alternative F would not change the extent or 

severity of IPFs analyzed; consequently, the impacts to marine and coastal birds would be 

unchanged under Alternative F compared with Alternative C, ranging from nominal to minor. 

Alternative F would require area closures in the CPA Closure Area, EPA Closure Area, Dry 

Tortugas Closure Area, and Flower Gardens Closure Area for seismic airgun survey operations. 

Impacts from active acoustic sound sources, vessel and equipment noise, vessel traffic, and aircraft 

traffic and noise on marine and coastal birds are expected to range from nominal to minor

(Chapter 4.6.4.1). Impacts from trash and debris to marine and coastal birds are expected to be 

nominal, as in Alternative A. The additional closure of four areas would reduce or eliminate impacts 

from the relevant IPFs on marine and coastal birds as these surveys would not occur within the 

designated areas; however, the overall level of G&G activity within the AOI would remain unchanged 

and any reduction or elimination of impacts would be localized. None of the additional closure areas 

are of any specific significance to marine and coastal birds; therefore, the impacts to marine and 

coastal birds under Alternative F would be expected to remain nominal to minor based on location, 

timing, and bird species.

4.6.7.2 Impacts of an Accidental Fuel Spill

Under Alternative F, impacts of an accidental fuel spill would be very similar to those 

analyzed in Chapter 4.6.4.2 for Alternative C. The analysis concluded that impacts to common 

shorebirds, waterfowl, and seabirds would range from nominal to minor. An accidental fuel spill 

affecting listed species or their food supply would cause moderate impacts. 

The risk of an accidental spill related to these activities would be lessened within the closure 

areas because seismic airgun operations would be prohibited; however, vessels could still use the 

area for transit, so the risk of an accidental spill would still exist. Additionally, the overall extent of 

survey activity within the GOM would not be reduced under Alternative F, and the overall risk of an 

accidental spill, although low, would remain despite certain areas being closed because spills from 

seismic survey vessels could occur outside the closure areas and still impact the closure areas from 

transit of spilled fuel. Also, spills from other vessels could occur within the closure areas. Therefore, 

Alternative F would not substantially change the risk of a small fuel spill or the risk of impacts from a 

spill. Overall, the risk of an accidental fuel spill and the potential impacts on marine and coastal 

birds would be the same as under Alternative C and would range from nominal to moderate, 

depending on the spill location and whether listed bird species within the AOI are affected by the 

spill.

4.6.7.3 Cumulative Impacts

Impact analyses presented in Chapters 4.6.7.1 and 4.6.7.2 determined that activities 

projected to occur under Alternative F would result in nominal, minor, or moderate impacts to 

marine and coastal birds depending on the IPF.
4-260 Description of the Affected Resources and Impact Analysis

Mitigation measures for the proposed action under Alternative F are described in Chapter

2.6 and summarized in Chapter 4.6.7.1. Mitigation measures under Alternative F are similar to 

Alternative C with the addition of closures in four areas: the CPA Closure Area; the EPA Closure 

Area; the Dry Tortugas Closure Area; and the Flower Gardens Closure Area.

The cumulative scenario would remain unchanged for Alternative F, and the associated 

impacts would remain the same. Alternative F would change the timing of seismic airgun surveys in 

certain areas and would restrict airgun surveys from four areas within the AOI; however, the coastal 

seasonal restriction area and area closures and restrictions would not appreciably change the 

cumulative impacts noted under Alternative A. While the area closures are effective in decreasing 

impacts, they, or the addition of the restriction of airgun surveys in areas farther offshore, will not 

result in a decrease in the overall activities, and the resultant impacts for the proposed action to the 

cumulative scenario and the incremental increase in impacts would be nominal. 

4.6.8 Impacts – Alternative G (No New Activity Alternative)

The IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.6.2).

4.6.8.1 Impacts of Routine Activities

Under Alternative G, BOEM would cease issuing permits/authorizations for new G&G 

surveys and would not approve G&G surveys proposed under exploration or development plans. 

However, G&G activities previously authorized under an existing permit/authorization or lease would 

proceed. Active acoustic sounds would persist in the near-term and at greatly reduced impact levels 

commensurate with the reduction in survey effort (Table 2.7-1). Impacts to marine and coastal birds 

from vessel and equipment noise, vessel traffic, aircraft traffic and noise, trash and debris, and 

accidental fuel spills generated from G&G activities would be reduced to nominal under 

Alternative G and would eventually be reduced to no impact. 

4.6.8.2 Impacts of Accidental Fuel Spill

Under Alternative G, impacts of an accidental fuel spill on marine and coastal birds would be 

very similar to those analyzed Alternative A (Chapter 4.6.2.2). The analysis concluded that impacts 

to shorebirds, waterfowl, and seabird species would range from nominal to minor depending on 

timing and location. Populations of listed species are already in peril; therefore, an accidental fuel 

spill that affected any of these species or their food supply would cause moderate impacts. 

Alternative G would not have the involvement of the quantity of vessels, but the risk remains 

that an accidental spill could occur. Therefore, Alternative G would range from nominal to 

moderate, depending on the spill location and whether listed bird species within the AOI are 

affected by the spill.
Gulf of Mexico G&G Activities Programmatic EIS 4-261

4.6.8.3 Cumulative Impacts

A detailed impacts assessment under the cumulative scenario is provided in Alternative A 

(Chapter 4.6.2.3). Impact analyses presented in Chapters 4.6.8.1 and 4.6.8.2 determined that 

activities projected to occur under Alternative G would result in nominal to moderate impacts to 

marine and coastal birds depending on the IPF.

The cessation of activity for future G&G surveys requiring a permit/authorization from BOEM 

would substantially decrease the cumulative impacts from all IPFs. However, VSP and SWD 

surveys are expected to continue under Alternative G. Therefore, following cessation of the majority 

of activities, there would be a nominal incremental increase in impacts from active acoustic sound 

sources, vessel and equipment noise, vessel traffic, aircraft traffic and noise, trash and debris, and 

accidental fuel spills.

4.7 MARINE PROTECTED AREAS

4.7.1 Description of the Affected Environment

A Marine Protected Area (MPA) is defined by EO 13158 as “any area of the marine 

environment that has been reserved by Federal, State, territorial, Tribal, or local laws or regulations 

to provide lasting protection for part or all of the natural and cultural resources therein.” In practice, 

MPAs are defined areas where natural and/or cultural resources are given greater protection than 

the surrounding waters. In the U.S., MPAs span a range of habitats including the open ocean, coral 

reefs, deepwater habitats, coastal areas, intertidal zones, estuaries, and the Great Lakes, and they 

can include freshwater or terrestrial areas. A National System of MPAs was established in 2009 as 

a nationwide program for the effective stewardship, conservation, restoration, sustainable use, 

understanding, and appreciation of marine resources. The National System currently includes 

437 Federal, State, and territorial MPAs covering an area of 494,765 km2 (191,030 mi2

) according to 

NOAA’s National Marine Protected Areas Center website. For the purpose of this analysis, National 

System MPAs are presented; however, it is recognized in Chapter 4.5 that additional areas are 

afforded protection by other management systems (e.g., GMFMC) (Simmons et al., 2015), and 

specific management areas (e.g., banks, topographic features) may be included within boundaries of 

existing National System MPAs.

There are 94 National System offshore MPAs within the AOI; these are listed in Table 4.7-1

and their locations are shown in Figures 4.7 1 and 4.7-2. They are additionally described in 

Appendix E, Section 7. Table 4.7-1 contains sites that are currently members of the National 

System of MPAs, as well as those sites listed and eligible for inclusion as part of the National 

System. The information was obtained from the Marine Protected Areas Inventory located on 

NOAA’s National Marine Protected Areas Center website. All sites listed are afforded some degree 

of protection based on their associated management plans.

The following chapter is summarized by the different groupings of MPAs as provided in 

Appendix E. For the affected environment, a summary for each grouping is provided, and the 
4-262 Description of the Affected Resources and Impact Analysis

summary entails the typical marine or coastal habitats and noted fauna present within that grouping 

of MPAs, as opposed to addressing each MPA individually. As noted, more specific details about 

each MPA is provided in Appendix E, including what portion of the MPA falls within the AOI.

It is important to note that, although an MPA has been established for a specific intent 

concerning preservation of particular fauna/flora (e.g., seasonal closure of a particular fishing gear to 

relieve pressure on fish stocks within a reserve), other fauna/flora are present in these areas 

although not highlighted in this chapter on MPAs. Such fauna are addressed in other chapters of 

this Programmatic EIS. In the interest of brevity, this Programmatic EIS does not re-list all of the 

potential faunal groupings that could be and are likely present because these are addressed in their 

respective chapters.

4.7.1.1 Offshore Marine Protected Areas

Offshore MPAs within the AOI include NMSs, deepwater MPAs, and other fishery 

management areas (Figure 4.7-1; Table 4.7-1).

National Marine Sanctuaries

Two NMSs are located within the AOI, the Florida Keys National Marine Sanctuary (FKNMS) 

and the FGBNMS, the latter of which is located in the northwestern GOM. These regions contain 

important habitats and fauna that contribute to why these regions are protected and are 

administered by NOAA’s National Office of Marine Sanctuaries (ONMS).

The FKNMS, which is not located within any of BOEM’s planning areas, supports 

6,000 species of marine life and contains the world’s third largest barrier reef, extensive seagrass 

meadows, and mangrove-fringed islands. A variety of plants, invertebrates, fishes, reptiles, birds, 

and mammals that use or contribute to sanctuary resources in the Florida Keys are protected at the 

Federal or State level. Each of these species is a valuable natural resource that contributes to the 

ecological balance of the sanctuary. Animal species at risk are dependent on the sanctuary’s 

diverse habitats, including mangroves, beaches (below high water mark), seagrass beds, and coral 

reefs. State and federally listed threatened and endangered marine and aquatic fauna include, but 

are not limited to, elkhorn coral, staghorn coral, pillar coral, all five species of sea turtles found in the 

western Atlantic (i.e., loggerhead, green, hawksbill, Kemp’s ridley, and leatherback), the American 

alligator (Alligator mississippiensis), American crocodile (Crocodylus acutus), smalltooth sawfish, 

Roseate Tern, Least Tern, and the West Indian manatee. The sanctuary is also in the migratory 

range of three species of whales: humpback whale, fin whale, and North Atlantic right whale. The 

sanctuary also protects elements of history such as shipwrecks and other archeological treasures, 

including approximately 669 historic artificial reefs that have been documented to date. As of 

January 2016, 14 shipwrecks and two lighthouses within the sanctuary are listed on the National 

Register of Historic Places.

The FGBNMS is located in the northwestern GOM and consists of three distinct areas: East 

FGB, West FGB, and Stetson Bank. The FGBs reefs are the northernmost living coral reefs on the 
Gulf of Mexico G&G Activities Programmatic EIS 4-263

U.S. continental shelf. Isolated from other coral reef systems by >556 km (300 nmi), the East and 

West FGBs favor hard corals and support at least 21 species. Eight species of coral are found on 

Stetson Bank, where the cooler water temperatures favor non-reef-building corals and sponges. 

Located in the general region of the East and West FGBs are other reefs and midshelf and shelfedge banks with existing or proposed designation as HAPCs, including Sonnier Bank, McGrail Bank, 

Bright Bank, Geyer Bank, and Alderdice Bank. These designated deepwater (>70 m [230 ft]) 

habitats contain outcroppings rising up from the seafloor populated with benthic invertebrates, 

coralline algae, deep corals, and a variety of fish species. All HAPCs have protective measures 

from certain fishing operations and vessel anchoring, and are identified as areas for special 

consideration during individual species assessments.

More than 300 different fish species and 3 species of sea turtles (i.e., hawksbill, leatherback, 

and loggerhead) inhabit FGBNMS waters. Macroalgae, crustaceans, sharks, skates, rays, many 

different types of benthic invertebrates, and a variety of seabirds thrive in the protected waters 

around FGBs (Showalter and Schiavinato, 2003). For additional details on these sanctuaries, refer 

to Appendix E. 

Offshore Marine Protection Areas Pulley Ridge HAPC, the deepest hermatypic, or reefbuilding, coral reef in the continental U.S., is located on Pulley Ridge off the southwest coast of 

Florida. The ridge itself is a drowned barrier island approximately 100 km (62.1 mi) long by 5 km 

(3.1 mi) wide, oriented parallel to the Florida peninsula northwest of the Dry Tortugas (Figure 4.7-1). 

Live corals dominated by Agaricia sp. occur between the 60- and 70-m (197- and-230 ft) isobaths on 

the reef along with a diverse assemblage of fish species comprising a mixture of shallow-water and 

deepwater species.

Pulley Ridge HAPC and some fishing activities involving pots, traps, longlines, nets, and 

anchoring are prohibited, but growing concern for the hermatypic corals in the area may lead to 

future management actions (Fisheries Leadership and Sustainability Forum, 2015). The GMFMC 

deepwater coral working group has expressed concern over ongoing damage to Pulley Ridge habitat 

by fishing operations and is considering additional protective measures. In May 2015, the Joint 

Coral Scientific and Statistical Committee and Coral Advisory Panel (Coral SSC/AP) recommended 

extended boundaries for the Pulley Ridge HAPC stating specific concerns over the golden crab 

fishery (Coral SSC/AP, 2015).

Other Federal Fishery Management Areas

Other Federal offshore MPAs have been designated by NMFS and the GMFMC with 

different degrees of management and protection and include reserves such as the Tortugas 

Ecological Reserve and specialized management areas such as the Reef Fish Stressed Area 

(Figure 4.7-1).

Protections in these areas can range from gear restrictions (seasonal closures on gear such 

as longlining to anchoring fish traps on the seafloor) to complete limitations on any access. The 
4-264 Description of the Affected Resources and Impact Analysis

MPAs were designated to protect a variety of different fauna ranging from large pelagic fishes such 

as tunas, billfish, and sharks to more bottom and reef-associated fish species such as gag grouper 

(USDOI, BOEM, 2013b,c) to coastal fishes located closer to shore. Measures were also developed 

to protected non-targeted yet still affected fauna such as sea turtles to more general regional 

protective measures for benthic habitat and associated fauna/flora.

In deeper regions, Federal fishery management areas include McGrail Bank, designated as 

a coral HAPC, where deeper reef habitat includes extensive coralline algae and deep coral 

assemblages. Year-round fishing regulations within McGrail Bank include the prohibition of bottom 

longline, bottom trawl, buoy gear, pot or trap, and bottom anchoring by fishing vessels.

Benthic habitat in the Florida Middle Grounds HAPC supports a wide variety of hermatypic 

corals, octocorals, sponges, other invertebrates, and fish. This area is recognized as the 

northernmost coral reef community in the GOM (Simmons et al., 2014). The Big Bend area of the 

GOM offers deepwater shelf habitats characterized by the Madison Swanson Marine Reserve HAPC 

and Steamboat Lumps. Little is known about the sessile community, but the shelf-edge habitats are 

documented aggregation and spawning sites for multiple species of grouper. The Madison and 

Swanson and Steamboat Lumps are closed to bottom fishing year-round to protect spawning 

grouper.

In terms of protections specifically for flora, the Pelagic Sargassum Habitat Restricted Area, 

which extends along the Atlantic Coast of the U.S. from Virginia along Peninsular Florida tapering to 

a narrow region along the Florida Keys, has seasonal restrictions on the harvest of pelagic 

Sargassum (68 FR 18942).

The Tortugas Marine (Ecological) Reserves consists of two regions totaling 513 km2

(151 nmi2

) in area and created in 2001 at the western extent of the FKNMS (with benthic habitat and 

associated fauna previously noted). The reserve is closed to all consumptive use, including fishing 

and anchoring, and a portion of it is only open to permitted marine research (Jeffrey et al., 2012).

Additionally, the wider Caribbean contains International Union for Conservation of Nature 

(IUCN) designated MPAs for whales, dolphins, and porpoises (Hoyt, 2005). These MPAs are based 

on IUCN protection initiatives for cetaceans and includes other marine mammal species. The 

FKNMS is the only cetacean MPA within the GOM.

4.7.1.2 Coastal Marine Protected Areas

Coastal MPAs within the AOI include national seashores, NWRs, National Estuarine 

Research Reserves (NERRs), and State-designated MPAs (Figure 4.7-2; Table 4.7-1).

National Park System (National Seashores)

There are four coastal national parks within the boundary of the AOI that are administered by 

the National Park Service (NPS). The NPS’ lands along the coast or in coastal areas of the AOI 
Gulf of Mexico G&G Activities Programmatic EIS 4-265

include the Dry Tortugas National Park, Everglades National Park, Gulf Islands National Seashore, 

and Padre Island National Seashore (Figure 4.7 2).

The Dry Tortugas consists mostly of open water habitat and seven small islands. The Dry 

Tortugas falls with the FKNMS and includes coral reefs and their associated communities. It also 

provides habitat for a great diversity of bird species that utilize the area.

The Everglades National Park includes the southern portion of mainland Florida, Florida Bay, 

and portions of the upper Keys. Coastal components include segments of open water, shallow 

waters, extensive seagrass meadows, and mangrove-fringed shorelines and islands.

The Gulf Islands National Seashore spreads across two island chains off the coast of 

Mississippi and Florida’s panhandle. The Gulf Islands consist of eight barrier islands, six in 

Mississippi and two in Florida, making it the Nation’s largest national seashore, spanning >240 km 

(149 mi) of the GOM. Coastal components include segments of beaches, open water, shallow 

water, benthic habitat consisting of primarily sand and mud bottom, isolated areas of seagrasses 

with associated marine flora, invertebrates, and fish (Lavoie et al., 2013). Beach areas provide 

habitat for a variety of bird species and nesting habitat for several species of sea turtles. 

The Padre Island National Seashore lies along the Gulf Coast of Texas and stretches 

180 km (112 mi), making it the longest barrier island in the U.S. Padre Island separates the GOM 

from the Laguna Madre, one of only a few hypersaline lagoons in the world. Coastal components 

include beaches, open GOM waters, benthic habitats of primarily sand and sand marl bottom with 

associated marine flora, invertebrates, and fish. Beach areas provide habitat for a variety of bird 

species as well as nesting habitat for several species of sea turtles.

National Wildlife Refuges

The NWR system is a network of U.S. lands and waters managed by the FWS specifically for 

the enhancement of wildlife. There are currently 19 NWRs contained or with portions within the AOI 

(Table 4.7 1; Figure 4.7 2; Appendix E).

All terrestrial and aquatic resources within the NWR system are managed with the goals of 

conservation, management, and where appropriate, restoration of the fish, wildlife, and plant 

resources and their habitats within the U.S. for the benefit of present and future generations of 

Americans. Management approaches and conservation methods differ among NWRs but typically 

include managing and rehabilitating wildlife habitat, controlling invasive species, and assisting in the 

recovery of rare wildlife species (USDOI, FWS, 2002).

The 19 NWRs were included as they have varying amounts of their coastal areas falling 

within the AOI (Table 4.7-1), and the vast majority provide coastal habitat to a diversity of bird 

species. Protection of important habitat utilized by migratory and/or resident birds appears to be a 

common objective for the initial establishment of most of these NWRs addressed in Appendix E. 
4-266 Description of the Affected Resources and Impact Analysis

Additionally, several of the listed NWRs also provide important habitat for protected coastal species. 

For example, the Ten Thousand Islands NWR and its adjacent waters are utilized by Florida’s 

manatee population, as well as providing habitat for a large concentrations of wading birds, 

shorebirds, waterfowl, and other water birds. Many of these refuges have coastal water components 

that consist of open water regions with benthic habitats primarily composed of soft sediment 

substrates and associated marine fauna and flora.

National Estuarine Research Reserve System

The NERR System is a partnership between NOAA and the coastal States that protects 

>1.3 million ac (526,091 ha) of coastal and estuarine habitat in a network of 28 reserves located in 

22 States and Puerto Rico. The reserves consist of relatively pristine estuarine areas that contain 

key habitat for purposes of long-term research, environmental monitoring, education, and 

stewardship, and are protected from significant ecological change or developmental impacts (NERR 

System, 2011). The NERRs containing portions within the AOI are the Apalachicola, Rookery Bay, 

and Mission-Aransas (Table 4.7-1; Figure 4.7-2; Appendix E).

State-Designated Marine Protected Areas

There are numerous State-designated coastal MPAs located along the coastal boundary of 

the AOI that include State parks, resource conservation areas (e.g., nature preserves, aquatic 

preserves, natural areas, and wildlife management areas), sanctuaries, water quality protection 

areas, and historical areas (Figure 4.7-2). In addition, there are also areas in State-designated 

MPAs where fishery activities are prohibited or controlled (Table 4.7 1). In total, there are 53 Statedesignated MPAs that are within the AOI (Appendix E). Coastal and marine habitats and 

associated coastal and marine flora and fauna of these State-designated coastal MPAs are quite 

variable. For example, an MPA protecting a shipwreck would have the water column, soft sediment 

benthic habitat, and fish and invertebrates species associated with the structure and seafloor. An 

MPA for a designated protective speed zone for manatees would have the water column; manatees; 

seagrass beds providing forage; soft sediment substrates; and associated fishes, flora, and other 

fauna. The following paragraphs provide a description of the managing State agency and the 

primary focus of the State designation.

The Florida Department of Environmental Protection manages 36 of these MPAs, the 

majority of which were designated for protection of natural heritage areas, and one for sustainable 

production. The vast majority of these MPAs are Outstanding Florida Waters, although many are 

also State Parks and aquatic preserves. Outstanding Florida Waters are water features designated 

by the Florida Department of Environmental Protection as worthy of special protection of their natural 

attributes and have special restrictions on any new activity that would lower water quality or 

otherwise degrade the body of water.

The FWC manages eight of these MPAs, with four of the MPAs as wildlife management 

areas and the other four as designated protection zones for the Florida manatee. The Florida 
Gulf of Mexico G&G Activities Programmatic EIS 4-267

Division of Historical Resources manages four MPAs that were designated to preserve underwater 

archaeological regions of cultural significance, which are composed of shipwrecks.

Louisiana has five State-designated eligible MPAs, which includes one refuge and four 

wildlife management areas, three of which are also game preserves. All of these MPAs are 

managed by the Louisiana Department of Wildlife and Fisheries.

4.7.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, the IPFs that may impact MPAs within the AOI include (1) active 

acoustic sound sources (e.g., airguns; non-airgun HRG sources such as high-resolution boomers, 

sparkers, and CHIRP subbottom profilers; SBESs and MBESs; and side-scan sonars), (2) trash and 

debris, (3) seafloor disturbance, (4) drilling discharges, and (5) accidental fuel spills. In considering 

the potential impacts to the associated MPAs, it is important to make the distinction between the AOI 

and the EPA, CPA, and WPA. The total AOI area of 689,166 km2 (266,089 mi2

) includes 45,630 km2

(17,618 mi2

) of State waters outside of the planning area boundaries, so the total planning areas in 

Federal waters considered for MPAs is 643,536 km2 (248,471 mi2

). The potential direct impacts 

considered here include the planning areas only and does not include State waters that extend to 

3 nmi (3.5 mi; 5.6 km) offshore Louisiana, Mississippi, and Alabama and 9 nmi (10.4 mi; 16.7 km) 

offshore Texas and Florida, which are beyond OCS lease block area boundaries and where the 

proposed BOEM-authorized G&G activities would not occur. This distinction is important because 

the EPA does not include the Florida Keys and other sensitive shallow-water habitats within State 

waters 3 or 9 nmi from shore. In these areas outside of the planning areas but within the AOI, for 

MPAs, only potential indirect impacts propagating into the area from proposed activities are 

considered.

The MPAs, or portions of the MPAs, within the planning areas include 15 of the 94 NOAA 

MPAs listed for the AOI (Table 4.7-1) located offshore (Figure 4.7-1). The MPAs within the planning 

areas are all in Federal waters and include the De Soto Canyon Conservation Area, East Florida 

Coast Conservation Area, Florida Keys NMS, Florida Middle Grounds HAPC, FGBNMS, Madison 

and Swanson MPA, McGrail Bank HAPC, Pelagic Sargassum Habitat Restricted Area, Pulley Ridge 

HAPC, Reef Fish Longline and Buoy Gear Reserve Area, Reef Fish Stressed Area, Steamboat 

Lumps, Stetson Bank HAPC, Tortugas Marine Reserves, and West and East FGBs HAPC.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact level categories. In contrast, the analysis 

of impacts associated with Alternatives B through G are organized by alternative-specific mitigation 

measures and how each of these measures may reduce impact levels.

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27), based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 
4-268 Description of the Affected Resources and Impact Analysis

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For MPAs, the below 

significance criteria have been used to evaluate the level of impact for each IPF.

Nominal impacts to MPAs would include those where little to no measurable impacts are 

observed or expected. Nominal impacts to MPAs would include those where G&G activities would 

produce little to no damage to natural communities, would not reduce the multiple resource uses 

within MPAs, and would not alter the physical, chemical, or biological environment within MPAs.

Minor impacts to MPAs would include those that are detectable but not severe or extensive. 

Minor impacts to MPAs would include impacts arising from any activity that results in low levels of 

damage to the ecological function or reduction in the biological productivity of natural communities or 

multiple resource uses within MPAs.

Moderate impacts to MPAs would be detectable and extensive within the MPA, but not 

severe or localized. Moderate impacts to MPAs would include impacts arising from any activity that 

results in moderate damage to the ecological function or reduction in the biological productivity of 

natural communities or multiple resource uses within MPAs.

Major impacts to MPAs would be detectable, extensive within the MPA, and severe if no 

mitigation measures were enacted upon the permitted activities. Major impacts to MPAs would 

include any G&G activity that results in severe destruction of, or damage to, key biological resources 

in MPAs; or severe, extensive damage to the ecological function or reduction in the biological 

productivity of natural communities or multiple resource uses within MPAs.

4.7.2.1 Impacts of Routine Activities

4.7.2.1.1 Active Acoustic Sound Sources

Because seismic airgun surveys authorized by BOEM are only expected to cover the 

planning areas and not the entire AOI, only the 10 offshore MPAs could be exposed to direct noise 

produced by seismic survey activity. Six of the 10 MPAs are within the EPA (i.e., the Madison and 

Swanson MPA, Steamboat Lumps, Pulley Ridge HAPC, De Soto Canyon Close Area, portions of the 

Tortugas Marine Reserve, and Florida Middle Grounds), one is within the WPA (i.e., the Stetson 

Bank HAPC), one is within the CPA (i.e., the McGrail Bank HAPC), and two are shared by the WPA 

and CPA (i.e., the West and East FGBs HAPC and FGBNMS). The other 88 MPAs within the AOI 

but outside of the planning areas could be exposed to secondary impacts through propagated noise 

from adjacent seismic airgun and electromechanical sound source surveys.

The G&G activities under the oil and gas program would account for most of the airgun and 

electromechanical sources (Table 3.2-8) and would have the greatest potential for affecting MPAs. 

Additionally, because of the nature of renewable energy and marine mining projects (i.e., their 

limited spatial distribution), activities associated with the oil and gas program have a greater 
Gulf of Mexico G&G Activities Programmatic EIS 4-269

potential to affect MPAs through noise. However, it is not clear how close these various G&G 

activities may come to MPAs.

National Marine Sanctuaries

The FGBNMS offshore Texas and Louisiana is located within the WPA and CPA. The 

NOAA is currently considering expanding the boundaries of the FGBNMS (80 FR 5699) (Chapter

4.7.1). While seismic surveys employing airgun arrays and hydrophone streamers are not currently 

precluded from conducting surveys over deepwater MPAs, other G&G activities may not be allowed 

in designated No Activity Zones. No Activity Zones restrict any bottom-disturbing activities and 

cover most of the FGBs but do not limit noise sources within the No Activity Zone. BOEM will not 

issue permits for bottom-disturbing activities where prohibited. However, the G&G permittees for 

those permits that BOEM does issue are required to consult with the FGBMS prior to the start of 

operations. The permittee must remove all mooring buoys before and replace them immediately 

after operations. In addition, the permittee must announce the time that the mooring buoys will not 

be available in a Notice to Mariners. The NMSA provides several tools for protecting designated 

NMSs, including the authority to issue regulations for each sanctuary and the system as a whole. 

The ONMS regulations, codified at 15 CFR part 922, prohibit specific kinds of activities, describe and 

define the boundaries of the NMSs, and set up a system of permits to allow the conduct of certain 

types of activities. Permits are required for any action that includes activities otherwise prohibited by 

sanctuary regulations.

As discussed in Appendix B, the ONMS and BOEM will initiate consultation. The NMSA 

and ONMS’ regulations have a broad definition of the terms “sanctuary resource” and “injury”; 

“sanctuary resources” are living and non-living attributes of the sanctuary and “injury” includes 

disruption of ecological processes inclusive of physical, physiological, and behavioral modifications. 

Therefore, sound-producing activities (such as seismic surveys) proposed in or near the boundaries 

of an NMS would initiate consultation between ONMS and BOEM to stipulate additional mitigation 

measures, if any, that are recommended to reduce or eliminate injury to sanctuary resources. 

Measures such as setback distances will be determined prior to any sound-producing surveys by 

BOEM and in consultation with ONMS pursuant to Section 304(d) of the NMSA.

All authorizations for seismic surveys (those involving airguns as an acoustic source) would 

include a survey protocol that specifies underwater noise mitigation measures for protected species, 

including an acoustic exclusion zone, ramp-up requirements, visual monitoring by PSOs, and array 

shutdown requirements as outlined in Appendix B. While an NMS may be avoided so no airguns 

and streamers directly transit within its bounds, noise from 2D seismic and other types of surveys 

may still reach animals within an NMS. Non-airgun HRG surveys are expected to use 

electromechanical sources such as side-scan sonars; boomer, sparker, and CHIRP subbottom 

profilers; and SBESs or MBESs. Some AUVs can use combinations of sources for HRG data 

collection. All authorizations for non-airgun HRG surveys would include specific protocol 

requirements as outlined in Appendix B. Recreational resources within an NMS may be affected by 

seismic noise as well (Appendix E). In an NMS that allows multiple uses such as recreational 
4-270 Description of the Affected Resources and Impact Analysis

fishing or diving, such activities would not be affected by noise from G&G activities except for 

potential impacts to target recreational fish species in close proximity to noise sources that could 

result in a localized, temporary displacement and/or disruption of feeding. Operators would be 

expected to follow the Guidance for Activities In or Near National Marine Sanctuaries (15 CFR part 

922), which provides a listing of prohibited or otherwise regulated activities for NMSs. Based on the 

rationale presented and the transient noise from survey vessels conducting seismic airgun surveys, 

no impacts to recreational fishing and diving in the FGBNMS and the FKNMS would be expected, 

where fishing and diving is allowed. 

Depending on the type of survey and associated source levels and sound propagation, the 

distance from seismic survey project areas to an NMS, and sensitive species and habitats contained 

therein, noise-generating activities from G&G surveys could affect benthic communities 

(Chapter 4.5.2.1), marine mammals (Chapter 4.2.2.2), sea turtles (Chapter 4.3.2.2), marine and 

coastal birds (Chapter 4.6.2.1), and fisheries resources and EFH (Chapter 4.4.2.1), any or all of 

which may be present within an NMS.

Benthic Communities: Impacts to benthic organisms from noise generated from G&G 

surveys are not likely to occur except in the unlikely event of airgun use at very close range (e.g., in 

very shallow water), where sufficient acoustic energy reaches the seafloor to cause physiological 

damage. As discussed in Chapter 4.5.2.1, soundscape orientation of pelagic larvae will be nominal

due to the transient and temporary nature of the proposed activities. At the depths where the 

FGBNMS occurs (>135 m [443 ft]), only nominal impacts to benthic communities from G&G survey 

noise are expected. Based on study results of invertebrate communities following airgun exposure, 

detectable impacts on hard/live bottom, coral, or chemosynthetic communities are not expected from 

active acoustic sound sources (Chapter 4.5.2.1). Furthermore, only nominal, localized impacts to 

benthic communities within the FGBNMS are expected. No overall changes in species composition, 

community structure, and ecological functioning of communities within the NMS is expected. The 

only other NMS within the AOI, i.e., the Florida Keys NMS, is outside of the planning areas and is 

located in shallow coastal waters off South Florida. Impacts to benthic communities, including those 

found within each NMS of the planning areas and the AOI, from active acoustic sound sources 

would be nominal. 

Marine Mammals: As discussed in Chapter 4.2.2.2, the effects of active acoustic sound 

sources (e.g., airgun noise) on marine mammals include reduction of prey availability, stress, 

disturbance, behavioral responses, auditory masking, TTS or PTS (hearing loss), non-auditory 

physiological effects, and mortality. Seismic survey (airgun) noise has the potential to disrupt normal 

activities of sensitive species and, in rare instances, inflict physiological damage. Direct effects may 

include pathological (i.e., injury), physiological (e.g., stress), and behavioral changes. Given 

sufficient exposure within an NMS, marine mammals may vacate the area, experience TTS, 

experience masking of biologically relevant sounds, or be completely unaffected (Chapter 4.2.2.1). 

From the analysis in Chapter 4.2.2.1, impacts to marine mammals from active acoustic sound 

sources would be minor for HRG and shallow-penetration airgun surveys and moderate for deeppenetration airgun surveys.
Gulf of Mexico G&G Activities Programmatic EIS 4-271

Sea Turtles: As discussed in Chapter 4.3.2.2, the effects of active acoustic sound sources 

(e.g., airgun noise) on sea turtles include behavioral responses, masking of biologically important 

sounds, TTS (hearing loss), PTS, and mortality. Seismic survey (airgun) noise has the potential to 

disrupt normal activities of sensitive species and, in rare instances, inflict physiological damage. 

Direct effects may include pathological (i.e., injury), physiological (e.g., stress), and behavioral 

changes. Given sufficient exposure within an NMS, sea turtles would vacate the area, experience 

TTS, experience masking of biologically relevant sounds, or be completely unaffected 

(Chapter 4.3.2.1). Due to the mobile nature of the seismic airgun surveys, the temporary surveying 

of small areas of the seafloor relative to the overall area, the propensity of sea turtles to move away 

from noise that is affecting them, and the expectation that no lethal impacts or population-level 

impacts from PTS auditory injuries would occur, it is expected that impacts to sea turtles from active 

acoustic sound sources would range from nominal (for HRG surveys) to minor (for airgun surveys) 

(Chapter 4.3.2.1).

Fisheries and EFH: As discussed in Chapter 4.4.2.1, the effects of active acoustic sound 

sources (e.g., airgun noise) on fishes include behavioral responses, masking of biologically 

important sounds, TTS (hearing loss), physiological effects, and mortality. Seismic survey (airgun) 

noise has the potential to disrupt normal activities of sensitive species and, in rare instances, inflict 

physiological damage. Direct effects may include pathological (i.e., injury), physiological (e.g., 

stress), and behavioral changes. Given sufficient exposure within an NMS, affected fish species 

would vacate the area, experience short-term threshold shift, experience masking of biologically 

relevant sounds, or be completely unaffected (Chapter 4.4.2.1). While accounting for the potential 

to disrupt spawning aggregations or schools of important prey species, the mobile nature of the 

seismic airgun surveys, the temporary surveying of small areas of the seafloor relative to the overall 

area, and the propensity of fishes to move away from noise that is affecting them, suggest that the 

impacts would range from nominal (for HRG surveys) to minor (for airgun surveys) (Chapter

4.4.2.1).

Marine and Coastal Birds: With only a few exceptions, marine and coastal birds would not 

be impacted within NMSs. Seabirds’ prey may temporarily exhibit avoidance of an area where 

surveys are being performed but this is expected to be limited to a very small portion of a bird’s 

foraging range. Consideration also has to be given to migrating seabirds and the temporary 

displacement of species from preferred feeding grounds due to active acoustic surveying activities. 

Therefore, impacts to marine and coastal birds, including those few species that may use the NMSs 

of the AOI, from active acoustic sound sources would range from nominal to minor, depending on 

timing and location (Chapter 4.6.2.1).

Conclusion: In summary, the extent of impacts to sensitive receptors in NMSs would 

depend largely on their distance from the noise sources associated with G&G surveys. Overall, 

such impacts from transient activities would be expected to be nominal in terms of potential impacts 

on sensitive populations within each NMS. Seismic survey airgun and electromechanical source 

noise intruding into a NMS would likely have no more than temporary effects on those NMS 

protected resources. Nominal impacts are expected for most NMS resources, including benthic 
4-272 Description of the Affected Resources and Impact Analysis

communities and marine and coastal birds, nominal to minor impacts for fisheries resources and 

EFH and sea turtles, while minor to moderate impacts are expected for marine mammals.

Offshore Marine Protected Areas

Within the National System of MPAs, nine federally designated offshore MPAs located 

offshore Texas, Louisiana, and Florida are within the planning areas. Five offshore MPAs (i.e., 

Pulley Ridge, Stetson Bank, McGrail Bank, West and East FGBs, and Florida Middle Grounds) are 

designated and established by NMFS as HAPCs with fishing restrictions applied. Additionally, 

Madison and Swanson MPA and Steamboat Lumps MPA are deepwater marine reserves offshore 

Florida, established to protect spawning aggregations of groupers. Fishes in the Federal fishery 

management areas, sea turtles, and marine mammals that may be present could be affected by 

noise from G&G activities. The impacts from noise produced by seismic activities within these MPAs 

will be primarily on fishes due to the focus of the management areas. The extent of impacts on 

fishes in these MPAs would depend largely on their distance and orientation from the noise source 

and the sensitivity to propagated frequencies. As seismic airgun surveys are not precluded from 

deepwater MPAs, airgun and electromechanical noise may affect fishes within these areas. Noise 

generated from any G&G activities is expected to produce minor impacts on fishes in offshore 

MPAs if surveys are conducted within the bounds of each MPA. While fishes are the primary 

resources for which these offshore MPAs were established, other resources such as benthic 

organisms, marine birds, and marine mammals are present also; these are unlikely to be 

significantly affected by airgun and electromechanical noise from survey activities, as discussed in 

the previous section, impacts to each resource within offshore MPA’s are expected to mirror the 

impacts for resources within the NMS, as discussed above. However, an expanded sanctuary with a 

presidential prohibition on oil and gas activities may lessen the potential impacts slightly.

Other Federal Offshore Marine Protection Areas

Management areas could be affected by noise from G&G activities. The extent of impacts 

from noise generated by seismic activities on resources of concern in these MPAs would depend 

largely on their distance and orientation from the noise source and sensitivity to the propagated 

frequencies. As seismic airgun surveys are not precluded from the fishery management areas, 

airgun and electromechanical noise may affect fishes within these areas. Noise generated by G&G 

activities are expected to produce minor impacts on fishes in fishery management areas if surveys 

are conducted within the areas. As discussed in the previous section, impacts to each resource 

within the MPA are expected to mirror the impacts for resources within the NMS.

Coastal Marine Protected Areas

National System coastal/State-designated MPAs located within the AOI are mostly outside 

and inshore of the planning areas and would not be directly impacted with the exception of a portion 

of the Tortugas Marine Reserve located in the EPA. The principal conservation focus of the 

88 MPAs outside of the planning areas but within the AOI includes 11 for sustainable production, 

4 for cultural heritage, and 73 for natural heritage (Table 4.7-1). Twenty of the coastal MPAs have 
Gulf of Mexico G&G Activities Programmatic EIS 4-273

at least 49 percent of their area included in the AOI, with the remaining 68 MPAs with smaller areas 

within or bordering the AOI. Sound propagation in shallow, coastal areas can be highly complex 

with some noise being quickly absorbed and other noise being augmented through reflection and 

refraction; therefore, impacts are highly site and source specific. Noise from G&G surveys could 

affect fishes (Chapter 4.4.2.1), marine mammals (Chapter 4.2.2.1), sea turtles (Chapter 4.3.2.1), 

and benthic communities (Chapter 4.5.2.1) in these coastal MPAs. The extent of impacts to fishes 

is expected to be minor. The extent of impacts to sea turtles and marine mammals in coastal MPAs 

would depend largely on their distance from the noise sources associated with G&G surveys and 

species sensitivities to the propagated frequencies. The impacts from G&G survey noise will likely 

depend largely on the context in which the sound is received while the animals are utilizing the MPA. 

Impacts to sea turtles and marine mammals are expected to range from nominal to moderate

depending on the timing, location, and the sound transmission properties of the survey. Moderate

level impacts to marine mammals could result from deep-penetration airgun surveys. Impacts to 

benthic organisms, primarily invertebrates, in these coastal MPAs from noise generated by G&G 

surveys are expected to be nominal. 

4.7.2.1.2 Trash and Debris

Most trash generated offshore during G&G activities is associated with galley and offshore 

food service operations. Although companies operating offshore have developed and implemented 

trash and debris reduction and improved handling practices in recent years to reduce the amount of 

offshore trash that could be lost into the marine environment, trash and debris would be generated 

during G&G activities that could be accidentally lost overboard. A discussion of the effects of debris 

lost overboard to benthic communities is provided in Chapter 4.5.2.1, which indicates that debris 

from exploratory drilling results in a minimal (i.e., nominal) impact to the benthic environment. 

Debris deposited in areas of extensive soft bottom provided artificial hard substrate that resulted in 

epifaunal colonization and attracted fishes.

NTL 2015-BSEE-G03 would be required for all survey vessels performing work within U.S. 

jurisdictional waters (i.e., they are required to comply with Federal regulations, including MARPOL 

73/78, and all authorizations for shipboard surveys would include guidance for marine debris 

awareness); only accidental loss of trash and debris is anticipated. Impacts from trash and debris 

generated by survey vessels, sampling, test well drilling, and other G&G-related activities on MPAs 

and the resources within would be nominal. 

4.7.2.1.3 Seafloor Disturbance

The G&G sampling, drilling, and anchor placement disturb the seafloor. A discussion of 

seafloor disturbances from sampling, drilling, and anchor placement is provided in Chapter 4.5.2.1. 

Activities with the potential for seafloor disturbance include sampling by vibracoring, geologic core, 

and grab samplers; use of jet probes and piezocone penetrometers; the laying of OBNs, OBC, and 

vertical cable; the drilling of shallow test wells; and the placement and retrieval of bottom-founded 

monitoring buoys. Proposed activities under Alternative A include bottom sampling, drilling, and 

anchoring. Bottom sampling could be conducted in all three planning areas.
4-274 Description of the Affected Resources and Impact Analysis

BOEM would require site-specific information regarding potential sensitive benthic 

communities prior to approving any G&G activities involving seafloor-disturbing activities or 

placement of bottom-founded equipment or structures in the planning areas. No Activity Zones 

within NMSs restrict any bottom-disturbing activities and cover most of the FGBs. BOEM has 

designated specific benthic locations, including deepwater benthic communities and biologically 

sensitive underwater features and areas (NTLs 2009-G40 and 2009-G39, respectively), for 

avoidance in the planning areas. Additionally, other known hard/live bottom areas, deepwater coral 

areas, and chemosynthetic community sites are likely areas for avoidance. All authorizations for 

G&G surveys proposed within or near these areas would be subject to review to facilitate avoidance 

(Chapter 2.1.2.4). BOEM would use this information to ensure that physical impacts to sensitive 

benthic communities are avoided. Therefore, seafloor-disturbing impacts to sensitive benthic 

communities within MPAs are expected to be nominal. 

4.7.2.1.4 Drilling Discharges

Drilling discharges may occur during the drilling of test wells; however, as discussed in 

Chapter 3.3.1.8, BOEM would require site-specific information prior to approving any G&G activities 

involving seafloor-disturbing activities, including drilling, in the planning areas. In addition, an 

NPDES permit would be required from the USEPA prior to any drilling activities. The installation of 

test wells associated with G&G survey activities is unlikely to be allowed in MPAs. An extensive 

discussion of impacts of drilling discharges from oil and gas operations is provided in 

Chapter 4.5.2.1. During the drilling process, drilling fluid and cuttings discharged would accumulate 

on the seafloor, causing changes in sediment grain size and affecting the benthic community by 

burial and smothering, anoxia, and sediment toxicity. Excess cement slurry released at the seafloor 

during casing installation would cause burial and smothering of benthic organisms around the 

wellbore. Soft bottom sediments disturbed by cuttings, drilling fluids, and cement slurry eventually 

would be recolonized through larval settlement and migration from adjacent areas (Chapter 4.5.2.1). 

The areal extent of impacts from drilling discharges during the proposed action would be small; a 

typical effect radius of 500 m (1,640 ft) would be expected. Therefore, drilling discharge impacts to 

sensitive benthic communities within MPAs are expected to be nominal. 

National Marine Sanctuaries

No seafloor-disturbing activities would be permitted in the FKNMS. Seafloor-disturbing 

activities proposed within the boundaries of FGBNMS would not be permitted within a No Activity 

Zone. No Activity Zones restrict any bottom-disturbing activities and cover most of the FGBNMS. 

Discharges can be allowed under FGBNMS regulations outside of No Activity Zones (including 

remaining area within the sanctuary) as long as they are “shunted” to within 10 m (33 ft) of the 

seafloor. This regulation limits the potential of the discharges being transported to sensitive habitats 

within the sanctuary, but it can result in the accumulation of toxic materials in the sediments around 

the base of the platform (Kennicutt, 1995). Seafloor-disturbing activities proposed within FGBNMS 

but outside No Activity Zones, or outside the FGBNMS but near its boundaries, may be assigned a 

setback distance as condition of a permit/COA to be determined at the time the action is under 

review by BOEM and in coordination with the ONMS. Further, if BOEM finds that injury to sanctuary 
Gulf of Mexico G&G Activities Programmatic EIS 4-275

resources are likely to occur as a result of permitted discharges within or near the FGBNMS, BOEM 

will consult with ONMS under NMSA Section 304(d). Sanctuary consultation would result in ONMS 

providing recommended alternatives to BOEM to reduce or eliminate such impacts. Given levels of 

restriction and opportunities for mitigation, limited discharges of drilling fluids and cuttings are likely 

to occur within or in close proximity to NMS waters. The required permitting and consultation 

process will allow for site-by-site assessment of activities and the mitigation of potential impacts; 

therefore, no impacts to FKNMS are expected from drilling discharges, and discharge impacts to 

FGBNMS are expected to be nominal. 

Offshore Marine Protected Areas

As discussed in Chapter 3.3.1.8, BOEM would require site-specific information prior to 

approving any G&G activities involving seafloor-disturbing activities, including drilling, in the planning 

areas. In addition, an NPDES permit would be required from the USEPA prior to any drilling 

activities. The installation of test wells associated with G&G survey activities would be restricted 

within No Activity Zones. Outside of No Activity Zones, approval will occur only after BOEM’s review 

of the required site-specific information, and sensitive habitats would be avoided. Through the 

permit and review process, there will be limited, and managed, seafloor disturbance within 

designated fisheries management areas and HAPCs. Therefore, no impacts from drilling 

discharges would be expected to benthic communities, submerged archaeological resources, 

fisheries resources and EFH, sea turtles, and marine mammals in offshore HAPCs.

Other Federal Fishery Management Areas

If drilling is not precluded in other federally designated offshore MPAs where there are 

existing restrictions on certain types of fishing activities, drilling discharges could affect the resources 

within those MPAs. Because of the small footprint relative to the total area of the remaining MPAs, 

impacts from drilling discharges would be expected to be nominal in terms of potential impacts on 

benthic communities, while no impacts to submerged archaeological resources, fisheries resources 

and EFH, sea turtles, and marine mammals are expected from drilling discharges in these MPAs.

Coastal Marine Protected Areas

As discussed in Chapter 3.3.1.8, BOEM would require site-specific information prior to 

approving any G&G activities involving seafloor-disturbing activities, including drilling, in the planning 

areas. In addition, an NPDES permit would be required from the USEPA prior to any drilling 

activities. The majority of the coastal MPAs occur onshore, and the offshore portion (which is within 

the AOI and as such is included) is limited to extreme shallow waters where O&G activities are 

unlikely. Therefore, drilling discharges would not be expected to affect coastal MPAs.

4.7.2.1.5 Routine Activities Impact Conclusions

In summary, the extent of active acoustic sound source impacts to resources in NMSs would 

depend largely on their distance from the noise sources associated with G&G surveys. Overall, 

such impacts from transient activities would be expected to be nominal in terms of potential impacts 
4-276 Description of the Affected Resources and Impact Analysis

on sensitive populations within each NMS. Seismic survey airgun and electromechanical source 

noise intruding into an NMS would likely have no more than temporary effects on those protected 

resources that are characteristic of each NMS. Nominal impacts from active acoustic sounds are 

expected for most NMS resources, including benthic communities and marine and coastal birds. 

Impacts to marine mammals are expected to range from minor to moderate, while nominal to 

minor impacts are expected for fisheries resources and EFH and sea turtles. Impacts from trash 

and debris, seafloor disturbance, and drilling discharges are expected to be nominal due to existing 

regulations and protections in place.

4.7.2.2 Accidental Fuel Spills

An accidental event such as a ship collision could result in a release of diesel fuel. Such 

spills are not expected to be extensive, would dissipate rapidly, and would likely affect only 

organisms in the immediate vicinity of the accident. Based on USCG spill statistics, a spill scenario 

was developed in Chapter 3.3.2.1 that assumes a diesel spill of 1.2 to 7.1 bbl. Spills occurring at 

the ocean surface would disperse and weather. Volatile components of the fuel would evaporate. 

Diesel and other fuels used for operation of survey vessels are light and would float on the surface of 

the water.

The likelihood of a fuel spill during seismic airgun surveys or other G&G activities in proximity 

to MPAs is considered remote. The potential for impacts from a diesel fuel spill would depend 

greatly on the size and location of a spill, meteorological conditions at the time, and speed for 

employing cleanup plans and equipment. Such small fuel spills are unlikely to significantly affect 

biota, habitats, and submerged cultural resources within each NMS, Federal fishery management 

areas (offshore MPAs), and coastal MPAs. Adult fishes within an MPA would be less susceptible to 

the effects of spilled fuel or oil than would eggs and larvae. Limited spills of fuel are unlikely to affect 

benthic communities, sea turtles, and marine mammals in MPAs because fuel would dissipate 

rapidly and would likely affect only organisms in the immediate vicinity of the accident. Marine and 

coastal birds could possibly contact spilled fuel, which could cause injury or mortality. However, 

while individual birds may be oiled during a diesel spill, such impacts would be unlikely to affect 

marine and coastal birds at a population level. However, the threatened and endangered bird 

species (i.e., Piping Plover, Roseate Tern, and Red Knot) are very susceptible to oiling. In terms of 

all biological resources potentially affected, accidents involving G&G survey vessels and resulting in 

a fuel spill would range from nominal to moderate: 

• Moderate: marine and coastal birds; 

• Nominal to minor: marine mammals, sea turtles, and fish resources and EFH; 

and 

• Nominal: all other resources. 
Gulf of Mexico G&G Activities Programmatic EIS 4-277

4.7.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for MPAs are compared with the IPFs from each of 

the cumulative scenario components in order to focus this cumulative analysis on those activities 

that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G activity IPFs 

that are included in the cumulative assessment are the same as those assessed under routine 

activities and accidental events. The following analysis evaluates the incremental increase by IPF 

and provides a conclusion of the cumulative incremental increase within the AOI.

The G&G activities have been ongoing in the GOM for at least the past 30 years and it is 

reasonable to assume they will continue into the future; however, for the purpose of this 

Programmatic EIS, the cumulative analysis assesses a 10-year timeframe to coincide with the 

proposed action because it is not expected that G&G activities as a result of this analysis will have 

lasting effects or extend beyond the 10-year timeframe of this Programmatic EIS.

4.7.2.3.1 Noise

Active Acoustic Sound Sources

All G&G survey activities associated with all three program areas (i.e., oil and gas, 

renewable energy, and marine minerals) are included in the proposed action; therefore, G&G 

activities on the OCS are not included in the cumulative analysis but instead are addressed in the 

proposed action impact analysis (Chapter 4.2.2.1). Cumulative impacts are assessed in this 

analysis for the cumulative activities that produce active acoustic sound sources, including State 

waters oil and gas, commercial fishing, cable installation, military, and scientific research activities 

(Table 3.4-1).

The impacts from active acoustic sound sources to NMSs, offshore MPAs, and other Federal 

fisheries management areas would depend on the distance between the activities and the protected 

areas. With the use of mitigation measures under Alternative A, nominal to minor incremental 

increases in impacts from active acoustic sound sources are expected under the cumulative 

activities scenario within MPAs. The incremental increase to the cumulative impacts would range 

from nominal to minor, depending on the resources occurring within NMSs, offshore MPAs, and 

other Federal fisheries management areas.

4.7.2.3.2 Trash and Debris

Trash and debris may originate from diverse activities, both onshore and offshore. All 

mariners operating vessels in the GOM are expected to comply with regulations for the management 

of waste in inland, coastal, and offshore waters. Trash and debris would be generated during G&G 

activities that could be accidentally lost overboard, some of which could sink to the seafloor and 

harm benthic communities or wash up on beaches and shorelines potentially causing entanglement, 
4-278 Description of the Affected Resources and Impact Analysis

ingestion, and aesthetic impacts. Guidance similar to NTL 2015-BSEE-G03 (“Marine Trash and 

Debris Awareness and Elimination”) (USDOI, BSEE, 2012) would be required for all survey vessels 

performing work within U.S. jurisdictional waters (i.e., they are required to comply with Federal 

regulations including MARPOL 73/78 and all authorizations for shipboard surveys would include 

guidance for marine debris awareness); therefore, only accidental loss of trash and debris is 

anticipated. As discussed in Chapter 4.7.2.1, the proposed action under Alternative A would follow 

the same regulations and guidance, thus potentially adding a small amount of accidentally released 

trash and debris and resulting in nominal impacts to MPAs under the proposed action. A nominal

incremental increase in impacts to MPAs from trash and debris is expected under the cumulative

scenario.

4.7.2.3.3 Seafloor Disturbances

Seafloor-disturbing activities associated with the proposed action over the 10-year period are 

included in Table 3.2-8. The cumulative scenario includes activities that disturb the seafloor by 

anchoring, trenching, coring, trawling and bottom sampling from OCS activities, decommissioning, 

and the renewable and marine minerals programs. In addition, other activities in the AOI, such as 

State waters oil and gas, commercial fishing, dredging and material disposal activities, cable 

installation, military activities, and scientific research, can cause seafloor disturbances (Table 3.4-1). 

The projected area of seafloor disturbance (Table 3.2-8) is a very small fraction of the AOI and 

represents a limited area when compared with the projected bottom disturbance from the OCS oil 

and gas program activities during the 10-year period (Table 3.4-2). Because of the likely wide 

separation, the risk of cumulative impacts associated with the proposed action with similar 

cumulative activities will be nominal. While small numbers of bottom samples may be clustered in 

an area, the seafloor disturbed by each sample is small, and there will likely be a large separation 

between areas investigated using bottom samples.

As discussed in Chapter 4.7.2.1, impacts to MPAs from the proposed seafloor-disturbing 

activities would be nominal primarily due to minimal seafloor disturbances associated with the 

proposed action and the exclusion and protection requirements associated with MPAs that require 

review and consultation for activities within and near the boundaries of MPAs. The incremental 

increase in impacts to MPAs from seafloor disturbances under the cumulative scenario would be 

nominal. 

4.7.2.3.4 Drilling Discharges

Drilling discharges under the proposed action are expected to be minimal, resulting from one 

COST well and two shallow test wells (Chapter 3.3.1.9). Cumulative activities that contribute to 

drilling discharges are the OCS oil and gas program, and oil and gas activities in State waters. As 

shown in Table 3.4-2, the number of wells projected in the next 10 years for oil and gas activities is 

>5,000 wells. Based on the proposed action parameters and the review process, no direct impacts 

to MPAs would be expected from drilling discharges, and incremental increases from the proposed 

action to cumulative MPA impacts from drilling discharges under the cumulative scenario would be 

nominal. 
Gulf of Mexico G&G Activities Programmatic EIS 4-279

4.7.2.3.5 Cumulative Impact Conclusions

Overall, proposed activities would increase levels of noise within the AOI, resulting in 

sporadic increases in ambient noise levels during proposed G&G operations; however, impacts from 

active acoustic sound sources are expected to result in nominal to minor incremental increases in 

impacts to MPAs under the cumulative scenario. For trash and debris, seafloor disturbances, drilling 

discharges, and other impact-producing factors (such as hypoxia, military activities, fisheries, etc.), 

the proposed activities would contribute very little to the other activities occurring under cumulative 

scenario; thus, a nominal incremental increase in impacts is expected.

4.7.2.3.6 Accidental Fuel Spills

As discussed in Chapter 3.4, the AOI includes an active commercial shipping and marine 

transportation system, recreational vessel traffic, and an extensive system of offshore oil and gas 

production facilities. However, the potential for collision and product transfer fuel spills from vessels 

involved in the cumulative activities scenario is considered remote. Diesel and other fuels used for 

operation of vessels associated with the activities is light and would float on the sea surface where is 

it subjected to weathering, dispersion, and dissolution. Heavier fuels may be used in larger 

commercial vessels involved in marine transportation. Impacts to MPAs from survey vessel 

accidental fuel spills were determined to be nominal for the proposed action (Chapter 4.7.2.2). 

Incremental increases in impacts to MPAs from accidental fuel spills would be nominal. 

4.7.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.7.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative B on MPAs.

4.7.3.1 Impacts of Routine Activities

Impacts from active acoustic sound sources, trash and debris, seafloor disturbance, and 

drilling discharges for Alternative A are evaluated in Chapter 4.7.2.1. The additional mitigation 

measures will reduce the potential direct impacts to MPAs within the planning areas and the 

nearshore MPAs in State waters within the AOI but outside of the planning areas. The mitigation 

measures designed to reduce impacts to marine mammals and sea turtles (i.e., expansion of NTL 

2012-JOINT-G02, minimum separation distances, seismic restrictions in the EPA, and expanded use 

of PAM [Chapter 2.2]) would reduce impacts to those species occurring in MPAs. The MPA impacts 

were evaluated to be nominal to moderate, depending on the resource and IPF for Alternative A. 

The evaluation below considers the potential impact changes as a result of the mitigation measures 

included in Alternative B and are expected to remain as nominal to moderate for active acoustic 

sound sources across all resources. Impacts from trash and debris, seafloor disturbance, and 

drilling discharges would remain nominal for all resources under Alternative B.
4-280 Description of the Affected Resources and Impact Analysis

4.7.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to April 30)

Coastal waters seasonal restrictions for airgun surveys would not change the impacts to the 

FGBNMS, but they could reduce secondary impacts to the FKNMS. The offshore and coastal MPAs 

and the Fishery Management Areas (Figure 4.7-1) located within the restricted area would have 

reduced impacts from active acoustic sound and trash and debris. The secondary impacts of sound 

propagation from airguns into the Coastal MPAs (Figure 4.7-2) would be reduced from January 1 to 

April 30. Because the restriction does not limit seafloor disturbance or drilling discharges, the 

impacts from drilling related to G&G activities would remain as similar to those described in 

Alternative A.

4.7.3.1.2 Expanded PSO Program

Expanding the NTL would reduce the impacts to protected marine mammals (including 

manatees) and sea turtles that could be present in MPAs, resulting in decreased sound impacts. 

This expansion would not change the levels of impact from the other IPFs (i.e., trash and debris, 

seafloor disturbance, or drilling discharges).

4.7.3.1.3 Minimum Separation Distances

Active acoustic sound source impacts to species in MPAs located within the Areas of 

Concern (Figure 2.2-1) will be reduced by increasing the separation distances for simultaneous 

deep-penetration seismic airgun surveys to a distance of 40 km (25 mi). This mitigation would not 

change the levels of impact from the other IPFs (i.e., trash and debris, seafloor disturbance, or 

drilling discharges).

4.7.3.1.4 Seismic Restrictions in the Areas of Concern within the EPA

Active acoustic sound source impacts from deep-penetration seismic airgun surveys in the 

MPAs located within the Areas of Concern in the EPA (Figure 2.2-1 [portions of Areas 2 and 3, and 

all of Area 4]) will be reduced. This mitigation would not change the levels of impact from the other 

IPFs (i.e., trash and debris, seafloor disturbance, or drilling discharges).

4.7.3.1.5 Use of PAM Required

Requiring PAM during seismic surveying when visibility is reduced could reduce impacts to 

protected mammals in MPAs. This mitigation would not change the levels of impact from the other 

IPFs (i.e., trash and debris, seafloor disturbance, or drilling discharges).

4.7.3.1.6 Routine Activities Impact Conclusions

The evaluation considers the potential impact changes as a result of the mitigation measures 

included in Alternative B and are expected to remain as nominal to moderate for active acoustic 

sound sources. Moderate level impacts to marine mammals could result from deep-penetration

airgun surveys. Impacts from trash and debris, seafloor disturbance, and drilling discharges would 

remain nominal for all resources under Alternative B.
Gulf of Mexico G&G Activities Programmatic EIS 4-281

4.7.3.2 Accidental Fuel Spills

Under Alternative B, impacts from accidental fuel spills on MPAs and the associated 

resources would be very similar to those evaluated for Alternative A (Chapter 4.7.2.2). The analysis 

concluded that the likelihood of a fuel spill during G&G activities in proximity to an MPA is remote. 

The small volume assumed from accidental fuel spills would have insignificant population effects on 

MPAs. However, some species occurring within MPAs may be susceptible to oiling, and individuals 

could be affected.

Alternative B includes seasonal restrictions of G&G activities in coastal waters, reducing the 

potential impacts from accidental fuel releases on MPAs in proximity to coastal waters. Overall, 

accidental fuel spill impacts for Alternative B would be the same as Alternative A and would range 

between nominal and moderate: 

• Moderate: marine and coastal birds; 

• Nominal to minor: marine mammals, sea turtles, and fish resources and EFH; 

and

• Nominal: all other resources. 

4.7.3.3 Cumulative Impacts

Impact analyses presented in Chapters 4.7.3.1 and 4.7.3.2 determined that activities 

projected to occur under Alternative B would result in nominal to moderate impacts to MPAs, 

depending on the IPF and resources occurring within the MPAs.

Mitigation measures for the proposed action under Alternative B are described in 

Chapter 2.2 and summarized in Chapter 4.7.3.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.7.2.3). Some of the additional mitigation 

measures included in Alternative B, such as the expansion of the PSO program and PAM 

requirement during periods of reduced visibility, would reduce the associated impacts on marine 

mammals in and around MPAs. Other mitigation measures associated with this alternative, 

including seasonal coastal water restrictions for surveying and additional airgun seismic survey 

restricted areas, will reduce seismic surveying and vessel activities within portions of the AOI to 

minimize potential impacts from active acoustic sound sources, trash and debris, and accidental fuel 

spills. Increasing vessel separation distances during simultaneous airgun seismic surveys under 

Alternative B could reduce the cumulative impacts common to MPA IPFs from active acoustic sound 

sources. While these mitigation measures would reduce the cumulative impacts from the associated 

IPFs, they would not significantly change the degree of impacts from the proposed action on MPAs. 

Incremental increase in impacts to MPAs would remain nominal to minor for Alternative B.
4-282 Description of the Affected Resources and Impact Analysis

4.7.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.7.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative C on MPAs.

4.7.4.1 Impacts of Routine Activities

Impacts from active acoustic sound sources, trash and debris, seafloor disturbance, and 

drilling discharges for Alternative A are evaluated in Chapter 4.7.2.1. The additional mitigation 

measures will reduce the potential impacts for direct impacts to MPAs within the planning areas and 

the nearshore MPAs in State waters within the AOI but outside of the planning areas.

The evaluation below considers the potential impact changes as a result of the mitigation 

measures included in Alternative C and are expected to remain as nominal to moderate for active 

acoustic sound sources and accidental fuel spills across all resources. Impacts from trash and 

debris, seafloor disturbance, and drilling discharges would remain nominal for all resources under 

Alternative C.

4.7.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to May 31)

Coastal waters seasonal restrictions for airgun surveys would not change the impacts to the 

FGBNMS, but they could reduce secondary impacts to the FKNMS. The offshore and some coastal 

MPAs and the Fishery Management Areas (Figure 4.7-1) located within the restricted area would 

have reduced impacts from active acoustic sound and trash and debris. The secondary impacts of 

sound propagation from airguns into the Coastal MPAs (Figure 4.7-2) would be reduced from 

February 1 to May 31. Because the restriction does not limit seafloor disturbance or drilling 

discharges, the impacts would remain as described in Alternative A.

4.7.4.1.2 Expanded PSO Program

Expanding the NTL would reduce exposure of protected marine mammals (including 

manatees) and sea turtles that could be present in MPAs to sound, resulting in decreased acoustic 

impacts. This expansion would not change the levels of impact from the other IPFs (i.e., trash and 

debris, seafloor disturbance, or drilling discharges).

4.7.4.1.3 Use of PAM Required

Requiring PAM during seismic surveying when visibility is reduced could reduce impacts to 

protected vocalizing marine mammals within MPAs. Requirement of PSOs in all water depths would 

also reduce impacts to protected marine mammals within MPAs. However, these mitigation 

measures would not change the levels of impact from the other IPFs (i.e., trash and debris, seafloor 

disturbance, or drilling discharges).
Gulf of Mexico G&G Activities Programmatic EIS 4-283

4.7.4.1.4 Non-Airgun HRG Survey Protocol

Requiring HRG pre-survey clearance periods for marine mammals and sea turtles would 

reduce potential impacts to marine mammals and sea turtles in and around NMSs. In addition, 

requiring a PSO program 200-m (656-ft) exclusion monitoring zone for any HRG surveys could 

reduce potential impacts to protected species in and around NMSs, but the impacts would remain 

unchanged in other areas.

4.7.4.1.5 Routine Activities Impact Conclusions

The evaluation considers the potential impact changes as a result of the mitigation measures 

included in Alternative C and are expected to remain as nominal to moderate for active acoustic 

sound sources across all resources. Impacts from trash and debris, seafloor disturbance, and 

drilling discharges would remain nominal for all resources under Alternative C.

4.7.4.2 Accidental Fuel Spills

Under Alternative C, impacts from accidental fuel spills on MPAs and the associated 

resources would be very similar to those evaluated for Alternative A (Chapter 4.7.2.1). The analysis 

concluded that the likelihood of a fuel spill during G&G activities in proximity to MPAs is remote. The 

small volume assumed from accidental fuel spills would have insignificant population effects on 

MPAs. However, some species occurring within MPAs may be susceptible to oiling, and individuals 

could be affected.

Alternative C includes seasonal restrictions of G&G activities in coastal waters, reducing the 

potential impacts from accidental fuel releases on MPAs in proximity to coastal waters. Overall, 

accidental fuel spill impacts for Alternative C would be the same as Alternative A and would range 

between nominal and moderate: 

• Moderate: marine and coastal birds; 

• Nominal to minor: marine mammals, sea turtles, and fish resources and EFH; 

and

• Nominal: all other resources. 

4.7.4.3 Cumulative Impacts

Mitigation measures for the proposed action under Alternative C are described in 

Chapter 2.3 and summarized in Chapter 4.7.4.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.7.2.3). The additional mitigation 

measures in Alternative C may reduce impacts to marine mammals in and around MPAs to less than 

moderate levels. Overall, proposed activities would increase levels of noise within the AOI, resulting 

in sporadic increases in ambient noise levels during proposed G&G operations; however, impacts 

from active acoustic sound sources are expected to result in nominal to minor incremental 

increases in impacts to MPAs under the cumulative scenario. For trash and debris, seafloor 

disturbances, and drilling discharges, the proposed activities would contribute very little to the other 
4-284 Description of the Affected Resources and Impact Analysis

activities occurring under the cumulative scenario. While these mitigation measures would reduce 

the cumulative impacts from the associated IPFs, they would not significantly change the degree of 

incremental impacts from the proposed action. Incremental increase in impacts to MPAs would 

remain nominal to minor for Alternative C.

4.7.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.7.2). The additional mitigation measure under Alternative D would not 

reduce potential active acoustic impacts discussed in Alternatives A and C (Chapters 4.7.2.1 and 

4.7.4.1) and would remain nominal to moderate. This mitigation would not alter the impact levels to 

MPAs from trash and debris, seafloor disturbance, or drilling discharges, and impacts would remain 

nominal. Under Alternative D, impacts of an accidental fuel spill on MPAs would be as described 

for Alternatives A and C (Chapters 4.7.2.2 and 4.7.4.2) and would remain nominal to moderate. 

4.7.5.1 Impacts of Routine Activities

Impacts from active acoustic sound sources, trash and debris, seafloor disturbance, and 

drilling discharges are evaluated for Alternatives A and C in Chapters 4.7.2.1 and 4.7.4.1. The 

additional mitigation measures will reduce the potential direct impacts to MPAs within the planning 

areas and the nearshore MPAs in State waters within the AOI but outside of the planning areas. 

The MPA impacts were evaluated to be nominal to moderate, depending on species present and 

IPFs for Alternatives A and C.

Alternative D includes the mitigation measures included in Alternatives A and C, and adds a 

mitigation measure requiring shutdown for all marine mammals, except bow-riding dolphins. 

Shutdowns for marine mammals and sea turtles, except for bow-riding dolphins, could reduce 

acoustic impacts to these species in and around MPAs, but impacts are expected to remain nominal

to moderate across the AOI as a whole. This mitigation would not change the levels of impact from 

the other IPFs (i.e., trash and debris, seafloor disturbance, or drilling discharges).

4.7.5.2 Accidental Fuel Spills

Under Alternative D, impacts from accidental fuel spills on MPAs and their associated 

resources would be very similar to those evaluated for Alternative A (Chapter 4.7.2.1) and 

Alternative C (Chapter 4.7.4.1). The analysis concluded that the likelihood of a fuel spill during G&G 

activities in proximity to MPAs is remote. The small volume assumed from accidental fuel spills 

would have insignificant population effects on MPAs. However, some species occurring within 

MPAs may be susceptible to oiling and individuals could be affected.

Alternative D includes seasonal restrictions of G&G activities in coastal waters, reducing the 

potential impacts from accidental fuel releases on MPAs in proximity to coastal waters. Overall, 

accidental fuel spill impacts for Alternative D would be the similar to Alternative A and would range 

between nominal to moderate:
Gulf of Mexico G&G Activities Programmatic EIS 4-285

• Moderate: marine and coastal birds; 

• Nominal to minor: marine mammals, sea turtles, and fish resources and EFH; 

and

• Nominal: all other resources. 

4.7.5.3 Cumulative Impacts

Mitigation measures for the proposed action under Alternative D are described in 

Chapter 2.4 and summarized in Chapter 4.7.5.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.7.2.3). The additional mitigation 

measure included in Alternative D will reduce impacts to marine mammals in MPAs. While this 

additional mitigation measure will reduce the cumulative impacts from active acoustic sound 

sources, it will not significantly change the degree of incremental impact from the proposed action. 

Overall, proposed activities would increase levels of noise within the AOI, resulting in sporadic 

increases in ambient noise levels during proposed G&G operations; however, impacts from active 

acoustic sound sources are expected to result in nominal to minor incremental increases in impacts 

to MPAs under the cumulative scenario. For trash and debris, seafloor disturbances, and drilling 

discharges, the proposed activities would contribute very little to the other activities occurring under 

the cumulative scenario. Incremental increase in impacts to MPAs would remain nominal to minor

for Alternative D.

4.7.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.7.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative E on MPAs.

4.7.6.1 Impacts of Routine Activities

Impacts for active acoustic sound sources, trash and debris, seafloor disturbance, and 

drilling discharges are evaluated for Alternatives A and C in Chapters 4.7.2.1 and 4.7.4.1. The 

additional mitigation measures will reduce the potential impacts for direct impacts to MPAs within the 

planning areas and the nearshore MPAs in State waters within the AOI but outside of the planning 

areas.

Alternative E includes the mitigation measures included in Alternatives A and C, and includes 

a reduction of deep-penetration, multi-client activities by 10 percent or 25 percent, which may reduce 

acoustic impacts from these activities; however, overall impacts are expected to remain nominal to 

moderate for active acoustic sound sources across all resources in MPAs. Impacts from trash and 

debris, seafloor disturbance, and drilling discharges would remain nominal for all resources in MPAs 

under Alternatives E1 and E2.
4-286 Description of the Affected Resources and Impact Analysis

4.7.6.2 Accidental Fuel Spills

Under Alternative E, impacts from accidental fuel spills on MPAs and their associated 

resources would be very similar to those evaluated for Alternatives A and C (Chapters 4.7.2.1 and 

4.7.4.1). The analysis concluded that the likelihood of a fuel spill during G&G activities in proximity 

to a MPA is remote. The small volume assumed from accidental fuel spills would have insignificant 

population effects on MPAs. However, some species occurring within MPAs may be susceptible to 

oiling and individuals could be affected.

Alternative E includes a 10 percent or 25 percent reduction in deep-penetration, multi-client 

activity line miles that also would reduce the potential for accidental fuel releases by reducing 

associated vessel activity. Overall, accidental fuel spill impacts for Alternative E would be the same 

as Alternative A and Alternative C and would range between nominal and moderate: 

• Moderate: marine and coastal birds; 

• Nominal to minor: marine mammals, sea turtles, and fish resources and EFH; 

and

• Nominal: all other resources. 

4.7.6.3 Cumulative Impacts

Mitigation measures for the proposed action under Alternative E are described in 

Chapter 2.5 and summarized in Chapter 4.7.6.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.7.2.3). The reduction of deeppenetration, multi-client activities (in line miles) by 10 percent (Alternative E1) or 25 percent 

(Alternative E2) would reduce the extent, severity, and timing of active acoustic sound sources, 

vessel and equipment noise, vessel traffic, aircraft traffic and noise, and trash and debris; therefore, 

impacts for these IPFs would be incrementally decreased under Alternative E.

Impacts from the proposed action on MPAs were determined to result in nominal

incremental increases for the cumulative scenario activity components and their associated IPFs for 

Alternatives A and C (Chapters 4.7.2.3 and 4.7.4.3). The additional mitigation measure of 

decreasing deep-penetration, multi-client activity survey miles by 10 percent (Alternative E1) or 

25 percent (Alternative E2) from estimated levels in a calendar year would result in a reduction of 

potential impacts across the AOI as a whole. While this mitigation measure would reduce the 

cumulative impacts from the associated IPFs, it would not significantly change the degree of 

incremental impacts from the proposed action. Incremental increase in impacts to MPAs would 

remain nominal to minor for Alternatives E1 and E2.
Gulf of Mexico G&G Activities Programmatic EIS 4-287

4.7.7 Impacts – Alternative F (Alternative C Plus Area Closures)

Impacts to MPAs under Alternative F would be very similar to those described for 

Alternatives A and C (Chapters 4.7.2 and 4.7.4). The evaluation below considers the potential 

impact changes as a result of the mitigation measures included in Alternative F.

4.7.7.1 Impacts of Routine Activities

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.7.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative F on MPAs. The additional mitigation measures will 

reduce the potential direct impacts to MPAs within the four closure areas, including the Tortugas 

Marine Reserves and Dry Tortugas National Park, and secondary impacts to MPAs within a close 

distance of the closure areas.

Alternative F includes the mitigation measures included in Alternatives A and C, and includes 

four area closures where only non-airgun HRG surveys operating at frequencies >200 kHz can 

operate. The restriction within the EPA Closure Area will directly reduce acoustic impacts to pelagic 

fish in the area and reduce sound impacts to fish communities in nearby fishery management MPAs 

such as the Madison and Swanson MPA and Steamboat Lumps MPA. Impacts are expected to be 

reduced to nominal to minor for active acoustic sound sources and trash and debris across all 

resources due to the potential for these impacts to cross MPA boundaries and based on the impact 

levels determined for resources occurring within MPAs (e.g., marine mammals [Chapter 4.2.2.7]). 

While the reduction in activity may reduce the likelihood of impact, the resultant effect to the 

resources would not change. Impacts from seafloor disturbance and drilling discharges would be 

eliminated within the MPAs that are within the closure areas; however, potential impacts to 

resources within open MPAs would remain. Therefore, the impacts expected from seafloor 

disturbance and drilling discharges for all resources within MPAs would remain nominal under 

Alternative F.

4.7.7.2 Accidental Fuel Spills

Under Alternative F, impacts from accidental fuel spills on MPAs and their associated 

resources would be very similar to those evaluated for Alternative A (Chapter 4.7.2.1) and 

Alternative C (Chapter 4.7.4.1). The analysis concluded that the likelihood of a fuel spill during G&G 

activities in proximity to an MPA is remote. The small volume assumed from accidental fuel spills 

would have insignificant population effects on MPAs. However, some species occurring within 

MPAs may be susceptible to oiling and individuals could be affected.

Alternative F’s area closures of the CPA Closure Area, EPA Closure Area, Dry Tortugas 

Closure Area, and Flower Gardens Closure Area would reduce the potential for accidental fuel 

releases by reducing the associated vessel activity in those areas. Overall, accidental fuel spill 

impacts to resources within MPAs for Alternative F would be the similar to those for Alternative A 

and Alternative C and would range between nominal and moderate: 
4-288 Description of the Affected Resources and Impact Analysis

• Moderate: marine and coastal birds; 

• Nominal to minor: marine mammals, sea turtles, and fish resources and EFH; 

and 

• Nominal: all other resources. 

4.7.7.3 Cumulative Impacts

Impact analyses presented in Chapters 4.7.7.1 and 4.7.7.2 determined that activities 

projected to occur under Alternative F would result in nominal to moderate impacts to MPAs, 

depending on the IPF and resources occurring within the MPAs.

Mitigation measures for the proposed action under Alternative F are described in Chapter

2.6 and summarized in Chapter 4.7.7.1. A detailed impacts assessment under the cumulative 

scenario is provided in Alternative A (Chapter 4.7.2.3). Mitigation measures under Alternative F are 

similar to Alternative C with the addition of area closures in four areas: the CPA Closure Area; the 

EPA Closure Area; the Dry Tortugas Closure Area; and the Flower Gardens Closure Area. As 

discussed in Chapter 4.7.7.1, trans-boundary IPFs would be nominally affected by additional MPA 

closures. Additional mitigation closures in Alternative F would eliminate seafloor impacts within 

specific MPAs but would not change the overall cumulative impact scenario for MPAs throughout out 

the AOI. Impacts from the proposed action on MPAs were determined to result in nominal

incremental increases for the cumulative scenario activity components and their associated IPFs for 

Alternatives A and C (Chapters 4.7.2.3 and 4.7.4.3). The additional Alternative F mitigation 

measure of area closures in the CPA Closure Area, EPA Closure Area, Dry Tortugas Closure Area, 

and Flower Gardens Closure Area would result in associated percentage reductions in potential 

impacts to common MPA IPFs from seafloor disturbance and drilling discharges but not a one-to-one 

reduction in potential impacts from active acoustic sound sources, trash and debris, and accidental 

fuel spills due to the distributed nature of these IPFs. Therefore, while this mitigation measure would 

reduce the cumulative impacts from some associated IPFs, it would not significantly change the 

degree of incremental impacts from the proposed action. Incremental increase in impacts to MPAs 

would remain nominal to minor for Alternative F.

4.7.8 Impacts – Alternative G (No New Activity Alternative)

The IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.7.2).

4.7.8.1 Impacts of Routine Activities

Impacts for active acoustic sound sources, trash and debris, seafloor disturbance, drilling 

discharges, and accidental fuel spills are evaluated for Alternative A in Chapter 4.7.2.1. Alternate G 

will reduce the potential and/or have no impact for overall impacts to MPAs within the AOI because 

the proposed level of activity would likely not be proximal to MPAs; therefore, impacts are expected 

to range from no impact to nominal under Alternative G.
Gulf of Mexico G&G Activities Programmatic EIS 4-289

4.7.8.2 Impacts of Accidental Fuel Spill

Under Alternative G, impacts from accidental fuel spills on MPAs and their associated 

resources would be very similar to those evaluated for Alternative A (Chapter 4.7.2.1). The analysis 

concluded that the likelihood of a fuel spill during G&G activities in proximity to an MPA is remote. 

The small volume assumed from accidental fuel spills would have insignificant population effects on 

MPAs. However, some species occurring within MPAs may be susceptible to oiling and individuals 

could be affected. Alternative G reduces the potential for accidental fuel releases from no impact to 

nominal by having the associated reduction in vessel activity (Chapter 2.7).

4.7.8.3 Cumulative Impacts

Impacts from the proposed action on MPAs were determined to result in nominal

incremental increases for the cumulative scenario activity components and their associated IPFs for 

Alternative A (Chapter 4.7.2.3). Alternative G activity reductions would result in no impacts to 

nominal impacts from active acoustic sound sources, trash and debris, seafloor disturbance, drilling 

discharges, and accidental fuel spills. This mitigation measure would reduce the cumulative impacts 

from the associated IPFs; therefore, incremental increase in impacts to MPAs would be no impact

to nominal for Alternative G under the cumulative scenario.

4.8 SARGASSUM AND ASSOCIATED COMMUNITIES

4.8.1 Description of the Affected Environment

Sargassum mats comprise two species of brown algae: Sargassum natans and S. fluitans. 

Each species is entirely pelagic, spending its entire life cycle on the ocean surface. Sargassum

reproduces by vegetative fragmentation (LaPoint, 1995), and its movement is controlled by surface 

winds and currents (Appendix E; Section 8). Sargassum can be found alone or aggregated into 

large mats or long windrows and can be randomly spread across the ocean surface or found along 

current- or wind-driven boundaries.

The life history of Sargassum in the GOM is part of a larger cycle that includes the midAtlantic Ocean and the Caribbean Sea (Frazier et al., 2015). This cycle begins in the Sargasso Sea 

where Sargassum remains year-round. However, winds and currents move some of this Sargassum

south into the Caribbean Sea and eventually into the GOM via the Yucatan Channel. Once in the 

GOM, it moves into the western area where it uses nutrient inputs from coastal rivers, including the 

Mississippi River, for growth. As Sargassum abundance increases, plants will continue to travel east 

during the summer months; however, a large quantity of plants will travel into the nearshore where 

they will be deposited on coastal beaches. Sargassum deposition on Gulf Coast beaches is 

important because Sargassum facilitates dune stabilization and provides a pathway for nutrient and 

energy transfer from the marine environment to the terrestrial environment (Webster and Linton, 

2013). Eventually, the plants moving east will be incorporated into the Gulf Stream where they 

return to the Sargasso Sea. Throughout this cycle, plants will continue to grow, die, and reproduce. 

When a plant dies, it can sink to the seafloor, transporting nutrients and resources to the seafloor 

(Coston-Clements et al., 1991; Parr, 1939; Wei et al., 2012). Although the cycle continues year-
4-290 Description of the Affected Resources and Impact Analysis

round, the rapid growth of Sargassum populations in the western GOM typically occurs during the 

spring/summer of the year (Gower et al., 2006; Gower and King, 2008; Gower and King, 2011). 

Estimates suggest that between 0.6 and 6 million metric tons of Sargassum are present annually in 

the GOM, with an additional 100 million metric tons exported to the Atlantic basin (Gower and King, 

2008; Gower and King, 2011, Gower et al., 2013). The spatial expanse of this life history facilitates 

the rapid recovery from episodic environmental perturbations because of the remote probability that 

any single event could impact the entire spatial distribution.

In 2010, Sargassum was present in the area of surface oiling resulting from the Deepwater 

Horizon oil spill. During the months following the spill, studies documented direct exposure of 

Sargassum to oil throughout the time surface oil was present. This evidence comes from 

observations of direct oiling during the spill response and observations of Sargassum within the 

oiling footprint (Deepwater Horizon Natural Resource Damage Assessment Trustees, 2016).

The Final PDARP/PEIS injury assessment estimated the lost area of Sargassum that 

resulted from direct oiling and the foregone growth that resulted from this exposure. This estimate 

states that up to 23 percent of the Sargassum in the northern GOM was lost due to direct exposure 

to Deepwater Horizon oil (Deepwater Horizon Natural Resource Damage Assessment Trustees, 

2016). The total loss of Sargassum, including foregone area from lost growth, was estimated to be 

11,100 km2 (4,286 mi2

) (Deepwater Horizon Natural Resource Damage Assessment Trustees, 

2016). However, once the spill subsides, the pelagic habitat would quickly return to normal. The 

pelagic habitat far from shore is also far from land-based sources of pollution. Only part of the 

Sargassum stocks would be affected; algae not affected by the spill would continue to grow normally 

and repopulate the habitat. Since Sargassum has a seasonal cycle of growth in the summer and 

reduction in the winter, populations in the winter following a catastrophic oil spill may be similar to 

populations of any other year. With this pattern, recovery from the effects of a catastrophic oil spill is 

expected within 1-2 growing seasons. For example, after the Deepwater Horizon oil spill, 

Sargassum populations had returned to comparable abundance the following summer (Powers 

et al., 2013). Additional information pertaining to this resource and NMFS’ determination of the 

effects of the Deepwater Horizon oil spill may be found in the Final PDARP/PEIS (Deepwater 

Horizon Natural Resource Damage Assessment Trustees, 2016).

Pelagic Sargassum mats provide habitat for fauna, including >100 species of fish and over 

100 species of invertebrates such as crabs, shrimp, and mollusks, as well as 4 species of sea turtles 

and many marine birds (Coston-Clements et al., 1991). Epiphytic algae (a group of microscopic 

algae that grow on the surface of marine plants), encrusting hydroids, bryozoans, and tubeworms 

are also associated with these communities.

The habitat and community provided by Sargassum mats is important to the life histories of 

many species of pelagic, littoral, and benthic fishes, providing them with substrate, protection from 

predation, and access to food in the open sea (Dooley, 1972). Wells and Rooker (2004a) 

documented the abundance of both estuarine and pelagic fish species, indicating that Sargassum
Gulf of Mexico G&G Activities Programmatic EIS 4-291

may serve as an important means of transport of larval and juvenile species between offshore and 

inshore waters.

Four species of sea turtles have been documented in association with Sargassum in the 

GOM, i.e., the loggerhead, green, hawksbill, and Kemp’s ridley, specifically post-hatchling and early 

juvenile life stages. The four species of sea turtles have been observed actively foraging within the 

mats, resting and drifting while concealed by the mats, or diving below the mats (Witherington et al., 

2012). Sargassum has also been identified as a critical habitat for the loggerhead sea turtle (Caretta 

caretta) (Federal Register, 2014a).

The invertebrate community that inhabits Sargassum includes both mobile and sessile 

species. Common invertebrates include hydroids, anthozoans, flatworms, bryozoans, polychaetes, 

gastropods, nudibranchs, bivalves, cephalopods, pycnogonids, isopods, amphipods, copepods, 

decapod crustaceans, insects, and tunicates. Shrimps and crabs compose the bulk of invertebrates 

and are a major food source for Sargassum-associated fishes (Dooley, 1972).

4.8.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, the IPFs that may impact Sargassum within the AOI include vessel 

traffic, vessel discharges, trash and debris, and accidental fuel spills. As discussed in Chapter

4.8.1, Sargassum can be found in mats of varying size and length, and is temporally and spatially 

patchy throughout the GOM.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact level categories. In contrast, the analysis 

of impacts associated with Alternatives B through G are organized by alternative-specific mitigation 

measures and how each these measures may reduce impact levels.

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For Sargassum and 

associated communities, the below significance criteria have been used to evaluate the level of 

impact for each IPF.

Nominal impacts to Sargassum and associated communities would include those where little 

to no measurable impacts are observed or expected. No serious damage to Sargassum and 

associated fauna is expected to occur. Nominal impacts also would include limited, short-term 

physical displacement (e.g., breaking up of mats and Sargassum being pushed aside).
4-292 Description of the Affected Resources and Impact Analysis

Minor impacts to Sargassum and associated communities would include those that are 

detectable but are not severe or extensive. Minor impacts to Sargassum also would include shortterm physical displacement of Sargassum mats that would not adversely affect the population or 

associated fauna.

Moderate impacts to Sargassum and associated communities would be detectable and 

extensive but not severe. Moderate impacts to Sargassum would include serious mechanical 

damage from G&G-related vessel propellers to Sargassum and injury to associated fauna. 

Moderate impacts also would include extended physical displacement of Sargassum mats. The 

viability or continued existence of affected Sargassum populations would not be threatened, 

although some impacts may be irreversible.

Major impacts to Sargassum would be detectable, extensive, and severe. Major impacts to 

Sargassum and associated communities would include severe mechanical damage from propellers 

sufficient to cause extensive mortality to Sargassum plants and associated communities; such 

damage would be sufficient to adversely affect the population. Major impacts to Sargassum also 

would include long-term (or permanent) physical displacement of the species to the extent that the 

long-term survivability of the species may be adversely affected.

4.8.2.1 Impacts of Routine Activities

4.8.2.1.1 Vessel Traffic

Under Alternative A, all G&G survey activities are performed from vessels, with the exception 

of remote sensing conducted via aircraft and satellites; therefore, most survey activities could impact 

Sargassum and associated communities from vessel traffic. The primary potential impact to 

Sargassum and associated communities from vessel traffic associated with G&G surveys is the 

physical displacement of Sargassum mats as vessels and towed equipment pass through large 

mats. Towed equipment may temporarily snag Sargassum and may require retrieval of equipment 

as needed to clean off Sargassum, depending on the amount of fouling. Sargassum will collect on 

cables and slide down the cable to a collection point, creating a cluster that causes drag and 

vibration on the equipment and cables. The subsurface equipment (e.g., airguns and HRG sources) 

is less likely to become fouled than the surface towed equipment (e.g., receivers, streamers, and 

hydrophones). Displaced Sargassum mats would likely re-form once the vessel has passed via 

surface winds, ocean currents, and gyres. Mechanical damage to Sargassum from passing through 

propellers is not expected to be extensive as much of the Sargassum would be pushed aside as the 

vessel passes. There is a possibility of Sargassum becoming impinged in cooling water intakes on 

vessels. Based on this analysis, impacts to Sargassum and associated communities from G&G 

vessel traffic would be nominal. Vessel traffic in the GOM is relatively high, and G&G survey 

vessels would add minimal additional traffic.

Species associated with, or dependent upon, the mats as habitat could be affected by vessel 

traffic moving through the mats. Sea turtles within Sargassum mats are at risk for survey vessel 

collision; however, collision risk from G&G vessel traffic does not differ from the risk associated with 
Gulf of Mexico G&G Activities Programmatic EIS 4-293

any other vessel movement within the AOI (Chapter 4.3.2). For larger turtles, regulations and 

guidance (e.g., NTL 2016-BOEM-G01, “Vessel Strike Avoidance and Injured/Dead Protected 

Species Reporting”) would further mitigate this risk. Smaller turtles, fish, and invertebrate species 

associated with Sargassum mats would likely not be affected by G&G survey vessel traffic. At the 

slow operating speeds of a G&G survey (<4 kn [5 mph]), most organisms would be displaced by the 

vessel hull, pushing them out of harm’s way.

4.8.2.1.2 Vessel Discharges

Under Alternative A, all G&G survey activities are performed from vessels, with the exception 

of remote sensing, which is conducted via aircraft and satellites; therefore, most survey activities 

could impact Sargassum and associated communities by vessel discharges. Vessel discharges 

could include bilge, ballast, and sanitary and domestic waste (Chapter 3.3.1.6). All routine 

discharges will be conducted in accordance with all established regulations and standards, including 

33 CFR § 151.10, 33 CFR part 151 subpart D, 40 CFR part 140, 33 CFR part 159, and 33 U.S.C. §§ 

1251 et seq. Given the widespread distribution of Sargassum and the size of the AOI, operational 

discharges would likely affect a very small percentage of the population. There is a possibility that 

exotic, and potentially harmful, organisms may be transferred and introduced from ballast water 

discharges (SAFMC, 2002; Trott et al., 2011), which could interact with Sargassum, possibly 

providing an environment where a new species could thrive and a mechanism of transportation to 

new habitats as Sargassum moves from the Atlantic Ocean into the Caribbean Sea and eventually 

into the GOM. 

Because Sargassum distribution is widespread and is temporally and spatially patchy 

throughout the AOI, it could come in contact with operational discharges; however, the waxy coating 

on Sargassum may prevent any effect from a short-term exposure to discharges (USDOI, BOEM, 

2012a). Considering the ratio of the affected area (immediately surrounding the survey vessel) to 

the entire AOI, and even to the larger area inhabited by Sargassum, only a small percentage of the 

total Sargassum population would directly contact operational discharges; therefore, impacts are 

expected to be nominal. 

Species associated with or dependent upon the Sargassum mats as habitat are not expected 

to be affected by vessel discharges.

4.8.2.1.3 Trash and Debris

All survey vessels performing work within U.S. jurisdictional waters are required to comply 

with Federal regulations and implement MARPOL 73/78. Within MARPOL Annex V, “Regulations for 

the Control of Pollution by Garbage from Ships,” as implemented by 33 CFR part 151, are 

requirements designed to protect the marine environment from various types of garbage generated 

on-board vessels. In addition, all authorizations for shipboard surveys would include guidance for 

marine debris awareness (NTL 2015-BSEE-G03, “Marine Trash and Debris Awareness and 

Elimination”). Therefore, the amount of trash and debris dumped offshore would be expected to be 
4-294 Description of the Affected Resources and Impact Analysis

minimal as only accidental loss of trash and debris is anticipated, some of which could float on the 

water surface.

The G&G survey activities generate trash comprised of paper, plastic, wood, glass, and 

metal. Most trash is associated with galley and offshore food service operations. However, over the 

last several years, companies operating offshore have developed and implemented trash and debris 

reduction and have improved handling practices to reduce the amount of offshore trash that could be 

lost into the marine environment. These trash management practices include replacing Styrofoam 

cups and dishes for those made of paper and ceramic, recycling offshore trash, and transporting and 

storing supplies and materials in bulk containers when feasible. These changes have resulted in a 

reduction of accidental loss of trash and debris from vessels.

Human-generated litter, including plastics and debris, is found in the surface waters of all of 

the world’s oceans and is documented in the GOM within pelagic Sargassum mats (Wei et al., 

2012). Several mechanisms concentrate pelagic Sargassum and anthropogenic debris (especially 

tar and plastics) in surface convergence zones, including surface currents and wind (Thiel and 

Gutow, 2005). While trash and debris may collect within Sargassum mats, such debris has not been 

documented to affect the algae. Because Sargassum has a temporally and spatially patchy 

distribution throughout the AOI, only a portion of the entire population would come in contact with 

trash and debris. No measureable impact would occur to Sargassum; therefore, impacts would be 

nominal. 

Species associated with or dependent upon Sargassum mats as habitat could be affected by 

trash and debris within the mats. Hatchling sea turtles may be found within Sargassum mats, which 

are rich in prey and provide shelter (Hirth, 1997; USDOC, NMFS and USDOI, FWS, 2008). 

Sargassum habitat is designated as critical habitat for the Northwest Atlantic Ocean DPS of the 

loggerhead sea turtle (79 FR 39855). Trash and debris within the mats may be mistaken as food or 

entanglement could occur. The complete analysis of potential impacts to sea turtles is provided in 

Chapter 4.3.2. Many commercially and recreationally important fish species associate with 

Sargassum at some point in their life cycle and could be affected through ingestion or entanglement 

in trash and debris (Chapter 4.4.2). Invertebrate communities within Sargassum mats would not be 

negatively affected by trash and debris. Sessile invertebrate attachment to biotic versus abiotic 

substrata is dependent upon biological factors such as temperature, feeding biology, and 

reproductive biology, as well as characteristics of the substratum such as complexity, surface, and 

size. Mobile invertebrates typically are highest on macroalgae (Sargassum) and lowest on abiotic 

substrata (Thiel and Gutow, 2005); however, certain species may prefer abiotic substrata (Winston, 

1982).

4.8.2.1.4 Routine Activities Impact Conclusions

Because the majority of G&G survey activities are performed using vessels, such activities 

could impact Sargassum and associated communities. Vessel traffic and its associated towed 

equipment can break apart free-floating mats of Sargassum in the survey area; vessel discharges 
Gulf of Mexico G&G Activities Programmatic EIS 4-295

may have an effect on water quality in the immediate area, which could indirectly affect Sargassum

and associated communities. In addition, there is a potential for impacts from the release of trash 

and debris to Sargassum and associated communities. Overall, impacts from all associated IPFs to 

Sargassum and associated communities under Alternative A would be nominal. 

4.8.2.2 Impacts of an Accidental Fuel Spill

An accidental event could result in the release of diesel or other fuel by a survey vessel. 

Based on USCG spill statistics, a spill scenario was developed in Chapter 3.3.2.1 that assumes a 

diesel spill volume of 1.2 to 7.1 bbl. Spills occurring at the ocean surface would disperse and 

weather. Volatile components of the fuel would evaporate rapidly. Diesel and other fuel used for 

operation of survey vessels is less dense than water and would float on the water surface. There is 

the potential for a small portion of the heavier fuel components to adhere to Sargassum and 

particulate matter in the upper portion of the water column and sink; there is also a potential for mats 

to become vectors for oiling of Sargassum inhabitants.

An accidental fuel spill could occur offshore or nearshore, and the impact to the Sargassum

and associated communities would depend on the amount of fuel spilled, the presence and amount 

of Sargassum, and the proximity of Sargassum directly contacted by the fuel spill (i.e., prior to any 

evaporation, dissipation, or weathering). It has been documented that Sargassum grows in the 

northwest GOM during the spring of each year, making the area a major nursery area for Sargassum

that supplies the Atlantic population (Gower and King, 2011). Thus, a fuel spill occurring in this 

region during the growing season likely will have a greater effect on the species than a fuel spill that 

occurs elsewhere at a different time. The yearly cycle of Sargassum reproduction in this area 

ensures that the species is resilient and able to recover annually without overall population-level 

effects (USDOI, BOEM, 2012a).

Powers et al. (2013) showed that the drifting Sargassum and its faunal associates could be 

negatively impacted by oil; however, they did not study the effects of diesel and other fuel 

specifically. The potential of a vessel collision occurring is quite low, with the likelihood of a resultant 

fuel spill even lower. An accidental event could result in the release of diesel or other fuel by a 

survey vessel, but such an event has a remote probability of occurring; if it did occur, it is anticipated 

that, because of the relatively small fuel spill size (1.2 to 7.1 bbl), the area of impact would be a very 

small portion of the AOI. Diesel remaining on the sea surface is expected to last for a day or less 

and have limited spatial extent. In addition, due to the widespread and temporally and spatially 

patchy distribution of Sargassum, most fuel spills would only contact a very small portion of the 

Sargassum population for a very short time, resulting in nominal impacts. 

Species associated with or dependent on Sargassum mats as habitat could be affected by 

an accidental release of diesel or other fuel. Sea turtles within a Sargassum mat that has been 

affected by a fuel spill may come in direct contact with the contaminant through ingestion of fouled 

prey, inhalation of air before diving, or exposure to sensitive tissues. Diesel and other fuel can 

adhere to sea turtle skin or shells. Sea turtles surfacing within or near an accidental release would 
4-296 Description of the Affected Resources and Impact Analysis

likely inhale petroleum vapors, causing respiratory stress. Ingested diesel fuel, particularly the 

lighter fractions, can be acutely toxic to sea turtles (Chapter 4.3.2.2). Fish eggs and larvae are most 

sensitive to oil spills (SAFMC, 2012), and those associated with a Sargassum mat that has been 

affected by a fuel spill would be impacted. Pelagic and epipelagic adults that forage at the ocean 

surface or within Sargassum mats that have been affected by a fuel spill would be most likely to be 

affected (Chapter 4.4.2.2). Diesel and other fuel may be toxic to invertebrates resident in 

Sargassum mats. Mobile invertebrates may avoid contaminated Sargassum by relocating; however, 

those that come in direct contact with diesel or other fuel likely would be impacted. However, the 

impact would be nominal given the relatively small size expected for an accidental fuel spill and the 

spatial extent of Sargassum coverage.

4.8.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for Sargassum are compared with the IPFs from 

each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI.

4.8.2.3.1 Vessel Traffic

As discussed in Chapter 4.8.2.1, impacts from G&G survey-related vessel traffic on 

Sargassum and associated communities would be nominal due to the minimal additional vessels 

associated with G&G survey activities and the nature of the interaction between Sargassum and 

vessels. 

Table 3.2-7 provides the number of estimated vessels required by survey type and by 

program area for the proposed action and includes 19,689 trips for support vessels and 1,008 trips 

for survey vessels. For cumulative vessel traffic, Table 3.4-2 provides a summary of projected 

support vessel operations anticipated for the oil and gas program and estimates that support vessel 

trips will range from 828,000 to 1,096,000 trips for the 10-year span of the cumulative scenario. 

Tables 3.4-7 and 3.4-8 provide vessel trip data for all vessels in the GOM. Exact numbers of 

cumulative vessel traffic associated with renewable energy- and marine mineral-related support 

activities are not known, but they are expected to be relatively small and spatially and temporally 

limited. Vessels are associated with all the activities under the cumulative scenario (Chapter 3.4). 

Overall, the contribution of vessel traffic from proposed G&G activities would be relatively small 

compared with the existing vessels in the AOI.

As discussed in Chapter 4.8.2.1, vessels could impact Sargassum communities slightly by 

their passage, damage from propellers, and possible impingement on cooling water intakes, but they
Gulf of Mexico G&G Activities Programmatic EIS 4-297

are expected to affect a small, localized portion of the overall Sargassum community. The additional 

vessels used for G&G surveys are not expected to contribute significantly to existing vessel traffic in 

the AOI. Therefore, cumulative impacts to Sargassum and associated communities from vessel 

traffic would result in a nominal incremental increase in the impact to Sargassum and associated 

communities under the cumulative scenario.

4.8.2.3.2 Vessel Discharges

As discussed in Chapter 4.8.2.1, impacts from G&G survey-related vessel discharges on 

Sargassum and associated communities would be nominal due to the temporally and spatially 

patchy distribution of Sargassum, the short-term and spatial extent of vessel discharges, and the 

adherence to regulations and standards.

The associated activities described in the cumulative scenario (Chapter 3.4) include the use 

of vessels and associated vessel discharges. Some activities utilize stationary platforms, barges, or 

drill ships that can produce similar effects to Sargassum and associated communities from runoff, 

sanitary facilities, and cooling water discharges. All discharges are strictly regulated, and offshore 

operators must adhere to existing regulations and standards for treating and managing discharges, 

thereby reducing the effect of discharges on water quality. The additional vessels used for G&G 

surveys are not expected to contribute significantly to existing vessel discharges in the AOI.

Because Sargassum distribution is widespread, it could come in contact with operational 

discharges; however, the waxy coating on Sargassum may prevent any effect from a short-term 

exposure to discharges (USDOI, BOEM, 2012a). Considering the ratio of the affected area 

(immediately surrounding the discharging vessel) to the entire AOI, and even to the larger area 

inhabited by Sargassum, it is clear that a small percentage of the total Sargassum population would

come in contact with operational discharges. Furthermore, the additional vessels used for G&G 

surveys are not expected to contribute significantly to existing vessel discharges occurring in the 

AOI. Therefore, cumulative impacts to Sargassum and associated communities from vessel 

discharges would result in a nominal incremental increase in the impact.

4.8.2.3.3 Trash and Debris

As discussed in Chapter 4.8.2.1, impacts on Sargassum and associated communities from 

trash and debris generated by G&G survey-related activities would be nominal due in part to 

adherence to existing requirements and guidance (e.g., NTL 2012-BSEE-G01 and MARPOL 73/78).

The cumulative activities described in Chapter 3.4 could introduce trash and debris. The 

offshore oil and gas industry’s adherence to the laws and regulations have greatly reduced their 

share of the trash and debris released in the GOM. The amount of trash and debris produced by 

G&G survey activities would be minimal, as only accidental loss of trash and debris is anticipated

and the additional vessels used for G&G surveys are not expected to contribute significantly to 

existing vessel traffic in the AOI. Therefore, cumulative impacts to Sargassum and associated 
4-298 Description of the Affected Resources and Impact Analysis

communities from trash and debris would result in a nominal incremental increase in the impact 

under the cumulative scenario.

4.8.2.3.4 Cumulative Impact Conclusions

In considering the level of contribution of vessel traffic, discharges, and trash and debris 

under the proposed action, it does not represent a large increase from existing conditions in the AOI, 

and overall nominal incremental impacts are expected. Further, the regulations and practices in 

place would further minimize the impacts from the proposed activities.

4.8.2.3.5 Accidental Fuel Spills

As discussed in Chapter 4.8.2.2, impacts on Sargassum and associated communities from 

an accidental fuel spill as a result of G&G survey-related activities would be nominal due to the 

remote probability of occurrence, the relatively small spill size (1.2 to 7.1 bbl), and the expectation 

that diesel would remain on the sea surface for a short period of time and have limited spatial extent. 

Furthermore, due to the widespread and patchy distribution of Sargassum, most fuel spills would 

only contact a small portion of the Sargassum population for a short time.

The activities under the cumulative scenario could result in an accidental release of diesel 

resulting from a vessel collision, similar to the scenario for the proposed action, and would be 

located in coastal waters. The severity of impacts to Sargassum and associated communities would 

vary depending on the location, timing, and size of the fuel spill relative to Sargassum distribution 

and could negatively impact Sargassum. 

With the use of AIS on large sea-going vessels, radar, and licensing of vessel captains, the 

potential of a vessel collision occurring is low, and the potential for a resultant fuel spill is even lower. 

An accidental fuel spill from a support or fishing vessel could occur, but the likelihood of such an 

event is remote. If an accidental fuel spill occurs, it is anticipated that the spill size would be 

relatively small and the area of impact would be a small portion of the AOI. Fuel spill size would 

depend on the type of vessel, the severity of the event, and whether the fuel storage is 

compartmentalized. The likelihood of a fuel spill resulting from a vessel collision is expected to be 

remote. Multiple and wide-ranging accidental fuel spills can occur as a result of extreme climatic 

events (i.e., hurricanes); therefore, fuel spill size and type can be variable. The G&G survey vessels 

would return to port in advance of a hurricane, and thus would not contribute to the potential for 

accidental fuel spills during a hurricane. Cumulative impacts to Sargassum and associated 

communities from an accidental fuel spill would result in a nominal incremental increase in the 

impact under the coastal developments component of the cumulative scenario.

4.8.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.8.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative B on Sargassum and associated communities.
Gulf of Mexico G&G Activities Programmatic EIS 4-299

4.8.3.1 Impacts of Routine Activities

Additional mitigation measures under Alternative B that would not change the extent, 

severity, or timing of G&G activities, and therefore related impacts to Sargassum and associated 

communities, include the minimum separation distance for simultaneous surveys, expansion of NTL 

2012-JOINT-G02 (inclusion of manatees and application to all deep-penetration seismic airgun 

surveys in all water depths), and the expanded use of PAM. As such, these mitigation measures will 

not be addressed in the following discussion.

4.8.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to April 30)

Alternative B would include a seasonal restriction area in Federal coastal waters of the GOM 

shoreward of the 20-m (66-ft) isobath between January 1 and April 30. No airgun surveys would be 

authorized within the closure area during this time.

The additional seasonal restriction for Federal coastal waters under Alternative B would 

change the timing of seismic airgun surveys in coastal areas and reduce the vessel traffic, vessel 

discharges, and trash and debris from these surveys in coastal areas during certain times of the year 

compared with Alternative A. As discussed in Chapter 4.8.2.1, impacts from vessel traffic, vessel 

discharges, and trash and debris to Sargassum and associated communities under Alternative A are 

already expected to be nominal. A change in survey timing in the additional closure area could 

reduce the impacts to Sargassum found in coastal areas, as these surveys would not occur within 

coastal waters between January 1 and April 30. However, the impacts to Sargassum and 

associated communities would be expected to remain nominal because the additional closure is not 

of sufficient duration to reduce impact levels. During the closure periods, the largest concentration 

of Sargassum remains outside the 20-m (66-ft) isobath. Additionally, once Sargassum is inside the 

20-m (66-ft) isobath, it is reaching the end of its lifecycle and will most likely be deposited on a 

beach.

4.8.3.1.2 Seismic Restrictions in the Areas of Concern within the EPA

Additional restrictions under Alternative B include the prohibiting of deep-penetration seismic 

airgun surveys within the portion of the Areas of Concern (Chapter 2.2.2) falling within the EPA. 

This restriction does not apply to surveys related to currently leased blocks, any portion of the area 

encompassed by EPA Lease Sale 226, or neighboring OCS lease blocks adjacent to permitted 

survey areas but within an otherwise off-limit area.

The additional area closure in portions of the EPA under Alternative B would change the 

location of seismic airgun surveys and could result in a localized reduction of vessel traffic, vessel 

and waste discharge, and trash and debris from these surveys compared with Alternative A. As 

discussed in Chapter 4.8.2.1, impacts from vessel traffic, vessel and waste discharge, and trash and 

debris to Sargassum and associated communities are expected to be nominal. A change in survey 

location restrictions in the additional area could reduce the impacts to Sargassum found in these 
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areas because these surveys would not occur there. The impacts to Sargassum and associated 

communities would be expected to remain nominal. 

4.8.3.1.3 Routine Activities Impact Conclusions

Because the majority of G&G survey activities are performed using vessels, such activities 

could impact Sargassum and associated communities. Vessel traffic and its associated towed 

equipment can break apart free-floating mats of Sargassum in the survey area; vessel discharges 

may have an effect on water quality in the immediate area, which could indirectly affect Sargassum

and associated communities. In addition, there is a potential for impacts from the release of trash 

and debris to Sargassum and associated communities. Overall, impacts from all associated IPFs to 

Sargassum and associated communities under Alternative B would be nominal. 

4.8.3.2 Impacts of an Accidental Fuel Spill

Under Alternative B, impacts of an accidental fuel spill on Sargassum and associated 

communities would be very similar to those analyzed for Alternative A in Chapter 4.8.2.2. The 

analysis concluded that a small fuel spill at the sea surface would result in nominal impacts. 

Alternative B would change the timing of certain surveys because of additional coastal seasonal 

restrictions and limits on concurrent seismic airgun surveys. Additionally, certain surveys would not 

be conducted within portions of the EPA. However, fuel spills from seismic survey vessels could 

occur in the closure areas during times outside the closure period. Also, fuel spills from other (nonseismic) survey vessels could occur during the closure period or in the EPA. A change in survey 

timing or type because of limits on concurrent seismic airgun surveys or a restriction of survey type 

would not substantially change the risk of a small fuel spill. Overall, the risk of a small fuel spill and 

the potential impacts to Sargassum and associated communities would be the same as under 

Alternative A and would be nominal. 

4.8.3.3 Cumulative Impacts

Impact analyses presented in Chapters 4.8.3.1 and 4.8.3.2 determined that activities 

projected to occur under Alternative B would result in nominal impacts to Sargassum and 

associated communities.

Mitigation measures for the proposed action under Alternative B are described in 

Chapter 2.2 and summarized in Chapter 4.8.3.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.8.2.3). Multiple mitigation measures 

under Alternative B would not change the extent, severity, or timing of activities in the proposed 

action; thus, the resultant impacts to Sargassum and associated communities also would not 

change. Mitigation measures under Alternative B that would change the timing and extent of 

activities in the proposed action include a seasonal restriction for the operation of airguns in Federal 

coastal waters and the prohibiting of deep-penetration seismic airgun surveys within portions of the 

EPA (Chapter 2.2.2).
Gulf of Mexico G&G Activities Programmatic EIS 4-301

The cumulative impact analysis identified nominal incremental increases in impacts from all 

IPFs under Alternative A (Chapter 4.8.2.3). The cumulative scenario would remain unchanged for 

Alternative B, and the associated impacts would remain the same. Alternative B would change the 

timing of seismic airgun surveys in certain areas; however, these coastal seasonal restrictions would 

not appreciably change the cumulative impacts described under Alternative A.

4.8.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.8.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative C on Sargassum and associated communities.

4.8.4.1 Impacts of Routine Activities

Additional mitigation measures under Alternative C that would not change the extent, 

severity, or timing of G&G activities, and therefore related impacts to Sargassum and associated 

communities, include the expanded use of PAM for seismic airgun surveys, the expanded use of 

PSOs, expansion of NTL 2012-JOINT-G02 (inclusion of manatees) for seismic airgun surveys, the 

pre-survey clearance period, and the expansion of NTL 2012-JOINT-G02 to include HRG surveys 

using airguns. As such, those mitigation measures will not be addressed in the following discussion.

4.8.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to May 31)

Alternative C includes a seasonal restriction in Federal coastal waters of the GOM 

shoreward of the 20-m (66-ft) isobath between February 1 and May 31. No airgun surveys would be 

authorized within the closure area during this time.

The additional seasonal restriction for Federal coastal waters under Alternative C would 

change the timing of seismic airgun surveys in coastal areas and reduce the vessel traffic, vessel 

discharges, and trash and debris from these surveys in coastal areas during certain times of the year 

compared with Alternative A. As discussed in Chapter 4.8.2.1, impacts from vessel traffic, vessel 

discharges, and trash and debris to Sargassum and associated communities are expected to be 

nominal. A change in survey timing in the additional closure area could reduce the impacts to 

Sargassum found in coastal areas, as these surveys would not occur within Federal coastal waters 

between February 1 and May 31. However, the impacts to Sargassum would be expected to remain 

nominal because the additional closure is not of sufficient duration to reduce impact levels.

4.8.4.1.2 Routine Activities Impact Conclusions

Because the majority of G&G survey activities are performed using vessels, such activities 

could impact Sargassum and associated communities. Vessel traffic and its associated towed 

equipment can break apart free-floating mats of Sargassum in the survey area; vessel discharges 

may have an effect on water quality in the immediate area, which could indirectly affect Sargassum

and associated communities. In addition, there is a potential for impacts from the release of trash 
4-302 Description of the Affected Resources and Impact Analysis

and debris to Sargassum and associated communities. Overall, impacts from all associated IPFs to 

Sargassum and associated communities under Alternative C would be nominal. 

4.8.4.2 Impacts of an Accidental Fuel Spill

Under Alternative C, impacts of an accidental fuel spill on Sargassum would be very similar 

to those analyzed for Alternative A in Chapter 4.8.2.2. The analysis concluded that a small fuel spill 

at the sea surface would result in nominal impacts. Alternative C would change the timing of certain 

surveys because of additional coastal seasonal restrictions and limits on concurrent seismic airgun 

surveys. Additionally, certain surveys will not be conducted within portions of the EPA. However, 

fuel spills from seismic survey vessels could occur in the closure areas during times outside the 

closure period. Also, fuel spills from other survey vessels (non-seismic) could occur during the 

closure period or in the EPA. A change in survey timing or survey type because of limits on 

concurrent seismic airgun surveys or a restriction of survey type would not substantially change the 

risk of a small fuel spill. Overall, the risk of a small fuel spill and the potential impacts to Sargassum

and associated communities would be the same as under Alternative A and would be nominal. 

4.8.4.3 Cumulative Impacts

Impact analyses presented in Chapters 4.8.4.1 and 4.8.4.2 determined that activities 

projected to occur under Alternative C would result in nominal impacts to Sargassum and 

associated communities, depending on the IPF.

Mitigation measures for the proposed action under Alternative C are described in 

Chapter 2.3 and summarized in Chapter 4.8.4.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.8.2.3). Most mitigation measures under 

Alternative C would not change the extent, severity, or timing of activities in the proposed action; 

thus, the resultant impacts to Sargassum and associated communities also would not change. The 

mitigation measures under Alternative C that would change the timing and extent of activities in the 

proposed action are a seasonal restriction for operation of airguns in Federal coastal waters.

The cumulative impact analysis identified nominal incremental increases in impacts from all 

IPFs under Alternative A (Chapter 4.8.2.3). The cumulative scenario would remain unchanged for 

Alternative C, and the associated impacts would remain the same. Alternative C would change the 

timing of seismic airgun surveys in certain areas; however, these coastal seasonal restrictions would 

not appreciably change the cumulative impacts described under Alternative A.

4.8.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative D are the same as for 

Alternative A (Chapter 4.8.2). The additional mitigation measure under Alternative D would not alter 

the impact levels to Sargassum and associated communities from vessel traffic, vessel discharges, 

or trash and debris, as described in Alternatives A and C (Chapters 4.8.2.1 and 4.8.4.1) and would 

remain nominal. Under Alternative D, impacts of an accidental fuel spill on Sargassum and 
Gulf of Mexico G&G Activities Programmatic EIS 4-303

associated communities would be as described for Alternatives A and C (Chapters 4.8.2.2 and 

4.8.4.2) and would remain nominal. 

4.8.5.1 Impacts of Routine Activities

Mitigation measures under Alternative D include all measures provided under Alternatives A 

and C but exclude bow-riding dolphins from the shutdown protocols during seismic surveys. 

Therefore, as discussed under Alternatives A and C (Chapters 4.8.2.1 and 4.8.4.1), all of the 

mitigation measures provided under Alternative D, except for the seasonal restriction for the 

operation of airguns in coastal waters, would not change the extent or severity of G&G activities and 

the associated impacts to Sargassum and associated communities.

The seasonal restriction for Federal coastal waters under Alternative D would change the 

timing of seismic airgun surveys in coastal areas and reduce the vessel traffic, vessel discharges, 

and trash and debris from these surveys in coastal areas during certain times of the year compared 

with Alternative A. As discussed in Chapter 4.8.2.1, impacts from vessel traffic, vessel and waste 

discharge, and trash and debris to Sargassum and associated communities are expected to be 

nominal. A change in survey timing in the additional closure area could reduce the impacts to 

Sargassum found in coastal areas, as these surveys would not occur within coastal waters between 

January 1 and April 30. However, the impacts to Sargassum and associated communities would be 

expected to remain nominal because the additional closure is not of sufficient duration to reduce 

impact levels.

4.8.5.2 Impacts of an Accidental Fuel Spill

Under Alternative D, impacts of an accidental fuel spill on Sargassum and associated 

communities would be very similar to those analyzed for Alternative A in Chapter 4.8.2.2. The 

analysis concluded that a small fuel spill at the sea surface would result in nominal impacts. 

Alternative D mitigation measures would not substantially change the risk of a small fuel spill. 

Overall, the risk of a small fuel spill and the potential impacts to Sargassum and associated 

communities would be the same as under Alternative A and would be nominal. 

4.8.5.3 Cumulative Impacts

Impact analyses presented in Chapters 4.8.5.1 and 4.8.5.2 determined that activities 

projected to occur under Alternative D would result in nominal impacts to Sargassum and 

associated communities, depending on the IPF.

Mitigation measures for the proposed action under Alternative D are described in 

Chapter 2.4 and summarized in Chapter 4.8.5.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.8.2.3). The mitigation measures are the 

same as described for Alternative C, with the addition of shutdown protocols during seismic 

operations for all marine mammals (except bow-riding dolphins). The addition of shutdown protocols 

for all marine mammals except bow-riding dolphins under Alternative D would not change the extent, 
4-304 Description of the Affected Resources and Impact Analysis

severity, or timing of activities in the proposed action; thus, the resultant impacts to Sargassum and 

associated communities also would not change and nominal incremental increases are expected.

4.8.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.8.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative E on Sargassum and associated communities.

4.8.6.1 Impacts of Routine Activities

The reduction of deep-penetration, multi-client activities by 10 percent or 25 percent under 

Alternative E would reduce the extent and severity of vessel traffic, vessel discharges, and trash and 

debris to Sargassum and associated communities. Impacts for these IPFs, therefore, would 

decrease incrementally under Alternative E from the analysis in Alternative A (Chapter 4.8.4.1); the 

overall level would be expected to remain nominal. 

4.8.6.2 Impacts of an Accidental Fuel Spill

Under Alternative E, impacts of an accidental fuel spill on Sargassum and associated 

communities would be very similar to those analyzed for Alternative A in Chapter 4.8.2.2. The 

analysis concluded that a small fuel spill at the sea surface would result in nominal impacts. 

Alternative E reduces survey activities; therefore, impacts would decrease incrementally. A change 

in the number of surveys would not substantially change the risk of a small fuel spill. Overall, the 

risk of a small fuel spill and the potential impacts to Sargassum and associated communities would 

be the same as under Alternative A and would be nominal. 

4.8.6.3 Cumulative Impacts

Impact analyses presented in Chapters 4.8.6.1 and 4.8.6.2 determined that activities 

projected to occur under Alternative E would result in nominal impacts to Sargassum and 

associated communities, depending on the IPF.

Mitigation measures for the proposed action under Alternative E are described in 

Chapter 2.5 and summarized in Chapter 4.8.6.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.8.2.3). The reduction of deeppenetration, multi-client activities (in line miles) by 10 percent (Alternative E1) or 25 percent 

(Alternative E2) would reduce the extent, severity, and timing of vessel traffic, vessel discharges, 

and trash and debris; therefore, impacts for these IPFs would be incrementally decreased under 

Alternative E. Overall, nominal incremental increases are expected under the cumulative scenario.
Gulf of Mexico G&G Activities Programmatic EIS 4-305

4.8.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.8.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative F on Sargassum and associated communities.

4.8.7.1 Impacts of Routine Activities

The additional reduction of activities under Alternative F would not change the extent or 

severity of vessel traffic, vessel discharges, and trash and debris generated from G&G activities in 

the majority of the AOI; consequently, the impacts to Sargassum and associated communities would 

be unchanged under Alternative F compared with Alternative A (Chapter 4.8.4.1).

Alternative F would require area closures in the CPA Closure Area, EPA Closure Area, Dry 

Tortugas Closure Area, and Flower Gardens Closure Area for seismic airgun survey operations. As 

discussed in Chapter 4.8.2.1, impacts from vessel traffic, vessel discharges, and trash and debris to 

Sargassum and associated communities are expected to be nominal. Thus, the impacts to 

Sargassum and associated communities would be expected to remain nominal. 

4.8.7.2 Impacts of an Accidental Fuel Spill

Under Alternative F, impacts of an accidental fuel spill on Sargassum and associated 

communities would be very similar to those analyzed for Alternative A in Chapter 4.8.2.2. The 

analysis concluded that a small fuel spill at the sea surface would result in nominal impacts. A 

change in the location of surveys would not substantially change the risk of a small fuel spill. 

Overall, the risk of a small fuel spill and the potential impacts to Sargassum and associated 

communities would be the same as under Alternative A and would be nominal. 

4.8.7.3 Cumulative Impacts

Impact analyses presented in Chapters 4.8.7.1 and 4.8.7.2 determined that activities 

projected to occur under Alternative F would result in nominal impacts to Sargassum and 

associated communities, depending on the IPF.

Mitigation measures for the proposed action under Alternative F are described in 

Chapter 2.6 and summarized in Chapter 4.8.7.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.8.2.3). Mitigation measures under 

Alternative F are similar to Alternative C with the addition of area closures in four areas: the CPA 

Closure Area; the EPA Closure Area; the Dry Tortugas Closure Area; and the Flower Gardens 

Closure Area. Most mitigation measures under Alternative F would not change the extent, severity, 

or timing of activities in the proposed action; thus, the resultant impacts to Sargassum and 

associated communities also would not change. These additional closures would reduce the extent 

and severity of impacts and therefore would decrease incrementally under Alternative F. 

Furthermore, as discussed under Alternative C (Chapter 4.8.4.3), these area closures and 
4-306 Description of the Affected Resources and Impact Analysis

restrictions would not appreciably change the cumulative impacts, and nominal incremental 

increases would be expected.

4.8.8 Impacts – Alternative G (No New Activity Alternative)

The IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.8.2).

4.8.8.1 Impacts of Routine Activities

Alternative G reduces the extent or severity of vessel traffic, vessel discharges, trash and 

debris, and accidental fuel spills generated from G&G activities in the majority of the AOI; 

consequently, the impacts to Sargassum and associated communities would be no impact; 

however, it is expected that without G&G surveys there could be an increase in exploratory drilling 

activity. In this case, impacts to Sargassum could be nominal. 

4.8.8.2 Impacts of Accidental Fuel Spill

Under Alternative G, impacts of an accidental fuel spill on Sargassum and associated 

communities would be very similar to those analyzed for Alternative A in Chapter 4.8.2.2. The 

analysis concluded that a small fuel spill at the sea surface would result in nominal impacts. 

Alternative G ceases survey activities; therefore, impacts would decrease substantially. Overall, the 

risk of a small fuel spill and the potential impacts to Sargassum and associated communities would 

be the same as under Alternative A and would be no impact to nominal. 

4.8.8.3 Cumulative Impacts

Impact analyses presented in Chapters 4.8.8.1 and 4.8.8.2 determined that activities 

projected to occur under Alternative G would result in no impacts to nominal to Sargassum and 

associated communities, depending on the IPF. The ceasing of activity for future G&G surveys 

requiring a permit/authorization from BOEM would not be adding an increase to the cumulative 

impacts because VSP and SWD are linked to current activity. Overall, the impacts to Sargassum

and associated communities would result in no impact to nominal incremental increases in impacts 

for Alternative G.

4.9 COMMERCIAL FISHERIES

4.9.1 Description of the Affected Environment

The AOI supports regionally and nationally important commercial fisheries. Information 

presented in this chapter is primarily summarized from the most recently published Fisheries 

Economics of the United States, 2014 (USDOC, NMFS, 2014). Commercial fisheries and the fishing 

industry is an important component of the economy of the GOM (Appendix E, Section 9). In 2012, 

the seafood industry in the five coastal states adjacent to the AOI supported nearly 160,000 jobs 

(Table 4.9-1), and the GOM’s seafood industry generated a total of $21.8 billion in sales. Florida 

generated the highest employment, sales, income, and value added impacts, generating 
Gulf of Mexico G&G Activities Programmatic EIS 4-307

82,000 jobs, $16.6 billion, $3.1 billion, and $5.5 billion, respectively. Louisiana and Texas had the 

highest landings revenue in 2012, with $331 million and $194 million, respectively (USDOC, NMFS, 

2014).

Table 4.9 2 shows commercial landings in thousands of pounds of key species or species 

groups within the GOM, including blue crab, groupers, menhaden, mullets, oysters, red snapper, 

shrimp, stone crab, and tunas (USDOC, NMFS, 2014). Fishers in the GOM region landed 

1.7 billion lb of finfish and shellfish in 2012 (USDOC, NMFS, 2014). The main commercial fishing 

gears used within the AOI and along the Gulf Coast are bottom trawls, purse seines, gill nets, 

pots/traps, and longlines (bottom and pelagic) (Table 4.9-3). Commercial landings can show 

seasonal patterns in fish abundance or the effects of legislative closures but do not provide actual 

locations of fishing activity. Such information must be inferred from species-specific habitat 

preferences and the particular gear used. For example, yellowfin tuna are caught with surface 

longlines fishing beyond the continental shelf, or red snapper are caught with hook-and-line near 

reefs or other structures in inner and middle shelf waters.

Two methods used to protect specific habitats and control commercial fishing effort are 

designating closed areas (space) or closing fisheries (by time: temporary, seasonal, or permanent). 

Permanent fishery or area closures are year-round, whereas seasonal and rolling closures are 

usually only at certain times of the year. Locations of selected seasonal and area closures to 

commercial fishing in Federal waters of the AOI are shown in Figure 4.9-1 and listed in Table 4.9-4. 

To notify the public of fishery or site closures, NMFS publishes the regulations, which are usually 

associated with an FMP amendment or management action, in the Federal Register. 

Deepwater Horizon Oil Spill

The Deepwater Horizon explosion, oil spill, and response had various impacts on the 

commercial fishing industry. The initial closure of 17,648 km2 (6,814 mi2

) occurred on May 2, 2010, 

12 days after the initial explosion. As the oil spill continued and spread due to currents and winds, 

the closure was expanded to include areas off Louisiana, Mississippi, Alabama, and Florida based 

on oil-slick modeling (USDOI, BOEM, 2012a). At its peak on June 2,2010, the fishery closure 

encompassed 229,271 km2 (88,522 mi2

), or approximately 37 percent of the Federal EEZ. The last 

of the closed areas was reopened on April 19, 2011 (USDOC, NOAA, 2011).

Carroll et al. (2016) describes the short-term impacts of the Deepwater Horizon oil spill on 

the GOM commercial fishing industry. From May through December 2010, there were reductions in 

landings for most species, including shrimp, oysters, menhaden, blue crab, and pelagic finfish. This 

impacted harvesters, dealers, processors, distributors, marketers, and restaurants in the GOM

seafood supply chain. Austin et al. (2014a,b) employed ethnographic methods and data analysis to 

analyze the impacts of the Deepwater Horizon oil spill on various industries, including the seafood 

industry. This study points out how the short-term impacts of the Deepwater Horizon on the seafood 

industry were exacerbated by existing trends (such as increasing import competition) and seafood 

safety concerns. The longer term impacts of the Deepwater Horizon will depend on the impacts to 
4-308 Description of the Affected Resources and Impact Analysis

fish populations (refer to Chapter 4.1). Fodrie and Heck (2011) concluded that there was no 

substantial shift in species composition for some nearshore fish species in the GOM after the spill. 

In addition, commercial landings for most species have not substantially changed during recent 

years (USDOC, NMFS, 2016c). Additional information pertaining to this resource and NMFS’ 

determination of the effects of the Deepwater Horizon explosion, oil spill, and response may be 

found in the Final PDARP/PEIS (Deepwater Horizon Natural Resource Damage Assessment 

Trustees, 2016). 

4.9.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, the IPFs that may impact commercial fisheries within the AOI 

include (1) active acoustic sound sources (e.g., airguns; non-airgun HRG sources such as highresolution boomers, sparkers, and CHIRP subbottom profilers; SBESs and MBESs; and side-scan 

sonars), (2) vessel traffic, (3) stand-off distance, (4) seafloor disturbance, (5) entanglement, and 

(6) accidental fuel spills.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact level categories. In contrast, the analysis 

of impacts associated with Alternatives B through G are organized by alternative-specific mitigation 

measures and how each these measures may reduce impact levels.

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For commercial 

fisheries, the below significance criteria have been used to evaluate the level of impact for each IPF.

Nominal impacts to commercial fisheries would include those where little to no measurable 

impacts are observed or expected. There would not be any interruption of commercial fishing 

activities, gear damage, or detectable impacts to commercial fish resources.

Minor impacts to commercial fisheries would include those that are detectable but not 

severe or extensive. Minor impacts to commercial fisheries would include localized, short-term 

interruption of commercial fishing activities or localized gear damage with no detectable effect on 

commercial fish landings. Minor impacts also would include localized, minor impacts on fish 

resources with no detectable effect on commercial fisheries landings.

Moderate impacts to commercial fisheries would be detectable, short term, and extensive 

but not severe; or severe but localized. Moderate impacts to commercial fisheries would include 

extensive but infrequent interruption of commercial fishing activities, damage to fishing gear 

sufficient to result in detectable decreases in commercial fisheries landings, and extensive but not 
Gulf of Mexico G&G Activities Programmatic EIS 4-309

severe impacts on fish resources (i.e., not sufficient to result in sizable decreases in commercial 

fisheries landings).

Major impacts to commercial fisheries would be detectable, extensive, and severe. Major 

impacts to commercial fisheries would include extensive, frequent interruption of commercial fishing 

activities; damage to fishing gear sufficient to result in sizable decreases in commercial fisheries 

landings; and extensive, severe impacts on fish resources (i.e., sufficient to result in sizable 

decreases in commercial fisheries landings).

4.9.2.1 Impacts of Routine Activities

Active Acoustic Sound Sources

The spatial and temporal characteristics of active acoustic sound source utilization vary 

depending on the type of activity. As discussed in Chapter 4.4.2.1, HRG surveys may take several 

days and cover smaller areas, whereas seismic surveys (i.e., 2D, 3D, 4D, WAZ, or VSP) may occur 

throughout significant portions of the AOI and continue for weeks, months, or even up to a year. 

Therefore, proposed G&G activities include various types of seismic and non-seismic surveys that 

could affect economically valuable commercial fisheries and fishing operations throughout the AOI, 

with appropriate caveats. The spatial and temporal (e.g., seasonal fishing activity) characteristics of 

individual commercial fishery are important to assess impact.

Physiological and behavioral impacts caused by active acoustic sound sources can occur in 

invertebrates; however, this depends on the species (Chapter 4.4.2.1). For some invertebrates, 

behavioral and physiologically impacts have the potential to indirectly influence catchability of some 

species. However, the available studies of the effects of sounds generated by G&G sound sources 

on economically important invertebrates suggest that behavioral responses are very limited 

(Chapter 4.4.2.1) (La Bella et al., 1996; Andriguetto-Filho et al., 2005; Parry and Gason, 2006). 

Given these results, it is unlikely that commercial fisheries that use pots/traps, dredges, and otter 

trawls to catch invertebrates would be significantly affected by exposure of these animals to seismic 

sound.

Sound is used by fishes in a variety of ways (Zelick et al., 1999; Fay and Popper, 2000), as 

summarized in Appendix J. A detailed discussion of direct and indirect effects of sound on fishes is 

presented in Chapter 4.4.2.1. Sound produced from anthropogenic sources (e.g., airguns, 

echosounders) can directly affect fishes in a variety of ways, ranging from changes in behavior to 

mortality. Direct effects such as auditory masking or TTS may impede a fish’s ability to detect 

biologically relevant sounds, thereby adversely impacting fitness. Thus, anthropogenic sound 

sources could interfere with normal behaviors or impact the survival of individuals or populations 

(e.g., feeding, predator detection, finding mates, and spawning). These direct effects could lead to 

indirect effects such as changes in the catchability of commercial fish stocks. In particular, 

anthropogenic sound has the potential to cause fishes to alter their movements, including avoidance 

of certain areas, affecting the ability of fishers to locate and capture them, which could increase the 

potential for changes to commercial fishery landings and revenue to fishers.
4-310 Description of the Affected Resources and Impact Analysis

Available studies indicate that fish catch can be impacted by seismic airgun sounds and may 

increase, decrease, or remain the same (Skalski et al., 1992; Løkkeborg and Soldal, 1993; Engås 

et al., 1996; Løkkeborg et al., 2012). When measured, the data indicated that catch rates return to 

normal within several days of sound cessation, suggesting that the effects are temporary. The 

change in fish catch depends on the species being fished, fishing gear used, and fishing location 

(Løkkeborg et al., 2012; Hawkins et al., 2014). Limited information is available about the response 

of commercially important fish to seismic survey sounds, in part because of the difficulty observing 

the behavior of fish populations at the temporal and spatial scales at which commercial fishing 

activities are conducted.

The impacts from active acoustic sound sources to fish behavior is discussed in 

Chapter 4.4.2.1. It is possible that sounds generated by some types of seismic survey equipment 

could affect the behavior and availability of the prey of commercially important fishes. The findings 

of several studies indicate that seismic surveying temporarily decreases local abundances of some 

fishes, while other fishes moved to deeper depths (Chapman and Hawkins, 1969; Dalen and 

Knutsen, 1987; Engås et al., 1996; Slotte et al., 2004). Conversely, sound might not elicit any 

behavioral responses unless they mimic biologically relevant characteristics of sounds similar to 

those produced by predators or prey (Plachta and Popper, 2003; Doksaeter et al., 2009; Jorgenson 

and Gyselman, 2009; Peña et al., 2013). Fishes exposed to seismic sound initially exhibit a startle 

response, then habituate to the sound, and after a period of time resume normal behavior 

(McCauley et al., 2000a; Fewtrell and McCauley, 2012). Thus, reaction to sound is species-specific 

and also dependent upon the level and type of sound being produced.

It appears that exposure to seismic sound can startle fish and, for some commercially 

important species, cause them to move to deeper depths or away from a seismic sound source. 

Additionally, exposure to seismic sound can cause behavior responses that change the availability of 

commercially important fish species to traditional fishing gear for a period of time. The spatial scale 

of behavior responses to seismic sound is not well understood, but it can extend up to 50 km (31 mi) 

from a seismic sound source (Slotte et al., 2004). Behavioral effects are variable and depend on the 

species, habitat, previous exposure, and current motivation (Chapter 4.4.2.1). Data indicate that 

behaviors (e.g., feeding, spawning, or migration) of commercially exploited pelagic and demersal fish 

stocks would be affected only temporarily. Given the limited spatial and temporal characteristics of 

seismic airguns used under the activity scenario, whether used in HRG or non-HRG surveys (refer to

Chapter 4.4.2.1), and the results of limited seismic sound exposure studies on fishes, it is likely that 

potential impacts to commercial fisheries resources would be minor, with no population-level effects, 

under Alternative A. Indirectly, catch rates could decline but would be expected to return to normal 

levels following the cessation of the seismic operation (Engås et al., 1996; Engås and Løkkeborg, 

2002). Therefore, there could be an increased potential for a localized and temporary decrease or 

increase, depending on the gear type, in catchability of one or more commercial fish species. Given 

the range of response of fish to gear (catch increases and decreases) and the temporary nature of 

the behavioral effects associated with seismic airguns, G&G activities are expected to result in 

minor impacts to commercial fisheries under Alternative A.
Gulf of Mexico G&G Activities Programmatic EIS 4-311

As discussed in Chapter 4.4.2.1, electromechanical sound sources such as echosounders, 

subbottom profilers, side-scan sonars, and MBESs used in non-airgun HRG surveys could affect the 

behavior of some fish species (Nestler et al., 1992; Mann et al., 1997; Popper et al., 2004) and not 

others (Doksaeter et al., 2009, 2012; Sivle et al., 2012). Sonar can cause TTS in fish, but studies 

have shown that the occurrence of TTS varies among species and that the severity of TTS can vary 

among individuals of the same species, depending on age and developmental stage (Popper et al., 

2007; Halvorsen et al., 2012, 2013). Sonar at intensities and durations considerably higher and 

longer than what is normally expected (193 and 195 dB re 1 μPa SPLrms) can cause TTS in some 

species (Popper et al., 2007; Halvorsen et al., 2013). Current research suggests that recovery from 

TTS occurs within 24 hours (Halvorsen et al., 2012, 2013). Therefore, impacts from 

electromechanical sources could influence the behavior and hearing abilities of some commercial 

fisheries resources. The effects are expected to be localized and temporary, with no populationlevel effects. Therefore, impacts associated with electromechanical sounds, such as acoustic sound 

sources used in non-seismic HRG surveys, are expected to result in nominal impacts to commercial 

fishery resources under Alternative A.

Vessel Traffic

Vessel traffic generated by each type of G&G survey proposed within the AOI is shown in 

Table 3.2 7, and the types of surveys and activity level scenarios are described in Chapter 3.3.1.3. 

Under Alternative A, vessel traffic could increase slightly in specific areas; however, this 

vessel traffic is not expected to cause any additional impact to commercial fishery resources, 

including commercial fisheries landings. Impacts are expected to be nominal because vessel traffic 

is relatively high in the AOI, and G&G activities have been ongoing in the area. Additionally, 

commercial fisheries and G&G operators are accustomed to cooperatively utilizing the same waters, 

and advance notice of seismic survey activity is provided to fishers by seismic survey operators. 

Resultant impacts from vessel traffic would be stand-off distances and entanglement as discussed 

below.

Stand-Off Distance

Due to the limited maneuverability of seismic survey vessels towing airgun streamers, standoff distances are implemented. For safety reasons, stand-off distances are meant to keep other 

vessel traffic at certain distances from the seismic surveys. Neither a seismic vessel towing an array 

nor a fishing vessel towing fishing gear are particularly maneuverable; therefore, communication 

between the industries is necessary to avoid accidents. Typical stand-off distance protocols are 

described in Chapter 3.3.1.5. 

The direct effects of a stand-off distance are the temporary loss of access to fishing grounds 

and loss of fishing time. Stand-off distances associated with G&G activities may require commercial 

fishers to retrieve nets or lines earlier than usual to avoid seismic survey vessels or cause them to 

stand off until the seismic vessels have moved past the fishing grounds. If commercial fishers 

temporarily lose access to fishing grounds or suspend fishing activity, they may experience 
4-312 Description of the Affected Resources and Impact Analysis

reductions in catch and quality of catch, which could ultimately affect their revenue. Interruption of 

fishing could be further exacerbated if numerous seismic vessels are conducting surveys through 

fishing grounds and on optimal fishing locations (e.g., fishing grounds or seasons), thus delaying the 

deployment of fishing gear in locations that maximize a fisher’s catch.

Vessel traffic associated with G&G activities would increase in specific areas, thereby 

increasing the potential for temporary interactions of seismic vessels and commercial fishing vessels 

through stand-off distances. Seismic survey operators typically advise fishers when they will be 

active in an area. Given the small area typically occupied by the stand-off distance for seismic 

vessels, the short duration of the impact at any given location, and the advance notice provided by 

seismic survey operators, the potential for space-use conflicts between G&G activities and 

commercial fishing operations within the AOI will be limited. Under Alternative A, G&G activities and 

associated stand-off distances are not expected to have any indirect effects on commercial fishery 

operations unless these activities cause commercial fishers to leave an impacted fishery to 

concentrate on alternative fishing activities. Commercial fisheries are continuing to evolve, so it is 

difficult to gauge whether conflicts in area use with seismic operations would cause some fishers to 

leave a fishery. Most commercial fishers already participate in various commercial fisheries, so it is 

unlikely that stand-off distances would cause any significant changes in fishing effort distribution.

Existing space-use conflicts (e.g., competing fisheries, and commercial fishing and OCS 

development) are an important consideration in marine spatial planning (Crowder and Norse, 2008; 

Douvere and Ehler, 2009). Seismic survey activity in a fishing area would preclude use of that area 

to fishers while the survey vessel is operating. When access to fishing grounds is not possible 

because of stand-off distance requirements, there would be a minor incremental increase in impacts 

to commercial fisheries. Although stand-off distances associated with the proposed G&G activities 

could affect a limited amount of commercial fishing within the AOI, impacts are expected to be 

intermittent, localized, and temporary. Impacts to commercial fisheries landings arising from standoff distances are expected to be minor under Alternative A.

Seafloor Disturbance

Bottom fisheries (i.e., dredges, otter trawls, and bottom longlines) in the AOI are among the 

most valuable commercial fisheries. The main effect associated with seafloor disturbance is longterm change in benthic community structure. The projected area of seafloor disturbance from G&G 

activities is an extremely small percentage of the planning areas (refer to Table 3.2-8). Depending 

on the amount and frequency of G&G survey effort that could disturb the seafloor in a specific area, 

G&G activities could change biodiversity, cause habitat fragmentation, and reshape benthic 

community structure (albeit on very small spatial scale), which could adversely and indirectly affect 

commercial bottom fisheries. Such effects have been documented in trawling and dredging 

operations (Barnette, 2001). Benthic communities have been significantly affected by commercial 

and recreational fishing activities, which are estimated by Watling and Norse (1998) to trawl 

approximately 53 percent (14.8 million km2 [5.7 million mi2

]) of the world’s continental shelf annually.
Gulf of Mexico G&G Activities Programmatic EIS 4-313

Seafloor disturbance related to G&G activities under Alternative A could indirectly affect 

some commercial fishing activities within the AOI. Although it is difficult to estimate the economic 

impacts at the regional level (if any), it is still possible these activities would impact some specific 

commercial fisheries in the AOI. It is likely that intermittent, temporary, and short-term changes in 

benthic communities would occur as a result of G&G benthic sampling and coring activity 

(Chapter 4.5.2.1). However, these types of G&G activities would be conducted on a very limited 

basis and the total area affected represents a small fraction of the AOI (Table 3.2-8). In addition, 

BOEM would require site-specific information concerning potential sensitive benthic communities 

(including hard/live bottom areas, deepwater coral communities, and chemosynthetic communities) 

prior to approving any G&G activities involving seafloor-disturbing activities or placement of bottomfounded equipment or structures in the AOI.

The total areal extent of seafloor disturbance expected under the proposed action scenario is 

a very small fraction of the seafloor in the AOI (Table 3.2-8). However, there is a chance that a 

particular seafloor disturbance, no matter how small, may occur within a productive fishing area. 

Seafloor disturbance and its impact to commercial fishing operations and commercial fishery 

landings under Alternative A are expected to be limited and localized, but potentially overlapping 

with productive fishing grounds and/or shipwrecks that function as artificial reefs and coral habitat; 

therefore, impacts are expected to be minor under Alternative A.

Entanglement

Vessel traffic associated with G&G activities would increase in specific areas, thereby 

increasing the potential for direct interference with commercial fishing operations. Direct impacts to 

commercial fisheries associated with G&G activities would include entanglement or damage to 

fishing gear. Benthic and pelagic fishing gear have the potential to be impacted by G&G activities.

Several commercial fishery gears, such as pots/traps, gillnets, and longlines (pelagic and 

bottom), are classified as passive gear. These gear types usually are set and left unattended for 

hours or days. Therefore, an increase in vessel traffic and towed survey gear (e.g., streamers) could 

increase the chances that fishing gear would be disturbed or damaged (buoys and lines cut) by 

seismic vessels, especially during the night. The G&G survey activities would be expected to result 

in a minor increased risk for entanglement of fishing gear with seismic gear, particularly in 

nearshore waters (<4.8 km [3 mi] from shore) where benthic and demersal inshore fisheries are 

operating.

Commercial fisheries operations that use fishing gear placed on the seafloor have the 

potential for entanglement or damage within the AOI. Most passive gears, such as traps, pots, and 

bottom longlines, are marked by surface buoys. The buoys of longlines and groups of traps may 

mark only the terminal ends of runs of gear. These types of gear would be susceptible to damage or 

entanglement from G&G bottom-founded equipment (e.g., OBCs, anchors, receivers, and certain 

geotechnical surveys [Appendix F, Section 1.1.3]). Under Alternative A, seafloor disturbance 
4-314 Description of the Affected Resources and Impact Analysis

caused by bottom-sampling activities has the potential to affect unmarked fishing gear or segments 

of gear deployments used by bottom-associated commercial fishing operations.

Entanglement and its impact to commercial fishing operations and commercial fishery 

landings under Alternative A have the potential to overlap with fishing grounds. Stand-off distances 

and advanced notification from seismic survey operations will reduce the direct interactions between 

fishing gear and seismic survey equipment (refer to the “Stand-off Distance” IPF discussion

[Chapter 4.9.2.3.3]). Additionally, fishing gear will have surface markers. Commercial fisheries and 

G&G operators are accustomed to cooperatively utilizing the same waters and are familiar with the 

operations and equipment of each other’s industries. Thus, fishing equipment could be damaged, 

but the potential for impacts are reduced by several measures, and any impacts would be spatially 

localized and temporary. For example, one of these measures is the Fishermen’s Contingency Fund 

Program, which was created to compensate fishermen for economic and property losses as a result 

of oil and gas industry activities on the OCS (Sharp and Sumaila, 2009; USDOC, NMFS, 2013a). 

According to NMFS, claims were approved for $188,168 in FY 2010, $126,608 in FY 2011, and 

$63,588 in 2012. Therefore, impacts to commercial fisheries landings arising from entanglement are 

expected to range from nominal to minor under Alternative A.

4.9.2.1.1 Routine Activities Impact Conclusions

Overall, impacts from proposed activities to commercial fisheries are expected to range from 

nominal to minor. Airgun sound sources, seafloor disturbance, and stand-off distances may result 

in minor impacts; entanglement risks may result in nominal to minor impacts; and HRG sound 

sources and vessel traffic impacts would be nominal. 

4.9.2.2 Impacts of an Accidental Fuel Spill

An accidental event could result in the release of diesel or other fuel by a survey vessel, but 

such an event has a remote probability of occurring. For the purposes of this analysis, it is assumed 

that a vessel collision may release 1.2 to 7.1 bbl of diesel fuel.

In the event of a fuel spill from a seismic vessel, it may be possible that commercially 

important fishes could be exposed to water soluble fractions of spilled diesel. Surface-feeding fishes 

are most likely to be exposed. For example, dolphinfish often consume small fishes associated with 

floating Sargassum habitat. Tuna and swordfish, species important to commercial fisheries, 

sometimes associate with Sargassum habitat or surface waters. Given the size of the diesel spill, 

the extent of surface fouling would be limited. Under the expected spill scenario developed in 

Chapter 3.3.2.1, a diesel fuel spill would be expected to remain in surface waters, subjected to 

evaporation and dispersion; a portion of the spill may sink. It is unlikely that a small release of diesel 

fuel would have any direct impact to commercial fishery landings in the AOI. Although a small fuel 

spill is not likely to pose a serious threat to fishery landings, there is the possibility that consumers 

would not buy fish or shellfish from the affected locality. Misperceptions like this could result in a 

temporary drop in revenue to local commercial fishers. However, potential for impacts are reduced 

by several measures, including the Fisherman’s Contingency Fund Program, as discussed above. 
Gulf of Mexico G&G Activities Programmatic EIS 4-315

Therefore, impacts to commercial fisheries resources from an accidental fuel spill would be nominal

under Alternative A.

4.9.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for commercial fisheries are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI.

4.9.2.3.1 Active Acoustic Sound Sources

The impacts from active acoustic sound sources from the proposed action are discussed in 

Chapter 4.9.2.1. Overall, Chapter 4.9.2.1 determined there would be increases in ambient noise 

levels within specific portions of the AOI during G&G operations, but nominal to minor impacts to 

commercial fisheries.

All G&G survey activities associated with the OCS Program are included in the proposed 

action; therefore, G&G activities are not included in the cumulative analysis but instead are 

addressed in the proposed action impact analysis. Active acoustic sound sources related to oil and 

gas development have been ongoing in the GOM for decades and are likely to be used in the future. 

As described in Chapter 4.9.2.1, active acoustic sound produced by seismic surveys conducted 

under the proposed action can influence fish behavior in ways that may impact commercial fishing 

catch or effort, but data suggest their effects are temporary.

The G&G activities associated with the proposed action will not be conducted within State 

waters. However, other agencies can permit G&G activities that can include active sound sources 

(e.g., seismic airguns and side-scan sonars for oil and gas activities in State waters). Sound 

produced by these surveys may propagate into coastal waters but will be significantly reduced in 

intensity proportional to the distance of seismic survey vessels from State waters boundaries and 

will, in most cases, add an insignificant amount to sound generated by similar sound sources 

operating in State waters. Effects of seismic sound propagating into State waters from G&G 

activities is likely to have an insignificant effect on commercial fishing when compared with sound 

caused by seismic vessels operating in State waters.

Other major factors that contribute active acoustic sound sources are shown in Table 3.4-1. 

Impacts to commercial fisheries from similar sound sources under the G&G proposed action are 

discussed in Chapter 4.9.2.1. Active acoustic sound sources from G&G activities considered in

cumulative impacts assessment have been ongoing in the AOI for multiple decades and are likely to 
4-316 Description of the Affected Resources and Impact Analysis

continue in the future. Anthropogenic sounds levels in the marine environment are increasing, and 

impacts fish behavior and hearing capabilities may impact commercial fishing (Slabbekoorn et al., 

2010; Radford et al., 2014). Yet, it is difficult to assess overall increases in sound because of the 

lack of baseline data from individual sound sources and the ambient sound conditions (Hawkins 

et al., 2014).

Activities associated with the proposed action would increase levels of active acoustic sound 

sources within the AOI, resulting in increases in ambient noise levels during G&G operations 

(primarily the WPA and CPA). Impacts to fisheries catch have been noted in several instances, 

although those impacts are shown to be temporary. Seismic surveys are not conducted 

homogenously over the entire AOI nor homogenously over the 10-year period, thus they are spatially 

and temporally limited and their impacts are not likely to increase over time. Therefore, the 

cumulative effects of added project-related active acoustic sound sources would result in minor

incremental increases in impacts under Alternative A.

4.9.2.3.2 Vessel Traffic

Impacts from vessel traffic from the proposed action are discussed in Chapter 4.9.2.1 and 

would be nominal. Support vessel traffic is a key part of most OCS Program activities 

(Chapter 3.4). Increased vessel traffic in particular areas could negatively affect commercial fishing 

effort or gear deployment/retrieval. Commercial fisheries and G&G operators are accustomed to 

cooperatively utilizing the same waters, and advanced notice of seismic survey activity is provided to 

fishers by seismic survey operators.

Under the proposed action for activities within BOEM’s jurisdiction, seismic vessels and other 

support vessel traffic will operate primarily in Federal waters but will cross State waters when 

transiting to and from shore. Oil and gas vessels transiting State waters while departing from and 

returning to port will not be engaged in BOEM-managed G&G activities. Thus, such seismic and 

support vessels can navigate to avoid active fishing vessels and deployed fishing gear.

Vessel traffic that may result from oil and gas activities is shown in Table 3.4-2. Vessel 

traffic from the proposed action is discussed in Chapter 3.3.1.3 and provided in Table 3.2-7. Vessel 

traffic from G&G operations under the proposed action would not represent a significant increase to 

existing vessel traffic from cumulative operations in coastal areas because the vessel traffic from the 

proposed action in the coastal environment will only involve support vessels transiting in and out of 

various ports along the Gulf Coast. Vessel traffic from G&G operations could increase to existing 

vessel traffic in offshore areas; however, commercial fisheries and G&G operators are accustomed 

to cooperatively utilizing the same waters, and advance notice of seismic survey activity is provided 

to fishers by seismic survey operators.

Considering the long-standing cooperative use of waters between commercial fishers and 

G&G-associated activities, and advance notice of seismic survey activity, effects from vessel traffic 

are not likely to significantly increase impacts from the cumulative scenario. Additionally, impacts 
Gulf of Mexico G&G Activities Programmatic EIS 4-317

would be temporary and localized to areas of vessel traffic and are not expected to increase over 

time. Therefore, when vessel traffic associated with the proposed action is added to existing traffic 

associated with the activities under the cumulative scenario component, there would be a nominal

incremental increase in impacts to commercial fisheries.

4.9.2.3.3 Stand-Off Distance

Impacts from stand-off distances to commercial fisheries from the proposed action are 

discussed in Chapter 4.9.2.1 and are expected to be minor. Certain activities under the OCS 

Program are managed to provide an area, called the stand-off distance, around the activity to help 

avoid interactions between fishing vessels and oil and gas vessels that would be hazardous to 

vessels, crews, and gear. Stand-off distances under the G&G proposed action that are similar to 

those in OCS Program could cause temporary loss of access to fishing grounds and loss of fishing 

time.

Under the proposed action, seismic survey vessels with large stand-off distances will operate 

only in Federal waters; however, non-surveying seismic vessels and other support vessel traffic will 

traverse State waters when departing from and returning to port. Non-surveying seismic vessels 

operating in State waters would not remain stationary, and impacts from stand-off distances would 

be short term and localized.

Stand-off distance may result from other major factors shown in Table 3.4-1. Stand-off 

distances resulting from these activities would cause similar impacts to those from seismic surveys 

from G&G activities. Stand-off distances from G&G activities are expected to cause temporary loss 

of access to fishing grounds and loss of fishing time. Stand-off distances from G&G activities will 

have less of an impact when seismic survey vessels are not operating, for example, in coastal or 

State waters.

Loss of access to fishing grounds or delays in setting fishing gear in optimal locations may 

result in reductions in catch and quality of catch. This could ultimately affect commercial fishing 

revenue. Access to fishing grounds may occasionally be limited due to stand-off distances from 

seismic activity. This is discussed in the cumulative impact section. There would be a minor

incremental increase overall in impacts to commercial fisheries.

4.9.2.3.4 Seafloor Disturbance

As discussed in Chapter 4.9.2.1, impacts to commercial fisheries landings arising from 

seafloor disturbance are expected to be minor. Seafloor-disturbing activities associated with the 

proposed action over the next 10 years are included in Table 3.4-2. The cumulative scenario 

includes activities that disturb the seafloor by anchoring, trenching, coring, and bottom sampling. 

Seafloor disturbance from these activities may cause long-term change in benthic community 

structure. Seafloor-disturbing activities and the projected area of seafloor disturbance associated 

with G&G activities under the proposed action can be found in Table 3.2-8. The projected area of 

seafloor disturbance is a very small fraction of the planning areas.
4-318 Description of the Affected Resources and Impact Analysis

State waters oil and gas activities disturb the seafloor by anchoring, trenching, coring, and 

bottom sampling. The G&G activities under the proposed action will not occur within State waters, 

which are outside of BOEM’s jurisdiction; therefore, the proposed action will not contribute to 

cumulative seafloor disturbance impacts in State waters. In addition, it is extremely unlikely that 

effects such as increased turbidity resulting from activities that disturb the seafloor conducted 

external to State waters would have enough persistence to be transported into State waters by 

ocean physical processes.

Seafloor disturbances contributed by other major factors are shown in Table 3.4-1. The 

areas likely to be impacted under the coastal component of the cumulative scenario and those 

conducted under the proposed action will not likely overlap because the proposed action activities 

generally will be restricted to Federal waters and distant from coastal waters. The areal extent of 

seafloor disturbance from G&G activities in the proposed action is small and, thus, impacts will be 

localized and temporary.

The number of seafloor disturbances expected under the proposed action do not occur 

homogenously over the entire AOI nor homogenously over the 10-year period; thus, they are 

spatially and temporally limited and their impacts are not likely to increase over time. Therefore, the 

cumulative effects of added project-related seafloor disturbance would result in nominal incremental 

increases under Alternative A.

4.9.2.3.5 Entanglement

As discussed in Chapter 4.9.2.1, Impacts to commercial fisheries landings arising from 

entanglement are expected to range from nominal to minor. Impacts to commercial fisheries 

associated with G&G activities would include entanglement or damage to fishing gear.

Support vessel traffic or other OCS Program activities could result in entanglement of fishing 

gear (Chapter 3.4.1). Similar activities from G&G seismic surveys can also increase the risk of 

entanglement of fishing gear from towed airgun arrays or bottom-laying seismic operations 

(Appendix F, Section 1.1.3). Increased G&G activity could negatively affect commercial fishing if 

fishing gear were to be entangled. Commercial fisheries and G&G operators are accustomed to 

cooperatively utilizing the same waters, and advanced notice of seismic survey activity is provided to 

fishers by seismic survey operators.

The G&G activities associated with the proposed action will not be conducted within State 

waters. However, other agencies can permit G&G activities that can include towed airgun arrays or 

bottom-laying seismic equipment, which could cause entanglement of fishing gear. Under the 

proposed action, seismic survey vessels will operate only in Federal waters. Non-surveying seismic 

vessels and other support vessel traffic will traverse State waters when departing from and returning 

to port and could increase the risk of entanglement in these areas, but these impacts would be shortterm and localized.
Gulf of Mexico G&G Activities Programmatic EIS 4-319

Entanglement may result from other major factors shown in Table 3.4-1. Entanglement 

resulting from these activities would cause similar impacts to those from towed airgun arrays or 

bottom-laying seismic operations from G&G activities. Entanglement from G&G activities are 

expected to cause damage to fishing gear and loss of fishing time.

Factors such as stand-off distances and marker buoys for fishing gear will reduce the risk of 

entanglement of fishing gear from G&G activities. Commercial fisheries and G&G operators are 

accustomed to cooperatively utilizing the same waters and are familiar with the operations and 

equipment of each other’s industries. When entanglement of fishing gear associated with the 

proposed action are added to activities in the cumulative scenario, there would be a nominal

incremental increase in impacts to commercial fisheries.

4.9.2.3.6 Cumulative Impact Conclusions

Overall, proposed activities associated with the proposed action would increase the levels of 

noise and vessel and aircraft traffic within the AOI, resulting in sporadic increases in ambient noise 

levels during proposed G&G operations. Sources of noise associated with the cumulative scenario 

that may affect commercial fisheries in the AOI include active acoustic sound, vessel traffic, stand-off 

distance, seafloor disturbance, entanglement, and accidental fuel spills. Many of these IPFs may 

occur simultaneously during some projected operations under the OCS Program.

The spatial distribution of activities projected under the proposed action during the project 

period are most concentrated within deepwater regions of the CPA and WPA, and less concentrated 

within continental shelf waters (Table 3.2-1). Very little activity is projected to occur within the EPA. 

Temporally, activity levels associated with the proposed action vary by activity type and year (Tables

3.2-1 through 3.2-5). Overall, proposed activities are expected to result in nominal to minor

incremental increases in impacts to commercial fisheries.

4.9.2.4 Accidental Fuel Spills

As discussed in Chapter 3.4, the AOI includes an extensive system of offshore oil and gas 

production facilities. The potential for fuel spills from vessels involved in the cumulative scenario 

would be higher than that expected under the proposed action because of the magnitude of vessel 

activity in the AOI and the high number of vessel transits. However, the potential for collision and 

product transfer fuel spills from vessels involved in the cumulative activities scenario is considered 

remote because of the small number of vessels, the type of vessels and required fuels, the 

standards and protocols for management of vessel fuels, and the aids to navigation and crew 

training for vessels likely to be used under the proposed alternative. With the use of AIS on large 

sea-going vessels, radar, and licensing of vessel captains, the potential of a vessel collision 

occurring is low, and the potential for a resultant spill is even lower. Fuel and diesel used for 

operation of support vessels is light and would float on the sea surface where is it subjected to 

weathering, dispersion, and dissolution. Heavier fuels may be used in larger commercial vessels 

involved in marine transportation. Thus, the increase in potential for accidental fuel spills arising 

from vessel collision during G&G activities would be considered extremely small.
4-320 Description of the Affected Resources and Impact Analysis

The G&G activities associated with the proposed action will not be conducted within State 

waters. However, vessels involved with G&G activities may transit through State waters. Because 

the majority of the activities associated with proposed action will not occur in State waters, there is a 

low probability of a G&G activity-related fuel spill or that fuel spilled in Federal waters would be 

transported into State waters. Thus, the potential for spills from vessels involved in the cumulative 

activities scenario is remote and it is anticipated that, if a spill occurred, the spill size would be 

relatively small, the type of fuel that would likely be spilled would rapidly dissipate, and the area 

impacted would be a small.

Accidental fuel spills are probable from support vessels associated with other major factors 

(Table 3.4-1). As discussed earlier, the potential for collision and product transfer fuel spills from 

vessels involved in the cumulative activities scenario is considered remote. Fuel and diesel used for 

operation of support vessels is light and would float on the sea surface where is it subjected to 

weathering, dispersion, and dissolution. Heavier fuels may be used in larger commercial vessels 

involved in marine transportation. The potential for fuel spills from vessels involved in the offshore 

development component of the cumulative scenario would be higher than that expected under the 

proposed action because of the magnitude of vessel activity in the AOI and the high number of 

vessel transits. Thus, the increase in potential for accidental fuel spills arising from vessel collision 

during G&G activities would be considered extremely small.

Activities associated with all cumulative scenario components have the potential to cause an 

accidental fuel spill (Table 3.4-1). If accidental fuel spills from the cumulative scenario activities 

coincided spatially and temporally with an accidental fuel spill from G&G vessels, then cumulative 

impacts to commercial fishing could be exacerbated. Impacts from G&G vessels are most likely to 

be cumulative with OCS Program activities because of the higher number of vessels and greater 

spatial overlap between activities. Fuel and diesel used for operation of support vessels is light and 

would float on the sea surface where is it subjected to weathering, dispersion, and dissolution. 

There are also several mitigation measures in place to avoid vessel collisions. Therefore, impacts 

from accidental fuel spills from G&G activities will be spatially and temporally limited and would 

result in a nominal incremental increase in impacts to commercial fishing under the cumulative 

scenario.

4.9.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.9.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative B on commercial fisheries.

4.9.3.1 Impacts of Routine Activities

Additional mitigation measures under Alternative B that would not change the extent, 

severity, or timing of G&G activities include the expansion of NTL 2012-JOINT-G02 (inclusion of 

manatees and application to all deep-penetration seismic airgun surveys in all water depths) and the 
Gulf of Mexico G&G Activities Programmatic EIS 4-321

expanded use of PAM. Since these mitigation measures will not impact commercial fisheries, they 

will not be addressed in the following discussion.

4.9.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to April 30)

Alternative B would require seasonal restrictions for seismic airgun survey operations in 

coastal waters of the GOM shoreward of the 20-m (66-ft) isobath between January 1 and April 30 

(Figure 2.2-1). The impacts of active acoustic sound sources, vessel traffic, and exclusions zones 

would be reduced, but only within coastal waters between January 1 and April 30. The closure area 

would be 9,032,418 ha (22,319,105 ac), 13.1 percent of the area of the AOI (68,916,602 ha 

[170,292,924 ac]). The purpose of this mitigation measure is to provide protection to marine 

mammals within the closure areas from the IPFs associated with deep-penetration seismic airgun 

surveys. This mitigation measure would provide an ancillary benefit to some coastal fish species 

(Tables 4.4-1, 4.4-2, and 4.4-4) as the effects on fish hearing and behavior (discussed in detail in 

Chapter 4.4.2.1) will be reduced in the coastal seasonal restriction area. Furthermore, this may 

indirectly benefit commercial fisheries because a reduction in the impact to fish hearing and behavior 

could result in a reduction in the indirect impacts to commercial catch rates (discussed in detail in 

Chapter 4.9.2.1). Another benefit would be a reduction in vessel traffic and exclusion zones from 

seismic surveys during the closure period, which will subsequently reduce the potential for damage 

to fishing gears or loss of access of fishing grounds. However, seismic surveys will still occur 

outside the area, the closure timeframe is temporary, and the closure area is small compared with

the size of the AOI. Thus, while a change in survey timing in the coastal seasonal restriction area 

would slightly reduce the impacts of active acoustic sound sources, vessel traffic, stand-off 

distances, and entanglement from seismic airguns surveys on commercial fisheries, it would not 

change the overall impact level. Therefore, impacts of active acoustic sound sources from airguns, 

stand-off distance, and entanglement are expected to range from nominal to minor for commercial 

fisheries under Alternative B. The mitigation measure does not apply to sound sources from nonairgun HRG surveys or vessel traffic; therefore, the impacts will remain nominal for commercial 

fisheries under Alternative B. Impacts from seafloor disturbance activities would remain minor. 

4.9.3.1.2 Minimum Separation Distances

Alternative B would establish a 40-km (25-mi) separation distance between simultaneously 

operating deep-penetration seismic airgun surveys within the Areas of Concern (Chapter 2.2.2) to 

limit ensonification of specific areas of the AOI at the same time. When outside the Areas of 

Concern, the separation distance will be 30 km (19 mi). However, the separation distance 

requirement does not apply to multiple ships operating in a coordinated survey such as a WAZ 

survey, and it need not be maintained if unsafe or due to weather conditions.

Applicable routine IPFs for commercial fisheries are active acoustic sound sources, vessel 

traffic, stand-off distance, and entanglement. Limits on concurrent seismic airgun surveys under 

Alternative B could change the timing of seismic surveys in certain areas. The locations cannot be 

predicted in advance, but this would depend on the schedule, planned coverage of individual 

surveys, and ports to be used for support activities. Seismic surveys will still be conducted; 
4-322 Description of the Affected Resources and Impact Analysis

therefore, a change in the survey timing because of limits on concurrent seismic airgun surveys 

would not alter the impacts from active acoustic sound sources (including seismic airguns and 

electromechanical sounds), vessel traffic, stand-off distance, and entanglement. Therefore, impacts 

of active acoustic sound sources, stand-off distance, and entanglement are expected to range from 

nominal to minor for commercial fisheries under Alternative B. The mitigation measure does not 

apply to sound sources from non-airgun HRG surveys or vessel traffic; therefore, the impacts will 

remain nominal for commercial fisheries under Alternative B. Impacts from seafloor disturbance 

activities would remain minor. 

4.9.3.1.3 Seismic Restrictions in the Areas of Concern within the EPA

Additional restrictions under Alternative B include the prohibiting of deep-penetration seismic 

airgun surveys within the portion of the Areas of Concern (Chapter 2.2.2) falling within the EPA. 

This restriction does not apply to surveys related to currently leased blocks, any portion of the area 

encompassed by EPA Lease Sale 226, or neighboring OCS lease blocks adjacent to permitted 

survey areas but within an otherwise off limit area.

A restriction on seismic surveys within a portion of the AOI could result in reduced impacts 

from active acoustic sound sources, vessel traffic, stand-off distance, and entanglement due to the 

reduced area of activity. The purpose of this mitigation measure is to provide protection to marine 

mammals within these closure areas from the IPFs associated with deep-penetration seismic airgun 

surveys. This mitigation measure would provide an ancillary benefit to some oceanic fish species 

(refer to Appendix E) in the closure area, as the effects on fish hearing and behavior (discussed in 

detail in Chapter 4.4.2.1) will be reduced in the region. Furthermore, this may indirectly benefit 

commercial fisheries because a reduction in the impact to fish hearing and behavior could result in a 

reduction of the impacts to commercial fisheries catch rates (discussed in detail in Chapter 4.9.2.1). 

Another benefit would be a reduction in vessel traffic, stand-off distances, and entanglement from 

seismic surveys in the restricted areas that would subsequently reduce the potential for damage to 

fishing gear or loss of access of fishing grounds. The impacts of active acoustic sound sources, 

vessel traffic, stand-off distance, and entanglement from seismic airgun surveys would be reduced, 

but only within the portion of the Areas of Concern falling within the EPA. The size of the closure 

area is small compared with the AOI, and the majority of deep-penetration seismic airgun surveys 

will occur in the WPA and CPA where seismic surveys will not be restricted. Thus, there will not be 

a substantial reduction in seismic survey activity in the AOI, and the overall impacts on commercial 

fisheries would not change under Alternative B.

4.9.3.1.4 Routine Activities Impact Conclusions

Impacts to commercial fisheries landings arising from active acoustic sound sources, standoff distance, and entanglement from seismic airguns surveys are expected to range from nominal to 

minor under Alternative B. The mitigation measures do not apply to sound sources from non-airgun 

HRG surveys or vessel traffic; therefore, the impacts will remain nominal for commercial fisheries 

under Alternative B. Impacts from seafloor disturbance activities would remain minor. 
Gulf of Mexico G&G Activities Programmatic EIS 4-323

4.9.3.2 Impacts of an Accidental Fuel Spill

Under Alternative B, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. Alternative B would change the timing of certain surveys because of additional coastal 

seasonal restrictions; however, spills from seismic survey vessels could occur in the closure areas 

during times outside the closure period and spills from other survey vessels could occur during the 

closure period. A change in survey timing would not substantially change the risk of a small fuel 

spill. Therefore, the impacts of the IPFs would be very similar to those analyzed for Alternative A in 

Chapter 4.9.2.2. Impacts to commercial fisheries resources from an accidental fuel spill or small 

diesel fuel spill would be nominal under Alternative B.

4.9.3.3 Cumulative Impacts

Impact analyses presented in Chapters 4.9.3.1 and 4.9.3.2 determined that activities 

projected to occur under Alternative B would result in nominal to minor impacts to commercial 

fisheries, depending on the IPF. Mitigation measures for the proposed action under Alternative B 

are described in Chapter 2.2 and summarized in Chapter 4.9.3.1. A detailed impacts assessment 

under the cumulative scenario is provided in Alternative A (Chapter 4.9.2.3). Most mitigation 

measures under Alternative B would not change the extent, severity, or timing of activities in the 

proposed action, and therefore would not change the resultant impacts to commercial fisheries. 

Mitigation measures under Alternative B that would change the timing and extent of activities in the 

proposed action include a seasonal restriction for operation of airguns in Federal coastal waters, a 

minimum separation distance requirement for simultaneous seismic operations, and the prohibiting 

of deep-penetration seismic airgun surveys within portions of the EPA (Chapter 2.2.2).

Therefore, the mitigation measures under Alternative B do not change the cumulative 

outcomes described in Alternative A (Chapter 4.9.2.3); there would be a minor incremental increase 

in impacts to commercial fisheries from active acoustic sound sources and stand-off distances as 

well as a nominal incremental increase in impacts to commercial fisheries from vessel traffic, 

seafloor disturbance, entanglement, and accidental fuel spills.

4.9.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.9.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative C on commercial fisheries.

4.9.4.1 Impacts of Routine Activities

Additional mitigation measures under Alternative C that would not change the extent, 

severity, or timing of G&G activities, and therefore related impacts to commercial fisheries, include 

the expanded use of PAM for seismic airgun surveys, the expanded use of PSOs for seismic airgun 

surveys and HRG surveys, expansion of NTL 2012-JOINT-G02 (inclusion of manatees) for seismic 

airgun surveys, expansion of NTL 2012-JOINT-G02 to include HRG surveys using airguns, and a 
4-324 Description of the Affected Resources and Impact Analysis

pre-survey clearance period for HRG surveys. As such, those mitigation measures will not be 

addressed in the following discussion.

4.9.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to May 31)

Alternative C would require seasonal restrictions for seismic airgun survey operations in 

Federal coastal waters of the GOM shoreward of the 20-m (66-ft) isobath between February 1 and 

May 31 (Figure 2.3 1). The impacts of active acoustic sound sources, vessel traffic, and stand-off 

distance would be reduced, but only within coastal waters between February 1 and May 31. The 

closure area is 9,032,418 ha (22,319,105 ac) and represents 13.1 percent of the area of the AOI 

(68,916,602 ha [170,292,924 ac]). The purpose of this mitigation measure is to provide protection to 

marine mammals within the closure area from the IPFs associated with deep-penetration seismic 

airgun surveys. This mitigation measure would provide an ancillary benefit to some coastal fish 

species (Tables 4.4-1, 4.4-2, and 4.4-4), as the effects on fish hearing and behavior (discussed in 

detail in Chapter 4.4.2.1) will be reduced in the coastal seasonal restriction area. Furthermore, this 

may indirectly benefit commercial fisheries because a reduction in the impact to fish hearing and 

behavior could result in a reduction of the indirect impacts to commercial fisheries catch rates 

(discussed in detail in Chapter 4.9.2.1). Another benefit would be a reduction in vessel traffic and 

stand-off distance from seismic surveys during the closure period that will subsequently reduce the 

potential for damage to fishing gears or loss of access of fishing grounds. However, seismic surveys 

will still occur outside this area, the closure timeframe is temporary, and the closure area is small 

compared with the size of the AOI as a whole. Thus, while a change in survey timing in the coastal 

seasonal restriction area would slightly reduce the impacts of active acoustic sound sources, vessel 

traffic, stand-off distance, and entanglement from seismic airgun surveys on commercial fisheries, it 

would not change the overall impact levels.

4.9.4.1.2 Routine Activities Impact Conclusions

Impacts of active acoustic sound sources, stand-off distance, and entanglement from seismic 

airgun surveys are expected to range from nominal to minor for commercial fisheries under 

Alternative C. The mitigation measure does not apply to sound sources from non-airgun HRG

surveys or vessel traffic; therefore, the impacts will be nominal for commercial fisheries under 

Alternative C. Impacts from seafloor disturbance activities would remain minor. 

4.9.4.2 Impacts of an Accidental Fuel Spill

Under Alternative C, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. Alternative C would change the timing of certain surveys because of additional coastal 

seasonal restrictions. However, spills from seismic survey vessels could occur in the closure areas 

during times outside the closure period and spills from other survey vessels could occur during the 

closure period. A change in survey timing would not substantially change the risk of a small fuel 

spill. Therefore, the impacts of the IPFs would be very similar to those analyzed for Alternative A in 

Chapter 4.9.2.2. Impacts to commercial fisheries resources from an accidental fuel spill or small 

diesel fuel spill would be nominal under Alternative C.
Gulf of Mexico G&G Activities Programmatic EIS 4-325

4.9.4.3 Cumulative Impacts

Impact analyses presented in Chapters 4.9.4.1 and 4.9.4.2 determined that activities 

projected to occur under Alternative C would result in nominal to minor impacts to commercial 

fisheries, depending on the IPF.

Mitigation measures for the proposed action under Alternative C are described in 

Chapter 2.3 and summarized in Chapter 4.9.4.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.9.2.3). Most mitigation measures under 

Alternative C would not change the extent, severity, or timing of activities in the proposed action, and 

therefore would not change the resultant impacts to commercial fishing. Under Alternative C, the 

mitigation measure that would change the timing and extent of activities in the proposed action is a 

seasonal restriction from February 1 to May 31 for operation of airguns in Federal and State coastal 

waters shoreward of the 20-m (66-ft) isobath within the AOI. Therefore, the mitigations under 

Alternative C do not change the cumulative outcomes described in Alternative A (Chapter 4.9.2.3); 

there would be a minor incremental increase in impacts to commercial fisheries from active acoustic 

sound sources and stand-off distances, and a nominal incremental increase in impacts to 

commercial fisheries from vessel traffic, seafloor disturbance, entanglement, and accidental fuel 

spills.

4.9.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative D are the same as for 

Alternative A (Chapter 4.9.2). The additional mitigation measure under Alternative D would not 

reduce potential active acoustic impacts discussed in Alternatives A and C (Chapters 4.9.2.1 and 

4.9.4.1) and would remain nominal to minor. The mitigation would not alter the impact levels to 

commercial fisheries from vessel traffic, stand-off distances, seafloor disturbance, or entanglement 

and would remain nominal to minor. Under Alternative D, impacts of an accidental fuel spill on 

commercial fisheries would be as described for Alternatives A and C (Chapters 4.9.2.2 and 4.9.4.2) 

and would remain nominal. 

4.9.5.1 Impacts of Routine Activities

The additional mitigation measure under Alternative D, exclusion of bow-riding dolphins from 

shutdown protocols, would not change the extent, severity, or timing of IPFs outlined in 

Alternatives A and C. The mitigation measure does not apply to commercial fisheries or the 

associated IPFs; therefore, impacts of active acoustic sound sources, stand-off distance, and 

entanglement from seismic airgun surveys are expected to range from nominal to minor under 

Alternative D. Impacts from non-airgun HRG surveys and vessel traffic will be nominal under 

Alternative C, while impacts from seafloor-disturbing activities will be minor. 

4.9.5.2 Impacts of an Accidental Fuel Spill

Alternative D would not add additional mitigation measures that would reduce the risk of an 

accidental fuel spill. Therefore, the impacts of the IPFs would be very similar to those analyzed for 
4-326 Description of the Affected Resources and Impact Analysis

Alternative A in Chapter 4.9.2.2. Impacts to commercial fisheries resources from an accidental fuel 

spill or small diesel fuel spill would be nominal under Alternative D.

4.9.5.3 Cumulative Impacts

Impact analyses presented in Chapters 4.9.5.1 and 4.9.5.2 determined that activities 

projected to occur under Alternative D would result in nominal to minor impacts to commercial 

fisheries, depending on the IPF.

Mitigation measures for the proposed action under Alternative D are described in 

Chapter 2.4 and summarized in Chapter 4.9.5.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.9.2.3). The mitigation measures are the 

same as described for Alternative C with the addition of shutdown protocols during seismic 

operations for all marine mammals (except bow-riding dolphins). The addition of shutdown protocols 

for all marine mammals, except bow-riding dolphins, under Alternative D would not change the 

extent, severity, or timing of activities in the proposed action; thus, the resultant impacts to 

commercial fisheries also would not change. Therefore, the mitigation measures under Alternative D 

do not change the cumulative outcomes described in Alternative A (Chapter 4.9.2.3); there would be 

a minor incremental increase in impacts to commercial fisheries from active acoustic sound sources 

and stand-off distances, and a nominal incremental increase in impacts to commercial fisheries 

from vessel traffic, seafloor disturbances, entanglement, and accidental fuel spills.

4.9.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.9.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative E on commercial fisheries.

4.9.6.1 Impacts of Routine Activities

The reduction of deep-penetration, multi-client activities by 10 percent or 25 percent would 

reduce the extent, severity, and timing of active acoustic sound sources, vessel traffic, stand-off 

distance, and seafloor disturbance compared with Alternative A. The analysis in Alternative A 

concluded that impacts from active acoustic sound sources, vessel traffic, stand-off distance, 

seafloor disturbance, and entanglement would range from nominal to minor. The reduction in 

activity would not change the overall impacts for these IPFs and, thus, the impacts would remain 

nominal to minor for commercial fisheries under Alternatives E1 and E2.

As discussed in Chapter 4.9.2.1, impacts of active acoustic sound sources are expected to 

be minor for commercial fisheries under Alternative A. Under Alternatives E1 and E2, there would 

be a 10 percent or 25 percent reduction in activities, respectively, for deep-penetration, multi-client 

activities. A reduction in activities under Alternatives E1 and E2 could reduce the impacts of 

acoustic sound sources from certain seismic airgun surveys on commercial fisheries. However, 

seismic airgun surveys will still be conducted throughout the AOI, and the majority of commercial fish 
Gulf of Mexico G&G Activities Programmatic EIS 4-327

resources will still be impacted by airguns. The effects will likely still include displacement of fish or 

extensive disruption of fish hearing and behavior (discussed in detail in Chapter 4.4.2.1) that may 

adversely affect some populations. Furthermore, this may continue to indirectly affect commercial 

fisheries because impacts to fish hearing and behavior could result in a reduction in commercial 

fisheries catch rates (discussed in detail in Chapter 4.9.2.1). Therefore, a reduction in deeppenetration, multi-client activities will not change the overall impacts under Alternatives E1 and E2. 

The impacts of active acoustic sound sources from seismic airguns are expected to be minor for 

commercial fisheries under Alternatives E1 and E2. The mitigation measure does not apply to 

sound sources from non-airgun HRG surveys; therefore, the impact from electromechanical sources 

will be nominal for commercial fisheries under Alternatives E1 and E2.

Under Alternatives E1 and E2, there would be a 10 percent or 25 percent reduction in 

activities, respectively, for deep-penetration, multi-client activities. However, many activities will 

continue, and seismic and HRG surveys will continue throughout the AOI. Impacts to commercial 

fisheries still are likely to be detectable, with the potential for localized, short-term interruption of 

commercial fishing activities or localized gear damage in areas where activity is concentrated. 

Alternative E1 would not change the impacts to commercial fisheries landings arising from vessel 

traffic, stand-off distance, and entanglement, and impacts are expected to remain between nominal

and minor. Alternative E2, a reduction of deep-penetration, multi-client surveys by 25 percent, 

would result in a decrease in large arrays that have greater stand-off distances and the highest 

potential for entanglement with commercial fishing operations; therefore, impacts from stand-off 

distances and entanglement under Alternative E2 would be reduced to nominal. 

Operational reductions under Alternatives E1 and E2 would not reduce seafloor-sampling 

activities requiring the placement of anchors, nodes, cables, or other bottom-founded equipment 

used to support these types of surveys (Chapter 2.7). The possibility remains that a particular 

seafloor disturbance, no matter how small, may occur within a productive fishing area as discussed 

under Alternative A. Therefore, seafloor disturbance and its impact to commercial fishing operations 

and potential effects on commercial fishery landings are expected to remain limited and localized, 

with the potential to overlap with productive fishing grounds. Therefore, impacts are expected to 

remain minor depending on the location under Alternatives E1 and E2. 

4.9.6.2 Impacts of an Accidental Fuel Spill

Under Alternatives E1 and E2, impacts of accidental fuel spills on commercial fisheries would 

be very similar to those analyzed for Alternative C in Chapter 4.9.4.2. Alternatives E1 and E2 would 

reduce the number of surveys and vessels conducting deep-penetration, multi-client surveys by 

10 percent or 25 percent, respectively, but this reduction would not substantially change the risk of a 

small fuel spill because the majority of activities will continue to take place. A small diesel spill is 

expected to disperse and weather rapidly, with evaporation of volatile components. The impacts 

would depend on the size and location of the spill, in addition to the meteorological conditions. 

Impacts to commercial fisheries resources from an accidental fuel spill or small diesel fuel spill would 

be nominal under Alternatives E1 and E2.
4-328 Description of the Affected Resources and Impact Analysis

4.9.6.3 Cumulative Impacts

Impact analyses presented in Chapters 4.9.6.1 and 4.9.6.2 determined that activities 

projected to occur under Alternative E would result in nominal to minor impacts to commercial 

fisheries, depending on the IPF.

Mitigation measures for the proposed action under Alternative E are described in 

Chapter 2.5 and summarized in Chapter 4.9.6.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.9.2.3). The reduction of deeppenetration, multi-client activities (in line miles) by 10 percent (Alternative E1) or 25 percent 

(Alternative E2) would reduce the extent, severity, and timing of active acoustic sound sources, 

vessel traffic, stand-off distances, seafloor disturbance, and entanglement; therefore, impacts for 

these IPFs would be incrementally decreased under Alternative E. However, the incremental 

decrease in impacts to commercial fisheries is not to the extent that overall cumulative impacts 

would change from the outcomes described in Alternative A; and, there would be a minor

incremental increase in impacts to commercial fisheries from active acoustic sound sources and 

stand-off distances, and a nominal incremental increase in impacts to commercial fisheries from 

vessel traffic, seafloor disturbances, entanglement, and accidental fuel spills.

4.9.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.9.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative F on commercial fisheries.

4.9.7.1 Impacts of Routine Activities

4.9.7.1.1 Closure Areas

Alternative F would require area closures in the CPA Closure Area, EPA Closure Area, Dry 

Tortugas Closure Area, and Flower Gardens Closure Area (Figure 2.6-1). The closures apply to all 

G&G activities, which would reduce the impacts of active acoustic sound sources, vessel traffic, 

stand-off distance, seafloor disturbance, and entanglement on commercial fisheries. The analysis in 

Alternative A concluded that impacts from active acoustic sound sources, vessel traffic, stand-off 

distance, seafloor disturbance, and entanglement on commercial fisheries would range from 

nominal to minor. The purpose of this mitigation measure is to provide protection to marine 

mammals within these closure areas. This mitigation measure would provide an ancillary benefit to 

some coastal and oceanic fish species (refer to Appendix E), as the effects on fish hearing and 

behavior (discussed in detail in Chapter 4.4.2.1) will be reduced following a reduction in active 

acoustic sound sources (e.g., seismic airgun and electromechanical sounds). This may also 

indirectly benefit commercial fisheries because a reduction in the impact to fish hearing and behavior 

could result in a reduction in the indirect impacts to commercial fisheries catch rates (discussed in 

detail in Chapter 4.9.2.1). Another benefit would be a reduction in vessel traffic, stand-off distance, 

and entanglement from seismic surveys during the closure period, which will subsequently reduce 

the potential for damage to fishing gear or loss of access of fishing grounds. Lastly, a reduction in 
Gulf of Mexico G&G Activities Programmatic EIS 4-329

seafloor-disturbing activities could be beneficial to certain demersal fish species (refer to 

Appendix E) and may reduce indirect impacts to bottom fisheries. However, impacts from active 

acoustic sound sources, vessel traffic, stand-off distance, seafloor disturbance, and entanglement 

will still occur throughout the AOI. The sum of all closure areas is small compared with the size of 

the AOI, and impacts will only be reduced within the closure areas. Thus, there will not be a 

substantial reduction in seismic survey activity in the AOI; the overall impacts on commercial 

fisheries would not change under Alternative F and would remain nominal to minor. 

4.9.7.1.2 Routine Activities Impact Conclusions

Impacts of active acoustic sound sources, stand-off distance, and entanglement from seismic 

airgun surveys are expected to range from nominal to minor, and impacts from non-airgun HRG 

surveys and vessel traffic will remain nominal under Alternative F for commercial fisheries. Impacts 

from seafloor-disturbing activities would remain minor. 

4.9.7.2 Impacts of an Accidental Fuel Spill

Under Alternative F, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. Alternative F would change the location where survey vessels could conduct G&G 

activities; however, spills from seismic airgun surveys, non-airgun HRG surveys, and other G&G 

activities could still occur within the AOI. The sum of the closure areas is small compared with the 

size of the AOI, and impacts will be reduced but only within the closure areas. Thus, impacts of 

accidental fuel spills on commercial fisheries would be very similar to those analyzed for 

Alternative A in Chapter 4.9.2.2. Impacts to commercial fisheries resources from an accidental fuel 

spill or small diesel fuel spill would be nominal under Alternative F.

4.9.7.3 Cumulative Impacts

Impact analyses presented in Chapters 4.9.7.1 and 4.9.7.2 determined that activities 

projected to occur under Alternative F would result in nominal to minor impacts to commercial 

fisheries, depending on the IPF.

Mitigation measures for the proposed action under Alternative F are described in Chapter

2.6 and summarized in Chapter 4.9.7.1. A detailed impacts assessment under the cumulative 

scenario is provided in Alternative A (Chapter 4.9.2.3). Mitigation measures under Alternative F are 

similar to Alternative C with the addition of area closures in four areas: the CPA Closure Area; the 

EPA Closure Area; the Dry Tortugas Closure Area; and the Flower Gardens Closure Area. Most 

mitigation measures under Alternative F would not change the extent, severity, or timing of activities 

in the proposed action; thus, the resultant impacts to commercial fisheries also would not change the 

cumulative outcomes described in Alternative A (Chapter 4.9.2.3). There would be a minor

incremental increase in impacts to commercial fisheries from active acoustic sound sources and 

stand-off distances, and a nominal incremental increase in impacts to commercial fisheries from 

vessel traffic, seafloor disturbances, entanglement, and accidental fuel spills.
4-330 Description of the Affected Resources and Impact Analysis

4.9.8 Impacts – Alternative G (No New Activity Alternative)

The IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.9.2) except that the IPF of entanglement is not included as part of 

Alternative F because no OBC surveys are part of the alternative.

4.9.8.1 Impacts of Routine Activities 

Under Alternative G, no new permits/authorizations will be issued for G&G activities. 

Previously authorized activities would still occur under existing agreements or 

permits/authorizations, but would drop off quickly. The VSP (2D only) and SWD surveys would 

continue at the level of activity in Table 2.7-1. The VSP surveys cover fewer line miles and shorter 

distances, use less sound energy, and most are completed in a few days (Appendix F, Section

1.1.5). Thus, impacts from active acoustic sound sources, vessel traffic, stand-off distances, 

seafloor disturbance, and entanglement would not change immediately, but would decrease over 

time. Impacts from other routine activities would also decrease over time. Therefore, impacts from 

routine activities on commercial fisheries would remain similar to Alternatives A and C in the 

immediate (nominal to minor). As activity levels decrease, a substantial reduction in active 

acoustic survey activities (non-VSP and SWD) would likely reduce impacts from all routine activities

on commercial fisheries to nominal. 

4.9.8.2 Impacts of Accidental Fuel Spills

Under Alternative G, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. No new permits/authorizations will be issued for G&G activities. Previously authorized 

activities would still occur under existing agreements or permits/authorizations, but would drop off 

quickly. Subsequently, VSP surveys will continue to be permitted. Thus, impacts of accidental fuel 

spills on commercial fisheries would be very similar to those analyzed for Alternatives A and C in 

Chapters 4.9.2.2 and 4.9.4.2. Impacts to commercial fisheries from an accidental fuel spill or small 

diesel fuel spill would be nominal declining to no impact. 

4.9.8.3 Cumulative Impacts

Impact analyses presented in Chapters 4.9.8.1 and 4.9.8.2 determined that activities 

projected to occur under Alternative G would result in nominal to minor impacts to commercial 

fisheries, depending on the IPF.

A detailed impacts assessment under the cumulative scenario is provided in Alternative A 

(Chapter 4.9.2.3). The cease of activity for future G&G surveys requiring a permit/authorization 

from BOEM would substantially decrease the cumulative impacts from all IPFs. However, VSP and 

SWD surveys are expected to continue under Alternative G. Therefore, following cessation of the 

majority of activities, there would be a nominal incremental increase in impacts to commercial 

fisheries from active acoustic sound sources, vessel traffic, stand-off distances, seafloor 

disturbances, entanglement, and accidental fuel spills under Alternative G.
Gulf of Mexico G&G Activities Programmatic EIS 4-331

4.10 RECREATIONAL FISHERIES

4.10.1 Description of the Affected Environment

Saltwater recreational fisheries in States adjacent to the AOI are among the most valuable in 

the U.S. In 2012, total fishing trip and durable equipment expenditures were $10 billion, and major 

expenditures included boat expenses ($4.8 billion), fishing tackle ($1.4 billion), vehicle expenses 

($1.2 billion), second home expenses ($896 million), and other equipment ($558 million). In 2012, 

west Florida ranked first ($9.1 billion) and Louisiana ranked third ($2 billion) nationally in sales 

impacts from total expenditures related to recreational fishing (USDOC, NMFS, 2014). Among the 

Gulf Coast States, the number of trips, jobs, sales, income, and value-added impacts from 

recreational fishing were highest in Florida (west coast) in 2012 (Table 4.10-1).

Recreational fishing is a year-round activity throughout the AOI and can be classified as a 

nearshore or offshore effort, depending on the size of the vessel and its fishing location (distance 

from shore); the majority of the activity takes place in nearshore waters. Nearshore recreational 

fishing (<4.8 km [3 mi]) consists of anglers fishing from private vessels and along beaches, marshes, 

or man-made structures (e.g., jetties, docks, and piers), while offshore fishing consists of anglers 

fishing from larger vessels (i.e., private, rental, charter, or party) in offshore waters (>4.8 km [3 mi]). 

In 2013, the majority of recreational fishing trips were from Florida (60%), while other Gulf Coast 

States accounted for 18 percent (Louisiana), 11 percent (Alabama), 7 percent (Mississippi), and 

4 percent (Texas) of the total number of trips (USDOC, NMFS, 2014). Refer to Table 4.10-2 for the 

number of fishing trips taken between 2003 and 2012.

Marine fishes depend on and utilize many different types of habitats (e.g., seagrass, salt 

marsh, soft bottom, hard bottom) for feeding, spawning, and nursery grounds. Therefore, 

recreational anglers have many options to target various species in these habitats. The choice of 

fish species targeted by recreational anglers depends on the season, fishing location, and seasonal 

movement of that particular species. For example, bottom fishing for snapper, grunts, and porgies 

increases during the summer months, while grouper fishing is best during winter months. 

Table 4.10-3 provides harvest and release numbers of key species and species groups from 2003 to 

2012.

Organized saltwater fishing tournaments are popular amateur and professional events that 

are held throughout the AOI from Texas to Florida (Table 4.10-4). Recreational fishing tournaments 

are held year-round, but most take place in summer during weekends. Depending on the fishing 

tournament and its rules, participants have the option to target inshore (e.g., red drum, spotted 

seatrout, and snook) or offshore (e.g., dolphinfish, wahoo, and kingfish) categories, or to enter both 

categories. Throughout the AOI, there are many fishing tournaments that are annual events; 

however, it is difficult to identify every possible tournament given that some tournaments are only 

one time events and sponsorships can change from year to year.
4-332 Description of the Affected Resources and Impact Analysis

Deepwater Horizon Oil Spill

Impacts from the Deepwater Horizon oil spill, including oiled shorelines and the closing of 

areas to recreation, resulted in losses to the public’s use of natural resources for outdoor recreation. 

The Final PDARP/PEIS includes an assessment of “lost recreational use” that focuses on two broad 

categories of recreation: shoreline use and boating (Deepwater Horizon Natural Resource Damage 

Assessment Trustees, 2016). Both categories include, but are not limited to, recreational fishing, 

e.g.,, boating includes any non-commercial boating activity and shoreline use includes other 

recreational activities such as swimming, sunbathing, surfing, walking, and kayaking. The following 

text summarizes the impacts to recreational fishing that were noted within the broader context of 

“lost recreational use,” as the Final PDARP/PEIS does not provide a separate analysis of impacts on 

recreational fishing.

The Deepwater Horizon oil spill resulted in losses to the public’s use of natural resources in 

the GOM for outdoor recreation, including fishing (Deepwater Horizon Natural Resource Damage 

Assessment Trustees, 2016). The impacts started in May 2010 and lasted through at least 

November 2011. The Final PDARP/PEIS estimates that the public lost 16,857,116 user days of 

fishing, boating, and beach-going experiences because of the oil spill. Total recreational use 

damages due to the oil spill are estimated to be $693.2 million with uncertainty ranging from $527.6 

million to $858.9 million. This lost value does not include losses to private businesses/individuals or 

lost tax revenue to municipalities. Recreational losses due to the oil spill affected sites in the States 

of Texas, Louisiana, Mississippi, Alabama, and Florida; however, residents throughout the U.S. were 

included as part of the affected public.

The most direct impact on recreational fishing activities in the AOI was due to the fishing 

areas closures in oil-impacted areas. At its peak on June 2, 2010, 37 percent of the Federal EEZ 

was closed to fishing. Between 2009 and 2010, the number of recreational angler trips in State and 

Federal waters (excluding inland) off the States of Louisiana, Mississippi, Alabama, and Florida 

cumulatively decreased by 37 percent in the March/April wave, 24 percent in the May/June wave, 

and 36 percent in the July/August wave (USDOC, NMFS, 2013c). A 123 percent increase in angler 

trips was noted between 2009 and 2010 in September/October, but activity decreased again in 

November/December (34%), indicating that the increase in September/October was temporary. 

Recreational angler trips after the spill showed growth as compared with pre-spill years. For 

example, the cumulative number of angler trips in State and Federal waters (excluding inshore) off

the States of Louisiana, Mississippi, Alabama, and Florida increased from 6.1 million trips in 2011 to 

7.1 million trips in 2012 and 10.2 million trips in 2013, an increase of 67 percent from 2011 and an 

increase (38%) from the 7.4 million trips taken by anglers before the spill in 2009 (USDOC, NMFS, 

2013c).

Recreational fish landings (in State and Federal waters [excluding inshore] of the States of

Louisiana, Mississippi, Alabama, and Florida) for most species only fell slightly between 2009 and 

2011, but substantial declines were recorded for offshore species such as gray snapper 

(30 decrease), red snapper (31% decrease), king mackerel (63% decrease), and red grouper 
Gulf of Mexico G&G Activities Programmatic EIS 4-333

(26% decrease) (USDOC, NMFS, 2013c). In 2013, a substantial increase was observed for the gray 

snapper (approximately 100%), red snapper (98%), king mackerel (72%), and red grouper (60%) 

from 2011. Long-term effects of the Deepwater Horizon explosion, oil spill, and response on 

recreational fisheries are difficult to quantify given that oil is more toxic to fish eggs and larvae than 

to adults. Long-term impacts on any particular species may take many years for the effects on one 

year’s cohorts to be realized. Recreational fisheries are also highly dependent on local tourism and 

the socioeconomic status of the states that border the AOI. However, in general, recreational fishing 

activity stabilized subsequent to the short-term fluctuations in recreational fishing activity subsequent 

to the Deepwater Horizon (USDOC, NMFS, 2016c). Additional information pertaining to this 

resource and NMFS’ determination of the effects of the Deepwater Horizon explosion, oil spill, and 

response may be found in the Final PDARP/PEIS (Deepwater Horizon Natural Resource Damage 

Assessment Trustees, 2016).

4.10.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, the IPFs that may impact recreational fisheries within the AOI 

include (1) active acoustic sound sources (e.g., airguns; non-airgun HRG sources such as highresolution boomers, sparkers, and CHIRP subbottom profilers; SBESs and MBESs; and side-scan 

sonars), (2) vessel traffic, (3) stand-off distance, and (4) accidental fuel spills.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact level categories. In contrast, the analysis 

of impacts associated with Alternatives B through G are organized by alternative-specific mitigation 

measures and how each these measures may reduce impact levels.

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For recreational 

fisheries, the below significance criteria have been used to evaluate the level of impact for each IPF.

Nominal impacts to recreational fisheries would include those with little to no measurable 

impacts observed or expected.

Minor impacts to recreational fisheries would include those that are detectable but not 

severe or extensive. Minor impacts to recreational fisheries would include localized, short-term 

interruption of recreational fishing activities, as well as localized, less than severe impacts on fish 

resources with minimal decreases in recreational fisheries landings.

Moderate impacts to recreational fisheries would be detectable and extensive but not 

severe. Moderate impacts to recreational fisheries would include extensive but infrequent 
4-334 Description of the Affected Resources and Impact Analysis

interruption of recreational fishing activities and extensive but not severe impacts on fish resources 

(i.e., not sufficient to result in sizable decreases in recreational fisheries landings).

Major impacts to recreational fisheries would be detectable, extensive, and severe. Major 

impacts to recreational fisheries would include extensive, frequent interruption of recreational fishing 

activities and extensive, severe impacts on fish resources (i.e., sufficient to result in sizable 

decreases in recreational fisheries landings).

4.10.2.1 Impacts of Routine Activities

Active Acoustic Sound Sources

The spatial and temporal characteristics of active acoustic sound sources vary depending on 

the type of activity. As discussed in Chapter 4.4.2.1, HRG surveys may take several days and 

cover smaller areas, whereas seismic (i.e., 2D, 3D, 4D, WAZ, and VSP) surveys may occur 

throughout significant portions of the AOI and for weeks, months, or even up to a year. Depending 

on the equipment and technique, airgun seismic pulses typically are fired from one or two vessels 

and are emitted at intervals of 5 to 60 seconds. Under the activity scenario, surveys using these 

types of equipment would be conducted throughout the AOI, but the majority of activity will take 

place in the WPA and CPA. 

Sound is used by fishes in a variety of ways, as outlined in Chapter 4.4.2.1. In general, 

fishes use sound to obtain an instant image of their surroundings in terms of biotic (living) and abiotic 

(environmental) sources. Many bony fishes can communicate with sound; some fishes use sound 

during mating and territorial interactions. Potential direct effects on fishes from anthropogenic 

sounds (e.g., airguns and echosounders) include changes in hearing abilities (masking or TTS), 

behavioral changes, injury, and mortality (discussed in detail in Chapter 4.4.2.1 and Appendix I).

Reef Fishes: It is unlikely that sounds generated from G&G equipment would cause any 

mortality to reef fishes such as groupers and snappers because Alternative A includes the use of 

ramp-up as part of the survey protocol. Research results suggest that exposure to noise from 

seismic airguns and electromechanical sounds (e.g., side-scan sonars and echosounders) would not 

produce serious injury or mortality to reef fishes. Song et al. (2008) and Kane et al. (2010) found 

that sound generated from seismic and sonar devices showed no tissue damage to fishes. 

Halvorsen et al. (2011a,b) reported that Chinook salmon was affected by sounds generated from 

simulated pile-driving procedures, but specimens showed complete recovery under laboratory 

conditions after a short period following exposure. Enger (1981) and McCauley et al. (2003) 

reported that Atlantic cod and pink snapper exhibited small losses of sensory cells after being 

exposed to high-intensity sounds, but fishes recovered shortly after exposure as well. The limited 

information on the effects of sonar indicate that behavior of certain species does not change when 

exposed to sound from these devices (Doksaeter et al., 2009, 2012; Sivle et al., 2012). Based on 

these studies and due to the mitigation measures in place, it is unlikely that the sounds produced by 

airguns for seismic surveys and electromechanical sources for HRG surveys would cause injury or 

mortality to reef fishes such as groupers and snappers under Alternative A. In general, impacts to 
Gulf of Mexico G&G Activities Programmatic EIS 4-335

fish hearing and behavior are more likely. However, changes in fish behavior and hearing will not 

occur in all fish species and effects will be temporary (discussed in Chapter 4.4.2.1; refer also to

Popper et al., 2005). Therefore, there will be little to no measurable impacts to reef fishes. Impacts 

on reef fishes, as a component of recreational fisheries, would be nominal under Alternative A.

Coastal Fishes: Fishes found along coastal beaches and inlets are among the most 

popular fishes pursued by recreational anglers. In general, anglers fish inshore and outside of the 

AOI (USDOC, NMFS, 2011b); however, the majority of the fishing activity occurs along nearshore 

coastal areas (i.e., <4.8 km [3 mi] from shore), which may be affected by sound generated by 

seismic equipment. Popular recreational fishes harvested along coastal beaches and nearshore 

waters include bluefish, pompano, cobia, spotted seatrout, pinfishes, drums, Spanish mackerel, and 

Atlantic croaker. Despite the fact that these inshore fishes are generally found in much shallower 

waters than reef fishes (e.g., groupers and snappers), there is no scientific evidence to suggest that 

these species are more vulnerable to active acoustic sound generated by seismic and HRG surveys. 

Based on available data and due to the mitigation measures in place, it is unlikely that the sounds 

produced by airguns for seismic surveys and electromechanical sources for HRG surveys would 

cause injury or mortality to inshore and coastal fishes under Alternative A. In general, impacts to fish 

hearing and behavior are more likely. However, changes in fish behavior and hearing will not occur 

in all fish species and effects will be temporary (discussed in Chapter 4.4.2.1; refer also to Popper 

et al., 2005). Therefore, there will be little to no measurable impacts to coastal fishes. Impacts to 

coastal fishes, as a component of recreational fisheries, would be nominal under Alternative A.

Pelagic Fishes: Recreational anglers often target pelagic species such as tuna, billfishes, 

and sharks throughout the offshore waters of the AOI. It is possible that seismic sounds may 

temporarily affect the catchability of recreationally targeted species, but it is very unlikely that these 

types of sounds would cause mortality in tuna, billfishes, and pelagic sharks. In general, these 

fishes display highly migratory behavior and are adapted to continuously swim. Therefore, the 

chance of these fishes being exposed to seismic sounds at a level that could cause mortality is 

extremely unlikely, especially because the seismic vessel and fishes are continually moving. 

Furthermore, ramp-up procedures are expected to minimize any potential impacts to migratory 

fishes. Based on available data and due to the mitigation measures in place, it is unlikely that the 

sounds produced by airguns for seismic surveys and electromechanical sources for HRG surveys 

would cause injury or mortality to pelagic fishes. In general, impacts to fish hearing and behavior are 

more likely. However, changes in fish behavior and hearing will not occur in all fish species and 

effects will be temporary (discussed in Chapter 4.4.2.1; refer also to Popper et al., 2005). 

Therefore, there will be little to no measurable impacts to pelagic fishes. Impacts to pelagic fishes, 

as a component of recreational fisheries, would be nominal under Alternative A.

Recreational Fishing Activity: Anthropogenic sound generated from seismic activity under 

Alternative A has the potential to indirectly affect recreational fishing activities within the AOI. There 

is little scientific evidence to suggest that seismic sound would cause immediate mortality or 

physiological effects causing long-term injury in fishes. Nevertheless, effects such as changes in 

hearing abilities or behavior that indirectly cause localized short-term interruptions of recreational 
4-336 Description of the Affected Resources and Impact Analysis

fishing activities may be expected, and slight decreases in recreational fisheries landings may occur. 

Given the absence of serious injury or mortality to recreational fishes and the low potential for 

behavioral changes from active acoustic sound exposure to airguns for seismic surveys and 

electromechanical sources for HRG surveys, it is likely that potential impacts would be intermittent, 

temporary, and short term in duration or frequency. Exposure to active acoustic sound sources 

(e.g., seismic airgun and electromechanical sounds) from G&G activities under Alternative A is 

expected to produce nominal impacts to recreational fisheries activities.

Vessel Traffic

Vessel traffic generated by each type of G&G survey proposed within the AOI is shown in 

Table 3.2 7, and the types of surveys and activity level scenarios are described in Chapter 3. 

Furthermore, existing vessel activity within the GOM is described in Chapter 3.4.3. 

Under Alternative A, vessel traffic could increase slightly in specific areas, and resultant 

impacts from vessel traffic would be stand-off distances. Generally, most recreational anglers fish 

(usually trolling, drifting, or bottom fishing) according to specific habitats (bottom profile) or water 

conditions. Catch rates may be adversely affected as they are not only dependent upon the 

numbers of fishes and location but also on fishing techniques. Because recreational anglers 

generally are in small maneuverable boats using rod-and-reel or electric reels with easily retrievable 

lengths of line in the water, avoiding large survey vessels would be relatively easy. Inshore fisheries 

(i.e., estuaries and bays) are not expected to be affected by vessel issues because they are outside 

of the AOI. The exception would be coastal inlets, as mentioned previously. Effects are likely to be 

localized at several locations, intermittent in frequency of occurrence, temporary, and short term in 

nature. Impacts to recreational fishing are not expected to increase under Alternative A because 

vessel traffic is relatively high in the AOI and G&G activities have been ongoing in the area. 

Therefore, vessel traffic disturbance and resultant stand-off distances would be expected to produce 

nominal impacts to recreational fishing under Alternative A.

Stand-Off Distance

During seismic airgun surveys, operators typically attempt to maintain a stand-off distance to 

protect towed-streamers from other vessel traffic and vice versa. The extent of the stand-off 

distance would depend on the equipment and number of streamers. Typical stand-off distance 

protocols are described in Chapter 3.3.1.5. 

The primary direct effect of a stand-off distance to recreational fisheries would be loss of 

access to fishing grounds and time. Given the amount of area occupied by the stand-off distance for 

these vessels, there is a potential for temporary space-use conflicts between G&G activities and 

recreational fishing operations within the AOI. Because of the stand-off distance, recreational fishers 

may have to retrieve lines earlier than usual to avoid seismic vessel surveys or stand down until the 

seismic vessel has moved past the fishing grounds and it is safe to reenter. Under Alternative A, 

G&G activities and the associated stand-off distance are expected to have no indirect effects on 

recreational fishery operations unless these activities cause recreational anglers to concentrate their 
Gulf of Mexico G&G Activities Programmatic EIS 4-337

fishing efforts on other species or areas. Impacts to recreational fisheries associated with stand-off 

distance under Alternative A are expected to be nominal under Alternative A.

4.10.2.1.1 Routine Activities Impact Conclusions

Overall, impacts from proposed activities to recreational fisheries are expected to be 

nominal. Impacts from active acoustic sound sources, vessel traffic, and stand-off distances would 

be intermittent, temporary, and short term in duration or frequency.

4.10.2.2 Impacts of an Accidental Fuel Spill

An accidental event could result in the release of fuel or diesel by a survey vessel. Based on 

USCG spill statistics, a spill scenario was developed in Chapter 3.3.2.1 that assumes a diesel spill 

volume of 1.2 to 7.1 bbl. Spills occurring at the ocean surface would disperse and weather. Volatile 

components of the fuel would evaporate. Fuel and diesel used for operation of survey vessels is 

light and would float on the water surface. There is the potential for a small proportion of the heavier 

fuel components to adhere to particulate matter in the upper portion of the water column and sink. 

Particulate matter contaminated with diesel fuel eventually could reach the seafloor within or outside 

the AOI, depending on spill location, water depth, ambient currents, and sinking rate.

Recreational fishing activity is not expected to be precluded from the area around the fuel 

source; spilled diesel would evaporate and disperse within a day or less. Given the relatively small 

size of the fuel spill and the rapid loss of most spilled fuel through evaporation and dispersion, a 

small diesel fuel spill at the surface would have little to no effect on recreational fisheries. An 

accidental fuel spill would be expected to result in nominal impacts to recreational fisheries under 

Alternative A.

4.10.2.3 Cumulative Impacts

Impact analyses presented in Chapters 4.10.2.1 and 4.10.2.2 determined that activities 

projected to occur under Alternative A would result in nominal impacts to recreational fishing.

The following analysis considers whether the incremental impact from the proposed action, 

when added to or acting synergistically with existing impact sources from the cumulative impacts 

scenario, may result in a significant collective impact to recreational fisheries.

4.10.2.3.1 Active Acoustic Sound Sources

The impacts from active acoustic sound sources from the proposed action are discussed in 

Chapter 4.10.2.1. Overall, Chapter 4.10.2.1 determined there would be increases in ambient noise 

levels within specific portions of the AOI during G&G operations, but nominal impacts to recreational 

fisheries.

All G&G survey activities associated with the OCS Program are included in the proposed 

action; therefore, G&G activities are not included in the cumulative analysis but instead are 
4-338 Description of the Affected Resources and Impact Analysis

addressed in the proposed action impact analysis. Active acoustic sound sources related to oil and 

gas development have been ongoing in the GOM for decades and are likely to be used in the future. 

As described in Chapter 4.10.2.1, active acoustic sound produced by seismic surveys conducted 

under the proposed action can influence fish behavior in ways that may impact recreational fishing 

catch or effort, but these effects are likely temporary.

The G&G activities associated with the proposed action will not be conducted within State 

waters. However, other agencies can permit G&G activities that can include active sound sources 

(e.g., seismic airguns and side-scan sonars for oil and gas activities in State waters). Sound 

produced by these surveys may propagate into coastal waters but will be significantly reduced in 

intensity proportional to the distance of seismic survey vessels from State waters boundaries and 

will, in most cases, add an insignificant amount to sound generated by similar sound sources 

operating in State waters. Effects of seismic sound propagating into State waters from G&G 

activities is likely to have an insignificant effect on recreational fishing when compared with sound 

caused by seismic vessels operating in State waters.

Other major factors that contribute active acoustic sound sources are shown in Table 3.4-1. 

Impacts to recreational fisheries from similar sound sources under the G&G proposed action are 

discussed in Chapter 4.10.2.1. Active acoustic sound sources from G&G activities considered in 

cumulative impacts assessment have been ongoing in the AOI for multiple decades and are likely to 

continue in the future. Anthropogenic sounds levels in the marine environment are increasing, and 

impacts fish behavior and hearing capabilities may impact recreational fishing (Slabbekoorn et al., 

2010; Radford et al., 2014). Yet, it is difficult to assess overall increases in sound because of the 

lack of baseline data from individual sound sources and the ambient sound conditions (Hawkins 

et al., 2014).

Activities associated with the proposed action would increase levels of active acoustic sound 

sources within the AOI, resulting in increases in ambient noise levels during G&G operations 

(primarily the WPA and CPA). Some impacts to recreational fishing is possible, but these impacts 

are likely temporary. Therefore, the cumulative effects of added project-related active acoustic 

sound sources would remain nominal under Alternative A. Seismic surveys are not conducted 

homogenously over the entire AOI nor homogenously over the 10-year period; thus, they are 

spatially and temporally limited and their impacts are not likely to increase over time.

4.10.2.3.2 Vessel Traffic

Impacts from vessel traffic to recreational fisheries from the proposed action are discussed in 

Chapter 4.10.2.1 and would be nominal. Support vessel traffic is a key part of most OCS Program 

activities (Chapter 3.4). Although recreational fishing and OCS activities have coexisted for many 

years within the AOI, support vessel traffic may interrupt some recreational fishing activity such as 

bottom fishing or trolling (Chapter 4.10.2.1). Recreational fishers are generally in small 

maneuverable boats using rod-and-reel or electric reels with easily retrievable lengths of line in the 

water, avoiding large survey vessels would be relatively easy.
Gulf of Mexico G&G Activities Programmatic EIS 4-339

Under the proposed action for activities within BOEM’s jurisdiction, seismic vessels and other 

support vessel traffic will operate primarily in Federal waters but will cross State waters when 

transiting to and from shore. Oil and gas vessels transiting State waters while departing from and 

returning to port will not be engaged in BOEM-managed G&G activities. Thus, such seismic and 

support vessels and recreational fishing watercraft can navigate to avoid each other.

Vessel traffic may result from other major factors shown in Table 3.4-1. Vessel traffic from 

the proposed action is discussed in Chapter 3.3.1.3. Vessel traffic from G&G operations under the 

proposed action would not represent a significant increase to existing vessel traffic from cumulative 

operations in coastal areas because the vessel traffic from the proposed action in the coastal 

environment will only involve support vessels transiting in and out of various ports along the Gulf 

Coast. Vessel traffic from G&G operations could increase to existing vessel traffic in offshore areas; 

however, advance notice of seismic survey activity is provided to fishers by seismic survey 

operators, and recreational fishing vessels can easily avoid larger vessels.

Considering the long-standing cooperative use of waters between recreational fishers and 

G&G-associated activities and the advance notice of seismic survey activity, effects from vessel 

traffic are not likely to significantly increase impacts from the cumulative scenario. Additionally, 

impacts would be temporary and localized to areas of vessel traffic and are not expected to increase 

over time. Therefore, when vessel traffic associated with the proposed action is added to existing 

traffic associated with the activities under the cumulative scenario component, there would be a 

nominal incremental increase in impacts to recreational fisheries.

4.10.2.3.3 Stand-off Distance

Impacts from stand-off distances to recreational fisheries from the proposed action are 

discussed in Chapter 4.10.2.1 and are expected to be nominal. Certain activities under the OCS 

Program are managed to provide an area, called the stand-off distance, around the activity to help 

avoid interactions between fishing vessels and oil and gas vessels that would be hazardous to 

vessels, crews, and gear. Stand-off distances under the G&G proposed action that are similar to 

those in OCS Program could cause temporary loss of access to fishing grounds and loss of fishing 

time. 

Under the proposed action, seismic survey vessels with large stand-off distances will operate 

only in Federal waters; however, non-surveying seismic vessels and other support vessel traffic will 

traverse State waters when departing from and returning to port. Non-surveying seismic vessels 

operating in State waters would not remain stationary, and impacts from stand-off distances would 

be short term and localized.

Stand-off distance may result from other major factors shown in Table 3.4-1. Stand-off 

distances resulting from these activities would cause similar impacts to those from seismic surveys 

from G&G activities. Stand-off distances from G&G activities are expected to cause temporary loss 

of access to fishing grounds and loss of fishing time. Stand-off distances from G&G activities will 
4-340 Description of the Affected Resources and Impact Analysis

have less of an impact when seismic survey vessels are not operating, for example, in coastal or 

State waters.

Loss of access to fishing grounds or delays in setting fishing gear in optimal locations may 

result in reductions in catch and quality of catch. This could ultimately affect recreational fishing. 

However, the majority of fishing will be done in State waters, where impacts from stand-off distances 

will be minimal. Therefore, when stand-off distance associated with the proposed action are added 

to activities in the cumulative scenario, there would be a nominal incremental increase in impacts to 

recreational fisheries.

4.10.2.3.4 Cumulative Impact Conclusions

Overall, proposed activities associated with the proposed action would increase levels of 

noise and vessel and aircraft traffic within the AOI, resulting in sporadic increases in ambient noise 

levels during proposed G&G operations. Sources of noise associated with the cumulative scenario 

that may affect recreational fisheries in the AOI include active acoustic sound, vessel traffic, standoff distance, and accidental fuel spills. Many of these IPFs may occur simultaneously during some 

projected operations under the OCS Program.

The spatial distribution of activities projected under the proposed action during the project 

period are most concentrated within deepwater regions of the CPA and WPA, and less concentrated 

within continental shelf waters (Table 3.2-1). Very little activity is projected to occur within the EPA. 

Temporally, activity levels associated with the proposed action vary by activity type and year (Tables

3.2-1 through 3.2-5). Overall, proposed activities are expected to result in nominal to minor

incremental increases in impacts to commercial fisheries.

4.10.2.3.5 Accidental Fuel Spills

As discussed in Chapter 3.4, the AOI includes an extensive system of offshore oil and gas 

production facilities. The potential for fuel spills from vessels involved in the cumulative scenario 

would be higher than that expected under the proposed action because of the magnitude of vessel 

activity in the AOI and the high number of vessel transits. However, the potential for collision and 

product transfer fuel spills from vessels involved in the cumulative activities scenario is considered 

remote because of the small number of vessels, the type of vessels and required fuels, the 

standards and protocols for management of vessel fuels, and the aids to navigation and crew 

training for vessels likely to be used under the proposed alternative. With the use of AIS on large 

sea-going vessels, radar, and licensing of vessel captains, the potential of a vessel collision 

occurring is low, and the potential for a resultant spill is even lower. Fuel and diesel used for the 

operation of support vessels is light and would float on the sea surface where is it subjected to 

weathering, dispersion, and dissolution. Heavier fuels may be used in larger commercial vessels 

involved in marine transportation. Thus, the increase in potential for accidental fuel spills arising 

from vessel collision during G&G activities would be considered extremely small.
Gulf of Mexico G&G Activities Programmatic EIS 4-341

The G&G activities associated with the proposed action will not be conducted within State 

waters. However, vessels involved with G&G activities may transit through State waters. Because 

the majority of the activities associated with proposed action will not occur in State waters, there is a 

low probability of a G&G activity-related fuel spill under the State waters oil and gas component or 

that fuel spilled in Federal waters would be transported into State waters. Thus, the potential for 

spills from vessels involved in the cumulative activities scenario is remote, and it is anticipated that, if 

a spill occurred, the spill size would be relatively small, the type of fuel that would likely be spilled 

would rapidly dissipate, and the area impacted would be a small.

Accidental fuel spills are probable from support vessels associated with other major factors 

(Table 3.4-1). As discussed earlier, the potential for collision and product transfer fuel spills from 

vessels involved in the cumulative activities scenario is considered remote. Fuel and diesel used for 

operation of support vessels is light and would float on the sea surface where is it subjected to 

weathering, dispersion, and dissolution. Heavier fuels may be used in larger commercial vessels 

involved in marine transportation. The potential for fuel spills from vessels involved in the offshore 

development component of the cumulative scenario would be higher than that expected under the 

proposed action because of the magnitude of vessel activity in the AOI and the high number of 

vessel transits. Thus, the increase in potential for accidental fuel spills arising from vessel collision 

during G&G activities would be considered extremely small.

The only IPF associated with natural events and processes that may impact recreational 

fishing is accidental fuel spills caused by hurricanes or weather events. Multiple and wide-ranging 

accidental spills can occur as a result of these periodic events. An extreme climatic event can cause 

additional accidents, damage OCS infrastructure, and result in oil and fuel leaks (Chapter 3.4.5). 

However, no G&G surveys would occur during an extreme climatic event, and there would not be a 

cumulative impact from a G&G vessel.

Activities associated with all cumulative scenario components have the potential to cause an 

accidental fuel spill (Table 3.4-1). If accidental fuel spills from the cumulative scenario activities 

coincided spatially and temporally with an accidental fuel spill from G&G vessels, then cumulative 

impacts to recreational fishing could be exacerbated. Impacts from G&G vessels are most likely to 

be cumulative with OCS Program activities because of the higher number of vessels and greater 

spatial overlap between activities. Fuel and diesel used for the operation of support vessels is light 

and would float on the sea surface where is it subjected to weathering, dispersion, and dissolution. 

There are also several mitigation measures in place to avoid vessel collisions. Therefore, impacts 

from accidental fuel spills from G&G activities will be spatially and temporally limited and would 

result in a nominal incremental increase in impacts to recreational fishing under the cumulative 

scenario.
4-342 Description of the Affected Resources and Impact Analysis

4.10.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.10.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative B on recreational fisheries.

4.10.3.1 Impacts of Routine Activities

Additional mitigation measures under Alternative B that would not change the extent, 

severity, or timing of G&G activities, and therefore related recreational fisheries, include the 

expansion of NTL 2012-JOINT-G02 (inclusion of manatees and application to all deep-penetration 

seismic airgun surveys in all water depths) and the expanded use of PAM. As such, those mitigation 

measures will not be addressed in the following discussion.

4.10.3.1.1 Seasonal Restriction for Federal Coastal Waters (January 1 to April 30)

Alternative B would require seasonal restrictions for seismic airgun survey operations in 

Federal coastal waters of the GOM shoreward of the 20-m (66-ft) isobath between January 1 and 

April 30 (Figure 2.2-1). The impacts of active acoustic sound sources, vessel traffic, and stand-off 

distance would be reduced, but only within coastal waters between January 1 and April 30. The 

closure area would be 9,032,418 ha (22,319,105 ac), 13.1 percent of the area of the AOI 

(68,916,602 ha [170,292,924 ac]). The purpose of this mitigation measure is to provide protection to 

marine mammals within these closure areas from the IPFs associated with deep-penetration seismic 

airgun surveys. This mitigation measure would provide an ancillary benefit to some coastal fish 

species (Tables 4.4-1, 4.4-2, and 4.4-4) as the effects on fish hearing and behavior (discussed in 

detail in Chapter 4.4.2.1) would be reduced in the coastal seasonal restriction area. Furthermore, 

this may indirectly benefit recreational fisheries because a reduction in the impact to fish hearing and 

behavior could result in a reduction of the indirect impacts to recreational fisheries catch rates. 

Another benefit would be a reduction in vessel traffic and stand-off distance from seismic surveys 

during the closure period that will subsequently reduce the potential for damage to fishing gear or 

loss of access of fishing grounds. However, seismic surveys will still occur outside this area, the 

closure timeframe is temporary, and the closure area is small compared with the size of the AOI. 

Thus, while a change in survey timing in the coastal seasonal restriction area would slightly reduce 

the impacts of active acoustic sound sources, vessel traffic, and stand-off distance from seismic 

airguns surveys on recreational fisheries, it would not change the overall impact level. Therefore, 

impacts are expected to be nominal for recreational fisheries under Alternative B. The mitigation 

measure does not apply to sound sources from non-airgun HRG surveys; therefore, the impact from 

electromechanical sources will be nominal for recreational fisheries under Alternative B.

4.10.3.1.2 Minimum Separation Distances

Alternative B would establish a 40-km (25-mi) separation distance between simultaneously 

operating deep-penetration seismic airgun surveys within the Areas of Concern (Chapter 2.2.2) to 

limit ensonification of specific areas of the AOI at the same time. When outside the Areas of 

Concern, the separation distance shall be 30 km (19 mi). However, the separation distance 
Gulf of Mexico G&G Activities Programmatic EIS 4-343

requirement does not apply to multiple ships operating in a coordinated survey such as a WAZ 

survey, and it need not be maintained if unsafe or due to weather conditions. It is anticipated that, 

through the adaptive management approach outlined in Chapter 2, this separation distance may be 

modified based on newly available information and in consideration of any other surveys requested 

or authorized to operate concurrently (if any).

Applicable routine IPFs for recreational fisheries are active acoustic sound sources, vessel 

traffic, and stand-off distance. Limits on concurrent seismic airgun surveys under Alternative B could 

change the timing of seismic surveys in certain areas. The locations cannot be predicted in 

advance, but this would depend on the schedule, planned coverage of individual surveys, and ports 

to be used for support activities. Seismic surveys will still be conducted; therefore, a change in the 

survey timing because of limits on concurrent seismic airgun surveys would not alter the impacts 

from active acoustic sound sources (including seismic airguns and electromechanical sounds), 

vessel traffic, and stand-off distance. Therefore, impacts are expected to be nominal for 

recreational fisheries under Alternative B.

4.10.3.1.3 Seismic Restrictions in the EPA

Additional restrictions under Alternative B include prohibiting deep-penetration seismic airgun 

surveys within the portion of the Areas of Concern (Chapter 2.2.2) falling within the EPA. A 

restriction on seismic surveys within a portion of the AOI could result in reduced impacts from active 

acoustic sound sources, vessel traffic, and stand-off distance due to the reduced area of activity. 

The purpose of this mitigation measure is to provide protection to marine mammals within these 

closure areas from the IPFs associated with deep-penetration seismic airgun surveys. This 

mitigation measure would provide an ancillary benefit to some oceanic fish species (refer to 

Appendix E) in the closure area, as the effects on fish hearing and behavior (discussed in detail in 

Chapter 4.4.2.1) will be reduced in that region. Furthermore, this may indirectly benefit recreational 

fisheries because a reduction in the impact to fish hearing and behavior should result in a reduction 

in the impacts to recreational fisheries catch rates. Another benefit would be a reduction in vessel 

traffic and stand-off distance from seismic surveys during the closure period, which will subsequently 

reduce the potential for damage to fishing gears or loss of access of fishing grounds. The impacts of 

active acoustic sound sources, vessel traffic, and stand-off distance from seismic airgun surveys 

would be reduced, but only within the portion of the Areas of Concern falling within the EPA. The 

size of the closure area is small compared with the AOI, and the majority of deep-penetration 

seismic airgun surveys will occur in the WPA and CPA where seismic surveys will not be restricted. 

Thus, there will not be a substantial reduction in seismic survey activity in the AOI, and the overall 

impacts on recreational fisheries would not change under Alternative B. Therefore, impacts are 

expected to be nominal for recreational fisheries under Alternative B. The mitigation measure does 

not apply to sound sources from non-airgun HRG surveys; therefore, the impact from 

electromechanical sources will be nominal for recreational fisheries under Alternative B.
4-344 Description of the Affected Resources and Impact Analysis

4.10.3.1.4 Routine Activities Impact Conclusions

Assessment of each of the mitigation measures included in Alternative B concluded that 

some reduction in impacts may result from the mitigation measures. However, consideration of the 

significance criteria, the AOI as a whole, and the 10-year timeframe results in no change in impact 

level of the overall impacts under Alternative B, which would remain nominal. 

4.10.3.2 Impacts of an Accidental Fuel Spill

Under Alternative B, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. Alternative B would change the timing of certain surveys because of additional coastal 

seasonal restrictions. However, spills from seismic survey vessels could occur in the closure areas 

during times outside the closure period and spills from other survey vessels could occur during the 

closure period. A change in survey timing would not substantially change the risk of a small fuel 

spill. Therefore, the impacts of the IPFs would be very similar to those analyzed for Alternative A in 

Chapter 4.9.2.2. An accidental fuel spill would be expected to result in nominal impacts to 

recreational fisheries under Alternative B.

4.10.3.3 Cumulative Impacts

Impact analyses presented in Chapters 4.10.3.1 and 4.10.3.2 determined that activities 

projected to occur under Alternative B would result in nominal impacts to recreational fisheries, 

depending on the IPF.

Mitigation measures for the proposed action under Alternative B are described in 

Chapter 2.2 and summarized in Chapter 4.10.3.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.10.2.3). Mitigation measures for 

Alternative B are described in Chapter 2.2. Most of the mitigation measures under Alternative B 

would not change the extent, severity, or timing of activities in the proposed action, and therefore 

would not change the resultant impacts to recreational fisheries. Mitigation measures under 

Alternative B that would change the timing and extent of activities in the proposed action include a 

seasonal restriction for operation of airguns in Federal coastal waters, a minimum separation 

distance requirement for simultaneous seismic operations, and the prohibition of deep-penetration 

seismic airgun surveys within portions of the EPA (Chapter 2.2.2).

The proposed action activities considered in the assessment of cumulative impacts are the 

same in Alternatives A and B. Seasonal restriction of airgun operation in Federal coastal waters 

under Alternative B would probably cause a shift in schedules for seismic surveys using airguns but 

not necessarily a reduction in the number and extent of surveys conducted in Federal coastal 

waters. Prohibition of deep-penetration seismic airgun surveys using airguns in the EPA would also 

not appreciably impact the number and extent of such surveys under Alternative B because almost 

all seismic exploration activity to be conducted during the 10-year analysis period will be conducted 

in the WPA and CPA where approximately 99 percent of oil- and gas-related activities take place. 

Because there is little to no change between Alternatives A and B in the proposed action activities 
Gulf of Mexico G&G Activities Programmatic EIS 4-345

considered and because of the limited effect of Alternative B mitigation measures on the occurrence 

and extent of IPFs, recreational fisheries would not be impacted by additional measures in 

Alternative B beyond that described for Alternative A. Therefore, the mitigations under Alternative B 

do not change the cumulative outcomes described in Alternative A (Chapter 4.10.2.3).

4.10.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.10.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative C on recreational fisheries.

4.10.4.1 Impacts of Routine Activities

Additional mitigation measures under Alternative C that would not change the extent, 

severity, or timing of G&G activities, and therefore related impacts to recreational fisheries, include 

the expanded use of PAM for seismic airgun surveys, the expanded use of PSOs for seismic airgun 

surveys and HRG surveys, expansion of NTL 2012-JOINT-G02 (inclusion of manatees) for seismic 

airgun surveys, expansion of NTL 2012-JOINT-G02 to include HRG surveys using airguns, and a 

pre-survey clearance period for HRG surveys. As such, these mitigation measures will not be 

addressed in the following discussion.

4.10.4.1.1 Seasonal Restriction for all Coastal Waters (February 1 to May 31)

Alternative C would require seasonal restrictions for seismic airgun survey operations in 

Federal coastal waters of the GOM shoreward of the 20-m (66-ft) isobath between February 1 and 

May 31 (Figure 2.3-1). The impacts of active acoustic sound sources, vessel traffic, and stand-off 

distance would be reduced, but only within coastal waters between February 1 and May 31. The 

closure area is 9,032,418 ha (22,319,105 ac) and represents 13.1 percent of the area of the AOI 

(68,916,602 ha [170,292,924 ac]). The purpose of this mitigation measure is to provide protection to 

marine mammals within the closure area from the IPFs associated with deep-penetration seismic 

airgun surveys. This mitigation measure would provide an ancillary benefit to some coastal fish 

species (Tables 4.4-1, 4.4-2, and 4.4-4), as the effects on fish hearing and behavior (discussed in 

detail in Chapter 4.4.2.1) will be reduced in the coastal seasonal restriction area. Furthermore, this 

may indirectly benefit recreational fisheries because a reduction in the impact to fish hearing and 

behavior could result in a reduction of the indirect impacts to recreational fisheries catch rates. 

Another benefit would be a reduction in vessel traffic and exclusion zones from seismic surveys

during the closure period, which will subsequently reduce the potential for damage to fishing gear or 

loss of access of fishing grounds. However, seismic surveys will still occur outside this area, the 

closure timeframe is temporary, and the closure area is small compared with the size of the AOI. 

Thus, while a change in survey timing in the coastal seasonal restriction area would slightly reduce 

the impacts of active acoustic sound sources vessel traffic and the stand-off distance from seismic 

airgun surveys on recreational fisheries, it would not change the overall impact level. Therefore, 

impacts are expected to be nominal for recreational fisheries under Alternative C. The mitigation 
4-346 Description of the Affected Resources and Impact Analysis

measure does not apply to sound sources from non-airgun HRG surveys; therefore, the impact from 

electromechanical sources will be nominal for recreational fisheries under Alternative C.

4.10.4.1.2 Routine Activities Impact Conclusions

Assessment of each of the mitigation measures included in Alternative C concludes that 

some reduction in impacts may result from the mitigation measures. However, consideration of the 

significance criteria, the AOI, and the 10-year timeframe results in no change in impact level of the 

overall impacts under Alternative C, and impacts would remain nominal. 

4.10.4.2 Impacts of an Accidental Fuel Spill

Under Alternative C, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. Alternative C would change the timing of certain surveys because of additional coastal 

seasonal restrictions. However, spills from seismic survey vessels could occur in the closure areas 

during times outside the closure period and spills from other survey vessels could occur during the 

closure period. A change in survey timing would not substantially change the risk of a small fuel 

spill. Therefore, the impacts of the IPFs would be very similar to those analyzed for Alternative A in 

Chapter 4.10.2.2. An accidental fuel spill would be expected to result in nominal impacts to 

recreational fisheries under Alternative C.

4.10.4.3 Cumulative Impacts

Impact analyses presented in Chapters 4.10.4.1 and 4.10.4.2 determined that activities 

projected to occur under Alternative C would result in nominal impacts to recreational fisheries.

Mitigation measures for the proposed action under Alternative C are described in 

Chapter 2.3 and summarized in Chapter 4.10.4.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.10.2.3). Most mitigation measures 

under Alternative C would not change the extent, severity, or timing of activities in the proposed 

action, and therefore would not change the resultant impacts to recreational fishing. Under 

Alternative C, the mitigation measure that would change the timing and extent of activities in the 

proposed action is a seasonal restriction from February 1 through May 31 for operation of airguns in 

all coastal waters shoreward of the 20-m (66-ft) isobath within the AOI. Therefore, the mitigations 

under Alternative C do not change the cumulative outcomes described in Alternative A (Chapter

4.10.2.3).

4.10.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative D are the same as for 

Alternative A (Chapter 4.10.2). The additional mitigation measure under Alternative D would not 

reduce potential active acoustic impacts discussed in Alternatives A and C (Chapters 4.10.2.1 and 

4.10.4.1), and impacts would remain nominal. The mitigation would not alter the impact levels to 

recreational fisheries from vessel traffic or stand-off distance and would remain nominal. Under 
Gulf of Mexico G&G Activities Programmatic EIS 4-347

Alternative D, impacts of an accidental fuel spill on recreational fisheries would be as described for 

Alternatives A and C (Chapters 4.10.2.2 and 4.10.4.2) and would remain nominal. 

4.10.5.1 Impacts of Routine Activities

The additional mitigation measure under Alternative D, i.e., the exclusion of bow-riding 

dolphins from shutdown protocols, would not change the extent, severity, or timing of the IPFs 

outlined in Alternatives A and C. Therefore, impacts would be nominal for recreational fisheries 

under Alternative D.

4.10.5.2 Impacts of an Accidental Fuel Spill

Alternative D would not add mitigation measures that would reduce the risk of an accidental 

fuel spill. Therefore, the impacts of the IPFs would be very similar to those analyzed for 

Alternatives A and C in Chapters 4.10.2.2 and 4.10.4.2. Impacts to recreational fisheries resources 

from an accidental fuel spill or small diesel spill would be nominal under Alternative D.

4.10.5.3 Cumulative Impacts

Impact analyses presented in Chapters 4.10.5.1 and 4.10.5.2 determined that activities 

projected to occur under Alternative D would result in nominal impacts to recreational fisheries, 

depending on the IPF.

Mitigation measures for the proposed action under Alternative D are described in 

Chapter 2.4 and summarized in Chapter 4.10.5.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.10.2.3). The mitigation measures are 

the same as described for Alternative C with the addition of shutdown protocols during seismic 

operations for all marine mammals (except bow-riding dolphins). The addition of shutdown protocols 

for all marine mammals except bow-riding dolphins under Alternative D would not change the extent, 

severity, or timing of activities in the proposed action; thus, the resultant impacts to recreational 

fisheries also would not change. Therefore, the mitigation measures under Alternative D do not 

change the cumulative outcomes described in Alternative A (Chapter 4.10.2.3).

4.10.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.10.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative E on recreational fisheries.

4.10.6.1 Impacts of Routine Activities

The reduction of deep-penetration, multi-client activities by 10 percent or 25 percent would 

reduce the extent, severity, and timing of active acoustic sound sources, vessel traffic, and stand-off 

distance compared with Alternative A. The analysis in Alternative A concluded that impacts from 
4-348 Description of the Affected Resources and Impact Analysis

these IPFs would be nominal. The reduction in activity would not change the overall impacts for 

these IPFs and would therefore be nominal for recreational fisheries under Alternatives E1 and E2.

4.10.6.1.1 Reduction of G&G Activity Levels

As discussed in Chapter 4.10.2.1, impacts of active acoustic sound sources are expected to 

be nominal for recreational fisheries under Alternative A. Under Alternatives E1 and E2, there 

would be a 10 percent or 25 percent reduction in activities, respectively, for deep-penetration, multiclient activities. A reduction in activities under Alternatives E1 and E2 could reduce the impacts of 

acoustic sound sources from certain seismic airgun surveys on recreational fisheries. However, 

seismic airgun surveys will still be conducted throughout the AOI, and recreational fish resources will 

still be impacted by airguns and electromechanical sounds sources. Localized short-term 

interruptions of recreational fishing activities may be expected, and slight decreases in recreational 

fisheries landings may still occur. Therefore, a reduction in deep-penetration, multi-client activities 

will not change the overall level under Alternatives E1 and E2. The impacts of active acoustic 

sounds from seismic airguns and electromechanical sources will be nominal for recreational 

fisheries under Alternatives E1 and E2.

Under Alternatives E1 and E2, the majority of the activities will continue without restrictions; 

impacts to recreational fisheries are likely to be localized at several locations, intermittent in 

frequency of occurrence, temporary, and short term in nature. Therefore, impacts to recreational 

fisheries landings arising from vessel traffic and stand-off distance are expected to remain nominal

under Alternatives E1 and E2.

4.10.6.2 Impacts of an Accidental Fuel Spill

Under Alternatives E1 and E2, impacts of accidental fuel spills on recreational fisheries 

would be very similar to those analyzed for Alternative C in Chapter 4.10.4.2. Alternatives E1 and 

E2 would reduce the number of surveys and vessels by 10 percent or 25 percent, respectively, but 

this reduction would not substantially change the risk of a small fuel spill because the majority of 

activities will continue to take place. A small diesel spill is expected to disperse and weather rapidly, 

with evaporation of volatile components. The impacts would depend on the size and location of the 

spill, as well as the meteorological conditions. Impacts to recreational fisheries resources from an 

accidental fuel spill or small diesel fuel spill would remain nominal under Alternatives E1 and E2.

4.10.6.3 Cumulative Impacts

Impact analyses presented in Chapters 4.10.6.1 and 4.10.6.2 determined that activities 

projected to occur under Alternative E would result in nominal impacts to recreational fisheries, 

depending on the IPF.

Mitigation measures for the proposed action under Alternative E are described in 

Chapter 2.5 and summarized in Chapter 4.10.6.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.10.2.3). The reduction of deep-
Gulf of Mexico G&G Activities Programmatic EIS 4-349

penetration, multi-client activities (in line miles) by 10 percent (Alternative E1) or 25 percent 

(Alternative E2) would reduce the extent, severity, and timing of active acoustic sound sources, 

vessel traffic, and stand-off distance; therefore, impacts for these IPFs would be incrementally 

decreased under Alternative E. Reductions in the line miles of deep-penetration, multi-client seismic 

airgun surveys would result in a net reduction of sound in the AOI. However, the changes under 

Alternative E do not change the impact level to the cumulative outcomes described in Alternative A 

(Chapter 4.10.2.3).

4.10.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.10.2). The following discussion outlines the effects of the additional 

mitigation measures included in Alternative F on recreational fisheries.

4.10.7.1 Impacts of Routine Activities

4.10.7.1.1 Area Closures

Alternative F would require area closures in the CPA Closure Area, EPA Closure Area, Dry 

Tortugas Closure Area, and Flower Gardens Closure Area (Figure 2.6-1). The closures would 

reduce the impacts of active acoustic sound sources, vessel traffic, and stand-off distance on 

recreational fisheries occurring within or near the closure areas. The analysis in Alternative A 

concluded that impacts from active acoustic sound sources, vessel traffic, and stand-off distance 

would be nominal. A reduction in activities under Alternative F would not change the overall impact 

level. Therefore, impacts of all active acoustic sound sources (e.g., airgun and electromechanical) 

are expected to be nominal for recreational fishes and fishing activity under Alternative F. Impacts 

of vessel traffic and stand-off distance are expected to be nominal for recreational fisheries under 

Alternative F.

4.10.7.1.2 Routine Activities Impact Conclusions

Assessment of each of the mitigation measures included in Alternative F conclude that some 

reduction in impacts may result from the mitigation measures. However, consideration of the 

significance criteria, the AOI, and the 10-year timeframe results in no change in impact level of the 

overall impacts under Alternative F, and impacts would remain nominal. 

4.10.7.2 Impacts of an Accidental Fuel Spill

A reduction in the geographical area covered by G&G activities would reduce the overall 

impact of accidental fuel spills or small diesel fuel spills under Alternative F compared with

Alternative A. The analysis in Alternative A concluded that impacts from accidental fuel spills or 

small diesel fuel spills would be nominal. A reduction in activities under Alternative F would not 

change the overall impact level. Therefore, impacts to recreational fisheries resources from an 

accidental fuel spill or small diesel fuel spill would remain nominal. 
4-350 Description of the Affected Resources and Impact Analysis

4.10.7.3 Cumulative Impacts

Impact analyses presented in Chapters 4.10.7.1 and 4.10.7.2 determined that activities 

projected to occur under Alternative F would result in nominal impacts to recreational fisheries.

Mitigation measures for the proposed action under Alternative F are described in 

Chapter 2.6 and summarized in Chapter 4.10.7.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.10.2.3). Mitigation measures under 

Alternative F are similar to Alternative C with the addition of area closures in four areas: the CPA 

Closure Area; the EPA Closure Area; the Dry Tortugas Closure Area; and the Flower Gardens 

Closure Area. Most mitigation measures under Alternative F would not change the extent, severity, 

or timing of activities in the proposed action; thus, the resultant impacts to recreational fisheries also 

would not change the nominal cumulative outcomes described in Alternative A (Chapter 4.10.2.3).

4.10.8 Impacts – Alternative G (No New Activity Alternative)

The IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.10.2).

4.10.8.1 Impacts of Routine Activities

Under Alternative G, no new permits/authorizations will be issued for G&G activities. 

Previously authorized activities would still occur under existing agreements or permits/authorizations 

but would drop off quickly. The VSP (2D only) and SWD surveys would continue at the level of 

activity in Table 2.7-1. The VSP surveys cover fewer line miles and shorter distances, use less 

sound energy, and most are completed in a few days (Appendix F, Section 1.1.5). Thus, impacts 

from active acoustic sound sources, vessel traffic, and stand-off distances would not change 

immediately but would decrease over time. Impacts from other routine activities would also 

decrease over time. Therefore, impacts from routine activities on recreational fisheries would remain 

similar to Alternatives A and C over time (nominal). A substantial reduction in non-VSP activities 

would likely reduce impacts from all routine activities on recreational fisheries, and impacts would be 

no impact to nominal. 

4.10.8.2 Impacts of Accidental Fuel Spills

Under Alternative G, a change in the spill volume for diesel fuel (1.2 to 7.1 bbl) is not 

expected. No new permits/authorizations will be issued for G&G activities. Previously authorized 

activities would still occur under existing agreements or permits/authorizations but would drop off 

quickly. Subsequently, VSP surveys will continue to be permitted. Thus, impacts of accidental fuel 

spills on recreational fisheries would be very similar to those analyzed for Alternatives A and C in 

Chapters 4.10.2.2 and 4.10.4.2. Impacts to recreational fisheries from an accidental fuel spill or 

small diesel fuel spill would be nominal, eventually declining to no impact. 
Gulf of Mexico G&G Activities Programmatic EIS 4-351

4.10.8.3 Cumulative Impacts

Impact analyses presented in Chapters 4.10.8.1 and 4.10.8.2 determined that activities 

projected to occur under Alternative G would result in nominal impacts to recreational fisheries.

Mitigation measures under Alternative G are described in Chapter 2.7. A detailed impacts 

assessment under the cumulative scenario is provided in Alternative A (Chapter 4.10.2.3). The 

cease of activity for future G&G surveys requiring a permit/authorization from BOEM would 

substantially decrease the cumulative impacts from all IPFs. However, VSP and SWD surveys are 

expected to continue under Alternative G. Therefore, following cessation of the majority of activities, 

there would be a nominal incremental increase in impacts to recreational fisheries from active 

acoustic sound sources, vessel traffic, stand-off distances, and accidental fuel spills under 

Alternative G.

4.11 ARCHAEOLOGICAL RESOURCES

4.11.1 Description of the Affected Environment

The following paragraphs are a summary of the material presented in Appendix E, 

Section 11 and serve to support the impact analysis presented below. The AOI holds the potential 

to contain unknown historic shipwrecks and prehistoric sites. Shipwrecks within the AOI date from 

the 16th century until modern times. A variety of shipwreck databases and secondary sources were 

reviewed under this Programmatic EIS to estimate the number of shipwrecks, obstructions, and 

archaeological sites that may be located within the AOI. The results of that review indicated that 

there could be >12,000 shipwrecks and/or historic resources within in the GOM. Due to the potential 

for unknown shipwreck resources on the Gulf of Mexico OCS, the NPS and MMS (BOEM’s 

predecessor) sponsored three studies starting in 1977 to identify areas in the GOM where 

shipwrecks may occur (CEI, 1977, Garrison et al., 1989; Pearson et al., 2003). These studies 

examined a variety of factors that could influence the location of a shipwreck, including, but not 

limited to, historic shipping routes, natural marine hazards, and atmospheric and ocean conditions. 

Researchers identified OCS lease blocks having high probabilities for containing shipwreck 

resources. New shipwreck discoveries during recent HRG surveys have demonstrated that 

deepwater regions also hold a high potential for containing well-preserved shipwreck remains. In 

response, BOEM has further revised their guidelines effectively, requiring archaeological surveys in 

all OCS lease blocks prior to any bottom-disturbing impacts.

Research has also shown the possibility of prehistoric resources in the AOI. Archaeological 

evidence indicates that the GOM region was first occupied approximately 11,700 B.P. Conditions 

necessary for preservation of intact Paleo-Indian sites along the Gulf of Mexico OCS are variable 

and depend on geomorphological conditions and the speed of sea-level rise. Current research on 

regional geology, relative sea-level changes, and marine transgression (geological event leading to 

sea level rise) are providing useful data concerning the possibility that there may be intact PaleoIndian sites submerged along the OCS. These submerged sites would most likely be found in the 

vicinity of paleochannels (remnant of an old river) or river terraces that offer the highest potential of 
4-352 Description of the Affected Resources and Impact Analysis

site discovery. The possibility of locating submerged prehistoric sites would be greatest in the 

nearshore zone (<60-m [197-ft] water depth) because portions of this area would have been 

exposed land during the period of human occupation.

4.11.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

As shown in Table 4.1-2, the IPFs that may impact archeological resources within the AOI 

include (1) seafloor disturbance, (2) drilling discharges, (3) entanglement with bottom-founded 

cables, and (4) accidental fuel spills.

In considering the potential impacts to the associated archeological resources, it is important 

to make the distinction between the AOI and the EPA, CPA, and WPA. The AOI covers 

689,166 km2 (266,089 mi2

), including 45,630 km2 (17,618 mi2) of State waters outside of the 

planning area boundaries, so the total planning areas in Federal waters considered for archeological 

resources is 643,536 km2 (248,471 mi2

). The potential direct impacts considered here include the 

planning areas only and does not include State waters that extend to 3 nmi (3.5 mi; 5.6 km) offshore 

Louisiana, Mississippi, and Alabama, and 9 nmi (10.4 mi; 16.7 km) offshore Texas and Florida, 

which are beyond OCS lease block area boundaries and where proposed BOEM-authorized G&G 

activities would not occur. This distinction is important because the EPA does not include the 

Florida Keys, Dry Tortugas National Park, the Tortugas Ecological Reserve, and other sensitive 

shallow-water habitats within State waters 3 or 9 nmi from shore. In these areas outside of the 

planning areas but within the AOI, for archaeological resources, only potential indirect impacts 

propagating into the area from proposed activities are considered.

The analysis for Alternative A is organized by IPF and takes into account the potential effects 

of associated mitigation measures to influence the impact level. In contrast, the analysis of impacts 

associated with Alternatives B through G are organized by alternative-specific mitigation measures 

and how each these measures may reduce impact levels.

Impact Levels and Impact Significance Criteria

The National Historic Preservation Act (NHPA) (54 U.S.C. §§ 300101 et seq.) established a 

national program to preserve the country’s historical and cultural resources. Section 106 of the

NHPA requires Federal agencies to consider the effects of their actions on historic properties and to 

provide the President’s Advisory Council on Historic Preservation an opportunity to comment on a 

proposed action before it is implemented. Regulations for implementing the Section 106 process are 

provided in 36 CFR part 800. State and Federal guidelines for cultural resources recognize that 

buildings, structures, objects, districts, archaeological sites, and cultural landscapes can be 

historically significant. Under Section 106 of the NHPA (36 CFR § 800.16), a historic property is 

“any prehistoric or historic district, site, building, structure, or object included in, or eligible for 

inclusion in, the National Register of Historic Places.” Districts include the property types known as 

cultural landscapes (e.g., historic, rural, designed, etc.). To be eligible for the National Register of 

Historic Places (NRHP), these property types must be >50 years old and/or meet at least one of the 

NRHP significance evaluation criteria (36 CFR § 60.4), and the property must possess integrity. 
Gulf of Mexico G&G Activities Programmatic EIS 4-353

Specific aspects or types of integrity include location, design, setting, materials, workmanship, 

feeling, and association. The NRHP properties meet one or more of the following evaluation criteria:

• Criterion A – the property is associated with events that have made a significant 

contribution to the broad patterns of our history;

• Criterion B – the property is associated with the lives of persons significant in our 

past;

• Criterion C – the property embodies the distinctive characteristics of a type, 

period, or method of construction; represents the work of a master; possesses 

high artistic values; or represents a significant and distinguishable entity whose 

components may lack individual distinction; or

• Criterion D – the property has yielded, or may be likely to yield, information 

important to prehistory or history.

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. In consideration of 

the NRHP criteria and the sensitivity of submerged cultural resources to disturbance, the following 

significance criteria are used to evaluate the level of impact for each IPF.

Nominal impacts to archaeological resources would be the lowest level of detection that 

would have neither adverse nor beneficial impacts. Nominal impacts would include any effects upon 

suspected archaeological resources, such as an untested magnetic anomaly, on the seafloor that 

later are determined to be modern debris.

Minor impacts to archaeological resources would be disturbance of archaeological 

resources resulting in little, if any, loss of site integrity.

Moderate impacts to archaeological resources would be site disturbance resulting in a loss 

of integrity and a partial loss of the character defining features and information potential that form the 

basis of the site’s NRHP eligibility. Mitigation is accomplished by a combination of archeological 

data recovery and in-place preservation.

Major impacts to archaeological resources would be disturbances resulting in a loss of site 

integrity to the extent that the resource is no longer eligible for listing in the NRHP. The site’s 

character-defining features and information potential are lost to the extent that archeological data 

recovery is the primary form of mitigation.
4-354 Description of the Affected Resources and Impact Analysis

In addition to the above impact criteria, not only were negative impacts considered but also 

considered were the beneficial impacts and duration. Beneficial impacts can occur when an 

archaeological site is stabilized in its current condition to maintain its existing level of integrity or 

when an archaeological site is preserved in accordance with Secretary of the Interior’s Standards for 

the Treatment of Historic Properties. Short-term impacts last for the duration of construction-related 

activities while long-term impacts last beyond the proposed construction activities and are 

permanent. All impacts to archaeological sites are considered long-term impacts.

4.11.2.1 Impacts of Routine Activities

4.11.2.1.1 Seafloor Disturbance and Entanglement

Placement of equipment (e.g., anchors, cables, nodes, receivers, and bottom-founded 

monitoring buoys) on the seafloor has the potential to damage any significant archaeological 

resources present. Proposed activities under Alternative A include bottom sampling in all three 

program areas, including a maximum of 896 bottom samples in the oil and gas program (Table

3.2-3); 270 core samples, 270 grab samples, and 270 CPT samples in the renewable energy 

program (Table 3.2-4); and 90 grab samples, 50 jet probes, and 392 vibracores in the marine 

minerals program (Table 3.2-5). The total of all bottom samplings from coring, grab samples, CPTs, 

and jet probes is 2,238 samplings in all three program areas. A total of 150,381 m2 (1,618,688 ft2

) 

(Table 3.2-8) of seafloor would be disturbed under the proposed activities scenario.

Certain surveys in oil and gas exploration require placement of anchors, nodes, cables, 

sensors, or other equipment on or in the seafloor (Chapter 3.3.1.8.2). Locations and projected 

levels are not estimated; however, nodal surveys are relatively uncommon and are typically used in 

shallow waters. Appendix F, Section 1.1.3 provides complete descriptions of nodal surveys.

Drill test wells that are associated with oil and gas exploration activities are expected to 

impact the seafloor over an area ≥2 ha (5 ac) per well, primarily through the physical coring of the 

sediment. Secondarily, deposition of drill muds and cuttings may bury artifacts, making their future 

detection more difficult. Only two test wells are planned under the time period of this Programmatic 

EIS. The VSP surveys associated with oil and gas exploration also are expected to impact the 

seafloor through the placement of receivers in well boreholes. It is projected that 561 VSP surveys 

are planned over the 10-year period of this Programmatic EIS (Table 3.2-8).

The depth distribution of submerged cultural resources is an important consideration when 

evaluating the potential impact. While historic shipwrecks may occur at any water depth within the 

AOI, prehistoric resources are depth-limited, as outlined in Chapter 4.11.1. The highest probabilities 

for encountering submerged prehistoric sites vary within the AOI, primarily by depth, location, and 

local sedimentation rate. In general, areas deeper than 60 m (197 ft) can be expected to have no 

sensitivity for the presence of or potential for impact to prehistoric resources. It is most likely that 

submerged prehistoric resources would be found in the vicinity of paleochannels or similar 

geomorphic features that possess a higher potential for preservation relative to other areas.
Gulf of Mexico G&G Activities Programmatic EIS 4-355

Because of the rich maritime history and potential for submerged prehistoric resources in the 

AOI, all activities that disturb the seafloor could impact previously unrecorded cultural resources. 

The potential impacts of survey operations are generally localized but occur over a widely dispersed 

area and may be caused by coring, bottom sampling, OBC and OBN surveys, vertical cable surveys, 

and anchor deployments associated with seafloor-disturbing activities. The placement of heavy 

objects (i.e., anchors and tethered nodes with sound dampeners), in conjunction with OBC and OBN 

surveys on the seafloor, have the potential to severely impact an archaeological site should they 

come into direct contact with a resource. The OBCs are deployed from a surface vessel onto the 

seafloor. While the cable itself is light and flexible, the acoustic node assembly and sound 

dampeners can weigh up to approximately 400 lb (181 kg). The “blind” method of laying down and 

peeling up the cable from the seafloor could cause the cable to snag on a shipwreck, causing 

moderate to major impacts. The OBNs are either dropped from a surface vessel, with a localized 

impact over a large area, or placed by ROVs, thereby lessening potential impacts to any 

archaeological resources that may be present on the seafloor. The potential for impacts to 

archaeological resources resulting from G&G surveys could be reduced further through predisturbance survey plan reviews provided by BOEM.

Except in the case of OBC and OBN surveys, BOEM considers G&G surveys to have a 

nominal impact to the seafloor. If site-specific information regarding potential archaeological 

resources is provided to BOEM prior to approving G&G activities involving the seafloor, these

activities would likely result in nominal impacts to archaeological resources. In the absence of a 

site-specific archaeological survey or ROVs are not utilized during deployment of nodes, BOEM 

does not have the ability to determine if an archaeological resource may have been impacted by 

OBC or OBN surveys. If impacts were to occur they would be moderate to major depending on the 

extent of the impact. In an attempt to mitigate potential damages to archaeological resources, 

BOEM also requires that, if a cable becomes snagged upon retrieval operations, the operator must 

verify the cause of the snag, which could possibly minimize further damage to archaeological 

resources. Additionally, if, during the course of G&G activities, it is determined that a potential 

shipwreck or prehistoric site has been located, the operator would immediately halt operations and 

take the necessary steps to ensure that the site is not disturbed further. BOEM must be notified 

within 48 hours of the discovery.

For the renewable energy program, BOEM has issued “Guidelines for Providing 

Archaeological and Historic Property Information Pursuant” to 30 CFR part 585. The July 2015 

revised guidelines specify that a site characterization survey must reliably cover any portion of the 

site that would be affected by seafloor-disturbing activities. The guidelines recommend avoidance 

as a primary mitigation strategy for objects of historical or archaeological significance.

4.11.2.1.2 Drilling Discharges

It is unlikely that archaeological resources would be affected by drilling discharges in the AOI 

during the time period of this Programmatic EIS. The oil and gas scenario for the planning areas 

predicts that only two drilled test wells would occur during the 10-year period of this Programmatic 
4-356 Description of the Affected Resources and Impact Analysis

EIS. Anticipated impacts to archaeological resources from drilling include discharge of drilling fluids, 

cuttings, and localized accumulation of cement slurry. Based on the limited impacts of these 

activities to benthic communities as discussed in Chapter 4.5.2.1, it is likely that the impact to 

archaeological resources would be nominal also. Avoidance of archaeological resources and the 

immediate reporting of unanticipated discoveries to BOEM are expected to prevent a serious impact 

to archaeological resources. Given BOEM’s requirement for site-specific information regarding 

archaeological resources for all drilling activities, impacts from drilling discharges in the AOI are 

expected to be nominal. 

4.11.2.1.3 Routine Activities Impact Conclusions

This analysis considered the significance criteria, the AOI, and the 10-year timeframe. 

Mitigation measures that are associated with Alternative A are outlined in Chapter 2.1 and detailed 

in Appendix B. Except in the case of OBC and OBN surveys, BOEM considers seafloor 

disturbance related to G&G surveys and drilling discharges to have a nominal impact to the 

seafloor. If site-specific information regarding potential archaeological resources is provided to 

BOEM prior to approving G&G activities involving the seafloor, seafloor disturbance activities and 

the potential for entanglement would likely result in nominal impacts to archaeological resources. 

Archaeological review is not required in advance of OBN and OBC surveys; however, identified and 

potential archaeological resources are noted for avoidance. The deployment of OBCs and OBNs 

dropped from the surface and entanglement during recovery have the potential to have moderate to 

major impacts to unidentified archaeological resources. The OBNs placed by an ROV will have a 

nominal impact to archaeological resources, as the seafloor is visually inspected before placement 

and recovery. Additionally, the requirement to visually verify any snags resulting from entanglement 

during recovery would also help to mitigate further potential damages to archaeological resources. 

In summary, the impacts to archaeological from each project-related IPF (including routine activities) 

is expected to range from nominal to major. 

4.11.2.2 Impacts of an Accidental Fuel Spill

An accidental event could result in the release of fuel by a survey vessel. Based on USCG 

spill statistics, a spill scenario developed under a previous study assumed a diesel spill volume of 

1.2 to 7.1 bbl (USDOI, BOEM, 2014b). Fuel spills occurring at the ocean surface would disperse 

and weather. Volatile components of the fuel would evaporate. Diesel and other fuel used for the 

operation of survey vessels is light and would float on the water surface. A small proportion of the 

heavier fuel components could adhere to particulate matter in the upper portion of the water column 

and sink. Particulate matter contaminated with diesel fuel eventually would reach the seafloor, 

within or outside the AOI, depending on spill location, water depth, ambient currents, and sinking 

rate. However, given the relatively small size of the fuel spill and the loss of most spilled fuel 

through evaporation and dispersion, a small diesel fuel spill at the surface would have no effect on 

the seafloor and would not require seafloor cleanup activity. An accidental diesel fuel spill would be 

expected to result in nominal impacts to archaeological resources.
Gulf of Mexico G&G Activities Programmatic EIS 4-357

High-volume catastrophic fuel spills such as the Deepwater Horizon explosion, oil spill, and 

response are rare, and the average size of a typical fuel spill is fairly small. Currently, there is very 

little information available on the impacts of a high-volume fuel spill on archaeological resources. 

However, as with the release of fuels, the impact of a low-volume spill to archaeological resources 

should be nominal. Oil released during a fuel spill should rise to the surface quickly and be 

volatilized or dispersed by ocean currents.

4.11.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 

in the cumulative scenario. The IPFs identified for archaeological resources are compared with the 

IPFs from each of the cumulative scenario components in order to focus this cumulative analysis on 

those activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The 

G&G activity IPFs associated with the proposed action included in the cumulative assessment are 

the same as those assessed under routine activities and accidental events. The following analysis 

evaluates the incremental increase by IPF from the proposed action and provides a conclusion of 

the cumulative incremental increase within the AOI.

The G&G activities have been ongoing in the GOM for at least the past 30 years, and it is 

reasonable to assume they will continue into the future; however, for the purpose of this 

Programmatic EIS, the cumulative analysis assesses a 10-year timeframe to coincide with the 

proposed action because it is not expected that G&G activities will have lasting effects or extend 

beyond the 10-year timeframe of this Programmatic EIS.

The IPFs that have been applied to the components of the cumulative activity scenario are 

provided in Table 3.4-1. The IPFs for these cumulative activities that could affect archaeological 

resources are (1) seafloor disturbance, (2) drilling discharges, (3) entanglements from bottomfounded cables; and (4) accidental fuel spills. Impact analyses presented in Chapters 4.11.2.1 and 

4.11.2.2 determined that activities projected to occur under Alternative A could result in nominal to 

major impacts to archaeological resources.

4.11.2.3.1 Seafloor Disturbance and Entanglement

Seafloor-disturbing activities under the OCS Program activities in the cumulative scenario 

over the next 10 years will include the construction and installation of a maximum of 

8,233 exploration and production wells; installation of a maximum of 507 production structures (e.g., 

caissons and multi-leg platforms); and a maximum of 17,437 km (10,835 mi) of pipelines (Table

3.4-2). Proposed action activities can disturb the seafloor by the placement of equipment, trenching, 

coring, and bottom sampling. These activities could damage archaeological resources, if present. 

Depending on size, production structures can impact the seafloor from as little as hundreds of 

square feet to up to tens of thousands of square feet. There are a limited number of renewable 

energy activities projected over the next 10 years. Seafloor disturbances from these activities would 
4-358 Description of the Affected Resources and Impact Analysis

be localized and evaluated to minimize disturbances to nearby archaeological resources. Seafloor 

disturbances associated with marine mineral use would be in pre-determined OCS sand source 

areas (Chapters 3.2.3 and 3.4.1.4) for use in coastal restoration. As restoration activities would be 

limited to “beach” quality sand sediments, seafloor disturbances would be localized.

Seafloor-disturbing activities associated with the proposed alternative activities over the 

10-year period would include a maximum of 3 wells, 2 bottom-founded monitoring buoys, and 

2,238 bottom samplings (Table 3.2-8). One renewable energy development is being considered 

under the proposed action scenario. For the activities under its purview, BOEM has existing 

regulations, guidelines, best management practices, and permit authorizations containing COAs 

regarding submerged cultural resources and their preservation. Because the location of most nonrenewable submerged cultural resources are unknown and because of the high potential for 

information loss and damage, cumulative impacts to submerged archaeological resources could be 

significant. However, all activities under BOEM’s purview that could disturb the seafloor may be 

subject to guidance for submitting site characterization surveys, which include the identification of 

potentially impacted cultural resources. Locations identified as having potential historic shipwreck or 

prehistoric archaeological resources will be assigned an avoidance buffer for all activities. If, during 

the course of G&G activity, it is determined that a potential shipwreck or prehistoric site has been 

located, the operator must immediately halt operations and take the necessary steps to ensure that 

the site is not disturbed further. BOEM must be notified within 48 hours of the discovery. If all 

existing protective measures and regulations are followed and potential archaeological resources 

are identified in advance, then a nominal incremental increase in impacts from seafloor disturbance 

activities to archaeological resources under the OCS Program is expected. If an impact related to 

seafloor disturbance activities or entanglements during recovery of OBCs and OBNs were to occur, 

the impact would be moderate to major depending on the nature and extent of the impact.

4.11.2.3.2 Drilling Discharges

Cumulative scenario activities that would include discharges of drilling fluids, drill cuttings, 

and other effluents from drilling rigs would require BOEM’s authorization as well as the submittal and 

agency review of site-specific information regarding archaeological resources prior to activity 

approval. BOEM’s review is expected to help ensure that physical impacts to sensitive 

archaeological resources are avoided and that the resources are protected from impacts from 

cumulative scenario activities.

Drilling discharge activities from the proposed action were determined to result in a nominal

impact to archaeological resources (Chapter 4.11.2.1). Considering the limited contribution of 

drilling discharges under the proposed action compared with existing drilling activities under the 

OCS program and State waters oil and gas activities, a nominal incremental increase to impacts 

from the proposed action is expected.
Gulf of Mexico G&G Activities Programmatic EIS 4-359

4.11.2.3.3 Accidental Fuel Spills

A significant amount of vessel traffic is expected to occur under the cumulative scenario, 

including high levels of vessel activity associated with servicing offshore oil and gas production 

facilities (Table 3.4-2), the commercial shipping and marine transportation system, and vessel traffic 

from other components included in the cumulative scenario (Tables 3.4-7 and 3.4-8). All vessel 

movements are associated with a risk of collision and subsequent loss of fuel. However, with the 

use of AIS on large sea-going vessels, radar, and licensing of vessel captains, the potential of a 

vessel collision occurring is low, and the potential for a resultant spill is even lower. The impact of a 

spill on archaeological resources was expected to be nominal (Chapter 4.11.2.2). Though the 

magnitude of vessel activity in the AOI is expected to be higher, the potential for an accidental fuel 

spill from vessel collisions would still be considered low. The impacts associated with the proposed 

action would result in a nominal incremental increase in impacts to archaeological resources.

4.11.2.3.4 Cumulative Impact Conclusions

Impact analyses presented in Chapters 4.11.2.1 and 4.11.2.2 determined that activities 

projected to occur under Alternative A would result in nominal to major (if no mitigation is imposed) 

impacts to archaeological resources.

For the activities under their purview, BOEM has existing regulations (NTLs), guidelines, best 

management practices, and permit authorizations containing COAs regarding submerged cultural 

resources and their preservation. Therefore, overall, the potential cumulative impacts to 

archaeological resources would result in a nominal incremental increase in impacts from seafloor 

disturbance and drilling discharges.

4.11.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs, impact significance criteria, and impact conclusions for Alternative B are the same 

as for Alternative A (Chapter 4.11.2).

4.11.3.1 Impacts of Routine Activities

The additional mitigation measures implemented under Alternative B would not change the 

extent, severity, or timing of G&G activities related to impacts to archeological resources. As 

discussed under Alternative A in Chapter 4.11.2, there are two applicable routine IPFs for 

archaeological resources: seafloor disturbance and drilling discharges. The mitigation measures 

under Alternative B would not change the extent, severity, or timing of seafloor disturbance or drilling 

discharges. Except in the case of OBC and OBN surveys, BOEM considers seafloor disturbance 

related to G&G surveys and drilling discharges to have a nominal impact to the seafloor. If sitespecific information regarding potential archaeological resources is provided to BOEM prior to 

approving G&G activities involving the seafloor, seafloor-disturbing activities and the potential for 

entanglement would likely result in nominal impacts to archaeological resources. Archaeological 

review is not required in advance of OBN and OBC surveys; however, identified and potential 

archaeological resources are noted for avoidance. The deployment of OBCs and OBNs dropped
4-360 Description of the Affected Resources and Impact Analysis

from the surface and entanglement during recovery have the potential moderate to major impacts 

to unidentified archaeological resources. The OBNs placed by an ROV will have a nominal impact 

to archaeological resources, as the seafloor is visually inspected before placement and recovery. 

Additionally, the requirement to visually verify any snags resulting from entanglement during 

recovery would also help to mitigate further potential damages to archaeological resources. In 

summary, the impacts to archaeological from each project-related IPF (including routine activities) is 

expected to range from nominal to major (if no mitigation is imposed).

4.11.3.2 Impacts of an Accidental Fuel Spill

Under Alternative B, impacts of an accidental fuel spill on archaeological resources would be 

very similar to those analyzed for Alternative A in Chapter 4.11.2.2. Because there is the potential 

for a small proportion of the heavier fuel components to adhere to particulate matter in the upper 

portion of the water column and sink, particulate matter contaminated with diesel fuel could 

eventually reach the seafloor; an accidental diesel fuel spill would be expected to result in nominal

impacts to archaeological resources.

4.11.3.3 Cumulative Impacts

Impact analyses presented in Chapters 4.11.3.1 and 4.11.3.2 determined that activities 

projected to occur under Alternative B would result in nominal to major (if no mitigation is imposed) 

impacts to archaeological resources.

Mitigation measures for the proposed action under Alternative B are described in 

Chapter 2.2 and summarized in Chapter 4.11.3.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.11.2.3). The mitigation measures under 

Alternative B would not change the extent, severity, or timing of activities in the proposed action; 

thus, the resultant impacts to archaeological resources also would not change because none of the 

mitigation measures would change the seafloor-disturbing activities or drilling discharges. 

Alternative B would change the timing of certain surveys because of seasonal restrictions and 

required limits on some types of seismic airgun surveys. However, as discussed in 

Chapter 4.11.2.3, a significant amount of vessel traffic is expected to occur under the cumulative 

scenario. All vessel movements are associated with a risk of collision and subsequent loss of fuel. 

The risk of accidental fuel spills arising from a vessel collision under the cumulative scenario is 

expected to be nominal. The changes to seismic airgun survey protocols would not substantially 

change the risk of a small fuel spill. Overall, the risk of a small fuel spill and the potential cumulative 

impacts to archaeological resources would be the same under Alternative B as determined under 

Alternative A and would result in a nominal incremental increase in impacts from seafloor 

disturbance and drilling discharges and in the risk of a collision-based fuel spill.
Gulf of Mexico G&G Activities Programmatic EIS 4-361

4.11.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs, impact significance criteria, and impact conclusions for Alternative C are the same 

as for Alternative A (Chapter 4.11.2).

4.11.4.1 Impacts of Routine Activities

The additional mitigation measures implemented under Alternative C would not change the 

extent, severity, or timing of G&G activities related to impacts to archeological resources. As 

discussed under Alternative A in Chapter 4.11.2, there are two applicable routine IPFs for 

archaeological resources: seafloor disturbance and drilling discharges. The mitigation measures 

under Alternative C would not change the extent, severity, or timing of seafloor disturbance or drilling 

discharges. Except in the case of OBC and OBN surveys, BOEM considers seafloor disturbance 

related to G&G surveys and drilling discharges to have a nominal impact to the seafloor. If sitespecific information regarding potential archaeological resources is provided to BOEM prior to 

approving G&G activities involving the seafloor, seafloor-disturbing activities and the potential for 

entanglement would likely result in nominal impacts to archaeological resources. Archaeological 

review is not required in advance of OBN and OBC surveys; however, identified and potential 

archaeological resources are noted for avoidance. The deployment of OBCs and OBNs dropped 

from the surface and entanglement during recovery has the potential for moderate to major impacts 

to unidentified archaeological resources. The OBNs placed by an ROV will have a nominal impact 

to archaeological resources, as the seafloor is visually inspected before placement and recovery. 

Additionally, the requirement to visually verify any snags resulting from entanglement during 

recovery would also help to mitigate further potential damages to archaeological resources. In 

summary, the impacts to archaeological from each project-related IPF (including routine activities) is 

expected to range from nominal to major (if no mitigation is imposed).

4.11.4.2 Impacts of an Accidental Fuel Spill

Under Alternative C, impacts of an accidental fuel spill on archaeological resources would be 

very similar to those analyzed for Alternative A in Chapter 4.11.2.2. A small proportion of the 

heavier fuel components could adhere to particulate matter in the upper portion of the water column 

and sink, and particulate matter contaminated with diesel fuel could eventually reach the seafloor. 

An accidental diesel fuel spill would be expected to result in nominal impacts to archaeological 

resources.

4.11.4.3 Cumulative Impacts

Impact analyses presented in Chapters 4.11.4.1 and 4.11.4.2 determined that activities 

projected to occur under Alternative C would result in nominal to major (if no mitigations are 

imposed) impacts to archaeological resources. Mitigation measures for the proposed action under 

Alternative C are described in Chapter 2.3 and summarized in Chapter 4.11.4.1. A detailed impacts 

assessment under the cumulative scenario is provided in Alternative A (Chapter 4.11.2.3). Most 

mitigation measures under Alternative C would not change the extent, severity, or timing of activities 
4-362 Description of the Affected Resources and Impact Analysis

in the proposed action; thus, the resultant impacts to archaeological resources also would not 

change because none of the mitigation measures would change the seafloor-disturbing activities or 

drilling discharges.

As discussed in Chapter 4.11.2.3, a significant amount of vessel traffic is expected to occur 

under the cumulative scenario. All vessel movements are associated with a risk of collision and 

subsequent loss of fuel. The risk of accidental fuel spills arising from a vessel collision under the 

cumulative scenario is expected to be nominal. The changes to seismic survey protocols would not 

substantially change the risk of a small fuel spill. Overall, the risk of a small fuel spill and the 

potential cumulative impacts to archaeological resources would be the same under Alternative C as 

determined under Alternative A and would result in a nominal incremental increase in impacts from 

seafloor disturbance and drilling discharges and risk of a collision-based fuel spill.

4.11.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs, impact significance criteria, and impact conclusions for Alternative D are the same 

as for Alternative A (Chapter 4.11.2). The additional mitigation measure under Alternative D would 

not alter the impact levels to archaeological resources from seafloor disturbance or drilling 

discharges as described in Alternatives A and C (Chapters 4.11.2.1 and 4.11.4.1), and impacts 

would remain nominal to major. Under Alternative D, impacts of an accidental fuel spill on 

archaeological resources would be as described in Alternatives A and C (Chapters 4.11.2.2 and 

4.11.4.2) and would remain nominal. 

4.11.5.1 Impacts of Routine Activities

The additional mitigation measures implemented under Alternative D would not change the 

extent, severity, or timing of G&G activities related to impacts to archeological resources. As 

discussed under Alternative A in Chapter 4.11.2, there are two applicable routine IPFs for 

archaeological resources: seafloor disturbance and drilling discharges. The mitigation measures 

under Alternative D would not change the extent, severity, or timing of seafloor disturbance or drilling 

discharges. Except in the case of OBC and OBN surveys, BOEM considers seafloor disturbance 

related to G&G surveys and drilling discharges to have a nominal impact to the seafloor. If sitespecific information regarding potential archaeological resources is provided to BOEM prior to 

approving G&G activities involving the seafloor, seafloor-disturbing activities and the potential for 

entanglement would likely result in nominal impacts to archaeological resources. Archaeological 

review is not required in advance of OBN and OBC surveys; however, identified and potential 

archaeological resources are noted for avoidance. The deployment of OBCs and OBNs dropped 

from the surface and entanglement during recovery has the potential for moderate to major impacts 

to unidentified archaeological resources. The OBNs placed by an ROV will have a nominal impact 

to archaeological resources, as the seafloor is visually inspected before placement and recovery. 

Additionally, the requirement to visually verify any snags resulting from entanglement during 

recovery would also help to mitigate further potential damages to archaeological resources. In 

summary, the impacts to archaeological from each project-related IPF (including routine activities) is 

expected to range from nominal to major (if no mitigations are imposed).
Gulf of Mexico G&G Activities Programmatic EIS 4-363

4.11.5.2 Impacts of an Accidental Fuel Spill

Under Alternative D, impacts of an accidental fuel spill on archaeological resources would be 

very similar to those analyzed for Alternative A in Chapter 4.11.2.2. Because there is the potential 

for a small proportion of the heavier fuel components to adhere to particulate matter in the upper 

portion of the water column and sink, particulate matter contaminated with diesel fuel could 

eventually reach the seafloor. An accidental diesel fuel spill would be expected to result in nominal

impacts to archaeological resources.

4.11.5.3 Cumulative Impacts

Impact analyses presented in Chapters 4.11.5.1 and 4.11.5.2 determined that activities 

projected to occur under Alternative D would result in nominal to major (if no mitigations are 

imposed) impacts to archaeological resources. 

Mitigation measures for the proposed action under Alternative D are described in 

Chapter 2.4 and summarized in Chapter 4.11.5.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.11.2.3). The mitigation measures are 

the same as described for Alternative C with the addition of shutdown protocols during seismic 

operations for all marine mammals (except bow-riding dolphins). The addition of shutdown protocols 

for all marine mammals except bow-riding dolphins under Alternative D would not change the extent, 

severity, or timing of activities in the proposed action; thus, the resultant impacts to archaeological 

resources also would not change because none of the mitigation measures would change the 

seafloor-disturbing activities or drilling discharges.

A significant amount of vessel traffic is expected to occur under the cumulative scenario, as 

discussed in Chapter 4.11.2.3. All vessel movements are associated with a risk of collision and 

subsequent loss of fuel. The risk of accidental fuel spills arising from a vessel collision under the 

cumulative scenario is expected to be nominal. The expanded shutdown protocols would not 

substantially change the risk of a small fuel spill. Overall, the risk of a small fuel spill and the 

potential cumulative impacts to archaeological resources would be the same under Alternative D as 

determined under Alternative A and would result in a nominal incremental increase in impacts from 

seafloor disturbance and drilling discharges and risk of a collision-based fuel spill.

4.11.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs, impact significance criteria, and impact conclusions for Alternative E are the same 

as for Alternative A (Chapter 4.11.2).

4.11.6.1 Impacts of Routine Activities

Under Alternatives E1 and E2, deep-penetration, multi-client activities would be reduced by 

10 percent and 25 percent, respectively, which does not apply to the IPFs for archaeological 

resources (i.e., seafloor disturbance or drilling discharges). Therefore, as discussed in Chapter

4.11.2.1, except in the case of OBC and OBN surveys, BOEM considers seafloor disturbance 
4-364 Description of the Affected Resources and Impact Analysis

related to G&G surveys and drilling discharges to have a nominal impact to the seafloor in 

Alternative E. If site-specific information regarding potential archaeological resources is provided to 

BOEM prior to approving G&G activities involving the seafloor, seafloor-disturbing activities and the 

potential for entanglement would likely result in nominal impacts to archaeological resources. 

Archaeological review is not required in advance of OBN and OBC surveys; however, identified and 

potential archaeological resources are noted for avoidance. The deployment of OBCs and OBNs 

dropped from the surface and entanglement during recovery has the potential for moderate to 

major impacts to unidentified archaeological resources. The OBNs placed by an ROV will have a 

nominal impact to archaeological resources, as the seafloor is visually inspected before placement 

and recovery. Additionally, the requirement to visually verify any snags resulting from entanglement 

during recovery would also help to mitigate further potential damages to archaeological resources. 

In summary, the impacts to archaeological from each project-related IPF (including routine activities) 

is expected to range from nominal to major. 

4.11.6.2 Impacts of an Accidental Fuel Spill

Under Alternative E, impacts of an accidental fuel spill on archaeological resources would be 

very similar to those analyzed for Alternative A (Chapter 4.11.2.2). The analysis concluded that a 

small fuel spill at the sea surface would be unlikely to have any effect. Alternative E1 would reduce 

the number of surveys and vessels because of a 10 percent reduction of oil and gas activities, but 

this would not substantially change the risk of a small fuel spill. A small diesel spill is expected to 

disperse and weather rapidly, with evaporation of volatile components. Particulate matter 

contaminated with diesel fuel eventually would reach the seafloor, within or outside the AOI, 

depending on fuel spill location, water depth, ambient currents, and sinking rate. However, given the 

relatively small size of the fuel spill and the loss of most spilled fuel through evaporation and 

dispersion, a small diesel fuel spill at the surface would have no effect on the seafloor and would not 

require seafloor cleanup activity. An accidental diesel fuel spill would be expected to result in 

nominal impacts to archaeological resources.

4.11.6.3 Cumulative Impacts

Impact analyses presented in Chapters 4.11.6.1 and 4.11.6.2 determined that activities 

projected to occur under Alternative E would result in nominal to major (if no mitigations are 

imposed) impacts to archaeological resources.

Mitigation measures for the proposed action under Alternative E are described in 

Chapter 2.5 and summarized in Chapter 4.11.6.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.11.2.3). The reduction of deeppenetration, multi-client activities (in line miles) by 10 percent (Alternative E1) or 25 percent 

(Alternative E2) would not change the seafloor-disturbing activities or drilling discharges; therefore, 

impacts to archeological resources would not change under Alternative E. Though there would be a 

reduction in the amount of vessel traffic under Alternative E, all vessel movements are associated 

with a risk of collision and subsequent loss of fuel. The risk of accidental fuel spills arising from a 

vessel collision under the cumulative scenario is expected to be nominal. Overall, the risk of a 
Gulf of Mexico G&G Activities Programmatic EIS 4-365

small fuel spill and the potential cumulative impacts to archaeological resources would be the same 

under Alternative E as determined under Alternative A and would result in a nominal incremental 

increase in impacts from seafloor disturbance and drilling discharges and risk of a collision-based 

fuel spill.

4.11.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs, impact significance criteria, and impact conclusions for Alternative F are the same 

as for Alternative A (Chapter 4.11.2).

4.11.7.1 Impacts of Routine Activities

As discussed in Chapter 4.11.2, there are two applicable routine IPFs for archaeological 

resources: seafloor disturbance and drilling discharges. The inclusion of area closures to the 

current levels of G&G activities (as described under Alternative A) and the mitigation measures 

imposed under Alternative C would not change the extent, severity, or timing of seafloor disturbance 

or drilling discharges. Except in the case of OBC and OBN surveys, BOEM considers seafloor 

disturbance related to G&G surveys and drilling discharges to have a nominal impact to the 

seafloor. If site-specific information regarding potential archaeological resources is provided to 

BOEM prior to approving G&G activities involving the seafloor, seafloor-disturbing activities and the 

potential for entanglement would likely result in nominal impacts to archaeological resources. 

Archaeological review is not required in advance of OBN and OBC surveys; however, identified and 

potential archaeological resources are noted for avoidance. The deployment of OBCs and OBNs 

dropped from the surface and entanglement during recovery has the potential for moderate to 

major impacts to unidentified archaeological resources. The OBNs placed by an ROV will have a 

nominal impact to archaeological resources, as the seafloor is visually inspected before placement 

and recovery. Additionally, the requirement to visually verify any snags resulting from entanglement 

during recovery would also help to mitigate further potential damages to archaeological resources. 

In summary, the impacts to archaeological resources from each project-related IPF (including routine 

activities) is expected to range from nominal to major. 

4.11.7.2 Impacts of an Accidental Fuel Spill

Under Alternative F, impacts of an accidental fuel spill on archaeological resources would be 

very similar to those analyzed for Alternative A in Chapter 4.11.2.2. Because there is the potential 

for a small proportion of the heavier fuel components to adhere to particulate matter in the upper 

portion of the water column and sink, particulate matter contaminated with diesel fuel could 

eventually reach the seafloor. An accidental diesel fuel spill would be expected to result in nominal

impacts to archaeological resources.

4.11.7.3 Cumulative Impacts

Impact analyses presented in Chapters 4.11.7.1 and 4.11.7.2 determined that activities 

projected to occur under Alternative F would result in nominal to major (if no mitigations are 

imposed) impacts to archaeological resources.
4-366 Description of the Affected Resources and Impact Analysis

Mitigation measures for the proposed action under Alternative F are described in Chapter

2.6 and summarized in Chapter 4.11.7.1. A detailed impacts assessment under the cumulative 

scenario is provided in Alternative A (Chapter 4.11.2.3). Mitigation measures under Alternative F 

are similar to Alternative C with the addition of area closures in four areas: the CPA Closure Area; 

the EPA Closure Area; the Dry Tortugas Closure Area; and the Flower Gardens Closure Area. Most 

mitigation measures under Alternative F would not change the extent, severity, or timing of activities 

in the proposed action; thus, the resultant impacts to archaeological resources also would not 

change because none of the mitigation measures or closures would change the seafloor-disturbing 

activities or drilling discharges. Therefore, the impacts would remain unchanged from Alternative A 

under the Alternative F cumulative scenario.

A significant amount of vessel traffic is expected to occur under the cumulative scenario, as 

discussed in Chapter 4.11.2.3. All vessel movements are associated with a risk of collision and 

subsequent loss of fuel. The risk of accidental fuel spills arising from a vessel collision under the 

cumulative scenario is expected to be nominal. The area closures would not substantially change 

the risk of a small fuel spill. Overall, the risk of a small fuel spill and the potential cumulative impacts 

to archaeological resources would be the same under Alternative E as determined under 

Alternative A and would result in a nominal incremental increase in impacts from seafloor 

disturbance and drilling discharges and risk of a collision-based fuel spill.

4.11.8 Impacts – Alternative G (No New Activity Alternative)

The IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.11.2).

4.11.8.1 Impacts of Routine Activities

Under Alternative G, a limited number of VSP and SWD surveys would occur and no bottomdisturbing activities are projected (Table 2.7-1). If no new bottom-disturbing activities occur under 

Alternative G, then no impact will occur to the archeological resources from bottom disturbance or 

drilling discharges; therefore, no impacts are expected under Alternative G.

4.11.8.2 Impacts of Accidental Fuel Spill

Under Alternative G, impacts of an accidental fuel spill on archaeological resources would be 

very similar to those analyzed for Alternative A (Chapter 4.11.2.2). The analysis concluded that a 

small fuel spill at the sea surface would be unlikely to have any effect. Alternative G would cease 

future activity, but this would not substantially change the risk of a small fuel spill from ongoing 

activity. A small diesel spill is expected to disperse and weather rapidly, with evaporation of volatile 

components. An accidental diesel fuel spill would be expected to result in no impacts to nominal

impacts to archaeological resources.
Gulf of Mexico G&G Activities Programmatic EIS 4-367

4.11.8.3 Cumulative Impacts

Impact analyses presented in Chapters 4.11.8.1 and 4.11.8.2 determined that activities 

projected to occur under Alternative G would result in no impact to nominal to archaeological 

resources.

Mitigation measures for the proposed action under Alternative G are described in 

Chapter 2.7 and summarized in Chapter 4.11.8.1. A detailed impacts assessment under the 

cumulative scenario is provided in Alternative A (Chapter 4.11.2.3). The cease of activity for future 

G&G surveys requiring a permit/authorization from BOEM would not be adding an increase to the 

cumulative impacts because VSP and SWD are linked to current activity. Overall, the impacts to 

archeological resources would remain nominal to no impact for Alternative G.

Though there would be no vessel involvement under Alternative G, all current vessel 

movements are associated with a risk of collision and subsequent loss of fuel. The risk of accidental 

fuel spills arising from a vessel collision under the cumulative scenario is expected to be nominal. 

Overall, the risk of a small fuel spill and the potential cumulative impacts to archaeological resources 

would be the same under Alternative G as determined under Alternative A and would result in a 

nominal incremental increase in impacts from seafloor disturbance and drilling discharges and risk 

of a collision-based fuel spill. Seafloor-disturbing activities associated with spill cleanup are not 

expected. Therefore, the impacts to archaeological resources from spill response and cleanup 

activities associated with fuel spills from vessels under the cumulative activities scenario are 

expected to be no impacts to nominal impacts. 

4.12 OTHER MARINE USES

4.12.1 Description of the Affected Environment

Other uses of the marine environment in the AOI include the following: 

• shipping and marine traffic; 

• MWAs, 

• sand and gravel mining;

• renewable energy development; 

• ocean dredged material disposal; and 

• oil and gas exploration and production.

Other marine uses of Gulf of Mexico waters and resources occur constantly. While these 

other activities in the GOM are most frequently described as multiple-use conflicts, the potential for 

geophysical surveys to interfere with these other uses does exist. Those potential impacts are 

discussed here, and detailed descriptions of these other marine uses are described in detail in 

Appendix E. The following chapters provide brief summaries.
4-368 Description of the Affected Resources and Impact Analysis

4.12.1.1 Shipping and Marine Transportation

The USCG designates shipping fairways and establishes traffic separation schemes that 

control the movement of vessels as they approach ports (Figure 4.12-1) (33 CFR part 166).

Seven deepwater commercial ports that can handle fully laden Panamax ships (pre-Panama 

Canal expansion) are located in the AOI as follows: Houston, Texas; Corpus Christi, Texas; 

Beaumont, Texas; Galveston, Texas; New Orleans, Louisiana; Mobile, Alabama; and Tampa, 

Florida. These deepwater ports are discussed further in Chapter 4.12.1.6. Military vessels 

operating in the AOI are associated with training and testing activities (Chapter 4.12.1.2). 

Commercial business craft include support vessels, fishing vessels (Chapter 4.9), and ferries. 

Commercial recreational craft may include cruise ships and fishing charters (Chapter 4.10).

4.12.1.2 Military Warning Areas and Other Military Uses

Twelve MWAs and six EWTAs (Figure 4.12-2) (NTL 2014-BOEM-G04) have been 

established in the AOI to allow military forces to conduct training and testing activities, including 

various air-to-air, air-to-surface, and surface-to-surface Naval fleet training, submarine and 

antisubmarine training, and Air Force exercises. 

These areas are multi-use areas where military operations and oil and gas exploration and 

production have coexisted for many years. The MWAs and EWTAs cumulatively include 75 percent 

of the total acreage of the WPA, 31 percent of the total acreage of the CPA, and 91 percent of the 

total acreage of the EPA. 

Portions of the AOI are further classified as danger zones, which can be closed or subject to 

limited public access during intermittent periods. Danger zones and restricted areas are defined and 

described by 33 CFR § 334.2 and encompass areas used for target practice, bombing, and rocket 

firing or are areas that provide security for Government property and/or protection to the public from 

the risks of property damage or injury from the Government’s use of the area.

Additionally, the GOM has 26 sites distributed across all three planning areas that contain 

unexploded ordnances, submerged explosives, depth charges, torpedoes, or other obstructions; or 

sites that are identified as discontinued dump sites for explosives or other wastes (Figure 4.12-2).

4.12.1.3 Sand and Gravel Mining

Offshore sand resources utilization in the AOI is limited to coastal areas where sand is 

needed for nourishment and restoration projects. BOEM’s Marine Minerals Program is implementing

several measures to help safeguard the most significant OCS sediment resources, reduce multiple 

use conflicts, and minimize interference with oil and gas operations under existing leases or rightsof-way. Figure 4.12-3 shows the OCS lease blocks with significant sediment resources (USDOI, 

BOEM, 2015d). Table 4.12-1 provides the recent projects in Florida and Louisiana, the cubic yards 

of sand, and the miles of restored shoreline (USDOI, BOEM, 2015e). Because of the nearshore 
Gulf of Mexico G&G Activities Programmatic EIS 4-369

nature of the sand and gravel activities, it is not anticipated that geophysical surveys would impact 

them to any extent beyond nominal. 

4.12.1.4 Renewable Energy Development – Wind Energy

The EPAct, signed by President Bush in 2005, authorized USDOI to grant leases, 

easements, or rights-of-way in the OCS for the development of energy resources other than 

traditional hydrocarbons on the OCS. The Programmatic Environmental Impact Statement for 

Alternative Energy Development and Production and Alternate Use of Facilities on the Outer 

Continental Shelf, Final Environmental Impact Statement was published by MMS (BOEM’s 

predecessor) in 2007 (USDOI, MMS, 2007c), leading the way for BOEM to develop an alternative 

energy program, which was published as a final rule on April 29, 2009 in 30 CFR part 285.

There are no operational wind farms within the AOI and there have been no Wind Energy 

Areas identified by USDOI or BOEM within the AOI. However, one licensed wind platform is 

currently the site of a meteorological monitoring tower used to track winds offshore of Galveston, 

Texas, in State waters (Coastal Point Energy, 2015), and a 150-MW wind farm is scheduled to be 

built on the site. Neither the company nor the State have any intentions at this time of proposing 

activities in Federal waters. Because of the lack of projected wind farms in the Gulf of Mexico, it is 

not anticipated that geophysical surveys would impact them.

4.12.1.5 Ocean Dredged Material Disposal Sites

Regulated by the USEPA, ODMDSs are composed of materials from maintenance dredging 

and are available for potential beneficial uses to restore and create habitat, beach nourishment 

projects, and industrial and commercial development. There are 19 ODMDSs designated within the 

AOI (40 CFR § 228.15; USEPA, 2015) (Figure 4.12 4).

4.12.1.6 Oil and Gas Exploration, Development, and Production

The Gulf of Mexico OCS is divided into the WPA, CPA, and EPA, and as of June 1, 2016, 

there were 3,998 active leases in the Gulf of Mexico OCS (USDOI, BOEM, 2015f). The majority of 

the active leases are located in the WPA and CPA with only 46 active leases located in the EPA. 

The Gulf of Mexico OCS Region currently oversees approximately 3,400 offshore oil and natural gas 

facilities accounting for nearly 30 percent of the Nation’s domestic oil production and approximately 

11 percent of domestic natural gas production (USDOI, BSEE, 2014b).

The GOMESA was signed into law by the President on December 20, 2006. Among other 

provisions, this Act banned oil and gas leases within 125 mi (201 km) of the Florida coastline in the 

EPA until at least 2022. The act also banned new oil and gas leases from all areas in the EPA east 

of the Military Mission Line (86°41' W. longitude) and areas in the CPA within 161 km (100 mi) of the 

Florida coastline (Figure 4.12-5).
4-370 Description of the Affected Resources and Impact Analysis

Offshore Deepwater Ports

According to MARAD, the LOOP is the only operational offshore deepwater port in the GOM 

with offshore marine terminal facilities. The LOOP carries 13 percent of all imported oil to the U.S. 

via subsea pipelines, transporting it onshore to Lafourche Parish where it is stored and piped via 

onshore pipelines to markets throughout the country.

Pipeline and Cable Infrastructure

There is an extensive network of pipelines in the AOI that carry produced oil and gas from 

the offshore field to refineries and terminals onshore (Figure 4.12-6a-c).

The IBP began operation of a fiber optic communication system in 2008, connecting seven of 

BP’s platforms with the BP enterprise. In addition, there are several other submarine power cables 

and multiple umbilicals associated with oil and gas platforms and field development within the GOM 

(Figure 4.12-7).

4.12.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative) 

As shown in Table 4.1-2, the IPFs that may impact other marine uses within the AOI include 

(1) vessel traffic, (2) aircraft traffic and noise, (3) stand-off distance, (4) seafloor disturbance, and 

(5) accidental fuel spills. For the purpose of this discussion, vessel traffic and stand-off distances 

will be addressed together because they are interrelated (seismic surveys conducted under all three 

program areas will result in this IPF) and result in impacts of a similar nature. In considering the 

potential impacts with areas of disturbance (i.e., on the seafloor), it is important to make the 

distinction between the AOI and BOEM’s planning areas. The total AOI area of 689,166 km2

(266,089 mi2

) includes 45,630 km2 (17,618 mi2) of State waters outside of the planning area 

boundaries, so the total planning areas considered with the potential to be impacted by seafloor 

disturbance is 643,536 km2 (248,471 mi2

).

Impact Levels and Impact Significance Criteria

As described in Chapter 4.1.2, significance criteria reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). Each impact significance criterion is developed on a 

resource-specific basis to determine the appropriate impact level for each IPF. For other marine 

uses, the below significance criteria have been used to evaluate the level of impact for each IPF.

Nominal impacts to other marine uses would include those where little to no measurable 

impacts on other marine uses are observed or expected.

Minor impacts to other marine uses would include those that are detectable but are not 

severe or extensive. Minor impacts to other marine uses would include limited, localized, and short-
Gulf of Mexico G&G Activities Programmatic EIS 4-371

term disruptions of other marine uses (from vessel traffic, stand-off distances, space-use conflicts, 

and seafloor disturbance).

Moderate impacts to other marine uses would be detectable and extensive but not severe or 

detectable, localized, and severe. Moderate impacts to other marine uses would include detectable 

disruptions of other marine uses (from vessel traffic, stand-off distances, space-use conflicts, and 

seafloor disturbance).

Major impacts to other marine uses would be detectable, extensive, and severe. Major 

impacts to other marine uses would include any G&G activity that results in (1) a substantial 

increase in the volume of vessel traffic for an extended period over a large area resulting in an 

interruption of other marine uses; (2) broad-scale, long-term stand-off distances resulting in longterm, space-use conflicts with other marine uses; or (3) severe and extensive disturbance to the 

seafloor.

4.12.2.1 Impacts of Routine Activities

4.12.2.1.1 Vessel Traffic and Stand-Off Distance

Vessel traffic generated by each type of G&G survey proposed within the AOI is shown in 

Table 3.2 7, and the types of surveys and activity level scenarios are described in Chapter 3. The 

level of vessel traffic related to G&G surveys would not represent a significant increase in total 

vessel traffic compared with existing vessel traffic (Table 3.4-2) in offshore waters. When G&G 

survey vessels are actively performing data acquisition, the vessels are slow-moving, which allows 

for other vessels to easily move out of the way.

The proposed G&G activities include extensive 2D and 3D surveys involving towed-streamer 

arrays (Chapter 3.2.1.2) requiring a stand-off distance or an operational distance, where other 

vessels are required to stay away from the seismic gear (towed array), to avoid interference within 

the AOI. The stand-off distance is simply an area monitored by a seismic survey operator and has 

no formal status or designation by the USCG. However, a Local Notice to Mariners would be issued 

that would specify the survey dates and locations and the recommended avoidance requirements.

The extent of the stand-off distance varies depending on the array configuration and other 

factors (Chapter 3.3.1.5). Because survey vessels move at speeds of 4.5 kn (5.2 mph), the length 

of time that any particular point would be within the stand-off distance would be approximately 

1 hour.

Survey vessels for non-seismic survey types (e.g., HRG, grab sampling, and coring) would 

be relatively small and are expected to make daily round-trips to their shore base. Depending on the 

location of the survey area, vessels could mobilize from several different ports throughout the AOI. 

Activities related to renewable energy are not anticipated, and marine minerals surveys (e.g., HRG, 

grab sampling, and vibracoring) would require relatively few round-trips per year (Table 3.2-6).
4-372 Description of the Affected Resources and Impact Analysis

4.12.2.1.2 Shipping and Marine Transportation Vessel Traffic

Impacts from G&G activities on shipping and marine transportation would result from limited 

access to routes when stand-off distances are in place. Impacts would be relatively short with the 

time and extent dependent on the type of G&G activity; all impacts would be of short duration, on the 

order of days, for seismic surveys related to marine minerals (e.g., HRG surveys) and up to months 

with seismic surveys related to oil and gas exploration (e.g., 2D, 3D, 4D, WAZ, and HRG surveys). 

Stand-off distances would move with the investigation equipment, so one specific location would not

be impacted for an extended period of time. Lease areas to be surveyed would not be located within 

maintained navigation channels and would not disrupt primary commercial ship traffic routes.

Based on the vessel traffic expected under G&G activities, impacts to shipping and marine 

transport are expected to be nominal because the number of G&G-related vessel trips involved and 

the duration of these surveys is small in relation to the existing vessel traffic throughout the AOI. 

There would not be a sufficient increase in vessel traffic to impact shipping and marine 

transportation. Under Alternative A, the level of vessel traffic related to G&G surveys already 

currently exists in the AOI and the proposed action would not be additive. Overall, impacts to 

shipping and marine transportation are expected to be nominal. 

4.12.2.1.3 Military Warning Areas and Other Military Uses

The MWAs and other military use areas, including restricted areas and danger zones, and 

unexploded ordnance sites are discussed in Chapter 4.12.1.2. Much of the AOI is within MWAs 

(Figure 4.12-2), and G&G activities would be subject to restrictions imposed by military needs, rules, 

and regulations. Coordination by the vessel operators or contractors performing G&G activities is 

required with the appropriate military range complex or command headquarters. Within the AOI, 

military and oil and gas exploration and production have coexisted for many years. Vessel traffic 

levels and stand-off distances associated with G&G activities are small and of limited duration but 

could be an obstruction to surface use by military units, depending on their location. Conflicts 

between G&G activities and scheduled military operations can be avoided through coordination as 

stipulated in NTL 2014-BOEM-G04 (Chapter 2). The potential impacts of G&G activities to military 

range complexes, MWAs, or areas of other military use would be nominal and avoidable when 

coordinated with the USDOD prior to commencement.

4.12.2.1.4 Sand and Gravel Mining

The OCS lease blocks within the AOI with significant sediment resources are discussed in 

Chapter 4.12.1.3 and shown in Figure 4.12-3. The G&G surveys are conducted during and in 

support of sand and gravel mining operations.

The marine minerals scenario includes an estimated maximum activity level of approximately 

2,196 line mi for HRG surveys (Table 3.2-8), with additional grab sampling and vibracoring 

(approximately 1 week of survey time) for all geophysical survey activities (Table 3.2-6). Because a 
Gulf of Mexico G&G Activities Programmatic EIS 4-373

portion of the G&G activities are in support of sand and gravel mining, impacts are expected to be 

nominal as there is no potential for use conflicts.

4.12.2.1.5 Renewable Energy Development

Renewable energy development within the AOI is discussed in Chapter 4.12.1.4. Currently, 

there are no operational wind farms in the GOM, and no wind energy areas have been identified by 

BOEM. Because there are no existing renewable energy projects within the AOI, there will be no 

impacts to renewable energy development from G&G vessel traffic and stand-off distances 

(resulting from seismic surveys utilizing towed arrays) within the AOI under Alternative A.

4.12.2.1.6 Ocean Dredged Material Disposal Sites

There are 16 ODMDSs designated within the AOI (Chapter 4.12.1.5; Figure 4.12-4). 

Impacts from vessel traffic and stand-off distances associated with the proposed action are expected 

to be nominal because the number of vessels involved and the duration of the surveys is small 

(Table 3.2-7).

Preclusion of vessels using the disposal sites would constitute a space-use conflict. Seismic 

vessels conducting G&G activities would be under a “restricted ability to maneuver” designation, 

which means other vessels in the path of the survey vessel must give way. Overall, impacts to 

ODMDSs from G&G activities are expected to be nominal. 

4.12.2.1.7 Oil and Gas Exploration, Development, and Production

Impacts to oil and gas exploration, development, and production from G&G vessel traffic and 

stand-off distances (resulting from seismic surveys) would be nominal. Such impacts would be 

relatively short, on the order of days for small-scale seismic surveys, HRG surveys, grab sampling, 

and coring, and up to a few months for large-scale seismic surveys related to oil and gas exploration 

(Table 3.2-7). Stand-off distances would move with the investigation equipment so that one specific 

location is not impacted for an extended duration. Multiple G&G survey types are consistent with the 

ongoing use of and conducted in support of oil and gas exploration, development, and production 

(Tables 3.2-1 and 3.2-2). All G&G surveys are subject to Form BOEM-0327 permit applications, 

which state, as a permit condition, that permitted activities do not “Interfere with or endanger 

operations under any lease or right-of-way or permit issued or maintained pursuant to the OCSLA.” 

The permit condition will limit or completely prevent conflicts between G&G activities and oil and gas 

exploration, development, and production resulting from vessel traffic and stand-off distances. 

Overall, impacts to oil and gas exploration, development, and production from G&G activities are 

expected to be nominal. 

4.12.2.1.8 Pipeline and Cable Infrastructure

An extensive network of pipelines in the GOM carries all gas production and >99 percent of 

OCS oil production from the offshore field to refineries and terminals onshore (Figure 4.12-6a-c). In 

2007, BP was responsible for the installation of a fiber optic communication system in the GOM that 
4-374 Description of the Affected Resources and Impact Analysis

extends into deep water to provide communications among assets. In addition, there are several 

submarine power cables and umbilicals associated with oil and gas platforms and field development 

within the GOM (Figure 4.12-7). Because pipelines and submarine cables are bottom-founded 

equipment, vessel traffic and stand-off distances related to G&G survey activities would have no 

impact to the existing infrastructure.

4.12.2.1.9 Routine Activities Impact Conclusions

Based on the vessel traffic and associated stand-off distances, aircraft traffic, and seafloor 

disturbance expected under G&G activities, impacts to shipping and marine transport, military, sand 

and gravel, renewable energy, ODMDSs, oil and gas activities, and infrastructure are expected to 

range from no impact to nominal. The level of G&G-related activity involved and the duration of 

these surveys is small in relation to the existing vessel traffic throughout the AOI. There would not 

be a sufficient increase in vessel or aircraft traffic or seafloor disturbances to impact the other marine 

uses activities existing in the AOI.

4.12.2.2 Impacts of an Accidental Fuel Spill

An accidental event could result in the release of diesel fuel by a survey vessel from a vessel 

collision or spillage during at-sea fuel transfer operations. Based on USCG spill statistics, a spill 

scenario was developed in Chapter 3.3.2.1 that assumes a diesel spill volume of 1.2 to 7.1 bbl. 

Spills occurring at the ocean surface would disperse and weather, and the volatile components of 

the fuel would evaporate. Fuel and diesel used for the operation of survey vessels is light and would 

float on the water surface. Given the relatively small size of the spill and the loss of most spilled fuel 

through evaporation and dispersion, a small diesel fuel spill at the surface would have no effect on 

other marine uses, other than perhaps temporary loss of access near the spill.

Due to the extensive existing network of commercial shipping lanes/fairways in the GOM, 

traffic coordination and regulation by the USCG, and the regulation of structures on the OCS under 

OCSLA, vessel-to-vessel collisions and vessel-to-structure collisions have been minimal compared 

with the extent of existing vessel traffic and movement. Because of the low potential of a vessel 

collision occurring and the potential for a resultant spill even lower, the risk of accidental fuel spills is 

expected to be remote.

The impacts of an accidental spill event would depend on the size and location of the spill in 

addition to the meteorological conditions at the time. A small diesel spill would have nominal impact 

on other marine uses because it would only prohibit full use of a small area by other marine users for 

a very limited amount of time.

4.12.2.3 Cumulative Impacts

The cumulative scenario in Chapter 3.4 describes the other past, present, and reasonably 

foreseeable future actions. This cumulative impacts assessment considers the combined effects 

and assesses the incremental increase in impact from the proposed action when added to activities 
Gulf of Mexico G&G Activities Programmatic EIS 4-375

in the cumulative scenario. The IPFs identified for other marine uses are compared with the IPFs 

from each of the cumulative scenario components in order to focus this cumulative analysis on those 

activities that coincide spatially and temporally with the proposed action (Table 3.4-1). The G&G 

activity IPFs that are included in the cumulative assessment are the same as those assessed under 

routine activities and accidental events. The following analysis evaluates the incremental increase 

by IPF and provides a conclusion of the cumulative incremental increase within the AOI.

The G&G activities have been ongoing in the GOM for at least the past 30 years and it is 

reasonable to assume they will continue into the future; however, for the purpose of this 

Programmatic EIS, the cumulative analysis assesses a 10-year timeframe to coincide with the 

proposed action because it is not expected that G&G activities will have lasting effects or extend 

beyond the 10-year timeframe of this Programmatic EIS.

The following analysis considers whether the incremental impact from the proposed action, 

when added to or acting synergistically with existing impact sources from the cumulative impacts 

scenario, may result in a significant collective impact.

A detailed impact analysis of activities included in the cumulative scenario has been 

conducted as part of the commercial fishing (Chapter 4.9), recreational fishing (Chapter 4.10), and 

other marine uses (Chapter 4.12) chapters of this Programmatic EIS. Because several of the 

activities included in the cumulative scenario are included in the other marine uses category, the 

cumulative scenario will be addressed according to IPF rather than cumulative component.

4.12.2.3.1 Vessel Traffic and Stand-Off Distances

The potential impacts to other marine uses from vessel traffic and stand-off distances stem 

from space-use conflicts. Vessel traffic under the cumulative impacts scenario would originate from 

all of the cumulative scenario components except natural events. Table 3.4-2 provides a summary 

of the oil and gas support vessel operations anticipated under the cumulative scenario within the 

OCS Program. Additional vessel traffic from G&G operations under the proposed action 

(Chapter 3.3.1.3) would not represent a significant increase to existing vessel traffic from cumulative 

scenario activities within the AOI and would not be sufficient to impact navigation, port capacity, or 

shipping and marine transportation. Therefore, the proposed action would produce a nominal

incremental increase in vessel traffic under the cumulative scenario.

Stand-off distances discussed in this analysis refer specifically to the area surrounding G&G 

seismic vessels to protect the towed-streamers. The implemented stand-off distance for the seismic 

surveys would result in space-use conflict impacts if multiple G&G activities under the proposed 

action occur simultaneously within close proximity of each other. Stand-off distances established for 

multiple projects could result in a larger cumulative area excluded from short-term use by other 

vessels and may result in a longer time period where other marine uses are prohibited from certain 

areas. This type of cumulative impact could be most acute where stand-off distances and an 

increase in vessel traffic occur near commercial harbors. However, the level of increased vessel 
4-376 Description of the Affected Resources and Impact Analysis

traffic would not increase significantly with the cumulative action scenario; therefore, only a nominal

incremental increase in impacts to other marine uses are expected from stand-off distances under 

the cumulative scenario.

4.12.2.3.2 Aircraft Traffic and Noise

Aircraft traffic under the cumulative impacts scenario would originate from the OCS Program, 

State waters oil and gas, military, and scientific research activities (Table 3.4-1). Helicopter traffic 

would result from oil and gas exploration activities, as they are often used for transporting personnel 

to offshore oil drilling rigs and platforms. Table 3.4-2 provides a summary of the oil and gas support 

vessel (helicopters) operations anticipated under the cumulative scenario within the OCS Program.

Additional vessel traffic from G&G operations under the proposed action (Table 3.2-7) would 

not represent a significant increase to existing vessel traffic from cumulative operations within the 

AOI and would not be sufficient to interfere with normal commercial traffic or to add considerable 

pressure to the air traffic control system. Aircraft traffic levels and the duration of airborne surveys 

associated with G&G activities under the proposed action are very limited in terms of survey area 

and duration. Therefore, the proposed action would produce a nominal incremental increase in total 

aircraft activity and associated impacts expected under the cumulative scenario.

4.12.2.3.3 Seafloor Disturbances

Several activities under components of the cumulative scenario would involve seafloor 

disturbances, including oil and gas development, marine minerals use, commercial fishing, dredged 

material disposal, new cable infrastructure, military activities, scientific research, maintenance 

dredging, and coastal restoration programs. Seafloor-disturbing activities associated with the 

components of the cumulative scenario over the next 10 years will include the construction and 

installation of a maximum of 8,233 exploration and production wells, the installation of a maximum of 

507 production structures (e.g., caissons and multi-leg platforms), and a maximum of 17,437 km 

(10,835 mi) of pipelines (Table 3.4-2). Because there are no renewable energy activities projected, 

related seafloor disturbances would be zero. Seafloor disturbances associated with marine mineral 

uses would be in pre-determined OCS sand resource areas (Chapter 3.2.3) for use in coastal 

restoration. Because of the effectiveness of mitigation measures imposed on all seafloor-disturbing 

activities resulting from the proposed action, impacts were determined to be nominal

(Chapter 4.12.2.1) 

4.12.2.3.4 Cumulative Impact Conclusions

As discussed in Chapter 4.12.2.1, based on the vessel traffic and associated stand-off 

distances, aircraft traffic, and seafloor disturbance expected under G&G activities, impacts to other 

marine uses are expected to be nominal because the level of G&G-related activity involved and the 

duration of these surveys is small in relation to the existing vessel traffic throughout the AOI. When 

assessing the contribution of the proposed G&G activities to the existing cumulative activities, there 
Gulf of Mexico G&G Activities Programmatic EIS 4-377

would be a nominal incremental increase in impacts from vessel or aircraft traffic or seafloor 

disturbances to the other marine uses activities existing in the AOI.

4.12.2.3.5 Accidental Fuel Spills

Chapter 3.4 outlines all of the activities in the cumulative scenario that could reasonably be 

expected to occur over the 10-year time period. A sizeable amount of vessel traffic is expected to 

occur under the cumulative scenario from activities under each of the components, including high 

levels of vessel activity associated with shipping and marine transportation around ports along the 

northern GOM (Chapter 3.4.3.4). Military operations and commercial and recreational fishing 

activity also would contribute to overall vessel activity (Chapters 3.4.3.7 and 3.4.3.2, respectively). 

All vessel movements are associated with a risk of collision and subsequent loss of fuel. The 

proposed action would slightly increase vessel traffic activity in the AOI and the risk of collision and a 

resultant spill.

For G&G activities under the proposed action, a spill scenario was evaluated 

(Chapter 3.3.2.1), and the likelihood of a fuel spill occurring during the proposed action is 

considered remote (Chapter 4.12.2.2); impacts associated with a small diesel fuel spill are expected 

to be variable. Spills occurring at the ocean surface would disperse and weather. Volatile 

components of the fuel would evaporate as fuel and diesel used for operation of survey vessels is 

light and would float on the water surface.

With the use of AIS on large sea-going vessels, radar, and licensing of vessel captains, the 

potential of a vessel collision occurring is quite low, and the potential for a resultant spill is even 

lower. Therefore, the potential for fuel spills from vessels involved in the cumulative activities 

scenario is considered remote. The G&G vessel activities under the proposed action would produce 

a nominal incremental increase in impacts to other marine uses from a collision-based fuel spill 

under the cumulative scenario.

4.12.3 Impacts – Alternative B (Settlement Agreement Alternative)

The IPFs and impact significance criteria applied for Alternative B are the same as for 

Alternative A (Chapter 4.12.2). For the sake of brevity, those detailed analyses are incorporated for 

this analysis, and the following discussion outlines the effects of the additional mitigation measures 

included in Alternative B on other marine uses.

4.12.3.1 Impacts of Routine Activities

The additional mitigation measures under Alternative B would not change the extent, 

severity, or timing of aircraft traffic and noise and seafloor disturbance impacts; therefore, impacts to 

other marine uses would be unchanged under Alternative B and would range from no impact to 

nominal for other marine uses. Most of the mitigation measures in Alternative B would not change 

the extent, timing, or severity of impacts; only mitigation measures that may change the level of 

effect to other marine uses are assessed below.
4-378 Description of the Affected Resources and Impact Analysis

4.12.3.1.1 Coastal Waters Seasonal Restrictions (January 1 to April 30)

As discussed in Chapter 4.12.2.1, impacts of vessel traffic and stand-off distances on other 

marine uses are expected to be nominal in all cases. The additional coastal seasonal restriction 

under Alternative B would change the timing of seismic airgun surveys in coastal waters and reduce 

the vessel traffic and stand-off distances related to these surveys in coastal areas between 

January 1 and April 30. A change in survey timing in the additional closure area would result in a 

temporary reduction of impacts of vessel traffic and stand-off distances from seismic airgun surveys, 

but it would not result in an overall reduction of survey activity within the AOI; therefore, the impacts 

to other marine uses would be remain nominal under Alternative B.

4.12.3.1.2 Minimum Separation Distances

Alternative B would establish a separation distance of 40 km (25 mi) between active sound 

sources in the Areas of Concern (Chapter 2.2.2) during simultaneous deep-penetration seismic 

airgun surveys. When outside the Areas of Concern, the separation distance will be 30 km (19 mi). 

As discussed in Chapter 4.12.2, applicable routine IPFs for other marine uses are vessel 

traffic and stand-off distances, aircraft traffic and noise, and seafloor disturbance. Minimum 

separation distances for simultaneous seismic airgun surveys would not change the extent, severity, 

or timing of aircraft traffic and noise and seafloor disturbance.

Minimum separation distances required during simultaneous deep-penetration seismic 

airgun surveys under Alternative B could result in reduced impacts from vessel traffic and stand-off 

distances by separating G&G activities (i.e., the use of different ports and a reduction of vessel traffic 

within a localized area) but not enough to result in a reduced impact level. As discussed in 

Chapter 4.12.2.1, impacts of vessel traffic and stand-off distances on other marine uses are 

expected to be nominal in all cases.

4.12.3.1.3 Routine Activities Impact Conclusions

Based on the vessel traffic and associated stand-off distances, aircraft traffic, and seafloor 

disturbance expected under G&G activities, impacts to shipping and marine transport, military, sand 

and gravel, renewable energy, ODMDSs, oil and gas activities, and infrastructure are expected to 

range from no impact to nominal because the level of G&G-related activity involved and the 

duration of these surveys is small in relation to the existing vessel traffic throughout the AOI. There 

would not be a sufficient increase in vessel or aircraft traffic or seafloor disturbances to impact the 

other marine uses activities existing in the AOI.

4.12.3.2 Impacts of an Accidental Fuel Spill

Alternative B would change the timing of certain surveys because of additional coastal 

seasonal restrictions. However, spills from seismic survey vessels could not occur in the closure 

areas during times of the closure period, although spills from other survey vessels could occur 

during the closure period. A change in survey timing would not substantially change the risk of a 
Gulf of Mexico G&G Activities Programmatic EIS 4-379

small fuel spill. Overall, the risk of an accidental fuel spill and the potential impacts on other marine 

uses would be the same as under Alternative A and would be nominal. 

4.12.3.3 Cumulative Impacts

A detailed impact analysis of eight of the activities included in the cumulative scenario – 

(1) oil and gas exploration and development; (2) renewable energy development; (3) marine 

minerals use; (4) commercial and recreational fishing; (5) shipping and marine transportation; 

(6) dredged material disposal; (7) existing, planned, and new cable infrastructure; and (8) military 

activities – has been conducted as part of the commercial fishing (Chapter 4.9), recreational fishing 

(Chapter 4.10), and other marine uses (Chapter 4.12) chapters of this Programmatic EIS. Impact 

analyses presented in Chapters 4.12.3.1 and 4.12.3.2 determined that activities projected to occur 

under Alternative B would result in nominal impacts to other marine uses.

The cumulative impact analysis identified nominal incremental increases in impacts from all 

IPFs under Alternative A (Chapter 4.12.2.3). Minimum separation distances required during 

simultaneous deep-penetration seismic airgun surveys under Alternative B could result in reduced 

impacts from vessel traffic and space-use conflicts from the survey stand-off distances by separating 

G&G activities (i.e., the use of different ports and requiring transit corridors between survey vessels). 

Therefore, Alternative B would change the timing of seismic airgun surveys in certain areas, place 

limits on concurrent seismic airgun surveys, and exclude certain areas from seismic airgun surveys; 

however, the mitigation measures would not appreciably change the cumulative impacts noted under 

Alternative A.

4.12.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

The IPFs and impact significance criteria applied for Alternative C are the same as for 

Alternative A (Chapter 4.12.2). For the sake of brevity, those detailed analyses are incorporated for 

this analysis, and the following discussion outlines the effects of the additional mitigation measures 

included in Alternative C on other marine uses.

4.12.4.1 Impacts of Routine Activities

The additional mitigation measures under Alternative C would not change the extent, 

severity, or timing of aircraft traffic and noise and seafloor disturbance impacts; therefore, impacts to 

other marine uses would be unchanged under Alternative C and would range from no impact to 

nominal for other marine uses. Most of the mitigation measures in Alternative C would not change 

the extent, timing, or severity of impacts; only mitigation measures that may change the level of 

effect to other marine uses are assessed below.
4-380 Description of the Affected Resources and Impact Analysis

4.12.4.1.1 Coastal Waters Seasonal Restrictions (February 1 to May 31)

Alternative C would require seasonal restrictions for seismic airgun survey operations in 

Federal and State coastal waters of the GOM shoreward of the 20-m (66-ft) isobath between 

February 1 and May 31.

As discussed in Chapter 4.12.2.1, impacts of vessel traffic and stand-off distances on other 

marine uses are expected to be nominal. A change in survey timing in the closure area would 

reduce the impacts of vessel traffic and stand-off distances from seismic airgun surveys on other 

marine uses during the 4-month closure period; however, the overall survey activity would not be 

reduced under this alternative and a localized reduction of vessel traffic and stand-off distance is not 

enough to change the impact level; therefore, the impacts to other marine uses would remain 

nominal. 

4.12.4.1.2 Routine Activities Impact Conclusions

Based on the vessel traffic and associated stand-off distances, aircraft traffic, and seafloor 

disturbance expected under G&G activities, impacts to shipping and marine transport, military, sand 

and gravel, renewable energy, ODMDSs, oil and gas activities, and infrastructure are expected to 

range from no impact to nominal because the level of G&G-related activity involved and the 

duration of these surveys is small in relation to the existing vessel traffic throughout the AOI. There 

would not be a sufficient increase in vessel or aircraft traffic or seafloor disturbances to impact the 

other marine uses activities existing in the AOI.

4.12.4.2 Impacts of an Accidental Fuel Spill

Under Alternative C, impacts of accidental collisions or fuel spills on other marine uses would 

be very similar to those analyzed for Alternative A in Chapter 4.12.2.2. Alternative C would change 

the timing of certain surveys because of expanded seasonal restrictions (coastal waters). However, 

spills from seismic survey vessels could occur in the closure areas during times outside the closure 

period. Also, spills from other survey vessels could occur during the closure period. A change in 

survey timing would not substantially change the risk of a small fuel spill. Overall, the risk of an 

accidental fuel spill and the potential impacts on other marine uses would be the same as under 

Alternative A and would be nominal. 

4.12.4.3 Cumulative Impacts

The cumulative impact analysis identified nominal incremental increases in impacts from all 

IPFs under Alternative A. Alternative C would change the timing of seismic airgun surveys in certain 

areas and decrease impacts to other marine uses during the closure; however, a coastal seasonal 

restriction would not appreciably change the cumulative impacts noted under Alternative A and, 

therefore, overall nominal incremental increases in impacts are expected.
Gulf of Mexico G&G Activities Programmatic EIS 4-381

4.12.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

The IPFs and impact significance criteria applied for Alternative D are the same as for 

Alternative A (Chapter 4.12.2). For the sake of brevity, those detailed analyses are incorporated for 

this analysis. The additional mitigation under Alternative D would not alter the impact levels to other 

marine uses from vessel traffic, aircraft traffic and noise, stand-off distances, or seafloor disturbance 

as described in Alternatives A and C (Chapters 4.12.2.1 and 4.12.4.1) and would have no impacts

to nominal impacts. Under Alternative D, impacts of an accidental fuel spill on other marine 

resources would be as described in Alternatives A and C (Chapters 4.12.2.2 and 4.12.4.2) and 

would remain nominal. 

4.12.5.1 Impacts of Routine Activities

The additional mitigation measure (a change in shutdown protocol to include all marine 

mammals except bow-riding dolphins) under Alternative D would not change the extent, severity, or 

timing of vessel traffic and exclusion zones, aircraft traffic and noise, and seafloor disturbance

impacts; therefore, impacts to other marine uses would be unchanged under Alternative D and 

would range from no impact to nominal for other marine uses.

4.12.5.2 Impacts of an Accidental Fuel Spill

Alternative D would not add additional mitigation measures that would result in the reduced 

the risk of an accidental fuel spill; however, the potential impacts on other marine uses would be the 

same as under Alternative A (i.e., nominal).

4.12.5.3 Cumulative Impacts

Mitigation measures for the proposed action under Alternative D would not change the 

extent, severity, or timing of activities in the proposed action; thus, the resultant cumulative impacts 

to other marine uses would result in nominal incremental increases under Alternative D.

4.12.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

The IPFs and impact significance criteria applied for Alternative E are the same as for 

Alternative A (Chapter 4.12.2). For the sake of brevity, those detailed analyses are incorporated for 

this analysis, and the following discussion outlines the effects of the additional mitigation measures 

included in Alternative E on other marine uses.

4.12.6.1 Impacts of Routine Activities

The reduction of deep-penetration, multi-client activities by 10 percent (Alternative E1) or 

25 percent (Alternative E2) under Alternative E would reduce the extent, severity, and timing of 

vessel traffic, stand-off distances, and aircraft traffic and noise; therefore, impacts for these IPFs 

would decrease incrementally under Alternative E.
4-382 Description of the Affected Resources and Impact Analysis

The reduction of deep-penetration, multi-client activities under Alternatives E1 or E2 would 

not substantially change the extent, severity, or timing of seafloor disturbance from G&G activities; 

therefore, impacts to other marine uses from seafloor disturbance would remain unchanged from 

Alternative C and would range from no impact to nominal. 

Vessel traffic from deep-penetration, multi-client airgun surveys under Alternatives E1 or E2 

would decrease by 10 percent or 25 percent, respectively, in line miles, thereby decreasing the 

potential for interference with other marine uses such as shipping and marine transportation, military 

range complexes, sand and gravel mining, and ODMDSs. Helicopter traffic levels and the duration 

flights associated with crew changes are very limited in terms of area and duration, and under 

Alternatives E1 and E2, would be reduced by 10 percent or 25 percent in deep-penetration, multiclient survey line miles, respectively; therefore, potential impacts would range from no impact to 

nominal. 

4.12.6.2 Impacts of an Accidental Fuel Spill

Under Alternative E, impacts of accidental collisions or fuel spills on other marine uses would 

be very similar to those analyzed for Alternative C in Chapter 4.12.2.2, which indicated that a small 

spill at the sea surface would be unlikely to have any effect on other marine uses.

Alternatives E1 and E2 would reduce the number of vessels relative to a 10 percent or 

25 percent, respectively, reduction in line miles of deep-penetration, multi-client activities, but this 

reduction would not substantially change the risk of a small fuel spill. If a small diesel spill were to 

occur, it would have nominal impact on other marine uses because it would only prohibit full use of 

a small area by other marine users for a very limited amount of time.

4.12.6.3 Cumulative Impacts

A detailed impacts assessment under the cumulative scenario is provided in Alternative A 

(Chapter 4.12.2.3). The reduction of deep-penetration, multi-client activities by 10 percent 

(Alternative E1) or 25 percent (Alternative E2) would reduce the extent, severity, and timing of vessel 

traffic, stand-off distances, aircraft traffic and noise, seafloor disturbances, and accidental fuel spills; 

therefore, impacts would be incrementally decreased under Alternatives E1 and E2. Overall, the 

resultant cumulative impacts to other marine uses would result in nominal incremental increases 

under Alternative E.

4.12.7 Impacts – Alternative F (Alternative C Plus Area Closures)

The IPFs and impact significance criteria applied for Alternative F are the same as for 

Alternative A (Chapter 4.12.2). For the sake of brevity, those detailed analyses are incorporated for 

this analysis, and the following discussion outlines the effects of the additional mitigation measures 

included in Alternative F on other marine uses.
Gulf of Mexico G&G Activities Programmatic EIS 4-383

4.12.7.1 Impacts of Routine Activities

The additional mitigation measures under Alternative F would not change the extent, 

severity, or timing of aircraft traffic and noise and seafloor disturbance impacts as described under 

Alternative C; therefore, impacts to other marine uses would be unchanged under Alternative F and 

would range from no impact to nominal for other marine uses.

Alternative F would require area closures in the CPA Closure Area, EPA Closure Area, Dry 

Tortugas Closure Area, and Flower Gardens Closure Area for seismic airgun survey operations. 

Area closures would eliminate the impacts of vessel traffic and stand-off distances from seismic 

airgun surveys on other marine uses, as these surveys would not occur within the designated areas; 

however, impacts to the non-closure areas would still occur and there would not be a reduction in 

the overall survey activity as part of the proposed action; therefore, the overall impacts to other 

marine uses would remain as no impact to nominal. 

4.12.7.2 Impacts of an Accidental Fuel Spill

Under Alternative F, impacts of accidental collisions or fuel spills on other marine uses would 

be very similar to those analyzed for Alternative C in Chapter 4.12.4.2. The analysis concluded that 

mitigation measures, including planning and implementing stand-off distances, vessel-to-vessel 

communication, issuance of warnings to mariners, and a coastal seasonal restriction area would limit 

the likelihood of a vessel collision or another vessel becoming entangled in towed G&G equipment

and that a small spill at the sea surface would be unlikely to have any effect on other marine uses.

The risk of an accidental spill related to G&G activities would be lessened within the closure 

areas because G&G survey activities would be prohibited; however, vessels could still use the area 

for transit so the risk of an accidental spill would still exist. Additionally, the overall extent of survey 

activity within the GOM would not be reduced under Alternative F, and the overall risk, although low, 

of an accidental spill would remain despite certain areas being closed because spills from seismic 

survey vessels could occur in areas outside the closure areas. Also, spills from other vessels could 

occur within the closure areas. Therefore, a closure of areas under Alternative F would not 

substantially change the risk of a small fuel spill. Overall, the risk of an accidental fuel spill and the 

potential impacts on other marine uses would be the same as under Alternative C and would be 

nominal. 

4.12.7.3 Cumulative Impacts

The cumulative impact analysis identified nominal incremental increases in impacts from all 

IPFs under Alternative A. The cumulative scenario would remain unchanged for Alternative F, and 

the associated impacts would remain the same. Alternative F closure and restricted areas within the 

AOI would not appreciably change the cumulative impacts noted under Alternative A. While the area 

closures are effective in decreasing impacts, they will not result in a decrease in the overall activities 

and resultant impacts for the proposed action to the cumulative scenario. Overall, the resultant 
4-384 Description of the Affected Resources and Impact Analysis

cumulative impacts to other marine uses would result in nominal incremental increases under 

Alternative D.

4.12.8 Impacts – Alternative G (No New Activity Alternative)

The IPFs and impact significance criteria applied for Alternative G are the same as for 

Alternative A (Chapter 4.12.2).

4.12.8.1 Impacts of Routine Activities

As evaluated in Alternative A (Chapter 4.12.2.1), impacts on other marine uses were 

determined to range from no impact to nominal. If no new activity occurs under Alternative G, 

potential impacts to other marine uses would remain no impact or nominal impacts, and impacts 

would eventually decline to no impacts. 

4.12.8.2 Impacts of Accidental Events

Alternative G would not have the number of survey vessels involved to conduct G&G 

activities compared with Alternative A; however, there remains a potential for spills to occur within 

the AOI with current activity. If an accidental fuel spill occurs, it is anticipated that the spill size 

would be relatively small and the area of impact would be a small portion of the AOI. The type and 

severity of impacts to other marine uses would depend on the location of the event but are expected 

to be nominal because it would only prohibit full use of a small area by other marine users for a very 

limited amount of time.

4.12.8.3 Cumulative Impacts

Impact analyses presented in Chapters 4.12.8.1 and 4.12.8.2 determined that activities 

projected to occur under Alternative G would result in no impact and nominal impacts to other 

marine uses, depending on the IPF. The cease of activity for future G&G surveys requiring a 

permit/authorization from BOEM would not be adding an increase to the cumulative impacts 

because VSP and SWD are linked to current activity. Overall, the resultant cumulative impacts to 

other marine uses would result in nominal incremental increases under Alternative G. 

4.13 HUMAN RESOURCES AND LAND USE

4.13.1 Description of the Affected Environment

The onshore portion of the AOI extends along the GOM coastline from the southwestern tip 

of the Florida Keys to the southern coast of Texas. The area encompasses 133 counties/parishes in 

23 BOEM-designated Economic Impact Areas. The G&G activities offshore in the GOM have a 

corresponding impact on the human environment onshore, including land use and coastal 

infrastructure, environmental justice, demographics, and socioeconomic aspects of the communities 

along the Gulf Coast. Activities in the OCS are supported by onshore facilities, which can impact the 

human environment. Additional information on the affected environment can be found in 

Appendix E, Section 13. 
Gulf of Mexico G&G Activities Programmatic EIS 4-385

4.13.1.1 Land Use and Coastal Infrastructure

The coastal areas of the GOM are not homogenous in terms of physical characteristics or 

socioeconomic attributes; they are divided into counties and parishes, each with unique histories and 

characteristics. Major cities near the study area include Houston, Texas; Baton Rouge and New 

Orleans, Louisiana; Pascagoula, Mississippi; Mobile, Alabama; and Tampa, Florida. Land uses in 

the study area range from urban areas in and around the cities previously mentioned to rural 

agricultural areas. Coastal land uses range from large areas of recreational beaches, wetlands, and 

barrier islands to deepwater ports and oil and gas production infrastructure. In addition, residential, 

commercial, farming/ranching, and other industrial uses are scattered along the coast.

The energy industry has a long history of operating in the GOM and, as a result, coastal 

infrastructure has been built to accommodate and service this sector. The G&G activities have been 

conducted for years in the GOM; therefore, companies that provide goods and services to support 

G&G activities are numerous and well established. For example, companies that provide 

shipbuilding and repair services, ports, and equipment and material suppliers are all part of the 

coastal infrastructure (Table 4.13-2).

According to the OCS-Related Infrastructure Fact Book completed in 2011 (Dismukes, 

2011), 28 major shipbuilding yards are located along the GOM, with the majority of these yards 

being topside repair yards. The yards mostly are clustered between New Orleans, Louisiana, and 

Mobile, Alabama.

Numerous ports and ports facilities that could be used to support G&G activities on the OCS 

are located throughout the GOM region. Ports that support activities on the OCS typically fall into 

one of two categories: (1) smaller facilities that are privately owned and are designed and used to 

support energy development activities in the GOM; or (2) larger facilities that support a wide 

spectrum of maritime activities, including oil and gas exploration, as well as bulk container traffic and 

maritime transportation. The top 50 offshore support ports in the GOM identified in the OCS-Related 

Infrastructure Fact Book are primarily located around the New Orleans/Mobile area or in the Houston 

area (Dismukes, 2011).

The two primary ports that support G&G activities in the GOM are Port Fourchon in 

Lafourche Parish, Louisiana, and the Port of Galveston in Texas, according to G&G permit 

application forms submitted to BOEM. Port Fourchon is the largest port serving oil and gas 

production in the GOM. More than 250 companies utilize the port as a base of operation, and 

>90 percent of the GOM’s deepwater oil production is serviced by Port Fourchon (Greater Lafourche 

Port Commission, n.d.). The Port of Galveston serves cruise ships, cargo ships, research vessel, 

barges, lay barges, and rigs. In 2013, a total of 912 ship calls occurred in the port, including 

317 cargo ships, 85 research vessels, and 179 cruise ships. Pipe-laying vessels and drilling rigs 

accounted for 96 ship calls, while pipe-laying barges accounted for an additional 229 ship calls. 

Cargo barges accounted for six ship calls in 2013 (Port of Galveston, n.d.).
4-386 Description of the Affected Resources and Impact Analysis

4.13.1.2 Environmental Justice

Executive Order 12898 (“Federal Actions to Address Environmental Justice in Minority 

Populations and Low Income Populations”) was signed by President Clinton on February 11, 1994. 

This EO requires each Federal agency to identify and address, as appropriate, disproportionately 

high and adverse human health or environmental impacts of its programs, policies, and activities on 

minority and low-income populations, including Native American populations. The USEPA and the 

CEQ emphasize the importance of incorporating environmental justice review in the analyses 

conducted by Federal agencies under NEPA and of developing protective measures that avoid 

disproportionate environmental impacts on minority and low-income populations.

President Clinton issued EO 13045 (“Environmental Health Risks and Safety Risk to 

Children”) on April 21, 1997. This EO requires each Federal agency to “make it a high priority to 

identify and assess environmental health risks and safety risks that may disproportionately affect 

children and shall ensure that its policies, programs, activities, and standards address 

disproportionate risks to children.” The EO was issued because a growing body of scientific 

knowledge demonstrates that children may suffer disproportionately from environmental health and 

safety risks.

The CEQ has issued the following guidance to Federal agencies on the terms used in 

EO 12898:

• Low-Income Population: Low-income populations in an affected area should 

be identified using the annual statistical poverty thresholds from the U.S. Bureau 

of the Census.

• Minority: An individual who is a member of the following population groups: 

American Indian or Alaskan Native; Asian or Pacific Islander; Black, not of 

Hispanic origin; or Hispanic.

• Minority Population: Minority populations should be identified where (1) the 

minority population of the affected area exceeds 50 percent or (2) the minority 

population percentage of the affected area is meaningfully greater than the 

minority population percentage in the general population or other appropriate unit 

of geographic analysis.

• Children: Individuals under the age of 18.

Table 4.13-3 shows the percent of the population in geographic areas around Port Fourchon 

and the Port of Galveston that are considered minorities. Totals for the U.S. and for Louisiana and 

Texas are shown for comparison purposes. Port Fourchon is located within the Houma-Bayou 

Cane-Thibodaux MSA. The Port of Galveston is located in the Houston Sugar Land Baytown MSA. 

As shown in Table 4.13-3, the areas surrounding Port Fourchon have smaller percentages of 

minorities than Louisiana or the U.S. as a whole. In contrast, Galveston and the Houston-Sugar 

Land-Baytown MSA have greater percentages of racial minorities than Texas or the U.S. as a whole. 
Gulf of Mexico G&G Activities Programmatic EIS 4-387

The areas surrounding the Port of Galveston have smaller percentages of Hispanic or Latino 

populations than the statewide total but larger percentages than the national level (U.S. Census 

Bureau, 2012). For environmental justice purposes, Galveston and the Houston-Sugar 

Land-Baytown MSA are considered to have meaningfully greater minority populations.

Table 4.13-4 shows the low-income populations in the same geographic areas. As shown in 

the table, the Houma-Bayou Cane-Thibodaux MSA has a slightly greater percentage of residents 

defined as low income compared with the nationwide average and a smaller percentage than the 

total for Louisiana. In contrast, Lafourche Parish has a smaller percentage of residents defined as 

low income compared with State and national levels. During the same time period, 24.7 percent of 

all resident in the City of Galveston were considered low income compared with 18.1 percent in 

Texas and 15.7 percent in the U.S., making this a difference that was meaningfully greater for 

environmental justice purposes. The Houston-Sugar Land-Baytown MSA around the Port of 

Galveston had a smaller percentage of low-income residents than the State and Nation (U.S. 

Census Bureau, 2012).

4.13.1.3 Demographics

The population living in the coastal communities along the GOM has experienced a dramatic 

increase over the last 40 years. As of 2010, approximately 24.2 million people lived in communities 

influenced by activities in the GOM, more than double the number of individuals who lived in the 

same communities 40 years ago. In 2010, approximately 7.8 percent of the total population of the 

U.S. lived in communities along the GOM (U.S. Census Bureau, 2012; USDOC, NOAA, n.d.). 

However, this increase in population is not uniformly distributed throughout the region.

Because the GOM region is so diverse, some areas have experienced rapid growth while 

other areas have not kept up with national growth rates. As shown in Table 4.13-1, Florida has 

experienced the most rapid population growth in the region, with its total and Gulf Coast populations 

nearly doubling between 1970 and 1990. From 1990 to 2010, an additional 3.1 million people 

moved to the coastal areas of the GOM in Florida alone.

In contrast, population growth rates in the coastal areas of Alabama and Louisiana have not 

kept up with national growth rates. Between 1970 and 1990 and from 1990 to 2010, the U.S. 

experienced population growth rates of 22.4 and 24.1 percent, respectively (U.S. Census Bureau, 

2002, 2012), whereas populations in the coastal areas of Louisiana increased by 18.0 and 

7.9 percent, respectively, during the two time periods, and populations in the Alabama coastal areas 

increased by only 20.5 and 19.45 percent, respectively (Table 4.13-1).

Total population around Port Fourchon and the Port of Galveston is shown in Table 4.13-3. 

There were 208,178 residents living in the Houma-Bayou Cane-Thibodaux MSA and 

96,318 residents living in Lafourche Parish in 2010. The area surrounding the Port of Galveston is 

much more populous. In 2010, there were >5.9 million people living in the Houston-Sugar LandBaytown MSA. More than 47,000 residents lived in the City of Galveston (Table 4.13-3).
4-388 Description of the Affected Resources and Impact Analysis

4.13.1.4 Socioeconomics

The communities along the GOM are a diverse group that range from the large urban areas 

like the Houston and New Orleans, which have well-integrated economies, to the smaller rural areas 

that are more dependent on a few industries.

The GOM has a great economic impact on the local and regional economies of coastal 

communities from Florida to Texas. In total, approximately 25,100 business enterprises generated 

nearly $161.2 billion in local GDP and $33.9 billion in wages and salaries, supporting nearly 

581,100 jobs in 2012 as a result of activities associated with the GOM. Offshore mineral extraction 

was the largest sector in terms of GDP and wages, accounting for 81.3 percent of the total economic 

activity and 57.5 percent of the total wages and salaries associated with the GOM. In contrast, the 

tourism and recreation sector accounted for >51.4 percent of all jobs associated with the GOM, but it 

generated only 16.7 percent of the total wages and salaries and only 7.4 percent of the local GDP 

tied to activities in the GOM. Marine transportation and shipbuilding were large employment sectors 

as well. The marine construction sector and the living resources sector (e.g., commercial fishing) 

generated the smallest portion of GOM-related employment in 2010 (Table 4.13-2) (USDOC, NOAA, 

n.d.).

The energy industry has a long history in the Gulf Coast States; the industry is mature and it 

is fully integrated into all aspects of the local and regional communities. Numerous companies offer 

G&G services in the GOM. According to an economic study on the oil services contract industry in 

the GOM region completed for BOEM in June 2011, the G&G services industry employs between 

5,870 and 6,128 workers in the GOM region and contributes at least $2.94 billion to the regional 

economy (Eastern Research Group, Inc., 2011).

A total of 79 companies were identified as providing G&G prospecting services in the GOM 

(Eastern Research Group, Inc., 2011). The firms ranged from large publicly owned multinational 

companies to small privately owned companies. Employment at the publicly owned companies 

ranged from 80,000 workers at Schlumberger to only 36 workers at GETECH, Inc. Some of these 

companies perform services in addition to G&G prospecting services; therefore, it cannot be 

assumed that all of their employees work in the G&G prospecting field. The majority of the privately 

held companies employed <25 workers. There were, however, a few notable exceptions, including 

Fairfield Industries that employed 400 workers, Paradigm that employed 950 workers, and Willis 

Group that employed 286 workers, which were large privately owned enterprises (Eastern Research 

Group, Inc., 2011).

Much of the onshore portion of the G&G industry is located in Harris County, Texas, the 

county that encompasses much of greater Houston. Approximately 68 percent of all firms offering 

G&G services in the GOM are located in Harris County, 84 percent of the total employees working in 

the G&G industry are assigned to offices in Harris County, and 95 percent of the total revenues 

earned in the industry are attributed to companies in Harris County. Other areas with large 
Gulf of Mexico G&G Activities Programmatic EIS 4-389

concentrations of personnel engaged in G&G activities included Lafayette Parish in Louisiana and 

Fort Bend County in Texas (Eastern Research Group, Inc., 2011).

In addition to the oil and gas industry, G&G services and activities in the GOM are utilized by 

a wide variety of scientific, research, educational, governmental, and commercial enterprises. 

Studies into geomorphology, cartology, and climate change; cultural resource surveys; fisheries 

research; military and USCG activities; and BOEM’s Marine Minerals Program all require G&G 

services. As a result, G&G services support these multimillion dollar industries that employ 

thousands of workers throughout the Gulf Coast.

4.13.2 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

Under Alternative A, BOEM would continue to permit/authorize G&G activities at current 

projected levels with the implementation of standard mitigation measures applied through lease 

stipulations, issued permits and authorizations, NTLs, and best management practices. No 

noticeable impact is expected to occur on human resources and land use in the Gulf Coast area as a 

result of this alternative. The G&G activities are projected to remain at current levels; therefore, this 

alternative is not expected to impact the size or structure of the existing G&G industry. In addition, 

employment and earnings in this industry are not expected to change; therefore, no secondary 

impacts to demographics, socioeconomics, environmental justice, or land use are expected to occur 

under this alternative.

4.13.3 Impacts – Alternative B (Settlement Agreement Alternative)

Under Alternative B, BOEM would continue to authorize the current level of G&G activity 

through the use of site-specific NEPA evaluations, lease stipulations, NTLs, best management 

practices, and COAs because the Settlement for Civil Action No. 2-cv-01882 dated June 25, 2013 

(Appendix C), was issued. Similar to Alternative A, no noticeable impact is expected to occur on 

human resources and land use in the Gulf Coast area as a result of this alternative. The G&G 

activities are projected to remain at current levels; therefore, this alternative is not expected to 

impact the size or structure of the existing G&G industry. In addition, employment and earnings in 

this industry are not expected to change; therefore, no secondary impacts to demographics, 

socioeconomics, environmental justice, or land use are expected to occur under this alternative.

4.13.4 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional 

Mitigation Measures)

Under Alternative C, BOEM would continue to authorize the current level of G&G activity and 

include mitigation measures, monitoring, reporting, survey protocols, and guidance that are currently 

in place (Alternative A), as well as additional mitigation measures for survey protocols for airgun and 

HRG surveys. Similar to the previous alternatives discussed, no noticeable impact is expected to 

occur on human resources and land use in the Gulf Coast area as a result of this alternative. The 

G&G activities are projected to remain at current levels; therefore, this alternative is not expected to 

impact the size or structure of the existing G&G industry. In addition, employment and earnings in 
4-390 Description of the Affected Resources and Impact Analysis

this industry are not expected to change; therefore, no secondary impacts to demographics, 

socioeconomics, environmental justice, or land use are expected to occur under this alternative.

4.13.5 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

Under Alternative D, BOEM would continue to authorize the current level of G&G activity and 

would include mitigation measures, monitoring, reporting, survey protocols, and guidance that are 

currently in place (Alternative A), as well as additional mitigation measures for survey protocols for 

airgun and HRG surveys (Alternative C). Alternative D would also include the addition of shutdowns 

for all marine mammals within the exclusion zone except bow-riding dolphins. Similar to the 

previous alternatives discussed, no noticeable impact is expected to occur to human resources and 

land use in the Gulf Coast area as a result of this alternative. The G&G activities are projected to 

remain at current levels; therefore, this alternative is not expected to impact the size or structure of 

the existing G&G industry. In addition, employment and earnings in this industry are not expected to 

change; therefore, no secondary impacts to demographics, socioeconomics, environmental justice, 

or land use are expected to occur under this alternative.

4.13.6 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

This chapter discusses the potential impacts associated with implementation of Alternative E 

on human resources and land use in affected communities along the Gulf Coast. Under 

Alternative E, all mitigation measures and protocols described in Alternatives A and C would be 

followed and G&G activities would occur at a reduced level. Total reduction of deep-penetration, 

multi-client activities (in line miles) is expected to decline by between 10 percent (Alternative E1) and 

25 percent (Alternative E2) from the estimated levels in a calendar year.

Potential impacts on human resources and land use associated with the implementation of 

this alternative would be caused directly by the reduction in G&G activity and the resulting decline in 

economic activity, not from the IPFs discussed in Chapter 4.1.3. Therefore, the IPFs will not be 

analyzed separately in this chapter. 

The reduction of G&G activities by 10 to 25 percent, as proposed by Alternative E, would 

lead to a corresponding reduction in the size of the G&G industry in the Gulf Coast region. The G&G 

industry in the GOM employs approximately 6,000 workers and generates approximately 

$2.94 billion in regional economic output (Eastern Research Group, Inc., 2011). Assuming 

employment and output are proportional to the amount of G&G activity occurring in the GOM, a 

decline in G&G activity by 10 to 25 percent would likely result in the direct loss of approximately 

600 to 1,500 jobs within the industry. In addition, direct economic output in the region would be 

expected to decline by approximately $294 million to $735 million a year.

Additional indirect and induced economic impacts would also occur as a result of this action. 

As the size of the G&G industry contracts, workers in the industry would have less income to spend 

in the regional economy. At the same time, suppliers to the G&G industry would see the overall 

demand for their goods and services decrease. Revenues at local retail outlets and service 
Gulf of Mexico G&G Activities Programmatic EIS 4-391

providers would decline. As these local merchants respond to this decrease in demand, they may, 

in turn, decrease employment at their operations and/or purchase fewer goods and services from 

their providers. These newly displaced workers and suppliers would also have a smaller amount of 

income to spend, thus “multiplying” the negative economic impacts of the exogenous change in G&G 

activity.

The bulk of the negative socioeconomic impacts would likely occur in areas that currently 

have the largest concentration of G&G firms; therefore, Harris County, Texas, would experience the 

majority of these negative socioeconomic impacts. Likewise, Fort Bend County, Texas, and 

Lafayette Parish, Louisiana, would also experience a loss of employment and economic impact if 

G&G services in the GOM were curtailed by 10 to 25 percent.

On a regional scale, these impacts are expected to be minor. Given the relative size of the 

communities where the majority of G&G industry is located, any loss of employment associated with 

Alternative E is expected to have a relatively minor impact on the regional economy. 

Unemployment rates in the region would be expected to remain relatively constant under this 

alternative. In 2014 each of the three communities had average labor forces that ranged in size from 

approximately 122,000 workers in Lafayette Parish to nearly 2.3 million workers in Harris County. In

addition, these areas experienced low unemployment, with average unemployment rates of 

4.9 percent or less (U.S. Dept. of Labor, Bureau of Labor Statistics, 2015a,b). Given the relative 

size of the regional labor market and the existing low unemployment rates, the majority of workers 

that are expected be displaced from the G&G industry under Alternative E would likely be able to 

find employment in other industries in the region.

All non-BOEM-regulated surveys for scientific research, all BOEM activities not covered by 

this program (i.e., geophysical surveys for archeological and/or benthic resources), and all surveys 

that occur in State waters would not be affected by the proposed reduction in activity under 

Alternative E and would continue as normal. However, implementation of Alternative E could also 

impact on the OCS Program. The proposed reduction in G&G survey activities under Alternative E 

has the potential to directly affect the leasing program. Potential bidders depend on new data 

acquisition for bid preparation prior to lease sales, and this could either prevent certain new bids or 

introduce an element of uncertainty in bid amounts. Thus, this could deter some drilling and 

decrease overall production in the GOM. Immediate effects would result from the inability of the oil 

and gas industry to collect as much G&G data as they could under the proposed action, an inability 

of BOEM to project accurate resource estimates, and additional costs could be incurred by the oil 

and gas companies as more uncertainty would be introduced into the exploration process. Some 

areas in the GOM that have not undergone significant G&G surveys could become less desirable for 

oil and gas leasing purposes and may not be developed until the price of oil and gas increased to a 

level where these areas would become financially and economically viable again. However, these 

impacts are expected to be nominal to minor because of the small scales of the lost activities 

relative the overall economies of the area and because firms will likely be able to prioritize (and 

potentially adjust) their G&G practices. In addition, the substantial declines in oil and gas prices 
4-392 Description of the Affected Resources and Impact Analysis

since mid-2014 will likely curtail oil and gas exploration activities, implying that G&G activities may 

decline even in the absence of Alternative E.

Overall, nominal to minor impacts are expected to occur on land use and coastal 

infrastructure, environmental justice, demographics, and socioeconomics under Alternative E.

4.13.7 Impacts – Alternative F (Alternative C Plus Area Closures)

Under Alternative F, BOEM would continue to authorize the current level of G&G activity and 

include mitigation measures, monitoring, reporting, survey protocols, and guidance currently in place 

(Alternative A), as well as additional mitigation measures for survey protocols for airgun and HRG 

surveys (Alternative C) with the addition of four area closures (except for non-airgun HRG surveys 

operating at frequencies >200 kHz) to provide additional protection for certain cetacean species and 

other resources. Similar to Alternatives A through D, no noticeable impact is expected to occur on 

human resources and land use in the Gulf Coast area as a result of this alternative. The G&G 

activities are projected to remain at current levels; therefore, this alternative is not expected to 

impact the size or structure of the existing G&G industry. In addition, employment and earnings in 

this industry are not expected to change; therefore, no secondary impacts to demographics, 

socioeconomics, environmental justice, or land use are expected to occur under this alternative.

4.13.8 Impacts – Alternative G (No New Activity Alternative)

Under Alternative G, no new G&G activities associated with the development of oil and gas 

reserves, renewable energy, or marine materials would be authorized to occur within the AOI during 

the time period covered by this Programmatic EIS. Other G&G survey activities would be unaffected 

by this ban, including any that occur within State waters, those that are for scientific studies and 

regulated by other Federal agencies, and any BOEM non-regulated G&G activities (i.e., geophysical 

surveys for archeological and benthic resources). In the short term, G&G activities already approved 

would be allowed to continue for the duration of their authorized permit/authorization; however, no 

additional permits/authorizations would be approved. In the long term, all BOEM-regulated G&G 

activities in the GOM would cease upon expiration of the permit/authorization.

Implementation of Alternative G would have a major negative economic impact on the G&G 

industry. According to estimates made by the Eastern Research Group, Inc., the G&G industry is a 

$2.94 billion industry that employs an estimated 5,870 to 6,128 workers in the Gulf Coast region 

(Eastern Research Group, Inc., 2011). Restricting all G&G activities associated with the 

development of oil and gas reserves, renewable energy, and marine minerals as planned under 

Alternative G would result in widespread layoffs and business closures within the industry. While 

some economic activity and employment in the G&G industry would continue as work continued on 

survey activities not included in the proposed action and through the reprocessing of existing data, 

the total size of the G&G industry in the GOM would greatly contract.

Similar to the impacts described for Alternative E, negative indirect and induced economic 

impacts would also occur. As the size of the G&G industry contracts, workers in the industry would 
Gulf of Mexico G&G Activities Programmatic EIS 4-393

have less income to spend in the regional economy. At the same time suppliers to the G&G industry 

would see the overall demand for their goods and services decrease. Local merchants could 

respond to this decrease in demand by decreasing employment at their operations and/or 

purchasing fewer goods and services from their providers, resulting in minor impacts for land use 

and infrastructure. Displaced workers and these suppliers would have a smaller amount of income 

to spend, thus “multiplying” the negative economic impacts of the change in G&G activity.

As described in Alternative E, the majority of the direct socioeconomic impacts associated 

with the cessation of all G&G activities under Alternative G would be concentrated in Harris County 

and Fort Bend County, Texas, and in Lafayette Parish, Louisiana. While these regions currently 

have large workforces and have been experiencing low unemployment rates, the loss of the majority 

of the G&G industry would have a noticeable impact on unemployment rates and employee earnings 

in these communities, resulting in an overall minor impact to the socioeconomics, environmental 

justice, and demographics in the region.

The cessation of G&G activities under Alternative G would also have a noticeable impact on 

the oil and gas industry throughout the Gulf Coast region. Immediate effects would result from the 

inability of the oil and gas industry to collect new G&G data once existing permits/leases expire. All 

proposed new oil and gas drilling in the AOI would become dependent on existing geophysical data. 

Additional costs would be incurred by the oil and gas companies as more uncertainty would be 

introduced into the exploration process. Areas in the GOM that have not undergone sufficient G&G 

surveys prior to cessation would become less desirable for oil and gas leasing purposes and may 

not be developed until the price of oil and gas increased to a level where these areas would become 

financially and economically viable again. The production of oil and gas in the GOM would likely 

decline in the near term. The U.S. Government’s lease revenues and oil/gas royalties from the GOM 

would also decline as GOM oil and gas leases become less valuable and as less oil and gas is 

produced.

In addition, the design and placement of new oil rigs and oil platforms would become less 

certain as site-specific G&G surveys would not be available to guide the placement of new rigs and 

platforms, making the interference of geohazards a greater possibility and the construction of these 

structures more risky. Additional engineering and construction costs would likely be incurred as 

“over engineering” and would be required to compensate for the lack of geohazard information. The 

pace of development of renewable energy resources in the GOM would also likely be slow. The lack 

of current G&G data would increase the costs associated with developing offshore wind resources 

and other renewable energy sources in the GOM, making these projects less financially attractive.

Finally, the costs associated with various Gulf Coast State coastal restoration projects, 

beach nourishment projects, and levee reconstruction projects that utilize marine minerals from the 

GOM could be increased. Currently, there is no fee for the use of OCS sediment resources by Gulf 

Coast State and local governments; however, the cost of the associated NEPA analyses, 

consultations, and supporting studies rests with BOEM. BOEM’s Marine Minerals Program, thus far, 
4-394 Description of the Affected Resources and Impact Analysis

has served seven states and restored 269 mi (433 km) of coastline, which indirectly supports the 

State tourism industry of those states.

Under this alternative, all G&G activities for marine minerals would cease, thereby making 

locating and securing significant quantities of sedimentary resources more difficult and costly. State 

and local governments would be limited to utilizing only limited, known resources or would be 

required to acquire these marine mineral resources from other sources. With all these resultant 

impacts, there would be a moderate cumulative incremental increase in impacts to human 

resources and land use from Alternative G.

4.13.9 Economic Factors

The communities along the GOM are a diverse group that range from the large urban areas 

like the Houston and New Orleans, which have well-integrated economies, to the smaller rural areas 

that are more dependent on a few industries.

The GOM has a great economic impact on the local and regional economies of coastal 

communities from Florida to Texas. In total, approximately 25,100 business enterprises generated 

nearly $161.2 billion in local gross domestic product and $33.9 billion in wages and salaries, 

supporting nearly 581,100 jobs in 2012 as a result of activities associated with the GOM. Offshore 

mineral extraction was the largest sector in terms of gross domestic product and wages, accounting 

for 81.3 percent of the total economic activity and 57.5 percent of the total wages and salaries 

associated with the GOM. In contrast, the tourism and recreation sector accounted for 

>51.4 percent of all jobs associated with the GOM, but it generated only 16.7 percent of the total 

wages and salaries and only 7.4 percent of the local gross domestic product tied to activities in the 

GOM. Marine transportation and shipbuilding were large employment sectors as well. The marine 

construction sector and the living resources sector (e.g., commercial fishing) generated the smallest 

portion of GOM-related employment in 2010 (Table 4.13-2) (USDOC, NOAA, n.d.-b).

The energy industry has a long history in the Gulf Coast States; the industry is mature and it 

is fully integrated into all aspects of the local and regional communities. The offshore energy 

industry in the GOM extracts oil, natural gas, and natural gas liquids, which are then processed and 

transported for use in various activities, including transportation, electricity generation, space 

heating, and chemical manufacturing. Extraction of oil, natural gas, and natural gas liquids entails 

capital and operating costs on various processes, including G&G surveying, drilling, platform 

fabrication, shipbuilding, and various support services. Spending on these equipment, facilities, and 

processes supports businesses further along supply chains and supports spending by workers. 

Quest Offshore Resources, Inc. (2011) provides an overview of the spending impacts of the offshore 

oil and gas industry in the GOM. The largest concentrations of the offshore energy industry are in 

coastal Texas and Louisiana. The offshore energy industry has been adapting to recent declines in 

energy prices. Lower energy prices have caused slowdowns in offshore drilling activities 

(Beaubouef, 2015) and rig construction (Odell, 2015).
Gulf of Mexico G&G Activities Programmatic EIS 4-395

Numerous companies offer G&G services in the GOM. According to an economic study on 

the oil services contract industry in the GOM region completed for BOEM in June 2011, the G&G 

services industry employs between 5,870 and 6,128 workers in the GOM region and contributes at 

least $2.94 billion to the regional economy (Eastern Research Group, Inc., 2011). A total of 

79 companies were identified as providing G&G prospecting services in the GOM (Eastern Research 

Group, Inc., 2011). The firms ranged from large publicly owned multinational companies to small 

privately owned companies. Employment at the publicly owned companies ranged from 

80,000 workers at Schlumberger to only 36 workers at GETECH, Inc. Some of these companies 

perform services in addition to G&G prospecting services; therefore, it cannot be assumed that all of 

their employees work in the G&G prospecting field. The majority of the privately held companies 

employed <25 workers. There were, however, a few notable exceptions, including Fairfield 

Industries that employed 400 workers, Paradigm that employed 950 workers, and Willis Group that 

employed 286 workers, which were large privately owned enterprises (Eastern Research Group, 

Inc., 2011). Along with the oil and gas industry, the G&G industry has been experiencing a 

noticeable slowdown in activities in 2016 compared with prior years.

Much of the onshore portion of the G&G industry is located in Harris County, Texas, the 

county that encompasses much of greater Houston. Approximately 68 percent of all firms offering 

G&G services in the GOM are located in Harris County, 84 percent of the total employees working in 

the G&G industry are assigned to offices in Harris County, and 95 percent of the total revenues 

earned in the industry are attributed to companies in Harris County. Other areas with large

concentrations of personnel engaged in G&G activities included Lafayette Parish in Louisiana and 

Fort Bend County in Texas (Eastern Research Group, Inc., 2011).

In addition to the oil and gas industry, G&G services and activities in the GOM are utilized by 

a wide variety of scientific, research, educational, governmental, and commercial enterprises. 

Studies into geomorphology, cartology, and climate change; cultural resource surveys; fisheries 

research; military and USCG activities; and BOEM’s Marine Minerals Program all require G&G 

services. As a result, G&G services support these multimillion dollar industries that employ 

thousands of workers throughout the Gulf Coast.

The cost analysis for this Programmatic EIS focused only on additional expenditures for 

operating costs from the proposed mitigations for Alternatives A-F; therefore, this cost analysis 

represents a part of the whole economic analysis. This is most evident for Alternatives E and F 

where the cost increase to industry would only represent a small part of the total economic impact. 

While the cost of the mitigation measures proposed for Alternatives E and F (such as expanded 

PSO and PAM programs, etc.) that would add additional operational cost are addressed in this 

analysis, those alternatives also have proposals such as the 10 and 25 percent reduction in line 

miles in Alterative E and the closure areas and associated buffer proposed in Alterative F, which 

were addressed qualitatively. Therefore, the following economic analyses consider the additional 

operating costs to be incurred, as well as the larger ranging effects to industry, the local economy, 

and the supply chains from a reduction in activity and closure areas. The analysis for each 

alternative and the associated impact conclusion were developed using the best available, 
4-396 Description of the Affected Resources and Impact Analysis

scientifically credible information and generally accepted scientific methodologies. Nonetheless, a 

“Regulatory Impact Analysis” will be conducted as part of the requirements for the MMPA 

Rulemaking that will further analyze the economic impacts.

Table 4.13.9-1 represents the incremental cost and the percent cost change per survey for 

Alternatives B-F that would be incurred over the Alternative A pre-settlement mitigation measures 

identified in Chapter 2.3.2 (“Mitigation Measures”) and detailed in Appendix B, Section 1, for 

Alternatives A-F. Alternative A was used as the baseline for the cost analysis to be able to more 

fully understand the percent cost increase to industry for Alternatives B-F, i.e., the percent cost 

increase that would be incurred beyond historic requirements, prior to the 2013 and 2015 settlement 

agreements..

Table 4.13.9-2 represents the total annual survey incremental cost for Alternatives A-F that 

would be incurred based on the forecasted annual numbers of surveys (Table 3.2-1) and survey 

incremental cost (Table 4.13.9-1). The information is presented annually but it could be multiplied 

out by 10 for a total, i.e., the total cost to be incurred by industry.

Table 4.13.9-3 represents the percent reduced efficiency per survey that could result for 

Alternatives A-F. The percent reduced efficiency is based on survey delays due to the proposed 

mitigations. BOEM analyzed the number of days it took, including delays as a result of shutdowns 

due to the proposed mitigation over the number of days it would have taken without those additional 

shutdowns. Alternative A was used as the baseline for the loss of efficiency analysis to be able to 

more fully understand the reduced efficiency for Alternatives B-F, prior to the 2013 and 2015 

settlement agreements. A 10 percent loss of operational efficiency was automatically assumed for 

Alternative A as part of the pre-settlement conditions.

The following chapters utilize the above information to estimate the socioeconomic impacts 

of each alternative.

4.13.9.1 Impacts – Alternative A (Pre-Settlement [June 2013] Alternative)

Under Alternative A, BOEM would continue to permit/authorize G&G activities at current 

projected levels with the implementation of standard mitigation measures applied through lease 

stipulations, issued permits and authorizations, NTLs, and best management practices. 

Alternative A includes no newly proposed mitigation measures since the Settlement Agreement and 

would result in no increased cost or loss in operational efficiency (Tables 4.13.9-1 through 

4.13.9-3). No noticeable impact is expected to occur on human resources and land use in the Gulf 

Coast area as a result of this alternative. The G&G activities are projected to remain at current 

levels; therefore, this alternative is not expected to impact the size or structure of the existing G&G 

industry. In addition, employment and earnings in this industry are not expected to change; 

therefore, no secondary impacts to demographics, socioeconomics, environmental justice, or land 

use are expected to occur under this alternative.
Gulf of Mexico G&G Activities Programmatic EIS 4-397

4.13.9.2 Impacts – Alternative B (Settlement Agreement Alternative)

Alternative B could cause socioeconomic impacts through various means, e.g., by 

increasing the costs of G&G activities over pre-settlement levels, by preventing a certain survey from 

occurring, by delaying G&G activity, or by causing G&G activities to glean less information than 

would have been obtained under pre-settlement conditions. More new oil and gas drilling in the AOI 

would become dependent on existing geophysical data. Additional costs would be incurred by the 

oil and gas companies as more uncertainty and inefficiencies would be introduced into the 

exploration process. Any increased costs would be borne by either the seismic surveying company 

or by the exploration and production company, depending on the extent to which the increased costs 

will result in increased prices for seismic services. All else being equal, the increased costs would 

lead to decreased profits for decreased profits for these companies, although the increased costs 

would also serve as income to the providers of mitigation-related services. Depending on the 

amount of lost business, G&G companies could move to other areas or go out of business. If a 

seismic survey were to be curtailed (or cancelled altogether), the associated companies and 

employees in the oil and gas supply chain would lose the associated income, and the overall 

economy would not receive the benefit of any lost oil and gas production. For example, disruptions 

to oil and gas production could increase energy prices and could lead to broader job losses. The 

majority of the associated socioeconomic impacts would occur in coastal Texas and Louisiana, 

although some impacts (such as lost profits or lost oil and gas production) could be felt elsewhere. 

These impacts would also depend on the state of the oil and gas industry, as well as the overall 

economy. In 2016, the overall United States’ economy is reasonably healthy, but the oil and gas 

industry is struggling with low energy prices (which is having a disproportionate impact on the Texas 

and Louisiana economies). Any loss in G&G activities could also negatively impact renewable 

energy or marine mineral development. However, there is not expected to be substantial renewable 

energy development in the GOM in the near future. The immediate effects of disruptions to marine 

mineral development would be small since most mineral extractions (currently sand) in the GOM 

have occurred in State waters for beach restoration and public works projects. However, as these 

sources become depleted, the identification and exploitation of new sand sources in Federal waters 

will become more important.

Alternative B would not directly curtail G&G activities. However, components of 

Alternative B, such as the minimum separation distance between seismic airguns, could increase 

costs by approximately 10 to 20 percent over pre-settlement levels (Tables 4.13.9-1 and 4.13.9-2). 

The minimum separation distance between surveys and the expanded PAM Program requirements 

could reduce operational efficiencies by up to 17 percent due to increased shutdowns in G&G data 

gathering (Table 4.13.9-3). This could harm companies in the G&G industry, and it could spread 

further if the costs were passed on to customers or if the resultant inefficiencies limited oil and gas 

exploration activities. The socioeconomic impacts of Alternative B are expected to be minor to 

moderate depending on the extent of these increased costs and inefficiencies.
4-398 Description of the Affected Resources and Impact Analysis

4.13.9.3 Impacts – Alternative C (Proposed Action – Alternative A Plus Additional Mitigation 

Measures)

Alternative C could cause socioeconomic impacts through various means, e.g., by increasing 

the costs of G&G activities over pre-settlement levels, by preventing a certain survey from occurring, 

by delaying G&G activity, or by causing G&G activities to glean less information than would have 

been obtained under pre-settlement conditions. More new oil and gas drilling in the AOI would 

become dependent on existing geophysical data. Additional costs would be incurred by the oil and 

gas companies as more uncertainty and inefficiencies would be introduced into the exploration 

process. Any increased costs would be borne by either the seismic surveying company or by the 

exploration and production company, depending on the extent to which the increased costs will 

result in increased prices for seismic services. All else being equal, the increased costs would lead 

to decreased profits for decreased profits for these companies, although the increased costs would 

also serve as income to the providers of mitigation-related services. Depending on the amount of 

lost business, G&G companies could move to other areas or go out of business. If a seismic survey 

were to be curtailed (or cancelled altogether), the associated companies and employees in the oil 

and gas supply chain would lose the associated income, and the overall economy would not receive 

the benefit of any lost oil and gas production. For example, disruptions to oil and gas production 

could increase energy prices and could lead to broader job losses. The majority of the associated 

socioeconomic impacts would occur in coastal Texas and Louisiana, although some impacts (such 

as lost profits or lost oil and gas production) could be felt elsewhere. These impacts would also 

depend on the state of the oil and gas industry, as well as the overall economy. In 2016, the overall 

United States economy is reasonably healthy, but the oil and gas industry is struggling with low 

energy prices (which is having a disproportionate impact on the Texas and Louisiana economies). 

Any loss in G&G activities could also negatively impact renewable energy or marine mineral 

development. However, there is not expected to be substantial renewable energy development in 

the GOM in the near future. The immediate effects of disruptions to marine mineral development 

would be small since most mineral extractions (currently sand) in the GOM have occurred in State 

waters for beach restoration and public works projects. However, as these sources become 

depleted, the identification and exploitation of new sand sources in Federal waters will become more 

important.

The mitigation measures for Alternative C would increase costs by up to 10 percent over 

pre-settlement levels (Tables 4.13.9-1 and 4.13.9-2). In addition, the expanded PSO and PAM 

Program requirements and the seasonal restrictions could reduce operational efficiencies by up to 

7 percent due to increased shutdowns in G&G data gathering (Table 4.13.9-3) and could cause 

certain surveys to not occur at all. However, most surveys could likely occur during other time 

periods, lessening the socioeconomic impacts. Therefore, the socioeconomic impacts of Alternative 

C are expected to be minor. 

4.13.9.4 Impacts – Alternative D (Alternative C Plus Marine Mammal Shutdowns)

Alternative D could cause socioeconomic impacts through various means, e.g., by increasing 

the costs of G&G activities over pre-settlement levels, by preventing a certain survey from occurring, 
Gulf of Mexico G&G Activities Programmatic EIS 4-399

by delaying G&G activity, or by causing G&G activities to glean less information than would have 

been obtained under pre-settlement conditions. More new oil and gas drilling in the AOI would 

become dependent on existing geophysical data. Additional costs would be incurred by the oil and 

gas companies as more uncertainty and inefficiencies would be introduced into the exploration 

process. Any increased costs would be borne by either the seismic surveying company or by the 

exploration and production company, depending on the extent to which the increased costs will 

result in increased prices for seismic services. All else being equal, the increased costs would lead 

to decreased profits for decreased profits for these companies, although the increased costs would 

also serve as income to the providers of mitigation-related services. Depending on the amount of 

lost business, G&G companies could move to other areas or go out of business. If a seismic survey 

were to be curtailed (or cancelled altogether), the associated companies and employees in the oil 

and gas supply chain would lose the associated income, and the overall economy would not receive 

the benefit of any lost oil and gas production. For example, disruptions to oil and gas production 

could increase energy prices and could lead to broader job losses. The majority of the associated 

socioeconomic impacts would occur in coastal Texas and Louisiana, although some impacts (such 

as lost profits or lost oil and gas production) could be felt elsewhere. These impacts would also 

depend on the state of the oil and gas industry, as well as the overall economy. In 2016, the overall 

United States economy is reasonably healthy, but the oil and gas industry is struggling with low 

energy prices (which is having a disproportionate impact on the Texas and Louisiana economies). 

Any loss in G&G activities could also negatively impact renewable energy or marine mineral 

development. However, there is not expected to be substantial renewable energy development in 

the GOM in the near future. The immediate effects of disruptions to marine mineral development 

would be small since most mineral extractions (currently sand) in the GOM have occurred in State 

waters for beach restoration and public works projects. However, as these sources become 

depleted, the identification and exploitation of new sand sources in Federal waters will become more 

important.

The mitigation measures for Alternative D would increase costs by up to 16 percent over 

pre-settlement levels (Tables 4.13.9-1 and 4.13.9-2). In addition, the seasonal restrictions and the 

additional marine mammals to monitor added under the expanded PAM Program would likely reduce 

operational efficiencies by up to 14 percent due to increased shutdowns in G&G data gathering 

(Table 4.13.9-3) and could cause certain surveys to not occur at all. However, most surveys could 

likely occur during other time periods, lessening the socioeconomic impacts. Refer to the general 

discussion above regarding the socioeconomic impacts of the alternatives. Overall, the 

socioeconomic impacts of Alternative D are expected to be minor to moderate. 

4.13.9.5 Impacts – Alternative E (Alternative C at Reduced Activity Levels)

Alternative E could cause socioeconomic impacts through various means, e.g., by increasing 

the costs of G&G activities over pre-settlement levels, by preventing a certain survey from occurring, 

by delaying G&G activity, or by causing G&G activities to glean less information than would have 

been obtained under pre-settlement conditions. More new oil and gas drilling in the AOI would 

become dependent on existing geophysical data. Additional costs would be incurred by the oil and 
4-400 Description of the Affected Resources and Impact Analysis

gas companies as more uncertainty and inefficiencies would be introduced into the exploration 

process. Any increased costs would be borne by either the seismic surveying company or by the 

exploration and production company, depending on the extent to which the increased costs will 

result in increased prices for seismic services. All else being equal, the increased costs would lead 

to decreased profits for decreased profits for these companies, although the increased costs would 

also serve as income to the providers of mitigation-related services. Depending on the amount of 

lost business, G&G companies could move to other areas or go out of business. If a seismic survey 

were to be curtailed (or cancelled altogether), the associated companies and employees in the oil 

and gas supply chain would lose the associated income, and the overall economy would not receive 

the benefit of any lost oil and gas production. For example, disruptions to oil and gas production 

could increase energy prices and could lead to broader job losses. The majority of the associated 

socioeconomic impacts would occur in coastal Texas and Louisiana, although some impacts (such 

as lost profits or lost oil and gas production) could be felt elsewhere. These impacts would also 

depend on the state of the oil and gas industry, as well as the overall economy. In 2016, the overall 

United States economy is reasonably healthy, but the oil and gas industry is struggling with low 

energy prices (which is having a disproportionate impact on the Texas and Louisiana economies). 

Any loss in G&G activities could also negatively impact renewable energy or marine mineral 

development. However, there is not expected to be substantial renewable energy development in 

the GOM in the near future. The immediate effects of disruptions to marine mineral development 

would be small since most mineral extractions (currently sand) in the GOM have occurred in State 

waters for beach restoration and public works projects. However, as these sources become 

depleted, the identification and exploitation of new sand sources in Federal waters will become more 

important.

Alternative E could increase costs by up to 10 percent over pre-settlement levels (Tables 

4.13.9-1 and 4.13.9-2). In addition, the season restrictions and additional marine mammals to 

monitor added under the expanded PAM Program would likely reduce operational efficiencies by up 

to 7 percent due to increased shutdowns (Table 4.13.9-3). This alternative also requires a 10 to 

25 percent reduction in the line miles of deep-penetration, multi-client seismic activities from the 

estimated baseline levels in a calendar year. If a 10 to 25 percent reduction in G&G activity arises 

due to forces external to this alternative (e.g., due the current general slowdown in the G&G 

industry), Alternative E would have minor impacts, similar to Alternative C. Refer to the general 

discussion above regarding the socioeconomic impacts of the alternatives.

However, if this alternative directly causes surveys to be curtailed or cancelled in order to 

attain the targeted reduction in G&G activity, the economic impacts would be more pronounced than 

under Alternative C. In particular, the curtailment or cancellation of G&G activities might cause the 

G&G industry to contract, resulting in layoffs and business closures. As the size of the G&G industry 

contracts, workers in the industry would have less income to spend in the regional economy. At the 

same time, the suppliers to the G&G industry (i.e., related economic sectors such as boat providers, 

equipment providers, etc.) would see the overall demand for their goods and services decrease, 

potentially generating a reduction in regional economic output and employment opportunities. 

Furthermore, the curtailment or cancellation of G&G surveys may delay or reduce the ability of oil 
Gulf of Mexico G&G Activities Programmatic EIS 4-401

and gas companies to identify and develop offshore oil and gas reserves. If oil and gas companies 

are not able to commission site-specific G&G surveys in a given year, then they may have to delay 

investments in new oil rigs and platforms or incur additional engineering and construction costs to 

compensate for the lack of geohazard information. Additionally, areas in the GOM that have not 

undergone extensive G&G surveys may become less desirable for oil and gas leasing purposes and 

may be developed at a slower pace as a result of the reduced availability of G&G surveys.

In addition to a potential contraction in the oil and gas industry and interrelated regional 

economic sectors, to the extent that offshore oil and gas production becomes more costly or 

economically infeasible as a result of the reduced G&G survey activity, there may be a resultant 

effect on oil and gas prices. Given the limited substitutes for energy generation, changes in the 

supply of oil or natural gas, even in the short term, may result in price changes. Increased oil prices 

have negative economic implications at both the household level and macroeconomic level. 

Increasing the share of household spending on oil and gas reduces disposable income. Similarly, 

the increase in oil and gas prices increases operational costs of businesses. In general, increased 

oil prices can generate inflation and hinder economic growth at the national level.

However, the oil market is global; thus, the potential for a reduction in production from the 

GOM to affect oil prices depends on how significant the reduction is with respect to global production 

levels, not just production from the GOM, in a given timeframe. In addition, external factors 

influencing oil prices, such as the geopolitical climate and energy demand in China and other rapidly 

developing economies, significantly affect oil prices and may marginalize the effects of delayed or 

reduced production from the GOM, depending on how significant GOM oil production is globally.

Independent of oil price impacts, stable domestic production contributes to the energy 

independence of the U.S. Thus, to the extent that reduced G&G activity under this alternative leads 

to reduced domestic oil and gas production, U.S. energy independence could be affected. The 

magnitude of such a reduction, however, will depend not only on the change in offshore oil and gas 

production but also on the extent to which oil and gas companies divert capital from offshore oil and 

gas development to onshore development in the U.S.

Considering these multiple factors, if Alternative E causes G&G activity to decrease by 10 to 

25 percent, the impacts of Alternative E would likely be minor to moderate. 

4.13.9.6 Impacts – Alternative F (Alternative C Plus Area Closures)

Alternative F could cause socioeconomic impacts through various means, e.g., by increasing 

the costs of G&G activities over pre-settlement levels, by preventing a certain survey from occurring, 

by delaying G&G activity, or by causing G&G activities to glean less information than would have 

been obtained under pre-settlement conditions. More new oil and gas drilling in the AOI would 

become dependent on existing geophysical data. Additional costs would be incurred by the oil and 

gas companies as more uncertainty and inefficiencies would be introduced into the exploration 

process. Any increased costs would be borne by either the seismic surveying company or by the 
4-402 Description of the Affected Resources and Impact Analysis

exploration and production company, depending on the extent to which the increased costs will 

result in increased prices for seismic services. All else being equal, the increased costs would lead 

to decreased profits for decreased profits for these companies, although the increased costs would 

also serve as income to the providers of mitigation-related services. Depending on the amount of 

lost business, G&G companies could move to other areas or go out of business. If a seismic survey 

were to be curtailed (or cancelled altogether), the associated companies and employees in the oil 

and gas supply chain would lose the associated income, and the overall economy would not receive 

the benefit of any lost oil and gas production. For example, disruptions to oil and gas production 

could increase energy prices and could lead to broader job losses. The majority of the associated 

socioeconomic impacts would occur in coastal Texas and Louisiana, although some impacts (such 

as lost profits or lost oil and gas production) could be felt elsewhere. These impacts would also 

depend on the state of the oil and gas industry, as well as the overall economy. In 2016, the overall 

United States economy is reasonably healthy, but the oil and gas industry is struggling with low 

energy prices (which is having a disproportionate impact on the Texas and Louisiana economies). 

Any loss in G&G activities could also negatively impact renewable energy or marine mineral 

development. However, there is not expected to be substantial renewable energy development in 

the GOM in the near future. The immediate effects of disruptions to marine mineral development 

would be small since most mineral extractions (currently sand) in the GOM have occurred in State 

waters for beach restoration and public works projects. However, as these sources become 

depleted the identification and exploitation of new sand sources in Federal waters will become more 

important.

The mitigation measures for Alternative C would increase costs by up to 10 percent over 

pre-settlement levels (Tables 4.13.9-1 and 4.13.9-2). The seasonal restrictions and additional 

marine mammals to monitor added under the expanded PAM Program would likely reduce 

operational efficiencies by up to 7 percent due to increased shut downs (Table 4.13.9-3). In 

addition, the area closures, particularly the CPA Closure Area, would cause more noticeable 

economic impacts than under Alternative C. In particular, the CPA Closure Area includes prolific oil 

and gas basins. All proposed new oil and gas drilling in the closure areas would become dependent 

on existing seismic data. The USDOI, BOEM (2016) provides information regarding the existing 

amounts of seismic coverage in various areas in the GOM. There are some levels of seismic 

coverage for many parts of the CPA Closure Area. However, the closure areas would prevent 

conducting seismic surveys in these areas using more advanced methods, particularly as continually 

evolving technology expands the frontiers of oil and gas development. As a result, basins that have 

not undergone sufficient G&G surveys prior to area closures would become less desirable for oil and 

gas leasing purposes and may be developed at a slower pace as oil and gas companies focus on 

lower-risk areas without survey restrictions. Any oil and gas development that is displaced from the 

closure areas would be replaced by the development of reserves that companies expect to be of 

lower quality or more difficult to extract. As a result, the closure areas may reduce oil and gas 

production or industry income, which may raise oil and gas prices or reduce industry employment. 

The design and placement of new oil rigs and platforms in closure areas would also become less 

certain as site-specific G&G surveys would not be available to guide them, making the interference 

of geohazards a greater possibility and the construction of these structures more risky. Additional 
Gulf of Mexico G&G Activities Programmatic EIS 4-403

engineering and construction costs would likely need to be incurred to compensate for the lack of 

geohazard information. Finally, Alternative F would restrict oil and gas development to a smaller 

geographic area, which could introduce space conflicts among G&G firms attempting to survey 

within this smaller area.

As described for Alternative E, the potential for reduced production in the GOM to affect oil 

prices depends on the relative global significance of GOM production to global production and other 

external influences. In addition, even in the case that the reduction in production is insignificant at a 

global scale, stable domestic production contributes to the energy independence of the U.S. The 

magnitude of energy independence impacts associated with reduced offshore production, however, 

will depend on the extent to which oil and gas companies divert capital from offshore oil and gas 

development to onshore development in the U.S.

Considering these factors, the socioeconomic impacts of Alternative F are expected to be 

minor to moderate. The exact impacts will depend on the extent to which existing seismic data 

coverage can fulfil the oil and gas industry’s exploration and development plans in the closure areas. 

Refer to the general discussion above regarding the socioeconomic impacts of the alternatives.

4.13.9.7 Impacts – Alternative G (No New Activity Alternative)

Overall, Alternative G would lead to major socioeconomic impacts. Under Alternative G, no 

new G&G activities associated with the development of oil and gas reserves, renewable energy, or 

marine materials would be authorized to occur within the AOI during the time period covered by this 

Programmatic EIS. Other G&G survey activities would be unaffected by this ban, including any that 

occur within State waters, those that are for scientific studies and regulated by other Federal 

agencies, and any BOEM non-regulated G&G activities (i.e., geophysical surveys for archeological 

and benthic resources). The G&G activities already approved would be allowed to continue for the 

duration of their authorized permit/authorization; however, no additional permits/authorizations would 

be approved.

Implementation of Alternative G would have a major negative economic impact on the G&G 

industry. Restricting all G&G activities associated with the development of oil and gas reserves, 

renewable energy, and marine minerals as planned under Alternative G would result in widespread 

layoffs and business closures within the industry. While some economic activity and employment in 

the G&G industry would continue as work continued on survey activities not included in the proposed 

action and through the reprocessing of existing data, the total size of the G&G industry in the GOM 

would greatly contract. As the size of the G&G industry contracts, workers in the industry would 

have less income to spend in the regional economy. At the same time suppliers to the G&G industry 

would see the overall demand for their goods and services decrease. Local merchants could 

respond to this decrease in demand by decreasing employment at their operations and/or 

purchasing fewer goods and services from their providers. The majority of the direct socioeconomic 

impacts associated with the cessation of all G&G activities under Alternative G would be 

concentrated in Harris County and Fort Bend County, Texas, and in Lafayette Parish, Louisiana.
4-404 Description of the Affected Resources and Impact Analysis

The cessation of G&G activities under Alternative G would also have a noticeable impact on 

the oil and gas industry throughout the Gulf Coast region. Immediate effects would result from the 

inability of the oil and gas industry to collect new G&G data once existing permits/leases expire. All 

proposed new oil and gas drilling in the AOI would become dependent on existing geophysical data. 

Additional costs would be incurred by the oil and gas companies as more uncertainty would be 

introduced into the exploration process. Areas in the GOM that have not undergone sufficient G&G 

surveys prior to cessation would become less desirable for oil and gas leasing purposes and may 

not be developed. The design and placement of new oil rigs and platforms would become less 

certain as site-specific G&G surveys would not be available to guide the placement of new rigs and 

platforms, making the interference of geohazards a greater possibility and the construction of these 

structures more risky. Additional engineering and construction costs would likely be incurred as 

“over engineering” and would be required to compensate for the lack of geohazard information. The 

cessation of G&G activities would eventually threaten all components of the offshore oil and gas 

industry. Employment and income related to oil and gas industry exploration, development, and 

production would decline. Oil and gas production would gradually decline, which would increase 

prices and the United States’ reliance on onshore and foreign energy sources. The U.S. 

Government’s revenues from rentals, royalties, and bonus bids would also decline.

Alternative G would hinder any development of potential renewable energy leases by 

eliminating any opportunity for geological safety and characterization surveys. This would have the 

effect of slowing job growth in alternative energy production and would hinder the transition from 

fossil fuels to non-traditional power sources. Although there currently are no active renewable 

energy projects in the GOM, this could drastically slow potential GOM job growth for this industry 

and could hinder production of renewable energy from Federal waters. This could increase the time 

needed to switch from fossil fuels to renewable ones and could increase domestic dependency on 

foreign sources of fossil fuels.

Under this alternative, all G&G activities for marine minerals would cease, thereby making 

locating and securing significant quantities of sedimentary resources more difficult and costly. State 

and local governments would be limited to utilizing only limited, known resources or would be 

required to acquire these marine mineral resources from other sources. The immediate effect would 

be small since most mineral extractions (currently sand) in the GOM have occurred in State waters 

for beach restoration and public works projects. However, as these sources become depleted, the 

identification and exploitation of new sand sources in Federal waters would not be possible without 

the use of G&G surveys. This would have the effect of further coastal erosion and lost revenue for 

communities that depend on tourism. Beaches and sand dunes serve as storm and surge buffers 

for coastal communities, and the loss of these areas due to erosion would present these 

communities with a greater potential for damage due to severe weather events such as hurricanes, 

which strike the Gulf Coast quite frequently. The result would be some businesses, jobs, and 

families leaving coastal areas and an increased economic burden on taxpayers, local, State and 

Federal governments, as well as insurance companies, who would have to pay for the rebuilding of 

homes and businesses.
Gulf of Mexico G&G Activities Programmatic EIS 4-405

Given the above, Alternative G would lead to major negative socioeconomic impacts.

4.14 NMFS’ ANALYSIS OF CHRONIC EFFECTS IN THE GULF OF MEXICO IN SUPPORT 

OF THE MMPA PETITION FOR INCIDENTAL TAKE REGULATIONS

Effective detection of sounds is critical for aquatic animals and methods are needed to 

assess and minimize the longer term and aggregate effects of noise on marine species and their 

habitat, in addition to acute impacts at closer range. Here, we present the results of a first-order 

assessment of the chronic and cumulative effects of noise produced by seismic activities in the GOM

performed in support of the MMPA rulemaking process (refer to Appendix K for the full report).

Modeling was conducted for 10 locations (receiver sites; Table 1 and Figure 1 of 

Appendix K of biological importance and for four scenarios corresponding to G&G survey 

alternatives in this Programmatic EIS, including the following: full proposed levels of seismic; a 25 

percent reduction in seismic; and both with and without time/area closures at each of these activity 

levels (Alternatives C, E1, E2, and F as described in Table 2 of Appendix K). “Lost listening area” 

was calculated among each of the four scenarios and relative to a baseline ambient noise estimate 

for the full modeled frequency bandwidth (10-5,000 Hz) and adjusted to account for the hearing 

sensitivity of low-, mid-, and high-frequency cetaceans. Because of heightened concern for lowfrequency hearing specialists, loss of listening area in this bandwidth is biologically relevant for the 

majority of GOM cetacean species, as well as endangered turtles and a wide variety of fishes and 

invertebrates in the region. In addition, “lost communication space” was calculated among scenarios 

and relative to ambient estimates for the specific 1/3 octave band centered at 100 Hz, representing 

the dominant frequencies of Bryde’s whale vocalizations. Bryde’s whales are the sole GOM 

cetacean species classified within the low-frequency hearing group, producing calls that span a lowfrequency range that directly overlaps the dominant energies produced by airguns. Results are 

reported as remaining listening area or communication space for a maximum of three depths (5, 30, 

and 500 m [16, 98, and 1,640 ft]) at each of the 10 locations. Broadly, results for projected full 

seismic activity levels indicate significant losses in both the listening area (6 of 10 locations lost 

>50% area) and communication space (5 of 10 locations lost >50% space), including severe losses 

at the deepest, off-shelf location chosen for modeling (Site 5, >99% listening space loss for lowfrequency cetaceans) and within the FGBNMS (Site 10, 82-90% losses for low- to mid-frequency 

cetaceans). Two locations within cetacean biologically important areas (Sites 7 and 10, within the 

Bryde’s whale area and coastal bottlenose dolphin area, respectively) incurred virtually no losses 

due to a combination of lower projected seismic levels in and around the area and local propagation 

conditions. Losses were generally more severe at lower frequencies and at greater depths. 

Scenarios that reduced overall levels of seismic in the region resulted in locations retaining more 

listening space relative to ambient levels and to full seismic projections. At locations within closure 

areas where losses were otherwise noted (e.g., Sites 6 and 8), applying closures maintained more 

listening and communication area.

There is ample evidence to support the fact that significant reductions in listening area or 

communication space can negatively affect aquatic animals; however, data are lacking to document 
4-406 Description of the Affected Resources and Impact Analysis

links to consequences for long-lived and often wide-ranging species such as marine mammals. In 

contrast with estimation of acoustic harassment, this analysis is not designed to evaluate the 

exposure of individual animals to seismic sources from one moment to the next. Rather, this 

analysis is intended to ensure consideration of the longer term and wider-ranging noise effects from 

these sources and to augment the more traditional analysis of acute effects (occurrence of exposure 

that may potentially cause injury and behavioral harassment) addressed in Chapter 4. 

While these results are broadly informative (especially when considered as a whole across 

the GOM), it is important to remain cognizant of the methods and simplifying assumptions when 

making location-specific interpretations and comparisons. For example, the distribution in space and 

time of seismic survey activity will significantly influence the resulting cumulative noise exposure at a 

specific location. Here, projected levels are distributed uniformly within planning areas, but 

actualized survey activity may result in higher concentrations in some areas within the planning 

areas and lower concentrations in others. The effect of concentrations of activity in high proximity to 

selected locations will continue to be offset by the methods applied here to remove the closest 

10 percent of pulses in order to focus on long-term accumulation of energy at regional scales. 

However, this same method can result in an under-representation of the value of closure areas at 

maintaining listening and communication space. Similarly, the assumption made here that 

25 percent of the activity that would have occurred in a closure area would be redistributed outside 

that area must be carefully considered when interpreting results, as this consequence is yet 

unknown (i.e., applying closures results in increased levels of activity in remaining area outside of 

closures).

Finally, all of the listening area losses presented here are relativistic, and most examine the 

differences in areas available under different seismic activity scenarios, without reliance on the 

difficult task of evaluating the levels of noise in the absence of seismic in the GOM. However, NEPA 

necessitates that we apply a no activity scenario to further assess the impacts resulting from the 

various alternatives. Because of the lack of available measured data, “non-seismic” ambient noise 

was estimated for this exercise using modeled noise contributed by ship traffic and wind, which are 

the most common noise-contributing factors in the GOM that are “non-seismic.” Limited acoustic 

measurements, as well as contributions to modeled estimates from additional noise sources 

(especially in coastal areas), suggest that the values used here would be lower than the actual noise 

levels in the GOM in the absence of seismic and point to the need for spatially varying baseline 

measurements in the region.
CHAPTER 5 

OTHER NEPA CONSIDERATIONS

Gulf of Mexico G&G Activities Programmatic EIS 5-3 

5 OTHER NEPA CONSIDERATIONS

5.1 UNAVOIDABLE ADVERSE IMPACTS OF THE PROPOSED ACTION

The NEPA regulations require an EIS to disclose any adverse environmental effects that 

cannot be avoided should the proposed action be implemented (40 CFR § 1502.16). While 

numerous effects to physical; ecological; and social, cultural, and economic resources can be 

avoided and minimized by adherence to regulations, guidance, and conventions; utilization of best 

management practices and industry standards; and implementation of mitigation measures, some 

unavoidable adverse effects associated with the proposed action can be expected to remain 

regardless of avoidance, minimization, and mitigation.

The use of airguns during seismic airgun surveys would result in unavoidable Level B 

harassment of marine mammals and may cause behavioral responses in sea turtles, fishes, and 

marine and coastal birds. Mortality to marine mammals and sea turtles is not expected, and physical

injury to marine mammals and sea turtles is expected to be avoided to the maximum extent 

practicable through protective measures included in the proposed action, including an exclusion 

zone and operational mitigation measures as described in Chapters 2 and 4 and Appendix B. 

However, some marine mammals may be exposed to sound levels that constitute Level A 

harassment (short of mortality) and that may induce TTS or PTS.

The behavioral impacts to marine mammals anticipated as a result of the proposed actions 

analyzed in this Programmatic EIS are short-term disruption of behavioral patterns, abandonment of 

activities, and/or temporary displacement from discrete areas. Due to the extensive mitigations in 

the proposed actions, no serious injuries or mortalities are anticipated.

During non-airgun HRG surveys, the use of other acoustic sources such as side scan 

sonars; boomer, sparker, and CHIRP subbottom profilers; and MBESs may cause behavioral 

responses in marine mammals that would also constitute Level B harassment. Mortality to marine 

mammals and sea turtles is not expected, and physical injury to marine mammals and sea turtles is 

expected to be avoided through protective measures included in the proposed action, including 

exclusion zone closures and operational mitigation measures, as described in Chapters 2 and 4. It 

is highly unlikely that animals would be exposed to sound levels that constitute Level A harassment 

(in marine mammals) or that may induce TTS or PTS during non-airgun HRG surveys. Non-routine 

effects to marine mammals, sea turtles, marine and coastal birds, fishes, and EFH that would be 

unavoidable and adverse would include direct exposure to fuel spills as some individuals may not 

recover from exposure.

Some other unavoidable adverse effects on marine life would be expected to occur as a 

result of the proposed action. For example, seafloor disturbing activities such as geological and 

geotechnical sampling and placement of bottom-founded equipment or structures would inevitably 

disturb soft bottom benthic habitat. Short-term disturbances could include resuspension of seafloor 

sediments with very limited burial and rapid recolonization; no long-term impacts would be 

anticipated. Impacts to sensitive benthic communities (i.e., coral, hard/live bottom, and 
5-4 Other NEPA Considerations

chemosynthetic communities) are expected to be avoided because BOEM requires site-specific 

information prior to approving any G&G activities involving seafloor disturbing activities or placement 

of bottom-founded equipment or structures in the AOI.

Unavoidable adverse effects from routine operations to archeological resources would be 

avoided and minimized with existing regulations; however, there is always a risk of unavoidable 

adverse impacts to archaeological resources where surveys are not required, inadequate, or 

unavailable. Non-routine unavoidable adverse effects could result from direct oil exposure and 

cleanup activities.

5.2 IRREVERSIBLE AND IRRETRIEVABLE COMMITMENT OF RESOURCES

Section 102(2)(c)(ii) of NEPA requires an EIS to identify irreversible and irretrievable 

commitments of resources that would be involved in the proposed action should it be implemented. 

Resources include renewable and non-renewable natural resources, including fish and wildlife 

habitat. A commitment of a resource is considered irreversible when the primary or secondary 

impacts from its use limit future options for its use. This commitment of resources applies primarily 

to the effects of use of non-renewable resources, which are resources that cannot be replenished by 

natural means (e.g., oil, natural gas, iron ore, and cultural resources). An irretrievable commitment 

refers to the use or consumption of a resource that is neither renewable nor recoverable (e.g., the 

disturbance of a cultural site) for use by future generations.

The proposed action would provide for the development of a permitting/authorization process 

to allow industry to conduct surveys to investigate the geology and geophysics of the seafloor within 

the AOI. Both oil and gas G&G activities and marine minerals G&G activities would require 

additional BOEM environmental reviews and approvals prior to the commencement of any “on the 

water” activities that could impact the environment. At the time of these reviews, BOEM has the 

opportunity to request or require additional mitigations if warranted. In addition, the Secretary of the 

Interior retains the discretion under the OCSLA to, among others, cancel or suspend plans, 

activities, and permits at any time, so as to protect the environment (refer to 43 U.S.C. § 1334(a)). 

Finally, for G&G activities related to renewable energy, BOEM requires that postlease G&G activities 

comply with mitigation measures included in the lease stipulations.

Non-renewable resources that would be consumed during the operation of survey vessels, 

should G&G activities proceed, include the consumption of ship and aircraft fuel. The proposed 

surveys would also require a commitment of human labor and financial resources. Because the 

reuse of these resources may not be possible, they would be irreversibly and irretrievably committed 

as part of the proposed action. Nonetheless, commitment of these resources is not expected to be 

significant.

In general, the impact of routine operations would not constitute an irreversible and 

irretrievable commitment of biological resources. Displacement and habitat loss may result in the 

reduction of some local populations and become irretrievable if alterations to the environment were 
Gulf of Mexico G&G Activities Programmatic EIS 5-5 

permanently maintained; however, the degree of displacement and habitat loss would represent a 

transitory and negligible effect on the overall populations of most species. No critical habitat 

associated with threatened or endangered species would be lost as a result of implementation of the 

proposed action and subsequent implementation of G&G activities, should they occur.

5.3 RELATIONSHIP BETWEEN SHORT-TERM USES OF THE ENVIRONMENT AND THE 

MAINTENANCE AND ENHANCEMENT OF LONG-TERM PRODUCTIVITY

The NEPA regulations require that an EIS include an analysis of the relationship between a 

project’s short-term impacts on the environment and the effects those impacts may have on the 

maintenance and enhancement of long-term productivity in the affected environment (40 CFR § 

1502.16). Impacts that narrow the range of beneficial uses of the environment are of particular 

concern. The proposed G&G surveys would allow industry to investigate the geology and 

geophysics of the seafloor within the AOI. This action would require short-term and long-term 

commitments of human labor and financial resources.

Non-renewable resources that would be consumed during the operation of seismic research 

vessels include fuel and oil. The planned monitoring and mitigation measures, which include 

avoiding sensitive habitats and/or seasonally important areas, visual monitoring, and an exclusion 

zone, would serve to minimize the effects of the proposed surveys. The majority of effects from 

G&G surveys would be temporary in nature, highly localized, transient, and nominal in effect. 

Although some space-use effects may be evident, they would also be highly localized and transient. 

As a result, implementation of the proposed action would not result in any environmental impacts 

that would significantly affect the maintenance and enhancement of long-term productivity of the 

marine environment (Chapter 4).

CHAPTER 6 

PUBLIC INVOLVEMENT AND 

AGENCY CONSULTATION AND COORDINATION

Gulf of Mexico G&G Activities Programmatic EIS 6-3 

6 PUBLIC INVOLVEMENT AND AGENCY CONSULTATION AND 

COORDINATION

6.1 DEVELOPMENT OF THE PROPOSED ACTION

BOEM prepared this Programmatic EIS to evaluate reasonably foreseeable impacts to the 

marine environment from G&G survey activities in Federal and State waters from the coastline out to 

the EEZ within the WPA, CPA, and EPA for the three program areas, i.e., oil and gas, renewable 

energy, and marine minerals. BOEM conducted early coordination with appropriate Federal and 

State agencies and other concerned parties to develop the proposed action in this Programmatic 

EIS. Key agencies and organizations were contacted, including the FWS, NOAA, USACE, USDOD, 

and National Aeronautics and Space Administration. The BSEE and NOAA are acting as 

cooperating agencies. Chapter 6.3.3 further discusses the cooperating agency process and the 

respective roles of cooperating agencies. Based on the information and analysis presented in 

Chapter 4, this Programmatic EIS presents the environmental impacts of the proposed action and 

the alternatives in comparative form, defining the issues and providing a clear basis for choice 

among alternatives by decisionmakers and the public.

6.2 NOTICE OF INTENT

The NMFS previously initiated the scoping process in 2004 for the purpose of soliciting 

comments from stakeholders on the scope of a Draft Programmatic EIS, identifying issues to be 

analyzed, and developing possible alternatives and mitigating measures. BOEM reinitiated the 

scoping process through a Notice of Intent (NOI) with a public comment period and a series of public 

meetings in 2013.

BOEM published an NOI in 78 FR 27427 on May 10, 2013, announcing its intent to prepare, 

cooperatively with NOAA, a Programmatic EIS to evaluate potential environmental effects of multiple 

G&G activities in OCS waters of the GOM, extending from the coastline to the seaward boundary of 

the EEZ. The NOI included dates, times, and locations for scoping meetings (Chapter 6.3.1). The 

public comment period was initially set to close on June 24, 2013; however, BOEM issued a 

correction to the NOI on June 5, 2013 (78 FR 33859), changing the date for closing the public 

comment period to July 9, 2013.

6.3 SCOPING AND DEVELOPMENT OF THE DRAFT PROGRAMMATIC EIS

BOEM, as the lead agency with BSEE and NOAA as cooperating agencies, prepared this 

Draft Programmatic EIS in accordance with CEQ regulations implementing NEPA (40 CFR part 

1502), USDOI implementing procedures for NEPA (43 CFR part 46), and NOAA procedures for 

implementing NEPA (USDOC, NOAA, 1999).

Scoping is an early and open process for determining the scope of the proposed action and 

the significant issues the EIS must analyze in depth. During the scoping process, the public 

provides input to assist the agency preparing the EIS (i.e., BOEM) in defining and prioritizing issues 

through meaningful participation, including the submission of comments. The scoping period begins 
6-4 Public Involvement and Agency Consultation and Coordination

with the publication of an NOI. The scoping process is intended to solicit input from Federal, State, 

local, and Tribal governments; commercial interests; environmental groups; and the general public.

6.3.1 Scoping Meetings

Public scoping meetings were held by the NMFS at the following locations and dates (one 

meeting per location):

Friday, December 3, 2004

Pontchartrain Hotel

2031 St. Charles Avenue

New Orleans, Louisiana

Thursday, December 16, 2004

NOAA Science Center

1301 East-West Highway

Silver Spring, Maryland

Public scoping meetings were held by BOEM at the following locations and dates (one 

meeting per location):

Monday, June 10, 2013

Embassy Suites Westshore

Tampa Airport

Tampa, Florida

Monday, June 17, 2013

Galveston Hilton

5400 Seawall Boulevard

Galveston, Texas

Tuesday, June 11, 2013

Ramada Plaza Beach Resort

1500 Miracle Strip Parkway, SE

Fort Walton Beach, Florida

Wednesday, June 19, 2013

Bureau of Ocean Energy Management

1201 Elmwood Park Boulevard

New Orleans, Louisiana

Wednesday, June 12, 2013

Government Plaza

205 Government Street

Mobile, Alabama

Thursday, June 20, 2013

National Oceanic and Atmospheric 

Administration

1305 East-West Highway

Silver Spring, Maryland

Thursday, June 13, 2013

Courtyard by Marriott, 

Gulfport Beachfront

1600 East Beach Boulevard

Gulfport, Mississippi

6.3.2 Comments Received During Scoping

During the initial scoping period, November 18 to December 22, 2004, the NMFS received a 

total of 11 comment letters from the following: 4 comments from nongovernmental organizations 

(NGOs); 1 comment from an industry group; 1 comment from a geophysical subcontractor; and

5 from members of the public.

During the second scoping period, May 10 to July 9, 2013, BOEM received a total of 

66 comments through the Internet/email (65%), formal letters (3%), and public meeting testimony, 

including oral and written comments (32%). Comments were received from individuals and 

organizations from nine states, Washington, DC, and Canada. Most comments came from private 
Gulf of Mexico G&G Activities Programmatic EIS 6-5 

citizens. Other sources included Federal and State agencies, NGOs, and members of various for 

profit industries. Most comments expressed concerns about G&G activities associated with offshore 

drilling, while a few comments also discussed siting of renewable energy. No comments were 

received concerning marine minerals activities. Of the comments received, 56 percent were 

opposed to G&G activities, 27 percent supported them, and 17 percent were neutral. Primary topics 

of the scoping comments included the following:

• concerns regarding impacts (particularly from underwater noise) to marine 

wildlife, specific species, and habitats; 

• impacts to fisheries and recreation and tourism; 

• economic growth and job creation from G&G activities; 

• advocating the use of alternative technologies for data collection; 

• implementing mitigating measures such as restricting activities within time-area 

closures, expanding shutdown requirements, banning survey activities in the 

EPA, banning all activities supporting oil and gas, expanding the use of PAM, 

reducing source levels of survey equipment, sound source verification, 

establishing activity caps to lower cumulative sound exposure; and 

• obtaining additional data regarding post-Deepwater Horizon effects, long-term 

monitoring effects of G&G activities on marine mammals, and evaluating

mitigating measure effectiveness.

The scope and content of this Programmatic EIS have been formulated to ensure the issues 

and concerns expressed by stakeholders during the scoping process have been fully addressed. 

The scoping report can be reviewed at http://www.boem.gov/GOM-PEIS-Scoping-Report/. 

6.3.3 Cooperating Agencies

BOEM is required, per 43 CFR § 46.225, to invite eligible government entities to participate 

as cooperating agencies during the development of an EIS. Per CEQ regulations (40 CFR § 

1508.5), a cooperating agency may be any Federal agency that has jurisdiction by law or special 

expertise with respect to environmental impacts expected from a proposal. The responsibilities of a 

cooperating agency are provided at 40 CFR § 1501.6(b). To ensure the responsibilities of the lead 

agency and the relationship between cooperating agencies are clear to all, a Memorandum of 

Agreement (MOA) is typically executed by the agencies. The MOAs delineate roles and 

responsibilities in accordance with CEQ’s January 30, 2002, “Memorandum for the Heads of Federal 

Agencies: Cooperating Agencies in Implementing the Procedural Requirements of the National 

Environmental Policy Act.” 

An NOI that was published in the Federal Register on May 10, 2013, included an invitation 

from BOEM to other Federal agencies and State, Tribal, and local governments to consider 

becoming cooperating agencies in the preparation of the Programmatic EIS. During the scoping 
6-6 Public Involvement and Agency Consultation and Coordination

period, BOEM received no expressions of interest by any Federal, State, or local government 

agency having jurisdiction or special expertise with respect to becoming a cooperating agency, aside 

from the agreements with BSEE and NOAA (Appendix A).

In addition, in September 2013, BOEM sent joint inquiries to Federal agencies to participate 

as cooperating agencies on this Programmatic EIS. Federal agencies that were sent inquires have 

either declined or provided no response (Appendix A). In February 2014, the Mississippi 

Development Authority indicated that they would be interested in participating in this Programmatic 

EIS. In response, BOEM transmitted an invitation for interest to Mississippi Development Authority

on May 27, 2014. The Mississippi Development Authority provided no response to BOEM’s inquiry.

6.3.3.1 Bureau of Safety and Environmental Enforcement

BOEM and BSEE were formally established on October 1, 2011, as part of a major 

reorganization of the USDOI’s offshore regulatory structure. The BSEE is the lead Federal agency 

in regulatory oversight and enforcement of G&G activities. The BSEE has an interest in the 

regulation of G&G surveys due to its responsibilities in working with BOEM to ensure the orderly 

development of mineral and other resources on the Federal OCS. In particular, BSEE is responsible 

for issuing permits for test drilling activities related to G&G explorations of the OCS (USDOI, BOEM, 

n.d.).

The BSEE uses a full range of authorities, policies, and tools to compel safety, emergency 

preparedness, environmental responsibility, and appropriate development and conservation of 

offshore oil and natural gas resources. One of these authorities is the OCSLA (43 U.S.C. § 

1348(c)), which requires BSEE to conduct on-site inspections of all oil and gas operations on the 

OCS to ensure compliance with lease terms, regulations, and approved plans, and to assure that 

safety and pollution-prevention requirements are met. Noncompliance with these requirements or 

procedures may be followed by prescribed enforcement actions consisting of written warnings or 

shut-ins (a temporary sealing) of platforms, zones (wells), equipment, or pipelines. No similar 

inspections are required for the MMP or OREP. Key functions of BSEE include the following:

• an offshore regulatory program that develops standards and regulations, and 

emphasizes a culture of safety in all offshore activities;

• oil-spill response preparation, including review of industry’s Oil Spill Response 

Plans, to ensure compliance with regulatory requirements;

• environmental enforcement with a focus on compliance by operators with all 

applicable environmental regulations as well as ensuring that operators adhere to 

the stipulations of their approved leases, plans, and permits; and

• funding scientific research to enhance the information and technology needed to 

build and sustain the organizational, technical, and intellectual capacity within 

and across BSEE’s key functions that keeps pace with industry technological 

improvements, innovates regulation and enforcement, and reduces risk through 
Gulf of Mexico G&G Activities Programmatic EIS 6-7 

systematic assessment and regulatory and enforcement actions in order to better 

carry out BSEE’s mission.

BOEM and BSEE

As part of the reorganization of Title 30 of the CFR after the creation of BOEM and BSEE, 

several MOAs were developed between the Bureaus to delineate responsibilities and establish the 

working relationship between the two agencies to synchronize environmental review and 

environmental enforcement for authorizations required to conduct conventional energy and 

resources activities on the OCS. An Environmental and NEPA MOA, dated October 3, 2011, was 

established to help both Bureaus minimize duplication of efforts, promote consistency in procedures 

and regulations, and resolve disputes (Appendix A).

The stated purpose of the Environmental and NEPA Memorandum of Agreement is that 

BSEE will serve as a cooperating agency on appropriate Bureau of Ocean Energy Management

NEPA documents, oversee any requisite environmental monitoring needs, and ensure post-activity 

environmental compliance needs are met and documented. There is an expectation that serving as 

a cooperating agency, where practicable, will be the standard protocol for any Bureau of Ocean 

Energy Management NEPA analysis that BSEE may adopt for its decisions and that is related to 

BSEE environmental monitoring and compliance activities. Consistent with this policy, BSEE is a 

cooperating agency on this document.

6.3.3.2 National Oceanic and Atmospheric Administration

The NOAA is serving as a cooperating agency because the scope of the proposed action 

and alternatives involve G&G activities that have the potential to impact marine resources, including 

living and nonliving marine resources within NOAA’s National Marine Sanctuaries (NMS). The 

NMFS has a statutory responsibility to protect, conserve and recover marine mammals and 

threatened and endangered species. This includes the authority to authorize incidental take of 

marine mammals, engage in consultations with other Federal agencies, which can allow for take of 

threatened and endangered listed species, and enforce against unauthorized takes under both 

statutes. The NMFS executes these authorities pursuant to the Marine Mammal Protection Act of 

1972, as amended (MMPA; 16 U.S.C. §§ 1361 et seq.) and the Endangered Species Act of 1973 

(ESA; 16 U.S.C. §§ 1531 et seq.). The NOAA’s Office of National Marine Sanctuaries (ONMS) has 

a statutory responsibility to protect and conserve the NMS. Consultation pursuant to Section 303(d) 

of the National Marine Sanctuaries Act (NMSA) is required of all Federal agencies for actions that 

are likely to injure sanctuary resources. In addition to consultation requirements, authorizations and 

general or special use permits may be required pursuant to the NMSA (16 U.S.C. §§ 1431-1445c-1) 

and the regulations for implementing the NMSA (15 CFR part 922).

An MOA was previously executed between BOEM and NOAA on June 12, 2013 

(Appendix A), to work as co-lead agencies in the preparation of this Programmatic EIS. After 

further evaluation during the development of this Programmatic EIS, the two agencies determined 

that, pursuant to 40 CFR §§ 1501.5 and 1501.6, BOEM should act as the lead agency and NOAA 
6-8 Public Involvement and Agency Consultation and Coordination

should assist BOEM as a cooperating agency. Therefore, on September 8, 2015, BOEM and NOAA 

executed a new MOA that describes the obligations of both agencies concerning the preparation of 

this Programmatic EIS (Appendix A) with NOAA as a cooperating agency instead of a co-lead. This 

MOA does not affect other responsibilities of the two agencies, NOAA in its role under the MMPA, 

ESA, and NMSA or BOEM in its role under the OCSLA.

6.4 DISTRIBUTION OF THE DRAFT PROGRAMMATIC EIS 

BOEM sent copies of the Draft Programmatic EIS to the government, public, and private 

agencies and groups listed below. Local libraries along the Gulf Coast were provided copies of this 

Draft Programmatic EIS; a list of these libraries is available on BOEM’s website at http://

www.boem.gov/nepaprocess/. 

Federal Agencies

Congress

Congressional Budget Office

House of Representatives

House Resources Subcommittee on 

Energy and Mineral Resources

Senate Committee on Energy and Natural 

Resources

Department of Commerce

National Marine Fisheries Service

National Oceanic and Atmospheric 

Administration

Department of Defense

Department of the Air Force

Department of the Army

Corps of Engineers

Department of the Navy

Naval Mine and ASW Command

Department of Energy

Strategic Petroleum Reserve PMD

Department of Homeland Security

Coast Guard

Department of State

Bureau of Oceans and International 

Environmental and Scientific Affairs

Department of the Interior

Bureau of Ocean Energy Management

Bureau of Safety and Environmental 

Enforcement

Fish and Wildlife Service

Geological Survey

National Park Service

Office of Environmental Policy and 

Compliance

Office of the Solicitor

Department of Transportation

Office of Pipeline Safety

Environmental Protection Agency

Region 4

Region 6

Marine Mammal Commission

National Aeronautics and Space 

Administration

State and Local Agencies

Alabama

Governor’s Office

Alabama Highway Department

Alabama Historical Commission and State 

Historic Preservation Officer

Alabama Public Library Service

Alabama Public Service Commission

City of Mobile

City of Montgomery

Department of Conservation and Natural 

Resources

Department of Environmental 

Management

Geological Survey of Alabama

South Alabama Regional Planning 

Commission

State Legislature Natural Resources 

Committee

Town of Dauphin Island

Florida

Governor’s Office

Bay County

Citrus County

City of Destin

City of Fort Walton Beach

City of Gulf Breeze

City of Panama City

City of Pensacola
Gulf of Mexico G&G Activities Programmatic EIS 6-9 

Department of Agriculture and Consumer 

Services

Department of Environmental Protection

Department of State Archives, History and 

Records Management

Escambia County

Florida Emergency Response 

Commission

Florida Fish and Wildlife Conservation 

Commission

Franklin County

Gulf County

Hernando County

Hillsborough City-County Planning 

Commission

Lee County

Monroe County

North Central Florida Regional Planning 

Council

Okaloosa County

Pasco County

Santa Rosa County

Sarasota County

Southwest Florida Regional Planning 

Council

State Legislature Agriculture and Natural 

Resources Committee

Tampa Bay Regional Planning Council

Walton County

West Florida Regional Planning Council

Withlacoochee Regional Planning Council

Louisiana

Governor’s Office

Calcasieu Parish

Cameron Parish

City of Lake Charles

City of Morgan City

City of New Orleans

Department of Culture, Recreation, and 

Tourism

Department of Economic Development

Department of Environmental Quality

Department of Natural Resources

Department of Transportation and 

Development

Department of Wildlife and Fisheries

Jefferson Parish

Lafourche Parish

Louisiana Geological Survey

South Lafourche Levee District

St. Bernard Parish

State House of Representatives, Natural 

Resources Committee

State Legislature Natural Resources 

Committee

State of Louisiana Library

Terrebonne Parish

Town of Grand Isle

Mississippi

Governor’s Office

City of Bay St. Louis

City of Gulfport

City of Pascagoula

Department of Archives and History

Department of Environmental Quality

Department of Marine Resources

Department of Wildlife, Fisheries, and 

Parks

Jackson-George Regional Library System

Mississippi Development Authority

State Legislature Oil, Gas, and Other 

Minerals Committee

Federally Recognized Indian Tribes

Alabama-Coushatta Tribe of Texas

Caddo Nation

Chitimacha Tribe of Louisiana

Choctaw Nation of Oklahoma

Coushatta Tribe of Louisiana

Jena Band of Choctaw Indians

Kickapoo Traditional Tribe of Texas

Miccosukee Tribe of Indians of Florida

Mississippi Band of Choctaw Indians

Poarch Band of Creek Indians

Seminole Tribe of Florida

Seminole Nation of Oklahoma

Tunica-Biloxi Indian Tribe of Louisiana

Industry

Adams and Reese, LLP

Alabama Petroleum Council

American Petroleum Institute

Applied Technology Research Corporation

Associated Gas Distributors of Florida

Baker Energy

Bepco, Inc.

C.H. Fenstermaker & Associates, Inc.

Century Exploration N.O., Inc.

Chet Morrison Contractors

Chevron U.S.A. Inc.

C-K Associates, LLC
6-10 Public Involvement and Agency Consultation and Coordination

Coastal Environments, Inc.

Columbia Gulf Transmission

CSA International

De Leon & Associates

Ecological Associates, Inc.

Ecosystem Management, Inc.

Energy Partners, Ltd.

Florida Natural Gas Association

Florida Petroleum Council

Florida Power and Light

Florida Propane Gas Association

Freeport-McMoRan, Inc.

General Insulation, Inc.

Global Industries, Ltd.

Halliburton Corporation

Han & Associates, Inc.

Horizon Marine, Inc.

John Chance Land Surveys, Inc.

L&M Botruc Rental, Inc.

Lampl Herbert Consultants

Larose Intercoastal Lands, Inc.

Linder Oil Company

Louisiana Oil and Gas Association

Magnum Steel Services Corp.

Mid Continent Oil and Gas Association

Nature’s Way Marine, LLC

Offshore Process Services, Inc.

Oil and Gas Property Management, Inc.

Phoenix International Holdings, Inc.

Project Consulting Services

R.B. Falcon Drilling

Raintree Resources, Inc.

Science Applications International 

Corporation

SEOT, Inc.

Shell Offshore, Inc.

Stone Energy Corporation

Strategic Management Services-USA

T. Baker Smith, Inc.

The SJI, LLC

The Times-Picayune

URS Corporation

Waring & Associates

Special Interest Groups

1000 Friends of Florida

Alabama Oil & Gas Board

Alabama Nature Conservancy

Alabama Wildlife Federation

Apalachee Regional Planning Council

Apalachicola Bay and Riverkeepers

Audubon Louisiana Nature Center

Audubon of Florida

Barataria-Terrebonne National Estuary

Program

Bay County Chamber of Commerce

Bay Defense Alliance

Citizens Assoc. of Bonita Beach

Clean Gulf Associates

Coalition to Restore Coastal Louisiana

Concerned Shrimpers of America

Conservancy of Southwest Florida

Earthjustice

Florida Chamber of Commerce

Florida Natural Area Inventory

Florida Wildlife Federation

Gulf and South Atlantic Fisheries 

Foundation, Inc.

Gulf Coast Environmental Defense

Gulf Coast Fisherman’s Coalition

Gulf Restoration Network

Houma-Terrebonne Chamber of

Commerce

Izaak Walton League of America, Inc.

LA 1 Coalition, Inc.

League of Women Voters of the 

Pensacola Bay Area

Louisiana Wildlife Federation

Manasota-88

Mobile Bay National Estuary Program

Offshore Operators Committee

Organized Fishermen of Florida

Panama City Beach Convention and 

Visitors Bureau

Pensacola Archaeological Society

Perdido Key Association

Perdido Key Chamber of Commerce

Perdido Watershed Alliance

Restore or Retreat

Roffers Ocean Fishing Forecast Service

Santa Rosa Sound Coalition

Save the Manatee Club

Sierra Club

South Central Industrial Association

Surfrider Foundation

The Ocean Conservancy

The Nature Conservancy

Ports/Docks 

Alabama

Alabama State Port Authority

Port of Mobile
Gulf of Mexico G&G Activities Programmatic EIS 6-11

Florida

Manatee County Port Authority

Panama City Port Authority

Port of Pensacola

Port St. Joe Port Authority

Tampa Port Authority

Louisiana

Abbeville Harbor and Terminal District

Greater Baton Rouge Port Commission

Greater Lafourche Port Commission

Grand Isle Port Commission

Lake Charles Harbor and Terminal District 

Port of Iberia District

Port of New Orleans

St. Bernard Port, Harbor and Terminal 

District 

West Cameron Port Commission

Mississippi

Mississippi State Port Authority

Educational Institutions/Research 

Laboratories

Dauphin Island Sea Laboratory

Florida A&M University

Florida Institute of Oceanography

Florida Institute of Technology

Florida Sea Grant College

Florida State University

Foley Elementary School

Gulf Coast Research Laboratory

Gulf Coast State College

Harbor Branch Oceanography

Louisiana Sea Grant College Program

Louisiana State University

Louisiana Tech University

Louisiana Universities Marine Consortium

Loyola University

McNeese State University

Mississippi State University

Mississippi-Alabama Sea Grant 

Consortium

Mote Marine Laboratory

Nicholls State University

Pensacola Junior College

Tulane University

University of Alabama

University of Florida

University of Louisiana at Lafayette

University of Miami

University of Mississippi

University of New Orleans

University of South Alabama

University of South Florida

University of Southern Mississippi

University of West Florida

Additionally, to initiate the public review and comment period on the Draft Programmatic EIS, 

BOEM took the following actions: 

(1) contemporaneously published a Notice of Availability for the Draft Programmatic 

EIS in the Federal Register, announcing a 45-day comment period; all 

comments received during the comment period will be included as part of the 

Programmatic EIS administrative record;

(2) mailed public notices that reported availability of the Draft Programmatic EIS 

and how to comment to all of the groups and agencies identified below;

(3) emailed a group notification that announced availability of the Draft 

Programmatic EIS and how to comment to all people who had furnished BOEM 

with their email address during scoping or had requested to be on such a 

mailing list;

(4) placed multiple newspaper notices announcing availability of the Draft 

Programmatic EIS, all public meeting locations and times, and how to comment 

on the document in each of the following newspapers that served local media 

markets;
6-12 Public Involvement and Agency Consultation and Coordination

(5) posted the Draft Programmatic EIS on BOEM’s websites at http://

www.boem.gov/GOM-G-G-PEIS/ and http://www.boem.gov/nepaprocess/; 

(6) mailed official letters to the Governor’s Offices of all States along the Gulf Coast 

that may have an interest in providing input on the proposed G&G activities, in 

accordance with BOEM’s policy of consultation and coordination with State and 

local governments; and

(7) mailed official letters to the federally recognized Indian Tribes along the five 

Gulf Coast States. 

All comments received on the Draft Programmatic EIS will be considered during preparation 

of the Final Programmatic EIS.

6.5 PUBLIC MEETINGS

BOEM will, in accordance with 40 CFR § 1506.6, hold public meetings to solicit comments 

on the Draft Programmatic EIS; the meetings are an additional avenue to submit comments during 

the review period. The meetings will provide the Secretary of the Interior with information from 

interested parties to help in the evaluation of potential effects of the proposed action. An 

announcement of the dates, times, and specific locations of the public hearings will be included in 

the NOA for this Draft Programmatic EIS. Public meetings are scheduled to be held in the cities

below, and additional information can be found on the project’s website at http://www.boem.gov/

GOM-G-G-PEIS/.

• Tampa, Florida;

• Houston, Texas;

• New Orleans, Louisiana;

• Biloxi, Mississippi;

• Mobile, Alabama; and

• Fort Walton Beach, Florida. 

6.6 REGULATORY FRAMEWORK

6.6.1 Federal Agencies and Regulations

Federal laws mandate the OCS leasing program (i.e., OCSLA) and certain environmental 

review processes (e.g., NEPA). The OCSLA establishes guidelines for the exploration of minerals 

(which, as defined by the OCSLA, is the process of searching for minerals, including geophysical 

surveys where magnetic, gravity, seismic, or other systems are used to detect or imply the presence 

of such minerals) on the OCS. Section 388 of the Energy Policy Act (EPAct) of 2005, Public Law

109-58, expanded the USDOI’s authority to issue leases, easements, and rights-of-way on the OCS 
Gulf of Mexico G&G Activities Programmatic EIS 6-13

for activities that produce energy from sources other than oil and gas (e.g., alternative energy 

projects). All of these actions are subject to the environmental review process under NEPA.

Several Federal regulations (e.g., CZMA, ESA, MSFCMA, and MMPA) establish specific 

consultation and coordination processes with Federal, State, and local agencies. In addition, 

activities and operations related to the OCS leasing process and G&G authorizations must comply 

with other Federal, State, and local laws and regulations, as appropriate. Table 1.1-1 (from 

Matthews and Cameron, 2016) lists the major Federal laws and regulations and Executive Orders 

that apply to the three program areas: (1) oil and gas; (2) renewable energy; and (3) marine 

minerals. Summaries of selected applicable Federal laws and regulations are provided in 

Appendix B. Additional information regarding the regulatory framework for activities in the GOM is

presented in Cameron and Matthews (2016).

6.6.2 State Agencies and Regulations

Federal agency activities that have reasonably foreseeable effects on coastal use or 

resources must be consistent to the maximum extent practicable with the enforceable policies of a 

coastal State’s federally approved coastal management program (CMP).

To ensure conformance with State CMP policies or enforceable guidelines, BOEM prepares 

a consistency determination for each proposed OCS lease sale. Through the designated State CZM 

agency, local land-use entities are provided an opportunity to comment on the OCS leasing 

program. Local land-use agencies also have the opportunity to comment directly to BOEM at any 

time, as well as during formal public comment periods related to the announcement of the Five-Year 

Program, Call for Information/Notice of Intent EIS scoping, public meetings for the Draft 

Programmatic EIS, and the Proposed Notice of Sale. Additional information regarding consistency 

determinations and CMPs is provided in Appendix B. 

6.7 CONSULTATION WITH THE NATIONAL MARINE FISHERIES SERVICE

On July 30, 2010, BOEM requested re-initiation of the existing ESA consultation for OCS oil 

and gas activities in the GOM, primarily to examine potential changes to the environmental baseline 

that may have resulted from the Deepwater Horizon explosion, oil spill, and response. The 

re-initiated consultation request initially focused on changes, either known or reasonably 

foreseeable, to the affected environment from the Deepwater Horizon explosion, oil spill, and 

response and considered those changes in light of current and future OCS leasing, exploration, 

development, production, decommissioning, and related activities in the GOM. The request was 

submitted on behalf of BOEM and BSEE, with BOEM serving as the lead agency.

BOEM and BSEE submitted the Draft Biological Assessment (BA) to NMFS on April 24, 

2012, that addressed all oil and gas activities in the GOM over a 10-year period (2012 to 2021) for 

technical assistance review, including G&G activities. On May 31, 2012, the NMFS provided BOEM 

with comments on the draft document via a letter. The Final BA, submitted by BOEM to NMFS in 

February 2013, included responses and clarifications related to NMFS’ comments on the draft 
6-14 Public Involvement and Agency Consultation and Coordination

document. The Final BA included all information necessary for NMFS to complete formal 

consultation and issue a single Biological Opinion to address all OCS oil and gas activities in the 

GOM, including G&G surveys.

The programmatic ESA consultation, to be completed in conjunction with this Programmatic 

EIS, will outline any additional consultations or other actions required at the individual permit level. 

Permit applications to BOEM for site-specific actions will need to meet the ESA requirements by 

falling under the umbrella of the Section 7 consultation completed for this Programmatic EIS or by 

completion of site-specific consultation for the proposed survey.

Pursuant to Section 305(b) of the Magnuson-Stevens Fishery Conservation and 

Management Act, Federal agencies are required to consult with NMFS on any action that may result 

in adverse effects to EFH. The NMFS published the final rule implementing the EFH provisions of 

the Magnuson-Stevens Fisheries Conservation and Management Act (50 CFR part 600) on 

January 17, 2002. Certain OCS oil- and gas-related activities authorized by BOEM may result in 

adverse effects to EFH and therefore require EFH consultation.

BOEM prepared a 2017-2022 EFH Assessment white paper, Essential Fish Habitat 

Assessment for the Gulf of Mexico, on behalf of BOEM and BSEE that describes the Gulf of Mexico 

OCS Region’s OCS proposed activities, analyzes the effects of the proposed activities on EFH, and 

identifies proposed mitigation measures (USDOI, BOEM, 2016). This Assessment was sent to 

NMFS on June 8, 2016, with a letter requesting formal consultation. This regional programmatic

EFH consultation will cover proposed GOM lease sales analyzed in the 2017-2022 Five-Year 

Program and the related activities (i.e., decommissioning and G&G). The EFH Assessment, the 

formalized conservation recommendations put forth by NMFS and accepted by BOEM/BSEE, or

NMFS concurrence will complete the EFH consultation. However, all agencies will continue to 

communicate for the duration of the EFH consultation (i.e., 2017-2022).
CHAPTER 7 

LITERATURE CITED

Gulf of Mexico G&G Activities Programmatic EIS 7-3 

7 LITERATURE CITED

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61 FR 6091. 1996. Executive Order 12989 – Economy and efficiency in government procurement 

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78 FR 24701. 2013. Endangered and threatened wildlife; 90-day finding on petitions to list the great 

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CHAPTER 8 

PREPARERS AND REVIEWERS

Gulf of Mexico G&G Activities Programmatic EIS 8-3 

8 PREPARERS AND REVIEWERS

8.1 BOEM, BSEE, AND NMFS PREPARERS

Kimberly Skrupky-Warshaw, BOEM, COR, Marine Biologist, MMPA and Protected Species

Tamara Arzt, BOEM, Environmental Protection Specialist, Protected Species

Stephanie Fiori, BOEM, NEPA Coordinator, Environmental Protection Specialist

Ronald Brinkman, BOEM, Senior Staff Geophysicist, Technologies & Oil and Gas Scenario

Deborah Epperson, Ph.D., BSEE, Protected Species Biologist

Donald (Tre) W. Glenn III, Ph.D., PE, BOEM ESA Lead, Marine Biologist, Protected Species

Gary Goeke, BOEM, Chief, Environmental Assessment Section

Andrea Heckman, BOEM, Environmental Scientist

Stanley Labak, BOEM, Marine Acoustician

Benjamin Laws, NMFS, Protected Species

Jill Lewandowski, Ph.D., BOEM, Chief, Division of Environmental Assessment

Beth Nord, BOEM, Senior Environmental Scientist

Trevis Olivier, BOEM, Environmental Scientist

Melissa Hearne, USDOI SOL, Attorney-Advisor

Pedro Meléndez-Arreaga, USDOI SOL, Attorney-Advisor

8.2 BOEM AND NMFS REVIEWERS

Bruce Baird, BOEM, Biologist

Kyle Baker, BOEM, Marine Biologist

Melissa Batum, BOEM, Geologist

Mark Belter, BOEM, Marine Biologist

Deborah Ben-David, NOAA, Attorney-Advisor, Office of the General Counsel

Jennifer Bosyk, BOEM, Biologist

Idrissa Boube, BOEM, Environmental Scientist

Perry Boudreaux, BOEM, Supervisor, Environmental Operations Unit 1

Megan Butterworth, BOEM, Biological Oceanographer

Brian Cameron, BOEM, Senior Environmental Scientist

Nicole Charpentier, BOEM, Protected Species Biologist

Joseph Christopher, BOEM, Regional Supervisor (retired), Office of Environment

Mary Cody, BOEM, Marine Biologist

Jennifer Culbertson, Ph.D., BOEM, Biological Oceanographer

David Dale, NMFS, EFH Coordinator, Southeast Region

Holli Ensz, BOEM, Air Quality Specialist

Stephanie Gambino, BOEM, Chief, Biological and Social Sciences Section

Leila Hatch, Ph.D., NOAA, Marine Ecologist, Stellwagen Bank National Marine Sanctuary, 

National Ocean Service

Allison Hernandez, NOAA, Biologist

Keely Hite, BOEM, Environmental Protection Specialist

Molly Holt, NOAA, General Counsel, Oceans and Coasts

Nicole Hughes, BOEM, Protected Species Biologist

Jack Irion, BOEM, Supervisor, Social Sciences Unit

Matthew Johnson, BOEM, Marine Biologist

Brian Jordan, Ph.D., BOEM, Marine Archaeologist

Agatha (Arie) Kaller, BOEM, Supervisor, Biological Sciences Unit
8-4 Preparers and Reviewers

Greg Kozlowski, BOEM, Deputy Regional Supervisor, Office of Environment

Jacob Levenson, BOEM, Marine Biologist

Kaye London, BOEM, Protected Species Biologist

Lissa Lyncker, BOEM, Supervisor, Environmental Assessment Section, Unit 1

Robert Martinson, BOEM, Environmental Protection Specialist

Charles McCreery, BOEM, Physical Scientist

Margaret Metcalf, BOEM, Chief, Physical and Chemical Sciences Section

Deborah Miller, BOEM, Technical Editor

Dave Moran, BOEM, Biologist

Mark Mueller, BOEM, Marine Ecologist

Barry Obiol, BOEM, Deputy Regional Director

Douglas Piatkowski, BOEM, Physical Scientist

Amy Scholik-Schlomer, NMFS, Fishery Biologist

Scott Sorset, BOEM, Marine Archaeologist

Susan Staehle, NMFS, ERT/NMFS HQ NEPA Program

Terri Thomas, BOEM, Regional Supervisor, Office of Environment

Vicki Wedell, NOAA, Acting Chief, Policy and Planning Division, Office of National Marine 

Sanctuaries, National Ocean Service

Toby Wraye, BOEM, Information Management Specialist

8.3 CONTRACTOR PREPARERS

Name Education/Expertise Contribution

CSA Ocean Sciences Inc.

Kimberley R. Olsen B.S. Oceanographic Technology; 

25 years of experience Project Manager

Melanie L. Cahill B.S. Marine Sciences; 10 years of 

experience

Deputy Project Manager, 

Co-author Chapter 4 

(Sargassum), Appendix E

Brian J. Balcom M.S. Marine Biology, B.S. Biology; 

29 years of experience Scientific Lead, Impacts Analyst

Alan D. Hart, Ph.D. Ph.D. Oceanography, B.S. Zoology; 

40 years of experience Scientific Advisor

Mark Fonseca, Ph.D.

Ph.D. Integrative Biology; M.S.

Environmental Sciences; 30 years 

of experience

Co-author Chapter 4

Neal Phillips, Ph.D. Ph.D. Ecology; M.S. Marine 

Studies; 30 years of experience

Co-author Chapter 4 (Deepwater 

Horizon Synthesis)

William R. Sloger, Jr.

M.S. Environmental Studies, M.S.

Civil Engineering, B.S. Civil 

Engineering; 20 years of experience

Co-author Chapters 1, 2, and 5

Mary Jo Barkaszi M.S. Biological Oceanography, B.S. 

Biology; 29 years of experience Co-author Chapter 2

Stephen T. Viada M.S. Biological Oceanography, B.S.

Zoology; 27 years of experience

Co-author Chapter 4 (Marine 

Mammals, Sea Turtles) and 

Appendix E

Bruce D. Graham

M.S. Biological Sciences, B.S. 

Biological Sciences; 30 years of 

experience

Scientific Reviewer Chapter 4 

(Birds, Benthic Habitats, Marine 

Protected Areas, and 

Sargassum)
Gulf of Mexico G&G Activities Programmatic EIS 8-5 

Name Education/Expertise Contribution

Robert B. Cady M.S. Oceanography, B.S. Marine 

Biology; 15 years of experience

Co-author Chapters 2 and 4 

(Marine and Coastal Birds, Other 

Marine Uses) and Appendix E

Robert (Bo) Douglas B.S. Civil Engineering, B.S. Marine 

Biology; 25 years of experience

Co-author Chapters 3 and 4 

(Marine Protected Areas and 

Benthic Habitats) and 

Appendix E

David B. Snyder

M.S. Marine Biology and 

Ichthyology, B.S. Zoology; 27 years 

of experience

Co-author Chapter 4 (Fisheries 

and EFH) 

Patrick W. Connelly M.S. Biology, B.A. Biology; 12 years 

of experience

Co-author Chapter 4 (Fish 

Resources and EFH, 

Commercial and Recreational 

Fisheries)

John M. Tiggelaar II M.S. Biology, B.A. Biology; 7 years 

of experience

Co-author Chapter 4 (Fish 

Resources and EFH, 

Commercial and Recreational 

Fisheries) and Appendix E

Edmund A. Hughes

Ph.D. Student, M.S. Oceanography, 

B.S. Marine Biology; 20 years of 

experience

Co-author Chapter 4 (Marine 

Protected Areas) and 

Appendix E

Luis M. Lagera, Jr., Ph.D.

Ph.D. Environmental Sciences 

(Ecology), M.S. Biological Sciences, 

B.S. Zoology; 20 years of 

experience

Co-author Appendix E

Kristen L. Metzger

M.A. Library and Information 

Science, B.A. Library Science/

Education; 36 years of experience

Administrative Record, Librarian

Brent R. Gore M.A. Geography, B.A. Geography; 8 

years of experience GIS Analyst

Natalie C. Kraft

M.E.M. Coastal Environmental 

Management, B.S. Marine 

Science/Biology; 5 years of 

experience

Technical Editor

Stephanie Urquhart 5 years of experience Support Services Manager

Deborah Murray 5 years of experience Document Processor 

ProBioSound, LLC

Thomas Carlson, Ph.D. Ph.D. Applied Acoustics/Bayesian 

Classification

Scientific Editor/Auditory/Impact 

Expert, Author Appendix J

Marine Acoustics, Inc.

Kathleen J. Vigness Raposa, 

Ph.D.

Ph.D. Landscape Ecology, M.S. 

Biological Oceanography, B.S. 

Education; 17 years of experience

Co-author Chapter 4 (Sea 

Turtles, Marine Mammals)

Adam S. Frankel, Ph.D.

Ph.D. Oceanography, M.S. Zoology, 

B.S. Biology; 27 years of 

experience

Co-author Chapter 4 (Acoustic 

Modeling Summary)

Cheryl Schroeder

M.S. Biological Oceanography, B.S. 

Marine Biology; 40 years of 

experience

Co-author Chapter 4 (Sea 

Turtles, Marine Mammals)
8-6 Preparers and Reviewers

Name Education/Expertise Contribution

Southeastern Archaeological Research, Inc. (SEARCH)

Jason M. Burns

M.A. History/Historical Archaeology, 

B.A. Anthropology; 15 years of 

experience

Project Manager; Co-author 

Chapter 4 (Archeological 

Resources)

Raymond Tubby

M.A. Maritime History, B.A. 

Anthropology; 14 years of 

experience

GIS Specialist; Co-author 

Chapter 4 (Archaeological 

Resources)

Environment & Ecology, Inc. (E&E)

Kirsten Shelly

M.S. Environmental/Resource 

Economics, B.A., Economics; 24

years of experience

Co-author Appendix E 

(Recreational Resources, 

Human Resources)

Antonio Riccobono

M.S. Civil/Geotechnical 

Engineering, B.S. Civil Engineering; 

28 years of experience

Author Chapter 4 (Human 

Resources and Land Use)

Southall Environmental Associates, Inc.

Brandon Southall, Ph.D.

Ph.D. Ocean Sciences, M.S. Marine 

Science, B.A. Environmental 

Biology, B.A. English; 17 years of 

experience

Author Appendix H

Virginia Wesleyan College

Soraya Moein Bartol, Ph.D.

Ph.D. Marine Science, M.S. Marine 

Science, B.A. Biology; 19 years of 

experience

Author Appendix I

Independent Consultant

John (Jack) Caldwell, Ph.D.

Ph.D. Geophysics and Geology, 

B.S. Mathematics; 35 years of 

experience

Co-author Chapter 3 and

Appendix F

The Department of the Interior Mission

The Department of the Interior protects and manages the Nation’s natural 

resources and cultural heritage; provides scientific and other information 

about those resources; and honors the Nation’s trust responsibilities or 

special commitments to American Indians, Alaska Natives, and affiliated 

island communities.

The Bureau of Ocean Energy Management Mission

The Bureau of Ocean Energy Management (BOEM) is responsible for 

managing development of U.S. Outer Continental Shelf energy and mineral 

resources in an environmentally and economically responsible way.