U.S. Department of the Interior

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

OCS EIS/EA

BOEM 2016-006

Gulf of Mexico OCS 

Oil and Gas Lease Sale: 2017

Central Planning Area Lease Sale 247

Draft Supplemental Environmental Impact Statement

U.S. Department of the Interior

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

OCS EIS/EA

BOEM 2016-006

Gulf of Mexico OCS 

Oil and Gas Lease Sale: 2017

Central Planning Area Lease Sale 247

Draft Supplemental Environmental Impact Statement

Author

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

Published by

New Orleans

February 2016



v 

COVER SHEET

Supplemental Environmental Impact Statement 

for 

Proposed Central Planning Area Lease Sale 247 

Draft (x) Final ( ) 

Type of Action: Administrative (x) Legislative ( )

Area of Potential Impact: Offshore Marine Environment and Coastal Parishes/Counties of 

Louisiana, Mississippi, Alabama, and Florida 

Agency Headquarters’ Contact Region Contacts

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 

Poojan Tripathi (355-C1)

U.S. Department of the Interior 

Bureau of Ocean Energy Management

45600 Woodland Road 

Sterling, VA 20166 

703-787-1843 

Beth Nord

504-736-2995 

Gary D. Goeke

504-736-3233 

ABSTRACT

This Supplemental Environmental Impact Statement (EIS) addresses one proposed Federal action: 

proposed Outer Continental Shelf (OCS) oil and gas Lease Sale 247 in the Central Planning Area (CPA) 

of the Gulf of Mexico, as scheduled in the Proposed Final Outer Continental Shelf Oil & Gas Leasing 

Program: 2012-2017 (Five-Year Program) (USDOI, BOEM, 2012a). 

This Supplemental EIS updates the baseline conditions and potential environmental effects of oil and 

natural gas leasing, exploration, development, and production in the CPA since publication of the “prior 

2012-2017 Gulf of Mexico EISs”: Gulf of Mexico OCS Oil and Gas Lease Sales: 2012-2017; Western 

Planning Area Lease Sales 229, 233, 238, 246, and 248; Central Planning Area Lease Sales 227, 231, 

235, 241, and 247, Final Environmental Impact Statement (2012-2017 WPA/CPA Multisale EIS) 

(USDOI, BOEM, 2012b); Gulf of Mexico OCS Oil and Gas Lease Sales: 2013-2014; Western Planning 

Area Lease Sale 233; Central Planning Area Lease Sale 231, Final Supplemental Environmental Impact 

Statement (WPA 233/CPA 231 Supplemental EIS) (USDOI, BOEM, 2013a); Gulf of Mexico OCS Oil 

and Gas Lease Sales: 2015-2017; Central Planning Area Lease Sales 235, 241, and 247, Final 

Supplemental Environmental Impact Statement (CPA 235/241/247 Supplemental EIS) (USDOI, BOEM, 

2014a); and Gulf of Mexico OCS Oil and Gas Lease Sales: 2016 and 2017; Central Planning Area Lease 

Sales 241 and 247; Eastern Planning Area Lease Sale 226, Final Supplemental Environmental Impact 

Statement (CPA 241/247 and EPA 226 Supplemental EIS). 

This Supplemental EIS analyzes the potential impacts of the CPA proposed action on sensitive 

coastal environments, offshore marine resources, and socioeconomic resources both onshore and offshore. 

It is important to note that this Supplemental 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.

The proposed action is considered to be major Federal action requiring an EIS. This document 

provides the following information in accordance with the National Environmental Policy Act (NEPA)
vi

and its implementing regulations, and it will be used in making decisions on the proposal. This 

Supplemental EIS is the final NEPA review conducted for proposed CPA Lease Sale 247. This document 

includes the purpose and background of the CPA proposed action, identification of the alternatives, 

description of the affected environment, and an analysis of the potential environmental impacts of the

CPA proposed action, alternatives, and associated activities, including proposed mitigating measures and 

their potential effects. Potential contributions to cumulative impacts resulting from activities associated 

with the CPA proposed action are also analyzed.

Hypothetical scenarios were developed on the levels of activities, accidental events (such as oil 

spills), and potential impacts that might result if the CPA proposed action is adopted. Activities and 

disturbances associated with the CPA proposed action on biological, physical, and socioeconomic 

resources are considered in the analyses.

Additional copies of this Supplemental EIS, the prior 2012-2017 Gulf of Mexico EISs, and the other 

referenced publications may be obtained from the Bureau of Ocean Energy Management, Gulf of Mexico 

OCS Region, Public Information Office (GM 250C), 1201 Elmwood Park Boulevard, Room 250, New 

Orleans, Louisiana 70123-2394, by telephone at 504-736-2519 or 1-800-200-GULF, or on BOEM’s 

website at http://www.boem.gov/nepaprocess/. 
Summary vii

SUMMARY

This Supplemental Environmental Impact Statement (EIS) addresses one proposed Federal action that 

offers for lease an area on the Gulf of Mexico Outer Continental Shelf (OCS) that may contain 

economically recoverable oil and gas resources. Under the Proposed Final Outer Continental Shelf Oil & 

Gas Leasing Program: 2012-2017 (Five-Year Program), five proposed lease sales are scheduled for the 

Central Planning Area (CPA) (USDOI, BOEM, 2012a). The remaining proposed CPA lease sale is 

proposed CPA Lease Sale 247, which is tentatively scheduled to be held in March 2017. At the 

completion of this Supplemental EIS process, a decision will be made on whether or how to proceed with 

proposed CPA Lease Sale 247. 

This Supplemental EIS updates the baseline conditions and potential environmental effects of oil and 

natural gas leasing, exploration, development, and production in the CPA since publication of the “prior 

2012-2017 Gulf of Mexico EISs”: Gulf of Mexico OCS Oil and Gas Lease Sales: 2012-2017; Western 

Planning Area Lease Sales 229, 233, 238, 246, and 248; Central Planning Area Lease Sales 227, 231, 

235, 241, and 247, Final Environmental Impact Statement (2012-2017 WPA/CPA Multisale EIS) 

(USDOI, BOEM, 2012b); Gulf of Mexico OCS Oil and Gas Lease Sales: 2013-2014; Western Planning 

Area Lease Sale 233; Central Planning Area Lease Sale 231, Final Supplemental Environmental Impact 

Statement (WPA 233/CPA 231 Supplemental EIS) (USDOI, BOEM, 2013a); Gulf of Mexico OCS Oil 

and Gas Lease Sales: 2015-2017; Central Planning Area Lease Sales 235, 241, and 247, Final 

Supplemental Environmental Impact Statement (CPA 235/241/247 Supplemental EIS) (USDOI, BOEM, 

2014a); and Gulf of Mexico OCS Oil and Gas Lease Sales: 2016 and 2017; Central Planning Area Lease 

Sales 241 and 247; Eastern Planning Area Lease Sale 226, Final Supplemental Environmental Impact 

Statement (CPA 241/247 and EPA 226 Supplemental EIS) (USDOI, BOEM, 2015a). 

This Supplemental EIS analyzes the potential impacts of the CPA proposed action on sensitive 

coastal environments, offshore marine resources, and socioeconomic resources both onshore and offshore. 

It is important to note that this Supplemental EIS was prepared using the best information that was 

publicly available at the time this 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, it was 

either acquired or in the event it was impossible or exorbitant to acquire the information, accepted 

scientific methodologies were applied in its place.

This summary section provides only a brief overview of the proposed CPA lease sale, alternatives, 

significant issues, potential environmental and socioeconomic effects, and proposed mitigating measures

contained in this Supplemental EIS. To obtain the full perspective and context of the potential 

environmental and socioeconomic impacts discussed, it is necessary to read the entire Supplemental EIS. 

Relevant discussions of specific topics can be found in the chapters and appendices of this Supplemental 

EIS as described below.

• Chapter 1, The Proposed Action, describes the purpose of and need for the proposed 

lease sale, the prelease process, postlease activities, and other OCS oil- and gasrelated activities.

• Chapter 2, Alternatives Including the Proposed Action, describes the environmental 

and socioeconomic effects of the proposed CPA lease sale and alternatives. It also 

discusses the potential mitigating measures to avoid or minimize impacts. 

• Chapter 3, Impact-Producing Factors and Scenario, describes the activities 

associated with a proposed lease sale and the OCS Program, and other foreseeable 

activities that could potentially affect the biological, physical, and socioeconomic 

resources of the Gulf of Mexico.

Chapter 3.1, Impact-Producing Factors and Scenario—Routine Operations, 

describes offshore infrastructure and routine activities (impact-producing 

factors) associated with a proposed lease sale that could potentially affect the 

biological, physical, and socioeconomic resources of the Gulf of Mexico. 
viii Central Planning Area Lease Sale 247 Supplemental EIS

Chapter 3.2, Impact-Producing Factors and Scenario—Accidental Events,

discusses potential accidental events (i.e., oil spills, losses of well control, 

vessel collisions, and spills of chemicals or drilling fluids) that may occur as 

a result of activities associated with a proposed lease sale.

Chapter 3.3, Cumulative Activities Scenario, describes past, present, and 

reasonably foreseeable future human activities, including non-OCS oil- and 

gas-related activities, as well as all OCS oil- and gas-related activities, that 

may affect the biological, physical, and socioeconomic resources of the Gulf 

of Mexico. 

• Chapter 4, Description of the Environment and Impact Analysis, describes the 

affected environment and provides analysis of the routine activities, accidental

events, and cumulative impacts of the CPA proposed action and the alternatives on 

environmental and socioeconomic resources of the Gulf of Mexico. 

Chapter 4.1, Proposed Central Planning Area Lease Sale 247, describes the

routine activities, accidental events, and cumulative impacts of the CPA 

proposed action and two alternatives to the CPA proposed action on the 

biological, physical, and socioeconomic resources of the Gulf of Mexico.. 

Chapter 4 also includes Chapter 4.2, Unavoidable Adverse Impacts of the 

Proposed Action; Chapter 4.3, Irreversible and Irretrievable Commitment of 

Resources; and Chapter 4.4, Relationship Between the Short-term Use of 

Man’s Environment and the Maintenance and Enhancement of Long-Term 

Productivity. 

• Chapter 5, Consultation and Coordination, describes the consultation and 

coordination activities with Federal, State, and local agencies and other interested 

parties that occurred during the development of this Supplemental EIS.

• Chapter 6, References Cited, is a list of literature cited throughout this Supplemental 

EIS.

• Chapter 7, Preparers, is a list of names of persons who were primarily responsible 

for preparing and reviewing this Supplemental EIS.

• Chapter 8, Glossary, is a list of definitions of selected terms used in this 

Supplemental EIS. 

• Appendix A, Memorandum of Agreement Between the Bureau of Ocean Energy 

Management and the National Park Service, outlines the responsibilities of BOEM 

and the National Park Service for this Supplemental EIS.

• Appendix B, Catastrophic Spill Event Analysis, is a technical analysis of a potential 

low-probability catastrophic event to assist BOEM in meeting the Council on 

Environmental Quality’s requirements for evaluating low-probability catastrophic 

events under NEPA and to provide the public and decisionmaker with an 

understanding of the potential impacts that could result should such an event occur. 

A catastrophic spill event is a low-probability event that is not reasonably expected to 

occur and not part of the CPA proposed action or reasonably foreseeable accidental 

events.

• Keyword Index is a list of descriptive terms and the pages on which they can be 

found in this Supplemental EIS.
Summary ix

Proposed Actions and Alternatives

The following alternatives were included for analysis in this Supplemental EIS.

Alternatives for Proposed Central Planning Area Lease Sale 247 

Alternative A—The Proposed Action (Preferred Alternative): This alternative would offer for lease 

all unleased blocks within the proposed CPA lease sale area for oil and gas operations (Figure 2-1), with 

the following exceptions:

(1) whole and portions of blocks deferred by the Gulf of Mexico Energy Security Act of 

2006; and

(2) blocks that are adjacent to or beyond the United States’ Exclusive Economic Zone in 

the area known as the northern portion of the Eastern Gap. 

The U.S. Department of the Interior (DOI) is conservative throughout the NEPA process and includes 

the total area within the CPA for environmental review even though the leasing of portions of the CPA 

(subareas or blocks) can be deferred during a Five-Year Program. 

The proposed CPA lease sale area encompasses about 63 million acres (ac) of the CPA’s 

66.45 million ac. As of January 2016, approximately 47.87 million ac of the proposed CPA lease sale 

area are currently unleased. This information is updated monthly and can be found on BOEM’s website 

at http://www.boem.gov/Gulf-of-Mexico-Region-Lease-Map/. The estimated amount of natural resources 

projected to be developed as a result of a proposed CPA lease sale is 0.460-0.894 billion barrels of oil 

(BBO) and 1.939-3.903 trillion cubic feet (Tcf) of gas (Table 3-1).

Alternative A has been identified as BOEM’s preferred alternative; however, this does not mean that 

a different alternative may not be selected in the Record of Decision. 

Alternative B—Exclude the Blocks Subject to the Topographic Features Stipulation: This alternative 

would offer for lease all unleased blocks within the proposed CPA lease sale area, as described for the 

proposed action (Alternative A), but it would exclude from leasing any unleased blocks subject to the 

Topographic Features Stipulation. The estimated amount of resources projected to be developed is 0.460-

0.894 BBO and 1.939-3.903 Tcf of gas. 

Alternative C—No Action: This alternative is the cancellation of the proposed CPA lease sale. If this 

alternative is chosen, the opportunity for development of the estimated 0.460-0.894 BBO and 

1.939-3.903 Tcf of gas that could have resulted from the proposed CPA lease sale would be precluded 

during the current 2012-2017 Five-Year Program, but it could again be contemplated as part of a future 

Five-Year Program. Any potential environmental impacts arising out of the proposed CPA lease sale 

would not occur, but activities associated with existing leases in the CPA would continue.

Mitigating Measures

Proposed lease stipulations and other mitigating measures designed to reduce or eliminate 

environmental risks and/or potential multiple-use conflicts between OCS operations and U.S. Department 

of Defense activities may be applied to the chosen alternative. Ten lease stipulations are proposed for a 

CPA proposed lease sale—the Topographic Features Stipulation; Live Bottom (Pinnacle Trend) 

Stipulation; Military Areas Stipulation; Evacuation Stipulation; Coordination Stipulation; Blocks South of 

Baldwin County, Alabama, Stipulation; Protected Species Stipulation; United Nations Convention on the 

Law of the Sea Royalty Payment Stipulation; Below Seabed Operations Stipulation; and the Stipulation 

on the Agreement between the United States of America and the United Mexican States Concerning 

Transboundary Hydrocarbon Reservoirs in the Gulf of Mexico. The United Nations Convention on the 

Law of the Sea Royalty Payment Stipulation is applicable to the proposed CPA lease sale even though it 

is not an environmental or military stipulation.

Application of lease stipulations will be considered by the Assistant Secretary of the Interior for Land 

and Minerals (ASLM). The inclusion of the stipulations as part of the analysis of the CPA proposed 

action does not ensure that the ASLM will make a decision to apply the stipulations to leases that may 

result from the proposed lease sale, nor does it preclude minor modifications in wording during 
x Central Planning Area Lease Sale 247 Supplemental EIS

subsequent steps in the prelease process if comments indicate changes are necessary or if conditions 

warrant. Any lease stipulations or mitigating measures to be included in a lease sale will be described in 

the Final Notice of Sale. Mitigating measures in the form of lease stipulations are added to the lease 

terms and are therefore enforceable as part of the lease. In addition, mitigations may be added to plans 

and/or permits for OCS oil- and gas-related activities. For more information on mitigating measures that 

are added at the postlease stage, refer to Appendix A (“Commonly Applied Mitigating Measures”) of the 

CPA 241/247 and EPA 226 Supplemental EIS, which is hereby incorporated by reference. A detailed 

listing of the current Gulf of Mexico OCS Region’s Notices to Lessees and Operators (NTLs) is available 

through BOEM’s Gulf of Mexico OCS Region’s website at http://boem.gov/Regulations/Notices-Lettersand-Information-to-Lessees-and-Operators.aspx or through the Region’s Public Information Office at 

504-736-2519 or 1-800-200-GULF.

Scenarios Analyzed

Offshore activities are described in the context of scenarios for the CPA proposed action (Chapter 

3.1) and for the OCS Program (Chapter 3.3). BOEM’s Gulf of Mexico OCS Region developed these 

scenarios to provide a framework for detailed analyses of potential impacts of the proposed CPA lease 

sale. The scenarios are presented as ranges of the amounts of undiscovered, unleased hydrocarbon 

resources estimated to be leased and discovered as a result of the CPA proposed action. The analyses are 

based on a traditionally employed range of activities (e.g., the installation of platforms, wells, and 

pipelines, and the number of helicopter operations and service-vessel trips) that would be needed to 

develop and produce the amount of resources estimated to be leased. 

The cumulative analyses (Chapters 4.1.) consider environmental and socioeconomic impacts that 

may result from the incremental contribution of the CPA proposed action when added to all past, present, 

and reasonably foreseeable future activities, including non-OCS oil- and gas-related activities such as 

import tankering and commercial fishing, as well as all OCS oil- and gas-related activities (OCS 

Program). The OCS Program scenario includes all activities that are projected to occur from past, 

proposed, and future lease sales during the 40-year analysis period (2012-2051). This includes projected 

activity from lease sales that have been held, but for which exploration or development has not yet begun 

or is continuing. In addition to human activities, impacts from natural occurrences, such as hurricanes, 

are analyzed.

Significant Issues

The major issues that frame the environmental analyses in this Supplemental EIS and in the prior 

2012-2017 Gulf of Mexico EISs are the result of concerns raised during years of scoping for the Gulf of 

Mexico OCS Program. Issues related to OCS oil and gas exploration, development, production, and 

transportation activities include the potential for oil spills, wetlands loss, air emissions, discharges, water 

quality degradation, trash and debris, structure and pipeline emplacement activities, platform removal, 

vessel and helicopter traffic, multiple-use conflicts, support services, population fluctuations, demands on 

public services, land-use planning, impacts to tourism, aesthetic interference, cultural impacts, 

environmental justice, and conflicts with State coastal zone management programs. Environmental 

resources and activities identified during the scoping process that warrant environmental analyses include 

air quality, water quality, coastal barrier beaches and associated dunes, wetlands, seagrass communities, 

live bottoms, topographic features, Sargassum communities, deepwater benthic communities, soft bottom 

benthic communities, marine mammals, sea turtles, diamondback terrapins, beach mice, coastal and 

marine birds, Gulf sturgeon, fish resources and essential fish habitat, commercial fisheries, recreational 

fishing, recreational resources, archaeological resources, and socioeconomic conditions. 

Other relevant issues include impacts from the Deepwater Horizon explosion, oil spill, and response;

impacts from past and future hurricanes on environmental and socioeconomic resources; and impacts on 

coastal and offshore infrastructure. During the past few years, both the Gulf Coast States and Gulf of 

Mexico oil and gas activities have been impacted by major hurricanes. The description of the affected 

environment (Chapter 4.1) includes impacts from these storms on the physical environment, biological 

environment, and socioeconomic activities and on OCS oil- and gas-related infrastructure. This 

Supplemental EIS also considers baseline data in the assessment of impacts from the CPA proposed 

action on the resources and the environment (Chapter 4.1). 
Summary xi

Impact Conclusions

The full analyses of the potential impacts of routine activities and accidental events associated with 

the CPA proposed action and the proposed action’s incremental contribution to the cumulative impacts

are described in Chapter 4.1. A summary of the potential impacts from the CPA proposed action on each 

environmental and socioeconomic resource and the conclusions of the analyses can be found below. 

Air Quality: Emissions of pollutants into the atmosphere from the routine activities associated with a 

CPA proposed action exceed the U.S. Environmental Protection Agency’s Significant Impact Levels 

(SILs) for annual nitrogen dioxide (NO2) (0.1 micron per cubic meter [μ/m3

]) and 24-hour particulate 

matter of 2.5 microns or less (PM2.5) (0.07 μ/m3

) in the Class I area. The results of the impacts equal 

annual NO2 (0.4 μ/m3

) and 24-hour PM2.5 (0.3 μ/m3) in the Class I area. However, onshore impacts on air 

quality from emissions from OCS oil- and gas-related activities are estimated to be within the Prevention 

of Significant Deterioration (PSD) Class II allowable increments. The background concentration and the 

impact concentration are below the National Ambient Air Quality Standards (NAAQS). While 

regulations are in place to reduce the risk of impacts from hydrogen sulfide (H2S) and while no H2Srelated deaths have occurred on the OCS, accidents involving high concentrations of H2S could result in 

deaths as well as environmental damage. Emissions from routine activities and accidental events 

associated with the CPA proposed action are not expected to occur at concentrations that would change 

onshore air quality classifications. 

Water Quality (Coastal and Offshore Waters): Impacts from routine activities associated with the 

CPA proposed action would be minimal if all existing regulatory requirements are met and because of the 

distance to shore of most routine activities. Coastal water impacts associated with routine activities 

include increases in turbidity resulting from pipeline installation and navigation canal maintenance, 

discharges of bilge and ballast water from support vessels, and run-off from shore-based facilities. 

Offshore water impacts associated with routine activities result from the discharge of drilling muds and 

cuttings, produced water, residual chemicals used during workovers, structure installation and removal, 

and pipeline placement. The discharge of drilling muds and cuttings causes temporary increased turbidity 

and changes in sediment composition. The discharge of produced water results in increased 

concentrations of some metals, hydrocarbons, and dissolved solids within an area of about 100 meters (m) 

(328 feet [ft]) adjacent to the point of discharge. Structure installation and removal and pipeline 

placement disturb the sediments and cause increased turbidity. In addition, offshore water impacts result 

from supply and service-vessel bilge and ballast water discharges. The potential impacts from accidental 

events (primarily oil spills) associated with the CPA proposed action is anticipated to be minimal.

Coastal Barrier Beaches and Associated Dunes: Routine activities associated with the CPA proposed 

action, such as increased vessel traffic, maintenance dredging of navigation canals, and pipeline

installation, is not expected to cause significant impacts. Such impacts would be expected to be restricted 

to temporary and localized disturbances and not deleteriously affect barrier beaches and associated dunes. 

Indirect impacts from routine activities are negligible and indistinguishable from direct impacts of inshore 

activities. The potential impacts from accidental events (primarily oil spills) associated with the CPA 

proposed action are anticipated to be minor. Should a spill (other than a low-probability catastrophic 

spill, which is not part of the CPA proposed action and not likely expected to occur) contact a barrier 

beach, oiling is expected to be light and sand removal during cleanup activities minimized. No significant 

long-term impacts to the physical shape and structure of barrier beaches and associated dunes are 

expected to occur as a result of the CPA proposed action. 

Wetlands: Routine activities associated with the CPA proposed action are expected to be small, 

localized, and temporary due to the small length of projected onshore pipelines, the minimal contribution 

to the need for maintenance dredging, the disposal of OCS wastes, and the mitigating measures that 

would be used to further reduce these impacts. Indirect impacts from wake erosion and saltwater 

intrusion are expected to result in low impacts that are indistinguishable from direct impacts from inshore 

activities. Accidental disturbances resulting from the CPA proposed action, mainly oil spills, have the 

potential to cause plant mortality and permanent loss of wetlands of the CPA. The potential impacts from 

accidental events (primarily oil spills originating in the OCS) would have a low probability of contacting 

and damaging wetlands along the Gulf Coast. Overall, impacts to wetland habitats from an oil spill 

associated with activities related to the CPA proposed action would be expected to be small and 

temporary because of the small contribution of the CPA proposed action to the total OCS activity, the 
xii Central Planning Area Lease Sale 247 Supplemental EIS

distance of most of the activity from shore, the weathering of spilled oil, and the ability of vegetation to 

recover from exposure to crude oil. 

Seagrass Communities: Turbidity impacts from pipeline installation and maintenance dredging 

associated with the CPA proposed action would be temporary and localized. The increment of impacts 

from service-vessel transit associated with the CPA proposed action would be minimal. Should an oil 

spill occur near a seagrass community, impacts from the spill and cleanup would be considered short term 

in duration and minor in scope. Close monitoring and restrictions on the use of bottom-disturbing 

equipment to clean up the spill would be needed to avoid or minimize those impacts. 

Live Bottoms (Pinnacle Trend and Low Relief): The combination of its depth (200-400 ft; 60-120 m), 

separation from sources of impacts as mandated by the Live Bottom (Pinnacle Trend) Stipulation and 

through site-specific seafloor reviews of proposed activity, and a community adapted to sedimentation 

makes damage to the ecosystem unlikely from routine activities associated with the CPA proposed action. 

In the unlikely event that oil from a subsurface spill would reach the biota of these communities, the 

effects would be primarily sublethal for adult sessile biota. Although unlikely, high concentrations of 

surface oil have the potential to impact live bottoms. A recent publication of data related to the apparent 

mixing of surface waters to a depth of at least 75 m (246 ft) in the Pinnacle Trend area during the passage 

of Tropical Storm Bonnie in July 2010 (Silva et al., 2015) documented acute impacts to gorgonians and 

black corals, seemingly caused by acute exposure to high concentrations of surface oil and/or dispersant

(presumably sourced from the Deepwater Horizon). The submerged oil and/or dispersant likely reached 

the live bottom features in relatively undiluted concentrations, leading to lethal and sublethal impacts.

Topographic Features: The routine activities associated with the CPA proposed action that would 

impact topographic feature communities include anchoring, infrastructure and pipeline emplacement, 

infrastructure removal, drilling discharges, and produced-water discharges. However, adherence to the 

proposed Topographic Features Stipulation would make damage to the ecosystem unlikely. Contact with

accidentally spilled oil would cause lethal and sublethal effects in benthic organisms, but the oiling of 

benthic organisms is not likely because of the small area of the banks, the scattered occurrence of spills, 

the depth of the features, and because the proposed Topographic Features Stipulation, if applied, would 

keep subsurface sources of spills away from the immediate vicinity of topographic features. Although 

very unlikely, the results of a new study suggest that high concentrations of surface oil, when combined 

with extreme mixing from storm events, have the potential to impact topographic features. A recent study 

documented the apparent mixing of surface waters to a depth similar to that of the topographic features 

during the passage of Tropical Storm Bonnie (Silva et al., 2015). This apparent mixing appears to have

resulted in surface oil reaching the benthic community of mesophotic reefs in concentrations high enough 

to damage the corals. Damage was determined through the detection of necrotic tissues, biofilms, and 

chemical analysis. Many of these reefs have similar communities and are found at similar depths, as are 

most topographic features. As such, if a large storm event did occur in the Gulf and it passed over a 

topographic feature while there was a substantial amount of surface oil present, impacts to the benthic 

community could be expected.

Sargassum Communities: The impacts that are associated with the CPA proposed action are expected 

to have only minor effects to a small portion of the Sargassum community as a whole. Limited portions 

of the Sargassum community could suffer mortality if it contacts spilled oil or cleanup activities. The 

Sargassum community lives in pelagic waters with generally high water quality and would be resilient to 

the minor effects predicted. It has a yearly cycle that promotes quick recovery from impacts. No 

measurable impacts are expected to the overall population of the Sargassum community from the CPA 

proposed action. 

Chemosynthetic and Nonchemosynthetic Deepwater Benthic Communities: Chemosynthetic and 

nonchemosynthetic communities are susceptible to physical impacts from structure placement, anchoring, 

and pipeline installation associated with the CPA proposed action. However, the protective measures 

provided as guidance by NTL 2009-G40 greatly reduce the risk of these physical impacts by clarifying 

the measures that must be taken to ensure avoidance of potential chemosynthetic communities and, by 

consequence, avoidance of other hard bottom communities. Even in situations where substantial burial of 

typical benthic infaunal communities occurred, recolonization by populations from widespread, 

neighboring, soft bottom substrate would be expected over a relatively short period of time for all size 

ranges of organisms. Potential accidental events associated with the CPA proposed action are expected to 

cause little damage to the ecological function or biological productivity of the widespread, low-density 

chemosynthetic communities and the widespread, typical, deep-sea benthic communities. 
Summary xiii

Soft Bottom Benthic Communities: The routine activities associated with the CPA proposed action 

that would impact soft bottoms generally occur within a few hundred meters of platforms, and the greatest 

impacts are seen close to the platform communities. Accidental disturbances to soft bottom benthic 

communities can result from oil spills associated with OCS oil- and gas-related activities. Oil deposited 

on soft bottom benthic communities could result in changes to local community structure. Although 

localized impacts to comparatively small areas of the soft bottom benthic communities would occur, the 

CPA proposed action is not expected to adversely impact the entire soft bottom environment because the 

locally impacted areas are extremely small compared with the entire seafloor of the Gulf of Mexico and 

because the soft bottom benthic communities are ubiquitous throughout the Gulf of Mexico. 

Marine Mammals: Routine events (i.e., vessel traffic, degradation of water quality from operational 

discharges, and marine debris from service vessels and OCS oil- and gas-related facilities) related to a the 

CPA proposed action are not expected to have adverse effects on the quality and productivity of any 

marine mammal species or population stocks in the Gulf of Mexico. Impacts from operations and 

equipment noise, vessel and aircraft noise, structure removals, and geological and geophysical activity 

could negatively impact marine mammals by increasing noise levels, as well as having the potential to 

harm or harass marine mammal species. These activities, when mitigated, are not expected to have longterm impacts on the quality and productivity of any marine mammal species or population stocks. 

Characteristics of impacts from accidental events depend on chronic or acute exposure from accidental 

events resulting in harassment, harm, or mortality to marine mammals. Accidental disturbances resulting 

from the CPA proposed action, including oil spills and spill-response activities, have the potential to have 

adverse, but not significant, impacts on marine mammal populations of the CPA. 

Sea Turtles: Routine activities resulting from the CPA proposed action have the potential to harm sea 

turtles, although this potential is unlikely to rise to a level of significance due to the activity already 

present in the Gulf of Mexico and due to mitigating measures that are in place. Accidental events, 

including accidental oil spills and spill-response activities, associated with the CPA proposed action have 

the potential to impact small to large numbers of sea turtles. Populations of sea turtles in the Gulf of 

Mexico may be exposed to residuals of oils spilled as a result of the CPA proposed action during their 

lifetimes. While chronic or acute exposure from accidental events may result in the harassment, harm, or 

mortality of sea turtles, in the most likely scenarios, exposure to hydrocarbons persisting in the sea 

following the dispersal of an oil slick are expected to most often result in sublethal impacts (e.g., 

decreased health and/or reproductive fitness and increased vulnerability to disease) to sea turtles. The 

incremental contribution of the CPA proposed action would not be likely to result in a significant 

incremental impact on sea turtles within the CPA; in comparison, non-OCS energy-related activities, such 

as overexploitation, commercial fishing, and pollution, have historically proved to be a greater threat to 

sea turtles. 

Diamondback Terrapins: The routine activities of the CPA proposed action are unlikely to have 

significant adverse effects on the size and recovery of terrapin species or populations in the Gulf of 

Mexico. Impacts on diamondback terrapins from smaller accidental events are likely to affect individual 

diamondback terrapins in the spill area, but they are unlikely to rise to the level of population effects (or 

significance) given the probable size and scope of such spills. Due to the distance of most terrapin habitat 

from offshore OCS energy-related activities, impacts associated with activities occurring as a result of the 

CPA proposed action are not expected to impact terrapins or their habitat. The incremental effect of the 

CPA proposed action on diamondback terrapin populations is not expected to be significant when 

compared with historic and current non-OCS energy-related activities, such as habitat loss, 

overharvesting, crabbing, and fishing. 

Beach Mice: An impact from the consumption of beach trash and debris associated with the CPA

proposed action on the Alabama, Choctawhatchee, St. Andrew, and Perdido Key beach mice is possible 

but unlikely. While potential spills that could result from the CPA proposed action are not expected to 

contact beach mice or their habitats, if either or both of these organisms and locations were to experience 

large-scale oiling, beach mice could go extinct. Also, if all personnel are not thoroughly trained, oil-spill 

response and cleanup activities could have a significant impact to the beach mice and their habitat. 

Coastal and Marine Birds: The majority of impacts resulting from routine activities associated with 

the CPA proposed action on avian species (Endangered Species Act listed and nonlisted) are expected to 

be adverse, but not significant. These impacts include behavioral effects, exposure to or intake of OCS

oil- and gas-related contaminants and discarded debris, disturbance-related impacts, and displacement of 

birds from habitats that are destroyed, altered, or fragmented, making these areas otherwise unavailable. 
xiv Central Planning Area Lease Sale 247 Supplemental EIS

Impacts from potential oil spills associated with the CPA proposed action and the effects related to oilspill cleanup are expected to be adverse, but not significant. Oil spills, irrespective of size, can result in 

some mortality as well as sublethal, chronic short- and long-term effects, in addition to potential impacts 

to food resources. The effect of cumulative activities on coastal and marine birds is expected to result in 

discernible changes to avian species’ composition, distribution, and abundance. The incremental 

contribution of the CPA proposed action to cumulative impacts is expected to be adverse, but not 

significant, because it may seriously alter avian species’ composition and abundance due to reductions in 

the overall carrying capacity of disturbed habitats, and possibly to the availability, abundance, and 

distribution of preferred food resources.

Gulf Sturgeon: Routine activities associated with the CPA proposed action, such as the installation of 

pipelines, maintenance dredging, potential vessel strikes, and nonpoint-source runoff from onshore 

facilities, would cause negligible impacts due to the distance of the Gulf sturgeon habitat and life cycles 

from most activities related to the CPA proposed action and would not deleteriously affect Gulf sturgeon. 

Indirect impacts from routine activities to inshore habitats are negligible and indistinguishable from direct 

impacts of inshore activities and are further reduced through mitigations and regulations. The potential 

impacts from accidental events, mainly oil spills associated with the CPA proposed action, are anticipated 

to be minimal. Because of the floating nature of oil, reduced toxicity through weathering (offshore 

dispersant treatment), and the small tidal range of the Gulf of Mexico, oil spills alone would typically 

have very little impact on benthic feeders such as the Gulf sturgeon. The incremental contribution of the 

CPA proposed action to the cumulative impact is negligible. 

Fish Resources and Essential Fish Habitat: Fish resources and essential fish habitat could be 

impacted by coastal environmental degradation potentially caused by canal dredging, increases in 

infrastructure, and inshore spills and marine environmental degradation possibly caused by pipeline

trenching, offshore discharges, and offshore spills. Impacts of routine dredging and discharges are 

localized in time and space and are regulated by Federal and State agencies through permitting processes; 

therefore, there would be minimal impact to fish resources and essential fish habitat from these routine 

activities associated with the CPA proposed action. Accidental events that could impact fish resources 

and essential fish habitat include oil or chemical spills. If a spill were to occur as a result of the CPA

proposed action and if it was proximate to mobile fishes, the impacts of the spill would depend on 

multiple factors, including the amount spilled, the areal extent of the spill, the distance of the spill from 

particular essential fish habitats (e.g., nursery habitats), and the type and toxicity of oil spilled. Much of 

the sensitive essential fish habitat would have decreased effects from oil spills because of the depths many 

are found and because of the distance that these low-probability spills would occur from many of the 

essential fish habitats (due to stipulations, NTLs, Magnuson-Stevens Fishery Conservation and 

Management Act compliance, etc.). If there is an effect of an oil spill on fish resources in the Gulf of 

Mexico, it is expected to cause a minimal decrease in standing stocks of any population. This is because 

most spill events would be localized, therefore affecting a small portion of fish populations.

Commercial Fisheries: Routine activities in the CPA, such as seismic surveys and pipeline trenching, 

would cause short-term localized disturbances that minimally impact commercially valuable fish species 

and associated essential fish habitat. Indirect impacts from routine activities to inshore habitats are 

negligible and indistinguishable from direct impacts of inshore activities on commercial fisheries. The 

potential impacts from accidental events, such as an oil spill, associated with the CPA proposed action are 

anticipated to be minimal. Commercial fishermen are anticipated to avoid the area of an oil spill. Large 

spills may impact commercial fisheries by area closures. The extent of impact depends on the areal extent 

and length of the closure. The impact of spills on catch or value of catch would depend on the volume 

and location (i.e., distance from shore) of the spill, as well as the physical properties of the oil spilled.

Recreational Fishing: There could be minor and short-term, space-use conflicts with recreational 

fishermen during the initial phases of the CPA proposed action. The CPA proposed action could also 

lead to low-level environmental degradation of fish habitat, which would also negatively impact 

recreational fishing activity. However, these minor negative effects would be offset by the beneficial role 

that oil platforms serve as artificial reefs for fish populations. An oil spill would likely lead to 

recreational fishing closures the CPA proposed action and not likely expected (e.g., the Deepwater 

Horizon oil spill), oil spills should not affect recreational fishing to a large degree due to the likely 

availability of substitute fishing sites in neighboring regions.

Recreational Resources: Routine OCS oil- and gas-related activities can cause minor disturbances to 

recreational resources, particularly beaches, through increased levels of noise, debris, and rig visibility. 
Summary xv 

The oil spills most likely to result from the CPA proposed action would be small, of short duration, and 

not likely to impact Gulf Coast recreational resources. Should an oil spill occur and contact a beach area 

or other recreational resource, it would cause some disruption during the impact and cleanup phases of the 

spill. However, except for a low-probability catastrophic spill, which is not part of the CPA proposed 

action and not likely expected (e.g., the Deepwater Horizon oil spill), these effects are likely to be small 

in scale and of short duration. 

Archaeological Resources (Historic and Prehistoric): The greatest potential impact to an 

archaeological resource as a result of routine activities associated with the CPA proposed action would 

result from direct contact between an offshore activity (e.g., platform installation, drilling rig 

emplacement, structure removal or site clearance operation, and dredging or pipeline project) and a 

historic or prehistoric site. The archaeological survey and archaeological clearance of sites, where 

required prior to an operator beginning OCS oil- and gas-related activities on a lease, are expected to be 

highly effective at identifying possible offshore archaeological sites; however, should such contact occur, 

there would be localized damage to or loss of significant and/or unique archaeological information. It is 

expected that coastal archaeological resources would be protected through the review and approval 

processes of the various Federal, State, and local agencies involved in permitting onshore activities.

It is not very likely that a large oil spill would occur and contact coastal prehistoric or historic 

archaeological sites from accidental events associated with the CPA proposed action. Should a spill 

contact a prehistoric archaeological site, damage might include loss of radiocarbon-dating potential, direct 

impact from oil-spill cleanup equipment, and/or looting resulting in the irreversible loss of unique or 

significant archaeological information. The major effect from an oil-spill impact on coastal historic 

archaeological sites would be visual contamination, which, while reversible, could result in additional 

impacts to fragile cultural materials from the cleaning process.

Land Use and Coastal Infrastructure: The CPA proposed action would not require additional coastal 

infrastructure, with the exception of possibly one new gas processing facility and one new pipeline

landfall. As a result, there may be increased demand for waste disposal services; however, this would 

minimally affect land use and infrastructure because waste disposal would occur at facilities already 

designated for such purposes and enough spare capacity exists at these facilities in the GOM region 

(Dismukes, official communication, 2015). The existing oil and gas infrastructure is expected to be 

sufficient to handle development associated with the CPA proposed action. There may be some 

expansion at current facilities, but the land in the analysis area is sufficient to handle such development. 

There is also sufficient land to construct a new gas processing plant in the analysis area, should it be 

needed. Accidental events, such as oil or chemical spills and vessel collisions, would have no effects on 

land use. Coastal or nearshore spills, as well as vessel collisions, could have short-term adverse effects on 

coastal infrastructure, requiring cleanup of any oil or chemicals spilled. 

Demographics: The CPA proposed action is projected to minimally affect the demography of the 

analysis area. Population impacts from the CPA proposed action are projected to be minimal (<1% of 

total population) for any economic impact area in the Gulf of Mexico region. The baseline population 

patterns and distributions, as projected and described in Chapter 4.1.1.23.2 are expected to remain 

unchanged as a result of the CPA proposed action. Accidental events associated with the CPA proposed 

action, such as oil or chemical spills and vessel collisions, would likely have no effects on the 

demographic characteristics of the Gulf coastal communities.

Economic Factors: The CPA proposed action would not cause employment effects >1 percent in any 

Economic Impact Area along the Gulf Coast. Most of the employment related to the CPA proposed 

action is expected to occur in the coastal areas of Louisiana and Texas. The demand would be met 

primarily with the existing population and labor force. 

Environmental Justice: Environmental justice implications arise indirectly from onshore activities 

conducted in support of OCS oil and gas exploration, development, and production. Because the onshore 

infrastructure support system for the OCS oil- and gas-related industry (and its associated labor force) is 

highly developed, widespread, and has operated for decades within a heterogeneous Gulf of Mexico 

population, impacts of routine activities resulting from the CPA proposed action are not expected to have 

disproportionately high or adverse environmental or health effects on minority or low-income people. 

Accidental disturbances resulting from the CPA proposed action, including oil spills, vessel collision, and 

chemical/drilling fluids spills, have the potential to negatively affect minority and low-income 

populations through direct exposure to oil, dispersants, degreasers, and other chemicals that can affect 

human health; decreased access to natural resources due to environmental damages, fisheries closures, or 
xvi Central Planning Area Lease Sale 247 Supplemental EIS

wildlife contamination; and proximity to onshore disposal sites used in support of oil and chemical spill 

cleanup efforts. The CPA proposed action would help to maintain ongoing levels of activity, which may 

or may not result in the expansion of existing infrastructure. For a detailed discussion of scenario 

projections and the potential for expansion at existing facilities and/or construction of new facilities, refer 

to Chapter 3.1.2. 
Table of Contents xvii

TABLE OF CONTENTS

Page

SUMMARY ................................................................................................................................................ vii

LIST OF FIGURES ................................................................................................................................... xxi

LIST OF TABLES ................................................................................................................................... xxiii

ABBREVIATIONS AND ACRONYMS ................................................................................................. xxv

CONVERSION CHART ......................................................................................................................... xxix

1. THE PROPOSED ACTION ................................................................................................................ 1-3

1.1. Purpose of and Need for the Proposed Action ......................................................................... 1-3

1.2. Description of the Proposed Action ......................................................................................... 1-5

1.3. Regulatory Framework ............................................................................................................ 1-6

1.3.1. Recent BOEM/BSEE Rule Changes ......................................................................... 1-7

1.3.1.1. Recent and Ongoing Regulatory Reform and GovernmentSponsored Research ................................................................................. 1-8

1.3.1.2. Recent and Ongoing Industry Reform and Research ............................... 1-9

1.4. Prelease Process ....................................................................................................................... 1-9

1.5. Postlease Activities ................................................................................................................ 1-12

1.6. Other OCS Oil- and Gas-Related Activities .......................................................................... 1-13

2. ALTERNATIVES INCLUDING THE PROPOSED ACTION .......................................................... 2-3

2.1. Supplemental EIS NEPA Analysis .......................................................................................... 2-3

2.2. Alternatives, Mitigating Measures, and Issues ........................................................................ 2-3

2.2.1. Alternatives ............................................................................................................... 2-3

2.2.1.1. Alternatives for Proposed Central Planning Area Lease Sale 247 ........... 2-3

2.2.2. Mitigating Measures .................................................................................................. 2-4

2.2.2.1. Proposed Mitigating Measures Analyzed ................................................ 2-5

2.2.2.2. Existing Mitigating Measures .................................................................. 2-5

2.2.3. Issues ......................................................................................................................... 2-6

2.2.3.1. Issues to be Analyzed ............................................................................... 2-6

2.2.3.2. Issues Considered but Not Analyzed ....................................................... 2-7

2.3. Proposed Central Planning Area Lease Sale 247 ..................................................................... 2-8

2.3.1. Alternative A—The Proposed Action ....................................................................... 2-8

2.3.1.1. Description ............................................................................................... 2-8

2.3.1.2. Summary of Impacts ................................................................................ 2-9

2.3.1.3. Mitigating Measures............................................................................... 2-10

2.3.1.3.1. Topographic Features Stipulation ....................................... 2-10

2.3.1.3.2. Live Bottom (Pinnacle Trend) Stipulation .......................... 2-11

2.3.1.3.3. Military Areas Stipulation ................................................... 2-11

2.3.1.3.4. Evacuation Stipulation ........................................................ 2-11

2.3.1.3.5. Coordination Stipulation ..................................................... 2-12

2.3.1.3.6. Blocks South of Baldwin County, Alabama, 

Stipulation ........................................................................... 2-12

2.3.1.3.7. Protected Species Stipulation .............................................. 2-12
xviii Central Planning Area Lease Sale 247 Supplemental EIS

2.3.1.3.8. United Nations Convention on the Law of the Sea 

Royalty Payment Stipulation ............................................... 2-12

2.3.1.3.9. Below Seabed Operations Stipulation ................................. 2-12

2.3.1.3.10. Stipulation on the Agreement between the United 

States of America and the United Mexican States 

Concerning Transboundary Hydrocarbon Reservoirs 

in the Gulf of Mexico .......................................................... 2-13

2.3.2. Alternative B—Exclude the Unleased Blocks Subject to the Topographic 

Features Stipulation ................................................................................................. 2-13

2.3.2.1. Description ............................................................................................. 2-13

2.3.2.2. Summary of Impacts .............................................................................. 2-13

2.3.3. Alternative C—No Action....................................................................................... 2-14

2.3.3.1. Description ............................................................................................. 2-14

2.3.3.2. Summary of Impacts .............................................................................. 2-14

3. IMPACT-PRODUCING FACTORS AND SCENARIO .................................................................... 3-3

3.1. Impact-Producing Factors and Scenario—Routine Operations ............................................... 3-3

3.1.1. Offshore Impact-Producing Factors and Scenario .................................................... 3-3

3.1.1.1. Resource Estimates and Timetables ......................................................... 3-4

3.1.1.1.1. Proposed Action .................................................................... 3-4

3.1.1.1.2. OCS Program ........................................................................ 3-5

3.1.1.2. Exploration and Delineation .................................................................... 3-6

3.1.1.2.1. Seismic Surveying Operations .............................................. 3-6

3.1.1.2.2. Exploration and Delineation Plans and Drilling .................... 3-6

3.1.1.3. Development and Production ................................................................... 3-8

3.1.1.4. Operational Waste Discharged Offshore................................................ 3-12

3.1.1.5. Air Emissions ......................................................................................... 3-13

3.1.1.6. Noise ...................................................................................................... 3-14

3.1.1.7. Major Sources of Oil Inputs in the Gulf of Mexico ............................... 3-14

3.1.1.8. Offshore Transport ................................................................................. 3-14

3.1.1.9. Safety Issues ........................................................................................... 3-14

3.1.1.10. Decommissioning and Removal Operations .......................................... 3-15

3.1.2. Coastal Impact-Producing Factors and Scenario ..................................................... 3-15

3.1.2.1. Coastal Infrastructure ............................................................................. 3-15

3.1.2.2. Discharges and Wastes ........................................................................... 3-17

3.2. Impact-Producing Factors and Scenario—Accidental Events ............................................... 3-18

3.2.1. Oil Spills .................................................................................................................. 3-18

3.2.1.2. Past OCS Spills ...................................................................................... 3-18

3.2.1.3. Characteristics of OCS Oil ..................................................................... 3-19

3.2.1.4. Overview of Spill Risk Analysis ............................................................ 3-20

3.2.1.5. Risk Analysis for Offshore Spills ≥1,000 bbl ........................................ 3-20

3.2.1.6. Risk Analysis for Offshore Spills <1,000 bbl ........................................ 3-21

3.2.1.7. Risk Analysis for Coastal Spills ............................................................. 3-22

3.2.1.8. Risk Analysis by Resource..................................................................... 3-22

3.2.1.9. Spill Response ........................................................................................ 3-22

3.2.2. Losses of Well Control ............................................................................................ 3-25

3.2.3. Pipeline Failures ...................................................................................................... 3-26

3.2.4. Vessel Collisions ..................................................................................................... 3-26

3.2.5. Chemical and Drilling-Fluid Spills ......................................................................... 3-26
Table of Contents xix

3.3. Cumulative Activities Scenario ............................................................................................. 3-27

3.3.1. OCS Program .......................................................................................................... 3-27

3.3.2. State Oil and Gas Activity ....................................................................................... 3-27

3.3.3. Other Major Factors Influencing Offshore Environments ...................................... 3-29

3.3.3.1. Dredged Material Disposal .................................................................... 3-29

3.3.3.2. OCS Sand Borrowing ............................................................................. 3-30

3.3.3.3. Marine Transportation ............................................................................ 3-31

3.3.3.4. Military Activities .................................................................................. 3-31

3.3.3.5. Artificial Reefs and Rigs-to-Reefs Development ................................... 3-32

3.3.3.6. Offshore Liquefied Natural Gas Projects and Deepwater Ports ............. 3-32

3.3.3.7. Development of Gas Hydrates ............................................................... 3-33

3.3.3.8. Renewable Energy and Alternative Use................................................. 3-33

3.3.4. Other Major Factors Influencing Coastal Environments ......................................... 3-33

3.3.4.1. Sea-Level Rise and Subsidence ............................................................. 3-33

3.3.4.2. Mississippi River Hydromodification .................................................... 3-33

3.3.4.3. Maintenance Dredging and Federal Channels ....................................... 3-34

3.3.4.4. Coastal Restoration Programs ................................................................ 3-34

3.3.5. Natural Events and Processes .................................................................................. 3-34

3.3.6. Non-OCS Oil- and Gas-Related Oil Spills .............................................................. 3-34

4. DESCRIPTION OF THE ENVIRONMENT AND IMPACT ANALYSIS ........................................ 4-3

4.1. Proposed Central Planning Area Lease Sale 247 ..................................................................... 4-3

4.1.1. Alternative A—The Proposed Action ....................................................................... 4-8

4.1.1.1. Air Quality ............................................................................................... 4-8

4.1.1.2. Water Quality ......................................................................................... 4-11

4.1.1.2.1. Coastal Waters ..................................................................... 4-11

4.1.1.2.2. Offshore Waters .................................................................. 4-14

4.1.1.3. Coastal Barrier Beaches and Associated Dunes ..................................... 4-17

4.1.1.4. Wetlands ................................................................................................. 4-21

4.1.1.5. Seagrass Communities........................................................................... 4-26

4.1.1.6. Live Bottoms (Pinnacle Trend and Low Relief) .................................... 4-28

4.1.1.7. Topographic Features ............................................................................. 4-31

4.1.1.8. Sargassum Communities ........................................................................ 4-35

4.1.1.9. Chemosynthetic Deepwater Benthic Communities ................................ 4-39

4.1.1.10. Nonchemosynthetic Deepwater Benthic Communities .......................... 4-43

4.1.1.11. Soft Bottom Benthic Communities ........................................................ 4-47

4.1.1.12. Marine Mammals ................................................................................... 4-50

4.1.1.13. Sea Turtles .............................................................................................. 4-55

4.1.1.14. Diamondback Terrapins ......................................................................... 4-59

4.1.1.15. Beach Mice ............................................................................................ 4-62

4.1.1.16. Coastal and Marine Birds ....................................................................... 4-64

4.1.1.17. Gulf Sturgeon ......................................................................................... 4-69

4.1.1.18. Fish Resources and Essential Fish Habitat ............................................. 4-72

4.1.1.19. Commercial Fisheries............................................................................. 4-76

4.1.1.20. Recreational Fishing............................................................................... 4-79

4.1.1.21. Recreational Resources .......................................................................... 4-81

4.1.1.22. Archaeological Resources ...................................................................... 4-84

4.1.1.22.1. Historic Archaeological Resources ..................................... 4-84

4.1.1.22.2. Prehistoric Archaeological Resources ................................. 4-87
xx Central Planning Area Lease Sale 247 Supplemental EIS

4.1.1.23. Human Resources and Land Use ........................................................... 4-90

4.1.1.23.1. Land Use and Coastal Infrastructure ................................... 4-90

4.1.1.23.2. Demographics...................................................................... 4-94

4.1.1.23.3. Economic Factors ................................................................ 4-96

4.1.1.23.4. Environmental Justice ......................................................... 4-98

4.1.1.24. Species Considered due to U.S. Fish and Wildlife Service 

Concerns ............................................................................................... 4-103

4.1.2. Alternative B—Exclude the Unleased Blocks Near Biologically Sensitive 

Topographic Features ............................................................................................ 4-105

4.1.3. Alternative C—No Action..................................................................................... 4-108

4.2. Unavoidable Adverse Impacts of the Proposed Action ....................................................... 4-110

4.3. Irreversible and Irretrievable Commitment of Resources .................................................... 4-112

4.4. Relationship between the Short-term Use of Man’s Environment and the 

Maintenance and Enhancement of Long-term Productivity ................................................ 4-113

5. CONSULTATION AND COORDINATION ..................................................................................... 5-3

5.1. Development of the Proposed Action ...................................................................................... 5-3

5.2. Call for Information and Notice of Intent to Prepare a Supplemental EIS .............................. 5-3

5.3. Development of the Draft Supplemental EIS........................................................................... 5-3

5.3.1. Summary of Comments Received in Response to the Calls for Information ............ 5-4

5.3.2. Summary of Scoping Comments ............................................................................... 5-4

5.3.3. Additional Scoping Opportunities ............................................................................. 5-6

5.3.4. Cooperating Agency .................................................................................................. 5-6

5.4. Distribution of the Draft Supplemental EIS for Review and Comment .................................. 5-7

5.5. Coastal Zone Management Act .............................................................................................. 5-10

5.6. Endangered Species Act......................................................................................................... 5-11

5.7. Magnuson-Stevens Fishery Conservation and Management Act .......................................... 5-11

5.8. National Historic Preservation Act ........................................................................................ 5-12

5.9. Government-to-Government .................................................................................................. 5-13

6. REFERENCES CITED ........................................................................................................................ 6-3

7. PREPARERS ....................................................................................................................................... 7-3

8. GLOSSARY ........................................................................................................................................ 8-3

FIGURES ......................................................................................................................................... Figures-3 

TABLES ........................................................................................................................................... Tables-3 

APPENDIX A. MEMORANDUM OF AGREEMENT BETWEEN THE BUREAU OF 

OCEAN ENERGY MANAGEMENT AND THE NATIONAL PARK 

SERVICE ................................................................................................................... A-3 

APPENDIX B. CATASTROPHIC SPILL EVENT ANALYSIS: HIGH-VOLUME, EXTENDEDDURATION OIL SPILL RESULTING FROM LOSS OF WELL CONTROL ON 

THE GULF OF MEXICO OUTER CONTINENTAL SHELF .................................. B-iii

KEYWORD INDEX ................................................................................................................... Keywords-3 
List of Figures xxi

LIST OF FIGURES

Page

Figure 1-1. Gulf of Mexico Planning Areas, Proposed CPA Lease Sale Area, and Locations 

of Major Cities. .......................................................................................................... Figures-3

Figure 2-1. Location of Proposed Stipulations and Deferrals. ...................................................... Figures-4

Figure 2-2. Military Warning Areas and Eglin Water Test Areas in the Gulf of Mexico. ........... Figures-5

Figure 3-1. Offshore Subareas in the Gulf of Mexico. ................................................................. Figures-6

Figure 4-1. Distribution of Bottom-Water Dissolved Oxygen from July 28 to August 3, 

West of the Mississippi River Delta .......................................................................... Figures-7

Figure 4-2. OCS Leasing Activity Near the Gulf Islands National Seashore ............................... Figures-7 

Figure 4-3. Photograph of Remaining OCS Structures taken from Petit Bois Island Looking 

South .......................................................................................................................... Figures-8 

Figure 4-4. Federal OCS Lease Blocks Subject to the Gulf Islands National Seashore 

Information to Lessees ............................................................................................... Figures-9 

Figure 4-5. Economic Impact Areas in the Gulf of Mexico. ...................................................... Figures-10

List of Tables xxiii

LIST OF TABLES

Page

Table 3-1. Projected Oil and Gas in the Gulf of Mexico OCS ..................................................... Tables-3

Table 3-2. Offshore Scenario Information Related to a Typical Lease Sale in the 

Central Planning Area ................................................................................................. Tables-4

Table 3-3. Offshore Scenario Information Related to OCS Program Activities in the 

Gulf of Mexico (WPA, CPA, and EPA) for 2012-2051 ............................................. Tables-5

Table 3-4. Offshore Scenario Information Related to OCS Program Activities in the 

Central Planning Area for 2012-2051 ......................................................................... Tables-6

Table 3-5. Annual Volume of Produced Water Discharged by Depth (millions of bbl) .............. Tables-7

Table 4-1. Unusual Mortality Event Cetacean Data for the Northern Gulf of Mexico ................ Tables-7

Table 4-2. Recreational and Tourism Employment and Value-Added in BOEM’s 

Economic Impact Areas in 2013 ................................................................................. Tables-8

Table 4-3. Economic and Demographic Information for BOEM’s Economic Impact 

Areas in 2015 .............................................................................................................. Tables-9

Table 4-4. Economic and Demographic Information for BOEM’s Economic Impact 

Areas in 2050 ............................................................................................................ Tables-10

Abbreviations and Acronyms xxv 

ABBREVIATIONS AND ACRONYMS

°C degree Celsius

°F degree Fahrenheit

μg microgram

2012-2017 WPA/CPA Gulf of Mexico OCS Oil and Gas Lease Sales: 2012-2017;

Multisale EIS Western Planning Area Lease Sales 229, 233, 238, 246, and 248; 

 Central Planning Area Lease Sales 227, 231, 235, 241, and 247; 

 Final Environmental Impact Statement; Volumes I-III

2D two-dimensional 

3D three-dimensional 

ac acre

ACP Area Contingency Plan

Agreement Agreement between the United States of America and the United

Mexican States Concerning Transboundary Hydrocarbon Reservoirs 

in the Gulf of Mexico 

AL Alabama

API American Petroleum Institute

Area ID Area Identification

ASLM Assistant Secretary of the Interior for Land and Minerals

B.P. before present

bbl barrel

BBO billion barrels of oil

BOEM Bureau of Ocean Energy Management

BOEMRE Bureau of Ocean Energy Management, Regulation and Enforcement

BOP blowout preventer 

BP British Petroleum

BSEE Bureau of Safety and Environmental Enforcement 

BTEX benzene, ethylbenzene, toluene, and xylene 

Call Call for Information

CD Consistency Determination

CEQ Council on Environmental Quality 

CEWAF chemically enhanced (dispersed) water-accommodated fraction

CFR Code of Federal Regulations

CG Coast Guard (also: USCG)

CH4 methane 

CIAP Coastal Impact Assistance Program

cm centimeter

CMP Coastal Management Program

CO carbon monoxide 

CO2 carbon dioxide 

COE Corps of Engineers (U.S. Army) 

CPA Central Planning Area

CPA 235/241/247 Gulf of Mexico OCS Oil and Gas Lease Sales: 2015-2017;

 Supplemental EIS Central Planning Area Lease Sales 235, 241, and 247; 

 Final Supplemental Environmental Impact Statement 

CSA Continental Shelf Associates

CWPPRA Coastal Wetlands Planning, Protection and Restoration Act

CZM Coastal Zone Management

CZMA Coastal Zone Management Act

DOC Department of Commerce (U.S.) (also: USDOC)

DOCD development operations coordination document 

DOD Department of Defense (U.S.) (also: USDOD)

DOE Department of Energy (U.S.) (also: USDOE)

DOI Department of the Interior (U.S.) (also: USDOI) 
xxvi Central Planning Area Lease Sale 247 Supplemental EIS

DP dynamically positioned 

DPS Distinct Population Segment

e.g. for example 

EA environmental assessment

EFH essential fish habitat

EIA Economic Impact Area

EIS environmental impact statement

EP exploration plan 

EPA Eastern Planning Area

EPA 225/226 EIS Gulf of Mexico OCS Oil and Gas Lease Sales: 2014 and 2016; 

 Eastern Planning Area Lease Sales 225 and 226; 

 Final Environmental Impact Statement 

ERMA Environmental Response Management Application 

ESA Endangered Species Act of 1973 

ESI Environmental Sensitivity Index 

et al. and others 

et seq. and the following 

EWTA Eglin Water Test Area

Five-Year Program Proposed Final Outer Continental Shelf Oil & Gas Leasing Program: 

 2012-2017 

Five-Year Program EIS Outer Continental Shelf Oil and Gas Leasing Program: 2012-2017, 

 Final Programmatic Environmental Impact Statement 

FL Florida 

FPSO floating production, storage, and offloading system 

FR Federal Register

ft feet

FWS Fish and Wildlife Service 

FY fiscal year

g gram

G&G geological and geophysical

GMFMC Gulf of Mexico Fishery Management Council 

GOM Gulf of Mexico 

GPS global positioning system 

GUIS Gulf Islands National Seashore 

H2S hydrogen sulfide 

ha hectare

HWCG Helix Well Containment Group

i.e. that is

in inch 

ITL Information to Lessees and Operators

IUCN International Union for the Conservation of Nature 

kg kilogram

km kilometer

km2 square kilometers

L liter

LA Louisiana 

lb pound 

LC50 lethal concentration, 50% mortality

LCA Louisiana Coastal Area

LNG liquefied natural gas

LUMCON Louisiana Universities Marine Consortium

m meter

m/sec meters/second

MAFLA Mississippi, Alabama, and Florida 

MARAD Maritime Administration (U.S. Department of Transportation) 

Mcf thousand cubic feet 
Abbreviations and Acronyms xxvii 

mi mile

mi2 square miles

mm millimeter

MMbbl million barrels

MMPA Marine Mammal Protection Act of 1972

MMS Minerals Management Service

MOA Memorandum of Agreement 

MODU mobile offshore drilling unit 

MS Mississippi

MWCC Marine Well Containment Company

N. north 

N2O nitrous oxide

NAAQS National Ambient Air Quality Standards

NASA National Aeronautics and Space Administration

NCP National Contingency Plan

NEPA National Environmental Policy Act

NGL natural gas liquid

NMFS National Marine Fisheries Service

nmi nautical-mile

NO2 nitrogen dioxide 

NOA Notice of Availability

NOAA National Oceanic and Atmospheric Administration

NOI Notice of Intent to Prepare an EIS

NOS Notice of Sale 

NOx nitrogen oxides 

NPDES National Pollutant and Discharge Elimination System

NPS National Park Service

NRC National Research Council

NRDA Natural Resource Damage Assessment

NTL Notice to Lessees and Operators

O3 ozone 

OBC ocean bottom cables

OCS Outer Continental Shelf

OCSLA Outer Continental Shelf Lands Act 

ODMDS ocean dredged-material disposal site

OSAT Operational Science Advisory Team

OSHA Occupational Safety and Health Administration 

OSRA Oil Spill Risk Analysis

OSRP oil-spill response plans

OSV offshore supply/service vessels

P.L. Public Law

PAH polycyclic aromatic hydrocarbons

PBR potential biological removal

PM10 particulate matter less than or equal to 10 μm 

PM2.5 particulate matter less than or equal to 2.5 μm 

ppb parts per billion

ppm parts per million 

PSBF potentially sensitive biological feature

PSD Prevention of Significant Deterioration

RESTORE Act Resources and Ecosystems Sustainability, Tourist Opportunities, and Revived 

 Economies of the Gulf Coast States Act of 2012 

ROD Record of Decision

ROV remotely operated vehicle

RRT Regional Response Team

S. south 

SAV submerged aquatic vegetation
xxviii Central Planning Area Lease Sale 247 Supplemental EIS

SBF synthetic-based fluid

SBM synthetic-based mud 

SCAT Shoreline Cleanup and Assessment Team

SE standard error

sec second

Secretary Secretary of the Interior

SIL Significant Impact Level

SMART Special Monitoring of Applied Response Technologies 

SO2 sulphur dioxide 

SOx sulphur oxides 

sp. species

spp. multiple species

Stat. Statute

STOF-THPO Seminole Tribe of Florida-Tribal Historic Preservation Officer

TA&R Technology Assessment and Research Program

Tcf trillion cubic feet

TPH total petroleum hydrocarbon 

Trustee Council Natural Resource Damage Assessment Trustee Council

TX Texas

U.S. United States

U.S.C. United States Code

UME unusual mortality event 

USCG U.S. Coast Guard (also: CG) 

USDHS U.S. Department of Homeland Security 

USDOC U.S. Department of Commerce (also: DOC)

USDOE U.S. Department of Energy (also: DOE) 

USDOI U.S. Department of the Interior (also: DOI) 

USDOT U.S. Department of Transportation (also: DOT) 

USEPA U.S. Environmental Protection Agency 

USGS United States Geological Survey (also: GS)

VGP Vessel General Permit

VOC volatile organic compound

VSP vertical seismic profiling

W. west

WAF water-accommodated fractions

WPA Western Planning Area

WPA 233/CPA 231 Gulf of Mexico OCS Oil and Gas Lease Sales: 2013-2014; 

Supplemental EIS Western Planning Area Lease Sale 233; Central Planning Area 

 Lease Sale 231, Final Supplemental Environmental Impact Statement 

WPA 238/246/248 Gulf of Mexico OCS Oil and Gas Lease Sales: 2014-2016; 

Supplemental EIS Western Planning Area Lease Sales 238, 246, and 248; 

 Final Environmental Impact Statement 

WPA 246/248 Gulf of Mexico OCS Oil and Gas Lease Sales: 2015 and 2016; 

Supplemental EIS Western Planning Area Lease Sales 246 and 248; 

 Final Environmental Impact Statement 

WSF water soluble fraction

yd yard

yr year
Conversion Chart xxix

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

CHAPTER 1 

THE PROPOSED ACTIONS

The Proposed Action 1-3 

1. THE PROPOSED ACTION

1.1. PURPOSE OF AND NEED FOR THE PROPOSED ACTION

The proposed Federal action addressed in this Supplemental Environmental Impact Statement (EIS) is 

to offer for lease certain Outer Continental Shelf (OCS) blocks located in the Central Planning Area 

(CPA) of the Gulf of Mexico (GOM) (Figure 1-1). Under the Proposed Final Outer Continental Shelf 

Oil & Gas Leasing Program: 2012-2017 (Five-Year Program) (USDOI, BOEM, 2012a), proposed CPA 

Lease Sale 247 is tentatively scheduled to be held in March 2017. The purpose of the proposed Federal 

action is to offer for lease those areas that may contain economically recoverable oil and gas resources in 

accordance with the Outer Continental Shelf Lands Act (OCSLA) of 1953 (67 Stat. 462), as amended 

(43 U.S.C. §§ 1331 et seq.). The proposed CPA lease sale will provide qualified bidders the opportunity 

to bid upon and lease acreage in the Gulf of Mexico OCS in order to explore, develop, and produce oil 

and natural gas. Under the OCSLA, for each potential lease sale in the Five-Year Program, the Bureau of 

Ocean Energy Management (BOEM) makes individual decisions on whether and how to proceed with a 

proposed lease sale. This Supplemental EIS will be used by BOEM to make an informed decision on 

proposed CPA Lease Sale 247. 

The need for the proposed action is to further the orderly development of OCS resources. The Gulf of 

Mexico constitutes one of the world’s major oil- and gas-producing areas and has historically provided a 

steady and reliable source of crude oil and natural gas for more than 50 years. Oil serves as the feedstock 

for liquid hydrocarbon products, including gasoline, aviation and diesel fuel, and various petrochemicals. 

Oil from the CPA would help reduce the Nation’s dependence on foreign oil imports. The U.S. 

consumed 19.03 million barrels (MMbbl) of oil per day (USDOE, Energy Information Administration, 

2015a) and 25.26 trillion cubic feet (Tcf) of natural gas per day (USDOE, Energy Information 

Administration, 2014a) in 2014. In 2014, Gulf of Mexico OCS leases provided 16 percent of all crude oil 

production (USDOE, Energy Information Administration, 2015b) and 3.9 percent of all natural gas 

produced in the U.S. (USDOE, Energy Information Administration, 2015c). The Energy Information 

Administration projects the total U.S. consumption of liquid fuels, including fossil fuels and biofuels, to 

fall slightly from 19.06 MMbbl per day in 2014 to 18.73 MMbbl by 2040 (USDOE, Energy Information 

Administration, 2014b). The Energy Information Administration also projects the total U.S. consumption 

of natural gas to rise from 25.26 Tcf in 2014 to 31.48 Tcf by 2040 (USDOE, Energy Information 

Administration, 2014a). The U.S. net imports of natural gas accounted for 1.36 Tcf in 2014 and are 

projected to decrease to 0.04 Tcf by 2017 (USDOE, Energy Information Administration, 2014a). A 

recent report shows total U.S. natural gas production increasing between the 1990’s and 2011, due in part 

to shale gas resources (USDOE, National Energy Technology Laboratory, 2013). This same report 

predicts continued increased natural gas production to 2040 (USDOE, National Energy Technology 

Laboratory, 2013). Altogether, net imports of crude oil and petroleum products (imports minus exports) 

accounted for 28.7 percent of our total petroleum consumption in 2014 and are projected to increase to 

32.2 percent by 2040 (USDOE, Energy Information Administration, 2014c). The U.S. crude oil and 

petroleum products imports stood at 9.2 MMbbl per day in 2014 (USDOE, Energy Information 

Administration, 2015d). Exports totaled 2.9 MMbbl per day in 2014, mainly in the form of distillate fuel 

oil, petroleum coke, and residual fuel oil (USDOE, Energy Information Administration, 2014d). The net 

exports of natural gas are projected to be 0.66 Tcf in 2018 and rise to 5.78 Tcf in 2040 (USDOE, Energy 

Information Administration, 2014a). In 2014, the Nation’s biggest supplier of crude oil and petroleumproduct imports was Canada (37%), with countries in the Persian Gulf being the second largest source 

(20%) (USDOE, Energy Information Administration, 2015d). In 2014, the Nation’s biggest supplier of 

natural gas imports was Canada (98%), with Trinidad being the second largest source (1.6%) (USDOE, 

Energy Information Administration, 2015e). Oil produced from the CPA would also reduce the 

environmental risks associated with transoceanic oil tankering from sources overseas. In addition, natural

gas is not easily transported, making domestic production especially desirable. The need for domestic 

natural gas reserves is also based upon the use of gas as an environmentally preferable alternative to oil 

for generating electricity.

The Secretary of the Interior (Secretary) has designated BOEM as the administrative agency 

responsible for the mineral leasing of submerged OCS lands and for the supervision of most offshore 

operations after lease issuance. BOEM is responsible for managing development of the Nation’s offshore 
1-4 Central Planning Area Lease Sale 247 Supplemental EIS

resources in an environmentally and economically responsible way. The functions of BOEM on the OCS 

include leasing; the regulation of exploration, development, and production activities; plan 

administration; environmental studies; NEPA analysis; hydrocarbon resource evaluation; economic 

analysis; and the renewable energy program. In addition, the Secretary has designated the Bureau of 

Safety and Environmental Enforcement (BSEE) as being responsible for enforcing safety and 

environmental regulations. The functions of BSEE include all field operations, including permitting and 

research, inspections, offshore regulatory programs, oil-spill response, and training and environmental 

compliance functions.

Other Pertinent Environmental Reviews or Documentation

This Supplemental EIS supplements, tiers from, and incorporates by reference all of the relevant 

analyses from the Multisale EIS and Supplemental EISs listed below, i.e., the “prior 2012-2017 Gulf of 

Mexico EISs.”

• July 2012 – Gulf of Mexico OCS Oil and Gas Lease Sales: 2012-2017; Western 

Planning Area Lease Sales 229, 233, 238, 246, and 248; Central Planning Area 

Lease Sales 227, 231, 235, 241, and 247, Final Environmental Impact Statement 

(2012-2017 WPA/CPA Multisale EIS) (USDOI, BOEM, 2012b) 

• April 2013 – Gulf of Mexico OCS Oil and Gas Lease Sales: 2013-2014; Western 

Planning Area Lease Sale 233; Central Planning Area Lease Sale 231, Final 

Supplemental Environmental Impact Statement (WPA 233/CPA 231 Supplemental 

EIS) (USDOI, BOEM, 2013a) 

• September 2014 – Gulf of Mexico OCS Oil and Gas Lease Sales: 2015-2017; 

Central Planning Area Lease Sales 235, 241, and 247, Final Supplemental 

Environmental Impact Statement (CPA 235/241/247 Supplemental EIS) (USDOI, 

BOEM, 2014a) 

• September 2015 – Gulf of Mexico OCS Oil and Gas Lease Sales: 2016 and 2017; 

Central Planning Area Lease Sales 241 and 247; Eastern Planning Area Lease Sale

226, Final Supplemental Environmental Impact Statement (CPA 241/247 and EPA 

226 Supplemental EIS) (USDOI, BOEM, 2015a) 

The NEPA documents listed above are part of the Five-Year Program, and their relationship (tiering

and supplementing) and timing with their respective proposed actions (lease sales) are illustrated in the

figure below.
The Proposed Action 1-5 

Each subsequent Supplemental EIS, regardless of the planning area, updates the analysis of the 

potential environmental effects of oil and natural gas leasing, exploration, development, and production in 

the GOM in Chapter 4.1, and updates the cumulative impacts from the most recent Supplemental EIS. 

Within each specific planning area, the baseline conditions for that planning area are updated to reflect 

the most recent technical and scientific information available. 

This Supplemental EIS focuses on updating the baseline conditions and potential environmental 

effects of oil and natural gas leasing, exploration, development, and production in the CPA since 

publication of the prior 2012-2017 Gulf of Mexico EISs. 

This Supplemental EIS analyzes the potential impacts of the proposed action in the CPA on the 

marine, coastal, and human environments. This Supplemental EIS will also assist decisionmakers in 

making informed, future decisions regarding the approval of operations, as well as leasing. At the 

completion of the NEPA process, a decision will be made for proposed CPA Lease Sale 247. The 

analysis in this Supplemental EIS also focuses on the potential environmental effects of oil and natural 

gas leasing, exploration, development, and production in the areas identified through the Area 

Identification (Area ID) procedure as the proposed lease sale area. In addition to the No Action 

alternative (i.e., cancel the proposed lease sale), other alternatives are considered for the proposed CPA

lease sale, such as deferring certain areas from the proposed lease sale.

1.2. DESCRIPTION OF THE PROPOSED ACTION

The proposed action is the last oil and gas lease sale in the CPA, as scheduled in the Five-Year 

Program. Proposed CPA Lease Sale 247 is tentatively scheduled to be held in March 2017. The analyses 

contained within this Supplemental EIS examine impacts from a single, typical CPA lease sale. 

The proposed CPA lease sale area encompasses about 63 million acres (ac) of the total CPA area of 

66.45 million ac. This area begins 3 nautical miles (nmi) (3.5 miles [mi]; 5.6 kilometers [km]) offshore 

Louisiana, Mississippi, and Alabama, and extends seaward to the limits of the United States’ jurisdiction 
1-6 Central Planning Area Lease Sale 247 Supplemental EIS

over the continental shelf (often referred to as the Exclusive Economic Zone) in water depths up to 

approximately 3,346 meters (m) (10,978 feet [ft]) (Figure 1-1). As of January 2016, approximately 

47.87 million ac of the proposed CPA lease sale area are unleased. This information is updated monthly 

and can be found on BOEM’s website at http://www.boem.gov/Gulf-of-Mexico-Region-Lease-Map/. 

The estimated amount of resources projected to be developed as a result of a single, typical CPA lease 

sale (i.e., proposed CPA Lease Sale 247) is 0.460-0.894 billion barrels of oil (BBO) and 

1.939-3.903 trillion cubic feet (Tcf) of gas. The proposed CPA lease sale includes proposed lease 

stipulations designed to reduce environmental risks; these stipulations are discussed in Chapter 2.3.1.3 of 

this Supplemental EIS and in Chapter 2.4.1.3 of the 2012-2017 WPA/CPA Multisale EIS and WPA 

233/CPA 231 Supplemental EIS and Chapter 2.3.1.3 of the CPA 235/241/247 Supplemental EIS and CPA 

241/247 and EPA 226 Supplemental EIS. 

1.3. REGULATORY FRAMEWORK

Federal laws mandate the OCS leasing program (e.g., OCSLA) and the environmental review process 

(e.g., NEPA). Several Federal regulations establish specific consultation and coordination processes with 

Federal, State, and local agencies (e.g., Coastal Zone Management Act, Endangered Species Act, the 

Magnuson-Stevens Fishery Conservation and Management Act, and the Marine Mammal Protection Act). 

In addition, the OCS leasing process and all activities and operations on the OCS must comply with other 

applicable Federal, State, and local laws and regulations. A detailed list of the major, applicable Federal 

laws, regulations, and Executive Orders are listed below. Information about select, applicable Federal 

laws, regulations, and Executive Orders can be found in OCS Regulatory Framework for the Gulf of 

Mexico Region (Matthews and Cameron, 2010). 

Regulation, Law, and Executive Order Citation

Outer Continental Shelf Lands Act 43 U.S.C. §§ 1331 et seq.

National Environmental Policy Act of 1969 42 U.S.C. §§ 4321-4347

40 CFR §§ 1500-1508

Coastal Zone Management Act of 1972 16 U.S.C. §§ 1451 et seq.

15 CFR part 930

Endangered Species Act of 1973 16 U.S.C. §§ 1531 et seq.

Magnuson-Stevens Fishery Conservation and Management Act 16 U.S.C. §§ 1251 et seq.

Essential Fish Habitat Consultation (in 1996 reauthorization of the 

Magnuson-Stevens Fishery Conservation and Management Act)

P.L. 94-265

16 U.S.C. §§ 1801-1891

50 CFR part 600 subpart K

Marine Mammal Protection Act 16 U.S.C. §§ 1361 et seq.

Clean Air Act 42 U.S.C. §§ 7401 et seq.

40 CFR part 55

Clean Water Act 33 U.S.C. §§ 1251 et seq.

Harmful Algal Bloom and Hypoxia Research and Control Act P.L. 105-383

Oil Pollution Act of 1990 33 U.S.C. §§ 2701 et seq.

Executive Order 12777

Comprehensive Environmental Response, Compensation, and 

Liability Act of 1980 42 U.S.C. §§ 9601 et seq. 

Resource Conservation and Recovery Act 42 U.S.C. §§ 6901 et seq.

Marine Plastic Pollution Research and Control Act 33 U.S.C. §§ 1901 et seq.

National Fishing Enhancement Act of 1984 33 U.S.C. §§ 2601 et seq.

Fishermen’s Contingency Fund 43 U.S.C. §§ 1841-1846

Ports and Waterways Safety Act of 1972 33 U.S.C. §§ 1223 et seq. 

Marine and Estuarine Protection Acts 33 U.S.C. §§ 1401 et seq. 

Marine Protection, Research, and Sanctuaries Act of 1972 P.L. 92-532
The Proposed Action 1-7 

Regulation, Law, and Executive Order Citation

National Estuarine Research Reserves 16 U.S.C. § 1461, Section 315

National Estuary Program P.L. 100-4

Coastal Barrier Resources Act 16 U.S.C. §§ 3501 et seq.

National Historic Preservation Act 54 U.S.C. §§ 300101 et seq.

Rivers and Harbors Act of 1899 33 U.S.C. §§ 401 et seq. 

Occupational Safety and Health Act of 1970 29 U.S.C. §§ 651 et seq.

Energy Policy Act of 2005 P.L. 109-58

Gulf of Mexico Energy Security Act of 2006 P.L. 109-432

Marine Debris Research, Prevention, and Reduction Act P.L. 109-449

American Indian Religious Freedom Act of 1978 P.L. 95-341

42 U.S.C. §§ 1996 and 1996a

Migratory Bird Treaty Act of 1918 16 U.S.C. §§ 703 et seq. 

Submerged Lands Act of 1953 43 U.S.C. §§ 1301 et seq. 

Structures Interfering with Air Commerce 49 U.S.C. § 44718

Marking of Obstructions 14 U.S.C. § 86

Wilderness Act of 1964

P.L. 88-577

16 U.S.C. §§ 1131-1136

78 Stat. 890

Toxic Substances Control Act

P.L. 94-469

15 U.S.C. §§ 2601-2697

Stat. 2003

Bald Eagle Protection Act of 1940 P.L. 86-70

16 U.S.C. §§ 668-668d

Executive Order 11988: Floodplain Management 42 FR 26951 (1977); amended by 

Executive Order 12148 (7/20/79)

Executive Order 11990: Protection of Wetlands 42 FR 26961 (1977); amended by 

Executive Order 12608 (9/9/87)

Executive Order 12114: Environmental Effects Abroad 44 FR 1957 (1979)

Executive Order 12898: Environmental Justice 59 FR 5517 (1994)

Executive Order 13007: Indian Sacred Sites 61 FR 26771-26772 (1996)

Executive Order 13089: Coral Reef Protection 63 FR 32701-32703 (1998)

Executive Order 13175: Consultation and Coordination with Indian 

Tribal Governments 65 FR 67249-67252 (2000)

Executive Order 13186: Responsibilities of Federal Agencies to 

Protect Migratory Birds 66 FR 3853 (2001)

1.3.1. Recent BOEM/BSEE Rule Changes

In light of the 2010 Deepwater Horizon explosion, oil spill, and response, the Federal Government, 

along with industry, increased their rules and safety measures related to oil-spill prevention, containment, 

and response. Additionally, the Federal Government and industry have increased their research and 

reform in response to the Deepwater Horizon explosion, oil spill, and response through governmentfunded research, industry-funded research, and joint partnerships. These joint partnerships are often 

between government agencies, industry, and nongovernmental organizations. For more information about 

the recent BOEM/BSEE rule changes prior to this Supplemental EIS, refer to Chapters 1.3 and 1.5 of the 

prior 2012-2017 Gulf of Mexico EISs. 
1-8 Central Planning Area Lease Sale 247 Supplemental EIS

1.3.1.1. Recent and Ongoing Regulatory Reform and Government-Sponsored 

Research

BOEM and BSEE have instituted regulatory reforms responsive to many of the recommendations 

expressed in the various reports prepared following the Deepwater Horizon explosion, oil spill, and 

response. To date, regulatory reform has occurred through both prescriptive and performance-based 

regulation and guidance, as well as OCS safety and environmental protection requirements, as described 

in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, and EPA 225/226 

EIS. The reforms strengthen the requirements for all aspects of OCS operations. Ongoing reform and 

research endeavors to improve workplace safety and to strengthen oil-spill prevention planning, 

containment, and response are described in detail in Chapter 1.3.1.2 of the 2012-2017 WPA/CPA 

Multisale EIS, and Chapter 1.3.2.3 of the EPA 225/226 EIS, with updated information in Chapter 1.3.2.2 

of the WPA 233/CPA 231 Supplemental EIS, and Chapter 1.3.1.1 of the CPA 235/241/247 Supplemental 

EIS. Since publication of the CPA 235/241/247 Supplemental EIS, no substantive rule changes have 

been implemented that would affect potential environmental impacts from OCS oil- and gas-related 

activities in the Gulf of Mexico. However, new and modified Notices to Lessees and Operators (NTLs) 

and other policies applicable to OCS oil and gas operations in the Gulf of Mexico, which were published 

after the publication of the CPA 241/247 and EPA 226 Supplemental EIS and pertain to environmental 

issues, are summarized below. A detailed listing of the current Gulf of Mexico OCS Region NTLs is 

available through BOEM’s Gulf of Mexico OCS Region’s website at http://boem.gov/Regulations/

Notices-Letters-and-Information-to-Lessees-and-Operators.aspx or through the Region’s Public 

Information Office at 504-736-2519 or 1-800-200-GULF. In addition, a detailed listing of BSEE’s 

current Gulf of Mexico OCS Region NTLs is available through BSEE’s website at 

http://www.bsee.gov/Regulations-and-Guidance/Notices-to-Lessees/index/ or through the Region’s 

Public Information Office at 1-800-200-GULF. 

NTL 2015-BSEE-G01, “Time Between Drilling Operations”

This NTL was issued pursuant to BSEE’s regulations under 30 CFR § 250.103 and 30 CFR § 

250.180(e). It provides guidance and clarification in response to recent questions from the offshore oil 

and gas industry regarding the granting of more than 180 days between drilling operations on leases 

continued beyond their primary terms. 

NTL 2015-BSEE-G02, “Hurricane and Tropical Storm Effects Reports”

This NTL supercedes NTL 2001-G01. It provides guidance on using either email or the eWell 

Permitting and Reporting System to report hurricane and tropical storm effects information, specifies the 

information included in the various hurricane and tropical storm reports, and makes minor administrative 

amendments.

Gulf of Mexico Environmental Studies Program

BOEM’s Environmental Studies Program develops, conducts, and oversees world-class scientific 

research specifically to inform policy decisions regarding development of OCS energy and mineral 

resources. Research covers physical oceanography, atmospheric sciences, biology, protected species, 

social sciences and economics, submerged cultural resources, and environmental fates and effects. 

BOEM is a leading contributor to the growing body of scientific knowledge about the Nation’s marine 

and coastal environment. Studies published by the Environmental Studies Program, Gulf of Mexico OCS 

Region, since publication of the CPA 241/247 and EPA 226 Supplemental EIS are shown in the table 

below. For a list of studies published by the Environmental Studies Program, Gulf of Mexico OCS 

Region, prior to those listed below (i.e., 2006-2013), refer to Appendix E of the CPA 235/241/247 

Supplemental EIS and Chapter 1 of the CPA 241/247 and EPA 226 Supplemental EIS. 
The Proposed Action 1-9 

Publications of the Environmental Studies Program, Gulf of Mexico OCS Region, 

Since Publication of the CPA 241/247 and EPA 226 Supplemental EIS

Study Number Title

BOEM 2015-003 Assessing Impacts of OCS Activities on Public Infrastructure, Services, and Population 

in Coastal Communities Following Hurricanes Katrina and Rita 

BOEM 2015-006 Observations and Dynamics of the Loop Current

BOEM 2015-026 Baseline Bioacoustic Characterization for Offshore Renewable Energy Development in 

the North Carolina and Georgia Wind Planning Areas

BOEM 2015-027

BOEM 2015-028

Long-Term Monitoring at East and West Flower Garden Banks National Marine 

Sanctuary, 2011-2012

Volume 1: Technical Report

Volume 2: Appendixes

BOEM 2015-035 Data Assimilative Hindcast for the Gulf of Mexico

1.3.1.2. Recent and Ongoing Industry Reform and Research

Since publication of the WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, 

and CPA 241/247 and EPA 226 Supplemental EIS, the oil and gas industry and engineering trade groups 

have continued to prepare new standards and develop best practices for the safe and environmentally 

responsible development of OCS oil and gas. As an example, the American Petroleum Institute (API) has

produced several Recommended Practices and Standards that have become part of State and Federal 

regulations. In July 2014, API completed Recommended Practice 17W, “Recommended Practice for 

Subsea Capping Stacks” (API, 2014). This recommended practice covers the design, fabrication, and 

operation of new subsea capping stacks, and it can be used to improve existing equipment. The API’s

standards are designed to assist industry professionals improve the efficiency and cost effectiveness of 

their operations, comply with legislative and regulatory requirements, safeguard health, and protect the 

environment. The API’s Recommended Practices and technical information can be found on API’s 

website (API, 2015a). 

1.4. PRELEASE PROCESS

Scoping for this Supplemental EIS was conducted in accordance with the Council on Environmental 

Quality’s (CEQ) guidelines on implementing NEPA (40 CFR § 1501.7). Scoping provides those with an 

interest in the OCS Program an opportunity to provide comments on the proposed action, alternatives, and 

mitigating measures to reduce or eliminate impacts. In addition, scoping provides BOEM an opportunity 

to update the Gulf of Mexico OCS Region’s environmental and socioeconomic information base. BOEM 

conducted early coordination with appropriate Federal and State agencies, federally recognized Indian 

Tribes, nongovernmental organizations, and other concerned parties to discuss and coordinate the prelease 

process for proposed CPA Lease Sale 247, for this Supplemental EIS. While scoping is an ongoing 

process, it officially commenced on August 17, 2015, with the publication of the Notice of Intent to 

Prepare an EIS (NOI) in the Federal Register (2015a). Additional public notices were distributed via 

local newspapers, the U.S. Postal Service, and the Internet. A 30-day comment period was provided; it 

closed on September 16, 2015. Federal, State, and local governments, and federally recognized Indian 

Tribes, as well as other interested parties, were invited to send written comments to the Gulf of Mexico 

OCS Region on the scope of this Supplemental EIS. Comments were received in response to the NOI 

from Federal and State government agencies, interest groups, industry, businesses, and the general public 

on the scope of this Supplemental EIS, significant issues that should be addressed, alternatives that should 

be considered, and mitigating measures. All scoping comments received were considered in the 

preparation of the Draft Supplemental EIS. The comments are summarized in Chapter 5.3

(“Development of the Draft Supplemental EIS”). 

In addition to BOEM’s consideration of scoping comments received for this Supplemental EIS, this 

document tiers from and incorporates by reference all of the relevant scoping comments and responses to 
1-10 Central Planning Area Lease Sale 247 Supplemental EIS

the comments from the prior 2012-2017 Gulf of Mexico EISs. A summary of scoping comments 

incorporated by reference can be found in Chapter 5.3 (“Development of the Draft Supplemental EIS”) of 

the prior 2012-2017 Gulf of Mexico EISs. 

At the beginning of each Five-Year Program, the Gulf of Mexico OCS Region releases an Area ID 

for each planning area, defining the proposed lease sale areas. On June 20, 2011, BOEM released its 

Area ID decision for the CPA and WPA lease sale areas. The Area ID is an administrative prelease step 

that describes the geographical area of the proposed action (proposed lease sale area) and identifies the 

alternatives, mitigating measures, and issues to be analyzed in the appropriate NEPA document. As 

mandated by NEPA, this Supplemental EIS analyzes the potential impacts of the CPA proposed action on 

the marine, coastal, and human environments.

BOEM mailed copies of the Draft Supplemental EIS for review and comment to Federal, State, and 

local government agencies; federally recognized Indian Tribes; industry; nongovernmental organizations; 

the general public; and local libraries. To initiate the public review and comment period on the Draft 

Supplemental EIS, BOEM published a Notice of Availability (NOA) in the Federal Register. In addition, 

public notices were mailed with the Draft Supplemental EIS and were placed on BOEM’s website at 

http://www.boem.gov/nepaprocess/. 

A consistency review will be performed in accordance with the Coastal Zone Management Act 

(CZMA), and a Consistency Determination (CD) will be prepared for each CZMA State prior to the 

proposed CPA lease sale. To prepare the CDs, BOEM reviews each CZMA State’s Coastal Management 

Program (CMP) and analyzes the potential impacts as outlined in this Supplemental EIS, new 

information, and applicable studies as they pertain to the enforceable policies of each CMP. Based on the 

analyses, BOEM’s Gulf of Mexico OCS Region’s Regional Director makes an assessment of consistency, 

which is then sent to the CZMA States of Louisiana, Mississippi, Alabama, and Florida for the proposed 

CPA lease sale. If a CZMA State disagrees with the Bureau of Ocean Energy Management’s CDs, the 

State is required to do the following under the CZMA: (1) indicate how BOEM’s presale proposal is 

inconsistent with the CZMA State’s CMP; (2) describe the specific enforceable policies (including 

citations) that are inconsistent; and (3) suggest alternative measures to bring BOEM’s proposal into 

consistency with the CZMA State’s CMP and/or describe the need for additional information that would 

allow a determination of consistency. Unlike the consistency process for specific OCS plans and permits, 

there is not a procedure for administrative appeal to the Secretary of Commerce for a Federal CD for 

prelease activities. In the event of a disagreement between a Federal agency and the CZMA State’s CMP 

regarding consistency of the proposed lease sales, either BOEM or the CZMA State may request 

mediation. The regulations provide for an opportunity to resolve any differences with the CZMA State, 

but the CZMA allows BOEM to proceed with a proposed lease sale despite any unresolved disagreements 

if the Federal agency clearly describes in writing how the activity is consistent to the maximum extent 

practicable with the CZMA State’s CMP. 

Proposed CPA Lease Sale 247 is tentatively scheduled for March 2017. BOEM must publish the 

Final Supplemental EIS at least 30 days prior to a decision on whether and/or how to proceed with 

proposed CPA Lease Sale 247. BOEM will publish an NOA for the Final Supplemental EIS in the 

Federal Register, will send copies of the Final Supplemental EIS to Federal, State, and local agencies; 

federally recognized Indian Tribes; industry; nongovernmental organizations; the general public; and 

local libraries. In addition, public notices will be mailed with the Final Supplemental EIS and will be 

placed on BOEM’s website at http://www.boem.gov/nepaprocess/. At the completion of this 

Supplemental EIS process, a decision will be made for proposed CPA Lease Sale 247. 

The Final Supplemental EIS is not a decision document. The Assistant Secretary of the Interior for 

Land and Minerals Management (ASLM) will make a decision on whether to hold the proposed lease sale

and, if the decision is made to hold the lease sale, then any particulars relevant to the lease sale including, 

but not limited to, the lease sale area and any mitigations will be announced in a Final Notice of Sale 

(NOS). A NEPA Record of Decision (ROD) will memorialize the decision and will identify BOEM’s 

preferred alternative for the lease sale, as well as the environmentally preferable alternative, if different. 

The ROD will summarize the proposed action and the alternatives evaluated in this Supplemental EIS, the 

information considered in reaching the decision, and the adopted mitigations. An NOA for the ROD will 

be published in the Federal Register and will be made available on BOEM’s website at http://

www.boem.gov/nepaprocess. 

A Proposed NOS will become available to the public 4-5 months prior to the proposed lease sale. A 

notice announcing the availability of the Proposed NOS appears in the Federal Register, initiating a 
The Proposed Action 1-11

60-day comment period. Comments received will be analyzed during preparation of the decision 

documents that are the basis for the Final NOS, including lease sale configuration and terms and 

conditions. 

If the ASLM decides to hold the proposed lease sale, a Final NOS will be published in its entirety in 

the Federal Register at least 30 days prior to the lease sale date, as required by the OCSLA. 

Measures to Enhance Transparency and Effectiveness in the Leasing and Tiering Process

The following discussion is from the Outer Continental Shelf Oil and Gas Leasing Program: 

2012-2017, Final Environmental Impact Statement (Five-Year Program EIS; USDOI, BOEM, 2012a) and 

has been incorporated into this Supplemental EIS for information purposes. 

BOEM realizes that each region is different in terms of mineral resources and dependent economies, 

the relative state of infrastructure and support industries, and the sensitivity of ecosystems, environmental 

resources, and communities; and that a leasing strategy needs to be sensitive to those differences, but also 

that it must be consistent with OCSLA principles. BOEM envisions a phased OCSLA process that 

minimizes multiple-use and environmental conflicts to the extent possible during the Five-Year Program 

implementation, that makes lease sale decisions in the context of the best available information, and that 

discloses clear reasons for those decisions, even in the face of uncertainty. This vision is consistent with 

the National Ocean Policy Implementation Plan and related Marine Planning initiatives, all of which 

provide a complementary framework for space-use conflict considerations.

BOEM is committing to several process enhancements to ensure transparency during the phased 

OCSLA and tiered NEPA processes of this Five-Year Program. Although specific approaches to 

implementation may be tailored to the different needs of the Regions and their stakeholders, BOEM is 

determined to improve the effectiveness of the tiering process (40 CFR § 1508.28) through the following: 

• Alternative and Mitigation Tracking Table. BOEM has established an alternative 

and mitigation tracking table to provide increased visibility into the consideration of 

recommendations for deferrals, mitigations, and alternatives at different stages of the

leasing process. Beginning with the Five-Year Program EIS, the table tracks the 

lineage and treatment of suggestions for spatial exclusions, temporal deferrals, and/or 

mitigation from the Five-Year Program to the lease sale phase and on to the plan 

phase. This table allows commenters to see how and at what stage of the process 

their concerns are being considered. BOEM will maintain a table that will be 

updated as deferral requests are considered at the lease sale and plan stages and as 

new requests are made. The alternative and mitigation tracking table has been placed 

on BOEM’s website at http://www.boem.gov/5-year/2012-2017/Tracking-Table/. 

• Strengthening the Prelease Sale Process. BOEM is taking a number of steps to 

enhance opportunities for members of the public to comment and provide new 

information in the prelease sale planning process. Historically, the Call for 

Information (Call), which is the first step in the Prelease Sale Process, has generally 

asked for industry to nominate specific blocks or descriptions of areas within the 

Five-Year Program area for which they have the most interest. The NOI requests 

comments from other Federal, State, and local governments, nongovernmental 

organizations, and the general public on issues that should be addressed and 

alternatives that should be considered in the NEPA documents that will be prepared 

for the action.

• Annual Progress Report. BOEM will publish an annual progress report on the 

approved Five-Year Program that includes an opportunity for stakeholders and the 

public to comment on the Five-Year Program’s implementation. Under Section 18(e) 

of the OCSLA, the Secretary must review annually the approved Five-Year Program. 

Historically, this has been an internal review process that reported to the Secretary 

any information or events that might result in a revision to the Five-Year Program. If 

the revision is considered significant under the OCSLA, the Five-Year Program can 

only be revised and reapproved by following the same Section 18 steps used to 

originally develop the Program. However, once the Section 18 process has been 
1-12 Central Planning Area Lease Sale 247 Supplemental EIS

initiated for the next Five-Year Program, the annual review is subsumed in that 

process, as the same substantive and procedural requirements are being addressed.

The findings of the annual progress report may lead the Secretary to revise the FiveYear Program by reducing the size of, delaying, or canceling scheduled lease sales. 

If the desired revisions are considered significant, such as including new areas for 

consideration or more lease sales in areas already included, the entire Section 18 

process must be followed, in essence resulting in the preparation of a new Program. 

BOEM’s 2014 Annual Progress Report (issued in January 2015) provided an 

overview of the activities that occurred during the previous year. Oil and gas 

exploration, development, and production were successful in the Gulf of Mexico, and 

there was no indication of proposed revisions to the current 2012-2017 Five-Year 

Program for the remainder of the Program. Nonetheless, BOEM is currently engaged 

in the development of the 2017-2022 Five-Year Program and should there be any 

proposed revisions, they would be subsumed into the ongoing 2017-2022 Section 18 

process.

• Systematic Planning. BOEM is committed to engaging in systematic planning 

opportunities that foster improved governmental coordination, communication, and 

information exchange. As the only agency authorized to grant renewable energy, 

marine mineral, and oil and gas leases on the OCS, the Bureau of Ocean Energy

Management has been assigned the Federal co-lead, along with the U.S. Coast Guard

(USCG), for systematic regional planning efforts in the Mid-Atlantic. Additionally, 

BOEM will participate on Regional Planning Bodies in the Northeast, Mid-Atlantic, 

and West Coast as the DOI lead. In the Gulf of Mexico OCS Region, BOEM 

representatives will assist the U.S. Fish and Wildlife Service (FWS), the DOI 

regional lead, with various working group activities. This will facilitate data and 

information availability, provide research of new technologies, and identify conflict 

resolution and avoidance strategies. BOEM anticipates that its Marine Planning 

engagement will enhance regulatory efficiency through improved coordination and 

collaboration, and, in the long term, enhance the stewardship of ocean and coastal 

resources.

These strategies will allow BOEM to not only address the activities that take place under the 

2012-2017 Five-Year Program but also to lay the groundwork for decisions that will be faced in 

subsequent Five-Year Programs. BOEM will improve efforts to gather information while enhancing 

opportunities for stakeholders and other interested parties to participate in and be engaged in the 

decisionmaking process. The initiation of studies and long-term planning will facilitate future decisions 

by ensuring that the best information is available when making leasing decisions on the approved 

program and before the development of future OCS Programs. 

1.5. POSTLEASE ACTIVITIES

BOEM and BSEE are responsible for managing, regulating, and monitoring oil and natural gas 

exploration, development, and production operations on the Federal OCS to promote the orderly 

development of mineral resources and to prevent harm or damage to, or waste of, any natural resource, 

any life or property, or the marine, coastal, or human environment. Regulations for oil, gas, and sulphur 

lease operations are specified in 30 CFR parts 250, 550, 551 (except those aspects that pertain to drilling), 

and 554. 

Measures to minimize potential impacts are an integral part of the OCS Program. These measures are 

implemented through lease stipulations, operating regulations, and project-specific requirements or 

approval conditions. The NTLs provide clarifications and additional information on some of these 

measures. Mitigating measures address concerns such as endangered and threatened species, geologic 

and manmade hazards, military warning and ordnance disposal areas, archaeological sites, air quality, oilspill response planning, chemosynthetic communities, artificial reefs, operations in hydrogen sulfide 

(H2S)-prone areas, and shunting of drill effluents in the vicinity of biologically sensitive features. BOEM 
The Proposed Action 1-13

issues NTLs to provide clarification, description, or interpretation of a regulation; to provide guidelines 

on the implementation of a special lease stipulation or regional requirement; or to convey administrative 

information. A detailed listing of the current Gulf of Mexico OCS Region’s NTLs is available through 

BOEM’s website at http://boem.gov/Regulations/Notices-Letters-and-Information-to-Lessees-andOperators.aspx or through the Region’s Public Information Office at 504-736-2519 or 1-800-200-GULF. 

Refer to Appendix A of the CPA 241/247 and EPA 226 Supplemental EIS (“Commonly Applied 

Mitigating Measures”) for more information on the mitigations that BOEM and BSEE apply to permits. 

Formal plans (i.e., exploration plans, development and production plans, and development operations 

coordination documents) and applications must be submitted to BOEM for review and approval before 

any project-specific activities can begin on a lease. Conditions of approval, which are mechanisms to 

control or mitigate potential safety or environmental problems associated with proposed operations, must 

be met before the activities can be approved by BOEM or BSEE. Conditions of approval are based on 

BOEM’s technical and environmental evaluations of the proposed operations. Comments from Federal 

and State agencies (as applicable) are also considered in establishing conditions. Conditions may be 

applied to any OCS plan, permit, right-of-use and easement, or pipeline right-of-way grant.

Some BOEM-identified mitigating measures are implemented through cooperative agreements or 

coordination with the oil and gas industry and Federal and State agencies. These measures include the 

National Marine Fisheries Service’s (NMFS) Observer Program to protect marine mammals and sea 

turtles when OCS structures are removed using explosives, labeling of operational supplies to track 

sources of accidental debris loss, development of methods of pipeline landfall to eliminate impacts to 

barrier beaches, and semiannual beach cleanup events.

Refer to Chapter 1.5 of the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 

Supplemental EIS for descriptions of postlease activities, including the following: geological and 

geophysical (G&G) surveys; exploration and development plans; permits and applications; inspection and 

enforcement; pollution prevention, oil-spill response plans, and financial responsibility; air emissions; 

flaring and venting; hydrogen sulfide contingency plans; archaeological resources regulation; coastal zone 

management consistency review and appeals for plans; best available and safest technologies, including at 

production facilities; personnel training and education; structure removal and site clearance; marine 

protected species NTLs; and the Rigs-to-Reefs program. 

1.6. OTHER OCS OIL- AND GAS-RELATED ACTIVITIES

BOEM and BSEE have programs and activities that are OCS oil- and gas-related but not specific to 

the oil and gas leasing process or to the management of exploration, development, and production 

activities. These programs include environmental and technical studies, cooperative agreements with 

other Federal and State agencies for NEPA work, joint jurisdiction over cooperative efforts, inspection 

activities, OCS sand borrowing, and regulatory enforcement. BOEM also participates in industry 

research efforts and forums. Chapter 1.6 of the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 

231 Supplemental EIS contains descriptions of the other OCS oil- and gas-related activities, including the 

Environmental Studies Program, Technology Assessment Programs (formerly known as Technology 

Assessment & Research [TA&R] Program), and interagency agreements. Refer to Chapter 1.3.1.1 for 

the list of recent Gulf of Mexico Environmental Studies Program publications. 

CHAPTER 2 

ALTERNATIVES INCLUDING THE PROPOSED ACTIONS

Alternatives Including the Proposed Action 2-3 

2. ALTERNATIVES INCLUDING THE PROPOSED ACTION 

This Supplemental EIS addresses one proposed Federal action: proposed oil and gas Lease Sale 247

in the CPA of the Gulf of Mexico OCS (Figure 1-1), as scheduled in the Five-Year Program (USDOI, 

BOEM, 2012a). The proposed action (proposed lease sale) assumes compliance with applicable 

regulations and lease stipulations in place at the time a ROD is signed for the proposed action. 

2.1. SUPPLEMENTAL EIS NEPA ANALYSIS

Proposed CPA Lease Sale 247 was analyzed in the 2012-2017 WPA/CPA Multisale EIS. This 

Supplemental EIS tiers from the prior 2012-2017 Gulf of Mexico EISs (i.e., 2012-2017 WPA/CPA 

Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 

241/247 and EPA 226 Supplemental EIS), and it summarizes and hereby incorporates those documents by 

reference. Proposed CPA Lease Sale 247 is expected to be within the scenario ranges summarized in 

Chapter 3 of this Supplemental EIS and as discussed in Chapter 3 of those NEPA documents from which 

it tiers.

At the completion of the NEPA process for this Supplemental EIS, a decision will be made on 

whether or how to hold proposed CPA Lease Sale 247. Informal and formal consultation with other 

Federal agencies, the affected States, federally recognized Indian Tribes, nongovernmental organizations, 

and the public will be carried out to assist in the determination of whether or not the information and 

analysis contained in this Supplemental EIS is still valid.

2.2. ALTERNATIVES, MITIGATING MEASURES, AND ISSUES

2.2.1. Alternatives

The alternatives to be considered for proposed CPA Lease Sale 247 are detailed in Chapter 2.3. 

These suggested alternatives have been derived from both the historical comments submitted to BOEM

and the EIS-specific scoping performed for this analysis.

Through our scoping efforts for this Supplemental EIS and the prior 2012-2017 Gulf of Mexico EISs, 

numerous issues and topics were identified for consideration. During the scoping period for the prior 

2012-2017 Gulf of Mexico EISs, a number of alternatives or deferral options were suggested and 

examined for inclusion in Chapter 2.2.1 of each of those NEPA documents. Those alternative and 

deferral options were also reexamined during the preparation of this Supplemental EIS. These 

suggestions included additional deferrals, policy changes, and suggestions beyond the scope of this 

Supplemental EIS. BOEM has not identified any new significant information that changes its conclusions 

in the prior 2012-2017 Gulf of Mexico EISs or that indicates that the proposed alternatives or deferral 

options are appropriate for further in-depth analysis. The justifications for not carrying those suggestions 

through detailed analyses in this Supplemental EIS are the same as those used in the prior 2012-2017 Gulf 

of Mexico EISs. 

The analyses of environmental impacts from the proposed alternatives summarized in 

Chapter 2.3.1.2 below and described in detail in Chapter 4.1.1 are based on the development scenario, 

which is a set of assumptions and estimates on the amounts, locations, and timing for OCS oil and gas 

exploration, development, and production operations and facilities, both offshore and onshore. A detailed 

discussion of the development scenario and major related impact-producing factors is included in 

Chapter 3. 

2.2.1.1. Alternatives for Proposed Central Planning Area Lease Sale 247

Alternative A—The Proposed Action (Preferred Alternative): This alternative would offer for lease 

all unleased blocks within the proposed CPA lease sale area for oil and gas operations (Figure 2-1), with 

the following exceptions: 

(1) whole and portions of blocks deferred by the Gulf of Mexico Energy Security Act of 

2006; and
2-4 Central Planning Area Lease Sale 247 Supplemental EIS

(2) blocks that are adjacent to or beyond the United States’ Exclusive Economic Zone 

in the area known as the northern portion of the Eastern Gap. 

The U.S. Department of the Interior (DOI or USDOI) is conservative throughout the NEPA process 

and includes the total area within the CPA for environmental review even though the leasing of portions 

of the CPA (subareas or blocks) can be deferred during a Five-Year Program.

The proposed CPA lease sale area encompasses about 63 million ac of the total CPA area of 

66.45 million ac. As of January 2016, approximately 47.87 million ac of the proposed CPA lease sale 

area are unleased. This information is updated monthly and can be found on BOEM’s website at 

http://www.boem.gov/Gulf-of-Mexico-Region-Lease-Map/. The estimated amount of resources projected 

to be developed as a result of the proposed CPA lease sale is 0.460-0.894 BBO and 1.939-3.903 Tcf of 

gas (Table 3-1).

Alternative B—Exclude the Unleased Blocks Near Biologically Sensitive Topographic Features: This 

alternative would offer for lease all unleased blocks within the proposed CPA lease sale area, as described 

for the proposed action (Alternative A), but it would also exclude from leasing any unleased blocks 

subject to the Topographic Features Stipulation. The estimated amount of resources projected to be 

developed is 0.460-0.894 BBO and 1.939-3.903 Tcf of gas (refer to Chapter 2.3.2 for further details).

Alternative C—No Action: This alternative is the cancellation of the proposed CPA lease sale. If this 

alternative is chosen, the opportunity for development of the estimated 0.460-0.894 BBO and 

1.939-3.903 Tcf of gas that could have resulted from the proposed CPA lease sale would be postponed 

during the current 2012-2017 Five-Year Program, but it could again be contemplated as part of a future 

Five-Year Program. Any potential environmental impacts arising out of the proposed CPA lease sale

would not occur, but activities associated with existing leases in the CPA would continue. This

alternative is also analyzed in the EIS for the Five-Year Program on a nationwide programmatic level.

Alternatives and Deferrals Considered but Not Analyzed in Detail

Chapter 2.2.1.2 of the 2012-2017 WPA/CPA Multisale EIS includes a detailed description of 

alternatives previously considered but not analyzed in detail in this Supplemental EIS, including the 

following: exclude deep water and limit leasing to shallow waters; delay leasing until drilling safety is 

improved; do not allow drilling in areas with strong ocean currents such as the Loop Current; delay 

leasing until the state of the Gulf of Mexico environmental baseline is known; and identify and protect 

sensitive ecosystems. The justifications for not engaging in detailed analysis of these alternatives and 

deferrals in this Supplemental EIS are the same as those used in the prior 2012-2017 Gulf of Mexico 

EISs, and BOEM has identified no new information that changes these conclusions. During scoping for

this Supplemental EIS and the CPA 241/247 and EPA 226 Supplemental EIS, the National Park Service

(NPS) requested that BOEM develop an alternative that excludes unleased blocks within 15 mi (24 km) of 

the Gulf Island National Seashore (GUIS). This alternative was previously addressed in Chapter 2.2.1.1 

of the CPA 241/247 and EPA 226 Supplemental EIS, which is incorporated by reference. 

2.2.2. Mitigating Measures

The NEPA process is intended to help public officials make decisions that are based on an 

understanding of environmental consequences and to take actions that protect, restore, and enhance the 

environment. Agencies are required to identify and include in an EIS those appropriate mitigating 

measures not already included in the proposed action or alternatives. The CEQ regulations (40 CFR § 

1508.20) define mitigation as follows: 

• Avoidance—Avoiding an impact altogether by not taking a certain action or part of 

an action. 

• Minimization—Minimizing impacts by limiting the intensity or magnitude of the 

action and its implementation. 

• Restoration—Rectifying the impact by repairing, rehabilitating, or restoring the 

affected environment. 
Alternatives Including the Proposed Action 2-5 

• Maintenance—Reducing or eliminating the impact over time by preservation and 

maintenance operations during the life of the action. 

• Compensation—Compensating for the impact by replacing or providing substitute 

resources or environments.

2.2.2.1. Proposed Mitigating Measures Analyzed

The potential lease stipulations and mitigating measures included for analysis in this Supplemental 

EIS were developed as a result of numerous scoping efforts for the continuing OCS Program in the Gulf 

of Mexico. Ten lease stipulations (described in Chapter 2.4.1.3 of the 2012-2017 WPA/CPA Multisale 

EIS and WPA 233/CPA 231 Supplemental EIS and Chapter 2.3.1.3 of the CPA 235/241/247 

Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS) are proposed for CPA Lease Sale

247—the Topographic Features Stipulation; Live Bottom (Pinnacle Trend) Stipulation; Military Areas 

Stipulation; Evacuation Stipulation; Coordination Stipulation; Blocks South of Baldwin County, 

Alabama, Stipulation; Protected Species Stipulation; United Nations Convention on the Law of the Sea 

Royalty Payment Stipulation; Below Seabed Operations Stipulation; and the Stipulation on the 

Agreement between the United States of America and the United Mexican States Concerning 

Transboundary Hydrocarbon Reservoirs in the Gulf of Mexico. The United Nations Convention on the 

Law of the Sea Royalty Payment Stipulation is applicable to the proposed CPA lease sale even though it 

is not an environmental or military stipulation.

These measures will be considered for adoption by the ASLM, under authority delegated by the 

Secretary of the Interior. The analysis of any stipulations for Alternative A does not ensure that the 

ASLM will make a decision to apply the stipulations to leases that may result from the proposed CPA 

lease sale nor does it preclude minor modifications in wording during subsequent steps in the prelease 

process if comments indicate changes are necessary or if conditions change.

Any lease stipulations or mitigating measures to be included in a lease sale will be described in the 

ROD for that lease sale. Mitigating measures in the form of lease stipulations are added to the lease terms 

and are therefore enforceable as part of the lease. In addition, each exploration and development plan, as 

well as any pipeline applications that result from a lease sale, will undergo a NEPA review, and additional 

project-specific mitigations will be applied as conditions of plan approval. Refer to Appendix A

(“Commonly Applied Mitigating Measures”) of the CPA 241/247 and EPA 226 Supplemental EIS for 

more information on the mitigations that BOEM and the Bureau of Safety and Environmental 

Enforcement (BSEE) typically apply to plans and/or permits. The BSEE has the authority to monitor and 

enforce these conditions and, under 30 CFR part 250 subpart N, may seek remedies and penalties from 

any operator that fails to comply with those conditions, stipulations, and mitigating measures. 

2.2.2.2. Existing Mitigating Measures

Mitigating measures have been proposed, identified, evaluated, or developed through previous 

BOEM lease sale NEPA review and analysis. Many of these mitigating measures have been adopted and 

incorporated into regulations and/or guidelines governing OCS oil and gas exploration, development, and 

production activities. All plans for OCS oil- and gas-related activities (e.g., exploration and development 

plans, pipeline applications, and structure-removal applications) go through rigorous BOEM review and 

approval to ensure compliance with established laws and regulations. Existing mitigating measures must 

be incorporated and documented in plans submitted to BOEM. Operational compliance of the mitigating 

measures is enforced through BSEE’s onsite inspection program.

Mitigating measures are a standard part of BOEM’s program to ensure that operations are conducted 

in an environmentally sound manner (with an emphasis on minimizing any adverse impact of routine 

operations on the environment). For example, certain measures ensure site clearance, and survey 

procedures are carried out to determine potential snags to commercial fishing gear and to avoid 

archaeological sites and biologically sensitive areas such as pinnacles, topographic features, and 

chemosynthetic and nonchemosynthetic deepwater benthic communities. In addition, all BOEMregulated activities and operations must comply with the requirements of other agencies having 

jurisdiction. Refer to Chapter 5 for more information on applicable consultation and coordination

requirements.
2-6 Central Planning Area Lease Sale 247 Supplemental EIS

Some BOEM-identified mitigating measures are incorporated into OCS operations through 

cooperative agreements or efforts with industry and State and Federal agencies. These mitigating 

measures include mandating compliance with NMFS’s Observer Program to protect marine mammals and 

sea turtles during the use of explosives for structure removal and G&G activities, labeling operational 

supplies to track possible sources of debris or equipment loss, developing methods of pipeline landfall to 

eliminate impacts to beaches or wetlands, and requiring beach cleanup events.

Site-specific mitigating measures are also applied by BOEM during plan and permit reviews. BOEM 

realized that many of these site-specific mitigations were recurring and developed a list of “standard” 

mitigations. There are currently over 120 standard mitigations. The wording of a standard mitigation is 

developed by BOEM in advance and may be applied whenever conditions warrant. Standard mitigation 

text is revised as often as is necessary (e.g., to reflect changes in regulatory citations, agency/personnel 

contact numbers, and internal policy). Site-specific mitigation “categories” include air quality, 

archaeological resources, artificial reef material, chemosynthetic communities, Flower Garden Banks, 

topographic features, hard bottom/pinnacles/potentially sensitive biological features, military warning 

areas and Eglin water test areas, hydrogen sulfide, drilling hazards, remotely operated vehicle surveys, 

geophysical survey reviews, and general safety concerns. Site-specific mitigation “types” include 

advisories, conditions of approval, hazard survey reviews, inspection requirements, notifications, postapproval submittals, and safety precautions. In addition to standard mitigations, BOEM may apply 

nonrecurring mitigating measures that are developed on a case-by-case basis. Refer to Appendix A 

(“Commonly Applied Mitigating Measures”) of the CPA 241/247 and EPA 226 Supplemental EIS for 

more information on the mitigations that BOEM and BSEE typically apply to plans and/or permits.

BOEM is continually revising applicable mitigations to allow the Gulf of Mexico OCS Region to 

more easily and routinely track mitigation compliance and effectiveness. A primary focus of this effort is 

requiring post-approval submittal of information within a specified timeframe or after a triggering event 

(e.g., end of operations reports for plans, construction reports for pipelines, and removal reports for 

structure removals).

2.2.3. Issues

Issues are defined in CEQ Guidance as the principal “effects” that an EIS should evaluate in-depth. 

Selection of environmental and socioeconomic issues to be analyzed was based on the following criteria:

• the issue is identified in CEQ regulations as subject to evaluation;

• the relevant resource/activity was identified through agency expertise, through the 

scoping process, or from comments on past EISs; 

• the resource/activity may be vulnerable to one or more of the impact-producing 

factors associated with the OCS Program;

• a reasonable probability of an interaction between the resource/activity and 

impact-producing factor should exist; or 

• the information that indicates a need to evaluate the potential impacts to a 

resource/activity has become available.

2.2.3.1. Issues to be Analyzed

Chapter 2.2.3.1 of the 2012-2017 WPA/CPA Multisale EIS addresses the issues related to potential 

impact-producing factors and the environmental and socioeconomic resources and activities that could be 

affected by OCS oil and gas exploration, development, production, and transportation activities (i.e., 

accidental events; drilling fluids and cuttings; visual and aesthetic interference; air emissions; water 

quality degradation and other wastes; structure and pipeline emplacement; platform removals; OCS oiland gas-related support services, activities, and infrastructure; and regional cultures and socioeconomics). 

Chapter 4.1 of this Supplemental EIS, Chapter 4.2.1 of the 2012-2017 WPA/CPA Multisale EIS and 

WPA 233/CPA 231 Supplemental EIS, and Chapter 4.1.1 of the CPA 235/241/247 Supplemental EIS and 

CPA 241/247 and EPA 226 Supplemental EIS describe the resources and activities that could be affected 

by the impact-producing factors listed above and include the following resource topics: 
Alternatives Including the Proposed Action 2-7 

— Air Quality

— Archaeological Resources (Historic and 

Prehistoric)

— Beach Mice

— Coastal Barrier Beaches and Associated 

Dunes 

— Coastal and Marine Birds 

— Commercial Fisheries

— Deepwater Benthic Communities 

(Chemosynthetic and Nonchemosynthetic) 

— Diamondback Terrapins 

— Fish Resources and Essential Fish Habitat

— Gulf Sturgeon 

— Human Resources and Land Use 

(Land Use and Coastal Infrastructure,

Demographics, Economic Factors, and 

Environmental Justice)

— Live Bottoms (Pinnacle Trend

and Low Relief) 

— Marine Mammals

— Recreational Fishing 

— Recreational Resources

— Sargassum Communities 

— Sea Turtles 

— Seagrass Communities

— Soft Bottom Benthic 

Communities 

— Species Considered due to 

U.S. Fish and Wildlife Service 

Concerns 

— Topographic Features 

— Water Quality (Coastal and 

Offshore)

— Wetlands

2.2.3.2. Issues Considered but Not Analyzed

As previously noted, the CEQ regulations for implementing NEPA instruct agencies to adopt an early 

process (termed “scoping”) for determining the scope of issues to be addressed and for identifying 

significant issues related to a proposed action. As part of this scoping process, agencies shall identify and 

eliminate from detailed study the issues that are not significant to the proposed action or that have been 

covered by prior environmental review. 

Additional issues were identified during scoping. Many of those issues were addressed in previous 

environmental reviews and, as a result, will not be addressed in this Supplemental EIS. These issues are 

summarized below. 

The NPS provided a recommendation to consider an alternative that excludes unleased blocks within 

15 mi (24 km) of the GUIS, as well as a series of recommendations related to impact assessment that 

should be conducted related to the GUIS and GUIS-related resources. Since the NPS’s comments that 

were submitted for this Supplemental EIS are similar to those submitted for the CPA 241/247 and EPA 

226 Supplemental EIS and since those issues were previously addressed in Chapter 5.12 of the CPA 

241/247 and EPA 226 Supplemental EIS, they have not been carried forward for additional analysis in 

this Supplemental EIS. 

Comments were received from the Louisiana Department of Natural Resources recommending that 

BOEM provide for compensatory mitigating measures for secondary, indirect, and cumulative impacts to 

Louisiana’s coast. Refer to Chapter 5.12 of the CPA 241/247 and EPA 226 Supplemental EIS for 

BOEM’s responses related to these mitigation recommendations. Since it was addressed in the CPA 

241/247 and EPA 226 Supplemental EIS, this issue will not be carried forward for additional analysis in 

this Supplemental EIS. 

Additionally BOEM considers the full range of mitigating measures, including compensatory, during 

site- or activity-specific reviews. BOEM is also evaluating the possible types of compensatory mitigation

to address recent DOI guidance related to landscape-scale mitigation policy and the Presidential 

memorandum dated November 3, 2015, which requires DOI bureaus to explore compensatory mitigation 

when appropriate. 

Additional comments were received during scoping that highlighted the potential impacts to water 

quality and fisheries resources from oil and gas support-vessel discharges and produced waters and 

drilling wastes. A discussion of these impact-producing factors can be found in Chapters 3.1.1.4.10 

(vessel operational wastes), 3.1.1.4.1 (drilling muds and cuttings), and 3.1.1.4.2 (produced waters) of the 

2012-2017 WPA/CPA Multisale EIS. A discussion of these potential impacts can be found in Chapters 

4.2.1.2, 4.2.1.18, 4.2.1.19, and 4.2.1.20 of the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 

231 Supplemental EIS and Chapters 4.1.1.2, 4.1.1.18, 4.1.1.19, and 4.1.1.20 of the CPA 235/241/247 

Supplemental and CPA 241/247 and EPA 226 Supplemental EIS. 
2-8 Central Planning Area Lease Sale 247 Supplemental EIS

Concerns about human health impacts associated with the Deepwater Horizon explosion, oil spill, 

and response were also raised during scoping. As discussed in Chapter 4.2.1.23.4.3 of the 2012-2017 

WPA/CPA Multisale EIS, the Deepwater Horizon explosion, oil spill, and response was an accidental 

event of catastrophic proportion. An analysis of a low-probability catastrophic oil spill and the potential 

human health impacts that may be associated with that type of oil spill and its associated response 

activities can be found in Appendix B of the CPA 241/EPA 226 Supplemental EIS.

One commenter raised concerns about the allocation of offshore oil and gas revenues to coastal states. 

Information about Public Law 109-432, which describes revenue sharing between the Federal 

Government and Gulf of Mexico oil- and gas-producing states (i.e., Alabama, Louisiana, Mississippi, and 

Texas) can be found in Chapter 1.3 of the 2012-2017 WPA/CPA Multisale EIS and in OCS Regulatory 

Framework for the Gulf of Mexico Region (Matthews and Cameron, 2010). 

Another commenter raised a series of concerns about pipelines that bring products onshore. The 

commenter discussed historic and the potential for future vessel/pipelines collisions and associated 

pipeline spills, and requested that these concerns be brought forward for scoping and environmental 

review. Chapter 4.2.1.23.1.1 of the 2012-2017 WPA/CPA Multisale EIS provides detailed information 

about coastal pipelines, pipeline landfalls, and pipeline shore facilities, including the steady decline in 

new pipeline projects. Refer to Chapter 4.2.1.2.1.3 of the 2012-2017 WPA/CPA Multisale EIS for 

information about coastal water quality impacts from spills resulting from accidental events, including 

collisions. In addition, the 2012-2017 WPA/CPA Multisale EIS clarifies that pipelines in State waters are 

not federally managed or maintained (refer to Chapter 5.12 of the 2012-2017 WPA/CPA Multisale EIS). 

Another commenter recommended that an oil-spill buoy system that would detect oil in the event of a 

spill should be in place. There are a number of offshore buoys and other fixed offshore stations that 

document meteorological conditions in the Gulf of Mexico. These stations are owned and operated by a 

variety of entities, including Federal and State governments, private industry, academic research 

institutions, and others. The type, location, and details about the types of historical data collected at these 

stations can be found on NOAA’s National Data Buoy Center website (USDOC, NOAA, 2015a). While 

these stations do not detect oil spills, they do record wind and current information that could be used to 

support trajectory modeling in the event of a spill. Trajectory modeling forecasts the movement of oil by 

employing computer simulations. In some cases, the wind and current information is available in real 

time and can be used to model oil movement, which in turn, can be used for decisionmaking for cleanup 

and protection operations. Section 11 of NTL 2012-BSEE-N06, “Guidance to Owners and Operators of 

Offshore Facilities Seaward of the Coast Line concerning Regional Oil Spill Response Plans,” clarifies 

the requirements related to spill assessment, including encouraging lessees to consider remote-sensing 

technology to acquire information to be used for real-time spill trajectory simulations. For leases or 

facilities located in the Flower Garden Banks Oil Spill Planning Area, Appendix H of NTL 2012-BSEEN06 further outlines the provisions for obtaining real-time, onsite meteorological information to use in 

trajectory simulations in the event of spill.

Comments received during scoping are summarized in Chapter 5.3. 

2.3. PROPOSED CENTRAL PLANNING AREA LEASE SALE 247

2.3.1. Alternative A—The Proposed Action

2.3.1.1. Description

Alternative A would offer for lease all unleased blocks within the proposed CPA lease sale area for oil 

and gas operations (Figure 2-1), with the following exceptions: 

(1) whole and portions of blocks deferred by the Gulf of Mexico Energy Security Act of 

2006; and

(2) blocks that are adjacent to or beyond the United States Exclusive Economic Zone in 

the area known as the northern portion of the Eastern Gap. 

The DOI is conservative throughout the NEPA process and includes the total area within the CPA for 

environmental review even though the leasing of portions of the CPA (subareas or blocks) can be deferred 

during a Five-Year Program.
Alternatives Including the Proposed Action 2-9 

The proposed CPA lease sale area encompasses about 63 million ac of the total CPA area of 

66.45 million ac. As of January 2016, approximately 47.87 million ac of the proposed CPA lease sale 

area are currently unleased. This information is updated monthly and can be found on BOEM’s website 

at http://www.boem.gov/Gulf-of-Mexico-Region-Lease-Map/. The estimated amount of resources 

projected to be developed as a result of the proposed CPA lease sale is 0.460-0.894 BBO and 

1.939-3.903 Tcf of gas (Table 3-1). 

The analyses of impacts summarized below and described in detail in Chapter 4.1.1 are based on the 

development scenario, which is a set of assumptions and estimates on the amounts, locations, and timing 

for OCS oil and gas exploration, development, and production operations and facilities, both offshore and 

onshore. A detailed discussion of the development scenario and major related impact-producing factors is 

included in Chapter 3. 

Alternative A has been identified as BOEM’s preferred alternative; however, this does not mean that 

another alternative may not be selected in the ROD.

2.3.1.2. Summary of Impacts

A search by BOEM’s subject-matter experts was conducted for each resource to consider new 

information made available since publication of the prior 2012-2017 Gulf of Mexico EISs and to consider 

new information on the Deepwater Horizon explosion, oil spill, and response. It must also be emphasized 

that, in arriving at the overall conclusions for certain environmental resources (e.g., coastal and marine 

birds, fisheries, and wetlands), the conclusions are not based on impacts to individuals, small groups of 

animals, or small areas of habitat, but on impacts to the resources/populations as a whole. Any new 

information discovered was analyzed by BOEM’s subject-matter experts to determine if the impact 

conclusions presented in those NEPA documents were altered as a result of the new information.

For the following resources, BOEM’s subject-matter experts determined through literature searches 

and communications with other agencies and academia that there was no new information made available 

since publication of the prior 2012-2017 Gulf of Mexico EISs that is relevant to potential impacts from 

the CPA proposed action. Therefore, the impact conclusions for these resources remain the same as those 

that were presented in the prior 2012-2017 Gulf of Mexico EISs. These impact conclusions are presented 

in Chapter 4.1.1 of this Supplemental EIS. For ease of review, the individual chapter numbers for each 

resource are provided in the following list.

• Seagrass Communities (Chapter 4.1.1.5) 

• Archaeological Resources (Historic and Prehistoric) (Chapters 4.1.1.22.1 and 

4.1.1.22.2, respectively) 

• Species Considered due to U.S. Fish and Wildlife Service Concerns (Chapter 

4.1.1.24) 

For the following resources, BOEM’s subject-matter experts determined through literature searches 

and communications with other agencies and academia that there was new information made available 

since publication of the prior 2012-2017 Gulf of Mexico EISs that is relevant to potential impacts from 

the CPA proposed action. BOEM’s subject-matter experts have reexamined the analyses for these 

resources based on new information made available; however, none of the new information was deemed 

significant in that it did not alter the impact conclusions presented in those NEPA documents. These 

impact conclusions are presented in Chapter 4.1.1. For ease of review, the individual chapter numbers 

for each resource are provided in the following list. 

• Air Quality (Chapter 4.1.1.1) 

• Water Quality (Coastal and Offshore) (Chapters 4.1.1.2.1 and 4.1.1.2.2, 

respectively) 

• Coastal Barrier Beaches and Associated Dunes (Chapter 4.1.1.3) 

• Wetlands (Chapter 4.1.1.4) 
2-10 Central Planning Area Lease Sale 247 Supplemental EIS

• Live Bottoms (Chapter 4.1.1.6) 

• Topographic Features (Chapter 4.1.1.7) 

• Sargassum Communities (Chapter 4.1.1.8) 

• Chemosynthetic Deepwater Benthic Communities (Chapter 4.1.1.9) 

• Nonchemosynthetic Deepwater Benthic Communities (Chapter 4.1.1.10) 

• Soft Bottom Benthic Communities (Chapter 4.1.1.11) 

• Marine Mammals (Chapter 4.1.1.12) 

• Sea Turtles (Chapter 4.1.1.13) 

• Diamondback Terrapins (Chapter 4.1.1.14) 

• Beach Mice (Chapter 4.1.1.15) 

• Coastal and Marine Birds (Chapter 4.1.1.16) 

• Gulf Sturgeon (Chapter 4.1.1.17) 

• Fish Resources and Essential Fish Habitat (Chapter 4.1.1.18) 

• Commercial Fisheries (Chapter 4.1.1.19) 

• Recreational Fishing (Chapter 4.1.1.20) 

• Recreational Resources (Chapter 4.1.1.21) 

• Human Resources and Land Use (Land Use and Coastal Infrastructure, 

Demographics, Economic Factors, and Environmental Justice) (Chapters 4.1.1.23.1, 

4.1.1.23.2, 4.1.1.23.3, and 4.1.1.23.4, respectively) 

Ultimately, no new significant information was discovered that would alter the impact conclusions for 

any of the resources analyzed in the prior 2012-2017 Gulf of Mexico EISs. The analyses and potential 

impacts detailed in those NEPA documents remain valid and, as such, apply for proposed CPA Lease 

Sale 247. 

In accordance with CEQ guidelines to provide decisionmakers with a robust environmental analysis, 

Appendix B (“Catastrophic Spill Event Analysis”) provides an analysis of the potential impacts of a lowprobability catastrophic oil spill, which is not part of the CPA proposed action and not likely expected to 

occur, to the environmental and cultural resources and the socioeconomic conditions analyzed in Chapter 

4.1.1. 

2.3.1.3. Mitigating Measures

The following lease stipulations may be applied to the CPA proposed action as mitigating measures. 

If the decision is to hold a lease sale, the lease stipulations applicable to the sale will be announced in the 

Final Notice of Sale and Record of Decision. 

2.3.1.3.1. Topographic Features Stipulation

The topographic features located in the CPA provide habitat for hard bottom communities of high 

biomass and diversity (Chapter 4.1.1.7). Without the Topographic Features Stipulation and mitigating 

measures, these communities could be severely and adversely impacted by OCS oil- and gas-related

activities resulting from the CPA proposed action if such activities took place on blocks that are subject to 

the Topographic Features Stipulation (i.e., those blocks with a topographic feature, a No Activity Zone 

surrounding a topographic feature, or a shunting zone [1,000-Meter, 1-Mile, 3-Mile, and/or 4-Mile] 

surrounding a topographic feature). The DOI has recognized this problem for some years and, since 

1973, has made lease stipulations a part of leases on or near these biotic communities so that impacts 

from nearby oil and gas activities were mitigated. This stipulation would not prevent the recovery of oil 
Alternatives Including the Proposed Action 2-11

and gas resources within a Topographic Features Stipulation block, but it would serve to protect valuable 

and sensitive biological resources from routine OCS oil- and gas-related activity by distancing bottomdisturbing activity (e.g., anchors, chains, cables, and wire ropes) 152 m (500 ft) from the No Activity 

Zone that surrounds topographic features and by requiring that drill muds and cuttings be shunted to the 

seafloor if a well is within a shunting zone (1,000-Meter, 1-Mile, 3-Mile, and/or 4-Mile) surrounding a 

topographic feature. 

The Topographic Features Stipulation was formulated based on consultation with various Federal 

agencies and comments solicited from the States, industry, environmental organizations, and academic 

representatives. The Topographic Features Stipulation has been updated over time, using years of 

scientific information collected since the stipulation was first proposed. This information includes 

numerous Agency-funded studies of topographic features in the GOM; numerous stipulation-imposed, 

industry-funded monitoring reports; and numerous studies of drilling discharges offshore (Neff, 2005; 

Boehm et al., 2001; Neff et al., 2000; and NRC, 1983). BOEM and the National Oceanic and 

Atmospheric Administration (NOAA) also co-sponsor an ongoing long-term monitoring program at the 

Flower Garden Banks in order to determine if continued offshore oil- and gas-related activity in the GOM 

has impacted the reef habitat of these features. This stipulation protects these biotic communities from 

routine oil and gas activities resulting from the CPA proposed action, while allowing the development of 

nearby oil and gas resources. This stipulation would not prevent adverse effects of an accident such as a 

large oil spill from a nearby oil or gas operation from impacting these biotic communities; however, it 

would distance the activity at least 152 m (500 ft) from the No Activity Zone surrounding topographic 

features, reducing the possibility of physical oiling. The location of the blocks affected by the 

Topographic Features Stipulation is shown on Figure 2-1. A more detailed discussion and definition of 

this stipulation and its effectiveness are found in Chapter 2.4.1.3.1 of the 2012-2017 WPA/CPA Multisale 

EIS.

2.3.1.3.2. Live Bottom (Pinnacle Trend) Stipulation

The Live Bottom (Pinnacle Trend) Stipulation covers the pinnacle trend area of the proposed CPA 

lease sale area. A small portion of the northeastern proposed CPA lease sale area is characterized by a 

pinnacle trend, which is classified as a live bottom under the stipulation. The pinnacles are a series of 

topographic irregularities with variable biotal coverage, which provide structural habitat for a variety of 

pelagic fish. The pinnacles in the region could be impacted from physical damage of unrestricted oil and 

gas activities, as noted in Chapter 4.1.1.6. The Live Bottom (Pinnacle Trend) Stipulation would protect 

live bottoms (Pinnacle Trend features) from routine OCS oil- and gas-related activity by distancing 

bottom-disturbing activity (e.g., anchors, chains, cables, and wire ropes) 30 m (100 ft) from hard 

bottoms/pinnacles. The Live Bottom (Pinnacle Trend) Stipulation is intended to protect the pinnacle 

trend and the associated hard bottom communities from damage and, at the same time, provide for 

recovery of potential oil and gas resources. The location of the pinnacle trend areas of the proposed CPA 

lease sale area is shown on Figure 2-1. A more detailed discussion and definition of this stipulation and 

its effectiveness are found in Chapter 2.4.1.3.2 of the 2012-2017 WPA/CPA Multisale EIS. 

2.3.1.3.3. Military Areas Stipulation

The Military Areas Stipulation has been applied to all blocks leased in military areas since 1977, and 

it reduces the potential impacts, particularly in regards to safety. However, this stipulation does not 

reduce or eliminate the actual physical presence of oil and gas operations in areas where military 

operations are conducted. The stipulation contains a “hold harmless” clause (holding the U.S. 

Government harmless in case of an accident involving military operations) and requires lessees to 

coordinate their activities with appropriate local military contacts. Figure 2-2 shows the military warning 

areas in the Gulf of Mexico. A more detailed discussion and definition of this stipulation and its 

effectiveness are found in Chapter 2.3.1.3.2 of the 2012-2017 WPA/CPA Multisale EIS. 

2.3.1.3.4. Evacuation Stipulation

The Evacuation Stipulation would be a part of any lease in the easternmost portion of the proposed 

CPA lease sale area resulting from the CPA proposed action, i.e., Lease Sale 247. This stipulation would 

provide for evacuation of personnel and shut-in of operations during any events conducted by the military 
2-12 Central Planning Area Lease Sale 247 Supplemental EIS

that could pose a danger to ongoing oil and gas operations. It is expected that the invocation of these 

evacuation requirements will be extremely rare.

It is expected that these measures will serve to eliminate dangerous conflicts between oil and gas 

operations and military operations. Continued close coordination between BSEE and the military may 

result in improvements in the wording and implementation of these stipulations. 

An evacuation stipulation has been applied to all blocks leased in this area since 2001. A more 

detailed discussion and definition of this stipulation and its effectiveness are found in Chapter 2.4.1.3.4 of 

the 2012-2017 WPA/CPA Multisale EIS. 

2.3.1.3.5. Coordination Stipulation

The Coordination Stipulation would be a part of any lease in the easternmost portion of the proposed 

CPA lease sale area resulting from the CPA proposed action, i.e., Lease Sale 247. This stipulation would 

provide for review of pending oil and gas operations by military authorities and could result in delaying 

oil and gas operations if military activities have been scheduled in the area that may put the oil and gas 

operations and personnel at risk. 

A coordination stipulation has been applied to all blocks leased in this area since 2001. A more 

detailed discussion and definition of this stipulation and its effectiveness are found in Chapter 2.4.1.3.5 of 

the 2012-2017 WPA/CPA Multisale EIS. 

2.3.1.3.6. Blocks South of Baldwin County, Alabama, Stipulation

The Blocks South of Baldwin County, Alabama, Stipulation will be included only on leases on blocks 

south of and within 15 mi (24 km) of Baldwin County, Alabama. The stipulation specifies requirements 

for consultation that lessees must follow when developing plans for fixed structures. The stipulation has 

been continually adopted in annual CPA lease sales since 1999. It has been considered satisfactorily 

responsive to the concern of the Governor of Alabama and was adopted in each of the CPA lease sales in 

the 2002-2007 and 2007-2012 Five-Year Programs. A more detailed discussion and definition of this 

stipulation and its effectiveness are found in Chapter 2.4.1.3.6 of the 2012-2017 WPA/CPA Multisale 

EIS.

2.3.1.3.7. Protected Species Stipulation

The Protected Species Stipulation has been applied to all blocks leased in the GOM since December 

2001. This stipulation was developed in consultation with the U.S. Department of Commerce, National 

Oceanic and Atmospheric Administration, NMFS, and the U.S. Department of the Interior, FWS, in 

accordance with Section 7 of the Endangered Species Act, and it is designed to minimize or avoid 

potential adverse impacts to federally protected species. A more detailed discussion and definition of this 

stipulation and its effectiveness are found in Chapter 2.3.1.3.3 of the 2012-2017 WPA/CPA Multisale 

EIS.

2.3.1.3.8. United Nations Convention on the Law of the Sea Royalty Payment 

Stipulation

If the U.S becomes a party to the 1982 United Nations Convention on the Law of the Sea prior to or 

during the life of a lease issued by the U.S on a block or portion of a block located beyond its Exclusive 

Economic Zone as defined in the United Nations Convention on the Law of the Sea and subject to such 

conditions that the Senate may impose through its constitutional role of advice and consent, then the 

royalty payment lease provisions will apply to the lease so issued, consistent with Article 82 of the United 

Nations Convention Law of the Sea. A more detailed discussion and definition of this stipulation can be

found in Chapter 2.3.1.3.4 of the 2012-2017 WPA/CPA Multisale EIS. 

2.3.1.3.9. Below Seabed Operations Stipulation

The Below Seabed Operations Stipulation language is intended to be lease sale-specific language and 

would incorporate maps of the blocks that may be affected. This stipulation can be found in Chapter 

2.4.1.3.9 of the 2012-2017 WPA/CPA Multisale EIS.
Alternatives Including the Proposed Action 2-13

2.3.1.3.10. Stipulation on the Agreement between the United States of America and the 

United Mexican States Concerning Transboundary Hydrocarbon Reservoirs 

in the Gulf of Mexico

The “Agreement Between the United States of America and the United Mexican States Concerning 

Transboundary Hydrocarbon Reservoirs in the Gulf of Mexico” has now entered into force, making it 

possible for U.S. lessees to enter into voluntary agreements with a licensee of the United Mexican States 

to develop transboundary reservoirs. The stipulation has been applied to blocks or portions of blocks 

located wholly or partially within the 3 statute miles (4.8 km) of the maritime or continental shelf 

boundary with Mexico. The stipulation incorporates by reference the Agreement and notifies lessees that, 

among other things, activities in this boundary area will be subject to the Agreement and that approval of 

plans, permits, and unitization agreements will be conditioned upon compliance with the terms of the 

Agreement. For more information, refer to the Agreement itself, which is available on BOEM’s website 

at http://www.boem.gov/BOEM-Newsroom/Library/Publications/Agreement-between-the-United-Statesand-Mexico-Concerning-Transboundary-Hydrocarbon-Reservoirs-in-the-Gulf-of-Mexico.aspx. 

2.3.2. Alternative B—Exclude the Unleased Blocks Subject to the Topographic 

Features Stipulation

2.3.2.1. Description

Alternative B differs from Alternative A by not offering the blocks that are subject to the proposed 

Topographic Features Stipulation but would be offered under Alternative A (Chapter 2.4.1.3.1 of the 

2012-2017 WPA/CPA Multisale EIS and Figure 2-1 of this Supplemental EIS). These unleased blocks 

will not be available for lease under Alternative B. The number of unleased blocks that would not be 

offered under Alternative B represents only a small percentage of the total number of blocks to be offered 

under Alternative A; therefore, it is assumed that the levels of activity for Alternative B would be 

essentially the same as those projected for the CPA proposed action (refer to Chapter 4.1.2). The 

estimated amount of resources projected to be developed under Alternative B is within the same scenario 

range as for Alternative A, i.e., 0.460-0.894 BBO and 1.939-3.903 Tcf of gas. All other assumptions, 

including the 9 other potential stipulations as described in Chapter 2.2.2.1.3, and estimates are the same 

as for Alternative A. A description of Alternative A is presented in Chapter 2.3.1.1. The Topographic 

Features Stipulation would not be applicable with Alternative B because the blocks that could be subject 

to the Topographic Features Stipulation would not be offered for lease. 

2.3.2.2. Summary of Impacts

The analyses of impacts summarized in Chapter 2.3.1.2 and described in detail in Chapter 4.1.1 are 

based on the development scenario, which is a set of assumptions and estimates on the amounts, 

locations, and timing for OCS oil and gas exploration, development, and production operations and 

facilities, both offshore and onshore. A detailed discussion of the development scenario and major related 

impact-producing factors is included in Chapter 3. 

The difference between the potential impacts described for Alternative A and those under 

Alternative B is that under Alternative B no OCS oil- and gas-related activity would take place in the 

blocks subject to the Topographic Features Stipulation (Figure 2-1). The number of blocks that would 

not be offered under Alternative B represents only a small percentage of the total number of blocks to be 

offered under Alternative A; therefore, it is assumed that the levels of activity for Alternative B would be 

similar to those projected for Alternative A. As a result, the impacts expected to result from Alternative B 

would be very similar to those described under the CPA proposed action (Chapter 4.1.1). Regional 

impact levels for all resources, except for the topographic features, would be similar to those described 

under the CPA proposed action. This alternative, if adopted, would prevent any OCS oil- and gas-related

activity whatsoever in the affected blocks; thus, it would eliminate any potential direct impacts to the 

biota of those blocks from OCS oil- and gas-related activities, which otherwise would be conducted 

within the blocks.
2-14 Central Planning Area Lease Sale 247 Supplemental EIS

2.3.3. Alternative C—No Action

2.3.3.1. Description

Alternative C is the cancellation of the proposed CPA lease sale. If this alternative is chosen, the 

opportunity for development of the estimated 0.460-0.894 BBO and 1.939-3.903 Tcf of gas that could 

have resulted from the proposed CPA lease sale would not occur as tentatively scheduled, but it could 

again be contemplated as part of another proposed lease sale in the 2017-2022 Five-Year Program. 

Proposed CPA Lease Sale 247 is the last CPA lease sale in the 2012-2017 Five-Year Program. Typically, 

in past Five-Year Programs, there were planning area lease sales, with one CPA lease sale per year. 

However, the 2017-2022 Five-Year Program may have two regionwide lease sales each year, and future 

lease sales will be dependent on decisions in the 2017-2022 Five-Year Program (USDOI, BOEM, 2015b). 

The No Action alternative, therefore, encompasses the same potential impacts as a decision to delay the 

proposed CPA lease sale to a later scheduled lease sale under the 2017-2022 Five-Year Program, when 

another decision on whether to hold that future lease sale is made. Delay of the proposed CPA lease sale 

was not considered as a separate alternative because the potential impacts are the same, namely that most 

impacts related to Alternative A would not occur as described above. Any potential environmental 

impacts resulting from the proposed CPA lease sale would not occur or would be postponed to a future 

lease sale decision. 

2.3.3.2. Summary of Impacts

Cancelling the proposed CPA lease sale would eliminate the effects described for Alternative A 

(Chapter 4.1.3). The incremental contribution of the proposed CPA lease sale to the cumulative effects 

would also be foregone, but the effects from other activities, including other previous OCS lease sales, 

would remain. Moreover, if the proposed CPA lease sale was cancelled, the resulting development of oil 

and gas could be reevaluated under a future proposed CPA lease sale. Therefore, the overall level of OCS 

oil- and gas-related activity in the CPA would only be reduced by a small percentage, if any, and the 

cancellation of the proposed CPA lease sale would not significantly change the environmental impacts of 

overall OCS oil- and gas-related activity in the short term at least. However, the cancellation of the

proposed CPA lease sale could result in direct economic impacts to the individual companies. Revenues 

collected by the Federal Government (and thus revenue disbursements to the States) also would be 

adversely affected.

If the proposed CPA lease sale was cancelled, then other sources of energy could potentially be 

substituted for the lost production. Principal substitutes would be additional imports, conservation, 

additional domestic production of oil and gas in other areas, and other fuels. These alternatives, except 

conservation, have significant negative environmental impacts of their own. For example, the tankering 

of fuels from alternate sources over longer distances may have significant potential negative impacts, 

including the increased risk of spills in the Gulf of Mexico. 
CHAPTER 3 

IMPACT-PRODUCING FACTORS AND SCENARIO

Impact-Producing Factors and Scenario 3-3 

3. IMPACT-PRODUCING FACTORS AND SCENARIO

3.1. IMPACT-PRODUCING FACTORS AND SCENARIO—ROUTINE OPERATIONS

3.1.1. Offshore Impact-Producing Factors and Scenario

Chapter 3.1.1 of the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, 

CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS describes the 

offshore infrastructure and activities (impact-producing factors) associated with a CPA proposed action 

(i.e., a typical lease sale) within the CPA that could potentially affect the biological, physical, and 

socioeconomic resources of the Gulf of Mexico.

In addition, these chapters describe the OCS Program’s cumulative activity scenario resulting from 

past and future lease sales in the WPA, CPA, and EPA that could potentially affect biological, physical, 

and socioeconomic resources within the Gulf of Mexico. Note that offshore and onshore impactproducing factors and scenarios associated with a WPA or an EPA proposed action (i.e., a typical lease 

sale that would result from a proposed action within the WPA or EPA), as well as OCS Program activity 

resulting from past and future lease sales in the WPA or EPA, are disclosed in the 2012-2017 WPA/CPA 

Multisale EIS, WPA 233/CPA 231 Supplemental EIS, WPA 238/246/248 Supplemental EIS, WPA 

246/248 Supplemental EIS, EPA 225/226 EIS, and CPA 241/247 and EPA 226 Supplemental EIS.

Offshore is defined, for the purposes of this Supplemental EIS, as the OCS portion of the GOM that 

begins 3 marine leagues (9 nmi; 10.36 mi; 16.67 km) offshore Texas and Florida and 3 nmi (3.45 mi; 

5.56 km) offshore Louisiana, Mississippi, and Alabama. The OCS extends seaward to the limits of the 

United States’ jurisdiction over the continental shelf in water depths up to approximately 3,346 m 

(10,978 ft), which comprises the Exclusive Economic Zone (Figure 1-1). Coastal infrastructure and 

activities associated with a CPA proposed action are described in Chapter 3.1.2. 

BOEM projects that the majority of the oil and natural gas fields discovered as a result of the CPA

proposed action will reach the end of their economic life within a time span of 40 years following a lease 

sale. Therefore, activity levels are not projected beyond 40 years for this document. Although unusual 

cases exist where activity on a lease may continue beyond 40 years, BOEM’s forecasts indicate that most 

significant activities associated with exploration, development, production, and abandonment of leases in 

the GOM occur well within the 40-year analysis period. For the cumulative case analysis, total OCS 

Program exploration and development activities are also forecast over a 40-year period. For modeling 

purposes and quantitative OCS Program activity analyses, a 40-year analysis period is also used. 

Exploration and development activity forecasts become increasingly more uncertain as the length of time 

of the forecast increases and the number of influencing factors increases.

BOEM uses a series of spreadsheet-based, data analysis tools to develop the forecasts of oil and gas 

exploration, discovery, development, and production activity for a CPA proposed action and OCS 

Program scenarios presented in this Supplemental EIS. Our analyses incorporate all relevant historical 

activity and infrastructure data, and our resulting forecasts are analyzed and compared with actual 

historical data to ensure that historical precedent and recent trends are reflected in each activity forecast.

BOEM is confident that our analysis methodology, with adjustments and refinements based on recent 

activity levels, adequately projects Gulf of Mexico OCS oil- and gas-related activities in both the short 

term and the long term for the Supplemental EIS analyses.

The CPA proposed action and the Gulfwide OCS Program scenarios are based on the following 

factors:

• resource estimates developed by BOEM; 

• recent trends in the amount and location of leasing, exploration, and development 

activity;

• estimates of undiscovered, unleased, economically recoverable oil and gas resources 

in each water-depth category and each planning area;

• existing offshore and onshore oil and/or gas infrastructure; 

• published data and information; 
3-4 Central Planning Area Lease Sale 247 Supplemental EIS

• industry information; and

• oil and gas technologies, and the economic considerations and environmental 

constraints of these technologies.

Proposed CPA Lease Sale 247 represents 3-4 percent of the OCS Program activities expected in the 

CPA from 2012 through 2051 based on barrels of oil equivalent (BOE) resource estimates and 3 percent 

of the total OCS Program (WPA, CPA, and EPA) from 2012 through 2051. 

Specific projections of activities associated with the CPA proposed action (a typical lease sale) are 

discussed in the following scenario sections. The potential impacts of the projected activities associated 

with a proposed “typical” lease sale are considered in the environmental analysis section (Chapter 4.1.1).

The OCS Program scenario includes all activities that are projected to occur from past, proposed, and 

future lease sales during the analysis period. This includes projected activity from lease sales that have 

been held, including the most recent CPA Lease Sale 235 (March 2015), but for which exploration or 

development has either not yet begun or is continuing. Activities that take place beyond the analysis 

timeframe as a result of future lease sales are not included in this analysis. The impacts of activities 

associated with the OCS Program on biological, physical, and socioeconomic resources are analyzed in 

the cumulative environmental analysis sections (Chapter 4.1.1).

3.1.1.1. Resource Estimates and Timetables

The CPA proposed action and cumulative case have not changed since last analyzed for the CPA 

241/247 and EPA 226 Supplemental EIS. BOEM has not identified any new information or change in 

circumstances since publication of the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 

Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental 

EIS that would change the estimates and timetables.

3.1.1.1.1. Proposed Action

The proposed action scenarios are used to assess the potential impacts of a proposed typical lease 

sale. The resource estimates for a proposed action are based on two factors: (1) the conditional estimates 

of undiscovered, unleased, conventionally recoverable oil and gas resources in the proposed lease sale 

area; and (2) estimates of the portion or percentage of these resources assumed to be leased, discovered, 

developed, and produced as a result of a proposed action. Due to the inherent uncertainties associated 

with an assessment of undiscovered resources, probabilistic techniques were employed and the results 

were reported as a range of values corresponding to different probabilities of occurrence. The estimates 

of the portion of the resources assumed to be leased, discovered, developed, and produced as a result of a 

proposed action are based upon logical sequences of events that incorporate past experience, current 

conditions, and foreseeable development strategies. Historical databases and information derived from oil 

and gas exploration and development activities are available to BOEM and were used extensively in the 

development of these scenarios. The undiscovered, unleased, conventionally recoverable resource 

estimates for a proposed action are expressed as ranges, from low to high. This range provides a 

reasonable expectation of anticipated oil and gas production from a typical lease sale held as a result of a 

proposed action based on an actual range of historic observations. 

Table 3-1 presents the projected oil and gas production for a typical lease sale and cumulatively for 

the OCS Program (between 2012 and 2051) based on planning areas. Table 3-2 provides a summary of 

the major scenario elements of the proposed action, a typical lease sale, and some of the related impactproducing factors for the CPA proposed action. To analyze impact-producing factors for the proposed 

action and the OCS Program, the proposed lease sale areas were divided into an offshore subarea based 

upon ranges in water depth. Figure 3-1 depicts the location of the offshore subareas. The water-depth 

range reflects the technological requirements and related physical and economic impacts as a 

consequence of the oil and gas potential, exploration and development activities, and lease terms unique 

to each water-depth range. Estimates of resources and facilities are distributed into each of the subareas.

Proposed Action Scenario (CPA Typical Lease Sale): The estimated amounts of resources projected 

to be leased, discovered, developed, and produced as a result of a typical proposed CPA lease sale are 

0.460-0.894 BBO and 1.939-3.903 Tcf of gas. 
Impact-Producing Factors and Scenario 3-5 

Offshore and onshore impact-producing factors and scenarios associated with a WPA or an EPA 

proposed action (i.e., a typical lease sale that would result from a proposed action within the WPA or 

EPA), as well as OCS Program activity resulting from past and future lease sales in the WPA or EPA, are 

disclosed in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, WPA 

238/246/248 Supplemental EIS, WPA 246/248 Supplemental EIS, EPA 225/226 EIS, and CPA 241/247 

and EPA 226 Supplemental EIS. 

The numbers of exploration and delineation wells, production platforms, and development wells 

projected to develop and produce the estimated resources for the CPA proposed action are given in Table

3-2. These tables show the distribution of these factors by the offshore subarea in the proposed lease sale 

areas. Table 3-2 also includes estimates of the major impact-producing factors related to the projected 

levels of exploration, development, and production activity. 

Exploratory drilling activity typically takes place over an 8-year period, beginning within 1 year after 

the lease sale. Development activity typically takes place over a 39-year period, beginning with the 

installation of the first production platform and ending with the drilling of the last development wells. 

Production of oil and gas typically begins by the third year after the lease sale and continues to the 40th

year (and in some limited cases beyond). 

3.1.1.1.2. OCS Program

OCS Program Cumulative Scenario (WPA, CPA, and EPA): Projected reserve/resource production 

for the OCS Program is 18.335-25.640 BBO and 75.886-111.627 Tcf of gas and represents anticipated 

production from lands currently under lease plus anticipated production from future lease sales over the 

40-year analysis period. The OCS Program cumulative scenario includes WPA, CPA, and EPA 

production estimates. Table 3-3 presents all anticipated production from lands currently under lease in 

the WPA, CPA, and EPA plus all anticipated activity from future total OCS Program (WPA, CPA, and 

EPA) lease sales over the 40-year analysis period.

WPA Cumulative Scenario: Projected reserve/resource production for the OCS Program in the WPA 

(2.510-3.696 BBO and 12.539-18.434 Tcf of gas) represents all anticipated production from lands 

currently under lease in the WPA plus all anticipated production from future WPA lease sales over the 

40-year analysis period. Projected production represents approximately 14 percent of the oil and 

17 percent of the gas of the total Gulfwide OCS Program. The impact-producing factors, affected 

environment, and environmental consequences related to the WPA cumulative OCS Program activities 

have been disclosed and addressed in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 

Supplemental EIS, WPA 238/246/248 Supplemental EIS, and WPA 246/248 Supplemental EIS. The 

WPA cumulative scenario is included in this Supplemental EIS in the context of the OCS Program, as the 

OCS Program covers all three panning areas.

CPA Cumulative Scenario: Projected reserve/resource production for the OCS Program in the CPA 

(15.825-21.733 BBO and 63.347-92.691 Tcf of gas) represents all anticipated production from lands 

currently under lease in the CPA plus all anticipated production from future CPA lease sales over the 

40-year analysis period. Projected production represents approximately 85-86 percent of the oil and 

83 percent of the gas of the total Gulfwide OCS Program. Table 3-4 presents projections of the major 

activities and impact-producing factors related to future cumulative OCS Program activities in the CPA 

over the 40-year analysis period. The impact-producing factors, affected environment, and environmental 

consequences related to the CPA cumulative OCS Program activities have been disclosed and addressed 

in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 

Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS. 

EPA Cumulative Scenario: Projected reserve/resource production for the OCS Program in the EPA 

(0-0.211 BBO and 0-0.502 Tcf of gas) represents all anticipated production from lands currently under 

lease in the EPA plus all anticipated production from future EPA lease sales over the 40-year analysis 

period. Projected production represents approximately less than 1 percent of the oil and gas of the total 

Gulfwide OCS Program. Table 3-3 of the EPA 225/226 EIS presents projections of the major activities 

and impact-producing factors related to future cumulative OCS Program activities in the EPA over the 

40-year analysis period. The impact-producing factors, affected environment, and environmental 

consequences related to the EPA cumulative OCS Program activities have been disclosed and addressed 

in the EPA 225/226 EIS and CPA 241/247 and EPA 226 Supplemental EIS.
3-6 Central Planning Area Lease Sale 247 Supplemental EIS

3.1.1.2. Exploration and Delineation

3.1.1.2.1. Seismic Surveying Operations

Prelease exploration surveys are comprised of geological and geophysical (G&G) surveys performed 

on or off leased areas. The most prevalent surveys used are seismic surveys with airguns/airgun arrays as 

acoustic sources, which are focused most commonly (but not always) on deeper targets and collectively 

authorized under the Bureau of Ocean Energy Management’s G&G permitting process. Postlease 

(ancillary) G&G surveys collect data on hazards, drilling, reservoir monitoring, and archaeological 

resources. There are also surficial or near-surface surveys conducted to identify potential shallow 

geologic hazards for geotechnical engineering and site planning for bottom-founded structures. Noise

associated with OCS oil and gas development results from various G&G surveys, the operation of fixed 

structures such as offshore platforms and drilling rigs, and helicopter and service-vessel traffic. Noise 

sources related to a CPA proposed action are discussed in Chapter 3.1.1.6 of this Supplemental EIS and 

Chapter 3.1.1.6 of the 2012-2017 WPA/CPA Multisale EIS. 

CPA Proposed Action Scenario (Typical Lease Sale): Because of the cyclic nature in the acquisition 

of G&G surveys, a prelease airgun survey would be attributable to lease sales held up to 7-9 years after 

the survey was completed. Based on an amalgam of historical trends in G&G permitting and industry 

input, BOEM projects that proposed lease sales within the WPA, CPA, and EPA would result in 

29,197 OCS blocks surveyed by 2D and 3D airgun surveys for the years 2012-2017. This breaks down 

per planning area as follows: WPA ~7,300 blocks; CPA ~21,314 blocks; and EPA ~583 blocks. (Note 

that the number of blocks could include multiple surveys on a single block that would then be counted as 

a unique block survey each time.) For postlease ancillary G&G surveys, information obtained from 

specific seismic contractors specializing in high resolution seismic acquisition in the GOM, project that 

the proposed action would result in about 50 vertical seismic profiling (VSP) airgun sourced surveys and 

629 non-airgun, high-resolution surveys covering approximately 226,400 line miles (364,420 km) of 

near-surface and shallow penetration seismic for the years 2012-2017. 

Chapter 3.1.1.2.1 of the 2012-2017 WPA/CPA Multisale EIS describes in detail ocean-bottom 

surveys related to a CPA proposed action. 

OCS Program Cumulative Scenario (WPA, CPA, and EPA): The G&G survey activity levels are 

projected to follow the same trend as exploration drilling activities. These activities, which peaked in 

2008-2010, are projected to steadily decline until 2027, and will potentially remain relatively steady 

throughout the second half of the 40-year analysis period. It is important to note that the cycling of G&G 

data acquisition is not driven by the 40-year life cycle of productive leasing, but instead it will trend to 

respond to new production or potential new production driven by new technology. Consequently, some 

areas will be resurveyed in 2-year cycles, while other areas, considered nonproductive, may not be 

surveyed for 20 years or more. 

Assuming that seismic acquisition will remain the dominant exploration survey used by industry in 

the future and that a number of surveyed blocks will be resurveyed several more times, BOEM makes the 

following projections. During the first 5 years (2012-2017) of the 40-year analysis period (2012-2051), 

BOEM projects the following annual activities: 50 VSP airgun surveys; 226,400 line miles (364,420 km) 

of non-airgun, high-resolution surveys; and 29,197 3D blocks surveyed by deep-penetration airgun arrays, 

including areas that will be resurveyed. Expanding this analysis to the first 20 years (2012-2032), the 

annual projections would be 60 VSP airgun surveys, 400,000 line miles (740,800 km) surveyed by highresolution non-airguns, and 33,000 blocks of 2D/3D deep-penetration airgun surveys (60% in the CPA, 

10% in the EPA, and 30% in the WPA). During the second half of the 40-year analysis period, the annual 

projection would be approximately 40 VSP airgun surveys, 240,000 line miles (444,480 km) surveyed by 

high-resolution non-airguns, and 15,000-20,000 blocks surveyed by deep-penetration airgun surveys 

annually (50% in the CPA, 20% in the EPA, and 30% in the WPA). 

3.1.1.2.2. Exploration and Delineation Plans and Drilling

Chapter 3.1.1.2.2 of the 2012-2017 WPA/CPA Multisale EIS describes in detail exploration and 

delineation plans and drilling related to a CPA proposed action. Oil and gas operators use drilling terms 

that represent stages in the discovery and exploitation of hydrocarbon resources. An exploration well 

generally refers to the first well drilled on a prospective geologic structure to confirm that a resource 

exists and to validate how much resource can be expected. If a resource is discovered in quantities that
Impact-Producing Factors and Scenario 3-7 

appear economically viable, one or more follow-up delineation wells help define the amount of resource 

or the extent of the reservoir. Following a discovery, an operator will often temporarily plug and abandon 

a discovery well to allow time for a development scenario to be generated and for equipment to be built or 

procured. 

In the GOM, exploration and delineation wells are typically drilled with mobile offshore drilling units 

(MODUs), e.g., jack-up rigs, semisubmersible rigs, submersible rigs, platform rigs, or drill ships. 

Non-MODUs, such as inland barges, are also used as drilling rigs. The type of rig chosen to drill a 

prospect depends primarily on water depth. Because the water-depth ranges for each type of drilling rig 

overlap to a degree, other factors such as rig availability and daily operation rates play a large role when 

an operator decides upon the type of rig to contract. The depth ranges for exploration rigs used in this 

analysis for the Gulf of Mexico are indicated below.

MODU or Drilling Rig Type Water Depth Range

Jack-up, submersible, and inland barges ≤100 m (328 ft)

Semisubmersible and platform rig 100-3,000 m (328-9,843 ft)

Drillship ≥600 m (1,969 ft)

Historically, drilling rig availability has been a limiting factor for activity in the GOM and is assumed 

to be a limiting factor for activity projected as a result of a proposed lease sale. Drilling activities may 

also be constrained by the availability of rig crews, shore-based facilities, risers, and other equipment. 

The scenario for a proposed action assumes that an average exploration well will require 30-120 

(average of 60) days to drill. The actual time required for each well depends on a variety of factors, 

including the depth of the prospect’s potential target zone, the complexity of the well design, and the 

directional offset of the wellbore needed to reach a particular zone. This scenario assumes that the 

average exploration or delineation well depth will be approximately 4,572-7,010 m (15,000-23,000 ft) 

below the mudline. 

Some delineation wells may be drilled using a sidetrack technique. In sidetracking a well, a portion 

of the existing wellbore is plugged back to a specific depth, directional drilling equipment is installed, and 

a new wellbore is drilled to a different geologic location. The lessee may use this technology to better 

understand the prospect and to plan future wells. Use of this technology may also reduce the time and 

exploration expenditures needed to help evaluate the prospective horizons on a new prospect. 

The cost of an average exploration well can be $40-$150 million or more, without certainty that 

objectives can be reached. Some recent ultra-deepwater exploration wells (>6,000-ft [1,829-m] water 

depth) in the GOM have been reported to cost upwards of $200 million. The actual cost for each well 

depends on a variety of factors, including the depth of the prospect’s potential target zone, the complexity 

of the well design, and the directional offset of the wellbore needed to reach a particular zone.

Subpart D of BSEE’s regulations (30 CFR part 250) specifies requirements for drilling activities. 

Refer to Chapter 1.3.1 of this Supplemental EIS, Chapter 1.3.1 and Table 1-2 of the 2012-2017 

WPA/CPA Multisale EIS, Chapter 1.3.2 of the WPA 233/CPA 231 Supplemental EIS, and Chapter 1.3.1 

of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS, which 

provide a summary of new and updated safety requirements related to the CPA proposed action. 

CPA Proposed Action Scenario (Typical Lease Sale): BOEM estimates that 168-329 exploration and 

delineation wells would be drilled as a result of the CPA proposed action. Table 3-2 shows the estimated 

range of exploration and delineation wells by water-depth range. Greater than 50 percent of the projected 

wells for the CPA proposed action is expected to be on the continental shelf (0-200 m [0-656 ft] water 

depth). 

CPA Cumulative Scenario: BOEM estimates that 5,270-8,110 exploration and delineation wells 

would be drilled as a result of all cumulative OCS Program activities in the CPA (Table 3-4). 

OCS Program Cumulative Scenario (WPA, CPA, and EPA): BOEM estimates that 6,910-9,827 

exploration and delineation wells would be drilled in the WPA, CPA, and EPA as a result of all active 

OCS leases from the current and previous Five-Year Programs. Table 3-3 shows the estimated range of 

exploration and delineation wells by water-depth range for the OCS Program activities (WPA, CPA, and 

EPA). Of these wells, approximately 55 percent are expected to be on the continental shelf (0-200 m [0-

656 ft] water depth) and approximately 45 percent are expected in intermediate water-depth ranges and 
3-8 Central Planning Area Lease Sale 247 Supplemental EIS

deeper (>200 m; 656 ft). Note that offshore and onshore impact-producing factors and scenarios 

associated with a WPA or an EPA proposed action (i.e., a typical lease sale that would result from a 

proposed action within the WPA or EPA), as well as OCS Program activity resulting from past and future 

lease sales in the WPA or EPA, are disclosed in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 

231 Supplemental EIS, WPA 238/246/248 Supplemental EIS, WPA 246/248 Supplemental EIS, EPA 

225/226 EIS, and CPA 241/247 and EPA 226 Supplemental EIS. 

3.1.1.3. Development and Production

Development and Production Drilling

Following a successful exploration program (i.e., one that results in the discovery of an economically 

viable oil and/or gas field), operators of OCS leases must engage in a series of field development and 

production drilling activities in order to extract the discovered oil and/or gas reserves from the subsurface. 

If, however, the exploration program results in failure, future activity on the lease is minimal, and limited 

to short-duration activities are carried out to plug and permanently abandon the exploration wells drilled 

on the lease.

The initial activity associated with a field development and production drilling program typically is 

the drilling of delineation wells. Delineation wells are drilled to specific subsurface targets in order to 

obtain information about the reservoir that can be used by the operator to identify the lateral and vertical 

extent of a hydrocarbon accumulation. Depending on the information obtained from delineation well 

drilling, these wells can be completed and prepared to serve as production wells. Production wells are 

wells that are drilled following the delineation stage of the development program. The production well is 

drilled specifically for the purpose of extracting hydrocarbons from the subsurface and therefore must be 

positioned within the reservoir in locations where the greatest volume of production can be realized. 

Wells initially drilled as delineation wells that are later converted to production wells and wells drilled as 

production wells are sometimes collectively referred to as development wells.

Following the drilling of development wells, the operator of a field may decide to remain on location 

and immediately begin the next stage of the field development program, i.e., preparing the development 

wells for production. However, there are a number of reasons (e.g., when additional well tests are 

required or if the drilling rig is committed to another location) that the operator may decide to move off 

location and delay the work required to prepare the wells for production. When a decision to delay the 

work is chosen, each development well must be temporarily abandoned before the drilling rig can be 

moved to another location. It is also not uncommon for an operator to drill the required number of 

development wells in stages, leaving some time period in between the well drill stages to evaluate the 

information obtained from the wells and, if necessary, use this information to modify the development 

program. 

The process that includes the suite of activities that are carried out to prepare a development well for 

production is the completion process.1

 When the decision is made to perform a well completion, a new 

stage of activity begins. BOEM estimates that approximately 80-90 percent of wells drilled as 

development wells will become producing wells. There is a wide variety of well completion techniques 

performed in the Gulf of Mexico, and the type of well completion used to prepare a drill well for 

production is based on the rock properties of the reservoir as well as the properties of the reservoir fluid. 

However, for the vast majority of well completions, the typical process includes installing or “running” 

the production casing; cementing the casing; perforating the casing and surrounding cement; injecting 

water, brine, or gelled brine as carrier fluid for frac pack/sand proppant pack and gravel pack; 

treating/acidizing the reservoir formation near the wellbore; installing production screens; running 

production tubing; and installing a production tree. Casing is run in the well to prevent the well from 

collapsing. Cement is pumped into the well both to displace drilling fluids that remain in the well and 

 

1

As described below, there is a wide range of variability in the particular activities that might be used in the 

completion process depending on the specific characteristics of the well. Many of the terms used to describe these 

activities (e.g., fracking and acidization) do not have precise, fixed definitions in all contexts. Accordingly, two 

very different processes with different potential environmental impacts may both be called by the same name. For 

these reasons, the description of these activities in this chapter is meant to be a general description of the range of 

activities that may be involved in well completion.
Impact-Producing Factors and Scenario 3-9 

also to fill in the space that exists between the casing and the face of the rock formations in the wellbore. 

The casing and cement are perforated adjacent to the reservoir to allow the reservoir fluids to enter the 

wellbore. A gravel pack is a filtration system that is used to prevent sand from entering the wellbore. 

Well treatment, such as acidizing, is used to improve the flow of reservoir fluids into the wellbore by 

cleaning out and/or dissolving debris that accumulates in the wellbore and near-wellbore reservoir 

formation as a result of the drilling process. For moderate to high permeability reservoirs, today’s most 

technologically advanced well treatment and stimulation processes are designed not only to mitigate nearwellbore formation damage issues but also to serve as another mechanism to help control the flow of sand 

into the wellbore and to enhance the flow rate of the well. Production tubing is run inside the casing. 

Production tubing protects the casing from wear and corrosion, and it provides a continuous conduit for 

the reservoir fluid to flow from the reservoir to the wellhead. The production tree is a wellhead device 

that is used to control, measure, and monitor the conditions of the reservoir and the well from the surface. 

A commonly used development well completion and stimulation technique that has been used in the 

Gulf of Mexico for more than 25 years is a combined fracturing and gravel packing technique, referred to 

as a fracture pack or “frac-pack” completion, which combines the production improvement from 

hydraulic fracturing with the sand control provided by gravel packing. The term hydraulic fracturing 

covers a broad range of techniques used to stimulate and improve production from a well. Fracture fluid 

is injected into a wellbore at high pressure to break open the rock to create/improve the flow path for 

hydrocarbon to flow into the well. This completion technique, which is typically used for moderate to 

high permeability reservoirs, is used to reduce the movement of sand and other fine particulate matter 

within the reservoir, reduce the concentration of sand and silt in the produced fluids, improve the flow of 

reservoir fluids into the wellbore, increase production rates, and maximize production efficiency. The 

frac-pack completion process uses pressurized fluids, typically seawater, brine, or gelled brine, to create 

small fractures in the reservoir rock within a zone near the wellbore where the reservoir’s permeability 

was damaged by the drilling process. The pressurized high-density, gelatin-like fluid also serves as the 

carrier agent for the mechanical agent or proppant that is mixed with the completion fluids. The 

mechanical agents (i.e., proppant), typically sand, manmade ceramics, or small microspheres (tiny glass 

beads), are injected into the small fractures and remain lodged in the fractures when the process is 

completed. The proppant serves to hold the fractures open, allowing them to perform as conduits to assist 

the flow of hydrocarbons from the reservoir formation to the wellbore. Well treatment chemicals are also 

commonly used to improve well productivity. For example, acidizing a reservoir to dissolve cementing 

agents and improve fluid flow is a common well treatment procedure in the GOM.

In contrast to the large-scale, induced hydraulic fracturing procedures, commonly referred to as 

“fracking,” used in onshore oil and gas operations for low-permeability “tight gas,” “tight oil,” and “shale 

gas,” reservoirs, the vast majority of hydraulic fracturing treatments carried out on the OCS in the GOM 

are “frac packs,” which are small-scale by comparison and most commonly used for high-permeability 

formations to reduce the concentration of sand and silt in the produced fluids and to maintain high flow 

rates. Since damage to the formation caused by drilling operations does not extend for large distances 

away from the reservoir-borehole interface, the fracturing induced by the procedure is also designed to 

remain in close proximity to the borehole, extending distances of typically 15-30 m (49-98 ft) from the 

borehole (Sanchez and Tibbles, 2007).

Additives used in fracture-pack operations are often similar, if not identical, to those used for shale or 

tight sand development onshore and they are used for similar purposes. The concentrations of some of 

these additives are typically different due to the GOM’s very different geologic characteristics of the 

producing formation. The most significant difference is that the GOM typically has much higher 

formation permeabilities and lower amounts of clay/shale in typical formations (API, 2015b). Another 

factor that can significantly influence additive selection and use in offshore operations is the ability to 

discharge treated wastewaters that meet applicable regulatory requirements (API, 2015b).

Boehm et al. (2001) notes 22 functional categories of additives and 2 categories of proppants used 

offshore in the GOM for fracturing activities:
3-10 Central Planning Area Lease Sale 247 Supplemental EIS

— water-based polymers

— defoamers

— friction reducers

— oil gelling additives

— fluid loss additives

— biocides 

— breakers 

— acid-based gel systems

— emulsifiers 

— water-based systems

— clay stabilizers 

— crosslinked gel systems

— surfactants

— alcohol/water systems

— non-emulsifiers

— oil-based systems

— pH control additives

— polymer plugs 

— crosslinkers 

— continuous mix gel concentrates 

— foamers

— resin-coated proppants 

— gel stabilizers 

— intermediate-to-high strength 

ceramic proppants 

Each of these is described in greater detail in the Boehm et al. (2001) study, which is incorporated by 

reference, along with other treatment and completion chemicals. The appendix to the study even offers a 

chemical inventory with example products and Material Safety Data Sheets for those products. In 

general, discharges of any fluids, including those associated with well completion, are subject to the terms 

of National Pollution Discharge Elimination System (NPDES) permits issued by the USEPA under the 

Clean Water Act. These permits place limitations on the toxicity of all effluents, as well as other 

requirements for monitoring and reporting. Wastes and discharges generated from OCS oil- and gasrelated activities, including produced water and well completion fluids, are addressed programmatically 

by BOEM in Chapters 3.1.1.4 and 3.1.2.2.3 of the 2012-2017 WPA/CPA Multisale EIS, from which this 

Supplemental EIS is tiered. 

During a “frac pack”, the pumping equipment, sand (proppant), and additives are carried, mixed, and 

pumped from a specialized stimulation and treatment vessel. The base fluid that is used for the frac-pack 

operation will typically be treated seawater, although other brines may be used if conditions dictate (API, 

2015b). BOEM considers these large special purpose vessels (supporting fracturing operations) as 

offshore supply/service vessels (OSVs). In Table 3-2, the number of OSV trips is estimated by subareas 

(range of water depths) in the GOM. Potential impacts associated with OSVs are described in various 

sections throughout Chapter 3 of this Supplemental EIS; these impacts include operational wastes, noise, 

and air emissions related to vessel movement throughout the GOM. 

What is explained above is a general procedure for frac-pack operation, but every fracturing job is 

case specific. In general, the fracturing process remains the same but chemical formulations, fluid and 

proppant volumes, pump time, and pressure will vary based on the depth and engineering/geologic 

parameters for a particular well completion. After a production test determines the desired production 

rate to avoid damaging the reservoir, the well is ready to go online and produce. 

The development operations and coordination document (DOCD) is the chief planning document that 

lays out an operator’s specific intentions for development. The range of postlease development plans is 

discussed in Chapter 1.5. BOEM estimates that approximately 90 percent of development wells would 

become producing wells. 

CPA Proposed Action Scenario (Typical Lease Sale): It is estimated that 215-417 development and 

production wells will be drilled as a result of the CPA proposed action. Table 3-2 shows the estimated 

range of development and production wells by water-depth subarea. The percentage of projected oil wells 

within the CPA is more evenly distributed throughout the water-depth ranges, with the greatest number of 

wells being forecasted for water depths >2,400 m (7,874 ft), whereas 66-75 percent of the gas wells are 

projected to be drilled on the continental shelf (0-200 m [0-656 ft] water depth). 

CPA Cumulative Scenario: BOEM estimates that 7,080-10,020 development and production wells 

would be drilled as a result of all cumulative OCS Program activities in the CPA (Table 3-4). 

OCS Program Cumulative Scenario (WPA, CPA, and EPA): It is estimated that 8,530-12,180 

development and production wells would be drilled in the WPA, CPA, and EPA as a result of the 

proposed lease sales and all OCS oil- and gas-related activity associated with previous lease sales. 

Table 3-3 shows the estimated range of development wells by water depth. 

Note that offshore and onshore impact-producing factors and scenarios associated with a WPA or an 

EPA proposed action (i.e., a typical lease sale that would result from a proposed action within the WPA 

or EPA), as well as OCS Program activity resulting from past and future lease sales in the WPA or EPA, 
Impact-Producing Factors and Scenario 3-11

are disclosed in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, WPA 

238/246/248 Supplemental EIS, WPA 246/248 Supplemental EIS, EPA 225/226 EIS, and CPA 241/247 

and EPA 226 Supplemental EIS. 

Infrastructure Emplacement/Structure Installation and Commissioning Activities

Chapter 3.1.1.3.2 of the 2012-2017 WPA/CPA Multisale EIS and Chapter 3.1.1.3 of the WPA 

233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 

Supplemental EIS describe in detail infrastructure emplacement/structure installation and commissioning 

activities related to a CPA proposed action. 

Bottom-founded or floating structures may be placed over development wells to facilitate production 

from a prospect. These structures provide the means to access and control the wells. They serve as a 

staging area to process and treat produced hydrocarbons from the wells, initiate export of the produced 

hydrocarbons, conduct additional drilling or reservoir stimulation, conduct workover activities, and carry 

out eventual abandonment procedures. There is a range of offshore infrastructure installed for 

hydrocarbon production. Among these are pipelines, fixed and floating platforms, caissons, well 

protectors, casing, wellheads, and conductors. 

CPA Proposed Action Scenario (Typical Lease Sale): It is estimated that 35-67 production structures 

will be installed as a result of the CPA proposed action. Table 3-2 shows the projected number of 

structure installations for the CPA proposed action by water-depth range. About 80 percent of all the 

production structures installed for the CPA proposed action are projected to be on the continental shelf 

(0-60 m; 0-197 ft).

CPA Cumulative Scenario: BOEM estimates that 1,180-1,640 production structures would be 

installed as a result of all cumulative OCS Program activities in the CPA (Table 3-4). 

OCS Program Cumulative Scenario (WPA, CPA, and EPA): It is estimated that 1,435-2,026 

production structures would be installed in the WPA, and CPA, and EPA as a result of the proposed lease 

sales and all OCS oil- and gas-related activity associated with previous lease sales. Table 3-3 shows the 

projected number of structure installations by water-depth range for the OCS. 

Note that offshore and onshore impact-producing factors and scenarios associated with a WPA or an 

EPA proposed action (i.e., a typical lease sale that would result from a proposed action within the WPA 

or EPA), as well as OCS Program activity resulting from past and future lease sales in the WPA or EPA, 

are disclosed in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, WPA 

238/246/248 Supplemental EIS, WPA 246/248 Supplemental EIS, EPA 225/226 EIS, and CPA 241/247 

and EPA 226 Supplemental EIS. 

Bottom Area Disturbance

Chapter 3.1.1.3.2.1 of the 2012-2017 WPA/CPA Multisale EIS and Chapter 3.1.1.3 of the WPA 

233/CPA 231 Supplemental EIS and CPA 235/241/247 Supplemental EIS describe in detail infrastructure

emplacement/structure installation and commissioning activities related to the CPA proposed action. 

Structures emplaced or anchored on the OCS to facilitate oil and gas exploration and production 

include drilling rigs or MODUs, pipelines , and fixed surface, floating, and subsea production systems. 

These are discussed in Chapter 3.1.1.3 of this Supplemental EIS, Chapters 3.1.1.3.1 and 3.1.1.3.2 of the 

2012-2017 WPA/CPA Multisale EIS, and Chapter 3.1.1.3 of the WPA 233/CPA 231 Supplemental EIS, 

CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS. The 

emplacement or removal of these structures disturbs small areas of the sea bottom beneath or adjacent to 

the structure. If mooring lines of steel, chain, or synthetic polymer are anchored to the sea bottom, areas 

around the structure can also be directly affected by their emplacement. This disturbance includes 

physical compaction or crushing beneath the structure or mooring lines and the resuspension and 

settlement of sediment caused by the activities of emplacement. Movement of floating types of facilities

will also cause the movement of the mooring lines in the facilities’ array. Small areas of the sea bottom 

will be affected by this kind of movement. Impacts from bottom disturbance are of concern near sensitive 

areas such as topographic features, pinnacles, low-relief live bottom features, chemosynthetic 

communities, high-density biological communities in water depths ≥400 m (1,312 ft), and archaeological 

sites.
3-12 Central Planning Area Lease Sale 247 Supplemental EIS

Sediment Displacement

Chapter 3.1.1.3.2.2 of the 2012-2017 WPA/CPA Multisale EIS and Chapter 3.1.1.3 of the WPA 

233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 

Supplemental EIS describe in detail sediment displacement related to a CPA proposed action. 

Displaced sediments are those that have been physically moved “in bulk.” Displaced sediments will 

cover or bury an area of the seafloor, while resuspended sediments will cause an increase in turbidity of 

the adjacent water column. Resuspended sediments may include entrained heavy metals or hydrocarbons 

and will eventually settle, covering the surrounding seafloor. 

Infrastructure Presence

Chapter 3.1.1.3.3 of the 2012-2017 WPA/CPA Multisale EIS and Chapter 3.1.1.3 of the WPA 

233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 

Supplemental EIS describe in detail impact-producing factors due to infrastructure presence related to a 

CPA proposed action. 

The installation and maintenance of infrastructure may include, but is not limited to, the following:

• anchoring; 

• offshore production systems; 

• space-use requirements (deployment of survey equipment or bottom-founded 

production equipment); 

• aesthetic quality (presence and visibility of equipment, vessels, and air traffic); and

• workovers and abandonments. 

3.1.1.4. Operational Waste Discharged Offshore

Chapter 3.1.1.4 of the 2012-2017 WPA/CPA Multisale EIS describes in detail impacting factors 

related to operational wastes discharged offshore, and Chapter 3.1.1.4 of the WPA 233/CPA 231 

Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental 

EIS provide a summary as well as updated information on stricter regulations regarding vessel discharges

and produced water volumes. Operational wastes discharged offshore include the following: 

• drilling muds and cuttings; 

• produced waters; 

• well treatment, workover, and completion fluids; 

• production solids and equipment; 

• bilge, ballast, and fire water; 

• cooling water; 

• deck drainage;

• treated domestic and sanitary wastes; 

• minor discharges; 

• vessel operational discharges; and

• distillation and reverse osmosis brine.

BOEM maintains records of the volume of water produced from each block on the OCS and its 

disposition―injected on lease, injected off lease, transferred off lease, or discharged overboard. The 
Impact-Producing Factors and Scenario 3-13

amount discharged overboard for the years 2000-2014 is summarized by water depth in Table 3-5, with 

new data provided for the year 2014 as well as any updates available for past years. The total volume for 

all water depths during this 14-year period ranged from 485.6 to 648.2 MMbbl, with the largest 

contribution (68-88%) coming from operations on the shelf. The total volume of produced water 

generally decreased after 2004, reflecting an overall decrease in contributions from operations on the 

shelf. The contribution of produced water from operations in deep water (>400-m [1,312-ft] water depth) 

and ultra-deepwater (>1,600-m [5,249-ft] water depth) production has been increasing. From 2000 to 

2014, the contribution from these operations (deep and ultra-deepwater together) increased from 6 percent 

(37.8 MMbbl) to 31 percent (150.0 MMbbl) of the total produced-water volume (calculated from data in 

Table 3-5). The updated annual amounts and depth distributions of produced water discharged by depth 

are within the range of or similar to data presented in the 2012-2017 WPA/CPA Multisale EIS, WPA 

233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 

Supplemental EIS. Thus, this new information did not change the validity of the operational wastes

discussions previously presented. 

3.1.1.5. Air Emissions

In 1990, pursuant to Section 328 of the Clean Air Act Amendments and following consultation with 

the Commandant of the U.S. Coast Guard (USCG) and the Secretary of the Interior, the U.S. 

Environmental Protection Agency (USEPA) assumed air quality responsibility for the OCS waters in the 

GOM east of longitude 87.5o W., and this Agency retained National Ambient Air Quality Standards 

(NAAQS) air quality jurisdiction for OCS operations west of the same longitude in the GOM. However, 

in 2014, BOEM’s air quality regulations underwent a comprehensive review to replace obsolete 

provisions and to ensure that updates in regulations are following improvements in scientific and 

technological information. BOEM’s air quality regulations update is expected to be published within the 

next 2 years as of the publication of this Supplemental EIS.

There are many air emissions sources related to OCS oil and gas exploration, development, and 

production in the GOM. During the exploration stage, most OCS emissions are from non-platform 

sources and include combustion from the equipment used on a drilling rig or from fuel usage of a support 

vessel. During the production stage, most emissions are from platform emission sources and include 

boilers, diesel engines, combustion flares, fugitives, glycol dehydrators, natural gas engines, turbines, 

pneumatic pumps, pressure/level controllers, storage tanks, cold vents, and others. During the 

development stage, most OCS emissions are from non-platform emissions and include fuel usage of 

support or survey vessels to lay pipelines, install facilities, or map geologic formations and seismic 

properties. 

Pollutants released by OCS oil- and gas-related sources include the NAAQS pollutants carbon 

monoxide (CO), nitrogen oxides (NOx), particulate matter (PM), and sulfur dioxide (SO2). Pollutants also 

released by OCS sources (NOx and volatile organic compounds [VOC]) are precursors to ozone, which is 

formed by photochemical reactions in the atmosphere and is another NAAQS pollutant. Lastly, OCS oiland gas-related sources release greenhouse gas emissions, such as carbon dioxide (CO2), methane (CH4), 

and nitrous oxide (N2O).

The Year 2011 Gulfwide Emissions Inventory Study (Wilson et al., 2014) indicates that OCS oil and 

gas production platform and non-platform sources emit the majority of criteria pollutants and greenhouse 

gases in the GOM on the OCS, with the exception of SO2 (primarily emitted from commercial marine 

vessels), and N2O (from biological sources). The OCS oil and gas production platform and non-platform 

sources account for 90 percent of the total CO emissions, 73 percent of NOx emissions, 68 percent of 

PM10 emissions, 42 percent of SO2 emissions, 63 percent of VOC emissions, and 85 percent of the 

greenhouse gas emissions. Similar to the 2008 inventory (Wilson et al., 2010), natural gas engines on 

platforms represented the largest CO emission source, accounting for 47 percent of the total estimated CO 

emissions, and support vessels were the highest emitters of both NOx and PM10, accounting for 37 percent

and 42 percent, respectively, of the total estimated emissions. Oil and natural gas production platform 

vents account for the highest percentage (29%) of the VOC emissions. Support vessels (32% of total 

emissions), production platform natural gas, diesel, and dual-fuel turbines (18% of total emissions), and 

commercial marine vessels (11% of total emissions) emit the majority of the greenhouse gas emissions.
3-14 Central Planning Area Lease Sale 247 Supplemental EIS

3.1.1.6. Noise

Noise associated with OCS oil and gas development results from G&G surveys, the installation of 

structures, the operation of fixed structures such as offshore platforms and drilling rigs, the 

decommissioning and removal of structures, and helicopter and service-vessel traffic. Noise generated 

from these activities can be transmitted through both air and water, and may be long-lived or temporary. 

Offshore drilling and production involve various activities that produce a composite underwater noise 

field. The source level and frequency of the noise are highly variable, both between and among the 

various industry sources. Noise from proposed OCS oil- and gas-related activities may affect resources 

near the activities. Whether a sound is or is not detected by marine organisms depends both on the 

acoustic properties of the source (spectral characteristics, intensity, and transmission patterns) and the 

sensitivity of the hearing system in the marine organism. Noise can cause varying degrees of harassment 

and/or behavioral responses to exposed animals, which may include, for example, interruptions to 

feeding, mating, migrating, communication, and/or alternation of hearing (temporary or permanent 

threshold shift). 

Chapter 3.1.1.6 of the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, 

CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS describes in 

detail noise-related impact-producing factors associated with OCS oil and gas development for a CPA 

proposed action. 

3.1.1.7. Major Sources of Oil Inputs in the Gulf of Mexico

Petroleum hydrocarbons can enter the GOM from a wide variety of sources. The major sources of oil 

inputs in the GOM are natural seepage, permitted produced-water discharges, land-based discharges, and 

accidental spills. Numerical estimates of the contributions for these sources to the GOM coastal and 

offshore waters are shown in Tables 3-8 and 3-9 of the 2012-2017 WPA/CPA Multisale EIS. Chapter 

3.1.1.7 of the 2012-2017 WPA/CPA Multisale EIS describes in detail major sources of oil inputs in the 

Gulf of Mexico, including natural seepage, produced water, land-based discharges, and spills.

Chapter 3.1.1.7.4 of the 2012-2017 WPA/CPA Multisale EIS also provides the following information 

related to oil spills: 

• trends in reported spill volumes and numbers; 

• projections of future spill events;

• OCS oil- and gas-related offshore oil spills; 

• non-OCS oil- and gas-related offshore spills; 

• OCS oil- and gas-related coastal spills; 

• non-OCS oil- and gas-related coastal spills; and

• other sources of oil. 

3.1.1.8. Offshore Transport

Offshore transport includes both movements of oil and gas products as well as the transportation of 

equipment and personnel. These include pipelines (installation and maintenance, and landfalls), barges, 

oil tankers, and projections related to floating production, storage, and offloading systems, service 

vessels, and helicopter trips.

Chapter 3.1.1.8 of the 2012-2017 WPA/CPA Multisale EIS and CPA 235/241/247 Supplemental EIS 

describes in detail the sources of offshore transport and proposed action scenarios for a CPA proposed 

action. 

3.1.1.9. Safety Issues

Safety issues related to OCS oil and gas development include the presence of hydrogen sulfide and 

sulfurous petroleum and shallow hazards. These safety issues are described in detail for a CPA proposed 
Impact-Producing Factors and Scenario 3-15

action in Chapters 3.1.1.9.1 and 3.1.1.9.2 of the 2012-2017 WPA/CPA Multisale EIS. In addition, 

technologies continue to evolve to meet the technical, environmental, and economic challenges of 

deepwater development. These new and unusual technologies are described in Chapter 3.1.1.9.3 of the 

2012-2017 WPA/CPA Multisale EIS.

3.1.1.10.Decommissioning and Removal Operations

During exploration, development, and production operations, the seafloor around activity sites within 

a proposed lease sale area becomes the repository of temporary and permanent equipment and structures. 

In compliance with Section 22 of BOEM’s Oil and Gas Lease Form (BOEM-2005) and BSEE regulations 

(30 CFR §§ 250.1710 et seq.—Permanently Plugging Wells and 30 CFR §§ 250.1725 et seq.—Removing 

Platforms and Other Facilities), lessees are required to remove all seafloor obstructions from their leases 

within 1 year of lease termination or relinquishment. These regulations require lessees to sever bottomfounded structures and their related components at least 5 m (15 ft) below the mudline to ensure that 

nothing would be exposed that could interfere with future lessees and other activities in the area. The 

structures are generally grouped into two main categories depending upon their relationship either to the 

platform/facility (e.g., piles, jackets, caissons, templates, mooring devises, etc.) or to the well (e.g., 

wellheads, casings, casing stubs, etc.).

Decommissioning and removal operations, including a CPA proposed action and OCS Program 

scenarios, are described in detail in Chapter 3.1.1.10 of the 2012-2017 WPA/CPA Multisale EIS. 

3.1.2. Coastal Impact-Producing Factors and Scenario

3.1.2.1. Coastal Infrastructure

A full description of coastal impact-producing factors and scenario is presented in Chapter 3.1.2 of 

the 2012-2017 WPA/CPA Multisale EIS, WPA/CPA 233/231 Supplemental EIS, CPA 235/241/247 

Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS. No new significant information 

was discovered that would alter impact conclusions based upon these operations. For more details refer 

to Chapter 3.1.2 of the 2012-2017 WPA/CPA Multisale EIS, WPA/CPA 233/231 Supplemental EIS, CPA 

235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS, which describe 

coastal impact-producing factors. The following information is a summary and update of information 

discussed in detail in the prior 2012-2017 Gulf of Mexico EISs, including the following: 

• service bases; 

• helicopter hubs; 

• platform fabrication yards; 

• shipbuilding and shipyards;

• pipecoating facilities and yards; 

• refineries; 

• gas processing plants;

• liquefied natural gas (LNG) facilities;

• pipeline shore facilities, barge terminals, and tanker port areas;

• coastal pipelines; 

• coastal barging; and 

• navigation channels. 

Coastal oil- and gas-related infrastructure has developed over many decades in the Gulf of Mexico 

region; it is an extensive and mature system that provides support for offshore activities. The expansive 

presence of this coastal infrastructure is the result of long-term industry offshore and onshore trends and 
3-16 Central Planning Area Lease Sale 247 Supplemental EIS

is not subject to rapid fluctuations. The routine activities of built infrastructure associated with the CPA 

proposed action are regulated by Federal and State agencies through permitting processes, routine 

inspections, and a structured enforcement regime. Permit requirements largely mitigate any air and water 

quality impacts that can result from these activities. Because these impacts occur whether or not the CPA 

proposed action is implemented, the CPA proposed action would account for only a small percentage of 

these impacts.

A detailed description of the baseline affected environment for land use and coastal infrastructure in 

the CPA is provided in Chapter 4.2.1.23.1.1 of the 2012-2017 WPA/CPA Multisale EIS, and updated 

information is provided in Chapter 4.1.1.23.1 of this Supplemental EIS, Chapter 4.2.1.23.1 of the WPA 

233/CPA 231 Supplemental EIS, and Chapter 4.1.1.23.1 of the CPA 235/241/247 Supplemental EIS and 

CPA 241/247 and EPA 226 Supplemental EIS. Chapter 3.1.1.3.2 of the 2012-2017 WPA/CPA Multisale 

EIS describes in detail offshore infrastructure emplacement/structure installation and commissioning 

activities related to a CPA proposed action. 

BOEM projects no new coastal infrastructure; however, any individual proposed action may result in 

one additional pipeline landfall and/or one additional gas processing facility as a result of an individual 

proposed action. While offshore projects may add additional miles of pipeline to transport product, it is 

not likely that these projects would transport natural gas or crude oil directly onshore, but rather 

interconnect with existing systems. Generally, it is more cost effective for companies to tie into the 

existing offshore pipeline network. Pipeline safety regulations govern the entire life of pipeline 

operations, including design, construction, inspection, recordkeeping, worker qualification, and 

emergency preparedness; and any new pipeline landfalls would be subject to regulatory requirements. 

Because of the long timelines associated with the Gulf of Mexico projects, the late 2014/early 2015 

downturn in oil prices is expected to have minimal direct impact on GOM crude oil production through 

2016. The U.S. Department of Energy’s (DOE or USDOE’s) Energy Information Administration projects 

GOM production to reach 1.52 MMbbl per day in 2015 and 1.61 MMbbl per day in 2016, or about 

16 percent and 17 percent of total U.S. crude oil production in those 2 years, respectively. The current 

low oil prices adds uncertainty to the timelines of deepwater GOM projects, with projects in early 

development stages exposed to the greatest risk of delay (USDOE, Energy Information Administration, 

2015f). 

A service base is a community of businesses that load, store, and supply equipment, supplies, and 

personnel that are needed at offshore work sites. Service bases can range from large yards offering a 

range of services, including full logistics management to smaller shops that supply one or many of the 

items needed on an offshore platform or marine vessel. The GOM ports vary considerably by size, 

specialty, and defining characteristics. In general, however, there are two major types of port facilities: 

deep-draft seaports and inland river and intra-coastal waterways port facilities (Dismukes, 2011). While 

no proposed action is projected to significantly change existing OCS oil- and gas-related service bases or 

ports, or require any additional ports or service bases, the CPA proposed action would contribute to the 

use of these coastal infrastructure types. Round-trip service vessel trips as a result of the CPA proposed 

action are projected between 94,000 and 168,000 over the 40-year planning period (Table 3-2). For a 

more in depth discussion of service vessels, refer to Chapter 3.1.1.8. 

Chapter 4.2.1.23.1 describes shipbuilding and shipyards in the analysis areas. In the GOM region, 

there is a direct correlation between oil and gas activities and the demand or opportunities for expanding 

shipbuilding and offshore support vessels. There are 137 shipyards in the analysis area, with the highest 

concentration in Louisiana at 64; there are 32 in Texas, 9 in Mississippi, 18 in Alabama, and 14 in Florida 

(Dismukes, 2011). No new facilities are expected to be constructed as a result of the CPA proposed 

action or in support of OCS Program activities. There is more than an adequate supply of shipyard 

resources in the GOM. No new facilities are expected to be constructed in support of OCS Program 

activities. Some shipyards may close, be bought out, or merge over the 2012-2051 period, resulting in 

fewer active yards in the analysis area.

If offshore oil and gas activity levels increase, it is reasonable to assume that heliport facilities may 

expand to meet demand. Helicopter hubs or “heliports” are facilities where helicopters can land, load, 

and offload passengers and supplies, refuel, and be serviced. These hubs are used primarily as flight 

support bases to service the offshore oil and gas industry. Most of the helicopter operations originate at 

helicopter hubs in coastal Louisiana (Dismukes, 2011). Helicopter operations for the CPA proposed 

action are projected between 696,000 and 1,815,000 round-trip operations over the 40-year planning 
Impact-Producing Factors and Scenario 3-17

period (Table 3-2). No new heliports are projected as a result of the OCS Program; however, if activity 

levels increase, current locations may expand.

The DOE’s Energy Information Administration updates national energy projections annually, 

including refinery capacity. A crude oil refinery is a group of industrial facilities that turns crude oil and 

other inputs into finished petroleum products. No new facilities are expected to be constructed as a result 

of the CPA proposed action. For many years, financial, environmental, and legal considerations have 

made it unlikely that new refineries will be built in the United States, and this is expected to continue. 

Therefore, expansions at existing refineries, rather than new refinery construction, will eventually 

increase total U.S. refining capacity over the 2012-2051 period. 

Navigation channels undergo maintenance dredging that is essential for sustaining proper water 

depths to allow ships to move safely through the waterways to ports, services bases, and terminal 

facilities. In the northern GOM, the existing system of navigation channels is projected to be adequate to 

allow proper accommodation for vessel traffic that will occur as a result of a single CPA proposed action. 

The Gulf-to-port channels and the Gulf Intracoastal Waterway that support prospective OCS ports are 

maintained by regular dredging and are generally sufficiently deep and wide to handle OCS oil- and gasrelated traffic (refer to Table 3-7 of the CPA 235/241/247 Supplemental EIS for the CPA proposed

action). BOEM projects that no new navigation channels will be authorized and constructed during the 

years 2012-2051 as a direct result of the OCS Program. 

3.1.2.2. Discharges and Wastes

Chapter 3.1.2.2 of the 2012-2017 WPA/CPA Multisale EIS describes in detail coastal discharges and 

wastes, and Chapter 3.1.2.2 of the WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247

Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS provide a summary and update to 

coastal discharges and wastes for a CPA proposed action. Information covered includes the following: 

• disposal and storage for offshore operational wastes; 

• onshore facility discharges; 

• coastal service-vessel discharges; 

• offshore wastes disposed onshore; and

• beach trash and debris. 

The USEPA, through general permits issued by the USEPA Region with jurisdictional oversight, 

regulates all waste streams generated from offshore oil and gas activities. The USEPA Region 6 has 

jurisdiction over the CPA off the Louisiana coast. The USEPA Region 4 has jurisdiction over the eastern 

portion of the GOM, including part of the CPA off the coasts of Alabama and Mississippi. Each region 

has promulgated general permits for discharges that incorporate the 1993 effluent guidelines as a 

minimum. In some instances, a site-specific permit is required. The USEPA also regulates vessel 

discharges with the Vessel General Permit (VGP), which is a Clean Water Act National Pollutant 

Discharge Elimination System (NPDES) permit that authorizes, on a nationwide basis, discharges 

incidental to the normal operation of nonmilitary and nonrecreational vessels greater than or equal to 79 ft 

(24 m) in length. On March 28, 2013, the USEPA reissued the 2008 VGP for another 5 years; the 

reissued permit, the 2013 VGP, now contains numeric ballast water discharge limits for most vessels. 

The VGP also contains more stringent effluent limits for oil-to-sea interfaces and exhaust gas scrubber 

washwater (USEPA, 2013). The VGP, geographically, covers inland waters out to 3 mi (5 km) and 

applies to vessels acting as a means of transportation. If the vessel is moored to a rig generating an 

amount of water that is greater than what it takes for the normal operation of a vessel, the VGP would not 

apply to brine production. As of early March 2015, a bipartisan effort to establish a uniform national 

framework for the regulation of vessel discharges took another step forward as the Senate Committee on 

Commerce, Science and Transportation approved Senate Bill 373, the Vessel Incidental Discharge Act. 

The measure would replace a patchwork of overlapping and conflicting Federal and State regulations with 

a uniform Federal framework for vessel discharge regulation (MarineLog, 2015).

The BSEE policy regarding marine debris prevention is outlined in NTL 2012-BSEE-G01, “Marine 

Trash and Debris Awareness and Elimination.” The NTL instructs OCS operators to post informational 
3-18 Central Planning Area Lease Sale 247 Supplemental EIS

placards that outline the legal consequences and potential ecological harms of discharging marine debris. 

The NTL also states that OCS workers should complete annual marine debris prevention training and 

instructs operators to develop a certification process for the completion of this training by their workers. 

These various laws, regulations, and the aforementioned NTL will likely minimize the discharge of

marine debris from OCS operations. 

For the CPA proposed action, existing onshore facilities would continue to be used to dispose of 

wastes generated offshore. However, no new disposal facilities are expected to be licensed as a direct 

result of the CPA proposed action. There is no current expectation for new onshore waste disposal

facilities to be authorized and constructed during the 2012-2051 period as a direct result of the OCS 

Program. If needed, existing facilities may undergo expansion, but no new disposal facilities are 

expected. 

3.2. IMPACT-PRODUCING FACTORS AND SCENARIO—ACCIDENTAL EVENTS

3.2.1. Oil Spills

Oil-spill occurrence cannot be predicted, but an estimate of its likelihood can be quantified using spill 

rates derived from historical data and projected volumes of oil produced and transported. The following 

chapters discuss spill prevention and spill response, and analyze the risk of spills that could occur as a 

result of activities associated with the CPA proposed action. Public input through public scoping 

meetings, Federal and State agencies’ input through consultation and coordination, and industry and 

nongovernmental organizations’ input indicate that oil spills are perceived to be a major concern. The 

following chapters analyze the risk of spills that could occur as a result of a typical CPA proposed action, 

as well as information on the number and sizes of spills from non-OCS sources. Since the potential 

occurrence of a catastrophic spill is exceedingly low (Ji et al., 2014), it is not expected as a result of a 

CPA proposed action. However, it cannot be ruled out entirely; refer to Appendix B for the 

“Catastrophic Spill Event Analysis.”

3.2.1.1. Spill Prevention

Over the years, comprehensive pollution-prevention requirements that include redundant safety 

systems, as well as inspection and testing requirements to confirm that these devices are working 

properly, have been established (Chapter 1.5). During the 40 years before the Deepwater Horizon oil 

spill, an overall reduction in spill volume had occurred, while oil production generally increased. A 

characterization of spill rates and the average and median volumes from 1995 to 2009 compared with 

1996 to 2010, which includes the Deepwater Horizon oil spill, is provided in Update of Occurrence Rates 

for Offshore Oil Spills (Anderson et al., 2012). BOEM attributes this improvement to BSEE’s operational 

requirements, ongoing efforts by the oil and gas industry to enhance safety and pollution prevention, and 

the evolution and improvement of offshore technology. 

3.2.1.2. Past OCS Spills

The BSEE spill-event database includes records of past spills from activities that are regulated by 

BOEM and BSEE. These data include oil spills >1 bbl that occurred in Federal waters from OCS 

facilities and pipeline operations. Spills from facilities include spills from drilling rigs, drillships, and 

storage, processing, or production platforms that occurred during OCS drilling, development, and 

production operations. Spills from pipeline operations are those that have occurred on the OCS and are 

directly attributable to the transportation of OCS oil. Anderson et al. (2012) was utilized in the 2012-

2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental 

EIS, and CPA 241/247 and EPA 226 Supplemental EIS for a CPA proposed action to characterize spill 

rates and to provide analysis for average and median volumes. The analysis by Anderson et al. (2012) 

examined spill data for the period 1964 to 2010, including the Deepwater Horizon oil spill.

A search of BSEE’s oil-spill database (USDOI, BSEE, 2015a) was performed to assess new spill 

information to provide an update to the Anderson et al. (2012) analysis. The most recent data available 

provide additional information for the period 2011 to 2013, during which 46 spills from OCS oil- and 

gas-related activities of <1,000 bbl in size were reported. The breakdown of the 46 spills <1,000 bbl that 
Impact-Producing Factors and Scenario 3-19

occurred from 2011 to 2013 from OCS oil- and gas-related activities is as follows: 28 spills of 1-4 bbl; 

6 spills of 5-9 bbl; 10 spills of 10-49 bbl; 1 spill of 50-99 bbl; 1 spill of 100-999 bbl; and 0 spills of 

≥1,000 bbl. The combined total of oil spilled in these 46 events was 857 bbl. The BSEE database 

(USDOI, BSEE, 2015b) indicated that there were two spills (one in 2011 and one in 2012) that were 

between 50 and 500 bbl in size, both of which occurred in the CPA. The spill of 67 bbl in 2011 was the 

result of equipment failure from a platform leak located in Garden Banks Block 72. The spill in 2012 was 

estimated at 480 bbl and resulted from an explosion on a platform located in West Delta Block 32. In 

summary, two spills >50 bbl occurred during the period 2011 to 2013. This is an outcome that is within 

the range of spills estimated to occur in Table 3-12 of the 2012-2017 WPA/CPA Multisale EIS, which 

provides an estimate of the number and size of spills likely to occur as a result of the CPA proposed

action over a 40-year time period. Thus, the additional information provided by the review of BSEE’s 

oil-spill database did not change the validity of the scenario previously presented. 

The majority of the 2011-2013 spills are attributed to OCS oil- and gas-related platforms/rigs, 

followed by vessels, and lastly by OCS oil- and gas related pipelines. These data were compared with the 

estimated number and size of spills presented in Table 3-12 of the 2012-2017 WPA/CPA Multisale EIS 

and it was found that the new spill data were within the spill numbers estimated in the prior 2012-2017 

Gulf of Mexico EISs. The new data also supported the previous finding that the most likely source of a 

spill would be from platforms, rigs, or vessels. Thus, a review of recent information does not change the 

risk analyses for spills <1,000 bbl previously provided in the 2012-2017 WPA/CPA Multisale EIS, WPA 

233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 

Supplemental EIS. As estimated in Table 3-12 of the 2012-2017 WPA/CPA Multisale EIS, no spills have 

occurred in the ≥1,000-bbl size class.

3.2.1.3. Characteristics of OCS Oil

The physical and chemical properties of oil greatly affect its transport and ultimate fate in the 

environment and determine the following: how oil will behave on the water surface (surface spills) or in 

the water column and sediments (subsea spills); the persistence of the slick on the water; the type and 

speed of weathering processes; the degree and mechanisms of toxicity; the effectiveness of containment 

and recovery equipment; and the ultimate fate of the spill residues. Crude oils are a natural mixture of 

hundreds of different compounds, with liquid hydrocarbons accounting for up to 98 percent of the total 

composition. The chemical composition of crude oil can vary significantly from different producing 

areas; thus, the exact composition of oil being produced in OCS waters varies throughout the Gulf. The 

American Petroleum Institute gravity (API gravity) is a measure of the relative density of oil compared 

with water and is expressed in degrees (°). Oils with an API gravity <10 are heavier and typically sink, 

whereas oils with an API gravity >10 are lighter and typically float. Following an oil spill, the 

composition of the released oil can change substantially due to weathering processes such as evaporation, 

emulsification, dissolution, and oxidation. More details on the properties and persistence of different 

types of oils are provided in Table 3-8 of the CPA 241/247 and EPA 226 Supplemental EIS. 

Extensive laboratory testing has been performed on various oils from the GOM to determine their 

physical and chemical characteristics. For example, numerous oils collected from the GOM (U.S. waters) 

are included in Environment Canada’s (2013) oil properties database. The database provides details of an 

oil’s chemical composition including hydrocarbon groups (i.e., saturates, aromatics, resins, and 

asphaltenes), VOCs (such as benzene, toluene, ethylbenzene, and xylene), sulfur content, biomarkers, and 

metals. The database also includes API gravities, of which GOM oils are in the range, of 15° to 60°. 

Additional data have been collected from approximately 450 deepwater exploration plans (EP) and 

DOCDs that were submitted to BOEM/BSEE. These data are available through BOEM’s Exploration and 

Development Plans Online Query (refer to USDOI, BOEM, 2014b). Statistics on these API gravities 

result in a similar range (16° to 58°) as previously reported, with a mean value of 36°. These new data 

corroborate the information previously presented in the 2012-2017 WPA/CPA Multisale EIS, WPA 

233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 

Supplemental EIS.
3-20 Central Planning Area Lease Sale 247 Supplemental EIS

3.2.1.4. Overview of Spill Risk Analysis

There are many factors that BOEM evaluates to determine the risk of impact occurring from an oil 

spill, including likely spill sources, likely spill locations, likely spill sizes, the likelihood and frequency of 

occurrence for different size spills, timeframes for the persistence of spilled oil, volumes of oil removed 

due to weathering and cleanup, and the likelihood of transport by wind and waves resulting in contact to 

specified environmental features. Sensitivity of the environmental resources and potential effects are 

addressed in the analyses for the specific resources of concern (Chapter 4.1.1). BOEM uses data on past 

OCS production and spills, along with estimates of future production, to evaluate the risk of future spills. 

Additionally, BOEM uses a numerical model to calculate the likely trajectory of spills (i.e., transport 

pathways) and analyzes historical data of occurrence rates for oil spills (refer to Anderson et al., 2012) to 

make projections of future oil-spill frequency and size. A more detailed description of the spill risk 

analysis and the trajectory model, called OSRA (oil-spill risk analysis) model, were provided in Chapter 3 

of the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 

Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS as well as in the Ji et al. (2012) 

OSRA report. Appendix C of the CPA 235/241/247 Supplemental EIS also contains the OSRA model’s 

catastrophic spill event results to estimate the risks associated with a possible future low-probability 

catastrophic or high-volume, long-duration oil spill.

The OSRA model’s results and estimated spill size/frequency tables as presented and discussed in the 

2012-2017 WPA/CPA Multisale EIS remain applicable because the basic assumptions inherent in the 

model and calculations are still valid. The latest analysis available for the characterization of spill rates 

and for average and median volumes (Anderson et al., 2012) inputted into the model is still valid because 

the more recent small OCS spills (2011-2013) were within spill scenario estimates developed using the 

past data. In addition, the physical forcing (e.g., ocean currents and wind fields) and environmental 

resources input (e.g., locations and seasonality of various biological resources) to the OSRA model are 

still representative of our current state of knowledge regarding both ocean modeling and potential 

environmental resources at risk. Numerous efforts are underway since the Deepwater Horizon oil spill to 

further improve trajectory modeling in the Gulf of Mexico, including several BOEM environmental 

studies (e.g., refer to Section 4.2 in Ji et al., 2013). However, the results of these new research activities 

are not yet available or fully tested for incorporation into BOEM’s oil-spill risk analysis. Thus, new 

information did not change the results of previous spill risk analyses provided in the 2012-2017 

WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, 

and CPA 241/247 and EPA 226 Supplemental EIS. 

The following discussions provide risk information for offshore and coastal spills that may result 

from the CPA proposed action. This analysis is divided into discussions of offshore spills ≥1,000 bbl, 

offshore spills <1,000 bbl, and coastal spills of any spill volume. Only spills ≥1,000 bbl are addressed 

using OSRA because smaller spills typically do not persist long enough to be simulated by trajectory 

modeling. 

3.2.1.5. Risk Analysis for Offshore Spills ≥1,000 bbl

Chapter 3.2.1.5 of the 2012-2017 WPA/CPA Multisale EIS addressed the risk of spills ≥1,000 bbl 

that could occur from accidents associated with activities resulting from a CPA proposed action. The risk 

analyses included the following:

• estimated number of offshore spills ≥1,000 bbl and probability of occurrence; 

• most likely source of offshore spills ≥1,000 bbl; 

• most likely size of an offshore spill ≥1,000 bbl; 

• fate of offshore spills ≥1,000 bbl; 

• transport of spills ≥1,000 bbl by winds and currents; 

• length of coastline affected by offshore spills ≥1,000 bbl; and
Impact-Producing Factors and Scenario 3-21

• likelihood of an offshore spill ≥1,000 bbl occurring and contacting modeled locations 

of environmental resources.

Specifically, Table 3-19 of the 2012-2017 WPA/CPA Multisale EIS estimated that the mean number 

of spills ≥1,000 bbl was ≤1 spill (mean equal to 0.5-1.0) from both OCS oil- and gas-related platforms 

and pipelines. Because no spills ≥1,000 bbl in size have occurred during 2011-2013, use of Anderson 

et al. (2012) remains applicable and up-to-date for characterizing spill rates and average and median spill 

volumes in this Supplemental EIS. In terms of weathering, fate, and transport of oil spills in the Gulf of 

Mexico, a variety of ongoing studies are providing more insights in the aftermath of the Deepwater

Horizon oil spill. For example, recent studies have provided further evidence that the diverse microbial 

communities in both the water column (e.g., Mason et al., 2012) and sediments (Kimes et al., 2013) of the 

GOM can play an active role in metabolizing and bioremediating crude oil from offshore spills. Further 

research is also being conducted regarding what impact chemical dispersant application may have on this 

biodegradation process. Other research on oil fates suggests that marine snow formation in the aftermath 

of a large oil-spill event (such as the Deepwater Horizon oil spill) may play a key role in the fate of 

surface oil (e.g., Passow et al., 2012). A review of recent information does not change the quantitative 

risk analyses for spills ≥1,000 bbl previously provided in the 2012-2017 WPA/CPA Multisale EIS, WPA 

233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 

Supplemental EIS. 

3.2.1.6. Risk Analysis for Offshore Spills <1,000 bbl

Chapter 3.2.1.6 of the 2012-2017 WPA/CPA Multisale EIS addressed the risk of spills <1,000 bbl 

resulting from a CPA proposed action. Analysis of historical data shows that most offshore OCS oil 

spills fall within this category, with the majority of spills falling within the significantly smaller range of 

≤1 bbl (Anderson et al., 2012). Although spills of ≤1 bbl amount to 96 percent of all OCS oil- and gasrelated spill occurrences, they have contributed very little to the total volume of oil spilled. The risk 

analyses addressed in Chapter 3.2.1.6 of the 2012-2017 WPA/CPA Multisale EIS for a CPA proposed 

action included the following: 

• estimated number of offshore spills <1,000 bbl and total volume of oil spilled; 

• most likely source and type of offshore spills <1,000 bbl; 

• most likely size of offshore spills <1,000 bbl; 

• persistence, spreading, and weathering of offshore oil spills <1,000 bbl; 

• transport of spills <1,000 bbl by winds and currents; and 

• likelihood of an offshore spill <1,000 bbl occurring and contacting modeled locations 

of environmental resources.

A search of BSEE’s oil-spill database (USDOI, BSEE, 2015a) was performed to assess new spill 

information that was not analyzed in Anderson et al. (2012). During 2011-2013, there were 46 spills from 

OCS oil- and gas-related activities of <1,000 bbl in size, totaling 857 bbl overall. The breakdown of these 

spills into size classes is provided in Chapter 3.2.1.2. As noted above, the 2011-2013 spill data were 

compared with the estimated number and sizes of spills presented in Table 3-12 of the 2012-2017 

WPA/CPA Multisale EIS and they were found to be within the spill numbers estimated in the previous 

documents. The new data also supported previous findings that the most likely source of a spill of <1,000 

bbl would be from platforms, rigs, or vessels. Thus, a review of recent information does not change the 

risk analyses for spills <1,000 bbl previously provided in Chapter 3.2.1.6 of the 2012-2017 WPA/CPA 

Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 

241/247 and EPA 226 Supplemental EIS. 
3-22 Central Planning Area Lease Sale 247 Supplemental EIS

3.2.1.7. Risk Analysis for Coastal Spills 

Spills in coastal waters could occur at storage or processing facilities supporting the OCS oil and gas 

industry or from the transportation of OCS-produced oil through State offshore waters and along 

navigation channels, rivers, and through coastal bays. BOEM projects that almost all (>99%) oil 

produced as a result of a CPA proposed action will be brought ashore via pipelines to oil pipeline shore 

bases, stored at these facilities, and eventually transferred via pipeline or barge to Gulf coastal refineries. 

Because oil is commingled at shore bases and cannot be directly attributed to a particular lease sale, this 

analysis of coastal spills addresses spills that could occur prior to the oil arriving at the initial shoreline 

facility. It is also possible that non-OCS oil may be commingled with OCS oil at these facilities or during 

subsequent secondary transport. Chapter 3.2.1.7 of the 2012-2017 WPA/CPA Multisale EIS describes in 

detail the estimated number and most likely sizes of coastal spills and the likelihood of coastal spill 

contact. 

The number and most likely spill sizes to occur in coastal waters in the future are expected to 

resemble the patterns that have occurred in the past, as long as the level of hydrocarbon use by 

commercial and recreational activities remains generally the same. Estimates of future coastal spills are 

based on the number and location of historical coastal spills reported to USCG. Based on the USCG’s 

historical data for the GOM region, Louisiana and Texas are attributed the highest probability of having a 

spill ≥1,000 bbl occur in coastal waters. 

3.2.1.8. Risk Analysis by Resource

BOEM previously analyzed the risk to resources from oil spills and oil slicks that could occur as a 

result of a CPA proposed action in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 

Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental 

EIS. The risk results were based on BOEM’s estimates of likely spill locations, sources, sizes, frequency 

of occurrence, physical fates of different types of oil slicks, and probable transport that were described in 

more detail in specific spill scenarios. For offshore spills ≥1,000 bbl, combined probabilities were 

calculated using the OSRA model, which includes both the likelihood of a spill from the CPA proposed

action occurring and the likelihood of the oil slick reaching areas where known environmental resources 

exist. The analysis of the likelihood of direct exposure and interaction of a resource with an oil slick and 

the sensitivity of a resource to the oil is provided under each resource category in Chapter 4.1.1 of this 

Supplemental EIS and was provided in Chapter 4.1.2 of the 2012-2017 WPA/CPA Multisale EIS, WPA 

233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 

Supplemental EIS, and Chapter 3.2.1.8 and Figures 3-8 through 3-28 of the 2012-2017 WPA/CPA 

Multisale EIS.

3.2.1.9. Spill Response

For a CPA proposed action, Chapter 3.2.1.9 of the 2012-2017 WPA/CPA Multisale EIS describes in 

detail issues related to offshore spill-response requirements and initiatives; offshore response, 

containment, and cleanup technology; and onshore response and cleanup. Additional information and 

updates to the 2012-2017 WPA/CPA Multisale EIS have been included within respective sections of the 

WPA 233/CPA 231 Supplemental EIS, WPA 233/ CPA 231 Supplemental EIS, CPA 235/241/247 

Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS. 

As a result of the Oil Pollution Act of 1990 and the reorganization of the Bureau of Ocean Energy 

Management, Regulation and Enforcement into BOEM and BSEE in 2010, BSEE was tasked with a 

number of oil-spill response duties and planning requirements. The BSEE implements the following 

requirements according to BSEE’s regulations at 30 CFR parts 250 and 254: 

• requires immediate notification for spills ≥1 bbl—all spills require notification to 

USCG, and BSEE also receives notification from the USCG of all spills ≥1 bbl; 

• conducts investigations to determine the cause of a spill;

• assesses civil and criminal penalties, if needed;

• oversees spill source control and abatement operations by industry;
Impact-Producing Factors and Scenario 3-23

• sets requirements and reviews and approves oil spill response plans (OSRPs) for 

offshore facilities;

• conducts unannounced drills to ensure compliance with OSRPs;

• requires operators to ensure that their spill-response operating and management 

teams receive appropriate spill-response training; 

• conducts inspections of oil-spill response equipment;

• requires industry to show financial responsibility to respond to possible spills; and 

• provides research leadership to improve the capabilities for detecting and responding 

to an oil spill in the marine environment. 

BOEM also has regulatory requirements addressing site-specific OSRPs and spill response 

information. In accordance with BOEM’s regulations at 30 CFR §§ 550.219 and 550.250, operators must 

have an approved OSRP prior to BOEM’s approval of an operator-submitted exploration, development, 

or production plan. Operators are, therefore, required to provide BOEM an OSRP that is prepared in 

accordance with 30 CFR part 254 subpart B with their proposed exploration, development, or production 

plan for the facilities that they will use to conduct their activities; or to alternatively reference their 

approved regional OSRP by providing the following information: 

• a discussion of the approved OSRP;

• the location of the primary oil-spill equipment base and staging area;

• the name of the oil-spill equipment removal organization(s) for both equipment and 

personnel; 

• the calculated volume of the worst-case discharge scenario in accordance with 

30 CFR § 254.26(a) and a comparison of the worst-case discharge scenario in the 

approved regional OSRP with the worst-case discharge calculated for these proposed 

activities; and

• a description of the worst-case discharge to include the trajectory information, 

potentially impacted resources, and a detailed discussion of the spill response 

proposed to the worst-case discharge in accordance with 30 CFR §§ 254(b)-(d).

All OSRPs are reviewed and approved by BSEE, whether submitted with a BOEM-associated plan or 

directly to BSEE in accordance with 30 CFR part 254. Hence, BOEM relies heavily upon BSEE’s 

expertise to ensure that the OSRP complies with all pertinent laws and regulations, and demonstrates the 

ability of an operator to respond to a worst-case discharge. The operator is also required to carry out the 

training, equipment testing, and periodic drills described in the OSRP. Since 1989, BSEE has conducted 

government-initiated unannounced exercises that provide an economically feasible mechanism for 

agencies to comply with the requirements defined in 30 CFR part 254. In 2014, BSEE carried out seven

table-top, government-initiated unannounced exercises and two deployment government-initiated 

unannounced exercises (USDOI, BSEE, 2014a). Equipment deployment exercises most often take place 

in waterways adjacent to where the equipment is stored, but they may be moved if the exercise requires it. 

Typical deployment exercises last only a few hours and rarely longer than a day (USDOI, BSEE, official 

communication, 2015c). The NTLs and guidance documents issued by BOEM and BSEE prior to 2012 

that clarify additional oil-spill requirements since the Deepwater Horizon explosion, oil spill, and 

response occurred are described in detail in Chapter 3.2.1.9 of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 

226 Supplemental EIS. 

The NTL 2012-BSEE-N06, “Guidance to Owners and Offshore Facilities Seaward of the Coast Line 

Concerning Regional Oil Spill Response Plans,” which was effective on August 10, 2012, provides 

clarification, guidance, and information concerning the preparation and submittal of a regional OSRP for 

owners and operators of oil handling, storage, or transportation facilities, including pipelines located 
3-24 Central Planning Area Lease Sale 247 Supplemental EIS

seaward of the coastline. Some of the clarifications and encouraged practices that are identified in NTL 

2012-BSEE-N06 and that are based upon lessons learned from the Deepwater Horizon oil-spill response 

are described in detail in the CPA 241/247 and EPA 226 Supplemental EIS. 

The BSEE has also issued NTL 2013-BSEE-N02, “Significant Change to Oil Spill Response Plan 

Worst Case Discharge Scenario” to clarify what BSEE considers a significant change in a worst-case 

discharge scenario, which requires that a revision to an OSRP be submitted. Details of the guidance 

issued by this NTL are discussed in the CPA 241/247 and EPA 226 Supplemental EIS. 

The BSEE also issued NTL 2012-BSEE-N07, “Oil Discharge Written Follow-up Reports,” to address 

the oil discharge reports (30 CFR § 254.46(b)(2)) that are required to be submitted by a responsible party 

to BSEE for spills ≥1 bbl within 15 days after a spill has been stopped or ceased. The responsible party is 

encouraged to report cause, location, volume, remedial action taken, sea state, meteorological conditions, 

and the size and appearance of the slick.

Mechanical Cleanup

As previously indicated, BSEE oversees a research program to improve the capabilities for detecting 

and responding to an oil spill in the marine environment. One of BSEE’s recently completed research 

projects suggested an alternative to improve the present regulatory requirements at 30 CFR § 254.44 for 

determining the effective daily recovery capacity of spill-response skimming equipment. The suggested 

alternative considers the encounter rate of a skimming system with spilled oil as a measure of effective 

daily recovery capacity instead of the presently used de-rated pump capacity of a skimmer. This project 

was undertaken because the Deepwater Horizon oil-spill response highlighted that the existing regulation 

may not be an effective or accurate planning standard or a predictor of oil-spill response equipment 

recovery capacity. The project was completed in 2012 and the National Academy of Sciences completed 

a peer review in 2013. The BSEE’s Gulf of Mexico OCS Region is presently using the results of this 

study in its OSRP reviews.

There have been some changes to the spill-response equipment staging locations previously reported 

in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, and CPA 

235/241/247 Supplemental EIS. Due to these changes, it is expected that the oil-spill response equipment 

needed to respond to an offshore spill in a proposed lease sale area could be called out from one or more 

of the following oil-spill equipment base locations: New Iberia, Belle Chasse, Baton Rouge, Sulphur, 

Morgan City, Port Fourchon, Harvey, Houma, Galliano, Leeville, Fort Jackson, Venice, Grand Isle, or 

Lake Charles, Louisiana;, Corpus Christi, Port Arthur, Aransas Pass, Ingleside, Galveston, or Houston, 

Texas; Pascagoula or Kiln, Mississippi; Mobile or Bayou La Batre, Alabama; and/or Panama City, 

Pensacola, Tampa, and/or Miami, Florida (Clean Gulf Associates, 2015; Marine Spill Response 

Corporation, 2015; National Response Corporation, 2015).

Dispersants

The USEPA has recently issued a proposed rule to amend the requirements in Subpart J of the 

National Oil and Hazardous Substances Pollution Contingency Plan (NCP) that governs the use of 

dispersants, other chemical and biological agents, and other spill mitigating substances when responding 

to oil discharges into waters of the United States. The proposal addresses the efficacy, toxicity, 

environmental monitoring of dispersants, and other chemical and biological agents, as well as public, 

local, State, and Federal officials’ concerns regarding their use (Federal Register, 2015b). The USEPA 

also updated the NCP product schedule in 2014. The 2014 NCP Product Schedule authorizes dispersants, 

surface washing agents, surface collecting agents, bioremediation agents, and miscellaneous oil-spill 

control agents for use on oil discharges. 

In February 2014, the USEPA published an NCP Product Schedule Notebook that presents 

manufacturers’ summary information that describes (1) the conditions under which each of the products is 

recommended for use, (2) handling and worker precautions, (3) storage information, (4) recommended 

application procedures, (5) physical properties, (6) toxicity information, and (7) effectiveness information 

(USEPA, 2014). 

Due to the unprecedented volume of dispersants applied for an extended period of time in situations 

not previously envisioned or incorporated in existing dispersant use plans during the Deepwater Horizon

oil-spill response, the U.S. National Response Team has developed guidance for monitoring atypical 
Impact-Producing Factors and Scenario 3-25

dispersant operations. The guidance document, which was approved on May 30, 2013, is titled 

Environmental Monitoring for Atypical Dispersant Operations: Including Guidance for Subsea 

Application and Prolonged Surface Application. The subsea guidance generally applies to the subsurface 

ocean environment and focuses on operations in waters below 300 m (984 ft) and below the pycnocline 

(or below the subsea layer where the density gradient is the greatest). The surface application guidance 

supplements and complements the existing protocols as outlined within the existing Special Monitoring of 

Applied Response Technologies (SMART) monitoring program where the duration of the application of 

dispersants on discharged oil extends beyond 96 hours from the time of the first application (U.S. 

National Response Team, 2013). This guidance is provided to the Regional Response Teams by the U.S. 

National Response Team to enhance existing SMART protocols and to ensure that their planning and 

response activities will be consistent with national policy.

Shoreline Cleanup Countermeasures

In addition, the USCG improved coastal oil-spill response since the Deepwater Horizon oil spill by 

replacing the One Gulf Plan with separate Area Contingency Plans (ACPs) for each coastal USCG sector. 

The ACPs cover sub-regional geographic areas and represent the third tier of the National Response 

Planning System mandated by the Oil Pollution Act of 1990. The ACPs are a focal point of response 

planning. The Gulf of Mexico OCS Region’s ACPs also include separate Geographic Response Plans, 

which are developed jointly with local, State, and other Federal entities to better focus spill-response 

tactics and priorities. These Geographic Response Plans, which will be periodically revisited, contain the 

resources initially identified for protection during a spill, response priorities, procedures, and appropriate 

spill-response countermeasures.

3.2.2. Losses of Well Control

All losses of well control must be reported to BSEE. The BSEE clarified its procedure for loss of 

well control incident reporting in NTL 2010-N05, “Increased Safety Measures for Energy Development 

on the OCS,” which became effective on June 8, 2010. The BSEE Drilling Safety Rule (Federal 

Register, 2012a) became effective on October 22, 2012. This rule implements certain additional safety 

measures recommended in NTL 2010-N05 by incorporating the recommendations contained in the DOI 

report Increased Safety Measures for Energy Development on the Outer Continental Shelf (Safety 

Measures Report; USDOI, 2010), and the Deepwater Horizon Joint Investigation Team report (USDOI, 

BOEMRE and USDHS, CG, Joint Investigation Team, 2013). The BSEE amended the drilling, wellcompletion, well-workover, and decommissioning regulations related to well control, including subsea 

and surface blowout preventers, well casing and cementing, secondary intervention, unplanned 

disconnects, recordkeeping, and well plugging. The Drilling Safety Rule also enhanced the description 

and classification of well-control barriers, defined testing requirements for cement, clarified requirements 

for the installation of dual mechanical barriers, and extended requirements for blowout preventers (BOPs) 

and well-control fluids to well-completions, workovers, and decommissioning operations. Operators are 

required to document any loss of well-control event, even if temporary, and the cause of the event, and 

they are required to furnish that information by mail or email to the addressee indicated in the NTL. The 

operator does not have to provide information on kicks that were controlled, but the operator should 

include the release of fluids through a flow diverter (a conduit used to direct fluid flowing from a well 

away from the drilling rig). 

The current definition for loss of well control is as follows:

• uncontrolled flow of formation or other fluids (the flow may be to an exposed 

formation [an underground blowout] or at the surface [a surface blowout]);

• uncontrolled flow through a diverter; and/or 

• uncontrolled flow resulting from a failure of surface equipment or procedures. 

A loss of well control can occur during any phase of development, i.e., exploratory drilling, 

development drilling, well completion, production, or workover operations. From 2007 to 2014, of the 

47 loss of well-control events reported in the GOM, 25 (53%) resulted in loss of fluids at the surface or 
3-26 Central Planning Area Lease Sale 247 Supplemental EIS

underground (USDOI, BSEE, 2015b). In addition to spills, the loss of well control can resuspend and 

disperse bottom sediments. Historically, since 1971, most OCS blowouts have resulted in the release of 

gas, while blowouts resulting in the release of oil have been rare.

A BOP is a device with a complex of choke lines and hydraulic rams mounted atop a wellhead 

designed to close the wellbore with a sharp horizontal motion that may cut through or pinch shut casing 

and sever tool strings. The BOPs were invented in the early 1920’s and have been instrumental in ending 

dangerous, costly, and environmentally damaging oil blowouts on land and in water. The BOPs have 

been required for OCS oil and gas operations from the time offshore drilling began in the late 1940’s. 

The BOPs are actuated as a last resort upon imminent threat to the integrity of the well or the surface 

rig. For a cased well, which is the typical well configuration, the hydraulic ram of a BOP may be closed 

if oil or gas from an underground zone enters the wellbore to destabilize the well. By closing a BOP, 

usually by redundant surface-operated and hydraulic actuators, the drilling crew can prevent explosive 

pressure release and allow control of the well to be regained by balancing the pressure exerted by a 

column of drilling mud with formation fluids or gases from below. Chapter 3.2.1.9.2 of the 2012-2017 

WPA/CPA Multisale EIS provides information on the subsea well containment capability staged in the 

GOM area that could be used by an offshore operator if a loss of well control occurred and resulted in a 

loss of fluids.

3.2.3. Pipeline Failures

The potential mechanisms for damage to OCS pipeline infrastructure include mass sediment 

movements and mudslides that can exhume or push the pipelines into another location, impacts from 

anchor drops or boat collisions, and accidental excavation or breaching because the exact whereabouts of 

a pipeline are uncertain. Pipeline failures could be caused by rig/platform and pipeline activities 

supporting a CPA proposed action. Chapter 3.2.3 of the 2012-2017 WPA/CPA Multisale EIS describes 

previous incidents of OCS oil- and gas-related pipeline failures related to a CPA proposed action. Any 

one of the mechanisms listed above could cause an OCS oil- and gas-related oil spill ≥1,000 bbl. Any 

resulting spill size would be limited by the size of the pipeline and the ability of an operator to quickly 

shut off flow from the source. The median spill size estimated from a pipeline failure is 2,200 bbl (Table 

3-12 of the 2012-2017 WPA/CPA Multisale EIS). For a CPA proposed action, up to one spill of this size 

is estimated to occur during the 40-year analysis period.

3.2.4. Vessel Collisions

The MMS (now BOEM and BSEE) revised vessel operator incident reporting requirements in a final 

rule effective July 17, 2006 (Federal Register, 2006). The incident reporting rule more clearly defines 

what incidents must be reported, broadens the scope to include incidents that have the potential to be 

serious, and requires the reporting of standard information for both oral and written reports. As part of 

the incident reporting rule, BSEE’s regulations at 30 CFR § 250.188(a)(6) require an operator to report all 

collisions that result in property or equipment damage greater than $25,000. “Collision” is defined as the 

act of a moving vessel (including an aircraft) striking another vessel or striking a stationary vessel or 

object (e.g., a boat striking a drilling rig or platform). Chapter 3.2.3 of the 2012-2017 WPA/CPA 

Multisale EIS provides data related to vessel collisions and discusses methods of prevention and 

avoidance of vessel collisions related to a CPA proposed action.

3.2.5. Chemical and Drilling-Fluid Spills

Chapter 3.2.5 of the 2012-2017 WPA/CPA Multisale EIS describes OCS oil- and gas-related 

chemical and synthetic-based fluid spills. Below is a brief summary of that information. 

Chemicals are stored and used to condition drilling muds during exploration and development and in 

well completions, stimulation, and workover procedures. The most common chemicals spilled are 

methanol, ethylene glycol, and zinc bromide. Methanol and ethylene glycol may be used as a treatment to 

prevent the formation of gas hydrates while zinc bromide may be used in completion fluids. Completion 

fluids are used in the largest quantity and constitute the largest volume of accidental releases. Completion 

fluids consist of brines made from seawater mixed with calcium chloride, calcium bromide, and/or zinc 

bromide. A study of chemical spills from OCS oil- and gas-related activities determined that only two 
Impact-Producing Factors and Scenario 3-27

chemicals could potentially impact the marine environment—zinc bromide and ammonium chloride 

(Boehm et al., 2001). Both of these chemicals are used for well treatment or completion and, therefore, 

are not in continuous use. Most other chemicals are either nontoxic or used in small quantities. There are 

some differences in the operational needs for chemicals in deepwater versus shallow-water operations. 

Higher volumes of treatment chemicals (e.g., defoamers and hydrate inhibitors) are used in deepwater 

environments due to the conditions encountered there (Boehm et al., 2001). 

Synthetic-based fluids (SBFs) or synthetic-based muds have been used since the mid-1990’s. In 

deepwater drilling, SBFs are preferred over water-based muds because of the SBFs’ superior performance 

properties. The synthetic oils used in SBFs are relatively nontoxic to the marine environment and have 

the potential to biodegrade. However, it should be noted that SBFs are not permitted to be discharged 

into the marine environment; only cuttings wetted with SBF may be discharged after the majority of 

synthetic fluid has been removed. Additionally, accidental riser disconnects could result in the release of 

large quantities of drilling fluids and are of particular concern when SBFs are in use. For further 

discussion on this topic, refer to Chapter 3.1.1.4.1 of the 2012-2017 WPA/CPA Multisale EIS. Refer to 

Chapter 3.2.5 of the CPA 235/241/247 Supplemental EIS for the most recent information on BSEE’s 

counts and summaries for spills ≥50 bbl. 

3.3. CUMULATIVE ACTIVITIES SCENARIO

The preceding sections of Chapter 3 discuss the impact-producing factors and scenario for routine 

activities and accidental events associated with a CPA that could potentially impact the physical, 

environmental, and socioeconomic resources that are analyzed in this Supplemental EIS. This chapter 

presents a summary of other factors that may cumulatively impact those resources. For a more complete 

and detailed discussion of topics related to cumulative activities related to a CPA proposed action, refer to

Chapter 3.3 of the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 

235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS, which are hereby 

incorporated by reference. 

3.3.1. OCS Program

The OCS Program’s cumulative scenario includes all activities that are projected to occur from past, 

proposed, and future lease sales during the 40-year activity period. Projected reserve/resource production 

for the OCS Program (Table 3-1) is 18.34-25.64 BBO and 75.886-111.627 Tcf of gas. Table 3-3

presents projections of the major activities and impact-producing factors related to future Gulfwide OCS 

Program activities.

The level of OCS oil- and gas-related activity is connected to oil prices, resource potential, cost of 

development, and rig availability rather than just the amount of acreage leased. The impacts of activities 

associated with the OCS Program on biological, physical, and socioeconomic resources are analyzed in 

the cumulative impacts analysis sections of Chapter 4.1.1 of this Supplemental EIS, Chapter 4.2.1 of the 

2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS, and Chapter 4.1.1 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. 

Note that offshore and onshore impact-producing factors and scenarios associated with a WPA or an 

EPA proposed action (i.e., a typical lease sale that would result from a proposed action within the WPA 

or EPA), as well as OCS Program activity resulting from past and future lease sales in the WPA or EPA, 

are disclosed in the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, WPA 

238/246/248 Supplemental EIS, WPA 246/248 Supplemental EIS, EPA 225/226 EIS, and CPA 241/247 

and EPA 226 Supplemental EIS. 

3.3.2. State Oil and Gas Activity

All five Gulf Coast States have had some historical oil and gas exploration activity and, with the 

exception of Florida and Mississippi, currently produce oil and gas in State waters. The coastal 

infrastructure that supports the OCS Program also supports State oil and gas activities.

State oil and gas infrastructure consists of the wells that extract hydrocarbon resources, facilities that 

produce and treat the raw product, pipelines that transport the product to refineries and gas facilities for 

further processing, and additional pipelines that transport finished product to points of storage and final 
3-28 Central Planning Area Lease Sale 247 Supplemental EIS

consumption. The type and size of infrastructure that supports production depends upon the size, type, 

and location of the producing field, the time of development, and the life cycle stage of operations. 

Chapter 3.3.2 of the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 

235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS provides a reference 

for relevant historical information on State leasing programs for a CPA proposed action. The most recent 

lease sale information for Texas and Louisiana has been updated below.

Texas 

The most recent State oil and gas lease sale occurred on January 20, 2015. Fifty-one parcels 

containing 24,850 ac (10,056 ha) of State lands were offered for oil and gas leasing in the offshore area 

(State of Texas, General Lands Office, 2015a). A total of eight bids were received on 4,400 ac (1,780 ha) 

(State of Texas, General Lands Office, 2015b). BOEM expects that Texas will conduct regular oil and 

gas lease sales during the 40-year cumulative activities scenario for OCS oil- and gas-related activity, 

although the lease sale’s regularity could differ from current practices.

Louisiana

During the 2014 Fiscal Year, the State of Louisiana offered 37 tracts for lease offshore, 17 of which 

were awarded. BOEM expects that Louisiana will conduct regular oil and gas lease sales during the 

40-year cumulative activities scenario for OCS oil- and gas-related activity, although the lease sale’s 

regularity could differ from current practices (State of Louisiana, Dept. of Natural Resources, 2015). 

Mississippi

Per conversations with the Mississippi Development Authority (2012), BOEM expects Mississippi to 

institute a lease sale program in the near future and to begin leasing in State waters during the 40-year 

cumulative activities scenario for OCS oil- and gas-related activity analyzed in this Supplemental EIS. 

Recent efforts to open Mississippi State waters for G&G and leasing activities have been challenged in 

court (Davis, 2014).

Alabama 

Alabama has no established schedule of lease sales. The limited number of blocks in State waters has 

resulted in the State not holding regularly scheduled lease sales. The last lease sale was held in 1997. 

BOEM does not expect Alabama to institute a lease sale program in the near future, although there is at 

least a possibility of a lease sale in State waters during the 40-year cumulative activities scenario for OCS 

oil- and gas-related activity following a proposed action (Mobile Area Chamber of Commerce, 2011). 

Florida

BOEM does not expect Florida to institute a lease sale program in the near future, although it is 

possible that a change in policy could lead to leasing on the OCS or in State waters during the 40-year 

cumulative activities scenario for OCS oil- and gas-related activity analyzed in this Supplemental EIS. 

For more information, refer to Chapter 3.3.2 of the 2012-2017 WPA/CPA Multisale EIS. 

Pipeline Infrastructure

A mature pipeline network exists in the GOM to transport oil and gas produced on the OCS to shore 

(Chapter 4.1.1.23.1 for a CPA proposed action). The network carries oil and gas onshore and inland to 

refineries and terminals, and a network of pipelines distributes finished products such as diesel fuel or 

gasoline to and between refineries and processing facilities onshore (Peele et al., 2002, Figure 4.1). 

Expansion of this network is projected to be primarily small-diameter pipelines to increase the 

interconnectivity of the existing network and a few major interstate pipeline expansions. Any new largerdiameter pipelines would likely be constructed to support onshore and offshore LNG terminals. Refer to 

Chapter 3.3.2 of the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 

235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS for information on 
Impact-Producing Factors and Scenario 3-29

pipeline infrastructure activities within the State waters of Texas, Louisiana, Mississippi, and Alabama in 

relation to a CPA proposed action. 

Cumulative Activities Scenario: Over the next 40 years, increased use of OCS sand for Louisiana 

restoration projects is likely. Currently, no Texas restoration projects have been specifically identified. 

The boundary between the OCS and Texas State waters (9 nmi [10 mi; 16 km]) allows that some offshore 

sand is within the jurisdiction of the State; however, the easternmost portion of the shelf in Texas State 

waters is relatively devoid of beach-quality sand deposits. The Texas General Land Office, in 

cooperation with BOEM and the Texas Bureau of Economic Geology, has investigated the potential for 

use of Heald and Sabine Banks as borrow for beach restoration projects, but it has yet to identify specific 

projects. With respect to Louisiana, some uncertainty exists as to the amount of offshore OCS sand that 

will eventually be sought for coastal restoration projects. The Louisiana Coastal Area Ecosystem 

Restoration Plan potentially may use up to 60 million yd3 (46 million m3

) (U.S. Dept. of the Army, COE, 

2009). Recently, there has been an increase in requests from Louisiana for State-funded OCS sand 

resources projects. BOEM anticipates that this growing trend of State-led projects will continue into the 

future as restoration funding is made available directly to the State through the Coastal Impact Assistance 

Program, the Gulf of Mexico RESTORE Act, the Deepwater Horizon NRDA restoration, and the Gulf of 

Mexico Energy Security Act.

3.3.3. Other Major Factors Influencing Offshore Environments

Other influencing factors occur in the offshore areas of the Gulf Coast States while OCS oil- and gasrelated activity takes place at the same time. Some of these factors are (1) dredged material disposal, 

(2) OCS sand borrowing, (3) marine transportation, (4) military activities, (5) artificial reefs and rigs-toreefs development, (6) offshore LNG projects, (7) development of gas hydrates, and (8) renewable energy

and alternative use.

Cumulative impacts to biological, physical, and socioeconomic resources from these types of 

non-OCS oil- and gas-related activities are analyzed in the cumulative impacts analysis sections in

Chapter 4.1.1 of this Supplemental EIS and Chapter 4.2.1 of the 2012-2017 WPA/CPA Multisale EIS. 

3.3.3.1. Dredged Material Disposal

Dredged material is described in 33 CFR part 324 as any material excavated or dredged from 

navigable waters of the United States. Materials from maintenance dredging are primarily disposed of 

offshore on existing dredged-material disposal areas and in ocean dredged-material disposal sites 

(ODMDS). Additional dredged-material disposal areas for maintenance or new-project dredging are 

developed as needed and must be evaluated and permitted by the U.S. Army Corps of Engineers (COE) 

and relevant State agencies prior to construction. ODMDS’s are regulated by USEPA under the Clean 

Water Act and the Marine Protection, Research, and Sanctuaries Act (also called the Ocean Dumping 

Act). 

If funds are available, COE uses dredge materials beneficially for restoring and creating habitat, for 

beach nourishment projects, and for industrial and commercial development (Chapter 3.3.4.3). The 

applicant will need funds to cover the excess cost over the least cost environmentally acceptable 

alternative (the Federal Standard). The material must also be suitable for the particular beneficial use. 

Virtually all ocean dumping that occurs today is maintenance dredging of sediments from the bottom of 

channels and bodies of water in order to maintain adequate channel depth for navigation and berthing. 

There are four authorized open-water disposal areas in Louisiana and Mississippi along stretches of the 

main Gulf Intracoastal Waterway (GIWW) between Louisiana and Mississippi: in Louisiana, Disposal 

Area 66 (1,593 ac; 645 ha); and in Mississippi, Disposal Area 65A (1,962 ac; 794 ha), Disposal Area 65B 

(815 ac; 330 ha), and Disposal Area 65C (176 ac; 71 ha) (U.S. Dept. of the Army, COE, 2008, Table 1). 

Dredged materials from the GIWW are sidecast at these locations. The ODMDS’s utilized by COE are 

located in the cumulative activities area and include those shown in Table 3-30 of the 2012-2017 

WPA/CPA Multisale EIS. Maps on the USEPA website show the locations for the ODMDS’s in 

Louisiana and Texas (USEPA, 2011).

There are two primary Federal environmental statutes governing dredge material disposal. The 

Marine Protection, Research, and Sanctuaries Act (also called the Ocean Dumping Act) governs 

transportation for the purpose of disposal into ocean waters. Section 404 of the Clean Water Act governs 
3-30 Central Planning Area Lease Sale 247 Supplemental EIS

the discharge of dredged or fill material into U.S. coastal and inland waters. The USEPA and COE are 

jointly responsible for the management and monitoring of ocean disposal sites. The responsibilities are 

divided as follows: (1) COE issues permits under the Clean Water Act and the Marine Protection, 

Research, and Sanctuaries Act; (2) USEPA has lead for establishing environmental guidelines/criteria that 

must be met to receive a permit under either statute; (3) permits for ODMDS disposal are subject to 

USEPA review and concurrence; and (4) USEPA is responsible for designating ODMDSs. 

The COE’s Ocean Disposal Database reports the amount of dredged material disposed in ODMDSs 

by district (U.S. Dept. of the Army, COE, 2010, Table 1). Table 3-9 of the CPA 235/241/247 

Supplemental EIS shows the quantities of dredged materials disposed of in ODMDSs between 2005 and 

2010 by the Mobile and New Orleans Districts.

The New Orleans District dredges an average annual 15.4 million yd3

 (11.8 million m3). Current 

figures estimate that approximately 38 percent (or 7.7 million yd3

 [5.9 million m3]) of that average is 

available for the beneficial use of dredge materials program (U.S. Dept. of the Army, COE, 2013). The 

remaining 62 percent of the total material dredged yearly by COE’s New Orleans District is disposed of at 

placement areas regulated under Section 404 of the Clean Water Act, at ODMDSs, or it is stored in 

temporary staging areas located inland (e.g., the Pass a Loutre Hopper Dredge Disposal Site at the head of 

the Mississippi River’s main “birdfoot” distributary channel system).

Cumulative Activities Scenario: BOEM anticipates that, over the next 40 years, the amount of 

dredged material disposed at ODMDSs will fluctuate generally within the trends established by the COE 

district offices. Between 2003 and 2013, the New Orleans District has averaged about 15.4 million yd3

(11.8 million m3

) of material dredged per year disposed at ODMDSs, while the Mobile District is about 

one-quarter of that quantity, or 5.0 million yd3 (3.8 million m3

) (refer to Table 3-9 of the CPA 

235/241/247 Supplemental EIS). Quantities disposed at ODMDSs may decrease as more beneficial uses 

of dredged material onshore are identified and evaluated. For a more complete and detailed discussion of 

dredged material disposal activities, refer to Chapter 3.3.3.1 of the 2012-2017 WPA/CPA Multisale EIS

and CPA 235/241/247 Supplemental EIS. 

3.3.3.2. OCS Sand Borrowing

If OCS sand is desired for coastal restoration or beach nourishment, BOEM uses the following two 

types of lease conveyances: a noncompetitive negotiated agreement that can only be used for obtaining 

sand and gravel for public works projects funded in part or whole by a Federal, State, or local government 

agency; and a competitive lease sale in which any qualified person may submit a bid. BOEM has issued 

47 noncompetitive negotiated agreements but has never held a competitive lease sale for OCS sand and 

gravel resources. BOEM’s Marine Minerals Program continues to focus on identifying sand resources for 

coastal restoration, investigating the environmental implications of using those resources, and processing 

noncompetitive use requests. In May 2015, BOEM issued one new agreement for the Deepwater Horizon

NRDA Whiskey Island Restoration Project in Terrebonne Parish, Louisiana, using sand from Ship Shoal 

Block 88. In March 2014, BOEM issued a noncompetitive agreement for Phase Two of the Caminada 

Headland Restoration Project in Lafourche and Jefferson Parishes, Louisiana, using sand from South 

Pelto Blocks 13 and 14. Construction for Phase Two began in May 2015 with completion anticipated in 

May 2017. 

BOEM has outlined its responsibility as steward of significant sand resources on the OCS in NTL 

2009-G04, which states the following: “If it is determined that significant OCS sediment resources may 

be impacted by a proposed activity, the MMS GOMR may require you to undertake measures deemed 

economically, environmentally, and technically feasible to protect the resources to the maximum extent 

practicable. Measures may include modification of operations and monitoring of pipeline locations after 

installation.” This NTL also provides guidance for the avoidance and protection of significant OCS 

sediment resources essential to coastal restoration initiatives in BOEM’s Gulf of Mexico OCS Region. 

Over the next 40 years, increased use of OCS sand for Louisiana restoration projects is likely. Currently, 

no Texas restoration projects have been specifically identified. For more information on OCS sand 

borrowing, refer to Chapter 3.3.3.2 of the 2012-2017 WPA/CPA Multisale EIS, CPA 235/241/247 

Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS. 
Impact-Producing Factors and Scenario 3-31

3.3.3.3. Marine Transportation

Under current conditions, freight and cruise ship passenger marine transportation within the analyzed 

area should continue to grow at a modest rate or remain relatively unchanged based on historical freight 

traffic statistics under current conditions. In 2013, the Sabine-Neches Waterway had the highest vessel 

capacity, followed by the Port of New Orleans in terms of tonnage handled. The Port of Houston was the 

third largest port in the United States (USDOT, MARAD, 2015). Tankers carrying mostly 

petrochemicals account for about 60 percent of the vessel calls in the Gulf of Mexico. Dry-bulk vessels 

including bulk vessels, bulk containerships, cement carriers, ore carriers, and wood-chip carriers 

accounted for another 17 percent of the vessel calls. The Gulf supports a popular cruise industry. In 

2011, there were 149 cruise ship departures from Galveston, 139 cruise ship departures from New 

Orleans, and 199 cruise ship departures from Tampa (USDOT, MARAD, 2012).

Total port use in the U.S. is increasing as a whole, and total port use within the GOM is also 

increasing. Over the last 10 years, the Gulf of Mexico port calls have represented approximately 

32 percent of total U.S. port calls. Trends for GOM port calls relative to total U.S. port calls show an 

approximate 3 percent average increase of GOM port calls over the last decade, i.e., from 17,673 to 

22,989 (USDOT, MARAD, 2013) (Table 3-10 of the CPA 235/241/247 Supplemental EIS).

Table 3-2 presents the estimated number of vessel trips that would occur as a result of the CPA 

proposed action. Annual OCS oil- and gas-related vessel traffic due to a typical CPA proposed action 

represents a small proportion (<1%) of the total vessel traffic in the GOM (Chapter 3.1.1.8 of this 

Supplemental EIS and Chapter 3.1.1.8.4 of the 2012-2017 WPA/CPA Multisale EIS for a CPA proposed 

action). Annual OCS oil- and gas-related vessel traffic due to cumulative OCS oil- and gas-related 

activity represents between 9 and 12 percent of the total traffic in the GOM.

Cumulative Activities Scenario: It is expected that the usage of GOM ports will continue to increase 

by approximately 3 percent annually over the next 40 years. As such, it is anticipated that port calls by all 

ship types will be bounded annually by a lower limit of current use and an upper limit of approximately 

85,000 vessel port calls. 

3.3.3.4. Military Activities

A standard military warning areas stipulation has been applied to all blocks leased in military areas in 

the GOM since 1977. The air space over the GOM is used by the U.S. Department of Defense (DOD) for 

conducting various military operations. Twelve military warning areas and six Eglin Water Test Areas 

(EWTAs) are located within the Gulf of Mexico (Figure 2-2. These military warning areas and EWTAs 

are multiple-use areas where military operations and oil and gas development have coexisted without 

conflict for many years. Several military stipulations are planned for leases issued within identified 

military areas.

CPA Activities Scenario: Six designated military areas and three EWTAs that are used for military 

operations lie wholly or partially within the CPA (Figure 2-2). The military warning areas within the 

CPA total approximately 13.3 million ac (about 23% of the total acreage of the CPA). The EWTAs 

within the CPA total approximately 7 million ac (about 12% of the total acreage of the CPA). Chapter 

3.3.3.4 of the 2012-2017 WPA/CPA Multisale EIS describes military activities within the OCS.

In addition to the previously noted standard Military Areas Stipulation, the EWTAs will require the 

following special stipulations: 

• Evacuation Stipulation: Lessee is required to evacuate, upon receipt of a directive 

from BOEM’s Regional Director, all personnel from structures on the lease. Lessee 

must also shut-in and secure all wells and other equipment, including pipelines, on 

the lease.

• Coordination Stipulation: Lessee is required to consult with the appropriate military 

command headquarters regarding the location, density, and the planned periods of 

operation of surface structures on the lease, and to maximize exploration while 

minimizing conflicts with DOD activities prior to approval of an exploration plan by 

BOEM’s Regional Director.
3-32 Central Planning Area Lease Sale 247 Supplemental EIS

Cumulative Activities Scenario: BOEM anticipates that, over the next 40 years, the military use areas 

currently designated in the CPA, EPA, and WPA will remain the same and that none of them would be 

released for nonmilitary use. Over 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 the military mission needs.

3.3.3.5. Artificial Reefs and Rigs-to-Reefs Development

A full description of artificial reefs and Rigs-to-Reefs operations is presented in the 2012-2017 

WPA/CPA Multisale EIS for a CPA proposed action. No new significant information was discovered 

that would alter impact conclusions based upon these operations. The following is a summary; for more 

details, refer to Chapter 3.1.1.10 of this Supplemental EIS and Chapter 3.1.1.10 of the 2012-2017 

WPA/CPA Multisale EIS. 

Artificial reefs have been used along the coastline of the U.S. since the early 19th century. Stone 

(1974) documented that the use of obsolete materials to create artificial reefs has provided valuable 

habitat for numerous species of fish in areas devoid of natural hard bottom. Some studies have indicated 

that artificial reefs in marine waters not only attract fish but, in some instances, may also enhance the 

production of fish (Stone et al., 1979; Carr and Hixon, 1997; Dance et al., 2011). All of the five Gulf 

Coast States—Texas, Louisiana, Mississippi, Alabama, and Florida—have established State artificial reef 

programs and plans. These programs are guided by the National Artificial Reef Plan, a requirement of the 

National Fishing Enhancement Act of 1984. The lead agencies responsible for guiding and regulating 

artificial reef development are NOAA and the COE.

Offshore oil and gas platforms have been contributing hard substrate to the GOM since the first 

platform was installed in 1942. However, OCSLA and implementing regulations establish 

decommissioning obligations, including the removal of platforms. The Rigs-to-Reefs Policy provides a 

means by which lessees may request a waiver to the removal requirement. Although BSEE supports and 

encourages the reuse of obsolete oil and gas structures as artificial reefs, lessees must meet specific 

requirements for a departure to be granted. In recent years, approximately 12 percent of the platforms 

decommissioned from the Gulf OCS have been used in authorized artificial reef programs (USDOI, 

BSEE, 2014b). Scientific and public interest in the ecology of offshore structures and the potential 

benefits of contributing substantial quantities of hard substrate to a predominantly soft bottom 

environment may lead to increased emphasis on the creation of artificial reefs through the Rigs-to-Reefs 

Policy. At present, Texas, Louisiana, Alabama, and Mississippi participate in the Rigs-to-Reefs Program. 

WPA, CPA, and EPA Proposed Actions Scenario (Typical Lease Sale): The number of platform 

removals projected for a WPA, CPA, or EPA proposed action is 14-22, 32-61, and 0-1, respectively 

(Table 3-2 of this Supplemental EIS for a CPA proposed action, Table 3-2 of the 2012-2017 WPA/CPA 

Multisale EIS for a WPA proposed action, and Table 3-2 of the EPA 225/226 EIS for an EPA proposed 

action). The number of platforms anticipated to be part of the Rigs-to-Reefs Program as a result of a 

WPA, CPA, or EPA proposed action is approximately 10 percent of the projected removals, or 1-2 in the 

WPA, 3-7 in the CPA, and up to 1 in the EPA.

OCS Program Scenario: Over the course of the 40-year cumulative activities scenario for the OCS 

Program (2012-2051), BOEM projects that a total of 1,279-1,837 platforms will be removed (Table 3-4). 

If approximately 10 percent of these structures are accepted into the Rigs-to-Reefs Program, there may be 

as many as 128-184 additional artificial reefs installed in the WPA, CPA, and EPA.

3.3.3.6. Offshore Liquefied Natural Gas Projects and Deepwater Ports

There are currently no LNG terminals operating on the OCS in the Gulf of Mexico. The following 

provides updates to the status of LNG projects and deepwater ports in the GOM, as provided in Chapter 

3.3.3.6 of the 2012-2017 WPA/CPA Multisale EIS, CPA 235/241/247 Supplemental EIS, and CPA 

241/247 and EPA 226 Supplemental EIS (USDOT, MARAD, 2014).

Florida

Port Dolphin. On March 29, 2007, Port Dolphin Energy LLC filed an application with the U.S. 

Department of Transportation Maritime Administration (MARAD) to construct a deepwater port located 

in Federal waters approximately 28 mi (45 km) offshore of Tampa, Florida. The applicant is a wholly
Impact-Producing Factors and Scenario 3-33

owned subsidiary of Höegh LNG. The proposed port will consist of two Submerged Turret Loading 

(STL) buoys similar to those used in the Northeast Gateway and Neptune projects. On October 26, 2009, 

the MARAD issued a ROD approving, with conditions, the Port Dolphin Energy Deepwater Port License 

application, and on April 19, 2010, the official license was issued. Port Dolphin is currently working with 

the relevant Federal and State of Florida agencies to obtain the required authorizations and permits for 

construction and operation of the facility. Due to market considerations and commercial potential of the 

project, Port Dolphin requested on October 17, 2014, that the Commission extend the deadline until 

December 31, 2018, for constructing and placing into operation the facilities authorized by the 

December 3, 2009, Federal Energy Regulatory Commission (FERC) Certificate (Port Dolphin Energy, 

2014). 

3.3.3.7. Development of Gas Hydrates

Chapter 3.3.3.7 of the 2012-2017 WPA/CPA Multisale EIS and CPA 235/241/247 Supplemental EIS 

describes the development of gas hydrates in detail. BOEM still anticipates that, within 40 years, it is 

likely that the first U.S. domestic production from hydrates may occur in Alaska. Gas obtained from 

onshore hydrates in Alaska will either support local oil and gas field operations or be available for 

commercial sale if and when a gas pipeline is constructed to the lower 48 states. However, Moridis et al. 

(2008) stated that one should not discount the possibility that the first U.S. domestic production of gas 

hydrates could occur in the GOM. Despite the substantially increased complexity and cost of offshore 

operations, there is a mature network of available pipeline capacity and easier access to markets in the 

Gulf of Mexico. 

3.3.3.8. Renewable Energy and Alternative Use

The two primary categories of renewable energy that have the potential for development in the coastal 

and OCS waters of the U.S. are (1) wind turbines and (2) marine hydrokinetic systems. Chapter 3.3.3.8 

of the 2012-2017 WPA/CPA Multisale EIS describes renewable energy and alternative use programs and 

potential action within the OCS, and it is updated in Chapter 3.3.3.8 of the CPA 241/247 and EPA 226 

Supplemental EIS. 

Cumulative Activities Scenario: BOEM expects that, over the next 40 years, a limited number of 

alternative use projects will be proposed in the WPA. It is also likely that these alternative use projects 

will consist of wind energy projects based on the current development of that technology. BOEM’s 

expectation is based on the fact that known projects are being proposed in Texas State waters. Likewise, 

the potential alternative use projects could consist of a combination of integrated existing GOM 

infrastructure with new-built facilities.

3.3.4. Other Major Factors Influencing Coastal Environments

3.3.4.1. Sea-Level Rise and Subsidence

Given the results from the National Assessment of Coastal Vulnerability to Sea Level Rise, BOEM 

anticipates that, over the next 40 years, the northern GOM will likely experience a minimum relative sealevel rise of 55.2 millimeters (2.17 inches) and a maximum relative sea-level rise of 384 millimeters 

(15.1 inches) (Pendleton et al., 2010). Sea-level rise and subsidence together have the potential to affect 

many important areas, including the OCS oil and gas industry, oil and gas infrastructure, waterborne 

commerce, commercial fishery landings, and important habitat for biological resources (State of 

Louisiana, Coastal Protection and Restoration Authority, 2012a). Chapter 3.3.4.1 of the 2012-2017 

WPA/CPA Multisale EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 

Supplemental EIS describe sea-level rise and subsidence in detail. Programmatic aspects of climate 

change relative to the environmental baseline for the Gulf of Mexico OCS Program are discussed in 

Chapter 3.3 of the Five-Year Program EIS. 

3.3.4.2. Mississippi River Hydromodification

Hydromodifying interventions include construction of (1) levees along the river and distributary 

channel systems, (2) upstream dams and flood control structures that impound sediment and meter the 
3-34 Central Planning Area Lease Sale 247 Supplemental EIS

river flow rate, and (3) channelized canals with earthen or armored banks. Once the natural processes that 

act to add sediment to the delta platform to keep it emergent are shut down, subsidence begins to outpace 

deposition of sediment. BOEM anticipates that, over the next 40 years, there might be minor sediment 

additions resulting from new and continuing freshwater diversion projects managed by the COE. Chapter 

3.3.4.2 of the 2012-2017 WPA/CPA Multisale EIS, CPA 235/241/247 Supplemental EIS, and CPA 

241/247 and EPA 226 Supplemental EIS describe Mississippi River hydromodification in detail. 

3.3.4.3. Maintenance Dredging and Federal Channels

The Gulf Intracoastal Waterway is a shallow-draft navigation channel constructed to provide a 

domestic connection between Gulf ports after the discovery of oil in East Texas in the early 1900’s and to 

serve the growing need for the interstate transport of steel and other manufacturing materials. It extends 

approximately 1,400 mi (2,253 km) along the Gulf Coast from St. Marks, south of Tallahassee, in 

northwestern Florida to Brownsville, Texas. The length of the Gulf Intracoastal Waterway along the 

Florida coast is approximately 186 mi (300 km), along Alabama approximately 50 mi (80 km), along 

Mississippi approximately 70 mi (112 km), along Louisiana approximately 990 mi (1,600 km), and from 

the Sabine River through Texas to the Mexican Border 428 mi (690 km) (Good et al., 1995), which does 

not include the length of subsidiary channels included in the COE’s maintenance programs. Maintenance 

dredging is performed by the COE on an as-needed basis along the Gulf Intracoastal Waterway and the 

subsidiary channels that directly or indirectly connect to it or open water. Typically, COE schedules 

surveys every 2 years for each navigation channel under its responsibility in order to maintain channel 

depth to specified standards.

For a more complete and detailed discussion of maintenance dredging and Federal channels, refer to 

Chapter 3.3.4.3 of the 2012-2017 WPA/CPA Multisale EIS and CPA 235/241/247 Supplemental EIS. 

For more information on coastal restoration programs, refer to Chapter 3.3.4.4 of this Supplemental EIS 

and Chapter 3.4.4.4 of the 2012-2017 WPA/CPA Multisale EIS. 

3.3.4.4. Coastal Restoration Programs

Coastal restoration programs are taking place on both the State and Federal levels. Current Federal 

efforts include the Coastal Wetlands Planning Protection and Restoration Act program; the Coastal 

Impact Assistance Program, which was formed in response to the Energy Policy Act of 2005; and the 

Gulf Coast Ecosystem Restoration Council, which was formed in response to the Resources and 

Ecosystems Sustainability, Tourist Opportunities and Revived Economies of the Gulf Coast States Act 

(RESTORE Act). For more information on coastal restoration programs, refer to Chapter 3.4.4.4 of the 

2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 

Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS. 

3.3.5. Natural Events and Processes

Chapter 3.3.5 of the 2012-2017 WPA/CPA Multisale EIS describes in detail natural events and 

processes in the GOM related to a CPA proposed action, including physical oceanography and hurricanes. 

Since 2009, most of the extreme atmospheric events in the GOM have been categorized as tropical storms 

with strong winds, heavy rain, and storm surges causing coastal flooding. However, on August 28, 2012, 

Hurricane Isaac made landfall in southeastern Louisiana as a Category 1 hurricane. While there were no 

reports of moderate or extensive damage to offshore oil or gas infrastructure in the GOM, Hurricane Isaac 

did result in the suspension of small amounts of tarballs and some oil from sediments (Mulabagal et al., 

2013). In addition, Mitra et al. (2009) evaluated the extent to which Hurricanes Katrina and Rita in 2005 

dispersed and resuspended sediments in marshes and in the shallow and deep shelf of the Gulf of Mexico. 

This conforms with predictions in the 2012-2017 WPA/CPA Multisale EIS analyses and is discussed 

more fully in Chapter 4.1.1.2.1 of this Supplemental EIS.

3.3.6. Non-OCS Oil- and Gas-Related Oil Spills

Oil spills related to non-OCS oil- and gas-related activities such as State oil and gas activity or vessel 

collisions (including tankering, barging, or State oil and gas vessels) can result in the contamination of 

offshore or coastal environments. The Oil Pollution Act of 1990 strengthens planning and prevention 
Impact-Producing Factors and Scenario 3-35

activities in waters by (1) providing for the establishment of spill contingency plans for all areas of the 

U.S., (2) mandating the development of response plans for individual tank vessels and certain facilities for 

responding to a worst-case discharge or a substantial threat of such a discharge, and (3) providing 

requirements for spill-removal equipment and periodic inspections. Oil spills associated with the CPA 

proposed action are discussed in Chapter 3.2.1 of this Supplemental EIS and Chapter 3.2.1 of the 2012-

2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental 

EIS, and CPA 241/247 and EPA 226 Supplemental EIS. For more information on the Oil Pollution Act

of 1990 and other response requirements and initiatives regarding oil spills, refer to Chapter 3.2.1.9 of 

this Supplemental EIS and Chapter 3.2.1.9 of the 2012-2017 WPA/CPA Multisale EIS. Spills from 

tankers involve the spillage of crude oil, whereas barge spills involve spills of both crude oil and other 

petroleum products. Anderson et al. (2012) noted that tanker spill rates have continued to have a 

substantial decline since 2000. Most likely, tanker spills have declined due to major regulatory changes 

in the early 1990’s that substantially eliminated the use of single-hull tankers by requiring double hulls or 

their equivalent (Anderson et al., 2012). A majority of spills from tankers occurred in coastal areas 

(37 spills) versus offshore (16 spills) between 1974 and 2008. Barge spill rates for the last 15 years (1994 

through 2008) declined dramatically as compared with the entire time period of available data (1974 

through 2008), especially for crude oil barges and for both spill sizes ≥1,000 bbl and >10,000 bbl 

(Anderson et al., 2012). From 1974 through 2008, 197 petroleum spills ≥1,000 bbl (28 of which were 

crude oil spills) occurred from barges in U.S. coastal, offshore, and inland waters (including U.S. 

territorial waters). Because the data available on barge transport in U.S. waters do not differentiate 

between inland and coastal/offshore transport, inland transport was included. 

CHAPTER 4 

DESCRIPTION OF THE ENVIRONMENT

AND IMPACT ANALYSIS

Description of the Environment and Impact Analysis 4-3 

4. DESCRIPTION OF THE ENVIRONMENT AND IMPACT ANALYSIS

The impacts of 10 WPA and CPA lease sales were analyzed in the “prior 2012-2017 Gulf of Mexico 

EISs”: Gulf of Mexico OCS Oil and Gas Lease Sales: 2012-2017; Western Planning Area Lease Sales 

229, 233, 238, 246, and 248; Central Planning Area Lease Sales 227, 231, 235, 241, and 247, Final 

Environmental Impact Statement (2012-2017 WPA/CPA Multisale EIS) (USDOI, BOEM, 2012b); and 

this analysis was updated in the Gulf of Mexico OCS Oil and Gas Lease Sales: 2013-2014; Western 

Planning Area Lease Sale 233; Central Planning Area Lease Sale 231, Final Supplemental 

Environmental Impact Statement (WPA 233/CPA 231 Supplemental EIS) (USDOI, BOEM, 2013a); 

Central Planning Area Lease Sales 235, 241, and 247, Final Supplemental Environmental Impact 

Statement (CPA 235/241/247 Supplemental EIS) (USDOI, BOEM, 2014a); and Central Planning Area 

Lease Sales 241 and 247 and Eastern Planning Area Lease Sale 226, Final Supplemental Environmental 

Impact Statement (CPA 241/247 and EPA 226 Supplemental EIS) (USDOI, BOEM 2015a). An analysis 

of the routine, accidental, and cumulative impacts of the CPA proposed action on the environmental, 

socioeconomic, and cultural resources of the GOM can be found in Chapter 4.2.1 of the 2012-2017 

WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS, and Chapter 4.1.1 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS; these EISs are hereby 

incorporated by reference.

The purpose of this Supplemental EIS is to determine if there are significant new circumstances or 

information bearing on the CPA proposed action or its impacts, as previously discussed in the prior 2012-

2017 Gulf of Mexico EISs and, if so, to disclose those changes and conclusions. This includes all 

relevant new information available since publication of the prior 2012-2017 Gulf of Mexico EISs. This 

Supplemental EIS analyzes the potential impacts of the CPA proposed action (Chapter 4.1.1) on the

sensitive coastal environments, offshore marine resources, onshore and offshore socioeconomic 

resources, and cultural resources.

4.1. PROPOSED CENTRAL PLANNING AREA LEASE SALE 247

Proposed CPA Lease Sale 247 is tentatively scheduled to be held in March 2017. The proposed CPA 

lease sale area encompasses about 63 million ac of the total CPA area of 66.45 million ac. This area 

begins 3 nmi (3.5 mi; 5.6 km) offshore Louisiana, Mississippi, and Alabama, and extends seaward to the 

limits of the United States’ jurisdiction (often the Exclusive Economic Zone) in water depths up to 

approximately 3,346 m (10,978 ft) (Figure 1-1). As of January 2016, approximately 47.87 million ac of 

the proposed CPA lease sale area are currently unleased. This information is updated monthly and can be 

found on BOEM’s website at http://www.boem.gov/Gulf-of-Mexico-Region-Lease-Map/. The CPA 

proposed action would offer for lease all unleased blocks within the proposed CPA lease sale area for oil 

and gas operations (Figure 2-1), with the following exceptions:

(1) whole and portions of blocks deferred by the Gulf of Mexico Energy Security Act of 

2006; and

(2) blocks that are adjacent to or beyond the United States’ Exclusive Economic Zone in 

the area known as the northern portion of the Eastern Gap. 

The DOI is conservative throughout the NEPA process and includes the total area within the CPA for 

environmental review even though the leasing of portions of the CPA (subareas or blocks) can be deferred 

during a Five-Year Program.

Chapter 4.1.1 presents a brief summary of the baseline data for the physical, biological, and 

socioeconomic resources that would potentially be affected by the CPA proposed action or the 

alternatives. For additional information on the baseline data for the physical, biological, and 

socioeconomic resources that would potentially be affected by the CPA proposed action or the 

alternatives, refer to Chapter 4.2.1 of the 2012-2017 WPA/CPA Multisale EIS and to updated information 

provided in Chapter 4.2.1 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1 of the WPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. 
4-4 Central Planning Area Lease Sale 247 Supplemental EIS

Chapter 4.1.1 also presents analyses of the potential impacts of routine events, accidental events, and 

cumulative activities associated with the CPA proposed action or the alternatives on these resources. 

Baseline data are considered in the assessment of impacts from proposed CPA Lease Sale 247 on these 

resources. In addition, Appendix B (“Catastrophic Spill Event Analysis”) serves as a complement to this 

chapter and provides additional analysis of the potential impacts of a low-probability catastrophic spill, 

which is not part of the CPA proposed action and not likely expected to occur, to the environmental and 

cultural resources and the socioeconomic conditions analyzed below. 

The Deepwater Horizon explosion off the Louisiana coast resulted in the largest oil spill in U.S. 

history. An event such as this has the potential to adversely affect multiple resources over a large area. 

The level of adverse effect depends on many factors, including the sensitivity of the resource as well as 

the sensitivity of the environment in which the resource is located. All effects may not initially be seen 

and some could take years to fully develop. The following analyses of impacts from the Deepwater 

Horizon explosion, oil spill, and response on the physical, biological, and socioeconomic resources are 

based on post-Deepwater Horizon credible scientific information that was publicly available at the time 

this document was prepared. This credible scientific information was applied using accepted 

methodologies, including numerical modeling of data and scientific writing methods to convey the 

information of BOEM’s subject-matter experts’ technical knowledge and experience. However, the 

Trustee Council of the NRDA for the Deepwater Horizon oil spill continues to study, measure, and 

interpret impacts arising out of that spill. Because much of the NRDA information has not yet been made 

available to BOEM or the general public, there are thus instances in which BOEM is faced with 

incomplete or unavailable information that may be relevant to evaluating reasonably foreseeable 

significant adverse impacts on the human environment. 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 there is sufficient basis to proceed with this 

Supplemental EIS while operating on the basis of the most current available data and expertise of 

BOEM’s subject-matter experts.

Chapter 4.1.1 and Appendix B provide a summary of existing credible scientific evidence related to 

this issue and BOEM’s evaluation of potential impacts based upon theoretical approaches or research 

methods generally accepted in the scientific community. Despite the unavailability of complete 

information from the NRDA process, BOEM has determined that it can make an informed decision even 

without this incomplete or unavailable information because BOEM utilizes the best available 

scientifically credible information in its decisionmaking process and because, although BOEM cannot 

speculate as to the results of ongoing NRDA studies, BOEM 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. 

Analytical Approach

The analyses of potential effects to the wide variety of physical, environmental, and socioeconomic 

resources in the vast area of the GOM and adjacent coastal areas are complex. Specialized education, 

experience, and technical knowledge are required, as well as familiarity with the numerous impactproducing factors associated with oil and gas activities and other activities that can cause cumulative 

impacts in the area. Knowledge and practical working experience of major environmental laws and 

regulations such as NEPA, the Clean Water Act, Clean Air Act, Coastal Zone Management Act (CZMA), 

Endangered Species Act (ESA), Marine Mammal Protection Act, the Magnuson-Stevens Fishery 

Conservation and Management Act, and others are also required. 

In order to accomplish this task, BOEM has assembled a multidisciplinary staff with hundreds of 

years of collective experience. The vast majority of this staff has advanced degrees with a high level of 

knowledge related to the particular resources discussed in this chapter. This staff prepares the input to 

BOEM’s lease sale EISs and a variety of subsequent postlease NEPA reviews, and they are also involved 

with ESA, essential fish habitat (EFH), and CZMA consultations. In addition, this same staff is also 

directly involved with the development of studies conducted by BOEM’s Environmental Studies 

Program. The results of these studies feed directly into our NEPA analyses.
Description of the Environment and Impact Analysis 4-5 

For this Supplemental EIS, BOEM developed a set of assumptions and a scenario, and described the 

impact-producing factors that could occur from routine oil and gas activities, as well as accidental events. 

These assumptions, scenario, and factors are summarized in Chapter 3 of this Supplemental EIS and are 

discussed in detail in Chapter 3 of the 2012-2017 WPA/CPA Multisale EIS. On the basis of these 

assumptions, scenario, and factors, BOEM’s multidisciplinary staff applies its knowledge and experience 

to analyze the potential effects that could arise out of proposed CPA Lease Sale 247.

For most resources, the conclusions developed by BOEM’s subject-matter experts regarding the 

potential effects of proposed CPA Lease Sale 247 are necessarily qualitative in nature; however, these 

conclusions are based on the expert opinion and judgment of highly trained subject-matter experts. 

BOEM’s staff approaches this effort in good faith utilizing credible scientific information including, but 

not limited to, information available since the Deepwater Horizon explosion, oil spill, and response, and 

applying this information using accepted methodologies, including numerical modeling of data and 

scientific writing methods to convey the information of the subject-matter experts’ technical knowledge 

and experience. It must also be emphasized that, in arriving at the overall conclusions for certain 

environmental resources (e.g., coastal and marine birds, fisheries, and wetlands), the conclusions are not 

based on impacts to individuals, small groups of animals, or small areas of habitat, but on impacts to the 

resources/populations as a whole. 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. If BOEM’s subject-matter experts determined 

that the incomplete or unavailable information was essential, BOEM made good faith efforts to acquire 

the information. In the event that BOEM was unable to obtain essential information due to either 

impossibility or exorbitant cost, BOEM applied accepted scientific methodologies in place of that 

information. This approach is described in the next subsection on “Incomplete or Unavailable 

Information.” 

Over the years, BOEM has developed a suite of lease stipulations and mitigating measures to 

eliminate or ameliorate potential environmental effects. In many instances, these lease stipulations and 

mitigating measures were developed in coordination with other natural resource agencies such as NMFS 

and FWS.

Throughout its effort to prepare this Supplemental EIS, BOEM has complied with the spirit and intent 

of NEPA, to avoid being arbitrary and capricious in its analyses of potential environmental effects, and to 

use adaptive management to respond to new developments related to the OCS Program. 

Incomplete or Unavailable Information 

In the following analyses of physical, environmental, and socioeconomic resources, BOEM identifies 

situations in which its analysis contains incomplete or unavailable information. The major area where 

BOEM is faced with incomplete or unavailable information is in relation to the Deepwater Horizon

explosion, oil spill, and response. Information related to the explosion, oil spill, and response is still 

being collected, interpreted, and analyzed by a myriad of Federal and State agencies. With respect to 

some of this information, including much of the data related to the NRDA process, those in charge of 

analyzing impacts from the spill have not yet shared their data and findings with BOEM or made this 

information publicly available. Therefore, in situations in which BOEM’s subject-matter experts were 

faced with incomplete or unavailable information, the subject-matter experts for each resource utilized the 

most recent publicly available, scientifically credible information from other sources to support the 

conclusions contained in this Supplemental EIS. This information is identified and summarized in 

Chapter 4.1.1 of this Supplemental EIS and is discussed in detail for each resource in Chapter 4.2.1 of 

the 2012-2017 WPA/CPA Multisale EIS. Updated information is provided in Chapter 4.2.1 of the WPA 

233/CPA 231 Supplemental EIS and Chapter 4.1.1 of the CPA 235/241/247 Supplemental EIS and CPA 

241/247 and EPA 226 Supplemental EIS. In certain circumstances, identified and described in more 

detail in Chapter 4.1.1 of this Supplemental EIS, BOEM’s subject-matter experts were required to utilize 

accepted methodologies to extrapolate conclusions from existing or new information and to make 

reasoned estimates and developed conclusions regarding the current CPA baseline for resource categories 

and expected impacts from the CPA proposed action given any baseline changes. For reasons described 

below, there are no changes to the conclusions presented in the prior 2012-2017 Gulf of Mexico EISs. 

It is important to note that, barring another catastrophic oil spill, which is a low-probability event that 

is not part of the CPA proposed action and not likely expected to occur, the adverse impacts associated 
4-6 Central Planning Area Lease Sale 247 Supplemental EIS

with the proposed CPA lease sale are small, even in light of the Deepwater Horizon explosion, oil spill, 

and response. This is because of lease sale stipulations that are typically applied and because of BOEM’s 

and other Federal and State entities’ mitigating measures. BOEM also imposes site-specific mitigations

that become conditions of plan or permit approval at the postlease stage. Collectively, these measures 

further reduce the likelihood and/or severity of adverse impacts.

For the following resources, as with the prior 2012-2017 Gulf of Mexico EISs, the subject-matter 

experts determined that there is incomplete or unavailable information that is relevant to reasonably 

foreseeable significant adverse impacts; however, it is not essential to a reasoned choice among 

alternatives.

• Natural Resource Damage Assessment (NRDA) Data: In response to the Deepwater 

Horizon explosion, oil spill, and response, a major NRDA is underway to assess 

impacts to all natural resources in the GOM that may have been impacted by the 

resulting spill from the Macondo well, as well as impacts from the spill-response 

operations. The NRDA is mandated by the Oil Pollution Act of 1990. The U.S. 

Department of the Interior is a co-Trustee in the NRDA process, and BOEM is a 

cooperating agency on a Programmatic EIS being prepared as part of the NEPA

analysis for NRDA. However, the NRDA process is being led by the NRDA Trustees, 

which include NOAA and DOI (FWS and the National Park Service) but not BOEM. 

BOEM is listed as an affected party for NRDA purposes. At this time, limited data 

compiled in the NRDA process have been made publicly available. Because limited 

data have been made publicly available, most NRDA datasets are not available for 

BOEM to use in its NEPA analyses. BOEM acknowledges that the ability to obtain 

and use the NRDA data in its NEPA analyses could be relevant to reasonably 

foreseeable significant adverse impacts; however, the NRDA data are not essential to 

a reasoned choice among the alternatives. Impacts identified through the NRDA 

process would likely be the same under any alternative and obtaining these data would 

not help inform the decisionmaker on a reasoned choice among those alternatives. 

This is because, as discussed above, the adverse impacts associated with the proposed 

CPA lease sale are small, even in light of how baseline conditions in the CPA may 

have been changed by the Deepwater Horizon explosion, oil spill, and response. The 

impacts are expected to be small because of BOEM’s lease sale stipulations and 

mitigating measures, site-specific mitigations that become conditions of plan or permit 

approval at the postlease stage, and mitigations required by other State and Federal 

agencies. Even if the NRDA data were essential to a reasoned choice among the 

alternatives, the data are not publicly available and much of the data may not become 

available for many years. The NEPA allows for decisions to be made based on 

available scientifically credible information (e.g., peer-reviewed journals and studies, 

government reports, etc.) applied using accepted methodologies where the incomplete 

information cannot be obtained or the cost of obtaining it is exorbitant. The NRDA 

process is ongoing and there is no timeline on when this information will be released. 

It is not within BOEM’s authority to obtain this information. Cost is not an issue in 

obtaining the information, regardless of whether the cost would be exorbitant or not. 

Instead, the limitations on the NRDA process, including statutory requirements under 

the Oil Pollution Act of 1990, are the determining factors on the availability of this 

information. In light of the fact that the NRDA data may not be available for years, 

BOEM has used accepted scientific methodologies to evaluate each resource, as 

described in this chapter. Since the spill, BOEM’s Gulf of Mexico OCS Region’s 

Environmental Studies Program has continually modified its Studies Plan to reflect the 

Agency’s current information needs for studies that address impacts and recovery 

from the oil spill. The scientific studies conducted by the Environmental Studies 

Program provide some of the data that BOEM relies on in making decisions in this 

Supplemental EIS. BOEM’s proposed studies attempt to avoid duplication of study 

efforts while striving to fill information gaps where NRDA studies may not address 

particular resources and their impacts from the oil spill. 
Description of the Environment and Impact Analysis 4-7 

• Physical Resources in the CPA: Physical resources (i.e., water quality and air quality) 

within the CPA are likely not continuing to be affected to any discernible degree by 

the Deepwater Horizon explosion, oil spill, and response, based on the best available 

information, including recent sampling data. Although unable to speculate as to the 

results of ongoing NRDA studies, BOEM has determined that the incomplete or 

unavailable information is not essential to a reasoned choice among alternatives 

because BOEM utilizes the best available scientifically credible information in its 

decisionmaking process. Much of the information related to the Deepwater Horizon

explosion, oil spill, and response may not be available for some time, regardless of the 

costs necessary to obtain this information, as there are numerous task forces and 

interagency groups involved in the production of the information. It is not expected 

that these data would become publicly available in the near term, and certainly not 

within the timeline contemplated in the NEPA analysis of this Supplemental EIS. 

• Coastal and Offshore Habitats within the CPA: Many coastal and offshore habitats 

(e.g., beaches, wetlands, hard bottoms, and soft bottoms) in the CPA were affected by 

the Deepwater Horizon explosion, oil spill, and response. Recent research has 

documented specific examples of acute and chronic effects to habitat-forming 

organisms and has identified evidence of persistent spill-related contaminants in 

seafloor sediments (refer to Chapters 4.1.1.3, 4.1.1.4, 4.1.1.6, 4.1.1.7, 4.1.1.9, 

4.1.1.10, and 4.1.1.11). Based on the best available information, including recent 

sampling data, overall adverse impacts to CPA coastal and offshore habitat is 

estimated to be small. However, long-term impacts to the affected habitats and 

associated communities are currently unknown and BOEM cannot speculate as to the 

results of ongoing NRDA studies. BOEM has determined that the incomplete or 

unavailable information regarding coastal and offshore habitats is not essential to a 

reasoned choice among alternatives because BOEM utilizes the best available 

scientifically credible information in its decisionmaking process.

• Biological Resources within the CPA: Biological resources (i.e., birds, fish, and 

marine invertebrates) within the CPA may have been affected directly or indirectly by 

the Deepwater Horizon explosion, oil spill, and response, or by residual impacts to 

habitats. Researchers documented some of the effects that likely resulted from 

coating, ingestion, or other contact with polycyclic aromatic hydrocarbons and/or 

spill-related contaminants. The known and likely impacts documented in recent 

studies include physiological and ecological effects to individuals and communities, 

but they have not been extended to population-level impacts. Although various 

biological and environmental factors could mask more extensive impacts and the 

results of ongoing NRDA analyses cannot be obtained, the best available science 

indicates adverse effects were limited (relative to overall populations). Therefore, 

BOEM has determined that the incomplete or unavailable information is not essential 

to a reasoned choice among the alternatives because the adverse impacts from routine 

activities associated with the CPA proposed action are expected to be small.

• Endangered and Threatened Species: BOEM reinitiated consultation with NMFS and 

FWS in light of new information that may become available on these species and in 

light of effects from the Deepwater Horizon explosion, oil spill, and response. 

Pending the completion of the reinitiated ESA section 7 consultation, BOEM has 

prepared an ESA section 7(d) determination (50 CFR § 402.09). Section 7(d) of the 

ESA requires that, after initiation or reinitiation of consultation under section 7(a)(2), 

the Federal agency “shall not make any irreversible or irretrievable commitment of 

resources with respect to the agency action which has the effect of foreclosing the 

formulation or implementation of any reasonable and prudent alternative measures 

which would not violate” section 7(a)(2). BOEM has determined that the CPA 

proposed action during the reinitiated section 7 consultation period is consistent with 

the requirements of ESA section 7(d) because (1) approving and/or conducting the 

proposed CPA lease sale will not foreclose the formulation or implementation of any 
4-8 Central Planning Area Lease Sale 247 Supplemental EIS

Reasonable and Prudent Alternative measures that may be necessary to avoid jeopardy 

(or the likely destruction or adverse modification of critical habitat) and (2) the 

Secretary of the Interior retains the discretion under OCSLA to deny, suspend, or 

rescind plans and permits authorized under OCSLA at any time, as necessary to avoid 

jeopardy. Lease sales alone do not constitute an irreversible and irretrievable 

commitment of resources. In addition, the results of consultation and any additional 

relevant information on endangered and threatened species can be employed during 

postlease activities to ensure that Reasonable and Prudent Alternative measures are 

not foreclosed. BOEM and BSEE have developed an interim coordination program 

with NMFS and FWS for individual consultations on postlease activities requiring 

permits or plan approvals while formal consultation and development of a new 

Biological Opinion is ongoing. 

• Socioeconomic and Cultural Resources: Incomplete or unavailable information 

related to socioeconomic and cultural impacts (i.e., commercial and recreational 

fishing, recreational resources, archaeological resources, land use and coastal 

infrastructure, demographics, economic factors, and environmental justice) may be 

relevant to reasonably foreseeable adverse impacts on these resources. Although 

unable to speculate as to the results of ongoing NRDA studies, BOEM has determined 

that the incomplete or unavailable information would not be essential to a reasoned 

choice among alternatives because BOEM utilizes the best available scientifically 

credible information in its decisionmaking process and cannot speculate as to the 

results of ongoing Deepwater Horizon NRDA studies. 

This chapter has thoroughly examined the existing credible scientific evidence that is relevant to 

evaluating the reasonably foreseeable significant adverse impacts of the proposed CPA lease sales on the 

human environment. The subject-matter experts that prepared this Supplemental EIS conducted a diligent 

search for pertinent new information, and BOEM’s evaluation of such impacts is based upon theoretical 

approaches or research methods generally accepted in the scientific community. All reasonably 

foreseeable impacts were considered, including impacts that could have catastrophic consequences, even 

if their probability of occurrence is low (Appendix B). 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 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). 

4.1.1. Alternative A—The Proposed Action

4.1.1.1. Air Quality

BOEM has reexamined the analysis for air quality presented in the prior 2012-2017 Gulf of Mexico 

EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for air quality presented in those NEPA documents. 

The analysis and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 

247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.1 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.1 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.1 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 
Description of the Environment and Impact Analysis 4-9 

Impacts of Routine Activities and Accidental Events

The following routine activities associated with the CPA proposed action would potentially affect air 

quality: platform construction and emplacement; platform operations; drilling activities; flaring; seismicsurvey and support-vessel operations; pipeline laying and burial operations; evaporation of volatile 

petroleum hydrocarbons during transfers; and fugitive emissions. The impact analysis is based on four 

parameters—emission rates, surface winds, atmospheric stability, and mixing height. Emissions of 

pollutants into the atmosphere from the activities associated with the CPA proposed action are projected 

to have minimal effects on onshore air quality because of the prevailing atmospheric conditions, emission 

rates and mixing heights, and the resulting pollutant concentrations. 

The accidental release of hydrocarbons related to the CPA proposed action would result in the 

emission of air pollutants. The OCS oil- and gas-related accidents could include the release of oil, 

condensate, natural gas, and chemicals used offshore, or pollutants from the burning of these products. 

The air pollutants include criteria NAAQS pollutants, volatile and semi-volatile organic compounds, H2S, 

and methane. If a fire was associated with the accidental event, it would produce a broad array of 

pollutants, including NAAQS-regulated primary pollutants, nitrogen dioxide (NO2), carbon monoxide 

(CO), sulphur dioxide (SO2), volatile organic compounds (VOCs), particulate matter less than or equal to 

10 μm (PM10), and particulate matter less than or equal to 2.5 μm (PM2.5). Response activities to an 

accidental event that could impact air quality include in-situ burning, the use of flares to burn gas and oil, 

and the use of dispersants applied from aircraft. The burning of oil and gas may also produce black 

carbon. Black carbon is the most strongly light-absorbing component of particulate matter and is formed 

by the incomplete combustion of fossil fuels, biofuels, and biomass. Measurements taken during an insitu burning show that a major portion of compounds was consumed in the burn (Fingas et al., 1995), and 

it was found that, during the burn, the pollutants were measured only at background levels; therefore, 

pollutant concentrations would be expected to be within the NAAQS. Accidents involving high 

concentrations of H2S could result in deaths as well as environmental damage. Regulations and NTLs 

include safeguards and protective measures, which are in place to protect workers from H2S releases. 

Other emissions of pollutants into the atmosphere from accidental events as a result of the CPA proposed 

action are not projected to have significant impacts on onshore air quality because of the prevailing 

atmospheric conditions, emissions height, emission rates, and the distance of these emissions from the 

coastline.

Cumulative Impacts 

The cumulative analysis considers OCS oil- and gas-related and non-OCS oil- and gas-related 

activities that could occur and adversely affect onshore air quality from OCS oil- and gas-related sources 

during the 40-year analysis period. The OCS oil- and gas-related activities that could impact air quality 

include the following: platform construction and emplacement; platform operations; drilling activities; 

flaring; seismic-survey and support-vessel operations; pipeline laying and burial operations; evaporation 

of volatile petroleum hydrocarbons during transfers; fugitive emissions; the release of oil, condensate, 

natural gas, and chemicals used offshore, or pollutants from the burning of these products; a lowprobability catastrophic spill, which is not part of the CPA proposed action and not likely expected to 

occur (refer to Appendix B for more details); and fires. Emissions of pollutants into the atmosphere from 

activities associated with the OCS Program are not projected to have significant effects on onshore air 

quality because of the prevailing atmospheric conditions, emission rates and heights, and the resulting 

pollutant concentrations, which result in dilution of the emissions offshore before they reach the 

shoreline. In the CPA, the impacts of the OCS oil- and gas-related emissions on the onshore air quality 

are annual NO2 (0.4μ/m3

) and 24-hour PM2.5 (0.3μ/m3) in the Class I area, which exceed the USEPA’s 

Significant Impact Levels (SILs) for annual NO2 (0.1μ/m3

) and 24-hour PM2.5 (0.07μ/m3) in the Class I 

area. However, onshore impacts on air quality from emissions from OCS oil- and gas-related activities 

are estimated to be within the Prevention of Significant Deterioration (PSD) Class II allowable 

increments. The background concentration and impact concentration are below the NAAQS. The only 

potential exception is for ozone, where there may be some minimal contribution to ozone at the shoreline. 

Non-OCS oil- and gas-related activity includes both marine and onshore industries and activities that 

are unrelated to oil and gas exploration and production. The non-OCS oil- and gas-related activities in the 

cumulative scenario that could potentially impact onshore air quality include the following: State oil and 
4-10 Central Planning Area Lease Sale 247 Supplemental EIS

gas programs; other major offshore but non-OCS oil- and gas-related factors influencing offshore 

environments (such as sand borrowing and transportation); onshore non-OCS oil- and gas-related 

activities such as emissions from industry (including major stationary sources, e.g., power plants, 

petroleum refineries and chemical plants) and mobile sources (cars/trucks) related to human activities; 

onshore non-OCS oil- and gas-related sources unrelated to human activities such as forest fires; accidental 

releases from an oil spill; accidental releases of hydrogen sulfide; and natural events (e.g., hurricanes). 

The non-OCS oil- and gas-related activity on the water that would most likely contribute to cumulative 

impacts to air quality would be the marine shipping or transportation industry. Industrial activity in the 

industrial areas of Louisiana, Mississippi, and Alabama and emissions from cars in areas with high 

populations are the onshore sources that would contribute to the cumulative impact to air quality. These 

non-OCS oil- and gas-related activities generate greater amounts of emission sources than OCS oil- and 

gas-related activities. Human populations reside near these same industries because they offer 

employment, and therefore humans encounter more air contaminants as a result of non-OCS oil- and gasrelated activities than they do from the OCS Program. These non-OCS oil- and gas-related sources would 

represent the majority of the cumulative emissions that are present at onshore locations.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of State and Federal databases, including updates to regulations, was conducted to determine 

the availability of recent information. The search revealed new information on the impacts of black 

carbon to air quality since publication of the prior 2012-2017 Gulf of Mexico EISs. This information is 

pertinent to this Supplemental EIS because it details new information on non-OCS oil- and gas-related 

impacts to the environment. 

Black carbon is emitted directly into the atmosphere in the form of fine particulates, is the most 

strongly light-absorbing component of particulate matter, and is formed by the incomplete combustion of 

fossil fuels, biofuels, and biomass. It is linked to climate impacts, particularly in the Arctic, and visibility 

impacts. The total cumulative PM2.5 from OCS sources is in the range between 4,714 and 

7,687 tons/year. In 2005, the United States is estimated to have emitted about 0.64 million tons of black 

carbon (USEPA, 2015). According to the USEPA, 12 percent of the total amount of PM2.5 is converted to 

black carbon. It is assumed that all PM10 is converted to PM2.5; therefore, the total amount of PM2.5

emitted from OCS sources is between 569 and 926 tons/year. The contribution of black carbon from 

OCS sources is from about 0.09 to 0.15 percent of that of the United States. It is assumed that all PM10 is 

converted to PM2.5; therefore, the estimated total amount of black carbon from OCS sources is overly 

conservative. A surface oil burn was conducted in the Deepwater Horizon oil spill, in which it was 

estimated that approximately 10 kilograms (kg) (22 pound [lb]) of black carbon was released into the 

atmosphere in the Gulf of Mexico during a period of the 9-week spill (Perring et al., 2011; refer to 

Appendix B for more detail). 

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. However, as discussed in this Supplemental EIS and in Chapter 

4.2.1.1 of the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS, and 

Chapter 4.1.1.1 of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental 

EIS, BOEM has identified unavailable information regarding air quality impacts related to the Deepwater 

Horizon explosion, oil spill, and response in the CPA. This information cannot be obtained because the 

means to obtain it are not known. This unavailable information may be relevant to adverse effects 

because air emissions could have reached land or dispersed throughout the WPA/CPA before the oil-spill 

response was activated. BOEM used relevant analysis such as air emissions measurements taken by 

Federal agencies to determine air impacts. For example, a large number of air emissions measurements 

were obtained and released to the public by USEPA, the National Oceanic and Atmospheric 

Administration, and other agencies, indicating that air emissions impacts tended to be minor and below 

USEPA’s health-based standards. And, since there are no continuing sources of air pollution related to 
Description of the Environment and Impact Analysis 4-11

the Deepwater Horizon explosion, oil spill, and response, BOEM would not expect any additional 

measurements or information to alter the conclusions from currently existing data. 

In addition, as noted in Appendix A of the CPA 235/241/247 Supplemental EIS, there are a number 

of competing methods and available models for estimating and tracking potential air emissions and 

impacts. Each of these methods and models has inherent limitations, particularly with regard to the 

offshore environment in which the CPA proposed action would take place. BOEM’s Offshore and 

Coastal Dispersion Model, which was used for this environmental impact assessment (Appendix A of the 

CPA 235/241/247 Supplemental EIS), has limitations such that it is a short-range dispersion model and it 

does not involve the reactive chemistry. In acknowledgement of these limitations, BOEM’s subjectmatter experts, using their best professional judgment and experience, have developed conservative 

assumptions and modeling parameters so as to ensure that the impact conclusions herein are reasonable 

and not underestimated (refer to Appendix A of the CPA 235/241/247 Supplemental EIS for the modeling 

analysis). The modeling that was conducted was overly conservative. All of the emissions during 1 year 

for the entire CPA, which would actually be dispersed throughout the CPA, were modeled as if they 

originated in a single block, i.e., Mississippi Canyon Block 856. This block was selected because it 

represented a location where the water is deep enough that a dynamically positioned drillship would be 

used and where hydrocarbons are probably present. Although there are limitations in air quality 

modeling, the evidence currently available and that was used to develop conservative assumptions, 

supports past analyses and does not indicate severe adverse impacts to air quality.

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing the relevant analysis and formulating the conclusions presented here. Although there is 

incomplete or unavailable information, the evidence currently available supports past analyses and does 

not indicate reasonably foreseeable significant adverse impacts. Therefore, BOEM has determined that 

this information is not essential to a reasoned choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for air quality presented in the prior 2012-2017 Gulf of Mexico 

EISs based on the additional information presented above. No new significant information was 

discovered that would alter the impact conclusion for air quality presented in those NEPA documents 

because of the available scientifically credible evidence in this analysis and based upon accepted 

scientific methods and approaches. Emissions of pollutants into the atmosphere from the routine 

activities and accidental events associated with the CPA proposed action are projected to have minimal 

impacts to onshore air quality, and emissions of pollutants into the atmosphere from activities associated 

with the OCS Program are also not projected to have significant effects on onshore air quality. The nonOCS oil- and gas-related emission sources of intercontinental origin and the hydraulic fracturing of 

reservoirs may have the potential to impact onshore air quality and human health. However, the new 

information does not alter previous impact conclusions for air quality. The analysis and potential impacts 

discussed in those NEPA documents still apply for proposed CPA Lease Sale 247. 

4.1.1.2. Water Quality

4.1.1.2.1. Coastal Waters

BOEM has reexamined the analysis for coastal water quality presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for coastal water quality presented in the prior 2012-

2017 Gulf of Mexico EISs. The analysis and potential impacts discussed in those documents still apply 

for proposed CPA Lease Sale 247. 

Coastal waters within the CPA, as defined by BOEM, include all the bays and estuaries from the 

Louisiana/Texas State border to the Alabama/Florida State border. A detailed description of the affected 

environment and the full analyses of the potential impacts of routine activities, accidental events, and 

cumulative impacts associated with the CPA proposed action are presented in Chapter 4.2.1.2.1 of the 

2012-2017 WPA/CPA Multisale EIS. Updated information is provided in Chapter 4.2.1.2.1 of the WPA 

233/CPA 231 Supplemental EIS and Chapter 4.1.1.2.1 of the CPA 235/241/247 Supplemental EIS and 

CPA 241/247 and EPA 226 Supplemental EIS. The following information is a summary of the resource 
4-12 Central Planning Area Lease Sale 247 Supplemental EIS

description and impact analysis incorporated from those NEPA documents. Any new information that 

has become available since those documents were published is presented below.

Impacts of Routine Activities and Accidental Events

The routine activities associated with the CPA proposed action that would impact coastal water 

quality include the following:

• discharges during drilling of exploration and development wells; 

• structure installation and removal; 

• discharges during production; 

• installation of pipelines; 

• workovers of wells,

• maintenance dredging of existing navigational canals;

• service-vessel discharges; and

• nonpoint-source runoff from platforms and OCS Program-related vessels.

These routine activities and associated impact-producing factors are discussed in detail in the 

2012-2017 WPA/CPA Multisale EIS. The primary impacting sources to water quality in coastal waters 

from oil and gas exploration and production activities are point-source and storm-water discharges from 

support facilities, vessel discharges, and nonpoint-source runoff. These activities are not only highly 

regulated but also localized and temporary in nature. The impacts to coastal water quality from routine 

activities associated with the CPA proposed action should be minimal because of the distance to shore of 

most routine activities, USEPA and USCG regulations that restrict discharges, and few, if any, new 

pipeline landfalls or onshore facilities that would be constructed.

Accidental events resulting from the CPA proposed action, including oil spills, have the potential to 

alter and degrade coastal waters through the increase of petroleum hydrocarbons and their various 

transformation/degradation products in the water.

Accidental events associated with the CPA proposed action that could impact coastal water quality

include spills of oil and refined hydrocarbons, releases of natural gas, spills of chemicals or drilling fluids, 

loss of well control, pipeline failures, collisions, or other malfunctions that would result in such spills. In 

the case of an accidental event, it is likely that response efforts would reduce the amount of oil. Although 

response efforts may decrease the amount of oil in the environment, the response efforts may also impact 

the environment. Increased vessel traffic, hydromodification (e.g., dredging, berm building, boom 

deployment, etc.), and the addition of dispersants and methanol to the marine environment in an effort to 

contain, mitigate, or clean up the oil may also tax the environment. Chapter 3.2.1.9 provides further 

discussion of oil-spill response considerations. A major hurricane can affect OCS oil- and gas-related 

activities and result in a greater number of coastal oil and chemical spill events with increased spill 

volume and oil-spill response times.

In addition to response efforts, natural processes can physically, chemically, and biologically degrade 

oil over time. Offshore oil spills generally have more time for these natural degradation processes to 

occur before impacting the coastline, whereas spills that originate close to shore often impact beaches and 

marshes with no prior degradation. Also, spills in shallow water are more susceptible to incorporate sand 

and gravel in the oil, making it heavier and more likely to sink to the seafloor. Chemicals used in the oil 

and gas industry are not a significant risk in the event of a spill because they are either nontoxic, are used 

in minor quantities, or are only used on a noncontinuous basis. Spills from collisions are not expected to 

be significant because collisions occur infrequently and usually do not cause oil spills >1,000 bbl. 

Cumulative Impacts 

Coastal waters are vulnerable to impacts from OCS oil- and gas-related activities including erosion 

and runoff, sediment disturbance and turbidity, vessel discharges, and accidental releases of oil, gas, or 
Description of the Environment and Impact Analysis 4-13

chemicals. Increased turbidity and discharge from the CPA proposed action would be temporary in 

nature and minimized by regulations and mitigation. Since a catastrophic OCS Program-related accident 

would be rare and not expected to occur in coastal waters, the impact of accidental spills is expected to be 

small. A low-probability catastrophic spill, which is not part of the CPA proposed action and not likely 

expected to occur, is discussed in Appendix B. 

Coastal waters are vulnerable to impacts from non-OCS oil- and gas-related activities or activities not 

related to the CPA proposed action or the OCS Program, including State oil and gas activities, alternative 

energy activities, alternate use programs for platforms (e.g., aquaculture), sand borrowing, the activities 

of other Federal agencies (including the military), natural events or processes, and activities related to the 

direct or indirect use of land and waterways by the human population. These activities may result in 

erosion and runoff, sediment disturbance and turbidity, vessel discharges, and accidental releases of oil, 

gas, or chemicals.

The impacts resulting from the CPA proposed action are a small addition to the cumulative impacts

on the coastal waters of the Gulf of Mexico because non-OCS oil- and gas-related activities, including 

vessel traffic, erosion, and nonpoint source runoff, are cumulatively responsible for a majority of coastal 

water impacts. The incremental contribution of the routine activities and accidental events associated 

with the CPA proposed action to the cumulative impacts on coastal water quality is not expected to be 

significant for the reasons identified above.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

Various Internet sources were examined and literature searches conducted in order to assess the 

availability of new information regarding the water quality and sediment quality in coastal waters that 

may be pertinent to the CPA proposed action. The searches included, but were not limited to, Google, 

Google Scholar, and several USEPA websites. New information was found on the affected environment 

in relation to the Louisiana-Texas hypoxic zone. 

As discussed in Chapter 4.2.1.2.1.4 of the 2012-2017 WPA/CPA Multisale EIS, nutrients carried in 

waters of the Louisiana and Texas rivers contribute to seasonal formation of a hypoxic zone on the 

Louisiana and Texas shelf. The Louisiana Universities Marine Consortium (LUMCON) generally 

predicts the seasonal maximum size of the Louisiana-Texas hypoxic zone based on nitrogen loading in 

the Mississippi River (as measured in May of each year), and the actual size reported is based on cruise 

data collected by LUMCON in July of each year. Recent estimates of the area of low oxygen by NOAA 

(USDOC, NOAA, 2015b) as of August 3, 2015, measured 6,474 square miles (mi2

) (16,760 square 

kilometers [km2

]) (Figure 4-1), an increase from the size measured in 2014 (5,052 mi2; 13,085 km2) and 

larger than the estimated size (5,838 mi2

; 15,120 km2) forecast by Turner and Rabalais (2015) in June 

2015. The Louisiana-Texas hypoxic zone is unrelated to OCS oil- and gas-related activities, but it is 

discussed here as a potential cumulative effect.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplemental EIS and in Chapter 4.2.1.2.1 of 

the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.2.1 

of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS, BOEM 

has identified incomplete or unavailable information that may be relevant to reasonably foreseeable 

impacts on coastal water quality. Much of this information relates to the Deepwater Horizon explosion, 

oil spill, and response and is continuing to be collected and developed through the NRDA process. 

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing this analysis and formulating the conclusions presented here. Given the available data on 

coastal sediments and water quality that have been released and evaluated, as described above and in 

Chapter 4.2.1.2.1 of the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS, 

and as noted in Chapter 4.1.1.2.1 of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 
4-14 Central Planning Area Lease Sale 247 Supplemental EIS

226 Supplemental EIS, BOEM believes that this incomplete or unavailable information is not essential to 

a reasoned choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for coastal waters presented in the prior 2012-2017 WPA/CPA 

Multisale EIS based on the additional information presented above. No new significant information was 

discovered that would alter the impact conclusion for coastal waters presented in those NEPA documents 

because of the available scientifically credible evidence in this analysis and based upon accepted 

scientific methods and approaches. The analysis and potential impacts discussed in those documents still 

apply for proposed CPA Lease Sale 247. 

4.1.1.2.2. Offshore Waters

Offshore waters within the CPA, as defined by BOEM, include Louisiana, Mississippi, and Alabama 

offshore waters and Federal OCS waters, which includes everything outside any barrier islands to the 

Exclusive Economic Zone. 

BOEM has reexamined the analysis for offshore water quality presented in the prior 2012-2017 Gulf 

of Mexico EISs based on the additional information presented below. No new significant information 

was discovered that would alter the impact conclusion for offshore water quality presented in the prior 

2012-2017 Gulf of Mexico EISs. The analysis and potential impacts discussed in those documents still 

apply for proposed CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.2.2 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.2.2 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.2.2 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

The routine activities associated with the CPA proposed action that would impact offshore water 

quality include the following:

• discharges during drilling of exploration and development wells; 

• structure installation and removal; 

• discharges during production; 

• installation of pipelines; 

• workovers of wells; 

• maintenance dredging of existing navigational canals;

• service-vessel discharges; and

• nonpoint-source runoff from platforms and OCS Program-related vessels.

These routine activities and associated impact-producing factors are discussed in detail in the 

2012-2017 WPA/CPA Multisale EIS. During exploratory activities, the primary impacting sources to 

offshore water quality are discharges of drilling fluids and cuttings. During platform installation and 

removal activities, the primary impacting sources to water quality are sediment disturbance and 

temporarily increased turbidity. Impacting discharges during production activities are produced water 

and supply-vessel discharges. Regulations are in place to limit the toxicity of the discharge components, 

the levels of incidental contaminants in these discharges, and, in some cases, the discharge rates and 
Description of the Environment and Impact Analysis 4-15

discharge locations. Pipeline installation can also affect water quality by sediment disturbance and 

increased turbidity. Service-vessel discharges might include water with an oil concentration of

approximately 15 ppm as established by USEPA regulatory standards. Any disturbance of the seafloor 

would increase turbidity in the surrounding water, but the increased turbidity should be temporary and 

restricted to the area near the disturbance. There are multiple Federal regulations and permit requirements 

that would decrease the magnitude of these activities. Impacts to offshore waters from routine activities 

associated with the CPA proposed action should be minimal as long as regulatory requirements are 

followed. 

Accidental events associated with the CPA proposed action that could impact offshore water quality

include spills of oil and refined hydrocarbons, releases of natural gas and condensate, spills of chemicals 

or drilling fluids, loss of well control, pipeline failures, collisions, or other malfunctions that would result 

in such spills. Spills from collisions are not expected to be significant. Overall, since major losses of 

well control are rare events, the potential impacts to offshore water quality are not expected to be 

significant except in the rare case of a catastrophic event. Although response efforts may decrease the 

amount of oil in the environment, the response efforts may also impact the environment through, for 

example, increased vessel traffic and the application of dispersants. Natural degradation processes will 

also decrease the amount of spilled oil over time. Chemicals used in the oil and gas industry are not a 

significant risk for a spill because they are either nontoxic, are used in minor quantities, or are only used 

on a noncontinuous basis. 

Cumulative Impacts 

Offshore waters are vulnerable to impacts from cumulative OCS oil- and gas-related activities 

including erosion and runoff, sediment disturbance and turbidity, vessel discharges, discharges from 

exploration and production activities, and accidental releases of oil, gas, or chemicals. Routine activities 

that increase turbidity and discharges are temporary in nature and are regulated; therefore, these activities 

would not have a lasting adverse impact on water quality. In the case of a low-probability catastrophic

event, degradation processes in both surface and subsurface waters would decrease the amount of spilled 

oil over time through natural processes that can physically, chemically, and biologically degrade oil 

(NRC, 2003). 

Offshore waters are also vulnerable to impacts from activities not related to the CPA proposed action 

or the OCS Program, including State oil and gas activities, alternative uses of platforms (e.g., 

aquaculture), sand borrowing, renewable energy activities, the activities of other Federal agencies 

(including the military), natural events or processes, and activities related to the direct or indirect use of 

land and waterways by the human population(e.g., urbanization, agricultural practices, coastal industry, 

and municipal wastes). These activities may result in erosion and runoff, sediment disturbance and 

turbidity, vessel discharges, natural releases of oil and gas (e.g., seeps), and accidental releases of oil, gas, 

or chemicals. Although some of these impacts are likely to affect coastal areas to a greater degree than 

offshore waters, coastal pollutants that are transported away from shore would also affect offshore 

environments. 

The impacts resulting from the CPA proposed action are a small addition to the cumulative impacts

on the offshore waters of the Gulf, when compared with inputs from natural hydrocarbon inputs (seeps), 

coastal factors (such as erosion and runoff), and other non-OCS oil- and gas-related industrial discharges. 

The incremental contribution of the routine activities and accidental discharges associated with the CPA 

proposed action to the cumulative impacts on offshore water quality is not expected to be significant. 

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

Various Internet sources were examined and literature searches conducted in order to assess the 

availability of new information regarding the water quality and sediment quality in offshore waters that 

may be pertinent to the CPA proposed action. The searches included, but were not limited to, Google, 

Google Scholar, and several USEPA websites. New information was found on the affected environment 

in relation to the Louisiana-Texas hypoxic zone and historic non-OCS oil- and gas-related activities that 

constitute a potential cumulative impact on the offshore environment. 
4-16 Central Planning Area Lease Sale 247 Supplemental EIS

As discussed in Chapter 4.2.1.2.1.4 of the 2012-2017 WPA/CPA Multisale EIS, nutrients carried in 

waters of the Louisiana and Texas rivers contribute to seasonal formation of a hypoxic zone on the 

Louisiana and Texas shelf. The LUMCON generally predicts the seasonal maximum size of the 

Louisiana-Texas hypoxic zone based on nitrogen loading in the Mississippi River (as measured in May of 

each year), and the actual size reported is based on cruise data collected by LUMCON in July of each 

year. Recent estimates of the area of low oxygen by NOAA (USDOC, NOAA, 2015b) as of August 3, 

2015, measured 6,474 mi2 (16,760 km2

) (Figure 4-1), an increase from the size measured in 2014 

(5,052 mi2

; 13,085 km2) and larger than the estimated size (5,838 mi2; 15,120 km2) forecast by Turner and 

Rabalais (2015) in June 2015. The Louisiana-Texas hypoxic zone is unrelated to OCS oil-and gas-related 

activities, but it is discussed here as a potential cumulative effect.

Between 1940 and 1970, certain offshore locations of the United States were used for the disposal of 

various industrial wastes and low-level radioactive wastes; these activities were large, unrecorded, and 

unregulated (USDOC, NOAA, 2015c).

The Marine Protection, Research, and Sanctuaries Act of 1972 (also known as the Ocean Dumping 

Act) was promulgated to regulate ocean dumping and set aside certain areas as national marine 

sanctuaries. Section 101 (33 U.S.C. § 1411) of the Act prohibited ocean dumping, except as authorized 

by permit issued by the USEPA pursuant to Section 102 (33 U.S.C. § 1412). 

In 1973, the USEPA permitted, through Section 102 (33 U.S.C. § 1412), two interim chemical 

disposal sites in the Gulf of Mexico, the charting of which has been maintained by NOAA. Disposal 

Site A, located within the WPA, is situated on the upper part of the Texas-Louisiana continental shelf, 

approximately 125 mi (201 km) southwest of Galveston, Texas. Disposal Site B is located in the CPA off 

the western side of the Mississippi Delta, approximately 60 mi (7 km) south of the mouth of the 

Mississippi River.

BOEM recently became aware of the report, Assessing Potential Ocean Pollutants, which was 

published by the National Academy of Sciences (National Research Council, 1975). This report provided 

a new understanding of the disposal site conditions.

At Site A, uncontained wastes were discharged through a submerged pipe into the turbulent wake of a 

barge. At Site B, waste materials were placed in barrels before discharge. Chemical wastes discharged at 

these sites reportedly had various concentrations of chlorinated hydrocarbons, calcium and sodium 

metals, formaldehyde, cyanide, and other metals (i.e., antimony, mercury, arsenic, zinc, manganese, and 

iron). Seven permits issued by the USEPA in 1973 allowed for the disposal of 84,500 tons of 

uncontained waste at Site A and 208,500 waste barrels at Site B, of which approximately 55,000 bbl 

contained chlorinated hydrocarbons. Chlorinated hydrocarbons were used during the Vietnam War to 

produce pesticides and defoliants (e.g., Agent Orange). 

Site B is discussed in the Information to Lessees and Operators (ITL), “Central Planning Area, Oil 

and Gas Lease Sale 213, Section (t), Commercial Waste Disposal Areas” (February 12, 2010). In the 

ITL, lessees are advised that the blocks associated with the disposal site and the adjacent blocks 

associated with the disposal site that were included in CPA Lease Sale 213 should be considered 

potentially hazardous. Drilling and platform/pipeline placement may require precautions such as 

avoidance upon identification and any other appropriate precautions. No such ITL currently exists for 

Site A.

These chemical waste disposal sites are pertinent to this impact analysis because they constitute a 

potential cumulative effect on offshore water and sediment quality, and they may expose benthic 

organisms to contaminants. Some of the constituents listed in the National Academy of Sciences’ report 

are carcinogenic, and others may bioaccumulate in marine ecosystems. To date, the barrels dumped at 

Site B in 1973 have been under water for 42 years and may have started to release their contents. As 

such, the potential impacts from Sites A and B must be considered in marine environmental assessments 

of the Gulf of Mexico. 

This new information indicates that some of the wastes disposed of on the OCS may have a greater 

environmental impact than offshore OCS oil- and gas-related activity. Chlorinated hydrocarbons are 

more dense than seawater and may sink into sediments if released from the waste barrels. These 

compounds may also dissolve in water and will form a persistent, localized contaminant plume in the 

water column as long as the source remains. In contrast, petroleum hydrocarbon compounds originating 

from OCS oil- and gas- related activities are considered degradable and do not persist in the water column 

after the source is removed.
Description of the Environment and Impact Analysis 4-17

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplemental EIS and in Chapter 4.2.1.2.2 of 

the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.2.2 

of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS, BOEM 

has identified incomplete or unavailable information that may be relevant to reasonably foreseeable 

impacts on offshore water quality. Much of this information relates to the Deepwater Horizon explosion, 

oil spill, and response and is continuing to be collected and developed through the NRDA process. 

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing this analysis and formulating the conclusions. Given the available data on offshore sediments 

and water quality that have been released and evaluated most recently in Chapter 4.1.1.2.2 of the CPA 

241/247 and EPA 226 Supplemental EIS, as well as in Chapter 4.2.1.2.2 of the 2012-2017 WPA/CPA 

Multisale EIS and WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.2.2 of the CPA 235/241/247 

Supplemental EIS, BOEM believes that this incomplete or unavailable information is not essential to a 

reasoned choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for offshore waters presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented above. No new significant information was 

discovered that would alter the impact conclusion for offshore waters presented those NEPA documents 

because of the available scientifically credible evidence in this analysis and based upon accepted 

scientific methods and approaches. The analysis and potential impacts detailed and updated in those 

documents still apply for proposed CPA Lease Sale 247. 

4.1.1.3. Coastal Barrier Beaches and Associated Dunes

BOEM has reexamined the analysis for coastal barrier beaches and associated dunes presented in the 

prior 2012-2017 Gulf of Mexico EISs based on the additional information presented below. No new 

significant information was discovered that would alter the impact conclusion for coastal barrier beaches 

and associated dunes presented in those NEPA documents. The analysis and potential impacts discussed 

in those documents still apply for proposed CPA Lease Sale 247.

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.3 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.3 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.3 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. Additional 

information about the Gulf Islands National Seashore is presented in Chapter 4.1.1.21 of this 

Supplemental EIS. The following information is a summary of the resource description and impact 

analysis incorporated from those NEPA documents. Any new information that has become available 

since those documents were published is presented below.

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors of the CPA proposed action on coastal barrier beaches

and associated dunes include pipeline emplacements, use of navigation channels by vessel traffic, 

dredging, and the use and construction of support infrastructure. Effects to coastal barrier beaches and 

associated dunes from pipeline emplacements, navigation channel use and dredging, and construction or 

continued use of infrastructure in support of the CPA proposed action are expected to be restricted to 

temporary and localized disturbances. The expected 0-1 pipeline landfalls projected in support of the

CPA proposed action are not expected to cause significant impacts to barrier beaches because of the use 

of nonintrusive installation methods and other requirements imposed through Federal and State regulatory 

programs and permitting processes. Impacts could be reduced or eliminated through modern techniques 

such as horizontal, directional (trenchless) drilling to avoid damages to these sensitive wetland habitats. 

Any new processing facilities would not be expected to be constructed on barrier beaches. The CPA 
4-18 Central Planning Area Lease Sale 247 Supplemental EIS

proposed action may contribute to the continued use of gas processing facilities that already exist. 

Existing pipelines, in particular those that are parallel and landward of beaches and that had been placed 

on barrier islands using older techniques that left canals or shore protection structures, have caused and 

could continue to cause barrier beaches to narrow and breach. Pipelines associated with CPA 

development proposing to cross the Gulf Islands National Seashore must be approved by the Secretary of 

the Interior and are subject to appropriate regulations for the protection of the natural and recreational 

values for which the Gulf Islands National Seashore was established (16 U.S.C. § 459(h)(3)).

Maintenance dredging of barrier inlets and bar channels is expected to occur, which, when combined 

with channel jetties, generally causes impacts on adjacent barrier beaches downdrift of the channel by 

removing sediment from the system. Dredging activities in these channels are permitted, regulated, and 

coordinated by the COE with the appropriate State and Federal resource agencies. Impacts from these 

operations are reduced by requirements for the beneficial use of the dredged material for wetland and 

beach construction and restoration. Permit requirements further mitigate dredged material placement in 

approved disposal areas by requiring the dredged material to be placed in such a manner that it neither 

disrupts hydrology nor changes elevation in the surrounding marsh. Because these impacts occur whether 

the CPA proposed action is implemented or not, the CPA proposed action would account for a small 

percentage of these impacts.

Routine activities associated with the CPA proposed action are not expected to adversely alter barrier 

beach configurations much beyond existing, ongoing impacts in localized areas downdrift of artificially 

jettied and maintained channels. Strategic placement of dredged material from channel maintenance, 

channel deepening, and related actions can mitigate adverse impacts upon those localized areas.

Accidental disturbances resulting from the CPA proposed action, including oil spills, have the 

potential to impact coastal barrier beaches and associated dunes of the CPA. The main accidental impactproducing factors that would affect coastal barrier beaches and associated dunes are oil spills and cleanup 

activities.

The potential impacts from oil spills to barrier islands seaward of the barrier-dune system are 

discussed below, while the potential impacts from spills that occur landward of the barrier-dune system 

are considered in the wetlands analysis (refer to Chapter 4.1.1.4). Due to the proximity of coastal spills 

to barrier islands and beaches, coastal spills pose the greatest threat because of their concentration and 

lack of weathering by the time they hit the shore and because dispersants are not used in coastal waters 

due to the negative effects on the shallow-water coastal habitats. Such spills may result from either vessel 

collisions that release fuel and lubricants or from pipelines that rupture. Impacts of a nearshore spill 

would likely be considered short term in duration and minor in scope because the size of such a spill is 

projected to be small. When limited to just oil- and gas-related spill sources such as platforms, pipelines, 

MODUs, and support vessels, Louisiana, Texas, Mississippi, and Alabama could have a total of 130-170, 

5-10, 3-5, and about 2 spills <1,000 bbl/yr, respectively. Louisiana and Texas are the states most likely to 

have a spill ≥1,000 bbl occur in coastal waters (refer to Chapter 3.2.1.7.1 of the 2012-2017 WPA/CPA 

Multisale EIS). The distribution of spill sizes is likely to be similar to those identified in Anderson et al. 

(2012) for OCS spills. Ninety-six percent of spills are <1 bbl (average size = 0.05 bbl) and 98 percent of 

spills are <10 bbl (average size for spills 1-9 bbl = 3 bbl). For more information on spill sizes, refer to 

Chapter 3.2.1.7.1 of the 2012-2017 WPA/CPA Multisale EIS. 

For offshore spills, the spill may be larger but the oil would likely be lessened in toxicity when it 

reaches the coastal environments due to the distance from shore, increased weathering, and the possible 

use of dispersant. Equipment and personnel used in cleanup efforts can generate the greatest direct 

impacts to an area, such as the disturbance of beach and foredune sands through foot traffic and 

mechanized cleanup equipment (e.g., sifters), dispersal of oil deeper into sands and sediments, and foot 

traffic in marshes impacting the distribution of oils and marsh vegetation. Close monitoring and 

restrictions on the use of bottom-disturbing equipment would be needed to avoid or minimize those 

impacts. The cleanup impacts of these spills could result in a short-term (up to 2 years) adjustment in 

beach profiles and configurations during cleanup operations. Beach profiles could be altered in various 

ways when oil is removed from beaches: by hand, using tools such as shovels and rakes; and by heavy 

equipment such as backhoes and graders. Holes may be dug to remove tarballs, and beaches may be 

graded, changing the shape of the beaches. Sand may be lost from the beach as it is removed along with 

oil and tar. Crab burrows and other habitat may be altered, and park visitors may observe an altered 

landscape compared with the natural beach observed previously. Some impact as a result of physical 

contact to lower areas of sand dunes is expected. These contacts would not result in significant 
Description of the Environment and Impact Analysis 4-19

destabilization of the dunes. The long-term stressors to barrier beach communities caused by the physical 

effects and chemical toxicity of an oil spill may lead to decreased primary production, plant dieback, and 

further erosion, particularly if oil is carried onto dunes by hurricanes. 

Currently available information suggests that impacts on barrier islands and beaches from accidental 

impacts associated with the CPA proposed action would be minor. Should a spill other than a lowprobability catastrophic spill, which is not part of the proposed action and not likely expected to occur, 

contact a barrier beach, oiling is expected to be light and sand removal during cleanup activities 

minimized. No significant long-term impacts to the physical shape and structure of barrier beaches and 

associated dunes are expected to occur as a result of the CPA proposed action. Therefore, the CPA 

proposed action would not pose a significant increase in risk to barrier island or beach resources.

Cumulative Impacts 

The OCS oil- and gas-related, impact-producing factors that could have cumulative impacts on 

coastal barrier beaches and associated dunes include dredging, construction and expansion of navigational 

canals and port facilities, pipeline emplacement/landfalls, vessel traffic, oil spills, and oil-spill response 

and cleanup activities. Under the cumulative scenario, up to one OCS oil- and gas-related pipeline 

landfall is projected. This pipeline is expected to be installed using modern techniques, which cause little 

to no impacts to the barrier islands and beaches. Impacts from existing infrastructure could continue to 

cause barrier beaches to narrow and breach. The impacts of oil spills from OCS oil- and gas-related 

sources to the Louisiana, Mississippi, and Alabama coast should not result in long-term alteration of 

landforms if the beaches are cleaned using techniques that do not significantly remove sand from the 

beach or dunes. Barrier beaches in the region around Lafourche, Cameron, Plaquemines, and St. Bernard 

Parishes in Louisiana have the greatest risks of sustaining impacts from oil-spill landfalls because of the 

high concentrations of oil production near that coast and the high volume of oil transported by ships in 

that area. Oil spills as a result of a low-probability catastrophic spill, which is not part of the CPA 

proposed action and not likely expected to occur, are discussed in Appendix B. 

Non-OCS oil- and gas-related impacts include non-OCS oil- and gas-related vessel traffic, 

maintenance dredging, beach protection and stabilization projects, sea-level rise, subsidence, development 

and urbanization, tourism, recreational activities, and the potential for nearshore salinity modifications 

(such as preparation of salt domes for oil storage). In addition, oil spills and oil-spill response and 

cleanup activities can originate from non-OCS oil- and gas-related activities, i.e., State oil and gas activity 

and international tankers. River channelization, sediment deprivation, tropical and extra-tropical storm 

activity, sea-level rise, and rapid submergence have resulted in erosion of most of the barrier and 

shoreline landforms along the Louisiana coast. Storm-induced changes in hydrology have, in some cases, 

changed the current regime responsible for stabilizing the barrier islands. Some beach stabilization 

projects are considered by coastal geomorphologists and engineers to accelerate coastal erosion. The 

beneficial use of maintenance dredged materials and other restoration techniques could be required to 

mitigate some of these impacts. Recreational use of some barrier beaches in the CPA is intense due to 

their accessibility by roads. These activities can cause changes to the beach landscapes. There are 

ongoing restoration efforts to minimize damages to beaches from both natural and human impacts. 

Coastal barrier beaches have experienced severe adverse cumulative impacts from natural processes 

and human activities. Natural processes are generally considered the major contributor to these impacts, 

whereas human activities cause severe local impacts and accelerate the natural processes that deteriorate 

coastal barriers. Human activities that have caused the greatest adverse impacts are river channelization 

and damming, pipeline canals, navigation channel stabilization and maintenance, and beach stabilization 

structures. Deterioration of Gulf barrier beaches is expected to continue in the future. Federal, State, and 

county/parish governments have made efforts to restore or protect the sensitive and vulnerable barrier 

islands and mainland beaches (Dixon and Pilkey, 1991; Penland et al., 2003). 

The CPA proposed action is not expected to adversely alter barrier beach configurations significantly. 

The CPA proposed action is not expected to increase the probabilities of oil spills beyond the current 

estimates. Strategic placement of dredged material from channel maintenance, channel deepening, and 

related actions can mitigate adverse impacts upon those localized areas. Compared with other impacting 

factors on coastal barrier beaches and dunes, the incremental contribution of the CPA proposed action to 

the cumulative impacts to these resources is expected to be small.
4-20 Central Planning Area Lease Sale 247 Supplemental EIS

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search was conducted for information published on barrier beaches and dunes, and various Internet 

sources were examined to determine any recent information regarding barrier beaches and dunes. 

Sources investigated include BOEM; the U.S. Department of the Interior, Geological Survey (USGS), 

National Wetlands Research Center; the USGS Gulf of Mexico Integrated Science Data Information 

Management System; Gulf of Mexico Alliance; State environmental agencies; USEPA; and coastal 

universities. Other websites from scientific publication databases (including Science Direct, Elsevier, the 

NOAA Central Library National Oceanographic Data Center, and JSTOR) were checked for new 

information using general Internet searches based on major themes. Most new and pertinent information 

has been the result of Deepwater Horizon-related research, and these studies have provided insight into 

many aspects of the spill and its effects as it relates to beach and dune environments. 

Hayworth et al (2015) found that oil from the Deepwater Horizon explosion and oil spill remained in 

Alabama’s beach system as surface residual balls and submerged oil mats 4 years after the spill. This 

study serves to expand our understanding of the baseline environment following the Deepwater Horizon

explosion, oil spill, and response. It also provides information about the continuing impacts in the years 

following oil contamination of beaches.

Another recent study has investigated the impacts of non-OCS oil- and gas-related activity. Houser 

et al (2015) studied barrier island resilience and found that, while erosion of beaches and dunes during 

powerful storms occurs over hours and days, it can be years to decades before the beach and dune are able 

to recover to their pre-storm state. This study helps to provide a context for the threats to beaches from 

sources other than OCS oil- and gas-related activities.

While the recent research has provided new information regarding impacts to coastal beaches and 

dunes from oil spills, this new information does not change the conclusions presented in the prior 2012-

2017 Gulf of Mexico EISs because such a low-probability catastrophic event is unlikely to occur and 

because BOEM has already considered the potential irreversible effects to coastal beaches and dunes in 

Appendix B. 

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions presented in the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is 

still incomplete or unavailable information. As discussed in the prior 2012-2017 Gulf of Mexico EISs, 

BOEM has identified incomplete or unavailable information regarding impacts to coastal barrier beaches

and associated dunes in the CPA as a result of the Deepwater Horizon explosion, oil spill, and response, 

as well as future restoration efforts and rates of sea-level rise.

This incomplete or unavailable information may be relevant to reasonably foreseeable significant 

adverse effects because recent events such as the Deepwater Horizon explosion, oil spill, and response 

may have caused changes to baseline conditions for coastal beaches and associated dunes of the Gulf of 

Mexico. This information cannot reasonably be obtained because the long-term effects may not yet be 

detectable and the overall costs in time and money to determine this are exorbitant. A large body of 

information regarding impacts of the Deepwater Horizon explosion, oil spill, and response upon coastal 

barrier beaches and associated dunes is being developed through the NRDA process, but much of it is not 

yet available. BOEM used existing information and reasonably accepted scientific methodologies to 

extrapolate from existing information in completing this analysis and formulating the conclusions 

presented here. For example, the following studies were analyzed with regards to coastal barrier beaches 

and dunes: The National Research Council (2013); Daylander et al. (2014); and Hayworth et al. (2015). 

The National Research Council (2013) found that natural populations of deep-sea, oil-degrading bacteria 

digested a significant amount of the oil, reducing the amount of oil contacting beaches. They also found 

that the effectiveness of berms and freshwater diversions for nearshore and onshore protection of 

shorelines was negligible. Daylander et al. (2014) and Hayworth et al. (2015) provided additional 

information about weathering and the mobility of tarballs on and adjacent to the oiled beaches. The 

results of these recent studies of coastal barrier beaches and dunes indicate that the extent of impacts 

resulting from a low-probability catastrophic oil spill could be extensive but that the oil would be 
Description of the Environment and Impact Analysis 4-21

degraded over time. However, a low-probability catastrophic oil spill is not much more likely with the 

proposed CPA lease sale than without, given the existing level of OCS oil- and gas-related activities and 

the small incremental increase in the activity that is expected from the proposed CPA lease sale. 

Therefore, none of these sources reveal reasonably foreseeable significantly greater adverse impacts, 

whether or not the No Action or an Action alternative is chosen under this Supplemental EIS. 

There are also unknowns regarding the future restoration efforts being planned, such as what projects 

will ultimately be constructed and how successful they may be. This information will not be available 

until such projects are constructed, which is not within the timeline contemplated in the NEPA analysis of 

this Supplemental EIS. However, BOEM used existing information regarding the effects of past projects, 

the plans for restoration projects currently being considered under the RESTORE Act, and past effects of 

coastal development on coastal beaches to anticipate the benefit of restoration projects in the CPA (Gulf 

Coast Ecosystem Restoration Council, 2014; State of Louisiana, Coastal Protection and Restoration 

Authority, 2014; State of Mississippi, Dept. of Environmental Quality, 2014; Alabama Gulf Coast 

Recovery Council, 2014; State of Florida, Dept. of Environmental Protection, 2014). BOEM has 

determined that the scope of the planned restoration projects would likely only partially restore what was 

present historically along the Gulf Coast, although any restoration of coastal barrier beaches and 

associated dunes would likely reduce the land loss rates. However, BOEM has determined that the 

incomplete information is not essential to a reasoned choice among alternatives because BOEM can 

extrapolate the effects of the CPA proposed action based on the effects of past lease sales on earlier 

baselines.

In addition, the future rates of relative sea-level rise are not known with certainty (Intergovernmental 

Panel on Climate Change, 2014), and thus, the resulting impacts to coastal barrier beaches and associated 

dunes are unknown. BOEM has used studies of the effects of sea-level rise on beach habitat (Hinkel 

et al., 2013; Chu et al., 2014), as well as a study that used a likely range of projections of sea-level rise 

(Glick et al., 2013) to assess the likely impacts of sea-level rise to the baseline environment. BOEM used 

this existing information to determine possible impacts of a natural non-OCS oil- and gas-related activity 

on an altered coast and to compare it with the possible impacts of the CPA proposed action. BOEM has 

determined that the incomplete information is not essential to a reasoned choice among alternatives 

because BOEM can extrapolate the effects of the CPA proposed action on expected reduced future 

acreages of wetlands based on the effects of past lease sales on earlier baselines.

BOEM has determined that the incomplete or unavailable information is not essential to a reasoned 

choice among alternatives because the CPA is an active oil and gas region with ongoing exploration, 

drilling, and production activities. In addition, non-OCS energy-related factors will continue to occur in 

the CPA irrespective of the CPA proposed action (i.e., development, urbanization, recreational activities, 

etc.). The potential for effects from changes to the affected environment (post-Deepwater Horizon), 

routine activities, accidental spills (including low-probability catastrophic spills), and cumulative impacts

remains whether or not the No Action or an Action alternative is chosen under this Supplemental EIS. 

Impacts on coastal barrier beaches and associated dunes from either smaller accidental events or lowprobability catastrophic spills would remain the same.

Summary and Conclusion

BOEM has reexamined the analysis for coastal barrier beaches and associated dunes presented in the 

prior 2012-2017 Gulf of Mexico EISs based on the additional information presented above. The 

information discovered does not alter the impact conclusion for coastal barrier beaches and associated 

dunes presented in the prior 2012-2017 Gulf of Mexico EISs. The analysis and potential impacts detailed 

and updated in those NEPA documents still apply for proposed CPA Lease Sale 247. 

4.1.1.4. Wetlands

BOEM has reexamined the analysis for wetlands presented in the prior 2012-2017 Gulf of Mexico 

EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for wetlands presented in those NEPA documents. The 

analysis and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 247.

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 
4-22 Central Planning Area Lease Sale 247 Supplemental EIS

presented in Chapter 4.2.1.4 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.4 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.4 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors on wetlands along the coast adjacent to the CPA 

include pipeline emplacement, construction, and maintenance; navigation channel use (vessel traffic) and 

maintenance dredging; disposal of OCS oil- and gas-related wastes; and use and construction of support 

infrastructure in coastal areas. Other potential impacts that are indirectly associated with OCS oil- and 

gas-related activities are wake erosion resulting from navigational traffic; levee construction that prevents 

necessary sedimentary processes; saltwater intrusion that changes the hydrology, leading to unfavorable 

conditions for wetland vegetation; and vulnerability to storm damage from eroded wetlands. It is 

expected that impacts of pipelines would be reduced or eliminated through mitigation, such as horizontal, 

directional (trenchless) drilling techniques to avoid damages to these sensitive wetland habitats. Although 

maintenance dredging of navigation channels and canals in the CPA is expected to occur, the CPA 

proposed action is expected to contribute minimally to the need for this dredging. Alternative dredgedmaterial disposal methods can be used to enhance and create wetlands. Secondary impacts to wetlands 

from the CPA proposed action would result from OCS oil- and gas-related vessel traffic, contributing to 

the erosion and widening of navigation channels and canals. Overall, the impacts to wetlands from 

routine activities associated with the CPA proposed action are expected to be low due to the small length 

of projected onshore pipelines, the minimal contribution to the need for maintenance dredging, and the 

mitigating measures that would be used to further reduce these impacts.

Accidental disturbances resulting from the CPA proposed action, mainly oil spills, have the potential 

to cause plant mortality and permanent loss of wetlands of the CPA. Offshore oil spills resulting from the 

CPA proposed action would have a low probability of contacting and damaging wetlands along the Gulf 

Coast, except in the case of a low-probability catastrophic spill, which is not part of the CPA proposed 

action and not likely expected to occur (refer to Appendix B). This is because of the distance of the spill 

to the coast, the likely weathered condition of oil (through evaporation, dilution, and biodegradation) 

should it reach the coast, and because wetlands are generally protected by barrier islands, peninsulas, sand 

spits, and in some cases by currents. However, because the protective capacity of barrier islands has been 

reduced due to land lost in hurricanes and anthropogenic factors, there is a greater potential for the oiling 

of coastal wetlands during an accidental event. The causes of coastal and offshore oil spills are 

summarized in Chapters 3.1.1.7 and 3.3.5.2. Although the probability of occurrence is low, the greatest 

threat from an oil spill to wetland habitat is from a spill as a result of an inland or nearshore vessel 

accident or pipeline rupture. Wetlands in the northern Gulf of Mexico are in moderate- to high-energy 

environments; therefore, sediment transport and tidal stirring should reduce the chances for oil persisting 

in the event that these areas are oiled. While a resulting slick may cause impacts to wetland habitat and 

associated seagrass communities, the equipment, chemical treatments, and personnel used for cleanup can 

generate the greatest impacts to the area. Associated foot traffic may work oil farther into the sediment 

than would otherwise occur. Close monitoring and restrictions on the use of bottom-disturbing equipment 

would be needed to avoid or minimize those impacts. In addition, an assessment of the area covered, oil 

type, and plant composition of the wetland oiled should be made prior to choosing remediation 

treatments. These treatments could include mechanical and chemical techniques with onsite technicians. 

Overall, impacts to wetland habitats from an oil spill associated with activities related to the CPA 

proposed action would be expected to be low and temporary because of the small contribution of the CPA 

proposed action to the total OCS activity, the distance of most of the activity from shore, the weathering 

of spilled oil, and the ability of vegetation to recover from exposure to crude oil (Khanna et al., 2013). 

Cumulative Impacts 

The cumulative analysis considers the effects of impact-producing factors related to the CPA 

proposed action, prior and future OCS lease sales in the Gulf of Mexico, and non-OCS oil- and gas-
Description of the Environment and Impact Analysis 4-23

related activities such as State oil and gas activities, other governmental and private projects and 

activities, and natural processes that may affect wetlands. Several OCS oil- and gas-related cumulative 

impact-producing factors could potentially impact wetland resources, including oil spills and cleanup 

activity, OCS oil- and gas-related vessel traffic, construction of OCS oil- and gas-related infrastructure

and support structure (including pipelines), and waste disposal. 

The primary impact-producing factors attributable to the CPA proposed action are pipeline landfalls, 

canal widening, and maintenance dredging of navigation canals because they can result in land loss. 

However, modern construction techniques and regulations reduce impacts to wetlands as a result of these 

activities. In addition, because the increase in pipelines, dredging, and vessel traffic from the CPA 

proposed action are predicted to be minimal, impacts related to these factors are also expected to be 

minimal. The possibility of physical oiling of wetlands from the CPA proposed action as a result of an oil 

spill originating in OCS waters is minimal compared with an oil spill that is closer to the wetlands and 

that could occur in State waters or in rivers, bays, or estuaries. The effects from a spill have the highest 

probability of occurring in Lafourche, Cameron, Plaquemines, and St. Bernard Parishes in Louisiana. 

These are the primary areas where oil produced in the CPA is transported and distributed. If any oil spills 

occur in rivers, bays, or estuaries from pipelines or vessels, they will likely be small and at service bases

or other support facilities, and these small-scale local spills would not be expected to severely affect 

wetlands. Accidental spills as a result of a low-probability catastrophic spill, which is not part of the CPA 

proposed action and not likely expected to occur, may have impacts on wetlands. Low-probability 

catastrophic events are discussed in Appendix B. 

Non-OCS oil- and gas-related cumulative impact-producing factors that could potentially impact 

wetland resources include State oil and gas activities, non-OCS oil- and gas-related vessel traffic, coastal 

infrastructure and development, maintenance of navigation canals, natural processes (including hurricane

and tropical storms), and sea-level rise. Between 2004 and 2009, the Gulf of Mexico coastal region lost a 

net amount of 257,150 ac (104,065 ha) of wetlands (Dahl and Stedman, 2013). Dahl and Stedman (2013) 

reported that saltwater wetland losses in the Gulf of Mexico have been attributed to the effects of severe 

coastal storms such as Hurricanes Katrina and Rita in 2005 and Hurricane Ike in 2008, which inundated 

wetlands with storm surge, abnormally high tides, increased rainfall, runoff, increased sediment and 

debris deposition, and erosion. By comparison, a small percentage of saltwater wetland losses have been 

traced to discrete anthropogenic actions in the Gulf of Mexico (Dahl and Stedman, 2013). Non-OCS oiland gas-related impacts from residential, commercial, agricultural, and silvicultural (forest expansion) 

developments are expected to continue in coastal regions around the Gulf of Mexico. Wetlands are most 

vulnerable to oil spills that may occur in coastal waters, the impacts of which would be primarily 

localized in nature. Many such spills are from non-OCS oil- and gas-related sources, such as State oil and 

gas activities, which can include vessel collisions, pipeline breaks, and shore-based transfer, refining, and 

production facilities. Insignificant adverse impacts on wetlands from maintenance dredging are expected 

because the large majority of the material would be placed in existing disposal areas or used beneficially 

for marsh restoration or creation. Hurricanes and tropical storms can cause extensive damage to 

wetlands, including conversion of large acreages of wetlands to open water. Marine vegetation deposited 

by storms can rest on wetland plants, resulting in mortality. One benefit of storms is that they can be 

capable of delivering sediment from offshore or interior bays into wetland areas, partially offsetting 

erosion. Sea-level rise can impact coastal wetlands by the drowning of plants. Relative sea-level rise, 

which includes local factors such as subsidence, can increase salinity and flooding, resulting in reduced 

productivity of wetland plants (Spalding and Hester, 2007). 

Development pressures in the coastal regions of Louisiana, Mississippi, Alabama, and Florida have 

caused the destruction of large areas of wetlands. In coastal Louisiana, the most destructive 

developments have been the inland oil and gas industry projects, which have resulted in the dredging of 

huge numbers of access channels. Agricultural, residential, and commercial developments have caused 

the most destruction of wetlands in Mississippi, Alabama, and Florida. In Florida, recreational and tourist 

developments have been particularly destructive. Groundwater extraction, vessel traffic, the drainage of 

wetland soils, and the construction of buildings, roads, and levees have also caused the loss of wetlands. 

The cumulative effects of human and natural activities in the coastal area have severely degraded the 

deltaic processes and have shifted the coastal area from a condition of net land building to one of net land 

loss. Therefore, wetland loss is expected to continue. Impacts are, to some extent, offset by coastal 

restoration programs. Examples of these programs are the Coastal Impact Assistance Program; the 

Coastal Wetlands Planning, Protection, and Restoration Act; and the RESTORE Act (refer to Chapter 
4-24 Central Planning Area Lease Sale 247 Supplemental EIS

3.3.4.4 of this Supplemental EIS and Chapter 3.3.4.4 of the 2012-2017 WPA/CPA Multisale EIS). The 

CPA proposed action represents a small (<5%) portion of the OCS oil- and gas-related impacts that will 

occur over the 40-year analysis period. Impacts associated with the CPA proposed action are a minimal 

part of the overall OCS oil- and gas-related impacts. The incremental contribution of the CPA proposed 

action to the cumulative impacts to coastal wetlands is minimal compared with the impacts associated 

with non-OCS oil- and gas-related activities in the Gulf of Mexico.

New Information Available Since the Publication of 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search was conducted for information published on northern Gulf of Mexico wetland communities, 

and various Internet sources were examined to determine any recent information regarding these 

communities. Sources investigated include BOEM, the USGS National Wetlands Research Center, the 

USGS Gulf of Mexico Integrated Science Data Information Management System, Gulf of Mexico 

Alliance, State environmental agencies, USEPA, and coastal universities. Other websites from scientific 

publication databases (including ScienceDirect, Elsevier, the NOAA Central Library National 

Oceanographic Data Center, and JSTOR) were checked for new information using general Internet 

searches based on major themes.

Numerous studies have been published regarding impacts of the Deepwater Horizon explosion, oil 

spill, and response. In a study of the side effects of the response, Middleton et al. (2015) found that, after 

the Davis Pond freshwater diversion project was operated at capacity for almost 4 months in an effort to 

keep offshore oil from threatened coastal wetlands, above-ground litter production by swamp plants 

increased by 2.7 times of levels in 2007-2011 and the biomass of several species increased. Zengel et al. 

(2015) compared the effectiveness of several shoreline cleanup treatments in heavily oiled salt marsh. 

They found that, of the methods used, manual treatment (conducted by small crews using hand tools to 

remove oil and oiled debris) appeared to strike the right balance between improving oiling and habitat 

conditions while not causing additional detrimental effects. They further found that planting following 

treatment increased recovery of the marsh. Andersen (2015) reviewed numerous studies of the oil spill’s 

impact and noted that aerial imagery was capable of detecting impacts penetrating up to 40 m (131 ft) into 

wetlands from shorelines, while ground-based visual observations were only able to confirm shoreline 

oiling and penetration into adjacent marshes of much lower distances. He also noted that, although 

wetland plants were negatively impacted by the oil, many of the affected areas are likely capable of rapid 

regeneration. Biber et al. (2015) found that salt marshes affected by oil along exposed, high-energy 

coastlines experienced more rapid removal or degradation of the oil contamination by tidal or wave 

action, with more rapid plant recovery. In contrast, in protected lagoonal shorelines, oil contamination 

tends to persist in the sediments, with a longer recovery of plants. 

Other studies used mesocosms to examine the responses of wetland soil to oil and dispersants. Shi 

and Yu (2014) exposed marsh sediment to crude oil, with and without the dispersant COREXIT EC 

9500A. They found that the dispersant decreased denitrification but stimulated organic matter 

mineralization. This result suggests that the loss of organic matter from the marsh could threaten its 

stability, and the more reducing conditions observed would tend to preserve the oil in the ecosystem for a 

longer time by decreasing its degradation. Batubara et al. (2014) exposed wetland soil to phenanthrene, 

comparing degradation rates at intertidal and subtidal simulations. They found that degradation occurred 

more rapidly in the intertidal setting, mirroring earlier field experiments (on beaches) by others (Elango 

et al., 2014; Lemelle, 2012). These studies can be used to better understand the possible impacts to 

marshes following an oiling event.

Other recent research focused on issues other than oil-spill impacts. Pate (2014) used the geographic 

information system (GIS) analysis to investigate feasibility, cost, and benefits of canal backfilling as a 

restoration technique, in concert with approved projects in Louisiana’s coastal marshes. He found that, 

using conservative estimates, over 26,000 ac (10,522 ha) could be backfilled at a significant savings using 

this approach. Hu et al. (2015) modeled the effect of wetlands on reducing storm surge in the Breton 

Sound Basin of Louisiana. Stem height and, to a lesser extent, stem density increased the maximum 

surge reduction and maximum surge reduction rate. The maximum surge reduction decreased 

significantly with increased wind intensity, and the maximum surge reduction rate was the highest with a 
Description of the Environment and Impact Analysis 4-25

fast-moving weak storm. This study provides insight into how much storm protection may be provided 

by coastal wetlands to vulnerable communities.

Kaiser (2015) forecasted offshore vessel activity and estimated between 53,000 and 119,000 trips per 

year from 2012 to 2017. Approximately half of the trips would emanate from Port Fourchon, Louisiana, 

and another 14 percent would emanate from Cameron, Louisiana. While this was not a study of wetlands, 

it helps to assess wetland impacts from routine activities by establishing that over 64 percent of the vessel 

traffic occurs in Louisiana.

While the recent research has provided much new information regarding impacts to wetlands from oil 

spills, this new information does not change the conclusions presented in the prior 2012-2017 Gulf of 

Mexico EISs because a catastrophic event is unlikely to occur and because BOEM has already considered 

the potential irreversible effects to wetlands, such as erosion and permanent loss, in Appendix B

(Chapter B.3.1.4).

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As identified in the resource analyses in this Supplemental EIS, 

as well as in the prior 2012-2017 Gulf of Mexico EISs, BOEM has identified incomplete or unavailable 

information regarding wetlands in the CPA. This incomplete or unavailable information may be relevant 

to reasonably foreseeable significant adverse effects because recent events such as the Deepwater

Horizon explosion, oil spill, and response may have caused changes to baseline conditions for coastal 

wetlands of the Gulf of Mexico. A large body of information regarding impacts of the Deepwater 

Horizon explosion, oil spill, and response upon coastal wetlands is being developed through the NRDA 

process, but much of this information is not yet available. Other unknowns are future benefits from 

restoration projects and future impacts of sea-level rise.

BOEM has determined that the information is not essential to a reasoned choice among alternatives 

because the CPA is an active oil and gas region with ongoing exploration, drilling, and production 

activities. In addition, non-OCS energy-related factors will continue to occur in the CPA irrespective of 

the CPA proposed action (i.e., commercial development, subsidence, hurricanes, etc.). The potential for 

effects from changes to the affected environment (post-Deepwater Horizon), routine activities, accidental 

event (including low-probability catastrophic spills), and cumulative impacts remains whether or not the 

No Action or an Action alternative is chosen under this Supplemental EIS. Impacts on wetlands from 

either smaller accidental events or low-probability catastrophic events will remain the same.

BOEM used existing information and reasonably accepted scientific methodologies to extrapolate 

from existing information in completing this analysis and formulating the conclusions presented here. 

For example, the following studies were analyzed with regards to wetlands: Middleton et al. (2015); 

Zengel et al. (2015); Andersen (2015); Biber et al. (2015); Shi and Yu (2014); and Batubara et al. (2014). 

The results of these recent studies of wetlands indicate that the extent of impacts resulting from a 

catastrophic oil spill could be extensive but that the oil would be degraded over time. While marsh 

vegetation can recover from oil contamination, the response methods and wave energy environment can 

influence the degree of recovery and the length of time required. However, a low-probability catastrophic 

oil spill is not much more likely with the proposed CPA lease sale than without it, given the existing level 

of OCS oil- and gas-related activities and the small incremental increase in that activity expected from the 

proposed CPA lease sale. Therefore, none of these sources reveal reasonably foreseeable significantly 

greater adverse impacts whether or not the No Action or an Action alternative is chosen under this 

Supplemental EIS. 

There are also data gaps regarding the future restoration efforts being planned in coastal states, such 

as what projects will ultimately be constructed and how successful they may be. This information will 

not be available until such projects are constructed, which is not within the timeline contemplated in the 

NEPA analysis of this Supplemental EIS. However, BOEM used existing information regarding the 

effects of past projects, the plans for restoration projects currently being considered under the RESTORE 

Act, and past effects of coastal development on coastal wetlands to anticipate the benefit of restoration 

projects in the CPA (Pate, 2014; Gulf Coast Ecosystem Restoration Council, 2014; Texas Commission on 

Environmental Quality, 2014b; State of Louisiana, Coastal Protection and Restoration Authority, 2014; 

State of Mississippi, Dept. of Environmental Quality, 2014; Alabama Gulf Coast Recovery Council, 
4-26 Central Planning Area Lease Sale 247 Supplemental EIS

2014; State of Florida, Dept. of Environmental Protection, 2014). BOEM has determined that the scope 

of the planned restoration projects would likely only partially restore what was present historically along 

the Gulf Coast, although any restoration of wetlands would reduce the land loss rates. However, BOEM 

has determined that the incomplete information is not essential to a reasoned choice among alternatives 

because BOEM can extrapolate the effects of the CPA proposed action based on the effects of past lease 

sales on earlier baselines and can reasonably use the extrapolation in current analyses.

The rate of future sea-level rise is unknown (Hausfather, 2013), but BOEM has used studies of the 

effects of sea-level rise on wetland plants, as well as a study that used a likely range of projections of sealevel rise (Glick et al., 2013), to assess the likely impacts of sea-level rise to the baseline environment. 

BOEM used this existing information to determine possible impacts of a natural non-OCS oil- and gasrelated activity on an altered coast and compare it with the possible impacts of the CPA proposed action. 

BOEM has determined that the incomplete information is not essential to a reasoned choice among 

alternatives because BOEM can extrapolate the effects of the CPA proposed action on expected reduced 

future acreages of wetlands based on the effects of past lease sales on earlier baselines.

Summary and Conclusion

BOEM has reexamined the analysis for wetlands presented in the prior 2012-2017 Gulf of Mexico 

EISs based on the additional information presented above. No new information was discovered that 

would alter the impact conclusion for wetlands presented in those NEPA documents. The analysis and 

potential impacts detailed and updated in those documents still apply for proposed CPA Lease Sale 247. 

4.1.1.5. Seagrass Communities

BOEM has reexamined the analysis for seagrass communities presented in the prior 2012-2017 Gulf 

of Mexico EISs based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for seagrass communities presented in those NEPA

documents. The analysis and potential impacts discussed in those documents still apply for proposed 

CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.5 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.5 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.5 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors on seagrass communities of the CPA are the 

construction of pipelines, canals, navigation channels, and onshore facilities; maintenance dredging; and 

vessel traffic (e.g., propeller scars). These factors could result in plants being uprooted, submerged 

vegetation beds being scarred or lost; decreased oxygen in the water; turbidity; and the burial of plants 

from suspended sediment. However, the routine OCS oil- and gas-related activities in the CPA impacting 

seagrasses are not predicted to significantly increase in occurrence and range in the near future. Only a 

single new pipeline landfall is expected as a result of the CPA proposed action. Requirements of other 

Federal and State programs, such as avoidance of seagrass and submerged vegetation communities or the 

use of turbidity curtains, reduce undesirable effects on submerged vegetation beds from potentially 

harmful activities. Local programs decrease the occurrence of prop scarring in grass beds, and generally 

channels used by OCS oil- and gas-related vessels are away from exposed submerged vegetation beds. 

Because of these requirements and implemented programs, along with the beneficial effects of natural 

flushing (e.g., from winds and currents), any potential effects from routine OCS oil- and gas-related 

activities on submerged vegetation in the CPA are expected to be short term, localized, and not 

significantly adverse.

Accidental disturbances resulting from the CPA proposed action, including oil spills, have the 

potential to change community structure, decrease growth rates, cause death, or cause a decline in 
Description of the Environment and Impact Analysis 4-27

ecological services by seagrass communities of the CPA if an accidental event was to occur in close 

proximity to these habitats. Although the size would be small and the duration would be short term, the 

greatest threat to inland, submerged vegetation communities would be from an inland spill resulting from 

a vessel accident or pipeline rupture. Because pipelines can be shut off, ships carry limited amounts of

oil, and response vessels can more easily access nearshore areas, it is expected that the resulting spill 

would be small and shorter in duration, resulting in short-term and localized impacts. There is also the 

remote possibility of a small offshore spill reaching submerged vegetation beds; this would have similar 

effects as an inshore spill. The resulting impacts to seagrass from contacting oil could range from the 

sloughing of epiphytes to plant death. Further, an offshore spill could result in more sinking oil (e.g., 

tarballs and patties) than an inshore spill, and oil could become entrained within seagrass root and leaf 

complex near the seafloor. Because prevention and cleanup measures can have negative effects on 

submerged vegetation, close monitoring and restrictions on the use of bottom-disturbing equipment would 

be needed to avoid or minimize those impacts. The floating nature of nondispersed crude oil, the regional 

microtidal range, the dynamic climate with mild temperatures, and the amount of microorganisms that 

consume oil would alleviate prolonged effects on submerged vegetation communities. Also, safety and 

spill-prevention technologies are expected to continue to improve and will minimize the effects to 

submerged vegetation from an accidental event related to the CPA proposed action. Impacts to 

submerged vegetation from an accidental event related to the CPA proposed action are expected to be 

negligible.

Cumulative Impacts 

The cumulative OCS oil- and gas-related activities that present the greatest threat of impacts to 

submerged vegetation communities are dredging, oil spills, and pipeline installation. In general, the CPA 

proposed action would cause a minor incremental contribution to impacts on submerged vegetation from 

related dredging, pipeline installations, and oil spills. Of those mentioned above, dredging generates the 

greatest overall risk to submerged vegetation by uprooting and burying plants, decreasing oxygen in the 

water, and reducing water clarity in an area. A low-probability catastrophic spill, which is not part of the 

CPA proposed action and not likely expected to occur, could also impact seagrass communities. Refer to 

Appendix B for more details on the impacts of a low-probability catastrophic spill. Further, non-OCS 

oil- and gas-related dredging and vessel traffic, boat scarring, changes in salinity and nutrient inputs 

(Waycott et al., 2009; Orth et al., 2006), changes to natural flow regimes from constructed structures, and 

storm events could continue to cause direct damage to seagrass beds by physical destruction, increased 

turbidity and burial of plants, and reduction in favorable environmental conditions for seagrass bed 

growth. However, the incremental contribution of stress from the CPA proposed action to submerged 

vegetation is reduced by the implementation of proposed lease stipulations, mitigating measures currently 

in place, and the small probability of an oil spill. The incremental contribution of the CPA proposed 

action to the overall cumulative impacts on seagrass communities that would result from the OCS 

Program and non-OCS oil- and gas-related activities is expected to be negligible.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of various printed and Internet sources was conducted for any recent information published 

regarding coastal submerged vegetation. Sources investigated include BOEM, the National Oceanic and 

Atmospheric Administration, the USGS National Wetlands Research Center, the USGS Gulf of Mexico 

Integrated Science Data Information Management System, Seagrass Watch, Gulf of Mexico Alliance, 

State environmental agencies, USEPA, and coastal universities. Other websites from scientific 

publication databases (including Science Direct, SCIRUS, Google Scholar, Elsevier, Pro Quest, and 

JSTOR) were checked for new information using general Internet searches based on major themes. No 

new information that would add to the analyses or change the conclusions was discovered since 

publication of CPA 241/247 and EPA 226 Supplemental EIS. 
4-28 Central Planning Area Lease Sale 247 Supplemental EIS

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the previous conclusions 

from the prior 2012-2017 Gulf of Mexico EISs are still valid because no new information on seagrass 

communities pertinent to the CPA proposed action has become available since publication of those NEPA

documents. BOEM has identified unavailable information regarding seagrass communities in the CPA. 

This information cannot reasonably be obtained because the long-term effects may not yet be detectable 

and the overall costs in time and money to determine this are exorbitant. This unavailable information 

may be relevant to adverse effects because much of the data related to research and monitoring of the 

Deepwater Horizon explosion, oil spill, and response has yet to be completed and made publicly 

available. Other unavailable information may be related to university-related research that has yet to be 

published as a thesis or a dissertation.

BOEM used existing information and reasonably accepted scientific methodologies to extrapolate 

from existing information in completing this analysis and formulating the conclusions presented here. 

For example, Fodrie and Heck (2011) did not sample all of the seagrasses across the northern GOM, but 

they sampled enough locations where OCS oil- and gas-related resource development occurs to allow for 

a general conclusion that changes within seagrass beds are not related to OCS oil- and gas-related 

development or the Deepwater Horizon oil spill. Gab-Alla (2000), Nievales (2009), and Mauseth et al. 

(2001) each showed that, historically, oil spills in other parts of the world have had little long-term 

negative impact on seagrass environments. Overall, none of the new sources or sources referenced in the 

prior 2012-2017 Gulf of Mexico EISs reveal any reasonably foreseeable significant adverse impacts as a 

result of the CPA proposed action. 

Summary and Conclusion

BOEM has reexamined the analysis for seagrass communities presented in the prior 2012-2017 Gulf 

of Mexico EISs understanding that no new information on seagrass communities has become available 

since publication of the those NEPA documents. Therefore, no new information was discovered that 

would alter the impact conclusion for seagrass communities in those documents. The analysis and 

potential impacts discussed in those documents still apply for proposed CPA Lease Sale 247.

4.1.1.6. Live Bottoms (Pinnacle Trend and Low Relief) 

BOEM has reexamined the analysis for live bottoms presented in the prior 2012-2017 Gulf of Mexico 

EISs based on additional information presented below. No new significant information was discovered 

that would alter the impact conclusion for live bottoms presented in those NEPA documents. The 

analysis and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.6 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.6 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.6 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors on live bottoms of the CPA are seafloor-disturbing 

activities (e.g., anchoring, infrastructure emplacement, and infrastructure removal), waste discharge (e.g., 

produced waters and drilling muds), resuspension of sediments (e.g., drill cuttings and pipeline burial), 

and explosive severance activities. These impact-producing factors have the potential to damage live 

bottom habitats and disrupt associated communities. Potential impacts as a result of seafloor-disturbing 

activities are mitigated through avoidance. The proposed Live Bottom (Pinnacle Trend) Stipulation

would protect features by requiring all bottom-disturbing activity be distanced at least 30 m (100 ft) from 

pinnacles. In addition, case-by-case reviews of permit applications allow BOEM to identify and protect 

live bottoms that occur outside identified live bottom low-relief blocks. A Live Bottom (Low Relief) 
Description of the Environment and Impact Analysis 4-29

Stipulation can also be applied to leases in live bottom low-relief blocks with water depths of 100 m 

(328 ft) or less in the EPA and northeast corner of the CPA; however, no blocks subject to the Live 

Bottom (Low Relief) Stipulation will be offered for lease in the proposed CPA lease sale. Measures 

distancing wells and structures from live bottom features would also reduce the potential for other impactproducing factors to adversely affect live bottom organisms. Impacts would be expected to be negligible.

Waste discharges from routine OCS oil- and gas-related operations may cause localized increases in 

turbidity or be moderately toxic to marine organisms at the point of discharge, potentially impacting 

benthos near drill sites. However, waste discharges rapidly disperse and would have little or no 

measurable effect on organisms inhabiting live bottoms distanced 30 m (100 ft) or more from the 

discharge point. Drilling muds and cuttings may be diluted 100 times at a distance of 10 m (33 ft) from 

the source, and up to 1,000 times more diluted at a distance of 100 m (328 ft) from the discharge point 

(Neff, 2005). Deposition of drilling muds and cuttings near the Pinnacle Trend and low-relief areas, 

distanced 30 m (100 ft) or more from OCS oil- and gas-related activities, would not greatly impact the 

biota of the live bottoms because the communities associated with live bottom features in the CPA are 

adapted to turbid (nepheloid) conditions and high sedimentation rates associated with the outflow of the 

Mississippi River (Gittings et al., 1992). Similarly, structure removal, pipeline burial, and other activities 

that resuspend sediment have the potential to impact communities associated with live bottoms if not 

sufficiently distanced from these features. The proposed Live Bottom (Pinnacle Trend) Stipulation and 

BOEM’s case-by-case reviews would prevent these activities from occurring within 30 m (100 ft) of any 

live bottom, mitigating potential impacts.

The use of explosive severance methods during decommissioning activities has the potential to 

impact live bottoms and associated fauna. The BSEE Interim Policy Document 2013-07, “Rigs-to-Reefs

Policy,” specifies the use of explosive severance methods “will not be approved if analysis determines 

they will cause harm to established artificial reef sites and/or natural biological/topographic features, such 

as the Flower Garden Banks and Pinnacles.” This policy, coupled with the distancing requirement and 

case-by-case reviews to identify and protect sensitive habitat, will minimize any potential for live bottoms 

to be adversely impacted by decommissioning operations. 

Accidental disturbances resulting from the CPA proposed action, including oil spills, have the 

potential to damage live bottom habitats and disrupt associated communities. Live bottom features 

represent a small fraction of the continental shelf area in the CPA. The proposed Live Bottom (Pinnacle 

Trend) Stipulation (Chapter 2.3.1.3.2) and case-by-case reviews of permit applications would distance 

activities that could result in oil spills and loss of well control at least 30 m (100 ft) from the features, 

mitigating most of the potential impacts. In a subsurface spill or loss of well control situation, it would be 

expected that the majority of released oil would rise to the surface and that the most heavily oiled 

sediments would likely be deposited before reaching live bottom features. A subsurface plume may 

impact sessile biota of live bottom features. Impacts may include loss of habitat, biodiversity, and live 

coverage; change in community structure; and reduced reproductive success. Distancing OCS oil- and 

gas-related activities from these features would allow for oil to mix with the surrounding water and 

become less concentrated, thus reducing toxicity to live bottom organisms. 

Surface oil spills also have the potential to impact live bottom features. Some pinnacle features rise 

to within 40 m (130 ft) of the sea surface, while many others have much less relief or are in deeper 

waters. The distance to the sea surface serves to buffer these features from surface spills. Any oil that 

might contact pinnacle features would probably be at low concentrations because the expected mixing 

depth in the water column is usually less than the peak of the tallest pinnacles. Outside the designated 

Live Bottom (Low Relief) blocks, low-relief features are typically found at depths sufficiently deep to 

prevent surface spills from severely impacting sensitive habitat. Oil becomes diluted as it physically 

mixes with the surrounding water and moves into the water column. Any oil that might be driven to a 

depth of 10 m (33 ft) or more is expected to be diluted to such a degree that any effects to these features 

would be minor. Any features in water shallower than 10 m (33 ft) would be located far from the source 

of activities in the CPA proposed action. Therefore, concentrated oil is not normally expected to reach 

live bottom features, and any impacts from diluted oil would be sublethal. 

Suspended sediment and oil adhered to sediment in the water column as a result of a loss of well 

control may impact benthic organisms. However, because OCS oil- and gas-related activities would be 

distanced at least 30 m (100 ft) from live bottom features, the heaviest sediment concentrations would be 

expected to fall out of suspension and disperse before sensitive features could be severely impacted. Live 

bottom organisms of the CPA are located within the influence of the Mississippi River plume and have 
4-30 Central Planning Area Lease Sale 247 Supplemental EIS

adapted to turbid (nepheloid) conditions and high sedimentation rates associated with the outflow of the 

Mississippi River (Gittings et al., 1992). Many organisms also have the ability to rid themselves of 

sediment through ciliary action and mucus shedding. 

In summary, the proposed Live Bottom (Pinnacle Trend) Stipulation and case-by-case reviews of 

permit applications would, through avoidance, mitigate potential impacts to live bottom communities as a 

result of routine activities and accidental disturbances. In addition, because no Live Bottom (Low Relief) 

blocks are included in the CPA proposed action, most live bottom features are distanced from oilproducing activity. In the unlikely event that oil from a spill reached the biota of a live bottom, the effects 

would be primarily sublethal and impacts would be at the community level. However, in such an event, if 

oil impacted a live bottom community at lethal concentrations, coral recovery could take in excess of 

10 years (Fucik et al., 1984). Overall impacts as a result of routine activities and accidental disturbances 

would be expected to be minor. 

Cumulative Impacts 

The cumulative analysis considers impacts resulting from ongoing routine oil and gas operations, as 

well as those resulting from past and future OCS leasing. These impacts include seafloor-disturbances 

(e.g., anchoring, structure emplacement, and structure removal), waste discharge (e.g., drilling muds, 

cuttings, and effluent), and accidental disturbances (e.g., loss of well control and oil spills). Potential 

non-OCS oil- and gas-related factors include vessel anchoring, import tankering, storms, and commercial 

fishing.

The OCS oil- and gas-related seafloor-disturbing activities represent the greatest threat to live 

bottoms. Potential impacts may be avoided through the continued application of the proposed Live 

Bottom (Pinnacle Trend) Stipulation and case-by-case review of permit applications for the presence of 

live bottom habitat and mitigation of potential impacts. This stipulation would avoid mechanical damage 

to live bottom habitat by prohibiting bottom-disturbing activities from occurring within 30 m (100 ft) of 

live bottoms. The 30 m (100 ft) buffer would also diminish the potential for adverse impacts resulting 

from operational discharges, due to the highly localized and temporary effect of such discharges. The 

USEPA’s discharge regulations and permits further reduce the potential for discharge-related impacts.

The majority of oil released below the sea surface rises and should not physically contact organisms 

on live bottoms. In the unlikely event that oil from a subsurface spill would reach the biota of a live 

bottom, the effects would be primarily sublethal. In the very unlikely event that oil from a subsurface 

spill reached an area containing coral cover in lethal concentrations, the recovery period could exceed 

10 years (Fucik et al., 1984). In the event that a live bottom suffers severe mechanical damage (e.g., 

vessel collision), recovery could take decades depending on the extent of the damage. Because these 

events are rare, the potential for impacts is considered low. For information on impacts resulting from a 

catastrophic spill, refer to Appendix B. 

Non-OCS oil- and gas-related activities (e.g., anchoring, trawling, and vessel collisions) can damage 

live bottoms, resulting in impacts similar to those described above. Commercial fishing activities may 

dislodge or damage organisms inhabiting live bottoms if lines or trawls are dragged across the live bottom 

surface or become entangled. Natural events of sufficient magnitude (e.g., hurricanes or earthquakes) 

may also cause severe impacts. Recreational SCUBA diving, fishing, and discharges or spills from 

tankering of imported oil may also have adverse impacts on live bottoms. Overall, the incremental 

contribution of the CPA proposed action to the cumulative impact is negligible.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of Internet information sources and scientific journals was conducted to determine the 

availability of recent information. This search revealed new information relevant to an analysis of the 

potential impacts of OCS oil- and gas-related activities on live bottom benthic communities. 

The most relevant information for this Supplemental EIS was the publication of data related to the 

apparent mixing of surface waters to a depth of at least 75 m (246 ft) in the Pinnacle Trend area during 

the passage of Tropical Storm Bonnie in July 2010 (Silva et al., 2015). These mixing depths are greater 

than what has been expected under normal conditions, and the authors hypothesize unusually strong wave 
Description of the Environment and Impact Analysis 4-31

action from the storm as the mechanism. The significance for live bottom features is that Silva et al. 

(2015) also documented acute impacts to gorgonians and black corals on two large Pinnacle Trend reef 

features at these depths, seemingly caused by acute exposure to high concentrations of surface oil and/or 

dispersant (presumably sourced from the Deepwater Horizon). The submerged oil and/or dispersant 

likely reached the live bottom features in relatively undiluted concentrations, leading to lethal and 

sublethal impacts. Although this happened during Tropical Storm Bonnie, it, required a highly unusual 

combination of conditions in order to occur: (1) a very large amount of surface oil associated with a 

catastrophic-level spill event (much greater than the amount expected for accidental events); and 

(2) unusually strong winds and surface waves that are only expected during tropical storm-level extreme 

weather conditions. Therefore, though this result is noteworthy, its unlikelihood and the catastrophic 

levels of oil/dispersant involved means that it does not change the overall conclusions for accidental 

impacts to live bottom features. 

For additional information, refer to Chapters 4.1.1.18 and 4.1.1.19 of this Supplemental EIS and 

Chapters 4.1.1.18 and 4.1.1.19 of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 

226 Supplemental EIS. Therefore, BOEM finds that, as more information has become available, the 

research supports the analyses in anticipating localized, temporary impacts.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplemental EIS, as well as in the prior 

2012-2017 Gulf of Mexico EISs, BOEM has identified incomplete or unavailable information related to 

live bottoms in the CPA. The information presented in Silva et al. (2015) demonstrates the incomplete 

state of knowledge about various potential impacts to organisms associated with live bottoms (Pinnacle 

Trend and low relief) as a result of the Deepwater Horizon oil spill and response. However, available 

information on species and habitats similar to those associated with the Pinnacle Trend and low relief live 

bottoms provides sufficient basis from which to extrapolate potential impacts from routine activities and 

accidental events; it is reasonable to assume that similar responses may be expected. Additional data 

collected in the vicinity of the Pinnacle Trend features are under development through the NRDA process 

and may be relevant to an analysis of live bottom (Pinnacle Trend and low relief) habitat in the CPA. 

However, further analysis of these data may take years to complete and the outcome cannot be predicted. 

Although the body of available information is incomplete and long-term effects are not yet known, 

evidence does not suggest that assemblages associated with live bottom (Pinnacle Trend and low relief) 

habitat are likely to sustain severe adverse impacts from routine activities and accidental events (refer to 

Appendix B for more information about catastrophic spill impacts). BOEM has determined that the 

incomplete or unavailable information is not essential to a reasoned choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for live bottoms presented in the prior 2012-2017 Gulf of Mexico 

EISs based on the additional information presented above. No new significant information was 

discovered that would alter the impact conclusion for live bottoms presented in those NEPA documents 

because of the available scientifically credible evidence in this analysis and based upon accepted 

scientific methods and approaches. The analysis and potential impacts discussed in those documents still 

apply for proposed CPA Lease Sale 247. 

4.1.1.7. Topographic Features

BOEM has reexamined the analysis for topographic features presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for topographic features presented in those NEPA

documents. The analysis and potential impacts discussed in those documents still apply for proposed 

CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 
4-32 Central Planning Area Lease Sale 247 Supplemental EIS

presented in Chapter 4.2.1.7 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.7 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.7 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Topographic features are hard bottom habitats and are rare compared with the ubiquitous soft bottoms 

in the GOM (Parker et al., 1983). These features can be upthrusts of rock due to an uplift of the 

underlying salt (diapirs) or the remnants of fossilized shorelines. These topographic highs, or subsea 

banks, provide an island of hard substrate in a virtual ocean of soft bottoms. Wherever rock protrudes up 

into the water column, reef organisms may thrive. The type of organisms inhabiting a reef is determined 

by environmental conditions. There are 37 protected topographic features in the GOM: 21 in the WPA 

and 16 in the CPA. 

Because of the recognized importance of the topographic features, BOEM proposes attaching the 

Topographic Features Stipulation to OCS oil and gas leases within Topographic Feature Stipulation 

blocks. When applied, this mitigation would prevent most of the potential impacts on topographic 

features from bottom-disturbing activities (structure removal and emplacement) and operational 

discharges associated with the CPA proposed action through avoidance. In addition, it would distance 

topographic features from possible accidental events. The mitigation would require that bottomdisturbing activities be located at least 152 m (500 ft) from a topographic feature’s No Activity Zone and 

that drill cuttings and fluids from wells within designated shunting zones must be shunted to the seafloor, 

although shunting requirements can vary among features.

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors on topographic features of the CPA could include 

bottom-disturbing activities such as anchoring, infrastructure emplacement or removal, and drillingeffluent and produced-water discharges. These factors could result in crushing and smothering of 

sensitive organisms and exposure to concentrated discharges. If the Topographic Features Stipulation is 

applied, it will minimize the potential impacts to the topographic features by distancing bottom-disturbing 

activities from the sensitive habitat. The distancing eliminates the possibility of anchors, pipelines, and 

structures being placed on top of the features, and structure removal activity will be distanced enough to 

minimize impacts to topographic features. If any contaminants reach topographic features, the 

contaminants would be diluted from their original concentration, and impacts that may occur should be 

minimal. In addition to the mitigations, discharges or activities that could harm topographic features are 

regulated by other agencies, including discharge permit restrictions from USEPA and essential fish 

habitat restrictions from NOAA. Furthermore, the high-energy environment and prevailing water currents 

associated with topographic features would help protect the features by enabling rapid turnover of the 

water column.

Adverse effects from accidental disturbances resulting from the CPA proposed action could include 

surface and subsurface oil spills, and turbidity and sedimentation from loss of well control with 

substantial quantities of oil. Each has the potential to disrupt and alter the environmental, commercial, 

recreational, and aesthetic values of topographic features of the CPA through oiling and sedimentation. 

The proposed Topographic Features Stipulation would assist in preventing most of the possible accidental 

impacts on topographic feature communities by increasing the distance of such events from the 

topographic features. It is expected that the majority of subsurface oil released during an accidental event 

would rise rapidly to the surface and that the most heavily oiled sediments in the water column would 

likely be deposited on the seafloor before reaching the topographic features. In the event that diluted oil 

from a subsurface spill did reach the biota of a topographic feature, the effects would be primarily 

sublethal and impacts would be at the community level. Any turbidity, sedimentation, and oil adsorbed to 

sediment particles would also be at low concentrations by the time the topographic features were reached, 

likely resulting in primarily sublethal impacts. Impacts from a surface oil spill on topographic features 

are also lessened by the distance of the spill to the features, the depth of the features, and the prevailing 

water currents that sweep around the features. It should be noted that a low-probability catastrophic spill

is not a part of the CPA proposed action and not likely expected to occur. For information on impacts 

resulting from events outside the scope of routine activities and accidental events, refer to Appendix B. 
Description of the Environment and Impact Analysis 4-33

Cumulative Impacts 

The cumulative impact from routine OCS oil- and gas-related operations includes effects resulting 

from the CPA proposed action, as well as those resulting from past and future OCS leasing. These 

operations include anchoring, structure emplacement, muds and cuttings discharge, effluent discharge, oil 

spills, and structure removal. Without mitigation, these factors could result in crushing and smothering of 

organisms on topographic features or exposure to concentrated discharges or oil. Low-probability 

catastrophic spills in the vicinity of one of these features could also potentially cause damage to benthic 

biota (refer to Appendix B for more details). It should be noted that a low-probability catastrophic spill 

is not a part of the CPA proposed action and not likely expected to occur. Impacts from OCS oil- and 

gas-related activities would be mitigated by the continued application of the proposed Topographic 

Features Stipulation, precluding physical damage caused by oil and gas leaseholders by establishing a 

buffer around the features. As such, little impact would be incurred by the biota of the topographic 

features as a result of OCS oil- and gas-related activities. The USEPA’s discharge regulations and 

permits would further reduce discharge-related impacts.

Potential non-OCS oil- and gas-related factors include vessel anchoring, SCUBA diving, treasurehunting activities, import tankering, heavy storms and hurricanes, the collapse of the tops of the 

topographic features due to dissolution of the underlying salt structure, and fishing activities. Many of 

these non-OCS oil- and gas-related factors may result in physical damage to organisms that colonize 

topographic features. For example, treasure hunting activities in the 1980’s resulted in several large 

cavities being dug on one of the topographic features that has yet to recover. Anchoring can result in the 

destruction of hard corals due to the ability of anchor lines to cut through the coral heads. Anchoring can 

also result in the tearing of soft corals from the seafloor during anchor removal or the movement of the 

anchoring line through the water column. Because corals and other benthic fauna are slow growing, 

physical disturbance represents the greatest threat to the organisms that colonize topographic features. 

With the application of stipulations and regulations, the incremental contribution of the CPA proposed 

action to the cumulative impact is negligible when compared with non-OCS oil- and gas-related impacts.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 Supplemental EIS 

A search of Internet information sources (e.g., NOAA’s Gulf Spill Restoration Publications website, 

NOAA’s Environmental Response Management Application [ERMA] Gulf Response website, NOAA’s 

Deepwater Horizon Archive Publications and Factsheets, the Gulf of Mexico Sea Grant Deepwater 

Horizon Oil Spill Research and Monitoring Activities Database, RestoreTheGulf.gov website, and the 

Deepwater Horizon Oil Spill Portal) and public search engines to search published journal articles, 

Federal documents, and research reports was conducted to determine the availability of recent information 

on topographic features. The search revealed new information on the affected environment that is 

pertinent to this Supplemental EIS.

For the Flower Gardens, BOEM has published a study in conjunction with the Flower Garden Banks

National Marine Sanctuary that monitored multiple species of vertebrates and invertebrates found on the 

topographic structures (Johnston et al., 2015). They found that the reefs are among the healthiest in the 

GOM with relatively high coral cover but relatively low species diversity. They also state that the reefs 

have maintained this status throughout a time period when OCS oil and gas development has occurred in 

nearby blocks, suggesting that the Topographic Features Stipulation does successfully mitigate against 

impacts due to routine activities and accidental events.

The most relevant information for this Supplemental EIS was the publication of data related to the 

apparent mixing of surface waters to a depth similar to that of the topographic features during the passage 

of Tropical Storm Bonnie in July 2010 (Silva et al., 2015). This mixing resulted in damages to the 

benthic community of mesophotic reefs due to surface oil on the water surface at the time. Many of these 

reefs have similar communities and are found at similar depths as most topographic features. As such, if 

a large storm event did occur in the Gulf and it passed over a topographic feature while there was a 

substantial amount of surface oil present, impacts to the benthic community would be expected. 
4-34 Central Planning Area Lease Sale 247 Supplemental EIS

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. Working in deep marine systems is complex and requires 

substantial resources, and as such, research on these features has been limited. Thus, there is a substantial 

amount of information that remains unknown about these features. All analyses discussed in this 

Supplemental EIS and in the prior 2012-2017 Gulf of Mexico EISs are based on incomplete information. 

Because topographic features are not unique to the CPA, information collected throughout the GOM has 

been used in this analysis. For example, our understanding of the possible impacts of surface oil spills to 

topographic features in the GOM was determined by combining research on the depth and concentration 

of physical mixing of surface oil with the known depths of CPA topographic features. These results 

suggest that, although oil measurements were not collected at every feature under every condition, 

topographic features exist at depths deeper than lethal concentrations of oil would be expected (Lange, 

1985; McAuliffe et al., 1975 and 1981a; Tkalich and Chan, 2002; Rezak et al., 1983; Wyers et al., 1986) 

unless dispersants are used. Additionally, continuous monitoring of the Flower Garden Banks since the 

1970’s for impacts related to OCS development suggests that BOEM’s topographic features stipulations

may achieve the stated objective of minimizing damage to topographic features from OCS oil- and gasrelated activities (refer to Johnston et al., 2013, and references therein). At the Flower Garden Banks, 

corals have flourished while OCS development has occurred, and in some cases, activities have taken 

place just outside the mitigation zone. Since corals are generally considered to be more fragile than most 

other organisms found in the CPA, it is reasonable to conclude that topographic features in the CPA with 

more resilient organisms than the Flower Garden Banks have not negatively impacted other topographic 

structures in the GOM.

With respect to unavailable information in relation to the Deepwater Horizon explosion, oil spill, and 

response, the majority of this information cannot be obtained because it has not been released. Relevant 

data on the status of topographic features may take years to acquire and analyze. This unavailable 

information may be relevant to adverse effects because the Deepwater Horizon explosion, oil spill, and 

response may have caused changes to baseline conditions for topographic features in the Gulf of Mexico. 

While outstanding reports are not expected to reveal reasonable foreseeably significant effects, BOEM 

nonetheless determined that additional information could not be timely acquired and incorporated within 

the timeline contemplated in the NEPA analysis of this Supplemental EIS. For example, if sampling 

techniques show that oil concentration were greater at Sackett Bank in the CPA (Sammarco, 2013), then it 

is possible that more oil reached other topographic features in the CPA than previously reported. 

Additionally, the conclusions by Felder et al. (2014) and Fredericq et al. (2014) do suggest that changes in 

the benthic communities coincided with the Deepwater Horizon oil spill; however, more information is 

required to conclude that this is the result of the oil spill, the result of larger ecological processes, or a 

combination of both. Until this information is collected, analyzed, and made available, it is impossible to 

make these determinations.

BOEM used existing information and reasonably accepted scientific methodologies to extrapolate 

from available information in completing this analysis and formulating the conclusions presented here. 

Although the body of available information is incomplete, the evidence currently available supports past 

analyses and does not indicate severe adverse impacts to topographic features. Therefore, BOEM has 

determined that the incomplete or unavailable information is not essential to a reasoned choice among 

alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for topographic features presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information provided above. No new significant information was 

discovered that would alter the impact conclusion for topographic features presented in those NEPA

documents because of the available scientifically credible evidence in this analysis and based upon 

accepted scientific methods and approaches. The analysis of potential impacts discussed in those 

documents still applies for the proposed CPA Lease Sale 247. It is concluded that the CPA proposed 

action would have a negligible or minor impact on the topographic features of the CPA. 
Description of the Environment and Impact Analysis 4-35

4.1.1.8. Sargassum Communities

BOEM has reexamined the analysis for Sargassum communities presented in the prior 2012-2017 

Gulf of Mexico EISs based on the additional information presented below. No new significant 

information was discovered that would alter the impact conclusion for Sargassum and Sargassum

communities presented in those NEPA documents. The analysis and potential impacts discussed in those 

documents still apply for proposed CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.8 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.8 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.8 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Sargassum is one of the most ecologically important brown algal genera found in the pelagic 

environment of tropical and subtropical regions of the world. The pelagic complex in the GOM is mainly 

comprised of S. natans and S. fluitans (Lee and Moser, 1998; Stoner, 1983; Littler and Littler, 2000). 

Both species of Sargassum live immediately below the water surface and are fully adapted to a pelagic 

existence (Lee and Moser, 1998). These floating plants may be up to a few meters in length and may be 

found floating alone or in larger rafts or mats that support communities of fish and a variety of other 

marine organisms. The distribution, size, and abundance of Sargassum mats varies depending on 

environmental and physiochemical factors such as temperature, salinity, and dissolved oxygen. 

Impacts of Routine Activities and Accidental Events

Impact-producing factors associated with routine activities for the CPA proposed action that could 

affect Sargassum communities may include the following: (1) drilling discharges (i.e., muds and 

cuttings); (2) produced water and well treatment chemicals; (3) operational discharges (i.e., deck 

drainage, sanitary and domestic water, and bilge and ballast water); and (4) physical disturbance from 

vessel traffic and the presence of exploration and production structures (i.e., rigs, platforms, and 

MODUs). Considering Sargassum’s widespread distribution and occurrence in the upper water column 

near the sea surface, it may be contacted by routine discharges from oil and gas operations; however, the 

quantity and volume of these discharges is relatively small compared with the surface area of pelagic 

waters of the CPA (268,922 km2

; 103,831 mi2). Therefore, contact through routine activities would only 

occur for a small portion of the Sargassum population and associated communities. Because these 

discharges are highly regulated to control toxicity and because they would continue to be diluted in the 

Gulf water, reducing concentrations of any toxic component, produced-water impacts on Sargassum 

communities would be minimal. 

The impingement by service vessels, working platforms, and drillships would contact only a very 

small portion of the Sargassum population. For algae coming in contact with OCS oil- and gas-related 

equipment, most should remain unharmed as they are pushed out of the way, but a small percentage of 

algae may be physically destroyed via propellers or stranded and subsequently become desiccated. For 

animals, the smaller organisms could be stranded with the algae or be destroyed by the equipment. 

Larger animals that often associate with Sargassum could avoid contact with most equipment. Because 

the distribution of Sargassum is dependent on many factors, the result is that the distribution is 

unpredictable and haphazard. As such, impacts to Sargassum communities associated with the CPA 

proposed action are expected to have a negligible or minor effect on the small portion of the Sargassum

community that could be contacted. Additionally, Sargassum and many of the associated species have 

adapted a rapid growing lifestyle to allow for rapid recovery from negative impacts. No measurable 

impacts are expected to the overall population of the Sargassum community. 

Potential impact-producing factors associated with accidental events for the CPA proposed action that 

could affect Sargassum and its associated communities include (1) spills (i.e., surface oil and fuel spills), 

(2) spill-response activities, and (3) chemical spills. These impacting factors would have varied effects 

depending on the intensity of the spill and the presence of Sargassum in the area of the spill. All types of 

spills, including surface oil and fuel spills and chemical spills, could potentially contact Sargassum 
4-36 Central Planning Area Lease Sale 247 Supplemental EIS

communities. The quantity and volume of most of these spills would be relatively small compared with 

the surface waters of the CPA (268,922 km2

; 103,831 mi2). Therefore, most spills would only contact a 

small portion of the Sargassum complex. Accidental spills would be diluted by Gulf water and, therefore, 

concentrations of toxic components that could potentially contaminate or kill Sargassum tissues or the 

associated community would also be reduced in this scenario. Any Sargassum that did come in contact 

with large concentrations of oil would eventually sink and advect oil bound to the algae to the seafloor. 

Presumably, any vessel contact during response activities to Sargassum would be to capture algae that are 

dead or dying due to contact with oil released during a spill; as such, response vessels would not impact 

the algae more than they are already impacted by the oil. The impacts to Sargassum associated with the

CPA proposed action are expected to have only minor effects to a small portion of the Sargassum

community. In the case of a very large spill, the consequences would be death of a large number of algae 

across a geographically large area in the northern Gulf of Mexico. However, the Sargassum community 

complex lives in pelagic waters with generally high water quality and is expected to show good resilience 

to the predicted effects of spills. It has a yearly growth cycle that promotes quick recovery from impacts 

and that would be expected to restore typical population levels in 1-2 growing seasons. For information 

on the impacts resulting from events outside the scope of routine activities and accidental events, refer to 

Appendix B. 

Cumulative Impacts 

Cumulative impacts from OCS oil- and gas-related operations include effects resulting from the CPA 

proposed action, as well as those resulting from past and future OCS leasing. These operations include 

drilling discharges, produced water and well treatment chemicals, operational discharges, accidental 

spills, and physical disturbance from OCS oil- and gas-related vessels and structures. Potential non-OCS 

oil- and gas-related factors include hurricanes, water quality, and non-OCS oil- and gas-related vessel 

traffic.

The OCS oil- and gas-related vessels transiting the GOM pass through Sargassum mats, producing 

slight impacts to the Sargassum community by breaking up clumps/mats or physically destroying the 

algae. Turbulence from wakes and direct damage from propellers on vessels servicing OCS oil- and gasrelated activities could affect Sargassum by breaking up mats or destroying strands. However, the 

amount of damage that vessels could inflict on a Sargassum mat would be minimized because of 

Sargassum’s temporary and seasonal nature. When present, Sargassum mats are naturally loose knit with 

the ability to break apart and re-form. Any vessel-related damage would likely be seen in the community 

of organisms inhabiting these mats, which may be killed when being struck by a vessel. Sea turtles and 

small fishes that reside in (rather than below) Sargassum mats would be most susceptible to this type of 

damage. However, the footprint of any vessel in the CPA is small compared with the distribution of 

Sargassum, and its transitory life history minimizes the possibility that any mat or the inhabitants are 

routinely affected. None of these would have more than minor localized effects to the affected mats as 

these mats routinely break up and move across extensive areas. The OCS oil- and gas-related structures 

can alter the movement of Sargassum mats and entrap small quantities of the algae. Because the CPA 

proposed action is not expected to substantially increase (if any) the number of OCS oil- and gas-related 

vessels, it is likely that OCS oil- and gas-related activities will only have a minimum and local effect on 

the Sargassum community. 

Accidental spills could contribute to the cumulative impacts of OCS oil- and gas-related activities if 

an accidental spill was exceptionally large, located in the “nursery” area where Sargassum resides in the 

western GOM, and was during a time of the year when the standing stock is restricted to the “nursery” 

area (e.g., late winter and spring) (Gower and King, 2011). The probability of this happening temporally 

and spatially is extremely low (refer to Appendix B). Given the life history of Sargassum, recovery of 

the algae could occur relatively rapidly; however, during the recovery period, animals that rely on 

Sargassum to move around the Gulf or use Sargassum for refuge would be severely impacted due to the 

loss of habitat or a method of transportation. Cumulative impacts would be most pronounced for animals 

that rely exclusively on Sargassum and have low reproduction rates or have larvae that only disperse 

locally. Any noncatastrophic spill would likely only result in localized and short-term adverse impacts 

that would contribute little to the overall cumulative effect of the CPA proposed action. 

Potential non-OCS oil- and gas-related factors include hurricanes, water quality, and non-OCS oiland gas-related vessel traffic. Hurricanes are major natural sources of impacts that affect Sargassum. 
Description of the Environment and Impact Analysis 4-37

The energy associated with these storms can break up mats, destroy strands, and displace animals; 

however, the life history and the widespread distribution of Sargassum communities minimize the 

probability that any given storm will have any lasting population-level effects. Violent surface turbulence 

caused by these storms would dislocate many of the organisms living on and in the Sargassum. Some of 

the organisms (those that cannot swim or swim only weakly) such as nudibranchs (sea slugs), shrimp, 

Sargassum fish (Histrio histrio), and pipefish (Syngnathus spp.) would become separated from the algae. 

Without cover, many would fall prey to fish after a storm; others may sink to the seafloor and die. Some 

epifauna, such as hydroids, living on the algae may suffer physical damage or be broken off. Hurricanes 

can also drive Sargassum into waters less conducive for growth and can strand large quantities on 

beaches. In addition, Sargassum communities may be susceptible to nonpoint-source pollution from 

land-based runoffs carrying pollutants and excessive nutrients, especially in nearshore areas. The results 

could be a basinwide reduction in Sargassum biomass. Turbulence from wakes, direct damage from 

propellers, impingement on non-OCS oil- and gas-related vessels (i.e., commercial shipping, fishing 

activity, and pleasure boating) could also affect Sargassum by breaking up mats, destroying algae, or 

stranding algae. However, the amount of damage that vessels could inflict on a Sargassum mat would be 

minimized because of Sargassum’s transitory nature. Any vessel-related damage would likely be seen in 

the community of organisms inhabiting these mats, which may be killed by being struck by a vessel. Sea 

turtles and small fishes that reside in (rather than below) Sargassum mats would be most susceptible to 

this type of damage. The incremental contribution of the CPA proposed action to the overall cumulative 

impacts on Sargassum communities that would result from the OCS Program, environmental factors, and 

non-OCS oil- and gas-related activities is expected to be minimal.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of Internet information sources (e.g., NOAA’s Gulf Spill Restoration Publications website 

and Environmental Response Management Application [ERMA] Gulf Response website, NOAA’s 

Deepwater Horizon Archive Publications and Factsheets, the Gulf of Mexico Sea Grant Deepwater 

Horizon Oil Spill Research and Monitoring Activities Database, RestoreTheGulf.gov website, and the 

Deepwater Horizon Oil Spill Portal) and public search engines to search published journal articles, 

Federal documents, and research reports was conducted to determine the availability of recent information 

on Sargassum communities. The search revealed new information on nursery areas for Sargassum, 

Sargassum’s suitability as habitat for other organisms, and impacts related to oil and dispersant exposure.

The primary publication relevant to this Supplemental EIS is the delineation of the Sargassum cycle 

(Frazier et al., 2015). Using a combination of satellite imaging and ground truthing, Frazier et al. (2015) 

determined that the life history of Sargassum in the GOM is part of a larger cycle that includes the midAtlantic Ocean and Caribbean Sea. 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 Gulf of Mexico via the Yucatan Peninsula. Once in the GOM, it moves into the 

western area where it feeds off the nutrient input from coastal rivers, including the Mississippi River. 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. 

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 round, the rapid growth of 

Sargassum populations in the western Gulf of Mexico typically occur during the spring/summer of the 

year (Gower et al., 2006, Gower and King, 2008 and 2011). Estimates suggest that between 0.6 and 

6 million metric tons of Sargassum are present annually in the Gulf of Mexico, with an additional 

100 million metric tons exported to the Atlantic basin (Gower and King, 2008 and 2011; Gower et al., 

2013). Sargassum deposition on GOM 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). 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.
4-38 Central Planning Area Lease Sale 247 Supplemental EIS

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplemental EIS and in Chapter 4.2.1.8 of 

the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231Supplemental EIS and Chapter 4.1.1.8 

of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS, BOEM 

has identified unavailable information regarding Sargassum and Sargassum communities in the CPA. 

This incomplete or unavailable information includes information on the effects of in-situ oil exposure and 

the movement patterns of Sargassum. BOEM used existing information and reasonably accepted 

scientific methodologies to extrapolate in completing this analysis. BOEM has determined that there are 

few foreseeable significant adverse impacts to the Sargassum population associated with routine activities 

or accidental OCS oil- and gas-related events using publications such as Frazier et al. (2015), Gower and 

King (2011), Gower et al. (2013), and Powers et al. (2013). Gower and King (2011) and Gower et al. 

(2013) suggest that Sargassum is continually present in the west-central GOM and that it moves in a 

general west to east pattern during the growing season; however, movements at a finer temporal or spatial 

scale are more difficult to predict. Frazier et al. (2015) expanded on the work by Gower and King (2011) 

to further delineate the life cycle of Sargassum. Although the large rafts identified by Gower and King 

(2011) were prevalent during the warmer months in the GOM, Frazier et al. (2015) found that Sargassum

was continuously moving through cycle. Liu et al. (2014) noted that the toxicity or the presence of oil 

across the surface waters of the GOM was also variable at any given time, suggesting that it is difficult to 

predict the effects of coming in contact with surface oil. Additionally, Lindo-Atichati (2012) suggested 

that patterns of larval fish in the surface currents in the northern GOM were not consistent spatially or 

temporally and that they were highly dependent on mesoscale current structures like the Loop Current and 

associated eddies. Combined, these studies suggest that, as Sargassum is passively moved in the surface 

waters, its presence at any given location or at any given time is difficult to predict, especially as the 

population grows exponentially during the growing season. Powers et al. (2013) also suggest that there 

were adverse effects to Sargassum under the proper conditions, but the spatial or temporal extent of those 

effects remain unknown. It is expected that for routine activities or accidental events the probability of 

enough Sargassum coming in contact with oil and dying as a result of this contact are low given that oil 

and Sargassum are each controlled by surface currents in differential manners. Ultimately, the 

cosmopolitan nature across the northern GOM and the reproductive capabilities of Sargassum provide a 

life history that is resilient towards localized or short-term deleterious effects, such as those expected to 

be associated with routine OCS oil- and gas-related activities and noncatastrophic oil or chemical spills. 

Therefore, BOEM has determined that the incomplete information on Sargassum is not essential to a 

reasoned choice among alternatives and that the information used in lieu of the missing information is 

acceptable for this analysis.

BOEM recognizes that the incomplete information, with respect to possible impacts to Sargassum in 

the CPA as a result of the Deepwater Horizon explosion, oil spill, and response, may be relevant to the 

evaluation of impacts. Because of this, BOEM’s subject-matter experts have used available scientifically 

credible evidence in this analysis and applied it using accepted scientific methods and approaches to 

extrapolate in completing this analysis. Sargassum communities within the CPA were affected by the 

Deepwater Horizon explosion, oil spill, and response; however, because the spill did not occur near an 

area where Sargassum persists year round, abundance recovered rapidly. Powers et al. (2013) 

documented a four-fold increase in Sargassum in the north-central GOM in the years following the spill. 

Additional information related to other possible adverse impacts of the Deepwater Horizon explosion, oil 

spill, and response to Sargassum communities in the CPA cannot be obtained during the timeline 

contemplated in the NEPA analysis of this Supplemental EIS because data related to research and 

monitoring related to the Deepwater Horizon explosion, oil spill, and response has yet to be completed 

and made publicly available. Therefore, BOEM has determined that the information is not essential to a 

reasoned choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for Sargassum communities presented in the prior 2012-2017 

Gulf of Mexico EISs based on the additional information presented above. No new significant 
Description of the Environment and Impact Analysis 4-39

information was discovered that would alter the impact conclusion for Sargassum communities presented 

in those NEPA documents because of the available scientifically credible evidence in this analysis and 

based upon accepted scientific methods and approaches. The analysis and potential impacts discussed in 

those documents still apply for proposed CPA Lease Sale 247. 

4.1.1.9. Chemosynthetic Deepwater Benthic Communities

BOEM has reexamined the analysis for chemosynthetic deepwater benthic communities presented in 

the prior 2012-2017 Gulf of Mexico EISs based on the additional information presented below. No new 

significant information was discovered that would alter the impact conclusion for chemosynthetic 

deepwater benthic communities presented in those previous NEPA documents. The analysis and potential 

impacts discussed in those documents still apply for proposed CPA Lease Sale 247.

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.9 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.9 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.9 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors on chemosynthetic deepwater benthic communities of 

the CPA are bottom-disturbing activities associated with anchoring, structure emplacement, pipelaying, 

structure removal, and discharges of drill cuttings, muds, and produced water. The application of 

avoidance criteria for chemosynthetic communities provided as guidance in NTL 2009-G40, “Deepwater

Benthic Communities,” typically precludes the placement of a well within 2,000 ft (610 m) of any 

suspected site of a chemosynthetic community. Considerable mechanical damage could be inflicted upon 

deepwater chemosynthetic communities by routine OCS oil- and gas-related drilling activities associated 

with the CPA proposed action if mitigations are not applied to permits. 

Bottom-disturbing activities associated with anchoring, structure emplacement, pipelaying, and 

structure removal cause localized bottom disturbances and disruption of benthic communities in the 

immediate area. Routine discharge of drill cuttings with associated muds can also affect the seafloor. 

Without mitigating measures, these activities could result in smothering by the suspension of sediments or 

the crushing of organisms residing in these communities. The risk of these physical impacts is greatly 

reduced by requiring the avoidance of potential chemosynthetic communities. Discharges of produced 

waters on the sea surface, chemical spills, and deck runoff would be diluted in surface waters, having no 

effect on seafloor habitats. Impacts from bottom-disturbing activities directly on chemosynthetic 

communities are expected to be extremely rare because of the application of required protective measures 

as provided as guidance by NTL 2009-G40. Information included in required hazards surveys for OCS 

oil- and gas-related activities depicts areas that could potentially harbor chemosynthetic communities. 

This allows BOEM to require avoidance of any areas that are conducive to chemosynthetic growth. If a 

high-density community is subjected to direct impacts by bottom-disturbing activities, potentially severe 

or catastrophic impacts could occur due to raking of the sea bottom by anchors and anchor chains, and 

partial or complete burial by muds and cuttings. The severity of such an impact is such that there would 

be incremental losses of productivity, reproduction, community relationships, and overall ecological 

functions of the local community, and incremental damage to ecological relationships with the 

surrounding benthos. 

Routine activities of the CPA proposed action are expected to cause no damage to the ecological 

function or biological productivity of chemosynthetic communities. Widely scattered, high-density 

chemosynthetic communities would not be expected to experience impacts from routine OCS oil- and 

gas-related activities in deep water because the impacts would be limited by the required avoidance 

criteria. Impacts on chemosynthetic communities from routine activities associated with the CPA 

proposed action would be minimal to none. 
4-40 Central Planning Area Lease Sale 247 Supplemental EIS

Accidental disturbances from the CPA proposed action, including subsea oil spills, have the potential 

to result in impacts on chemosynthetic communities of the CPA. Accidental events that could impact 

chemosynthetic communities are primarily limited to seafloor loss of well control. A loss of well control 

event at the seafloor could create a crater and could resuspend and disperse large quantities of bottom 

sediments. Chemosynthetic communities could be susceptible to physical impacts, including smothering, 

from a loss of well control event depending on bottom-current conditions. The avoidance criteria 

described above reduces the risk of these physical impacts by requiring a buffer of 2,000 ft (610 m) from 

wells. The avoidance required would protect sensitive communities from heavy sedimentation, with only 

light sediment components able to reach the communities in small quantities. 

Studies indicate that periods as long as hundreds of years are required to reestablish a seep 

community once it has disappeared (depending on the community type) (Powell, 1995; Fisher, 1995). 

There is evidence that substantial impacts on these communities could permanently prevent 

reestablishment (Fisher, 1995), particularly if hard substrate required for recolonization is buried by 

resuspended sediments from a loss of well control. Because widely scattered, high-density 

chemosynthetic communities would typically be located at more than 2,000 ft (610 m) away from a loss 

of well control event due to mitigating measures, potential accidental impacts from the CPA proposed 

action are expected to cause little damage to ecological or biological function of these communities.

If dispersants are applied to an oil spill or if oil is ejected under high pressure, oil would mix into the 

water column, be carried by underwater currents, and eventually contact the seafloor in some form, either 

concentrated (near the source) or decayed (farther from the source), where it may impact patches of 

chemosynthetic community habitat in its path. As with sediments, the farther the dispersed oil travels, the 

more diluted the oil will become as it mixes with surrounding water. 

There is some reason to believe the presence of oil would have only limited effects on 

chemosynthetic organisms because these communities live among oil and gas seeps; however, natural 

seepage is very constant and at very low rates as compared with the potential volume of oil released from 

a loss of well control or pipeline rupture. In addition, organisms inhabit certain niches within the 

gradients found at oil seeps, choosing locations with enough hydrocarbons to sustain their metabolism but 

not enough to be toxic. All seep organisms also require unrestricted access to oxygenated water at the 

same time as exposure to hydrocarbon energy sources. Oil plumes that contact the seafloor before they 

degrade could potentially affect sensitive benthic communities if they happen to encounter such a habitat 

in a localized area. The coating of organisms with oil could cause mortality or sublethal effects.

Accidental impacts associated with the CPA proposed action would likely result in only minimal 

impacts to chemosynthetic communities with adherence to the distancing guidance provided in NTL 

2009-G40. 

Cumulative Impacts 

Cumulative factors considered to impact the chemosynthetic communities of the Gulf of Mexico 

include both OCS oil- and gas-related and non-OCS oil- and gas-related activities. Cumulative OCS oiland gas-related impacts to deepwater communities in the Gulf of Mexico are considered negligible 

because of the application of distancing mitigations applied to permits. The most serious, impactproducing factor threatening chemosynthetic communities is physical disturbance of the seafloor, which 

could destroy the organisms of these communities. Such disturbance would most likely come from those 

OCS oil- and gas-related activities associated with pipelaying, anchoring, structure emplacement, and 

seafloor loss of well control events. Drilling discharges and resuspended sediments have a potential to 

cause minor, mostly sublethal impacts to chemosynthetic communities, but substantial sediment 

accumulations could result in more serious impacts. Possible catastrophic oil spills (Appendix B) due to 

seafloor loss of well control have the potential to devastate localized deepwater benthic habitats. This 

could occur in the case of a low-probability catastrophic spill combined with the application of dispersant

or high-pressure ejection of oil, producing the potential to cause devastating effects on local patches of 

habitat in the path of subsea plumes where they physically contact the seafloor. The possible impacts, 

however, will be localized due to the directional movement of oil plumes by the water currents and 

because the sensitive habitats have a scattered, patchy distribution. Oil plumes that remain in the water 

column for longer periods would disperse and decay, having only minimal effect. However, these events 

are rare and would only affect a small portion of the sensitive benthic habitat in the Gulf of Mexico. 
Description of the Environment and Impact Analysis 4-41

The non-OCS oil- and gas-related, impact-producing factors include activities such as commercial 

fishing, trawling, storm impacts, and climate change. As with deepwater coral communities (Hourigan, 

2014), fishing and trawling could potentially crush, topple, and remove chemosynthetic communities in 

the path of the gear. Because of the water depths where chemosynthetic communities live (>300 m; 

984 ft) and because of the low density of potentially commercially valuable fishery species at these 

depths, these activities are not expected to substantially impact deepwater benthic communities. 

However, if trawling were to occur over a chemosynthetic community, the community may be devastated. 

Regionwide and global impacts from climate change, such as ocean acidification and temperature change, 

are not expected to have noticeable impacts to deepwater habitats in the immediate future, but they are a 

potential concern over the long term (Lunden et al., 2013 and 2014). Overall, non-OCS oil- and gasrelated activities are not expected to greatly impact chemosynthetic communities, and the incremental 

contribution of the CPA proposed action to cumulative impacts is expected to be negligible to minor due 

to the proposed mitigation. 

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS and 

CPA 241/247 and EPA 226 Supplemental EIS 

A broad Internet search for relevant new information and scientific journal articles made available 

since publication of the prior 2012-2017 Gulf of Mexico EISs was conducted using the Internet and 

interlibrary loan acquisition. 

Because research specific to chemosynthetic organisms is limited, it can be useful to consider 

research regarding impacts relevant to deepwater corals, especially those associated with seeps that can be 

included in the broader definition of a chemosynthetic community, such as Callogorgia delta. Such 

research is presented here as potentially relevant with the major caveat that experiments were not 

performed on chemosynthetic organisms themselves and results could be different. 

DeLeo et al. (2015) performed laboratory tests on the effects of (1) bulk oil-water mixtures, (2) wateraccommodated oil fractions, (3) the chemical dispersant COREXIT 9500A, and (4) a combination of 

hydrocarbons and dispersants on representative living samples of three species of northern GOM corals

(i.e., Paramuricea type B3, Callogorgia delta, and Leiopathes glaberrima) obtained in the field at depths 

of 500-1,100 m (1,640-3,609 ft). Samples were exposed for a 96-hour period. All species showed greater 

health declines in response to dispersant alone (2.3-3.4 fold) and to the oil-dispersant mixtures 

(1.1-4.4 fold) than in the oil only treatments, which did not result in mortality. C. delta, which is found in 

increased abundance near natural hydrocarbon seeps and may have some natural adaptation to short-term 

oil exposure, showed less severe health declines than the other two species in response to oil and 

oil/dispersant mixtures. It can be reasonably concluded that chemosynthetic organisms such as 

tubeworms and bivalves, which intentionally consume hydrocarbons, would possess similar adaptations 

to naturally occurring levels of oil. 

COREXIT 9500A was created with hopes of reducing its toxicity when compared with older 

formulations, but the DeLeo et al. study demonstrates continued toxic effects. Much is still unknown 

(DeLeo et al., 2015), including the extent to which laboratory conditions and concentrations are 

analogous to likely field conditions, and these results may not be applicable to all deepwater coral species 

or to all chemosynthetic organisms. However, given the clear results in the study, the authors advise 

caution regarding application of chemical dispersants at depth, where dispersants and dispersant/oil 

mixtures could remain in contact with coral or chemosynthetic organisms for long periods of time and 

seem likely to induce greater impacts than oil exposure alone.

This study provides important information regarding the application of chemical dispersants at depth, 

as was performed during the Deepwater Horizon oil-spill response. However, that method of application 

was unprecedented and likely unique to a catastrophic level spill. For the types of small, noncatastrophic 

accidental spill events that are reasonably foreseeable with the CPA proposed action, the use of 

dispersants at depth is not anticipated. Moreover, the results of experiments on deepwater coral may not 

apply to chemosynthetic organisms. Therefore, this new research does not alter the previous impact level 

conclusions of the prior 2012-2017 Gulf of Mexico EISs. 

In another study, Valentine et al. (2014) found evidence of an area of approximately 3,200 km2 

(1,236 mi2

) around the Macondo well contaminated by ~1,800 kg (±1,000 kg) (~3,968 lb [±2,205 lb]) of 

excess hopane (a tracer for crude oil), reflecting deposition of oil from the Deepwater Horizon explosion 
4-42 Central Planning Area Lease Sale 247 Supplemental EIS

and oil spill. Based on maps of the contaminated area presented by Valentine et al., compared with the 

Bureau of Ocean Energy Management’s GIS database, it appears likely that some chemosynthetic 

communities may have been within the contamination footprint, although damage to chemosynthetic 

communities in the vicinity of the Macondo well has not been reported to date (Shedd, official 

communication, 2015). This study provides evidence that there could have been impacts to 

chemosynthetic communities that have yet to be documented, but this does not change the conclusions of 

the prior 2012-2017 Gulf of Mexico EISs. 

Our search did not reveal any other relevant new studies that would impact the analyses or 

conclusions of the prior 2012-2017 Gulf of Mexico EISs.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in those NEPA documents, there remains 

incomplete or unavailable information on the effects of the Deepwater Horizon explosion, oil spill, and 

response on chemosynthetic communities that could potentially be relevant to reasonably foreseeable 

significant adverse impacts. Ongoing research projects funded by NOAA and the National Science 

Foundation are investigating these impacts. Some of this information cannot reasonably be obtained 

because the long-term effects may not yet be detectable and the means to obtain it are unknown. This 

unavailable information may be relevant to adverse effects because it could provide an example of 

adverse impacts directly caused by a loss of well control event.

Existing information suggests that chemosynthetic communities did not experience significant 

adverse impacts from the Deepwater Horizon explosion, oil spill, and response. Numerous cruises using 

research ships, submersibles, and drift cameras investigated the seafloor in the area surrounding the well 

site (USDOC, NOAA, 2011a and 2011b). As detailed above, damage to chemosynthetic communities in 

the vicinity of the Macondo well has not been reported to date (Shedd, official communication, 2015). 

Therefore, it has not been demonstrated that even a catastrophic oil spill would have significant adverse 

impacts or change the baseline for chemosynthetic communities in the Gulf of Mexico. Even if this 

incomplete or unavailable information becomes available and ultimately demonstrates that such 

communities in the vicinity of the Macondo well have been severely impacted by the Deepwater Horizon

explosion, oil spill, and response, BOEM has determined that the information is not essential to a 

reasoned choice among alternatives. Even if some impacts did occur, chemosynthetic communities are 

found throughout the Gulf and are in patchy distributions, thus minimizing the proportion that would be 

likely to be impacted by any single event.

BOEM has also identified incomplete or unavailable information regarding the abundance and 

distribution of chemosynthetic communities in the GOM. Current understanding of the relationship 

between reflectivity of the seafloor and occurrence of potential habitat for chemosynthetic communities is 

used by BOEM to assess whether such communities occur in the vicinity of proposed OCS oil- and gasrelated activities. Similarly, side-scan sonar data are also used to determine the presence of likely habitat. 

These and other data are used to implement distance requirements to protect these communities. 

Incomplete or unavailable information could change our understanding of what signatures from such data 

sources indicate. Development of improved data or methods could help in determining where 

chemosynthetic communities occur. Such information could be used by BOEM to reduce impacts to 

these communities. Available scientifically credible information has been applied by BOEM’s subjectmatter experts using accepted scientific methodologies. The confirmed presence of chemosynthetic 

communities in areas predicted to have likely habitat via reflectivity or side-scan sonar data indicates that 

BOEM is currently able to effectively protect these communities from OCS oil- and gas-related activities. 

Therefore, BOEM has determined that the information is not essential to a reasoned choice among 

alternatives because existing information has shown that current methods provide for an appropriate 

means for protecting these communities.

Summary and Conclusion

BOEM has reexamined the analysis for chemosynthetic communities presented in the prior 2012-

2017 Gulf of Mexico EISs based on the additional information presented above. No new significant 
Description of the Environment and Impact Analysis 4-43

information was discovered that would alter the impact conclusions for chemosynthetic communities 

presented in those NEPA documents. The analysis and potential impacts detailed in those documents still 

apply for proposed CPA Lease Sale247. 

4.1.1.10. Nonchemosynthetic Deepwater Benthic Communities

BOEM has reexamined the analysis for nonchemosynthetic deepwater benthic communities (also 

termed “deepwater coral communities”) presented in the prior 2012-2017 Gulf of Mexico EISs based on 

the additional information presented below. No new significant information was discovered that would 

alter the impact conclusion for nonchemosynthetic deepwater benthic communities presented in those 

NEPA documents. The analysis and potential impacts discussed in those documents still apply for 

proposed CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.10 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.10 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.10 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors on nonchemosynthetic deepwater benthic 

communities of the CPA are bottom-disturbing activities associated with anchoring, structure 

emplacement, pipelaying, structure removal, and discharges of drill cuttings, muds, and produced water. 

The application of avoidance criteria for deepwater benthic communities provided as guidance in NTL 

2009-G40, “Deepwater Benthic Communities,” typically precludes the placement of a well within 610 m 

(2,000 ft) of any suspected site of a deepwater benthic community. Considerable mechanical damage 

could be inflicted upon sensitive nonchemosynthetic deepwater benthic communities by routine OCS 

drilling activities associated with the CPA proposed action if mitigations are not applied to permits. 

Deepwater live bottom communities, primarily structured by the coral Lophelia pertusa, are the 

nonchemosynthetic deepwater benthic communities that would be sensitive to impacts from OCS oil- and 

gas-related activities.

Bottom-disturbing activities associated with anchoring, structure emplacement, pipelaying, and 

structure removal cause localized bottom disturbances and disruption of benthic communities in the 

immediate area. If a sensitive community is subjected to direct impacts by bottom-disturbing activities, 

potentially severe or catastrophic impacts could occur due to raking of the sea bottom by anchors and 

anchor chains and partial or complete burial by muds and cuttings. The severity of such an impact is such 

that there would be incremental losses of productivity, reproduction, community relationships, and overall 

ecological functions of the local community, and incremental damage to ecological relationships with the 

surrounding benthos. Should this occur, it could result in recovery times on the order of decades or more 

with the possibility of the community never recovering (Food and Agriculture Organization of the United 

Nations, 2008; Jones, 1992; Probert et al., 1997). However, impacts from bottom-disturbing activities 

directly on deepwater coral communities are expected to be rare because of the application of required 

protective measures as guidance provided in NTL 2009-G40, “Deepwater Benthic Communities.”

Routine discharge of drill cuttings with associated muds can also affect the seafloor. In deep water, 

as opposed to shallower areas on the continental shelf, discharges of drilling fluids and cuttings at the sea 

surface are spread across broad areas of the seafloor and are generally distributed in thinner 

accumulations. A deepwater effects study funded by this Agency included determinations of the extent of 

muds and cuttings accumulations in approximately 1,000 m (3,281 ft) of water (CSA, 2006). 

Geophysical and chemical measurements indicated that a layer of cuttings and muds several centimeters 

thick was deposited within a 500-m (1,640-ft) radius of well sites. This suggests that the required 

2,000-ft (610-m) distance would protect deepwater benthic communities from impacts. Discharges of 

produced waters on the sea surface, chemical spills, and deck runoff would be diluted in surface waters, 

having no effect on seafloor habitats.
4-44 Central Planning Area Lease Sale 247 Supplemental EIS

Routine activities associated with the CPA proposed action are not expected to cause damage to the 

ecological function or biological productivity of sensitive nonchemosynthetic deepwater benthic 

communities (deepwater coral reefs) due to the consistent application of BOEM’s protection guidance 

provided in NTL 2009-G40. Information included in required hazards surveys for OCS oil- and gasrelated activities depicts areas that could potentially harbor nonchemosynthetic communities. This allows 

BOEM to require avoidance of any areas that are conducive to the growth of sensitive hard bottom 

communities. The same geophysical conditions associated with the potential presence of chemosynthetic 

communities also results in the potential occurrence of hard carbonate substrate and other associated, 

nonchemosynthetic deepwater benthic communities. Because of the required avoidance criteria, these 

communities are generally avoided in exploration and development planning and in bottom-disturbing 

activities. Impacts on sensitive deepwater communities from routine activities associated with the CPA 

proposed action would be minimal to none. 

Accidental disturbances resulting from the CPA proposed action, including oil spills, have the 

potential to result in impacts to nonchemosynthetic deepwater benthic communities of the CPA. 

Accidental events that could impact nonchemosynthetic deepwater benthic communities are primarily 

limited to seafloor loss of well control. A loss of well control at the seafloor could create a crater and 

could resuspend and disperse large quantities of bottom sediments. This would destroy any organisms 

located nearby via burial or modification of narrow habitat quality requirements. Substantial impacts on 

these communities could permanently prevent reestablishment, particularly if hard substrate required for 

recolonization is buried by resuspended sediments from a loss of well control. Physical disturbance or 

destruction of a limited area of benthos or to a limited number of megafauna organisms (e.g., brittle stars, 

sea pens, and crabs) would not result in a major impact to the deepwater benthos ecosystem as a whole or 

even in relation to a small area of the seabed within a lease block. The application of avoidance criteria 

for deepwater coral communities as provided as guidance in NTL 2009-G40 precludes the placement of a 

well within 2,000 ft (610 m) of any suspected site of a deepwater coral community, therefore distancing 

the community from sedimentation resulting from a possible loss of well control event. 

Accidental impacts due to oil spills associated with the CPA proposed action would likely result in

only minimal impacts to nonchemosynthetic communities with adherence to the required avoidance 

measures. A loss of well control could result in a low-probability catastrophic spill (Appendix B), which 

is not part of the CPA proposed action and not likely expected to occur, but the distance requirements 

would tend to lessen but not necessarily eliminate the impacts. A large subsea spill combined with the 

application of dispersant or high-pressure ejection of oil could mix oil into the water column, resulting in 

a subsea plume. Such a plume could potentially cause devastating effects on local patches of habitat in its 

path where it physically contacts the seafloor. If such an event were to occur, it could take decades to 

reestablish the nonchemosynthetic community in that location. The possible impacts, however, would be 

localized due to the directional movement of an oil plume by the water currents and because the sensitive 

habitats have a scattered, patchy distribution. As with sediments, the farther the dispersed oil travels, the 

more diluted it would become as it mixes with the surrounding water, and bacteria would degrade the oil 

over time (and distance). Oil plumes that remain in the water column for longer periods would disperse 

and decay, having only a minimal effect. 

Cumulative Impacts 

Cumulative factors considered to impact the deepwater benthic communities (>300 m; 984 ft) of the 

Gulf of Mexico include both OCS oil- and gas-related and non-OCS oil- and gas-related activities. The 

OCS oil- and gas-related activities associated with pipelaying, anchoring, structure emplacement, drilling 

discharges, and seafloor loss of well control have the potential to impact nonchemosynthetic deepwater 

benthic communities. The most serious, impact-producing factor threatening nonchemosynthetic 

communities is physical disturbance of the seafloor, which could destroy the organisms of these 

communities. Such disturbance would most likely come from those OCS oil- and gas-related activities 

associated with pipelaying, anchoring, and structure emplacement. Anchoring and pipeline and structure 

emplacement have the potential to crush deepwater benthic communities. Drilling discharges and 

resuspended sediments have the potential to cause minor, mostly sublethal impacts to nonchemosynthetic 

communities, but substantial accumulations could result in more serious impacts. Possible effects of an 

oil spill could range from no discernible effect (for well-dispersed oil undergoing biodegradation), 

reduced growth, interruption of reproductive cycles, loss of gamete viability, tissue damage, and death of 
Description of the Environment and Impact Analysis 4-45

affected organisms to a reduction in the distribution of species, depending on the amount and duration of 

contamination. Major impacts to localized benthic habitat are possible in the event of a low-probability 

catastrophic loss of well control on the seafloor (refer to Appendix B for more details). However, a lowprobability catastrophic spill is not part of the CPA proposed action and not likely expected to occur. 

Therefore, cumulative impacts to deepwater communities in the Gulf of Mexico are considered negligible 

because of the application of the avoidance criteria described in NTL 2009-G40 that distances bottomdisturbing activities from sensitive habitats.

Non-OCS oil- and gas-related activities include commercial fishing and trawling, storm impacts, and 

climate change. Among the activities unrelated to the OCS Program (non-OCS oil and gas impactproducing factors), fishing and trawling represent the greatest possible threat to nonchemosynthetic 

communities and associated fish communities as a result of habitat destruction and overfishing (Kaiser, 

2004). The impacts on deepwater fisheries in the GOM associated with deepwater coral habitat as a result 

of trawling activity are a serious concern (Hourigan, 2014), but because of the water depths (>300 m; 

984 ft) and the low density of potentially commercially valuable fishery species in areas associated with 

these communities, fishing and trawling are not expected to severely impact deepwater benthic 

communities. Regionwide and global impacts from climate change, such as ocean acidification and 

temperature change, are not expected to have noticeable impacts to deepwater habitats in the immediate 

future, but they are a concern over the long term (Lunden et al. 2013 and 2014). Storms cause little to no 

impacts at the depths (>300 m; 984 ft) that nonchemosynthetic communities occur. A storm could 

potentially cause some type of accident that could then cause secondary impacts, such as shipwrecks that 

could crush nonchemosynthetic communities, but such occurrences would be rare. State oil and gas 

activities are not expected to impact deepwater benthic communities due to the great distance between 

such activities and water depths of >300 m (984 ft). 

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search for relevant new information was conducted using the Internet and interlibrary loan 

acquisition of relevant publications. New information was found about the potential impacts from 

exposure to oil, chemical dispersants, and dispersant/oil mixtures. 

Valentine et al. (2014) found evidence of an area of approximately 3,200 km2 (1,236 mi2

) around the 

Macondo well contaminated by ~1,800 kg (±1,000 kg) (~3,968 lb [±2,205 lb]) of excess hopane (a tracer 

for crude oil), reflecting deposition of oil from the Deepwater Horizon explosion and oil spill. Based on 

maps of the contaminated area presented by Valentine et al., compared with the Bureau of Ocean Energy 

Management’s GIS database, it appears likely that some deepwater benthic communities may have been 

within the contamination footprint (Shedd, official communication, 2015). Following up on White et al.’s 

(2012) documentation of a deepwater coral community impacted by oil from the Deepwater Horizon oil 

spill, Fisher et al. (2014) described two additional deepwater coral communities with negative impacts 

attributed to the Deepwater Horizon oil spill, i.e., in Mississippi Canyon Block 297 (6 km [4 mi] south of 

the Macondo wellhead) and in Mississippi Canyon Block 344 (22 km [14 mi] southeast of the Macondo

wellhead). Numerous other deepwater coral communities investigated by Fisher et al. (2014) since the 

spill were found to be healthy. These studies provide evidence that there could have been impacts to 

deepwater benthic communities that have yet to be documented, but this does not change the conclusions 

of the prior 2012-2017 Gulf of Mexico EISs. 

DeLeo et al. (2015) performed laboratory tests on the effects of (1) bulk oil-water mixtures, (2) wateraccommodated oil fractions, (3) the chemical dispersant COREXIT 9500A, and (4) a combination of 

hydrocarbons and dispersants on representative living samples of three species of northern GOM corals

(i.e., Paramuricea type B3, Callogorgia delta, and Leiopathes glaberrima) obtained in the field at depths 

of 500-1,100 m (1,640-3,609 ft), exposing the samples for a 96-hour period. All species showed greater 

health declines in response to dispersant alone (2.3-3.4 fold) and to the oil-dispersant mixtures 

(1.1-4.4 fold) than in the oil only treatments, which did not result in mortality. C. delta, which is found in 

increased abundance near natural hydrocarbon seeps and may have some natural adaptation to short-term 

oil exposure, showed less severe health declines than the other two species in response to oil and 

oil/dispersant mixtures. Much is still unknown (DeLeo et al., 2015), including the extent to which 

laboratory conditions and concentrations are analogous to likely field conditions, and these results may 
4-46 Central Planning Area Lease Sale 247 Supplemental EIS

not be applicable to all deepwater coral species. However, given the clear results in the study, the authors 

advise caution regarding the application of chemical dispersants at depth, where dispersants and 

dispersant/oil mixtures could remain in contact with coral for long periods of time and seem likely to 

induce greater impacts than oil exposure alone.

This study provides important information that should inform future decisions regarding the 

application of chemical dispersants at depth, as was performed during the Deepwater Horizon oil-spill 

response. However, that method of application was unprecedented and likely unique to a catastrophic

level spill. For the types of small, noncatastrophic accidental spill events that are reasonably foreseeable 

in the CPA proposed action, the use of dispersants at depth is not anticipated. Therefore, this new 

research does not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplement EIS and in Chapter 4.2.1.10 of 

the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.10 

of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS, BOEM 

has identified incomplete or unavailable information for impacts related to the following: locations of 

deepwater corals in the Gulf of Mexico; toxicity of oil to deepwater corals; secondary impacts on 

associated deepwater fish communities; and impacts from the Deepwater Horizon explosion, oil spill, and 

response on nonchemosynthetic deepwater benthic communities that may be relevant to reasonably 

foreseeable significant adverse impacts.

At present, the best available information does not provide data for a complete understanding of these 

four data gaps. BOEM used reasonably accepted scientific methodologies to extrapolate from existing 

information in completing this analysis and formulating the conclusions presented here. BOEM’s 

database of known deepwater benthic communities is incomplete. This database is used when deepwater 

exploration and development plans are reviewed to ensure that deepwater corals are not impacted by OCS 

oil- and gas-related activities. In order to fill this data gap, BOEM’s subject-matter experts identify 

probable habitat for deepwater corals using a database of 3D seismic data, which provides the locations of 

28,000 features that could represent such communities, in conjunction with side-scan sonar data and sitespecific, high-resolution surveys to identify sensitive habitat and communities. BOEM’s database of 

3D seismic anomalies is well suited to the identification of general areas in which favorable coral habitat 

may occur and is sufficient in assisting BOEM in identifying areas that should be avoided for OCS oiland gas-related activities. However, these surveys may not be sufficiently high resolution for the 

identification of small, scattered hard substrate, as discussed by Quattrini et al. (2013) and as analyzed in 

the CPA 241/124 and EPA 226 Supplemental EIS. Small patches of shell and rubble substrate are 

commonly observed in soft bottom habitat near active and inactive seep sites, which frequently occur in 

areas targeted for OCS oil- and gas-related activities. If data are sparse or indicate additional detail is 

warranted, this data gap may be additionally filled by site-specific video or photographic surveys to 

obtain this information. Despite these procedures, some communities scattered throughout predominantly 

soft bottom habitat may still be impacted if seafloor surveys do not suggest deepwater coral habitat is 

present. However, BOEM has determined that the incomplete information is not essential to a reasoned 

choice among alternatives because BOEM reviews plans on a case-by-case basis to reduce the possibility 

of impacting deepwater coral habitat. 

Information on the toxic impacts of oil on deepwater corals is incomplete. A previous investigation 

of several deepwater octocorals and their association with oil seeps indicated that one species was found 

in association with oil seeps. The results of this study indicate that this coral could “possess mechanisms 

for dealing with natural levels of exposure to hydrocarbons” (Quattrini et al., 2013). The new research by 

DeLeo et al. (2015) corroborates this finding for one species (Callogorgia delta) commonly associated 

with seeps. Such an adaptation could result in resilience after exposure to oil from a loss of well control. 

It is possible that, if this coral may be tolerant of some oil exposure, other species may be as well; 

however, that information is not known at this time. BOEM has determined that the unavailable 

information on the tolerance of deepwater corals to oil exposure is not essential to a reasoned choice 

among alternatives because BOEM requires that OCS oil- and gas-related activities are sufficiently 

distanced from wells and because exposure from accidental events is unlikely.
Description of the Environment and Impact Analysis 4-47

Harm to nonchemosynthetic deepwater benthic communities as a result of bottom trawling is thought 

to present a serious threat (Hourigan, 2014). In place of unavailable information on commercial fishing 

impacts on deepwater fisheries in areas of deepwater coral habitat, existing information on commercial 

fishing activity in the deep GOM shows that, unlike other areas in the Atlantic Ocean and in Europe, 

bottom-fishing and trawling efforts in the deeper water of the CPA are currently minimal, and areas 

where royal red shrimp are trawled are in soft bottom communities (CSA, 2002). The primary Gulf of 

Mexico royal red shrimp trawling grounds are found in the upper continental slope off the Mississippi 

Delta (CSA, 2002). Grounds there are blue-black terrigenous silt and greenish mud, and any areas that 

fishermen know to be hard bottom (potential nonchemosynthetic communities) are not targeted because 

of the likelihood of lost/damaged trawling gear (CSA, 2002). The minimal fishery and minimal areal 

extent of potential nonchemosynthetic communities that are inside the outer boundaries of the fishery 

indicate that the footprint of the fishery would not likely overlap with the footprint of an impacted 

deepwater benthic community. Also, nonchemosynthetic communities are widely distributed in the Gulf 

of Mexico, mostly outside the narrowly distributed area of royal red shrimp grounds. Therefore, impacts 

on such communities as a whole are expected to be negligible. In conclusion, available information 

consistent with acceptable scientific reasoning shows that commercial fishing impacts on 

nonchemosynthetic deepwater benthic communities are expected to cause only negligible impacts.

BOEM has determined that the incomplete information is not essential to a reasoned choice among 

alternatives because nonchemosynthetic deepwater benthic communities are found throughout the Gulf of 

Mexico and are in patchy distributions, minimizing the number that would be likely to be impacted by 

any single event. Available scientifically credible information has been applied by BOEM’s subjectmatter experts using accepted scientific methodologies. Published information (White et al., 2012; Fisher 

et al., 2014) indicates that, even though multiple coral communities in the vicinity of the Macondo well 

were impacted by oil from the Deepwater Horizon oil spill, the impact to the overall population of coral 

communities of the GOM was relatively minor.

Summary and Conclusion

BOEM has reexamined the analysis for nonchemosynthetic deepwater benthic communities presented 

in the prior 2012-2017 Gulf of Mexico EISs based on the additional information presented above. The 

potential for effects from changes to the affected environment (post-Deepwater Horizon), routine 

activities, accidental spills (including low-probability catastrophic spills), and cumulative impacts remains 

whether or not the No Action or an Action alternative is chosen under this Supplemental EIS. Impacts on 

nonchemosynthetic deepwater benthic communities from either smaller accidental events or lowprobability catastrophic events will remain the same. No new significant information was discovered that 

would alter the impact conclusion for nonchemosynthetic communities presented in those NEPA

documents because of the available scientifically credible evidence in this analysis and based upon 

accepted scientific methods and approaches. The analysis and potential impacts discussed in those 

documents still apply for proposed CPA Lease Sale 247. 

4.1.1.11. Soft Bottom Benthic Communities

BOEM has reexamined the analysis for soft bottom benthic communities presented in the prior 2012-

2017 Gulf of Mexico EISs based on the additional information presented below. No new significant 

information was discovered that would alter the impact conclusion for soft bottom benthic communities 

presented in those NEPA documents. The analysis and potential impacts discussed in those documents 

still apply for proposed CPA Lease Sale 247. 

A detailed description of soft bottom benthic communities and the full analyses of the potential 

impacts of routine activities, accidental events, and cumulative impacts associated with the CPA proposed 

action are presented in Chapter 4.2.1.11 of the 2012-2017 WPA/CPA Multisale EIS. Updated 

information is provided in Chapter 4.2.1.11 of the WPA 233/CPA 231 Supplemental EIS and Chapter 

4.1.1.11 of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. 

The following information is a summary of the resource description and impact analysis incorporated 

from those NEPA documents. Any new information that has become available since those documents 

were published is presented below.
4-48 Central Planning Area Lease Sale 247 Supplemental EIS

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors include seafloor disturbances (e.g., anchoring, 

trenching, infrastructure emplacement, and infrastructure removal), waste discharge (e.g., drilling muds 

and cuttings from oil and gas operations), and resuspension of sediments (e.g., pipeline burial and 

decommissioning operations). Disturbances of soft bottom benthic communities cause localized 

disruptions to benthic community composition and an alteration in food sources for some large 

invertebrate and finfish species. Analysis of these routine activities has identified only localized and 

short-term impacts to soft bottom benthic communities. Any activity that may affect the soft bottom 

communities would only impact a small portion of the overall area of the seafloor of the Gulf of Mexico. 

Because the soft bottom substrate is ubiquitous throughout the Gulf of Mexico, there are no lease 

stipulations to avoid these communities; however, other routine practices restrict detrimental activities 

that could cause undue harm to benthic habitats (e.g., discharge restrictions, debris regulations, and 

NPDES permits).

Accidental disturbances to soft bottom benthic communities can result from oil spills associated with 

OCS oil- and gas-related activities. Because of the proportionately small area that OCS oil- and gasrelated activities occupy on the seafloor, only a very small portion of Gulf of Mexico soft bottom benthic 

communities would experience impacts as a result of oil spills. The greatest impacts would likely occur 

closest to the source of the spill, and impacts would rapidly decrease with increased distance from the 

source. Contact with spilled oil outside the vicinity of the event would likely cause sublethal to negligible 

effects to benthic invertebrates and finfishes. Oil deposited on soft bottom benthic communities could 

result in changes to local community structure. The organic enrichment of impacted sediments may result 

in altered sediment communities as bacteria degrade deposited organic matter. This response can lead to 

hypoxic conditions and a series of altered community structures until the organic matter is depleted and 

surface sediments return to an oxygenated state (Neff, 2005). Although an oil spill may have some 

detrimental impacts, especially closest to the occurrence of the spill, the impacts may be no greater than 

natural fluctuations (Clark, 1982), and impacts would affect a relatively small portion of the seafloor. 

Cumulative Impacts 

The cumulative analysis considers impacts resulting from ongoing routine oil and gas operations, as 

well as those resulting from past and future OCS leasing. These impacts include seafloor disturbances, 

waste discharge, and resuspension of sediments. Potential non-OCS oil- and gas-related disturbances 

include storms, sand mining, trawling, State oil and gas activities, and hypoxia. 

Although OCS oil- and gas-related activities may have locally devastating impacts, impacted 

communities are repopulated relatively quickly and the cumulative effect on the overall seafloor and 

benthic communities would be negligible. Long-term OCS oil- and gas-related activities are not expected 

to adversely impact the entire soft bottom environment of the GOM because the locally impacted areas 

are small in comparison with the entire area of the GOM. For information on impacts resulting from 

events outside the scope of routine activities and accidental events, refer to Appendix B. 

Non-OCS oil- and gas-related disturbances are likely to impact the soft bottom communities more 

frequently than do OCS oil- and gas-related activities. In some areas, soft bottom benthic communities 

remain in an early successional stage due to the frequency of natural and anthropogenic disturbances. 

The incremental contribution of the CPA proposed action to the cumulative impact is expected to be 

negligible.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

BOEM has examined newly available information for findings that may affect the analyses of routine 

activities, accidental events, and cumulative impacts of OCS oil- and gas-related activities and potentially 

alter previous conclusions. A search of Internet information sources and scientific journals was 

conducted to determine the availability of recent information (including ACS Publications, BioOne, 

EBSCO, Elsevier, the Gulf of Mexico Fishery Management Council’s website, JSTOR, NMFS’s 

databases, NOAA’s Gulf Spill Restoration Publications website, PLoS ONE, Science Direct, and 
Description of the Environment and Impact Analysis 4-49

SeaGrant website). This search revealed that new information relevant to an analysis of the potential 

impacts of OCS oil- and gas-related activities on soft bottom benthic communities has been published. 

New studies document that community structure of microbial, meiofaunal, and macrofaunal 

communities can be influenced by the presence of oil (Main et al., 2015; Baguley et al., 2015; Qu et al., 

2015). Main et al. (2015) found that deep-sea benthic microbial communities had increased oxygen 

consumption rates in response to hydrocarbon contamination. Bacterial biomass decreased, community 

structure changed in response to the contamination, and the data suggested a possible increase in 

hydrocarbon degraders. Baguley et al. (2015) studied meiofaunal deep-sea, soft-sediment community 

response to the Deepwater Horizon explosion and oil spill. They found that nematode dominance 

increased with proximity to the spill site and that copepod abundance decreased. Diversity and relative 

species abundance also decreased with proximity to the oil source. Qu et al. (2015) studied the 

community response of macrobenthos in sediments located from 5 to 9 km (3 to 6 mi) from the site of the 

Deepwater Horizon explosion and oil spill. Numbers of species, abundance, and diversity declined 

relative to pre-spill values, although the concentration of oil in the sediments remained low. Katsiaras 

et al. (2015) studied impacts to soft bottom macrofauna from dredged material disposal. High 

concentrations of hydrocarbons associated with the dredged material impacted the macrofaunal 

community, which was reflected in species number, abundance, and toxicity levels. Burial and 

smothering affected a diverse and abundant community, resulting in an almost azoic state. Similar 

impacts could be expected from the discharge of drilling muds and cuttings, although high concentrations 

of hydrocarbons are not common in such discharges. 

Based on the new information presented in this Supplement EIS and in the prior 2012-2017 Gulf of 

Mexico EISs’ analyses, which indicated that only a small portion of the GOM seafloor and associated 

benthic organisms would be impacted by oil exposure, BOEM concludes that population-level responses 

are not realistically expected.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the conclusions from the 

prior 2012-2017 Gulf of Mexico EISs are still valid because no new significant information on soft 

bottom benthic communities has been published since those NEPA documents were published; 

nevertheless, there is still incomplete or unavailable information, such as how the impacts of trawling 

affect soft bottom communities, how long it takes for recovery, and how the area impacted compares with 

that from OCS oil- and gas-related activities. As discussed in the prior 2012-2017 Gulf of Mexico EISs, 

BOEM has identified incomplete or unavailable information regarding soft bottom benthic communities. 

The cumulative impacts of OCS oil and gas exploration and development may result in locally 

significant impacts to soft bottom benthic communities. However, soft bottom communities are abundant 

throughout the GOM and the area of the seafloor impacted by OCS oil- and gas-related activities is very 

small in comparison with the overall area of soft bottom habitat in the GOM. Analysis of available 

information did not identify any reasonably foreseeable impacts extending beyond localized responses to 

oil contamination or sedimentation events among soft bottom inhabitants. Although additional 

information regarding impacts to soft bottom benthic communities and potential changes in baseline 

conditions may be in development, research to date does not suggest Gulfwide impacts should be 

expected. Relevant data regarding the status and function of soft bottom benthic communities directly 

impacted by OCS oil- and gas-related activity, including that being developed through the NRDA 

process, may take years to acquire and analyze and cannot be obtained within the timeline contemplated 

in the NEPA analysis of this Supplemental EIS. 

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing the analysis of impacts to soft bottom benthic communities and subsequent recovery. The 

new information summarized above indicates that microbial, meiofaunal, and macrofaunal soft bottom 

benthic communities transition rapidly when exposed to oil contamination of the sediment (Main et al., 

2015; Baguley et al., 2015; Qu et al., 2015; Katsiaras et al., 2015). Although the body of available 

information is incomplete and long-term effects cannot yet be known, the evidence currently available 

supports past analyses and does not indicate severe adverse impacts to the soft bottom benthic 

communities of the CPA or entire GOM as a result of OCS oil- and gas-related activities. Therefore, 

BOEM has determined that the incomplete information is not essential to a reasoned choice among 

alternatives.
4-50 Central Planning Area Lease Sale 247 Supplemental EIS

Summary and Conclusion

BOEM has reexamined the analysis for soft bottom benthic communities presented in the prior 2012-

2017 Gulf of Mexico EISs based on the additional information presented above. No new significant 

information was discovered that would alter the impact conclusion for soft bottom benthic communities 

presented in those NEPA documents because of the available scientifically credible evidence in this 

analysis and based upon accepted scientific methods and approaches. The analysis and potential impacts 

discussed in those documents still apply for proposed CPA Lease Sale 247.

4.1.1.12. Marine Mammals

BOEM has reexamined the analysis for marine mammals presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for marine mammals presented in those NEPA

documents. The analysis and potential impacts discussed in those documents still apply for proposed 

CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.12 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.12 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.12 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Operators must adhere to certain NTLs while conducting OCS oil- and gas-related activities in order 

to reduce impacts to marine mammals. The operator’s reaffirmed compliance with NTL 2012-JOINTG01 (“Vessel Strike Avoidance and Injured/Dead Protected Species Reporting”) and NTL 2015-BSEEG03 (“Marine Trash and Debris Awareness and Elimination”), as well as the limited scope, timing, and 

geographic location of the CPA proposed action, would result in negligible effects from the proposed 

drilling activities on marine mammals. In addition, NTL 2012-JOINT-G02, “Implementation of Seismic 

Survey Mitigation Measures and Protected Species Observer Program,” minimizes the potential of harm 

from seismic operations to marine mammals. These mitigations include onboard observers, airgun shutdowns for whales in the exclusion zone, ramp-up procedures, and the use of a minimum sound source. 

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors on marine mammals of the CPA are the degradation of 

water quality from operational discharges; noise generated by aircraft, vessels, operating platforms, and 

drillships; vessel traffic; explosive structure removals; seismic surveys; and marine debris from service 

vessels and OCS oil- and gas-related facilities. Some routine activities related to the CPA proposed 

action have the potential to have adverse, but not significant, impacts to marine mammal populations in 

the Gulf of Mexico. Impacts from vessel traffic, structure removals, and seismic activity could negatively 

impact marine mammals by increasing noise levels as well as having the potential to harm or harass 

marine mammal species. These activities, when mitigated as required by BOEM, BSEE, and NMFS, are 

not expected to have long-term impacts on the size and productivity of any marine mammal species or 

population. Mitigations reduce the risk of harassing or harming marine mammal species. Other routine 

activities such as aircraft activity, drilling and production noise, discharges, and marine debris are 

expected to have negligible effects.

Accidental disturbances resulting from the CPA proposed action, including oil spills and spillresponse activities, have the potential to have adverse, but not significant impacts on marine mammal

populations of the CPA. Characteristics of impacts (i.e., acute vs. chronic impacts) depend on the 

magnitude, frequency, location, and date of accidents; characteristics of spilled oil; spill-response 

capabilities and timing; and various meteorological and hydrological factors. Oil spills may cause 

chronic (long-term lethal or sublethal oil-related injuries) and acute (spill-related deaths occurring during 

a spill) effects on marine mammals. Long-term effects include decreases in prey availability and 

abundance because of increased mortality rates, change in age-class population structure because certain 

year-classes were impacted more by oil, decreased reproductive rate, and increased rate of disease or 
Description of the Environment and Impact Analysis 4-51

neurological problems from exposure to oil (Harvey and Dahlheim, 1994). The effects of cleanup 

activities are unknown, but increased human presence (e.g., vessels) could add to changes in marine 

mammal behavior and/or distribution, thereby additionally stressing animals and perhaps making them 

more vulnerable to various physiologic and toxic effects. 

Even after an oil spill is stopped, oiling or deaths of marine mammals could still occur due to oil and 

dispersants persisting in the water, past marine mammal and oil or dispersant interactions, and ingestion 

of contaminated prey (Lane et al., 2015). The animals’ exposure to hydrocarbons persisting in the sea 

may result in sublethal impacts (e.g., decreased health, reproductive fitness, and longevity; and increased 

vulnerability to disease) and some soft tissue irritation, respiratory stress from inhalation of toxic fumes, 

food reduction or contamination, direct ingestion of oil and/or tar, and temporary displacement from 

preferred habitats.

Cumulative Impacts 

The cumulative impact from oil and gas operations includes effects resulting from the CPA proposed 

action, as well as those resulting from past and future OCS leasing. These impact-producing factors 

include ingestion and entanglement in marine debris; contaminant spills and spill-response activities; 

vessel strikes; and noise from numerous sources (i.e., platforms, drillships, helicopters, vessels, etc.), 

seismic surveys, and explosive severance operations (e.g., decommissioning and structure removal). 

Potential non-OCS oil- and gas-related factors include vessel traffic and related noise (including from 

commercial shipping and research vessels), State oil and gas activities, military operations, commercial 

and recreational fishing, pollution, scientific research, and natural phenomena. The military (U.S. Navy 

and USCG) and other Federal agencies (USEPA, COE, and NMFS), dredging operations, commercial 

fishermen, and recreational boaters operate vessels and aircraft that can contribute to the ambient noise in 

the GOM. Noise in the ocean has become a worldwide topic of concern, particularly in the last two 

decades. Noises originate from a broad range of sources, both natural and anthropogenic (Richardson et 

al., 1995). Virtually all of the marine mammal species in the GOM have been exposed to OCS industrial 

noise due to the rapid advance into GOM deep oceanic waters by the oil and gas industry in recent years; 

whereas, 20 years ago, the confinement of industry to shallower coastal and continental shelf waters 

generally only exposed two species of marine mammals (the bottlenose dolphin and the Atlantic spotted 

dolphin) to industry activities and the related sounds. Most marine mammal species in the GOM, and 

particularly the deepwater mammals, rely on echolocation for basic and vital life processes including 

feeding, navigation, and communication. Noise levels that interfere with these basic marine mammal 

capabilities could have impacts on individuals and populations. The OCS oil and gas industry’s 

operations contribute noise to the marine environment from several different operations. It is believed 

that some of the industry-related noise is at lower frequencies than is detectable or in the sensitivity range 

of most of the GOM marine mammal species (Southall et al., 2007). Examples of some industry-related 

noise sources are summarized in the 2013 G&G Survey Techniques Information sheet (USDOI, BOEM, 

2013b) and are described in greater detail in Chapter 3 of the Atlantic OCS Proposed Geological and 

Geophysical Activities: Mid-Atlantic and South Atlantic Planning Areas, Final Programmatic 

Environmental Impact Statement (USDOI, BOEM, 2014c).

Cumulative impacts on marine mammals are expected to result in a number of chronic and sporadic 

sublethal effects (i.e., behavioral effects and nonfatal exposure to or intake of OCS oil- and gas-related 

contaminants or discarded debris) that may stress and/or weaken individuals of a local group or 

population and predispose them to infection from natural or anthropogenic sources (Harvey and 

Dahlheim, 1994). Disturbance (noise from vessel traffic and drilling operations) and/or exposure to 

sublethal levels of toxins and anthropogenic contaminants may stress animals, weaken their immune 

systems, and make them more vulnerable to parasites and diseases that normally would not be fatal 

(Harvey and Dahlheim, 1994). Cumulative noise can potentially cause masking effects that may prevent 

an individual from detecting another individual’s calls or interfere with navigation ability (Hatch et al., 

2014; Merchant et al., 2014; Southall et al., 2007). Available information regarding industry-related and 

other anthropogenic sound effects on marine mammals are mainly qualitative descriptions, but a 

committee was convened in 2010 to advance a method for systematic evaluation (Streever et al., 2012). 

Streever et al. (2012) identified typical anthropogenic sources during autumn bowhead whale migration in 

the Alaskan Beaufort Sea (i.e., production, seismic data acquisition, and vessel traffic), used available 

empirical data for bowhead behavior inputs, and conducted a modelled sea trial using simplified 
4-52 Central Planning Area Lease Sale 247 Supplemental EIS

assumptions to collect acoustic data for individual virtual animals. Empirical data (i.e., bowhead 

behavioral response to sound and migration patterns) provided relevant and necessary inputs for the 

model, ambient noise was not considered, and overall, the committee offered documentation and guidance 

for future work (Streever et al., 2012). Baseline soundscape is not well-documented for the GOM, and 

marine mammal behavioral data related to sound effects are not available for all species. These and other 

factors are essential for modelling inputs and for predicting effects of sound on marine mammals. BOEM 

continues to make efforts to gain a more thorough understanding of the potential effects of sound on 

marine mammals. The net result of any disturbance will depend upon the size and percentage of the 

population likely to be affected, the ecological importance of the disturbed area, the environmental and 

biological parameters that influence an animal’s sensitivity to disturbance and stress, or the 

accommodation time in response to prolonged disturbance (Hatch et al., 2008; Geraci and St. Aubin, 

1980). 

The effects of the CPA proposed action, when viewed in light of the effects associated with other 

past, present, and reasonably foreseeable future activities, may result in impacts to marine mammals when 

compared with before the Deepwater Horizon explosion, oil spill, and response; however, the magnitude 

of those effects cannot yet be determined. This is because the long-term effects may not yet be 

detectable. A large body of information regarding impacts of the Deepwater Horizon explosion, oil spill, 

and response on marine mammals is being developed through the NRDA process, but it is not yet 

available. Nonetheless, as mentioned earlier, operators are required to follow all applicable lease 

stipulations and regulations, as clarified by NTLs (i.e., NTL 2012-JOINT-G01, NTL 2015-BSEE-G03, 

and NTL 2012-JOINT-G02), to minimize these potential interactions and impacts. Even when taking into 

consideration the potential effects of the Deepwater Horizon explosion, oil spill, and response and the 

minimization of impacts through lease stipulations and regulations, no significant cumulative impacts to 

marine mammals would be expected as a result of the proposed activities when added to the impacts of 

past, present, or reasonably foreseeable oil and gas development in the area, as well as other ongoing 

activities in the area.

Non-OCS oil- and gas-related activities that may affect marine mammal populations include vessel 

traffic and related noise (including from commercial shipping and research vessels), State oil and gas 

activities, military operations, commercial fishing, pollution, scientific research, and natural phenomena. 

Groups such as the military (U.S. Navy and USCG) and other Federal agencies (USEPA, COE, and 

NMFS), dredges, commercial fishermen, and recreational boaters operate vessels and aircraft that can 

contribute to the ambient noise in the GOM. Pollution in the ocean comes from many point and nonpoint 

sources. The drainage of the Mississippi River results in massive amounts of chemicals and other 

pollutants being constantly discharged into the GOM. Tropical storms and hurricanes are normal 

occurrences in the GOM and along the coast. Generally, the impacts have been localized and infrequent. 

The actual impacts of these storms on the animals in the GOM, and the listed species and critical habitat 

in particular, have not yet been determined and, for the most part, may remain very difficult to quantify. 

An unusual mortality event (UME) is defined under the Marine Mammal Protection Act as “a 

stranding that is unexpected; involves a significant die-off of any marine mammal population; and 

demands immediate response.” Infections, biotoxins, human interactions, and malnutrition are considered 

causes of UMEs. A UME for bottlenose dolphins occurred off the coast of Texas in 2011-2012 when 

126 dolphins were stranded. While there is no known cause for the strandings, preliminary findings 

include infected lungs, poor body condition, discoloration of the teeth, and substance in the stomach in 

four of the animals (USDOC, NMFS, 2014). Further, a UME for the entire northern GOM began in 

February 2010 and is ongoing, continuing through 2015. This UME is defined by the Florida panhandle 

west to the Louisiana-Texas border (USDOC, NMFS, 2015a). As of November 30, 2015, the causes of 

these UMEs are still undetermined (USDOC, NMFS, 2015b) and the relationship of these UMEs to the 

Deepwater Horizon explosion, oil spill, and response require more research (refer to the “Incomplete or 

Unavailable Information” section below).

Within the GOM, there is a long-standing and well-developed OCS Program (more than 50 years); 

there are no data to suggest that activities from the preexisting OCS Program are significantly impacting 

marine mammal populations. The incremental contribution of the CPA proposed action to the cumulative 

impact is expected to be negligible. There are existing leases in the CPA with either ongoing or the 

potential for oil and gas exploration, drilling, and production activities. In addition, the potential for nonOCS oil- and gas-related activities discussed herein will continue to occur in the CPA irrespective of the 

CPA proposed action. The potential for effects from changes to the affected environment (post-
Description of the Environment and Impact Analysis 4-53

Deepwater Horizon), routine activities, accidental spills, low-probability catastrophic spills (which are 

discussed in Appendix B and which are not part of the CPA proposed action and not likely expected to 

occur), and cumulative effects remains whether or not the No Action or an Action alternative is chosen 

under this Supplemental EIS. Impacts on marine mammals from either smaller accidental events or lowprobability catastrophic events would remain the same. Therefore, in light of the CPA proposed action 

and its impacts, the incremental effect of the CPA proposed action on marine mammal populations is not 

expected to be significant when compared with the effects associated with other past, present, and 

reasonably foreseeable future activities, including non-OCS energy-related activities.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of Internet information sources (NOAA’s websites and the RestoreTheGulf.gov website), as 

well as recently published journal articles, was conducted to determine the availability of recent 

information on marine mammals. 

On December 13, 2010, NMFS declared a UME for cetaceans (whales and dolphins) in the Gulf of 

Mexico. Evidence of the UME was first noted by NMFS as early as February 2010, before the 

Deepwater Horizon explosion, oil spill, and response. As of November 29, 2015, a total of 

1,442 cetaceans (6% stranded alive and 94% stranded dead) have stranded since the start of the UME, 

with a vast majority of these strandings between Franklin County, Florida, and the Louisiana/Texas 

border (Table 4-1). In addition to investigating all other potential causes, scientists are investigating what 

role Brucella plays in the northern Gulf of Mexico UME. As of October 27, 2015, 68 out of 210 dolphins 

tested were positive or suspected positive for Brucella. More detail on the UME can be found on 

NMFS’s website (USDOC, NMFS, 2015a). It is unclear at this time whether the increase in strandings is 

related partially, wholly, or not at all to the Deepwater Horizon explosion, oil spill, and response. 

Studies that are published from the NRDA process and that evaluate the possible effects of the 

Deepwater Horizon explosion, oil spill, and response on bottlenose dolphins exposed to oiling 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., 2014, 

Venn-Watson et al., 2015a). A new study, which was published on February 11, 2015, indicates that the 

current multiyear marine mammal UME in the northern Gulf of Mexico has multiple groupings of high 

bottlenose dolphin mortalities and may be due to different contributing factors, including the Deepwater 

Horizon oil spill (Venn-Watson et al., 2015b). Identification of spatial, temporal, and demographic 

groupings within the UME suggest that this mortality event may involve different contributing factors 

varying by location and time, including a potential contributing role of the Deepwater Horizon explosion, 

oil spill, and response, which will be better discerned by incorporating diagnostic information including 

histopathology and other tissue analysis. 

A related study provided information regarding details on histopathology reports from bottlenose 

dolphins affected by the northern Gulf of Mexico UME (Venn-Watson et al., 2015a). This study 

confirmed that adrenal disease was prevalent in dolphins that stranded between 2010 and 2012, and it 

may offer insight to contributing factors for the UME. Results from this study also parsed out a subset of 

dolphins from Barataria Bay, Louisiana, and showed adrenal atrophy was more prevalent in that isolated 

cluster. Bacterial pneumonia was identified from dolphins before and during the UME, but it was 

detected more in the UME dolphins. These results are mentioned further in another study which 

suggested that the reproduction and survival of the subset of Barataria Bay dolphins was impacted by the 

chronic disease and overall poor health (Lane et al., 2015). This study continually monitored female 

bottlenose dolphins in Barataria Bay that were confirmed to be pregnant via ultrasound during a health 

assessment conducted in 2011and found decreases in reproductive success and high mortality when 

compared to a reference group not impacted by the Deepwater Horizon explosion, oil spill, and response 

(Lane et al., 2015).

Continued research will provide a better understanding about the relationship of these UMEs to the 

Deepwater Horizon explosion, oil spill, and response, which is still under investigation (refer to the 

“Incomplete or Unavailable Information” section below).

More detail on the UME can be found on NMFS’s website (USDOC, NMFS, 2015a). It is still 

unclear at this time whether the increase in strandings is related partially, wholly, or not at all to the 
4-54 Central Planning Area Lease Sale 247 Supplemental EIS

Deepwater Horizon explosion, oil spill, and response mainly due to the fact that other environmental 

stressors were present and may have contributed. A study by Carmichael et al. (2012) suggested that 

natural stressors combined with the Deepwater Horizon explosion, oil spill, and response may have 

created a “perfect storm” for bottlenose dolphins in the northern Gulf of Mexico. Many coastal species in 

the northern Gulf of Mexico, including dolphins, experienced unusually harsh winter conditions in early 

2010, which were followed by the Deepwater Horizon explosion, oil spill, and response. A third 

potential stressor was introduced in January 2011 when large volumes of cold freshwater, associated with 

melt water from an unusually large winter snowfall near the Mobile Bay watershed, entered the nearshore 

coastal systems very rapidly. This event happened days prior to the start of unusually high numbers of 

perinatal (near term to neonatal) bottlenose dolphin mortalities in the northern Gulf of Mexico from 

January to April 2011. 

While this information may ultimately be useful in expanding the available knowledge on baseline 

environmental conditions following the Deepwater Horizon explosion, oil spill, and response, it remains 

difficult to draw specific conclusions regarding the current overall bottlenose dolphin population in the 

GOM.

Incomplete or Unavailable Information 

After evaluating the information above, BOEM has determined that the new information does not 

change the conclusions presented in the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplemental EIS, as well as in the 

previously mentioned NEPA documents, BOEM has identified incomplete information for impacts on 

marine mammals from the Deepwater Horizon explosion, oil spill, and response. The final 

determinations on damages to marine mammal resources from the Deepwater Horizon explosion, oil spill, 

and response will ultimately be made through the NRDA process. The Deepwater Horizon explosion, oil 

spill, and response will ultimately allow a better understanding of any realized effects from a lowprobability catastrophic spill, which is not part of the CPA proposed action and not likely expected to 

occur. However, even with recent publications such as Lane et al. (2015), Schwacke et al. (2014), and 

Venn-Watson et al. (2015a and 2015b), the best available information on impacts to marine mammals 

does not yet provide a complete understanding of the effects of the oil spill and active response/cleanup 

activities from the Deepwater Horizon explosion, oil spill, and response on marine mammals as a whole 

in the GOM and whether these impacts reach a population level. As identified above, unavailable 

information, such as the anthropogenic impacts following an oil-spill response and the population 

variation due to naturally occurring events such as hurricanes and UMEs, provides challenges in 

understanding the baseline conditions and changes within marine mammal populations. As also 

previously discussed, the actual impacts of tropical storms and hurricanes on the GOM, and on the listed 

species and critical habitat in particular, have not yet been determined and, ultimately, the impacts may 

remain very difficult to quantify. However, BOEM used existing information and reasonably accepted 

scientific methodologies to extrapolate from available information in completing this analysis.

BOEM concludes that the unavailable information from these events may be relevant but not 

necessarily essential to reasonably foreseeable significant adverse impacts to marine mammals. In some 

specific cases, such as with bottlenose dolphins as noted above, the unavailable information may also be 

relevant to a reasoned choice among the alternatives based on the discussion below. The cost of obtaining 

data on the effects from the UME and/or Deepwater Horizon explosion, oil spill, and response are 

exorbitant, duplicative of efforts already being undertaken as part of the UME and NRDA, and would 

likewise take years to acquire and analyze through the existing NRDA and UME processes. The NMFS 

has jurisdiction for the investigation of marine mammal strandings and has only released raw data on 

stranding numbers to date. Therefore, it is not possible for BOEM to obtain this information within the 

timeline contemplated in the NEPA analysis of this Supplemental EIS, regardless of the cost or resources 

needed. In light of the incomplete or unavailable information, BOEM’s subject-matter experts have used 

available scientifically credible evidence, such as the scientific research evaluated in the prior 2012-2017 

Gulf of Mexico EISs, as well as new information such as the Schwacke et al. (2014) and Venn-Watson 

et al. (2015a and 2015b) papers, in this analysis and have applied it using accepted scientific methods and 

approaches. Wider ranging species may have been exposed to the Deepwater Horizon oil spill but are 

unlikely to have experienced population-level effects due to their wide-ranging distributions and behavior 

(i.e., Davis et al., 2000; Jochens et al., 2008). Further, impacts from the Deepwater Horizon explosion, 
Description of the Environment and Impact Analysis 4-55

oil spill, and response may be difficult or impossible to discern from other factors. For example, even 

20 years after the Exxon Valdez spill, long-term impacts to marine mammal populations were still being 

investigated (Matkin et al., 2008). Therefore, it is not possible for BOEM to obtain this information 

within the timeline contemplated in the NEPA analysis of this Supplemental EIS, regardless of the cost or 

resources needed. In light of the incomplete or unavailable information, BOEM’s subject-matter experts

have used available scientifically credible evidence in this analysis and applied it using accepted scientific 

methods and approaches. Nevertheless, a complete understanding of the missing information is not 

essential to a reasoned choice among alternatives for this Supplemental EIS (including the No Action and 

Action alternatives) for the three main reasons listed below.

(1) The CPA is an active oil and gas region with ongoing (or the potential for) 

exploration, drilling, and production activities. In addition, non-OCS oil- and gasrelated activities will continue to occur in the CPA irrespective of the CPA proposed 

action (i.e., fishing, military activities, and scientific research). The potential for 

effects from changes to the affected environment (post-Deepwater Horizon), routine 

activities, accidental spills (including low-probability catastrophic spills), and 

cumulative effects remains whether or not the No Action or an Action alternative is 

chosen under this Supplemental EIS. Impacts on marine mammals from either 

smaller accidental events or low-probability catastrophic events will remain the 

same.

(2) Some marine mammal populations in the CPA do not generally travel throughout 

areas affected by spilled oil from the Deepwater Horizon explosion, and they would 

not be subject to a changed baseline or cumulative effects from the Deepwater 

Horizon explosion, oil spill, and response (e.g., coastal bottlenose dolphins that are 

resident in the EPA). Other marine mammals, such as Bryde’s whales and

manatees, although potentially affected by the Deepwater Horizon explosion, oil 

spill, and response, also do not typically occur in the proposed CPA lease sale area. 

(3) Other wide-ranging populations of marine mammals (e.g., sperm whales and killer 

whales) that may occur in the CPA and within areas affected by the spill are 

unlikely to have experienced population-level effects from the Deepwater Horizon

explosion, oil spill, and response given their wide-ranging distribution and 

behaviors. 

Summary and Conclusion

BOEM has reexamined the analysis for marine mammals presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented above. The information discovered does not 

alter the impact conclusion for marine mammals presented in those NEPA documents. The analysis and 

potential impacts detailed and updated in those documents still apply for proposed CPA Lease Sale 247. 

4.1.1.13. Sea Turtles

BOEM has reexamined the analysis for sea turtles presented in the prior 2012-2017 Gulf of Mexico 

EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for sea turtles in those NEPA documents. The analysis 

and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the routine events, 

accidental events, and cumulative impacts associated with the CPA proposed action are presented in 

Chapter 4.2.1.13 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is provided in 

Chapter 4.2.1.13 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.13 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 
4-56 Central Planning Area Lease Sale 247 Supplemental EIS

In order to minimize potential interactions and impacts to sea turtles, operators are required to follow 

all applicable lease stipulations and regulations, as clarified by NTLs. The operator’s reaffirmed 

compliance with NTL 2012-JOINT-G01 (“Vessel-Strike Avoidance and Injured/Dead Protected Species 

Reporting”) and NTL 2015-BSEE-G03 (“Marine Trash and Debris Awareness Elimination”), as well as 

the limited scope, timing, and geographic location of the CPA proposed action, would result in negligible 

effects from the CPA proposed action on sea turtles. In addition, NTL 2012-JOINT-G02, 

“Implementation of Seismic Survey Mitigation Measures and Protected Species Observer Program,” 

minimizes the potential of harm from seismic operations to sea turtles and marine mammals; these 

mitigations include onboard observers, airgun shut-downs for whales in the exclusion zone, ramp-up 

procedures, the use of a minimum sound source, and delayed use of explosives when sea turtles or marine 

mammals are observed in the exclusion zone. 

Impacts of Routine Activities and Accidental Events

The routine activities associated with proposed CPA Lease Sale 247 that could potentially affect sea 

turtles include the following: the degradation of water quality resulting from operational discharges; 

noise generated by helicopter and vessel traffic, platforms, drill ships, and seismic exploration; noise and 

impact from explosive structure removals; vessel strikes; and marine debris generated by service vessels 

and OCS oil- and gas-related facilities. Noise disturbance and/or exposure to sublethal levels of toxins 

and anthropogenic contaminants may stress animals, weaken their immune systems, and make them more 

vulnerable to parasites and diseases that normally would not be fatal during their life cycle. Because of 

the mitigations (e.g., BOEM and BSEE proposed compliance with NTLs) as described in the prior 2012-

2017 Gulf of Mexico EISs and as summarized below, routine activities (e.g., operational discharges, 

noise, vessel traffic, and marine debris) related to the CPA proposed action are not expected to have longterm adverse effects on the size and productivity of any sea turtle species or populations in the northern 

Gulf of Mexico. With the mitigations, few deaths are expected from chance collisions with OCS oil- and 

gas-related service vessels, ingestion of plastic material, and pathogens. To minimize impacts to sea 

turtles and marine mammals from explosive structure removal, the use of explosives is delayed when sea 

turtles or marine mammals are observed in the exclusion zone. In addition, the best available scientific 

information indicates that sea turtles do not rely on acoustics; therefore, vessel noise and related activities 

(drilling, seismic exploration, and explosive structure removals) would have limited effects. Most routine 

OCS oil- and gas-related activities are expected to have sublethal effects that are not expected to rise to 

the level of significance.

Accidental events including marine debris generated by service vessels and OCS oil- and gas-related 

facilities, oil spills, contaminant spills, and spill-response activities may be associated with the CPA 

proposed action. The major impact-producing factors resulting from the accidental activities associated 

with the CPA proposed action that may affect loggerhead, Kemp’s ridley, hawksbill, green, and 

leatherback turtles include accidental oil spills, and spill-response activities that have the potential to 

impact small to large numbers of sea turtles in the GOM, depending on the magnitude and frequency of 

accidents, the ability to respond to accidents, the location and time of year the accidents occur, and 

various meteorological and hydrological factors. Impacts from smaller accidental events may affect 

individual sea turtles in the area, but impacts are unlikely to rise to the level of population effects (or 

significance) given the size and scope of such spills. Population-level impacts are not anticipated based 

on the best available information. Further, the potential remains for smaller accidental spills to occur in 

the CPA proposed action area, regardless of any alternative selected under this Supplemental EIS, given 

that it is an active oil and gas region with either ongoing or the potential for exploration, drilling, and 

production activities. 

Cumulative Impacts 

The cumulative analysis considers the effects of impact-producing factors of OCS oil- and gas-related 

impacts along with non-OCS oil- and gas-related impacts of other commercial, military, recreational, 

offshore, and coastal activities that may occur and adversely affect sea turtles in the same general area of 

the CPA proposed action. The major impact-producing factors resulting from cumulative OCS oil- and 

gas-related activities associated with the CPA proposed action that may affect loggerhead, Kemp’s ridley, 

hawksbill, green, and leatherback turtles and their habitats include marine debris, contaminant spills and 
Description of the Environment and Impact Analysis 4-57

spill-response activities, vessel strikes, noise, seismic surveys, and explosive structure removals. Lease 

stipulations and regulations, as clarified by NTLs, are in place to reduce vessel strike mortalities, impacts 

from marine trash and debris, and seismic surveys. The cumulative impact of these ongoing OCS oil- and 

gas-related activities on sea turtles may result in a number of chronic and sporadic sublethal effects (i.e., 

behavioral effects and nonfatal exposure to or intake of OCS oil- and gas-related contaminants or 

discarded debris) because these activities may stress and/or weaken individuals of a local group or 

population and may predispose them to infection from natural or anthropogenic sources. However, these 

effects are not expected to impact the GOM sea turtle population as a whole. As discussed in 

Appendix B, a low-probability catastrophic spill, which is not part of the CPA proposed action and not 

likely expected to occur, could have population-level effects on sea turtles. The net result of any 

disturbance depends upon the size and percentage of the population likely to be affected, the ecological 

importance of the disturbed area, the environmental and biological parameters that influence an animal’s 

sensitivity to disturbance and stress, or the accommodation time in response to prolonged disturbance 

(Geraci and St. Aubin, 1980). 

Non-OCS oil- and gas-related activities that may affect sea turtle populations include vessel noise and 

strikes (including commercial shipping, recreational, and research vessels), State drilling operations, 

military operations, commercial and recreational fishing, pollution, historic overexploitation, coastal 

infrastructure and habitat loss, dredging, pathogens, increased runoff, and natural phenomena. Effects 

from these activities could result in physiological stress, reduced reproductive success, weakened immune 

systems, or mortality of individuals. 

The effects of the CPA proposed action, when viewed in light of the effects associated with other 

past, present, and reasonably foreseeable future activities, may result in more significant impacts to sea 

turtles as compared with effects before the Deepwater Horizon explosion, oil spill, and response; 

however, the magnitude of those effects cannot yet be determined. Applicable lease stipulations and 

regulations, as clarified by NTLs such as those discussed above, would minimize impacts. Even when 

taking into consideration the potential effects of the Deepwater Horizon explosion, oil spill, and response 

and the minimization of impacts through lease stipulations and regulations, no significant cumulative 

impacts to sea turtles would be expected as a result of the proposed exploration activities when added to 

the impacts of past, present, or reasonably foreseeable oil and gas development in the area, as well as 

other ongoing activities in the area. 

No significant cumulative impacts to sea turtles would be expected as a result of the CPA proposed 

action. The potential for impacts is mainly focused on the individual, and population-level impacts are 

not anticipated. The effects of the CPA proposed action, when viewed in light of the effects associated 

with other past, present, and reasonably foreseeable future OCS oil- and gas-related activities, may result 

in greater impacts to sea turtles than before the Deepwater Horizon explosion, oil spill, and response; 

however, the magnitude of those effects cannot yet be determined. However, the incremental 

contribution of the CPA proposed action would not be likely to result in a significant incremental impact 

on sea turtles within the CPA; in comparison, non-OCS oil- and gas-related activities, such as 

overexploitation, commercial fishing, and pollution, have historically proved to be a greater threat to sea 

turtles.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search was conducted for information published on sea turtles, and various Internet sources were 

examined to determine any recent information regarding sea turtles. Sources investigated included, but 

were not limited to, journals and scientific articles, Google, Google Scholar, and other Federal and State 

natural resource management agency websites. All new relevant information was incorporated into the 

analysis below.

On April 21, 2015, NMFS published a final rule, “Fisheries of the Northeastern United States; 

Atlantic Sea Scallop Fishery and Northeast Multispecies Fishery; Framework Adjustment 26; Endangered 

and Threatened Wildlife; Sea Turtle Conservation,” which modified existing regulations on fishing gear 

alignment measures to protect sea turtles (Federal Register, 2015c). On March 23, 2015, NMFS 

published a draft proposed rule for “Endangered and Threatened Species; Identification and Proposed 

Listing of Eleven Distinct Population Segments of Green Sea Turtles (Chelonia mydas) as Endangered or 
4-58 Central Planning Area Lease Sale 247 Supplemental EIS

Threatened and Revision of Current Listings” (Federal Register, 2015d). Lamont et al. (2015) published 

a report on the importance of the Gulf of Mexico for different life stages of the GOM loggerhead distinct 

population segment. The authors suggested that the loss of individual habitats could have long-term 

consequences to population recovery by affecting several life stages (Lamont et al., 2015). Putman and 

Mansfield (2015) reported that the once thought passive-drifting juveniles (Sargassum-associated stage) 

are actually active swimmers. Their research used synchronized surface drifter and tagged turtle releases 

to support the hypothesis that sea turtles in the Gulf of Mexico are able to move themselves and are not 

dispersed solely by currents (Putnam and Mansfield, 2015). 

Within the GOM, there is a long-standing and well-developed OCS Program (more than 50 years); 

there are no data to suggest that activities from the preexisting OCS Program are significantly impacting 

sea turtle populations within these designated critical habitats. Therefore, in light of the CPA proposed 

action and its impacts, the incremental effect on sea turtle critical habitat is not expected to be significant 

when compared with non-OCS energy-related activities. 

Since January 1, 2011, a notable increase in sea turtle strandings has occurred in the northern GOM. 

While turtle strandings in this region typically increase in the spring, the increase is a cause for concern. 

The Sea Turtle Stranding and Salvage Network is monitoring and investigating this increase. The 

network is part of the NOAA/FWS National Marine Mammal Health and Stranding Response Program 

and encompasses the coastal areas of the 18 states from Maine through Texas. There are many possible 

reasons for the increase in strandings in the northern GOM, both natural and human caused (USDOC, 

NMFS, 2015b). These sea turtle species include loggerhead, green, Kemp’s ridley, leatherback, 

hawksbill, and unidentified. The most recent update to these stranding data on NMFS’s website was on 

August 25, 2013 (USDOC, NMFS, 2013), without conclusive findings about the strandings. 

The new information presented in this chapter provides additional details on the baseline affected 

environment for sea turtles, and it does not change BOEM’s conclusions about the potential effects of the 

CPA proposed action on sea turtles.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions from the 2012-2017 WPA/CPA Multisale EIS, WPA 233/CPA 231 

Supplemental EIS, and CPA 235/241/247 Supplemental EIS; nevertheless, there is still incomplete or 

unavailable information. As discussed above, as well as in the 2012-2017 WPA/CPA Multisale EIS,

WPA 233/CPA 231 Supplemental EIS, and CPA 235/241/247 Supplemental EIS, BOEM has identified 

incomplete information regarding impacts of the Deepwater Horizon explosion, oil spill, and response on 

sea turtles in the CPA. BOEM used existing information and reasonably accepted scientific 

methodologies to extrapolate from available information in completing the relevant analysis of potential 

oil exposure impacts to sea turtles using studies investigating evidence of oil and impacts stemming from 

exposure to oil (Witham, 1978; Vargo et al., 1986; Lutz and Lutcavage, 1989; Lutcavage et al., 1995; 

Plotkin and Amos, 1988). In addition, BOEM used information published on sea turtle nesting to draw 

conclusions about sea turtle populations following the Deepwater Horizon explosion, oil spill, and 

response (USDOC, NMFS, 2015b; State of Florida, Fish and Wildlife Conservation Commission, 2014a 

and 2014b; Share the Beach, 2015). Unavailable information on the effects to sea turtles from the 

Deepwater Horizon explosion, oil spill, and response (and thus changes to the sea turtle baseline in the 

affected environment) makes an understanding of the cumulative effects less clear. A large body of 

information is being developed though the NRDA process, but it is not yet available. Relevant data on 

the status of sea turtle populations after the Deepwater Horizon explosion, oil spill, and response and 

increased sea turtle GOM strandings may take years to acquire and analyze, and impacts from the 

Deepwater Horizon explosion, oil spill, and response may be difficult or impossible to discern from other 

factors. BOEM used existing information and reasonably accepted scientific methodologies to 

extrapolate from available information on sea turtle nests and strandings in completing the relevant 

analysis of sea turtle populations. None of these sources reveal reasonably foreseeable significant adverse 

impacts. Therefore, BOEM concludes that the unavailable information from these events may be relevant 

to foreseeable significant adverse impacts to sea turtles because the full extent of impacts on sea turtles is 

not known, but BOEM has determined that the information is not essential to a reasoned choice among 

alternatives for this Supplemental EIS.
Description of the Environment and Impact Analysis 4-59

Nevertheless, there are existing leases in the CPA with either ongoing or the potential for exploration, 

drilling, and production activities. In addition, non-OCS oil- and gas-related activities will continue to 

occur in the CPA irrespective of the CPA proposed action (i.e., fishing, military activities, and scientific 

research). The potential for effects from changes to the affected environment (post-Deepwater Horizon

explosion, oil spill, and response), routine activities, accidental spills (including low-probability 

catastrophic spills), and cumulative effects remains whether or not the No Action or an Action alternative 

is chosen under this Supplemental EIS. All wide-ranging populations of sea turtles that may occur in the 

CPA and within areas affected by the spill are unlikely to have experienced population-level effects from 

the Deepwater Horizon explosion, oil spill, and response given their wide-ranging distribution and 

behaviors. 

Summary and Conclusion

BOEM has reexamined the analysis for sea turtles presented in the prior 2012-2017 Gulf of Mexico 

EISs based on the additional information presented above. No new significant information was 

discovered that would alter the impact conclusion for sea turtles presented in those NEPA documents 

because of the available scientifically credible evidence in this analysis and based upon accepted 

scientific methods and approaches. The analysis and potential impacts discussed in those documents still 

apply for proposed CPA Lease Sale 247. 

4.1.1.14. Diamondback Terrapins

BOEM has reexamined the analysis for the Texas diamondback terrapin (Malaclemys terrapin 

littoralis) and Mississippi diamondback terrapin (Malaclemys terrapin pileata) (referred to as 

diamondback terrapins in this Supplemental EIS) presented in the prior 2012-2017 Gulf of Mexico EISs 

based on the additional information presented below. No new significant information was discovered that 

would alter the impact conclusion for diamondback terrapins in those NEPA documents. The analysis 

and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 247.

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action is 

presented in Chapter 4.2.1.14 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.14 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.14 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/241 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the prior 

2012-2017 Gulf of Mexico EISs. BOEM has found no significant new information that has become 

available since those NEPA documents were published. 

The national and subnational conservation status rank of diamondback terrapins is “vulnerable” or at 

a moderate risk of extirpation in the jurisdiction due to a fairly restricted range, relatively few populations 

or occurrences, recent and widespread declines, threats, or other factors. “Species of concern” is an 

informal term that refers to those species that might be in need of concentrated conservation actions. 

Such conservation actions vary depending on the health of the populations and the degree and types of 

threats. At one extreme, there may only need to be periodic monitoring of populations and threats to the 

species and its habitat. At the other extreme, a species may need to be listed as a federally threatened or 

endangered species under the Endangered Species Act. Species of concern receive no legal protection 

above those already afforded the species under other laws, and the use of the term does not necessarily 

mean that the species will eventually be proposed for listing as a threatened or endangered species. At the 

present time, the diamondback terrapin is neither a listed species nor a candidate for listing under the 

Endangered Species Act.

Impacts of Routine Activities and Accidental Events

The following routine activities associated with proposed CPA Lease Sale 247 could potentially 

affect diamondback terrapins: ingestion of beach trash and debris generated by service vessels and OCS 

oil- and gas-related facilities; direct injury from vessel traffic (boat propellers); and indirect injury from 

loss of habitat due to coastal marsh erosion associated with vessel traffic (refer to Chapters 4.1.1.3 and 

3.3.4.3 of this Supplemental EIS and Chapters 4.1.1.3 and 3.3.4.3 of the CPA 241/247 and EPA 226 

Supplemental EIS). Erosion to marshes can be indirectly attributed to OCS service traffic and onshore 
4-60 Central Planning Area Lease Sale 247 Supplemental EIS

development, but it is expected to cause little to no damage to the physical integrity, species diversity, or 

biological productivity of terrapin habitat. Adverse impacts due to routine activities resulting from the 

CPA proposed action are possible but unlikely. Annual awareness training, as required by NTL 2012-

BSEE-G01 (“Marine Trash and Debris Awareness and Elimination”), is expected to reduce the amount of 

marine debris from OCS oil- and gas-related activities and to minimize the effects on marine life. Due to 

the distance from shore, most impacts are not expected to reach terrapins or their habitat. Impacts that 

may occur from routine activities of the CPA proposed action are unlikely to have significant adverse 

effects on the size and recovery of any terrapin subspecies or population in the Gulf of Mexico because 

most routine, OCS oil- and gas-related activities are expected to have sublethal effects. Sublethal effects 

such as behavioral effects, nonfatal exposure to or intake of OCS oil- and gas-related contaminants, or 

discarded debris may stress and/or weaken individuals of a local group or population and predispose them 

to infection from natural or anthropogenic sources. These effects are not expected to rise to the level of 

significance to affect the populations.

Impact-producing factors associated with accidental events that may be associated with the CPA 

proposed action that could affect diamondback terrapins include offshore and coastal oil spills and spillresponse activities. Even after oil is no longer visible, terrapins may still be exposed while they forage in 

the salt marshes lining the edges of estuaries where oil may have accumulated under the sediments and 

within the food chain (Burger, 1994; Roosenburg et al., 1999). In 2010, contaminants associated with 

petroleum products were detected in low concentrations using blood plasma samples from terrapins along 

the Gulf Coast, but it was not conclusive in determining the source of the hydrocarbon compounds 

(Drabek et al., 2014). Cleanup efforts may affect reproductive success if nests are disturbed or destroyed. 

Hatching success studies at various oiled nesting sites of the northern diamondback terrapin suggest that 

spills may result in a reduction in nest size and increased mortality of spring emergers at the oiled sites 

(Wood and Hales, 2001). However, research on the PAH exposure and toxicology of eggs in the vicinity 

of a spill site found no correlation to substrate PAHs when compared with egg toxicology. The level of 

PAHs found in the eggs may be the result of maternal transfer and represent the exposure level of the 

nesting female rather than environmental exposure to PAHs from oil at the site of the nest (Holliday et al., 

2008). Impacts on diamondback terrapins from smaller accidental events are likely to affect individual 

diamondback terrapins in the spill area, but they are unlikely to rise to the level of population effects (or a 

level of significance) given the probable size and scope of such spills. Further, the potential remains for 

smaller accidental spills to occur in the CPA proposed action area, regardless of any alternative selected 

under this Supplemental EIS, given that it is an active oil and gas region with either ongoing or the 

potential for exploration, drilling, and production activities.

Cumulative Impacts 

The major OCS oil- and gas-related impact-producing factors that may affect the diamondback 

terrapin include (1) vessel traffic, (2) exposure or intake of OCS oil- and gas-related contaminants or 

debris, and (3) oil spills and spill response. To mitigate the potential impacts from OCS oil- and gasrelated activities, operators are required to follow all applicable lease stipulations and regulations, as 

clarified by NTLs, to minimize these potential interactions and impacts. The operator’s reaffirmed 

compliance with NTL 2012-BSEE-G01 (“Marine Trash and Debris Awareness and Elimination”), as well 

as the limited scope, timing, and geographic location of the CPA proposed action, would result in 

minimal effects from the proposed drilling activities on diamondback terrapins. Most spills related to the

CPA proposed action, as well as low-probability catastrophic spills, which are not part of the CPA 

proposed action and not likely expected to occur (refer to Appendix B for more information), as well as 

oil spills stemming from tankering and prior and future lease sales, are not expected to contact terrapins or 

their habitats. Most routine and accidental OCS oil- and gas-related activities are expected to have 

sublethal effects, such as behavioral effects, that are not expected to rise to the level of significance to the 

populations as a whole. Therefore, the incremental contribution of the CPA proposed action to 

cumulative impacts on terrapins is expected to be minimal.

Activities posing the greatest potential harm to terrapins are non-OCS oil- and gas-related factors, 

including habitat destruction, overharvesting and crab pot fishing, vessel traffic and road mortality, nest 

depredation, State oil- and gas-related activity, and natural processes. Spending most of their lives within 

their limited home ranges at the aquatic-terrestrial boundary in estuaries, terrapins are susceptible to 

habitat destruction (i.e., urban development, subsidence/sea-level rise, direct oil contact from non-OCS 
Description of the Environment and Impact Analysis 4-61

oil- and gas-related leasing program activities, and associated cleanup efforts). Habitat destruction, road 

construction, nest depredation, and drowning in crab traps are the most recent threats to diamondback 

terrapins. In the 1800’s, populations declined due to overharvesting for meat (Hogan, 2003). Tropical 

storms, hurricanes, and beach erosion threaten their preferred nesting habitats. Characteristics of terrapin 

life history render this species especially vulnerable to overharvesting and habitat loss. These 

characteristics include low reproductive rates, low survivorship, limited population movements, and nest 

site fidelity year after year. Inshore oil spills from non-OCS oil- and gas-related sources are potential 

threats to the terrapins’ brackish coastal marsh habitat.

The incremental contribution of the CPA proposed action is expected to be minimal compared with 

non-OCS oil- and gas-related activities. The major impact-producing factors resulting from the 

cumulative activities associated with the CPA proposed action that may affect diamondback terrapins

include oil spills and spill-response activities, alteration and reduction of habitat, and consumption of 

trash and debris. Overall, within the CPA, there is a long-standing and well-developed OCS Program 

(more than 50 years); there are no data to suggest that activities from the preexisting OCS Program are 

significantly impacting diamondback terrapin populations. Due to the extended distance from shore, 

impacts associated with activities occurring in the OCS Program are not expected to impact terrapins or 

their habitat. Non-OCS oil- and gas-related activities will continue to occur in the CPA irrespective of the

proposed CPA lease sale (i.e., crabbing, fishing, military activities, scientific research, and shoreline 

development). Therefore, in light of the above analysis of the CPA proposed action and its impacts, the 

incremental effect of the CPA proposed action on diamondback terrapin populations is not expected to be 

significant when compared with historic and current non-OCS oil- and gas-related activities, such as 

habitat loss, overharvesting, crabbing, and fishing. 

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of Internet information sources (NOAA’s and FWS’s websites, and the RestoreTheGulf.gov 

website), as well as recently published journal articles, was conducted to determine the availability of 

recent information on diamondback terrapins. The search revealed no new significant information was 

found at this time that would alter the overall conclusions of the prior 2012-2017 Gulf of Mexico EISs 

that impacts on diamondback terrapins associated with the CPA proposed action are expected to be 

minimal.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the conclusions from 

previous documents are still valid because no new information on diamondback terrapins pertinent to the 

proposed action has become available since publication of the prior 2012-2017 Gulf of Mexico EISs; 

nevertheless, there is still incomplete or unavailable information on possible impacts to diamondback 

terrapins as a result of the Deepwater Horizon explosion, oil spill, and response.

Diamondback terrapins within the CPA were not likely affected to any discernible degree by the 

Deepwater Horizon explosion, oil spill, and response, based on the best available information and the 

distance of terrapin habitat from the Macondo well. However, BOEM has identified incomplete 

information regarding impacts of the Deepwater Horizon explosion, oil spill, and response on 

diamondback terrapin in the CPA because little information about Deepwater Horizon explosion, oil spill, 

and response has been released as of the publication of this Supplemental EIS. Through the NRDA 

process, ongoing research and analysis of the presence of contaminants in terrapin eggs following the 

Deepwater Horizon oil spill is being conducted (USDOC, NOAA, 2012), but the results are not yet 

available. Relevant data on the status of diamondback terrapin populations after the Deepwater Horizon

explosion, oil spill, and response may take years to acquire and analyze, and impacts may be difficult or 

impossible to discern from other factors. This incomplete information may be relevant to evaluating 

adverse effects because the full extent of potential impacts on terrapins is not known. In place of the 

missing information, BOEM used existing information and reasonably accepted scientific methodologies 

to extrapolate from available information in completing the relevant analysis, such as studies investigating 

the evidence of oil and impacts stemming from exposure to oil (Burger, 1994; Roosenburg et al., 1999; 
4-62 Central Planning Area Lease Sale 247 Supplemental EIS

Holliday et al., 2008; Wood and Hales, 2001; Drabek et al., 2014). The results of these studies indicate 

impacts resulting from the Deepwater Horizon oil spill have been largely indistinguishable from natural 

fluctuations or variability due to other anthropogenic activities. Although the body of available 

information is incomplete and long-term effects cannot yet be known, past analyses are not indicative of 

significant population-level responses. BOEM has determined that the information is not essential to a 

reasoned choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for diamondback terrapins presented in the prior 2012-2017 Gulf 

of Mexico EISs. No new significant information was discovered that would alter the impact conclusion 

for diamondback terrapin presented in those NEPA documents because of the available scientifically 

credible evidence in this analysis and based upon accepted scientific methods and approaches. The 

analysis and potential impacts discussed in those documents still apply for the proposed CPA Lease 

Sale 247. 

4.1.1.15. Beach Mice

BOEM has reexamined the analysis for beach mice presented in the prior 2012-2017 Gulf of Mexico 

EISs based on the additional information presented below. No new significant information was 

discovered that would alter the conclusion for beach mice presented in those NEPA documents. The 

analysis and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 247.

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.15 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.15 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.15 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impact of Routine Activities and Accidental Events

The potential routine impact-producing factors that may affect beach mice are beach trash and debris, 

and efforts undertaken for the removal of marine debris or for restoration. An impact from the routine 

activities associated with the CPA proposed action on the Alabama (Peromyscus polionotus ammobates), 

Choctawhatchee (P. p. allophrys), St. Andrew (P. p. peninularis), and Perdido Key (P. p. trissyllepsis) 

beach mice is possible but unlikely. Impacts may result from consumption of or entanglement in beach 

trash and debris. Because the CPA proposed action would deposit only a small portion of the total debris 

that would reach the habitat, the impacts would be minimal. Any coastal discharges into marine water 

would not affect beach mice because they drink only fresh water. Boat traffic would have no impact on 

beach mice because they live above high tide. Helicopter traffic is expected to occur only well to the west 

of beach mouse habitat (the nearest existing helicopter hub is in Theodore, Alabama; refer to Chapter 

3.1.2.1.2. of the 2012-2017 WPA/CPA Multisale EIS). Coastal and nearshore construction projects (e.g., 

those producing OCS oil- and gas-related supporting structures and facilities and those involving OCS 

oil- and gas-related activities such as navigation channel dredging) are not expected to have impacts on 

beach mice because their critical habitat is protected.

The major impact-producing factors resulting from accidental events associated with the CPA 

proposed action that may affect beach mice include offshore and coastal oil spills, and spill-response 

activities. The oiling of beach mice could result in local extinction. An accidental spill occurring and 

contacting the shoreline is unlikely and the area of viable habitat is broad relative to the area potentially 

contacted by a spill (Figure 3-11 of the 2012-2017 WPA/CPA Multisale EIS). To contact beach mouse 

habitat oil would have to wash over the foredunes to beach mouse habitat in a storm surge. Disruption of 

beach mouse habitat could occur from oil-spill cleanup by trampling or vehicle traffic if personnel are not 

properly trained or supervised. A review of the available information shows that impacts on beach mice 

from accidental impacts associated with the CPA proposed action would be minimal.
Description of the Environment and Impact Analysis 4-63

Cumulative Impacts 

Cumulative activities have the potential to harm or reduce the abundance of beach mice. Cumulative 

impacts could potentially deplete some beach mice populations to unsustainable levels. However, the 

expected incremental contribution of the CPA proposed action to these cumulative impacts is negligible. 

The OCS oil- and gas-related impacts include oil spills and cleanup operations, the consumption of and 

entanglement in beach trash and debris, and trash and debris removal efforts. Most spills related to the

CPA proposed action and prior and future lease sales are not expected to contact beach mice or their 

habitats because the species lives above the intertidal zone where contact is less likely. Destruction of the 

remaining beach mouse habitat due to a low-probability catastrophic spill and cleanup activities, which is 

not part of the CPA proposed action and not likely expected to occur, would increase the threat of 

extinction. Impacts on beach mice from a catastrophic spill are discussed in Appendix B. 

Non-OCS oil- and gas-related impacts include oil spills from State oil and gas activities and import 

tankers; beach development that alters, fragments, or reduces habitat; hurricanes; and tropical storms. 

Within the last 20-30 years, the combination of habitat loss due to beachfront development, the isolation 

of remaining beach mouse habitat areas and populations, and the destruction of the remaining habitat by 

tropical storms and hurricanes have increased the threat of extinction of several subspecies of beach mice. 

In comparison to the cumulative OCS and non-OCS impacts, the expected incremental contribution of the

CPA proposed action to the cumulative impacts on beach mice is negligible.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of Internet information sources including published journal articles was conducted to 

determine the availability of recent information on beach mice. Websites visited included Federal 

agencies (U.S. Fish and Wildlife Service, U.S. Environmental Protection Agency, U.S. Geological 

Survey, and the Bureau of Ocean Energy Management) and various stakeholders (Sierra Club, National 

Fish and Wildlife Foundation, Nature Conservancy, Gulf Coast Ecosystem Restoration Council, and 

NOAA Central Library’s Deepwater Horizon Bibliography [Belter, 2014]). Where applicable, websites 

of subdivisions of many of these organizations were also consulted. Environmental journal articles were 

also located online using four search engines (JSTOR, EBSCO, Google Advanced Scholar Search, and 

Google Advanced Book Search). Three of the search engines collectively searched all of the ecology 

journals of six major publishers (John Wiley and Sons, Springer, Elsevier Science, Taylor and Francis 

Group, Cambridge University Press, and Oxford University Press). 

This search resulted in information about the Perdido Key beach mouse. Its population may be at a 

record high since its time of Federal listing as an endangered or threatened species on June 6, 1985 

(USDOI, FWS, 2014). Its requirements for corridor size and tolerance to fragmentation are unknown 

(USDOI, FWS, 2014); however, this new information indicates important baseline conditions about the 

population of this resource. 

Finally, Yanchis (official communication, 2015) indicates that no new NRDA research on the impacts 

of the Deepwater Horizon explosion, oil spill, and response has been made available since July 2014. 

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplemental EIS and in the prior 2012-2017 

Gulf of Mexico EISs, BOEM has identified incomplete information regarding beach mice in the CPA. 

This incomplete information may be relevant to an evaluation of adverse effects because it provides any 

change in the baseline environmental conditions for beach mouse populations in the affected environment 

from the Deepwater Horizon oil spill and response, exacerbating any impacts from the CPA proposed 

action. Relevant data on the status of beach mice after the Deepwater Horizon explosion, oil spill, and 

response may take years to acquire and analyze. Much of these data are being developed through the 

NRDA process, which may take years to complete. It is not possible for BOEM to obtain this 

information and incorporate it into this analysis within the timeline contemplated in the NEPA analysis of 
4-64 Central Planning Area Lease Sale 247 Supplemental EIS

this Supplemental EIS, regardless of the costs or resources needed. Current studies are investigating the 

effects of the Deepwater Horizon explosion, oil spill, and response activities on beach mice and their 

habitat (Frater, official communication, 2014). The time when the studies’ results will be released is 

unclear; therefore, BOEM cannot commit to waiting for this new information to become available to 

incorporate it into this Supplemental EIS. 

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing this analysis and formulating the conclusions presented here. The following is an example of 

extrapolations made from data summarized from OSAT-2 (2011) that BOEM used in the stead of 

unavailable and incomplete information. Assessment of the efficacy of shoreline cleanup in supratidal 

Alabama beach mouse habitat showed 60 percent “no oil observed,” 37 percent “light-very light oiling,” 

and 3 percent “moderate-heavy oiling.” Much of the supratidal habitat of the Perdido Key and 

Choctawhatchee beach mice showed “no oil observed.” Impacts on Perdido Key beach mouse habitat 

from the Deepwater Horizon explosion, oil spill, and response may not have occurred based on both the 

OSAT-2 approach and a newer approach that measured its population at a record high since its time of 

Federal listing as an endangered or threatened species on June 6, 1985 (USDOI, FWS, 2014). The 

supratidal habitat of the St. Andrew beach mouse was not affected by the Deepwater Horizon oil spill and 

response. A “toxicity reference value” is developed by USEPA for low (2-3 ring) and high (4-7 ring) 

molecular weight PAHs. Two scenarios for the PAH oral uptake by the Alabama beach mouse were 

reported: 10 percent contribution and a worst-case 100 percent contribution of small tarballs to the 

overall ingesting of soil. The estimated daily dose of PAHs from oral uptake following the Deepwater 

Horizon oil spill and response did not exceed the toxicity reference value for low molecular weight PAHs 

in the Alabama beach mouse.

The following is another example of extrapolations made from data summarized from Frater (official 

communication, 2011) that BOEM used in the stead of unavailable or incomplete information. Known 

occupied beach mouse habitat has been trampled, denuded, and eroded. Reasonable estimates of the 

amount of beach mouse habitat that has been damaged, altered, or destroyed varies from 1 to 50 ac (0.4 to 

20 ha) throughout the range of the five Gulf Coast subspecies (4 of which are federally protected). 

Preliminary data suggest that impacts to beach mouse habitat was very minor. The impacts to beach 

mouse habitat during the Deepwater Horizon response probably have not caused significant impacts to 

the population levels of beach mice. Impacts on Perdido Key beach mouse habitat from the Deepwater 

Horizon explosion, oil spill, and response may not have occurred based on a measure of its population at 

a record high since its time of Federal listing as an endangered or threatened species on June 6, 1985 

(USDOI, FWS, 2014). The habitat that was damaged was primarily young dunes. The damage may 

restrict population expansion and recovery for a few years, but anticipated restoration activities will 

probably offset this impact in the near future. 

Any additional NRDA information obtained from the Deepwater Horizon oil spill and response is 

unlikely to be so significant as to change the assessed impact level. In summary, BOEM has determined 

that the information is not essential to a reasoned choice of alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for beach mice presented in the prior 2012-2017 Gulf of Mexico 

EISs based on the additional information presented above. The information discovered does not alter the 

impact conclusion for beach mice presented in those NEPA documents. The analysis and potential 

impacts detailed and updated in those documents still apply for proposed CPA Lease Sale 247. 

4.1.1.16. Coastal and Marine Birds

BOEM has reexamined the analysis for coastal and marine birds presented in the prior 2012-2017 

Gulf of Mexico EISs based on additional information presented below. No new significant information 

was discovered that would alter the impact conclusion for coastal and marine birds presented in those 

NEPA documents. The analysis and potential impacts discussed in those documents still apply for 

proposed CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.16 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 
Description of the Environment and Impact Analysis 4-65

provided in Chapter 4.2.1.16 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.16 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

The majority of the effects resulting from routine activities of the CPA proposed action (Tables 3-2 

through 3-4) on threatened or endangered (Table 4-1 of the WPA 233/CPA 231 Supplemental EIS) and 

nonthreatened and nonendangered coastal and marine birds are expected to be sublethal, primarily 

disturbance-related effects (Chapter 4.2.1.16.2 of the 2012-2017 WPA/CPA Multisale EIS and Chapter 

4.2.1.16 of the WPA 233/CPA 231 Supplemental EIS). Major potential impact-producing factors 

resulting from routine activities for marine birds in the offshore environment include the following: 

• habitat loss and fragmentation (Fahrig, 1997 and 1998); 

• behavioral effects primarily due to disturbance from OCS oil- and gas-related 

helicopter and service-vessel traffic and associated noise (Habib et al., 2007; Bayne 

et al., 2008); 

• mortality due to exposure and intake of OCS oil- and gas-related contaminants, e.g., 

drilling discharges and produced waters (Wiese et al., 2001; Fraser et al., 2006) and 

discarded debris (Robards et al., 1995; Pierce et al., 2004); 

• sublethal, chronic effects from air emissions (Newman, 1979; Newman and 

Schreiber, 1988); and 

• mortality and energetic costs associated with structure presence and associated light 

(Russell, 2005; Montevecchi, 2006). 

Overall, impacts to avian species from routine activities are expected to be adverse but not significant. 

Impacts from routine activities are more likely to be sublethal to moderate numbers of birds and 

infrequently lethal. Mortality is expected to be distributed among many populations with no substantial 

mortality for any one population. 

Impact-producing factors from accidents include oil spills, regardless of size and despite oil-spill 

cleanup activities, including the release of rehabilitated birds. Information regarding the CPA proposed 

action and oil-spill information can be found in Table 3-22 of the 2012-2017 WPA/CPA Multisale EIS. 

Oil spills (and disturbance impacts associated with cleanup activities) have the greatest impact on coastal 

and marine birds. Sometimes the rehabilitation of birds may have benefits beyond wild bird condition 

because of veterinary care that wild birds do not receive. However, the handling of birds during 

rehabilitation may sometimes stress birds. Depending on the timing and location of the spill, even small 

spills can result in major avian mortality events (Piatt et al., 1990a and 1990b; Castège et al., 2007; 

Wilhelm et al., 2007). Small amounts of oil can affect birds, and mortality from oil spills is often related 

to numerous symptoms of toxicity (Burger and Gochfeld, 2001; Albers, 2006). Data from actual spills 

strongly suggest that impacts to a bird species’ food supply are typically delayed after initial impacts from 

direct oiling (e.g., Esler et al., 2002; Velando et al., 2005; Zabala et al., 2010). Sublethal, long-term 

effects of oil on birds have previously been documented (Esler et al., 2000; Alonso-Alvarez et al., 2007), 

including changes to sexual signaling (Pérez et al., 2010). 

Oil-spill impacts on birds from the CPA proposed action are expected to be adverse but not 

significant, given the number and relatively small size of spills expected over the 40-year life of the CPA 

proposed action (Table 3-12 of the 2012-2017 WPA/CPA Multisale EIS). Impacts of oil-spill cleanup 

from the CPA proposed action are also expected to be adverse, but not significant, and may be negligible 

depending on the scope and scale of efforts. Significant impacts to coastal and marine birds could result 

in the event of a low-probability catastrophic spill, depending on the timing, location, and size of the spill. 

However, this is not part of the CPA proposed action and is not likely expected to occur. For additional 

information on a low-probability catastrophic spill, refer to Appendix B. 
4-66 Central Planning Area Lease Sale 247 Supplemental EIS

Cumulative Impacts 

The cumulative analysis considers impact-producing factors that may adversely affect populations of 

threatened and endangered avian species, as well as nonthreatened and nonendangered species, related to 

OCS oil- and gas-related and non-OCS oil- and gas-related activities. Several OCS oil- and gas-related 

impact-producing factors could potentially affect coastal and marine birds, including the following: 

• air pollution;

• pollution of coastal and offshore waters resulting from OCS oil- and gas-related 

activities, including platform and pipeline oil spills, produced waters, and any spillresponse activities;

• structure presence and lighting (e.g., OCS platforms);

• aircraft and vessel traffic and oil-spill cleanup associated noise; 

• maintenance and use of navigation waterways;

• habitat loss, fragmentation, and alteration from coastal facility and OCS oil- and gasrelated support structure construction; 

• OCS pipeline landfalls; and

• trash and debris.

The incremental contribution of the CPA proposed action to the cumulative impact is considered 

adverse but not significant because the effects of the most probable impacts, such as lease sale-related 

operational discharges and helicopters and service-vessel noise and traffic, are expected to be sublethal; 

and some displacement of local individuals or flocks may occur to other habitat, if available. In general, 

the net effect of habitat loss from oil spills, OCS oil- and gas-related pipeline landfalls, and maintenance 

and use of navigation waterways, as well as habitat loss and modification resulting from coastal facility 

construction and development, will probably reduce the overall carrying capacity of the disturbed 

habitat(s). That is, impacted habitats may result in reductions to both species composition (fewer species) 

and abundance (lower numbers) as compared with what the area supported historically. These would be 

the most serious cumulative impacts on birds. In addition to the factors listed above, there are several 

non-OCS oil- and gas-related impact-producing factors that could potentially impact coastal and marine 

birds. These factors include the following: air pollution; habitat loss, alteration, and fragmentation 

associated with commercial and residential construction and industrial growth; water pollution including 

State or tanker oil- and gas-related spills and any spill-response activities and pollution of coastal waters 

resulting from municipal, industrial, and agricultural runoff and discharge; aircraft and vessel (including 

military) activities and noise; nonconsumptive and consumptive recreation; maintenance and use of 

navigation waterways; collisions with anthropogenic structures; predation; diseases; climate change and 

related impacts; impacts from storms and floods; fisheries interactions; and trash and debris. Impacts 

from non-OCS oil- and gas-related resources (including impacts from the State oil and gas program and 

associated structure collisions and spills, waste and debris, water pollution, and air pollution) on habitat 

and bird behavior operate in a way similar to the OCS oil- and gas-related impacts on each resource 

discussed previously in this chapter. Non-OCS oil- and gas-related impacts include avian habitat loss, 

alteration, and fragmentation associated with commercial and residential development, and maintenance 

and use of navigation waterways combined with the associated effects of climate change (including sealevel rise and the frequency and intensity of tropical storms. Oil spills, regardless of size, are but one of a 

myriad of anthropogenic avian mortality sources. 

Mortality as a result of long migrations may also impact coastal and marine bird populations. Various 

passerine forest birds include a substantial migration (approximately tens of kilometers; Gauthreaux, 

1975) over land at the end of their spring nonstop trans-Gulf flight. Such a flight over land may also 

occur before crossing the Gulf itself. The mortality rates of species during nonstop flight due to 

exhaustion of energy reserves are unknown. House cat predation is a threat mostly for passerines, which 

comprise most of the trans-Gulf migrants. Despite the number of waterfowl killed annually under Federal 
Description of the Environment and Impact Analysis 4-67

hunting laws, their populations remain strong. Sublethal effects on birds may also include interactions 

with commercial fisheries and noise disturbance from non-OCS oil- and gas-related air and vessel traffic.

In conclusion, the incremental contribution of the CPA proposed action to the cumulative impact is 

considered adverse but not significant when compared with the impacts of some of the reasonably 

foreseeable non-OCS oil- and gas-related factors.

New Information Available Since the Publication of 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of Internet information sources including published journal articles was conducted to 

determine the availability of recent information on coastal and marine birds. Websites visited included 

5 for Federal agencies (U.S. Environmental Protection Agency [including its Gulf of Mexico Program], 

U.S. Geological Survey, National Oceanographic and Atmospheric Administration, U.S. Fish and 

Wildlife Service, and the Bureau of Ocean Energy Management), several for various stakeholders (Sierra 

Club, National Fish and Wildlife Foundation, Nature Conservancy, Gulf of Mexico Alliance, BaratariaTerrebonne National Estuary Program, National Audubon Society, Restoration Council), and NOAA 

Central Library’s Deepwater Horizon Bibliography (Belter, 2014). Where applicable, websites of 

subdivisions of many of these organizations were also consulted. Environmental journal articles were 

also located online using four search engines (JSTOR, EBSCO, Google Advanced Scholar Search, and 

Google Advanced Book Search). Three of the search engines collectively searched all of the ecology 

journals of six major publishers (John Wiley and Sons, Springer, Elsevier Science, Taylor and Francis 

Group, Cambridge University Press, and Oxford University Press). The search revealed new information 

on the attraction of trans-Gulf nocturnally migrant birds to lights on platforms. Birds will likely stop over 

on platforms with lights with spectral red or with high intensity. This is likely only during overcast, 

rainy, or foggy conditions at night (Marquenie et al., 2013). Also, they might stop over if they encounter 

head winds that slow their trans-Gulf migration. At least sometimes, they may decline to stop over during 

overcast, rainy, or foggy conditions at night if the platform work lights are green or blue (Marquenie 

et al., 2013) and if the lights are of moderate (not high) intensity (Wiltschko and Wiltschko, 2001; 

Wiltschko et al., 2003). The cause-and-effect processes of lights and occurrence or absence of attraction 

to platforms and stopovers on platforms during migration are being investigated. They have not been 

rigorously determined (Wiltschko and Wiltschko, 2014; Ramirez et al., 2014). The cause-and-effect 

processes likely include an optical magnetic compass (with undetermined biochemistry) in the retinas of 

bird eyes, at least for some species. Small populations of birds may be affected by lights, which may 

affect species richness (community structure). Effects may include positive (i.e., from resting and 

feeding) and/or negative (i.e., from nocturnal circulation and collisions) results of stopping over on 

platforms. Nocturnal circulation occurs when birds circle platforms at night and use up an unspecified 

amount of their migratory energy reserves. Negative impacts may in turn affect bird watching and bird 

hunting as economically valuable activities. Injury or mortality from collision or nocturnal circulation 

(after stopover) at the small population level for a long-term (10+ years) with almost full recovery means 

that impacts to trans-Gulf migrants will be major. Positive impacts for trans-Gulf migrants due to use of 

platforms as stopovers for resting and/or feeding may possibly compensate as much as completely for 

impacts of injury or mortality. Positive impacts of stopover may convert any major negative impacts of 

stopover to negligible impacts, but considerable uncertainty surrounds the impacts; therefore, further 

study is required. The impact of artificial light along the coast on birds has not been studied. 

The search also revealed new information on the impact of the Deepwater Horizon incident on seabirds. 

Mortality from the Deepwater Horizon explosion, oil spill, and response is 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 for the analyzed species were 

60,000-15,000,000 for four procellariiform species, 9,000 for one pelecaniform species, and 

96,000-500,000 for three charadriiform species (Haney et al., 2014a). Total bird mortality shoreward of 

25 mi (40 km) from shore was estimated by two models, culminating in estimates of 600,000 birds using 

one model and 800,000 birds using the other (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). 
4-68 Central Planning Area Lease Sale 247 Supplemental EIS

This new information estimates a small negative shift in baseline numbers. No data are yet available on 

recovery since the analysis by Haney et al. (2014a and 2014b), but the initial negative shift was 

insufficient to cause a change in the expected impacts to seabirds from the CPA proposed action. The 

shift was extrapolated from the increased mortality due to the Deepwater Horizon explosion, oil spill, and 

response. The work by Haney et al. (2014 and 2014b) is not for NRDA. Any additional (NRDA) 

information obtained from the Deepwater Horizon oil spill and response is unlikely to be so significant as 

to change the relative importance of non-OCS oil- and gas-related factors to bird populations, which is 

demonstrated in Table 4-7 of the 2012-2017 WPA/CPA Multisale EIS and Table 4-2 of the WPA

233/CPA 231 Supplemental EIS. 

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplemental EIS and in the prior 2012-2017 

Gulf of Mexico EISs, BOEM has identified incomplete information regarding coastal and marine birds in 

the CPA. This incomplete information may be relevant to the evaluation of adverse effects because it 

provides any change in the baseline environmental conditions for bird populations in the affected 

environment from the Deepwater Horizon oil spill, exacerbating any impacts from the CPA proposed 

action. Much of these data are being developed through the NRDA process, which may take years to 

complete. This information cannot be obtained because it may take years to acquire and analyze through 

the NRDA process, producing a reliable, model-based estimate of mortality that accounts for detectionrelated issues (Flint et al., 1999; Byrd et al., 2009). The information cannot be released due to ongoing 

NRDA litigation and, even after it is released, the impacts of the oil spill may be difficult or impossible to 

discern from other factors. It is not possible for BOEM to obtain this information and incorporate it into 

this analysis within the timeline contemplated by the NEPA analysis of this Supplemental EIS regardless 

of the costs or resources needed. At present, the best available information does not provide a complete 

understanding of the effects of the spilled oil or the recovery potential for the most impacted species 

(Tables 4-8, 4-12, and 4-13 of the 2012-2017 WPA/CPA Multisale EIS and Table 4-2 of the WPA 

233/CPA 231 Supplemental EIS).

No Gulf of Mexico regional estimates are available for annual mortality rates from several 

anthropogenic sources of mortality. However, recent quantitative national estimates allow a qualitative 

but not quantitative extrapolation to the Gulf of Mexico. The national estimates include songbirds, and 

these are relevant because they may be impacted during trans-Gulf migration. An estimated range of 

national annual mortality from collision with vehicles is 62-275 million birds per year (Loss et al., 

2014a). An estimate of national annual mortality from collision with buildings is 599 million birds per 

year (Loss et al., 2014b). Finally, an estimate of annual mortality from predation by free-ranging 

domestic cats is 1.4-3.7 billion birds per year (Loss et al., 2013). The mortality estimates are nationwide 

and not just for the northern Gulf of Mexico, where impacts would be much less. Loss et al. (2014b) 

provide unprecedented state-of-the-art science (Machtans and Thogmartin, 2014).They and others used 

species-specific local mortality estimates and an explicit treatment of known biases with acknowledged 

uncertainty in the final national estimate. All of this allowed extrapolation to total bird mortality on a 

national scale. It is imperfect but it is innovative science because the local studies were never designed to 

be used for extrapolation (Machtans and Thogmartin, 2014).

BOEM has identified incomplete information on avian mortality rates during migration, from both 

exhaustion and collisions with platforms. Various passerine forest birds include a substantial migration 

(approximately tens of kilometers; Gauthreaux, 1975) over land at the end of their spring nonstop transGulf flight. Such a flight over land may also occur before crossing the Gulf of Mexico itself unless 

substantial forests are located near the shoreline. The mortality rates of species during nonstop flight due 

to exhaustion of energy reserves are unknown. This information may be relevant to the evaluation of 

adverse impacts from OCS oil- and gas-related activities because, at the present time, there is no way to 

discern if annual or long-term mortality from such activities, due mostly to collisions with platforms (over 

the life of newly installed platforms) for any of the affected trans-Gulf migrant species considered herein 

results in major population-level impacts (Russell, 2005, Chapters 17 and 18). Annual mortality may 

cause major impacts because it has been estimated at 200,000 birds (Russell, 2005). However, in lieu of 

this data gap, BOEM extrapolated existing information using accepted scientific methodologies to 
Description of the Environment and Impact Analysis 4-69

complete this analysis. Studies indicate that the numbers of birds successfully migrating across the Gulf 

in the spring are so great (on the order of magnitude of hundreds of millions; Russell, 2005) that any 

mortality associated with exhaustion from migration or collision with platforms would likely not 

exacerbate any cumulative impacts of other mortality factors. Birds suffering from exhaustion would 

typically be sick or weak, and their mortality would be a case of natural selection, where the populations 

would be strengthened (made more fit). The potential range of a bird adapted to fatten up enough to cross 

extensive barriers like the open ocean or Gulf of Mexico may be approximated by data on shorebirds, 

which may be an accurate proxy for the maximum possible flight range of forest songbirds that may 

traverse the GOM. The computed maximum nonstop range of a bar-tailed godwit leaving Alaska (based 

on a model of fuel load) was all the way to the South Pole (Pennycuick and Battley, 2003). Given what 

we know about the life history characteristics of many of these species (e.g., age at first reproduction, 

clutch size, and nest success), as well as the estimate of maximum nonstop flight range, the potential for 

such major population-level impacts as a result of migration mortality seems relatively low (Arnold and 

Zink, 2011, page 2). 

Additionally, the focus within this Supplemental EIS is on major (population- and ecosystem-level) 

impacts to bird management, protection, and conservation, as well as ecoregions and landscapes over the 

long term rather than impacts to individual birds and small sites over a short time. Therefore, although 

the body of available information on migratory mortality is incomplete and long-term effects are 

unknown, the evidence currently available supports the analyses in the prior 2012-2017 Gulf of Mexico 

EISs. The evidence does not indicate severe adverse impacts to coastal and marine bird populations as a 

result of migration mortality from collisions with platforms.

In summary, BOEM has determined that the incomplete information is not essential to a reasoned 

choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for coastal and marine birds presented in the prior 2012-2017 

Gulf of Mexico EISs based on the additional information presented above. No new significant 

information was discovered that would alter the impact conclusion for coastal and marine birds presented 

in those NEPA documents because of the available scientifically credible evidence in this analysis and 

based upon accepted scientific methods and approaches. The analysis and potential impacts discussed in 

those documents still apply for proposed CPA Lease Sales 247.

4.1.1.17. Gulf Sturgeon

BOEM has reexamined the analysis for Gulf sturgeon presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for Gulf sturgeon presented in those NEPA documents. 

The analysis and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 

247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.17 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.17 of the WPA 233/CPA 231 Supplemental EIS, Chapter 4.1.1.17 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

Potential impacts from routine activities to the threatened Gulf sturgeon (Acipenser oxyrinchus 

desotoi) and their designated critical habitat from routine activities associated with the CPA proposed 

action may occur from drilling and produced-water discharges, degradation of estuarine and marine water 

quality from infrastructure, dredging activities, vessel traffic, pipeline installation, and explosive platform 

removal. Designated Gulf sturgeon critical habitat is confined to State waters, and navigation channels 

are exempt from the critical habitat status. Most activities related to the CPA proposed action would 
4-70 Central Planning Area Lease Sale 247 Supplemental EIS

occur in Federal waters (i.e., structure placement, drilling, removal, etc.). Though critical habitat may be 

impacted directly or indirectly, such impacts are expected to be negligible due to the distance of Gulf 

sturgeon habitat and life cycles from most activities related to the CPA proposed action.

Potential impacts from accidental events on Gulf sturgeon and the designated critical habitat may 

occur primarily from oil spills. Unusually low tidal events, increased wave energy, or the use of oil 

dispersants increases the risk of impact with bottom-feeding and bottom-dwelling fauna. For this reason, 

dispersants are not expected to be used with coastal spills. Winds, currents, and outflow from the 

Mississippi River would also diminish the volume of a slick. The spreading of the slick would reduce the 

oil concentrations that would potentially impact the coastal Gulf sturgeon critical habitat. The potential 

risk to sturgeon would result from either direct contact with oil spills (or the potential PAHs introduced 

through the spill), exposure through their diet or, in some cases, long-term exposure to produced water or 

water associated with extraction processes. If there is contact with spilled oil, it could have detrimental 

physiological effects on an individual Gulf sturgeon. Due to the distance of the activity from shore and 

Gulf sturgeon critical habitat, there is a minimal risk of any oil coming in contact with Gulf sturgeon from 

an offshore spill.

Cumulative Impacts 

The cumulative impact from routine OCS oil- and gas-related operations includes oil spills. Potential 

non-OCS oil- and gas-related impact-producing factors considered in this analysis include natural 

catastrophes, fishing, and other factors that can result in changes to habitats.

Gulf sturgeon could be impacted by oil spills resulting from the CPA proposed action. The effects on 

Gulf sturgeon from contact with spilled oil would be sublethal (Berg, 2006). Other potential impacts may 

occur from drilling and produced-water discharges, bottom degradation of estuarine and marine water 

quality by nonpoint runoff from estuarine OCS oil- and gas-related facilities, vessel traffic, pipeline

installation, and explosive removal of structures. However, these impacts are expected to have negligible 

effects on Gulf sturgeon and their designated critical habitat, and will not be discussed as part of the 

cumulative impacts analysis.

For a low-probability catastrophic spill, the proximity, type of oil, weather conditions, as well as the 

amount and location (distance offshore and water depth) of the dispersant treatment, may contribute to the 

severity of the spill’s impact to the sturgeon and its habitat (for more information regarding a lowprobability catastrophic spill, which is not part of the CPA proposed action and not likely expected to 

occur, refer to Appendix B).

The Gulf sturgeon and its critical habitat can be cumulatively impacted by non-OCS oil- and gasrelated activities including natural catastrophes, commercial fishing, State oil and gas activities, and other 

factors that can result in habitat changes. Recent climate trends and projections indicate more frequent 

and higher intensity storms, flooding, droughts, coastal erosion, and rising sea levels (Parry et al., 2007), 

all of which could impact Gulf sturgeon critical habitat, spawning areas and life history stages. Other 

naturally occurring events that can impact Gulf sturgeon may increase, such as the 1999 and 2005 red 

tides in Choctawhatchee Bay that resulted in sturgeon deaths (USDOI, FWS, 2000; State of Florida, Dept. 

of Environmental Protection, 2012) or El Niño/La Niña events, which can cause fish to extend their range 

(USDOC, NOAA, 2013a). Deaths of adult sturgeon and potential habitat alterations are expected to occur 

from commercial fishing. Non-OCS oil- and gas-related accidental spills can happen, such as the 2008 

industrial spill in the Pearl River in Louisiana that resulted in the mortality of juvenile and adult Gulf 

sturgeon (Kimmel and Constant, 2011) and the February 2013 spill of wastewater from a water pollution 

control plant into the Withlacoochee River in Georgia (Schaefer, 2013). While these events have 

happened recently and there is ongoing monitoring of the impacted areas, it is unknown how the related 

mortalities affect the Gulf sturgeon population. Upstream urbanization and commercial or residential 

development can adversely affect the water quality downstream and therefore can have potential 

cumulative impacts to Gulf sturgeon.

The CPA proposed action would not require dredging near natal rivers used as migratory routes to 

upstream spawning areas. While there could be a need for maintenance dredging not directly related to 

OCS oil- and gas-related activities in the nearshore waters, juvenile or adult sturgeon using these areas 

have the ability to avoid the regulated dredging activity.

On August 8, 2013, a notice of issuance of permits was published in the Federal Register for take of 

Gulf sturgeon for scientific research (Federal Register, 2013). Substantial damage to Gulf sturgeon 
Description of the Environment and Impact Analysis 4-71

critical habitat is expected from natural catastrophes and inshore alteration activities, such as dam 

building or maintenance dredging. As a result, it is expected that the Gulf sturgeon would experience a 

decline in population sizes and a displacement from their current distribution that would last more than 

one generation. 

The incremental contribution of the CPA proposed action to the cumulative impacts on Gulf sturgeon

is expected to be negligible. This is because the effect of contact between lease sale-specific oil spills and 

Gulf sturgeon is expected to be sublethal, and regulations and mitigations decrease impacts from routine 

events. Other non-OCS oil- and gas-related activities, including storms and anthropogenic factors on 

habitat, are expected to result in more incremental and cumulative impacts to this species. Non-OCS oiland gas-related impacts are seen as the primary cumulative impacts on Gulf sturgeon, compared with the 

CPA proposed action, even in light of incomplete or unavailable information. 

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search was conducted for published journal articles on Gulf sturgeon, and various Internet websites 

(Federal Register, FWS, National Marine Fisheries Service, USGS, and Gulf Coast State Natural 

Resources websites) were examined to determine any recent information regarding this species.

The search revealed an article by Rudd et al. (2014) that used surgically implanted acoustic telemetry 

tags in Gulf sturgeon to examine spatial distribution and movement patterns. Fidelity rates in rivers in the 

spring and summer and overwintering in the Gulf of Mexico to feed were reconfirmed. These authors 

suggested that Gulf sturgeon should be managed by individual riverine populations. They suggested that 

western GOM populations may have higher mortality rates than eastern GOM populations. This new 

information about Gulf sturgeon and its critical habitat does not change the conclusions of the prior 2012-

2017 Gulf of Mexico EISs. 

The NRDA team has completed an assessment plan for nearshore resources following the Deepwater 

Horizon explosion, oil spill, and response. The goals set forth are to characterize the extent and 

distribution of nearshore sediment oiling, to model exposure of organisms in the water column and 

benthos to hydrocarbons in nearshore sediments, and to evaluate and quantify injury to nearshore benthic 

organisms (USDOC, NOAA, 2012). Work plans for this assessment can be found on NOAA’s website 

(USDOC, NOAA, 2013b). Analyses of available data are unavailable.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. This incomplete information may be relevant to adverse effects 

because the PAH toxicity to similar fish (shortnose sturgeon, salmonids) varies substantially, although 

conclusions of the impacts of PAHs on fish are often generalized due to the difficulty in testing any 

specific chemical (Berg, 2006). The final determinations on damages to Gulf sturgeon resources from the 

Deepwater Horizon explosion, oil spill, and response will ultimately be made through the NRDA process. 

The Deepwater Horizon explosion, oil spill, and response will ultimately allow a better understanding of 

any realized effects from a low-probability catastrophic spill, which is not part of the CPA proposed 

action and not likely expected to occur. This information cannot be obtained because the means to obtain 

it are not known and because related information already in development has not been released from the 

NRDA process.

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing this analysis and formulating the conclusions presented here. For example, studies such as 

Malins et al. (1985), O’Conner and Huggett (1988), Fabacher et al. (1991), Varanasi et al. (1992), 

Bateman and Brim (1994), Baumann et al. (1996), Matthiessen and Sumpter (1998), and Berg (2006) 

indicated no reasonably foreseeable significant adverse impacts from oil. For example, in the rare event 

that Gulf sturgeon have contact with oil, this could cause sublethal effects, including causing the fish to 

temporarily migrate from the affected area, irritation of gill epithelium, an increase of liver function in a 

few adults, and possibly interference with reproductive activity. The juvenile and subadult Gulf sturgeon, 

at a minimum, seasonally use the nearshore coastal waters and could potentially be at risk from both 
4-72 Central Planning Area Lease Sale 247 Supplemental EIS

coastal and offshore spills. Due to the distance of the proposed activity from shore and the Gulf sturgeon 

critical habitat, there is a minimal risk of any oil coming in contact with Gulf sturgeon from an offshore 

spill. Indeed, there is little risk of most routine activities impacting Gulf sturgeon for the same reasons. 

Therefore, BOEM has determined that the information is not essential to a reasoned choice among 

alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for Gulf sturgeon presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information provided above. No new significant information was 

discovered that would alter the impact conclusion for these Gulf sturgeon presented in those NEPA

documents because of the available scientifically credible evidence in this analysis and based upon 

accepted scientific methods and approaches. The analysis and potential impacts discussed in those 

documents still apply for proposed CPA Lease Sale 247. 

4.1.1.18. Fish Resources and Essential Fish Habitat

BOEM has reexamined the analysis for fish resources and essential fish habitat (EFH) presented in 

the prior 2012-2017 Gulf of Mexico EISs based on the additional information presented below. No new 

significant information was discovered that would alter the impact conclusion for fish resources and EFH 

presented in those NEPA documents. The analysis and potential impacts discussed in those documents 

still apply for proposed CPA Lease Sale 247.

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.18 and Appendix D of the 2012-2017 WPA/CPA Multisale EIS. Updated 

information is provided in Chapter 4.2.1.18 of the WPA 233/CPA 231 Supplemental EIS and Chapter 

4.1.1.18 of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. 

Also, EFH is discussed in the following chapters of this Supplemental EIS: water quality (Chapter 

4.1.1.2); wetlands (Chapter 4.1.1.4); seagrass communities (Chapter 4.1.1.5); live bottoms (Chapter 

4.1.1.6); topographic features (Chapter 4.1.1.7); Sargassum communities (Chapter 4.1.1.8); 

chemosynthetic deepwater benthic communities (Chapter 4.1.1.9); nonchemosynthetic deepwater 

benthic communities (Chapter 4.1.1.10); and soft bottom benthic communities (Chapter 4.1.1.11). The 

following information is a summary of the resource description and impact analysis incorporated from the 

prior 2012-2017 Gulf of Mexico EISs. Any new information that has become available since those 

documents were published is presented below. 

The Gulf of Mexico supports a great diversity of fish. The distribution of fish species is related to 

variable ecological factors that include salinity, primary productivity, and bottom type. These factors 

differ widely across the Gulf of Mexico and between the inshore and offshore waters. Characteristic fish 

resources are associated with the various environments and are not randomly distributed. 

Impacts of Routine Activities and Accidental Events

Effects on fish resources and EFH from routine activities associated with the CPA proposed action 

could result from coastal and marine environmental degradation as a result of construction activities (i.e., 

from onshore facilities to well-site construction activities, including board roads, ring levees, and 

impoundments), pipeline trenching, offshore discharges of drilling muds and produced waters, anchor and 

anchor chain placement, and structure emplacement and removal. Since the majority of fish species 

within the CPA are estuary dependent, any modification of the coastal environment resulting from the 

CPA proposed action has the potential to adversely affect EFH and fish resources through the loss of 

nursery habitat or functional impairment of existing habitat through decreased water quality (Chambers, 

1992; Stroud, 1992). Although the potential exists, it is expected that any possible coastal and marine 

environmental degradation from the CPA proposed action would have little effect on fish resources or 

EFH.

With the CPA proposed action, BOEM projects no new coastal infrastructure with the exception of a 

potential new pipeline landfall and a potential new gas processing facility. Although the installation of 

pipelines has the potential to temporarily resuspend sediment in localized areas, this is expected to have a 

negligible impact. Depending on the sediment characteristics, sediment load, and duration of exposure, 
Description of the Environment and Impact Analysis 4-73

impacts to commercially valuable species within a sediment plume can vary. Responses range in severity 

from no effect to mortality, but mobile species can avoid severe effects by limiting exposure. Sessile 

organisms and those with limited mobility may be exposed for longer durations, leading to increasingly 

severe impacts (e.g., increased respiratory rates, reduced feeding, and mortality). Regulations, 

mitigations, and practices reduce the undesirable effects on coastal habitats from dredging and other 

construction activities; permit requirements should ensure that pipeline routes avoid sensitive coastal 

habitat types. At the expected level of impact, the resultant influence on fish resources would be short 

term and localized, affecting only small portions of fish populations and selected areas of EFH. As a 

result, there would be little disturbance to fish resources or EFH.

The primary impacting sources to water quality in coastal waters are point-source and storm-water 

discharges from support facilities, vessel discharges, and nonpoint-source runoff. These activities are not 

only highly regulated but also localized and temporary in nature. The impacts to coastal water quality 

from routine activities associated with the CPA proposed action should be minimal because of the 

distance to shore of most routine activities and USEPA regulations that restrict discharges. Offshore 

water quality is affected temporarily and in a limited area by the discharge of produced water and the 

overboard discharge of drilling muds. Maintenance dredging and canal widening in inshore areas causes 

only the temporary suspension of sediments. Negative impacts from most of these routine operations 

would require a short time for fish resources to recover. This is because of multiple life history and 

environmental factors such as fecundity or year-class recruitment through oceanographic circulation.

Offshore, many of the EFHs are protected under the stipulations and regulations currently in place. 

Without these measures, there could be major negative impacts to topographic features and live bottoms. 

However, with routine impact-producing factors mitigated by BOEM through the Topographic Features 

Stipulation and the Live Bottom (Pinnacle Trend and Low Relief) Stipulation, negative impacts are 

expected to be avoided. These stipulations establish a No Activity Zone around BOEM-protected 

topographic features, such as the Flower Gardens Banks, and NTL 2009-G39 and NTL 2009-G40 advise 

operators of BOEM’s distancing requirements for bottom-disturbing activity from identified seafloor 

features (i.e., live bottoms, Pinnacles, topographic features, potentially sensitive biological features, and 

features capable of supporting high-density deepwater benthic communities). Additionally, hard substrate 

habitat provided by structure installation in areas where natural hard bottom is rare will tend to increase 

fish populations or attract fish populations. The removal of these structures will eliminate that habitat, 

except when decommissioned platforms are used as artificial reef material. This practice is expected to 

increase over time. A more detailed discussion of decommissioning and the impacts of these activities on 

marine fishes can be found in Chapters 3.1.1.10 and 4.1.1.19, respectively.

For these reasons, as well as the fact that Gulf of Mexico fish stocks have retained both diversity and 

relatively stable biomass throughout the years of offshore development and other disturbances, the CPA 

proposed action is expected to result in a minimal decrease in fish resources and/or standing stocks or in 

EFH.

Accidental disturbances resulting from the CPA proposed action, including oil or chemical spills, 

have the potential to adversely affect fish resources and EFH within the CPA. If oil or chemical spills due 

to the CPA proposed action were to occur in open waters of the OCS proximate to mobile adult finfish, 

the effects would likely be nonfatal and the extent of damage would be reduced because adult fish have 

the ability to move away from a spill, metabolize hydrocarbons, and excrete both metabolites and parent 

compounds. Weathered crude oil has been shown in laboratory experiments and field research to cause a 

range of sublethal effects, including malformation, genetic damage, and physiological impairment in 

different life history stages of different fish species (Whitehead et al., 2011; Brewton et al., 2013; 

Incardona et al., 2014; Mager et al., 2014). Oil can be lethal to fish, especially in larval and egg stages, 

since early life stages of animals are usually more sensitive to environmental stress than adults (Moore 

and Dwyer, 1974) and are unable to avoid spills, putting early development stages at greater risk. 

Therefore, fish populations would primarily be affected if oil reaches the coastal and estuarine areas 

because many species reside in estuaries for at least part of their life cycle or are dependent on the 

nutrients exported from the estuaries to the shelf region. However, pelagic species may also be affected. 

Offshore spawning and nursery habitat supports several valuable species that could likewise be impacted 

by widespread contamination of the epipelagic region. However, due to natural variability in spawning 

success, recruitment, oceanographic conditions, and other factors, it is difficult to attribute specific causes 

to short-term shifts in stocks, and research to date has been inconclusive with respect to the individual 

contributions of the many factors impacting these fishes because of natural variability in spawning 
4-74 Central Planning Area Lease Sale 247 Supplemental EIS

success, recruitment, oceanographic conditions, and other factors (Rijnsdorp et al., 2009; Atlantic Bluefin 

Tuna Status Review Team, 2011; Rooker et al., 2013). The probability of a spill impacting these nursery 

habitats is low. Much of the coastal northern Gulf of Mexico is a moderate- to high-energy environment; 

therefore, sediment transport and tidal stratification should reduce the chances for oil persisting in these 

areas if they are oiled. The extent to which a spill could impact offshore spawning and nursery habitat is 

highly dependent upon the time of year of the event. 

The effect of oil spills that may be associated with the CPA proposed action on fish resources is 

expected to cause a minimal decrease in standing stocks of any population because most spill events 

would be small in scale and localized. Historically, there have been no oil spills of any size in the Gulf of 

Mexico that have had a long-term impact on fishery populations. Although many potential effects of the 

Deepwater Horizon explosion, oil spill, and response have been alleged, the actual effects are largely 

unknown and likely to remain so for several years, until more research is completed and the analyses 

become available. Recent analysis of early stage survival of fish species inhabiting seagrass nursery 

habitat from Chandeleur Islands, Louisiana, to St. Joseph Bay, Florida, pre- and post-Deepwater Horizon

oil spill show that immediate catastrophic losses of 2010 cohorts were largely avoided and that no shifts 

in species composition occurred following the spill (Fodrie and Heck, 2011). Analysis of the effects of a 

low-probability catastrophic oil spill can be found in Appendix B. The fish populations of the Gulf of 

Mexico have repeatedly proven to be resilient to large, annually occurring areas of hypoxic conditions, 

major hurricanes, and oil spills. Accidental events from the CPA proposed action are not expected to 

significantly affect fish populations or EFH in the Gulf of Mexico. 

Cumulative Impacts 

There are widespread anthropogenic and natural factors that impact EFH and fish populations in the 

GOM. These include OCS oil- and gas-related and non-OCS oil- and gas-related factors. The OCS oiland gas-related activities that could impact fish resources and EFH include construction, pipeline and 

structure emplacement, anchor and anchor chain placement, drilling and produced-water discharges, 

structure removal, and oil spills. The routine OCS oil- and gas-related activities have the potential to 

impact fish and degrade EFH, but they would probably only have a minimal effect on fish resources and 

EFH because of the regulations, mitigations, and permit reviews that are applied for OCS oil- and gasrelated activity. Oil spills, although considered rare events, can affect seagrass beds through physical 

oiling and destruction from oil-spill cleanup. Low-probability catastrophic spills, which are not part of 

the CPA proposed action and not likely expected to occur, similar to the Deepwater Horizon explosion 

and oil spill are analyzed in Appendix B. Overall, the incremental contribution of OCS oil- and gasrelated impacts to fish populations and EFH is minor due to regulations, mitigations, and permit reviews.

Non-OCS oil- and gas-related factors that can impact fisheries and EFH include State oil and gas 

activity, inshore pollutants, dredging, coastal development, human population expansion, commercial and 

recreational fishing, overfishing, and natural phenomena. Inshore inputs of pollutants to estuaries from 

runoff and industry are contributors to wetland loss and the degradation of water quality. Fish are known 

to avoid any area of adverse water quality, such as hypoxia (Wannamaker and Rice, 2000; Craig and 

Bosman, 2013). Canal dredging primarily accommodates commercial, residential, and recreational 

development, and increased population and commercial pressures on the Gulf Coast are also causing the 

expansion of ports and marinas. Resource management agencies, both State and Federal, set restrictions 

and issue permits in an effort to mitigate the effects of development projects and industry activities. The 

Federal and State governments are also funding research and coastal restoration projects; however, it may 

take decades of monitoring to ascertain the feasibility and the long-term effectiveness of these coastal 

restoration efforts.

Overfishing (including bycatch) has contributed to population effects seen with GOM fishes. The 

Magnuson-Stevens Fishery Conservation and Management Act and its amendments address sustainable 

fisheries and set guidelines for protecting marine resources and habitat from fishing- and nonfishingrelated activities. Under this Act, fisheries management plans, including limits on catch and fishing 

seasons, are developed and proposed by the regional fisheries management councils for approval and 

implementation by NMFS. State agencies regulate inshore fishing seasons and limits.

Some natural phenomena can impact fish resources and EFHs. Nearshore habitat can be affected 

through events such as severe storms and floods. These events can accelerate wetland loss or damage 

oyster reef habitat. Offshore resources such as biologically sensitive underwater features may be 
Description of the Environment and Impact Analysis 4-75

damaged or buried by events like storms or turbidity flows, potentially affecting fish resources. 

Additionally, variability in spawning success and juvenile survival directly affect Gulf of Mexico fish 

populations. These natural phenomena are all continual, integral elements of the ecosystem, and impacts 

attributed to these events are often exacerbated by anthropogenic activities.

While all of these events and activities cause some sort of effect on the different EFHs and fish 

resources, many anthropogenic inputs, including the CPA proposed action, are now monitored, regulated, 

and mitigated by the permitting agency or State. The CPA proposed action would add a minimal amount 

to the overall cumulative effects.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of Internet information sources and scientific journals was conducted to determine the 

availability of recent information (including NMFS’s databases, the Gulf of Mexico Fishery Management 

Council’s website, Science Direct, EBSCO, Elsevier, PLoS ONE, JSTOR, and BioOne). This search 

revealed new information relevant, but not essential, to an analysis of the potential impacts of OCS oiland gas-related activities on fish resources and EFH. The following studies investigated the impacts of 

acute and chronic hydrocarbon exposure on juvenile and adult life stages of species and the rate of 

incidence for histopathologic lesions and other physiological effects in fishes associated with particular 

habitats or feeding strategies: Murawski et al. (2014); Brown-Peterson et al. (2015); Millemann et al. 

(2015); and Snyder et al. (2015). In general, studies suggest that impacts are spatiotemporally limited and 

that fishes have experienced reduced incidence of oil-related effects over time; however, accumulations in 

some species indicate continued exposure, potentially resulting in long-term effects. This information 

serves to expand our understanding of the potential impacts an oil spill may have on valuable marine 

species. A review of literature by Fodrie et al. (2014) examines evidence of oil-related impacts on fishes 

and the lack of detectable population-level effects. This review proposes mechanisms that could explain 

the apparent discrepancy, such as masking by biological and environmental factors, natural population 

variability, other anthropogenic disturbances, and compensatory processes. This analysis supports 

previous conclusions reached by BOEM and suggests research that could improve future assessment 

efforts.

Overall, newly available information supports and reaffirms the conclusions reached in the prior 

2012-2017 Gulf of Mexico EISs. Therefore, the analysis and potential impacts discussed in those NEPA

documents still apply for proposed CPA Lease Sale 247.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. BOEM has identified incomplete information regarding impacts 

of the Deepwater Horizon explosion, oil spill, and response or other oil exposure on fish resources and 

EFH in the CPA. This incomplete information may be relevant to evaluating adverse effects because the 

full extent of the potential impacts on fish resources and EFH are not known. Relevant data on fish 

resources and EFH after the Deepwater Horizon explosion, oil spill, and response may take years to 

acquire and analyze. Much of these data are being developed through the NRDA process, which may 

take years to complete. Therefore, it is not possible for BOEM to obtain this information within the 

timeline contemplated in the NEPA analysis of this Supplemental EIS, regardless of the cost or resources 

needed.

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing this analysis and formulating the conclusions presented here. Although the body of available 

information is incomplete and the long-term effects cannot yet be known, the evidence currently available 

supports past analyses and is not indicative of significant population-level responses. Therefore, BOEM 

has determined that the incomplete information is not essential to a reasoned choice among tge 

alternatives. Additional information on commercially and recreationally valuable species can be found in 

Chapters 4.1.1.19 and 4.1.1.20, respectively.
4-76 Central Planning Area Lease Sale 247 Supplemental EIS

Summary and Conclusion

BOEM has reexamined the analysis for fish resources and EFH presented in the prior 2012-2017 Gulf 

of Mexico EISs based on the additional information presented above. No new significant information 

was discovered that would alter the impact conclusion for the fish resources and EFH presented in those 

NEPA documents because of the available scientifically credible evidence in this analysis and based upon 

accepted scientific methods and approaches. The analysis and potential impacts discussed in those 

documents still apply for proposed CPA Lease Sale 247.

4.1.1.19. Commercial Fisheries

BOEM has reexamined the analysis for commercial fisheries presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for commercial fisheries presented in those NEPA

documents. The analysis and potential impacts discussed in those documents still apply for proposed 

CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.19 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.19 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.19 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors include seafloor disturbing activities (e.g., pipeline

installation, infrastructure emplacement, and dredging), waste discharge (e.g., drilling muds, cuttings, and 

produced waters), explosive severance operations (decommissioning and structure removal), and spaceuse conflicts (e.g., seismic surveys and structure emplacement). Some of these factors have the potential 

to indirectly impact commercial fisheries through degradation or loss of habitat. Healthy fish stocks 

depend on EFH, which is defined in the Sustainable Fisheries Act as “those waters and substrate 

necessary to fish for spawning, breeding, feeding, and/or growth to maturity.” Since the majority of 

commercially harvested species within the CPA are estuary-dependent, coastal environmental degradation 

resulting from the CPA proposed action has the potential to adversely affect EFH and commercially 

valuable fishes. However, analysis of routine OCS oil- and gas-related activities, such as pipeline 

trenching, maintenance dredging, canal construction, and OCS discharge of drilling muds and produced 

water, has identified only short-term localized disturbances that minimally impact commercially valuable 

fish species and associated EFH. Resuspended sediments and offshore discharges settle or dissipate 

rapidly, limiting both the area affected and the duration of the effect. Additionally, regulations, 

mitigations, and current practices reduce the undesirable effects of construction and operational activities 

on coastal and offshore habitats. At the expected level of impact, the resultant influence on fish resources

would be indistinguishable from natural fluctuations and other anthropogenic influences. 

Fish mortality as a result of decommissioning operations is an example of OCS oil- and gas-related 

activities directly impacting fishes. However, a study of structure removals employing explosive 

severance methods found that associated mortality for three commercially important fishes did not 

significantly alter projected stocks (Gitschlag et al., 2000). To account for inherent variations in species 

composition and abundance among platforms (e.g., Stanley and Wilson, 1997; Gitschlag et al., 2000; 

Stanley and Wilson, 2000; Wilson et al., 2003), mortality estimates were doubled and stock estimates 

were recalculated. Although the study was limited and cannot be directly applied to all species or 

habitats, it is reasonable to assume that other commercially important fishes would respond similarly. At

the projected rate of removal, these activities are not expected to have a substantial negative impact on 

stocks of commercially important fishes or, by extension, the associated fisheries. 

Space-use conflicts could result directly from OCS oil- and gas-related activities that restrict or 

prevent other users from accessing OCS resources. For example, seismic surveys and structure 

emplacement represent short-term and semi-permanent obstructions, respectively. Although studies have 
Description of the Environment and Impact Analysis 4-77

shown airguns can produce behavioral responses in fishes, possibly even resulting in species- or gearspecific effects on catch rate (Popper and Hastings, 2009; Fewtrell and McCauley, 2012; Løkkeborg 

et al., 2012), there is insufficient data to consistently predict responses and important variables, such as 

the duration of exposure and repeated exposure. Commercial fisheries’ impacts related to seismic surveys 

are not fully understood. The OCS structures present a minor space-use conflict when compared with the 

area available for commercial fishing. In addition, the current paradigm posits these structures act as both 

fish-attracting and production-enhancing devices, depending upon the species (Carr and Hixon, 1997; 

Gallaway et al., 2009; Shipp and Bortone, 2009). The resultant assemblages frequently include 

commercially valuable fishes, such as tunas (Thunnus spp.), red snapper (Lutjanus campechanus), and 

wahoo (Acanthocybium solanderi). Therefore, OCS structures may either enhance or obstruct 

commercial fishing, depending upon gear type (e.g., hydraulic reel, greenstick, trawl, and long-line) and 

target species. For more information, refer to Chapters 4.1.1.18 and 4.1.1.20. 

Accidental events that could impact commercial fisheries are very limited. Oil spills on the OCS that 

are >1 bbl due to the CPA proposed action are highly unlikely (Table 3-12 of the 2012-2017 WPA/CPA 

Multisale EIS). If oil spills due to the CPA proposed action were to occur in open waters of the OCS 

proximate to mobile adult finfish, the effects would likely be nonfatal and the extent of damage would be 

reduced because adult fish have the ability to avoid adverse water conditions. This behavioral mechanism 

allows mobile fishes to move away from the source of the hydrocarbons, thereby minimizing exposure. 

However, larval and juvenile life stages are typically more vulnerable than adults and would be expected 

to suffer significant adverse effects as a result of acute oil exposure (Brewton et al., 2013; Incardona 

et al., 2014; Mager et al., 2014). Species-specific response, duration of exposure, and hydrocarbon 

concentration are critical factors in determining short- and long-term effects, but BOEM conservatively 

assumes larval and juvenile fishes exposed to oil in close proximity to the point of accidental release 

would be expected to experience mortality. The probability of an offshore spill impacting nearshore 

environments is low, and spilled oil would generally be volatilized or dispersed by currents in the 

offshore environment prior to impacting inshore nursery habitat. Overall, the commercial fish and 

shellfish populations have remained healthy in the Gulf of Mexico despite ongoing anthropogenic and 

natural disturbances.

Cumulative Impacts 

The cumulative analysis considers activities that have occurred, are currently occurring, and could 

occur and adversely affect commercial fisheries by harming fishes and affecting landings, or the value of 

those landings, for the years 2012-2051. These activities include the effects of the OCS Program 

(proposed action and prior and future OCS lease sales) resulting from pipeline installation, channel 

dredging, waste discharge, decommissioning operations, seismic surveys, and structure emplacement. In 

recent years, decommissioning operations have exceeded structure emplacements, resulting in a decrease 

in the total number of OCS platforms. BOEM expects this trend to continue throughout the OCS 

Program, further reducing the potential for impacts to commercial fisheries through space-use conflicts. 

Although the decommissioning process frequently employs explosive severance methods, which result in 

localized mortality of fishes, the cumulative impact to commercially valuable stocks is expected to be 

indistinguishable from natural fluctuations and the effects of commercial and recreational fishing activity. 

For information on impacts resulting from catastrophic spills, refer to Appendix B. 

Non-OCS oil- and gas-related factors include State oil and gas activity, coastal development, natural 

phenomena, and commercial and recreational fishing. Although some OCS oil- and gas-related activities 

contribute incrementally to the degradation and loss of wetland habitat (Chapter 4.1.1.4), the cumulative 

impact is small in comparison with the combined effect of State oil and gas development; coastal 

commercial, residential, and agricultural development; levees; river channelization; and episodic natural 

phenomena. The cumulative direct impact to commercial fisheries through a reduction in resources 

(fishable area and fish stocks) is negligible.
4-78 Central Planning Area Lease Sale 247 Supplemental EIS

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

BOEM has examined newly available information for findings that may impact the analyses of 

routine activities, accidental events, and cumulative impacts and that may potentially alter previous 

conclusions. A search of Internet information sources and scientific journals was conducted to determine 

the availability of recent information (including NMFS’s databases, the NOAA Gulf Spill Restoration 

Publications website, the Gulf of Mexico Fishery Management Council website, Science Direct, EBSCO, 

Elsevier, PLoS ONE, JSTOR, and BioOne). This search revealed new information relevant, but not 

essential, to an analysis of the potential impacts of OCS oil- and gas-related activities on commercial 

fisheries. Several recent studies investigated the impacts of acute and chronic hydrocarbon exposure on 

juvenile and adult life stages of species and the rate of incidence for histopathologic lesions and other 

physiological effects in fishes associated with particular habitats or feeding strategies (Murawski et al., 

2014; Brown-Peterson et al., 2015; Millemann et al., 2015; Snyder et al., 2015). In general, studies 

suggest that impacts are spatiotemporally limited and that fishes have experienced a reduced incidence of 

oil-related effects over time; however, accumulations in some species indicate continued exposure, 

potentially resulting in long-term effects. This information serves to expand our understanding of the 

potential impacts an oil spill may have on valuable marine species. A review of literature by Fodrie et al.

(2014) examines the recent evidence of oil-related impacts on fishes and the lack of detectable 

population-level effects. This review proposes mechanisms that could explain the apparent discrepancy, 

such as masking by biological and environmental factors, natural population variability, other 

anthropogenic disturbances, and compensatory processes. This analysis supports previous conclusions 

reached by BOEM and suggests research that could improve future assessment efforts.

Overall, the newly available information supports and reaffirms the conclusions reached in the prior 

2012-2017 Gulf of Mexico EISs. Therefore, the analysis and potential impacts discussed in those NEPA

documents still apply for proposed CPA Lease Sale 247. 

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. BOEM has identified incomplete information regarding impacts 

of the Deepwater Horizon explosion, oil spill, and response or other oil exposure on commercially 

valuable fish resources in the CPA. This incomplete information may be relevant to evaluating adverse 

effects because the full extent of long-term adverse impacts to fishes from acute and chronic exposure to 

oil are not known. Relevant data on the potential impacts to fishes after the Deepwater Horizon

explosion, oil spill, and response may take years to acquire and analyze. Therefore, it is not possible for

BOEM to obtain this information within the timeline contemplated in the NEPA analysis of this 

Supplemental EIS, regardless of the cost or resources needed.

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing this analysis and formulating the conclusions presented here. Although the body of available 

information is incomplete and the long-term effects cannot yet be known, the evidence currently available 

supports past analyses and is not indicative of significant population-level responses. Therefore, BOEM 

has determined that the incomplete information is not essential to a reasoned choice among alternatives. 

Additional information on fish resources and EFH, and recreationally valuable species can be found in 

Chapters 4.1.1.18 and 4.1.1.20, respectively.

Summary and Conclusion

BOEM has reexamined the analysis for commercial fisheries presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented above. No new significant information was 

discovered that would alter the impact conclusion for commercial fisheries presented in those NEPA

documents because of the available scientifically credible evidence in this analysis and based upon 

accepted scientific methods and approaches. The analysis and potential impacts discussed in those 

documents still apply for proposed CPA Lease Sale 247. 
Description of the Environment and Impact Analysis 4-79

4.1.1.20. Recreational Fishing

BOEM has reexamined the analysis for recreational fishing presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented below. No new information was discovered 

that would alter the impact conclusion for recreational fishing presented in those NEPA documents. The 

analyses and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 

247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.20 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.20 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.20 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

Impacts of Routine Activities and Accidental Events

Activities during the initial phases of the CPA proposed action, such as seismic surveying operations 

and other forms of vessel traffic, may lead to some space-use conflicts with recreational fishermen. 

Vessel traffic during subsequent infrastructure emplacement and production operations could also lead to 

some space-use conflicts with recreational fishing activities. The OCS oil- and gas-related activities 

could also affect the aesthetics of fishing in a particular location, which could dissuade anglers from 

fishing in specific locations. Some activities arising from proposed CPA Lease Sale 247, such as 

construction activities and discharges of muds and produced water, may also lead to low-level 

environmental degradation of fish habitat (Chapter 4.1.1.18), which would negatively impact 

recreational fishing activity. However, these minor negative effects would likely be outweighed by the 

beneficial addition of hard substrate and complex habitat provided by oil and gas infrastructure. The level 

of participation in any particular State Rigs-to-Reefs program will be an important determinant of the 

long-term impact of the CPA proposed action on recreational fishing activity. As structures are scheduled 

for decommissioning, a higher level of participation may benefit fishermen through the retention of 

complex habitat and potentially enhanced production for some recreationally desirable species, as 

opposed to structure removals (particularly those that use explosives) that can negatively impact the 

recreational activity that depends on any particular platform. In aggregate, the impacts of the CPA 

proposed action on recreational fishing activity are expected to be minor.

Oil spills can arise from accidents with respect to vessels, pipelines, drilling operations, or production 

operations. An oil spill would likely lead to recreational fishing closures in the vicinity of the oil spill. 

Small-scale spills should not affect recreational fishing to a large degree due to the likely availability of 

substitute fishing sites in neighboring regions. The longer-term effects of an oil spill will be determined 

by its effects on fish populations (Chapter 4.1.1.18), as well as by its effects on people and firms that 

support recreational fishing activity. Some of these effects will be similar to the effects on species that 

are important to commercial fishing activity, which are discussed in Chapter 4.1.1.19. 

Cumulative Impacts 

The cumulative analysis considers the effects of impact-producing factors related to OCS oil and gas, 

along with non-OCS oil- and gas-related impacts that may occur and adversely affect recreational fishing

in the same general area of the CPA proposed action. The proposed CPA lease sale will contribute to the 

impacts of the broader OCS Program. This includes the space-use impacts arising from vessel traffic and 

construction operations, as well as the low-level environmental degradation to fish habitats that could 

occur. The proposed CPA lease sale will also incrementally add to the probabilities of oil spills, which 

could affect recreational fishing activity in the short term. Low-probability catastrophic oil spills, which 

are not part of the CPA proposed action and not likely expected to occur, could also impacts recreational 

fishing and are described in Appendix B. The proposed CPA lease sale could also have positive impacts 

to recreational fishing activity since OCS oil and gas platforms often serve as reefs for fish populations, 

although removals of these platforms could have negative impacts on recreational fishing activity. 
4-80 Central Planning Area Lease Sale 247 Supplemental EIS

However, these negative effects would be partially offset if some platforms are redeployed as artificial 

reef substrate through Rigs-to-Reefs programs.

Recreational fishing activity could also be influenced by a number of non-OCS oil- and gas-related 

factors, such as commercial, military, recreational, and industrial activities; natural processes; wetlands

loss; hypoxia events; fish kills; water quality degradation; fisheries management plans; hurricanes; State 

oil and gas activities; State artificial reef programs; tourism (refer to Chapter 4.1.1.21); and other 

economic factors (refer to Chapter 4.1.1.23.3). Many of these impacts will be determined by the 

cumulative impacts to fish populations, which are discussed in Chapter 4.1.1.18. However, recreational 

fishing activity is driven by unique economic and tourism trends (refer to Chapters 4.1.1.21 and 

4.1.1.23.3). It can also be influenced by the quality of fishing grounds, such as wetland areas, which can 

be degraded by hurricanes. Military activities, recreational vessel traffic, and other forms of vessel traffic 

could also cause space-use conflicts with recreational fishermen. However, it is likely that Fisheries 

Management Plans of the Federal and State governments would serve to keep overall recreational fishing 

activity reasonably stable through time. The incremental contribution of the CPA proposed action to 

these positive and negative cumulative impacts would be minimal because of the relatively small amount 

of activity expected with the CPA proposed action. 

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

BOEM examined a variety of Internet sources, as well as known data providers, for new information 

regarding the impacts of the CPA proposed action on recreational fishing. Ajemian et al. (2015) analyzed 

the fish populations at operational platforms, decommissioned platforms that were reefed using a variety 

of methods, and liberty ship reefs offshore Texas. This study found that recreationally important species 

such as red snapper (Lutjanus campechanus) were prevalent among all types of platform structures, 

suggesting that the reefing of a platform could maintain some of the properties desired by recreational 

fishermen. Hutt et al. (2015) presents baseline information regarding the economic contributions of bait 

and tackle stores in the Gulf of Mexico, which improves BOEM’s understanding of the affected 

environment for recreational fishing. For example, this study finds that $266 million in bait and tackle 

sales support $160 million in labor income and 4,402 jobs, which provides insights regarding the affected 

environment for recreational fishing. Finally, the Gulf of Mexico Fishery Management Council (2015) 

summarized the most recent recreational fishing regulations in the Gulf of Mexico. For example, this 

document describes the recreational fishing seasons for red snapper (Lutjanus campechanus), red grouper 

(Epinephelus morio), and greater amberjack (Seriola dumerili).

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the impact conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is 

still incomplete or unavailable information related to recreational fishing related to the Deepwater

Horizon explosion, oil spill, and response. This incomplete information may be relevant to evaluating 

adverse effects because the full extent of the potential cumulative impacts on recreational species arising 

from the Deepwater Horizon explosion, oil spill, and response are not known. This information relates to 

the ultimate impacts of the Deepwater Horizon explosion, oil spill, and response on fish populations that 

support recreational fishing activity. This information is relevant because it would allow BOEM to more 

accurately estimate the scales of recreational fishing activity in future time periods. Much of this 

information is being developed through the NRDA process and is not yet available. There is also 

uncertainty regarding the extent to which recreational fishing is dependent upon OCS oil and gas 

platforms. BOEM is planning to undertake a study project to examine this issue, although the results 

from this study project will not be released within the timeline contemplated in the NEPA analysis of this 

Supplemental EIS. 

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing this analysis and formulating the conclusions presented here. For example, BOEM has used 

data on recreational fishing activity provided by NMFS, which allowed BOEM to examine trends in 

recreational fishing over time. BOEM does not expect the missing information to significantly change its 
Description of the Environment and Impact Analysis 4-81

estimates of the impacts of the OCS Program on recreational fishing activity because BOEM still has 

enough baseline data to reasonably estimate impacts. Therefore, BOEM has determined that the 

incomplete or unavailable information is not essential to a reasoned choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for recreational fishing presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented above. No new information was discovered 

that would alter the impact conclusion for recreational fishing presented in the prior 2012-2017 Gulf of 

Mexico EISs because of the available scientifically credible evidence in this analysis and based upon 

accepted scientific methods and approaches. The analysis and potential impacts discussed in those 

documents still apply for proposed CPA Lease Sale 247. 

4.1.1.21. Recreational Resources

BOEM has reexamined the analysis for recreational resources presented in the prior 2012-2017 Gulf 

of Mexico EISs based on the additional information presented below. No new significant information 

was discovered that would alter the impact conclusion for recreational resources presented in those NEPA

documents. The analysis and potential impacts discussed in those documents still apply for proposed 

CPA Lease Sale 247.

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.21 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.21 of the WPA 233/CPA 231 Supplemental EIS, Chapter 4.1.1.21 of the CPA 

235/241/247 Supplemental EIS, and Chapter 4.1.1.21 of the CPA 241/247 and EPA 226 Supplemental 

EIS. The following information is a summary of the resource description and impact analysis 

incorporated from those NEPA documents. Any new information that has become available since those 

documents were published is presented below. 

Impacts of Routine Activities and Accidental Events

Routine OCS oil- and gas-related activities in the CPA can cause various disturbances to recreational 

resources. For example, marine debris can noticeably affect the aesthetic value of coastal areas,

particularly beaches. Many mitigating measures have been adopted and incorporated into regulations 

and/or guidelines governing OCS oil and gas exploration, development, and production activities. 

Regulations and NTLs include safeguards and protective measures, which are in place to reduce impacts 

of marine trash and debris and other impact-producing factors associated with OCS oil- and gas-related 

activities. Vessel noise and the visibility of OCS oil and gas infrastructure can also conflict with some 

recreational activities. Similarly, vessel traffic can cause space-use conflicts with recreational activities. 

The OCS oil- and gas-related activities can also change the composition of local economies through 

changes in employment, land use, and demand for activities related to recreation and tourism. The 

presence of OCS oil and gas platforms can enhance some recreational activities such as fishing and 

diving, although the removal of a platform at decommissioning could reduce recreational opportunities. 

However, the small scale of the CPA proposed action relative to the scale of the existing oil and gas 

industry suggests that these potential impacts on recreational resources are likely to be minimal.

The NPS has raised concerns about impacts to national parks located along the Gulf Coast. Economic 

benefits associated with these national parks have been evaluated in Cullinane-Thomas et al. (2015). The 

number of visitors and the amount of visitor spending supported by each national park along the Gulf 

Coast are as follows: Padre Island National Seashore (Texas) (578,814 visitors; $23,892,700); Jean 

Lafitte National Historical Park and Preserve (Louisiana) (445,524 visitors; $24,986,300); Gulf Islands 

National Seashore (Mississippi and Florida) (4,455,240 visitors; $185,611,000); De Soto National 

Memorial (Florida) (342,039 visitors; $19182,600); Big Cypress National Preserve (Florida) 

(1,192,856 visitors; $91,111,200); Everglades National Park (Florida) (1,110,900 visitors; $104,476,500); 

and Dry Tortugas National Park (Florida) (64,865 visitors; $3,783,600). 

The NPS has voiced specific concerns regarding noise impacts of OCS oil- and gas-related activities. 

The NPS cited White (2014), which provides data on baseline noise levels at Horn and Petit Bois Islands 

relative to Fort Pickens. Horn and Petit Bois Islands have higher measures of watercraft noise and lower 
4-82 Central Planning Area Lease Sale 247 Supplemental EIS

levels of aircraft noise than Fort Pickens. The study also found that Horn and Petit Bois Islands have 

higher levels of noise at night than during the day, while Fort Pickens has more noise during the day than 

at night. The study results did not differentiate between OCS oil- and gas-related noise and other 

anthropogenic noise. The NPS also voiced concerns regarding the night lighting of OCS structures. The 

NPS provided BOEM with data regarding the overall scales of natural and anthropogenic light at Horn 

and Petit Bois Island. These data found that the anthropogenic light ratio is 537 percent higher than 

average natural conditions at Horn Island and 510 percent higher than average natural conditions at Petit 

Bois Island (Brown, official communication, 2014). 

During scoping for recent EISs, the NPS raised questions regarding the potential visual impacts from 

OCS platforms to Horn and Petit Bois Islands. Horn and Petit Bois Islands are federally designated 

wilderness areas and are sensitive to disruptions to nature experiences. Figure 4-2 presents information 

regarding the current and historical locations of structures in the vicinity of Horn and Petit Bois Islands. 

There are currently nine producing platform complexes (i.e., fixed platforms and caissons) within 7-15 mi 

(11-24 km) of the Gulf Islands National Seashore offshore the States of Louisiana, Mississippi, and 

Alabama (Figure 4-2). Some OCS platforms are visible on the horizon. Numerous OCS structures and 

wells have existed within 3-7 mi (5-11 km) of Petit Bois Island over the years. Most of these have been 

removed; a few structures remain 7-10 mi (11-16 km) away. No studies have analyzed the impacts of the 

historical OCS structures on visitor experiences. Figure 4-3 is a photograph of the remaining OCS 

structures taken from Petit Bois Island. Figure 4-3 also shows a ship passing through the major shipping 

fairway near Petit Bois Island; the location of this shipping fairway is shown in Figure 4-2. This 

shipping fairway will continue to be used regardless of the CPA proposed action. In Figure 4-3, the 

platforms are barely visible and have less of an impact on the viewshed than the passing ship.

An analysis of the visual impacts of the CPA proposed action depends importantly on the locations of 

the structures likely to arise. Given the low resource potential offshore Mississippi, as well the low 

current prevailing energy prices, it is unlikely that a production structure would arise from the CPA 

proposed action. In the unlikely event of a lease near Horn or Petit Bois Island, it would probably be 

developed using minimal structures that tie back to existing platforms due to cost considerations. In 

addition, BOEM developed the ITL that provides for NPS consultation on a lessee’s plans (excerpt from 

the ITL is below), as appropriate, and began adding the ITL to the Notices of Sale for proposed CPA 

lease sales beginning with CPA Lease Sale 231. The lease blocks that would be subject to the Gulf 

Islands National Seashore’s ITL are illustrated in Figure 4-4. The ITL states the following:

(q) Gulf Islands National Seashore. Potential bidders are hereby notified that postlease 

plans submitted by lessees of whole and partial lease blocks located within the first 12 

miles of Federal waters near the Gulf Islands National Seashore (State of Mississippi 

Barrier Island Chain Map, enclosed with ITL) may be subject to additional review in 

order to minimize visual impacts from development operations on these blocks. BOEM 

will review and make decisions on a lessee’s plans for these blocks in accordance with 

applicable Federal law and regulations, and BOEM policies, to determine if visual 

impacts are expected to cause serious harm and if any additional mitigative action is 

required. Mitigations may include, but are not limited to, requested changes in location, 

modifications to design or direction of proposed structures, pursuing joint use of existing 

structures on neighboring blocks, changes in color design, or other plan modifications. 

BOEM may consult with the State of Mississippi and/or the State of Alabama and with 

the National Park Service, Southeast Regional Office, during such reviews as appropriate.

The following whole and partial blocks are specifically identified for this ITL: Chandeleur Area – 1; 

Mobile – 765-767, 778, 779, 809-823, 853-867, 897-910, 942-954, and 987-997; and Viosca Knoll – 

24-27. 

BOEM would expect this ITL to be applied to proposed CPA Lease Sale 247. For these reasons, 

potential impacts to these islands would likely be negligible to minor.

Accidental events that could result from the CPA proposed action will be small, of short duration, and 

not likely to impact Gulf Coast recreational resources. Should an oil spill occur and contact a beach area 

or other recreational resource, it will cause some disruption during the impact and cleanup phases of the 

spill. Beaches, nature parks, and wetland areas could be impacted during these phases of a spill. 

Disruptions to beaches, nature parks, and wetland areas could also have impacts on firms and consumers 
Description of the Environment and Impact Analysis 4-83

that depend on the use of these resources. Media coverage and public perception regarding the extent of 

the oil damage can also influence the ultimate economic impacts of the spill. The economic impacts of a 

spill would be mitigated to some extent if a legal damage claims process were to be implemented 

subsequent to an oil spill. However, all of these effects would likely be small in scale and of short 

duration. A catastrophic oil spill, however, would likely have larger impacts on recreational resources; 

these impacts are discussed in Appendix B. A catastrophic spill is not part of the CPA proposed action

and is not likely expected to occur. This analysis of impacts is based on historical leasing patterns as well 

as the subsequent review process called for in BOEM’s Information to Lessees and Operators regarding 

the Gulf Islands National Seashore.

Cumulative Impacts 

The cumulative analysis considers the effects of impact-producing factors related to OCS oil and gas 

along with non-OCS oil- and gas-related impacts of other commercial, military, offshore, and coastal 

activities, and natural processes that may occur and adversely affect recreational resources in the same 

general area of the CPA proposed action.

The CPA proposed action would contribute to the aesthetic impacts and space-use conflicts that arise 

due to the broader OCS Program. This includes impacts from vessel traffic, marine debris, and the 

presence or absence of OCS oil- and gas-related infrastructure. Vessel traffic can cause space-use 

conflicts with recreational activities such as boating. Marine debris can degrade the recreational value of 

resources such as beaches. The presence or absence of OCS oil- and gas-related infrastructure could 

impact activities such as recreational fishing or diving. Oil spills could also contribute to the overall 

degradation of beach and wetland-based recreational resources. Most accidental spills are not likely to 

impact Gulf Coast recreational resources because they are expected to be small and of short duration 

(refer to Chapter 3.2.1). If oil resulting from a spill were to contact a beach area or other recreational 

resource, disruption could occur from oiling and oil cleanup. However, these effects are also likely to be 

small in scale and of short duration. The impacts of a low-probability catastrophic oil spill, which is not 

part of the CPA proposed action and not likely expected to occur, on recreational resources are discussed 

in Appendix B. 

Recreational resources along the Gulf Coast can also be impacted by non-OCS oil- and gas-related 

aesthetic and space-use conflicts, as well as a variety of other factors, such as coastal erosion, beach 

disruptions, and economic factors. However, the incremental contribution of the CPA proposed action is 

expected to be minimal in light of all OCS oil- and gas-related and non-OCS oil- and gas-related 

activities. This is because of the small scale of the CPA proposed action, as well as the fact that most 

impacts to recreational resources will be temporary.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS and CPA 

241/247 and EPA 226 Supplemental EIS 

BOEM conducted a search of Internet sources and of known data providers for new information 

regarding recreational resources. BOEM has incorporated a new methodology for defining the scales of 

recreation and tourism in the Gulf of Mexico that applies data from IMPLAN Group LLC (2015) to the 

methodologies developed in Nadeau et al. (2014). This methodology allows for more detailed 

examinations of which industries support recreation and tourism. The use of IMPLAN data allows 

BOEM to overcome the disclosure issues in certain industries and counties associated with other data 

sources. Nadeau et al. (2014) defined which industries comprise recreation and tourism, and estimated 

the percentage of each industry that supports tourism. For example, the hotel industry is primarily 

supported by tourists, while the restaurant industry is supported by tourists and local residents. Table 4-2

presents estimates of the employment and value-added supported by recreation and tourism in BOEM’s 

Economic Impact Areas (EIAs). The areas with the largest recreation and tourism industries are TX-3 

(which includes Houston and Galveston), LA-6 (which includes New Orleans), and various EIAs along 

the Florida coast. Parts of coastal Mississippi and Alabama also have sizeable recreational economies 

supported by parks, beaches, and casinos. 
4-84 Central Planning Area Lease Sale 247 Supplemental EIS

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. In particular, the visual impacts that will arise due to site-specific 

offshore oil and gas activities are not fully known. BOEM has determined that such information is not 

essential to a reasoned choice among alternatives because much of this uncertainty relates to the inherent 

uncertainty regarding where and what types of structures will arise from the CPA proposed action. In 

addition, existing information allows for sufficient estimates of the overall dependence of visual impacts 

to factors such as distance, height, brightness, and general location. BOEM used generally accepted 

scientific principles to estimate the visual impacts of the CPA proposed action, including literature 

sources, data sources, and photographic evidence. BOEM has issued an ITL to ensure that visual impacts 

near the Gulf Islands National Seashore will be addressed at BOEM’s site-specific review stage.

Summary and Conclusion

BOEM has reexamined the analysis for recreational resources presented in the prior 2012-2017 Gulf 

of Mexico EISs based on the additional information presented above. No new significant information 

was discovered that would alter the impact conclusion for recreational resources presented in those NEPA

documents because the new information was roughly consistent with prior expectations. The analysis and 

potential impacts detailed and updated in those documents still apply for proposed CPA Lease Sale 247. 

4.1.1.22. Archaeological Resources

4.1.1.22.1. Historic Archaeological Resources

BOEM has reexamined the analysis for historic archaeological resources presented in the prior 2012-

2017 Gulf of Mexico EISs based on the additional information presented below. No new significant 

information was discovered that would alter the impact conclusion for historic archaeological resources 

presented in those NEPA documents. The analysis and potential impacts discussed in those documents 

still apply for proposed CPA Lease Sale 247.

Historic archaeological resources on the OCS consist of historic shipwrecks and a single historic 

lighthouse, the Ship Shoal Light. A historic shipwreck is defined as a submerged or buried vessel or its 

associated components, at least 50 years old, that has foundered, stranded, or wrecked, and that is 

currently lying on or embedded in the seafloor. Ships are known to have traversed the waters of the CPA 

as early as Captain Alonso Alverez de Piñeda’s expedition in 1519. 

A detailed description of the affected environments and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.22.1 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.22.1 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.22.1 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. BOEM has found no significant new information that has become available since publication 

of those NEPA documents. 

Impacts of Routine Activities and Accidental Events

Routine impact-producing factors associated with the CPA proposed action that could impact historic 

archaeological resources include direct physical contact with a shipwreck site; the placement of drilling 

rigs and production systems on the seafloor; pile driving associated with platform emplacement; dredging 

of new channels, as well as maintenance dredging of existing channels; anchoring activities; pipeline

installation and maintenance; post-decommissioning platform removal and trawling clearance; and the 

masking from geophysical sensors of archaeological resources from industry-related debris.

The greatest potential impact to an archaeological resource as a result of the CPA proposed action 

would result from direct contact between an offshore activity (e.g., platform installation, drilling rig 

emplacement, and dredging or pipeline project) and a historic site because of incomplete knowledge of 

the location of these sites in the Gulf. The risk of contact to archaeological resources is greater in 
Description of the Environment and Impact Analysis 4-85

instances where archaeological survey data are inadequate or unavailable. Such an event could result in 

the disturbance or destruction of important archaeological information. Archaeological surveys provide 

the necessary information to develop avoidance strategies that reduce the potential for impacts on 

archaeological resources.

Damage to archaeological resources from offshore oil and gas activity can be minimized by 

conducting archaeological surveys before seabed disturbance occurs. Archaeological surveys, where 

required prior to an operator beginning OCS oil- and gas-related activities on a lease, are expected to be 

effective at identifying possible archaeological sites. The technical requirements of the archaeological 

resource reports are detailed in NTL 2005-G07, “Archaeological Resource Surveys and Reports.” Under 

30 CFR § 550.194(c) lessees are required to immediately halt operations and notify BOEM’s Regional 

Director of the discovery of any potential archaeological resources. Under 30 CFR § 250.194(c) and 

30 CFR § 250.1010(c), lessees are also required to immediately halt operations and notify BSEE’s 

Regional Director of the discovery of any potential archaeological resources.

Except for the projection of up to one new gas processing facility and up to one new pipeline landfall, 

the CPA proposed action would require no new oil and gas coastal infrastructure. It is expected that 

archaeological resources would be protected through the review and approval processes of the various 

Federal, State, and local agencies involved in permitting onshore activities.

Impacts to documented and undocumented historic archaeological resources could occur as a result of 

an accidental oil spill and the associated cleanup operations. Detailed risk analyses of offshore oil spills 

ranging from <1,000 bbl to ≥1,000 bbl and coastal spills associated with the CPA proposed action are 

provided in Chapters 3.2.1.5, 3.2.1.6, and 3.2.1.7. When oil is spilled in offshore areas, much of the oil 

volatilizes or is dispersed by currents, so it has a low probability of contacting coastal areas. However, 

should a spill contact a historic archaeological site (including submerged sites), damage might include 

contamination of materials, direct impact from oil-spill cleanup equipment, and/or looting. An additional 

major effect from an oil spill could be viewshed pollution of a historic coastal site, such as a fort or 

lighthouse. Although such effects may be temporary and reversible, cleaning oil from historic structures 

can be a complex, time-consuming, and expensive process, and the use of dispersants may result in longterm chemical contamination of submerged cultural heritage sites (e.g., Chin and Church, 2010). As of 

the publication of this Supplemental EIS, there are no published studies documenting or analyzing the 

long-term effects of oil or dispersant contamination on submerged archaeological sites. It is expected, 

however, that any spill cleanup operations would be considered a Federal undertaking for the purposes of 

Section 106 of the National Historic Preservation Act (54 U.S.C. § 300101 et seq.) and would be 

conducted in such a way as to minimize impacts to historic archaeological resources.

Cumulative Impacts 

Several OCS oil- and gas-related cumulative impact-producing factors could potentially impact 

historic archaeological resources, including the following: (1) OCS Program routine and accidental 

impacts; (2) artificial rigs-to-reefs development; and (3) renewable energy and alternative use 

conversions. Historic archaeological resources on the OCS are vulnerable to OCS oil- and gas-related 

cumulative impact-producing factors due to the associated bottom-disturbing activities. An impact could 

result from direct physical contact between historic shipwrecks located on the OCS and OCS Program oil 

and gas activities (i.e., pipeline and platform installations, drilling rig emplacement and operation, site 

decommissioning, rigs-to-reefs development, dredging, and anchoring activities). Permitting OCS oiland gas-related development prior to requiring archaeological surveys has been documented to have 

impacted wrecks containing significant or unique historic information. Impacts may be reduced when 

preconstruction surveys are required by BOEM or the permitting agency prior to these activities. Impacts 

to historic resources may still occur in areas where a remote-sensing survey fails to resolve the location of 

partially or completely buried resources or when no pre-disturbance survey is required. Impacts to 

documented and undocumented historic archaeological resources could occur as a result of an accidental 

oil spill and the associated cleanup operations; however, the potential for spills is low, the effects would 

generally be localized, and the cleanup efforts would be regulated. Low-probability catastrophic spills, 

which are not part of the CPA proposed action and not likely expected to occur, are discussed in 

Appendix B. 

Non-OCS oil- and gas-related cumulative impact-producing factors that could potentially impact 

historic archaeological resources include the following: (1) State oil and gas activity; (2) offshore LNG 
4-86 Central Planning Area Lease Sale 247 Supplemental EIS

projects; (3) new channel dredging and maintenance dredging; (4) State renewable energy and alternative 

use conversions; (5) State artificial reefs and rigs-to-reefs development; (6) commercial fishing; (7) sport 

diving and commercial treasure hunting; and (8) natural processes, including wave action and hurricanes. 

As with the OCS oil- and gas-related cumulative impact-producing factors, risks from the above non-OCS 

oil- and gas-related cumulative impact-producing factors are related to their associated bottom-disturbing 

activities. An impact could result from direct physical contact between historic shipwrecks and Staterelated oil and gas activities, sand borrowing, renewable energy activities, LNG facility construction, 

artificial reef creation, new channel dredging, and maintenance dredging. With the exception of 

maintenance-dredging, preconstruction surveys may be required for these activities. Impacts to historic 

archaeological resources may still occur in areas where a remote-sensing survey fails to resolve the 

location of partially or completely buried resources or when no pre-disturbance survey is required. 

The effects of the various impact-producing factors discussed in this analysis have likely resulted in 

the localized loss of significant or unique historic archaeological information. In the case of factors 

related to OCS Program activities within the cumulative activity area, it is reasonable to assume that most 

impacts would have occurred where development occurred prior to any archaeological survey 

requirements. The incremental contribution of the CPA proposed action is expected to be very small due 

to the efficacy of remote-sensing surveys and archaeological reports where required. Future OCS 

Program activities and the bottom-disturbing activities permitted by BOEM and other agencies may 

require preconstruction archaeological surveys that, when completed, are highly effective in identifying 

bottom anomalies that could be avoided or investigated before bottom-disturbing activities begin. When 

surveys are not required, it is impossible to anticipate what might be embedded in or lying directly on the 

seafloor, and impacts to these sites are likely to be major in scale. Despite diligence in site-clearance 

survey reviews, there is still the possibility of an unanticipated interaction between bottom-disturbing 

activity (e.g., rig emplacement, pipeline trenching, anchoring, and other ancillary activities) and a historic 

shipwreck.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

Various Internet sources were examined to assess recent information regarding impacts to 

archaeological resources or potential new threats to archaeological resources that may be pertinent to the 

CPA. These Internet sources included online indexes to periodical literature, such as JSTOR, the 

National Technical Information Service’s National Technical Reports Library, and ScienceDirect. This 

search did not identify any new information that would be pertinent to the analysis of the potential 

impacts of OCS oil- and gas-related activities on historic archaeological resources.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the conclusions from the 

prior 2012-2017 Gulf of Mexico EISs are still valid. No new significant information has been identified 

since those NEPA documents were published that would alter those documents’ conclusions on impacts 

to historic archaeological resources from the CPA proposed action. Nevertheless, there is still incomplete 

or unavailable information regarding the long-term effects of oil and/or dispersant contamination on, and 

the location of, historic archaeological resources in the CPA. As discussed above, there are currently no 

published studies on the long-term effects to historic archaeological resources exposed to oil or dispersant 

contamination. Such information is unlikely to be available prior to proposed CPA Lease Sale 247; 

therefore, considering the low probability of an accidental oil spill contacting an archaeological site as a 

result of the CPA proposed action, BOEM has determined that the incomplete or unavailable information 

is not essential to a reasoned choice among alternatives.

Additionally, the locations of historic archaeological resources in the CPA cannot be determined 

because the overall costs of obtaining that information through survey of the entire CPA are exorbitant. 

This incomplete information may be relevant to adverse effects because the locations and integrity of 

many historic archaeological resources remain unknown. Nevertheless, this incomplete information is not 

likely to be available within the timeline contemplated in the NEPA analysis of this Supplemental EIS. It 

would take several years before data confirming the presence (or lack thereof) of historic archaeological 
Description of the Environment and Impact Analysis 4-87

resources, and the status of each, could be investigated, analyzed, and compiled. Historic archaeological 

sites within the CPA region have the potential to be buried, embedded in, or laying on the seafloor. The 

CPA covers an area of 66,446,351 ac and ranges in water depths from an estimated 3 to 3,475 m (10 to 

11,401 ft). It includes highly variable bathymetric and geophysical regimes, which differentially affect 

the ease and ability to identify, verify, and evaluate historic archaeological sites. This fact, combined 

with the scope of the acreage within the CPA, results in the aforementioned exorbitant costs and time 

factors.

BOEM used reasonably accepted scientific theories on archaeological site potential in the Gulf of 

Mexico to extrapolate from existing survey data in completing the relevant analysis and formulating the 

conclusions presented here. In addition, site-specific, remote-sensing surveys of the seafloor will be 

required when deemed appropriate to establish the presence of potential resources (NTL 2005-G07). The 

results of these surveys are reviewed in tandem with credible scientific evidence from previously 

identified sites, regional sedimentology, and physical oceanography that is relevant to evaluating the 

adverse impacts on historic resources that are a part of the human environment. The required surveys are 

analyzed by industry and BOEM archaeologists prior to the authorization of any new or significant 

bottom-disturbing impacts and, if necessary, avoidance of potential archaeological resources is 

prescribed. Archaeological surveys are expected to be highly effective in identifying resources to allow 

for the protection of the resource during OCS oil- and gas-related activities. The CPA proposed action is 

not expected to have a reasonably foreseeable significant impact because BOEM’s evaluation of such 

impacts is based upon pre-disturbance and site-specific surveys, the results of which BOEM uses to 

require substantial avoidance of any potential historic resource that could be impacted by the CPA 

proposed action. Therefore, BOEM has determined that the information is not essential to a reasoned 

choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for historic archaeological resources presented in the prior 2012-

2017 Gulf of Mexico EISs. No new significant information was discovered that would alter the impact 

conclusion for historic archaeological resources presented in those NEPA documents because of the 

available scientifically credible evidence in this analysis and based upon accepted scientific methods and 

approaches. The analysis and potential impacts discussed in those documents still apply for proposed 

CPA Lease Sale 247.

4.1.1.22.2. Prehistoric Archaeological Resources

BOEM has reexamined the analysis for prehistoric archaeological resources presented in the prior 

2012-2017 Gulf of Mexico EISs based on the additional information presented below. No new 

significant information was discovered that would alter the impact conclusion for prehistoric 

archaeological resources presented in those NEPA documents. The analysis and potential impacts 

discussed in those documents still apply for proposed CPA Lease Sale 247.

Prehistoric archaeological resources are any material remains of human life or activities associated 

with the earliest inhabitants of the Gulf Coast, predating European discovery and exploration of the area. 

Available evidence suggests that the first Americans arrived on the Gulf Coast as much as 12,000 years 

B.P. (before present) during a time when the continental shelf was exposed above sea level and open to 

habitation (Pearson et al., 1986). Prehistoric archaeological sites are thought to be preserved shoreward 

of the 45-m (148-ft) bathymetric contour, where the Gulf of Mexico continental shelf was subaerially 

exposed during the Late Pleistocene. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.22.2 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.22.2 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.22.2 of the 

CPA 235/241/247 Supplemental EIS and CPA 2341/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. BOEM has found no significant new information that has become available since publication 

of those documents.
4-88 Central Planning Area Lease Sale 247 Supplemental EIS

Impacts of Routine Activities and Accidental Events

Routine impact-producing factors associated with the CPA proposed action that could impact 

prehistoric archaeological resources include direct physical contact associated with the placement of 

drilling rigs and production systems on the seafloor; pile driving associated with platform emplacement; 

dredging of new channels, as well as maintenance dredging of existing channels; anchoring activities; 

pipeline installation and maintenance; and post-decommissioning platform removal and trawling 

clearance. This direct physical contact with a site could destroy fragile artifacts or site features and could 

disturb artifact provenance and site stratigraphy. The result would be the loss of archaeological data on 

prehistoric migrations, settlement patterns, subsistence strategies, and archaeological contexts for North 

America, Central America, South America, and the Caribbean. 

Archaeological survey and archaeological clearance of sites, where required prior to an operator 

beginning oil and gas activities on a lease, are expected to be somewhat effective at identifying 

submerged landforms that could support archaeological sites. While surveys, where required, provide a 

reduction in the potential for a damaging interaction between an impact-producing factor and a prehistoric 

archaeological site, there is a possibility of an OCS oil- and gas-related activity contacting an 

archaeological site because of an insufficiently dense survey grid. Should such contact occur, there 

would be damage to or loss of significant and/unique archaeological information. The risk of contact to 

archaeological resources is greater in instances where archaeological survey data are inadequate or 

unavailable. Archaeological surveys provide the necessary information to develop avoidance strategies 

that reduce the potential for impacts on archaeological resources.

Except for the projection of up to one new gas processing facility and up to one new pipeline landfall, 

the CPA proposed action would require no new oil and gas coastal infrastructure. It is expected that the 

protection of archaeological resources would be maximized through the review and approval processes of 

the various Federal, State, and local agencies involved in permitting onshore activities.

Impacts to documented and undocumented prehistoric archaeological resources could occur as a 

result of an accidental oil spill and the associated cleanup operations. Oil spills resulting from a loss of 

well control in the CPA and related spill-response activities have the potential to impact cultural resources 

near the spill site and landfall areas. Detailed risk analyses of offshore oil spills ranging from <1,000 bbl

to ≥1,000 bbl and coastal spills that may be associated with the CPA proposed action is provided in 

Chapters 3.2.1.5, 3.2.1.6, and 3.2.1.7 of this Supplemental EIS and Chapters 3.2.1.5, 3.2.1.6, and 3.2.1.7 

of the 2012-2017 WPA/CPA Multisale EIS. Should a spill contact a prehistoric archaeological site, 

damage might include loss of radiocarbon-dating potential, direct impact from oil-spill cleanup 

equipment, and/or looting. There is currently no published information documenting or analyzing the 

long-term effects of oil or dispersant contamination on prehistoric archaeological sites. Previously 

unrecorded sites could be impacted by oil-spill cleanup operations on beaches. However, when oil is 

spilled in offshore areas, much of the oil volatilizes or is dispersed by currents, so it has a low probability 

of contacting coastal and barrier island prehistoric sites as a result of the CPA proposed action. The CPA 

proposed action, therefore, is not expected to result in impacts to prehistoric archaeological sites due to an 

accidental oil spill.

Cumulative Impacts 

The OCS oil- and gas-related activities that could potentially impact prehistoric archaeological sites 

located on the OCS through contact include pipeline and platform installations, drilling rig emplacement 

and operation, site decommissioning, rigs-to-reefs development, dredging, and anchoring activities. 

Preconstruction surveys may be required by BOEM or the lead permitting agency prior to these activities. 

Impacts to prehistoric resources may still occur in areas where a remote-sensing survey fails to resolve the 

location of partially or completely buried resources or when no pre-disturbance survey is required. 

Development onshore as a result of the CPA proposed action could result in the direct physical contact 

between a prehistoric site and pipeline trenching. It is assumed that archaeological investigations prior to 

construction will serve to mitigate these potential impacts. Oil spills have the potential to impact coastal 

prehistoric sites directly or indirectly by physical impacts caused by oil-spill cleanup operations. The 

number and most likely spill sizes to occur in coastal waters in the future are expected to resemble the 

patterns that have occurred in the past, as long as the level of oil- and gas-related commercial and 

recreational activities remain the same. Low-probability catastrophic spills, which are not part of the 
Description of the Environment and Impact Analysis 4-89

proposed action and not likely expected to occur, could also contact coastal prehistoric sites, and the 

effects of a spill that size would likely result in longer-lasting impacts that take longer to mitigate. 

Accidental spills as a result of a low-probability, catastrophic spill are discussed in Appendix B. 

Non-OCS oil- and gas-related cumulative impact-producing factors that could potentially impact 

prehistoric archaeological resources including the following: (1) State oil and gas activity; (2) new 

channel dredging and maintenance dredging; (3) State renewable energy and alternative use conversions; 

(4) State artificial reefs and rigs-to-reefs development; (5) OCS sand borrowing; (6) offshore LNG 

projects; (7) commercial fishing; and (8) natural processes, including wave action and hurricanes. These 

impact-producing factors all create associated bottom disturbances that may threaten prehistoric 

archaeological resources. An impact could result from contact between prehistoric resources and 

permitted activities such as State oil and gas activities, renewable energy activities, artificial reef creation, 

new channel dredging, and maintenance dredging. With the exception of maintenance dredging, 

preconstruction surveys may be required for these activities. Impacts to prehistoric resources may still 

occur in areas where a remote-sensing survey fails to resolve the location of partially or completely buried 

resources or when no pre-disturbance survey is required. Oil and gas program wells, structures, and 

pipelines existing entirely in State waters are not under the jurisdiction of BOEM with respect to the 

archaeological resource protection requirements of the National Historic Preservation Act and would be 

the responsibility of the State and the permitting Federal agency. Prehistoric sites in shallow waters and 

on coastal beaches are exposed to the destructive effects of wave action and scouring currents. Overall, 

loss of data from prehistoric sites has probably occurred, and will continue to occur, in the northeastern 

Gulf of Mexico from the effects of tropical storms. 

The effects of the various impact-producing factors discussed in this analysis have likely resulted in 

localized losses of significant or unique prehistoric archaeological information. In the case of factors 

related to OCS Program activities in the cumulative activity area, it is reasonable to assume that most 

impacts have occurred in areas where surveys have not been required in the past or have been acquired at 

insufficient transect spacing. The incremental contribution of the CPA proposed action is expected to be 

very small due to the efficacy of the required remote-sensing survey and concomitant archaeological 

report and clearance.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

Various Internet sources were examined to assess recent information regarding impacts to 

archaeological resources or potential new threats to archaeological resources that may be pertinent to the 

CPA. These Internet sources included various online indexes to periodical literature such as JSTOR, the 

National Technical Information Service’s National Technical Reports Library, and ScienceDirect.

This search did not identify any new information that would be pertinent to the analysis of the 

potential impacts of OCS oil- and gas-related activities on prehistoric archaeological resources. 

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the conclusions from the 

prior 2012-2017 Gulf of Mexico EISs are still valid because no new information on prehistoric 

archaeological resources from the CPA proposed action has become available since those documents 

were published; nevertheless, there is still incomplete or unavailable information regarding the long-term 

effects of oil and/or dispersant contamination on, and the location of, prehistoric archaeological resources 

in the CPA.

This incomplete information may be relevant to adverse effects because the locations and integrity of 

prehistoric archaeological resources on the OCS remain unknown. Nevertheless, this incomplete 

information is not likely to be available within the timeline contemplated within the NEPA analysis of 

this Supplemental EIS. It would take many years before data confirming the presence of prehistoric 

archaeological resources in a given location, and the status of each, could be investigated, analyzed, and 

compiled. Most prehistoric sites within the CPA region are likely deeply buried, resulting in the largest 

portion of the aforementioned exorbitant costs and time factors. An extensive study funded by the 

National Park Service in 1977 in the CPA estimated that prehistoric period sites could be buried on the 
4-90 Central Planning Area Lease Sale 247 Supplemental EIS

OCS under as much as 200 m (656 ft) of sediment in western portions of the CPA and 107 m (351 ft) of 

sediment in eastern portions of the CPA (Coastal Environments, Inc., 1977). 

BOEM used reasonably accepted scientific methodologies to extrapolate from existing survey data in 

completing the relevant analysis and formulating the conclusions presented here. In addition, new sitespecific, remote-sensing surveys of the seafloor are required when deemed appropriate to establish the 

presence of potential resources. The results of these surveys are reviewed in tandem with credible 

scientific evidence from previously identified terrestrial sites, regional sedimentology, and physical 

oceanography that is relevant to evaluating the adverse impacts on landforms that may preserve 

prehistoric resources that are a part of the human environment. The required surveys are analyzed by 

archaeologists prior to any new or significant bottom-disturbing impacts being authorized and avoidance 

of potential resources prescribed. Archaeological surveys, where required, are expected to be highly 

effective in identifying resources to allow for the protection of the resource during OCS oil- and gasrelated activities. The CPA proposed action is not expected to have a reasonably foreseeable significant 

impact because BOEM’s evaluation of such impacts is based upon pre-disturbance and site-specific 

survey, the results of which BOEM uses to require substantial avoidance of any potential prehistoric 

resource that could be impacted by the proposed activity. Therefore, BOEM has determined that the 

information is not essential to a reasoned choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for prehistoric archaeological resources presented in the prior 

2012-2017 Gulf of Mexico EISs based on the additional information presented above. No new significant 

information was discovered that would alter the impact conclusion for prehistoric archaeological 

resources presented in those NEPA documents because of the available scientifically credible evidence in 

this analysis and based upon accepted scientific methods and approaches. The analysis and potential 

impacts discussed in those documents still apply for proposed CPA Lease Sale 247.

4.1.1.23. Human Resources and Land Use

4.1.1.23.1. Land Use and Coastal Infrastructure

BOEM has reexamined the analysis for land use and coastal infrastructure presented in the prior 

2012-2017 Gulf of Mexico EISs, based on the additional information presented below. No new 

significant information was discovered that would alter the impact conclusion for land use and coastal 

infrastructure presented in those NEPA documents. The analysis and potential impacts detailed in those 

documents still apply for proposed CPA Lease Sale 247. 

A detailed description of the affect environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.23.1 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.23.1 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.23.1 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

is a summary of the resource description and impact analysis incorporated from those NEPA documents. 

Any new information that has become available since those documents were published is presented 

below. 

Impacts of Routine Activities and Accidental Events

Routine impact-producing factors associated with the CPA proposed action that could affect land use

and coastal infrastructure include the construction of new or expansion of existing gas processing 

facilities, pipeline landfalls, service bases, navigation channels, and waste disposal facilities. The OCS 

oil- and gas-related infrastructure has developed over many decades and is an extensive and mature 

system that provides support for offshore activities. The expansive presence of this coastal infrastructure 

is the result of long-term industry trends, and it is not subject to rapid fluctuations. 

Routine activities relating to the CPA proposed action are expected to minimally affect the current 

land use of the analysis area because most subareas have strong industrial bases and designated industrial 

parks with existing infrastructure and facilities to accommodate future growth in oil and gas businesses. 

BOEM projects up to one new gas processing facility and up to one new pipeline landfall may occur from 
Description of the Environment and Impact Analysis 4-91

activities associated with the CPA proposed action. There may be increased demand for waste disposal

services; however, this would minimally affect land use and infrastructure because waste disposal would 

occur at facilities already designated for such purposes and enough spare capacity exists at these facilities 

in the GOM region (Dismukes, official communication, 2015). BOEM anticipates that there may be 

maintenance dredging of navigation channels in support of routine activity at services bases as a result of 

the CPA proposed action. 

Accidental events associated with the CPA proposed action that could affect land use and coastal 

infrastructure include, but are not limited to, oil spills, vessel collisions, and chemical/drilling-fluid spills. 

Accidental events associated with the CPA proposed action would occur at differing levels of severity, 

based in part on the location, timing/season, and size of event. Depending on where an accidental event 

occurs, it is expected that the oil-spill response equipment needed to respond to an offshore spill as a 

result of the proposed CPA lease sale could be called out from one or more of the following oil-spill 

equipment base locations: New Iberia, Belle Chasse, Baton Rouge, Sulphur, Morgan City, Port 

Fourchon, Harvey, Leeville, Fort Jackson, Venice, Grand Isle, or Lake Charles, Louisiana; La Porte, 

Corpus Christi, Port Arthur, Aransas Pass, Ingleside, Galveston, or Houston, Texas; Kiln or Pascagoula, 

Mississippi; Mobile or Bayou La Batre, Alabama; Panama City, Pensacola, Tampa, or Miami, Florida;

and/or Ponce or San Juan, Puerto Rico (Clean Gulf Associates, 2014; Marine Spill Response Corporation, 

2014; National Response Corporation, 2014). 

Cumulative Impacts 

The cumulative analysis considers both existing land use patterns and the effects of impact-producing 

factors from OCS oil- and gas-related and non-OCS oil- and gas-related activities. Impact-producing 

factors associated with OCS oil- and gas-related activities that could affect land use and coastal

infrastructure include the construction of new or expansion of existing gas processing facilities, pipeline

landfalls, service bases, navigation channels, and waste disposal facilities, plus the occurrence of oil 

spills, vessel collisions, and chemical/drilling-fluid spills. Any service base expansion in the cumulative 

case would be limited, would occur on lands designated for such purposes, and would have minimal 

effects on land use and infrastructure. Impacts resulting from chemical or oil spills and vessel collisions 

can vary in location and severity, but they are not likely to last long enough to adversely affect overall 

land use or coastal infrastructure in the analysis area. A low-probability catastrophic spill, which is not 

part of the CPA proposed action and not likely expected to occur, can result in impacts to land use and 

coastal infrastructure. For more information on a low-probability catastrophic spill event, refer to 

Appendix B. Therefore, the incremental contribution of impact-producing factors from cumulative OCS 

oil- and gas-related activities to the cumulative impacts on land use and coastal infrastructure is also 

expected to be minor. 

The non-OCS oil- and gas-related factors that can contribute substantially to the baseline conditions 

as well as affect coastal infrastructure and land use consist of the following:

• prior, current, and future State oil and gas lease sales;

• other onshore fossil fuel exploration and production activities; 

• petrochemical and manufacturing activities;

• housing and other residential developments; 

• the development of private and publicly owned recreational facilities;

• the construction and maintenance of industrial facilities and transportation systems; 

• urbanization; 

• city planning and zoning; 

• changes to public facilities such as water, sewer, educational, and health facilities;

• changes to military bases and reserves;

• changes in population density; 
4-92 Central Planning Area Lease Sale 247 Supplemental EIS

• changes in State and Federal land use regulations; 

• changes in non-OCS oil- and gas-related demands for water transportation systems 

and ports; 

• macro- and microeconomic trends; 

• coastal landloss and subsidence; and

• natural processes.

The OCS oil and gas program exists within a highly industrialized and economically diverse coastal 

region, which is itself the aggregate of past and present community, government, and business actions. 

How land has been traditionally used or will be used in the future is determined irrespective of the CPA 

proposed action. Coastal infrastructure associated with the OCS oil and gas industry is also utilized by 

State leased and privately owned oil and gas interests, as well as other industries. State oil and gas 

activities and associated impacts will occur based on State leasing programs, geologic plays, economic 

trends, and local regulatory regimes. The OCS oil- and gas-related support activities occur within a 

context of a well-established populated coastal region, which is home to a diverse and robust economy. 

Many local and national industries, such as agricultural and industrial interests, utilize the same 

transportation systems and ports used by the OCS oil and gas industry. The OCS oil- and gas-related 

demands on land use are typically relegated to coastal or inland waterway industrial zones and represent a 

small fraction of how existing residential, recreational, agricultural, military, and industrial uses utilize 

and impact land use and coastal infrastructure. Because the vast majority of coastal infrastructure 

supports OCS and State offshore and land-based oil and gas production, as well as other land-based 

industrial uses, the coastal infrastructure supporting the CPA proposed action represents only a small 

portion of the coastal land use and infrastructure throughout the CPA and Gulf of Mexico. Therefore, the 

incremental contribution of the CPA proposed action is expected to have minimal impact overall. 

Land use categories are tied to existing infrastructure and historic uses, and for the purpose of this 

analysis include the Economic Research Service’s land use inventory categories, which include the 

following: land-based oil and gas activities and those in State waters; agriculture; forest, parks, and 

special use areas; urban areas; miscellaneous areas; and inland navigable waterways and ports. Land use 

patterns vary greatly by region, reflecting differences in soils, climate, topography, and patterns of 

population settlement. Changes in land use will largely depend upon local zoning and economic trends. 

Of the over 400,000 mi

2

 (1,035,995 km2) comprising these coastal states, 18 percent of the total land area 

is covered in cropland. Texas and Mississippi have the highest percentages of cropland, with 20 percent 

and 19 percent of each respective State’s total land being used for cropland. Louisiana’s highway 

network is the 32nd largest in the Nation, with the State highway system the 11th largest. The network is 

comprised of over 60,000 mi (96,561 km) and more than 13,000 bridges under the jurisdiction of Federal, 

State, and local governments and entities. The 27.4 percent of highway network centerline mileage that 

are State-owned places Louisiana 10th nationally, while the 30 percent of total highway network lane 

mileage that are State-owned places Louisiana 11th (State of Louisiana, Dept. of Transportation and 

Development, 2011). Five interstate highways converge in Alabama, allowing goods to be shipped to 

major markets. The I-22 is planned to be completed by 2014, making this the sixth interstate in Alabama 

(Economic Development Partnership of Alabama, 2013). 

The Ports of South Louisiana and Houston rank 13th and 14th, respectively, in total trade for all world 

ports and 1st and 2nd, respectively, for American ports (American Association of Port Authorities, 2012). 

With direct access to the Mississippi River and its system of inland rivers, the Port of South Louisiana 

averages 223 million metric tons per year. In Louisiana, there are 2,823 mi (4,543 km) of inland 

waterways (State of Louisiana, Dept. of Transportation and Development, 2011). Alabama’s water 

corridors connect to over 15,000 mi (24,140 km) of inland waterways in 23 states (Economic 

Development Partnership of Alabama, 2013). Meanwhile, OCS oil- and gas-related coastal infrastructure

and land use represent only an incremental contribution to total land use, and the cumulative impacts as a 

result of the CPA proposed action and the OCS Program as a whole on land use and coastal infrastructure 

are also expected to be minor. This short summary of land uses and land use categories and coastal 

infrastructure is by no means comprehensive, but it should illustrate that OCS oil- and gas-related coastal 
Description of the Environment and Impact Analysis 4-93

land use and infrastructure comprises only a percentage of the total land use and allows us a bird’s eye 

view of the program within the context of other impact-producing factors. 

The proposed CPA lease sale would mostly maintain ongoing activity levels associated with the 

current OCS Program. Industry would essentially maintain its current usage of infrastructure according to 

the proposed lease sale schedule. Macroeconomic shifts, such as a change in commodity prices or an 

economic upturn or downturn, will also determine future utilization of this infrastructure.

The CPA proposed action would minimally affect the current land use within the analysis area 

because most subareas have strong industrial bases and designated industrial parks with enough capacity 

to accommodate the future growth that OCS oil- and gas-related businesses would demand. Coastal land 

use and infrastructure along the Gulf Coast can also be impacted by non-OCS oil- and gas-related 

conflicts, as well as a variety of other factors, such as coastal erosion and economic factors. However, the 

incremental contribution of the CPA proposed action is expected to be minimal in light of all OCS oiland gas-related and non-OCS oil- and gas-related activities.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

Additional research was conducted to investigate the availability of recent information affecting land 

use and coastal infrastructure since publication of the prior 2012-2017 Gulf of Mexico EISs. Various 

Internet sources were examined, including the websites of numerous Federal and State agencies (USDHS, 

Federal Emergency Management Agency; USDOC, Bureau of the Census; USDOC, NOAA; U.S. 

Department of Energy, Energy Information Administration; U.S. Department of Transportation, Maritime 

Administration; USDOI, FWS; RestoreTheGulf.gov website; Deepwater Horizon Oil Spill Portal; 

USEPA; Louisiana Department of Environmental Quality; Louisiana Recovery Authority; Louisiana 

Office of Community Development; Mississippi Department of Environmental Quality; Alabama 

Department of Environmental Management; and the State of Florida Department of Environmental 

Protection). Further information was sought from other organizations, recently published journal articles, 

and trade publications such as The Greater Lafourche Port Commission, LA1 Coalition, The Oil Drum, 

Rigzone, Oil and Gas Journal, Offshore Magazine, Reuters, TOLLROADS News, and The Energy 

Journal. 

The latest projections from the USDOE’s Energy Information Administration (2015h) reflect the 

ongoing trend of decreasing energy imports as domestic production of crude oil and natural gas are 

projected to continue increasing over the next several years. These projections stand in stark contrast to 

the ongoing reduction in new rig orders globally and a declining operating rig count in the GOM (Odell, 

2015; Offshore, 2015). Fluctuations in new and ongoing OCS oil- and gas-related activities can be 

expected and will have a minor effect on coastal infrastructure as oil and gas companies adjust to 

maximize efficiencies and protect profit margins. However, none of this new information would alter the 

impact conclusion for land use and coastal infrastructure presented in the prior 2012-2017 Gulf of Mexico 

EISs because the new information is consistent with longstanding expectations. The analysis and 

potential impacts discussed in those NEPA documents still apply for proposed CPA Lease Sale 247.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplemental EIS and in Chapter 4.2.1.23.1 

of the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS and Chapter 

4.1.1.23.1 of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS, 

BOEM has identified incomplete information regarding the potential impacts of coastal landloss on land 

use and coastal infrastructure. This incomplete information may be relevant to adverse effects because a 

comprehensive understanding of the potential impacts of coastal landloss on coastal infrastructure and 

land use remains unknown. It is not completely known how current subsidence and erosion are affecting 

industry or whether industry is making plans to mitigate current or future impacts. This information 

cannot reasonably be obtained because the overall costs in time and money to collect data on the varying 

impacts of coastal landloss to different firms are exorbitant. BOEM has proposed a study to evaluate 
4-94 Central Planning Area Lease Sale 247 Supplemental EIS

these potential effects by surveying industry on current impacts and potential adaptation strategies, but at 

the time of publication of this Supplemental EIS, it is unfunded, and it would take several years before 

data could be available. Nevertheless, this incomplete information is not likely to be available within the 

timeline contemplated in the NEPA analysis of this Supplemental EIS.

BOEM used reasonably accepted scientific methodologies to extrapolate from existing information in 

completing this analysis and formulating the conclusions presented here. For example, BOEM knows 

that, in the case of coastal ports for instance, dredged material from navigation slips are used to fill in 

property and mitigation habitat areas for wildlife and to act as a barrier to protect ports from storm surges 

(Volz, 2013). While coastal infrastructure is subject to the impacts of coastal landloss and routine tropical 

storm activity, there is still considerable investment to expand, improve, and protect existing 

infrastructure. In June 2013, Louisiana Governor Bobby Jindal signed Senate Bill 122, which modified 

the Investor Tax Credit and the Import-Export Tax Credit. The new credits now include projects like 

warehousing and storage, port operations, marine cargo handling, ship building and repairs, and oil- and 

gas-related activities (State of Louisiana, Office of the Governor, 2013). Additionally, the decision 

criteria for the State of Louisiana’s 5-year coastal restoration planning document places a higher value on 

collections of risk reduction and restoration projects that improve coastal conditions for oil- and gasrelated infrastructure and increase the resilience of coastal communities that support the industry. The 

criterion also puts a higher value on projects that benefit the navigation industry and places a lower value 

on projects that impede navigation (State of Louisiana, Coastal Protection and Restoration Authority, 

2012a). Therefore, coastal restoration efforts will be focused on those land use areas with a higher 

concentration of OCS coastal infrastructure. While not completely known, current and future industry 

adaptation plans for coastal landloss are not essential to a reasoned choice among alternatives for this 

Supplemental EIS (including the No Action and an Action alternative). 

Like any industrial infrastructure improvements, future adaptations will likely occur on an as-needed 

basis or as new technologies become available. Therefore, BOEM has determined that the information is 

not essential to a reasoned choice among alternatives. BOEM will continue to monitor industry and its 

infrastructure footprint over time to document short- and long-term impacts of continued landloss. For a 

more detailed discussion on deltaic landloss, refer to Chapter 4.1.1.4. 

Summary and Conclusion

BOEM has reexamined the analysis for land use and coastal infrastructure presented in the prior 

2012-2017 Gulf of Mexico EISs based on the additional information presented above. No new significant 

information was discovered that would alter the impact conclusion for land use and coastal infrastructure 

presented in those NEPA documents because the new information was roughly consistent with prior 

expectations. The analysis and potential impacts discussed in those documents still apply for proposed 

CPA Lease Sale 247.

4.1.1.23.2. Demographics

BOEM has reexamined the analysis for demographics presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for demographics presented in those NEPA documents. 

The analysis and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 

247. 

A detailed description of the affected and the full analyses of the potential impacts of routine 

activities, accidental events, and cumulative events associated with the CPA proposed action are 

presented in Chapter 4.2.1.23.2 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.23.2 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.23.2 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis presented in those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 
Description of the Environment and Impact Analysis 4-95

Impacts of Routine Activities and Accidental Events

In general, impact-producing factors that cause employment impacts, such as exploration and 

delineation activities, development and production activities, and coastal infrastructure development, can 

have some impacts on the demographic characteristics of a particular area. However, routine activities 

associated with the CPA proposed action are projected to minimally affect the demography of the analysis 

area. The projected impacts to population arising from the proposed CPA lease sale are calculated by 

multiplying the employment estimates from the mathematical model MAG-PLAN by an estimate of the 

number of members in a typical family. The projected population increases arising from the proposed 

CPA lease sale are then divided by the population forecasts in Woods and Poole, Inc. (2015), which 

yields the percentage impacts to population of the proposed CPA lease sale. Population impacts from the 

CPA proposed action are projected to be minimal (<1% of the total population) for all Economic Impact 

Areas (EIAs) in the Gulf of Mexico region.

Accidental events associated with the CPA proposed action, such as low- to moderate-scale oil or 

chemical spills and vessel collisions, would likely have no effects on the long-term demographic 

characteristics of the Gulf coastal communities. This is because accidental events typically cause only 

short-term population movements as individuals seek employment related to the event or have their 

existing employment displaced during the event. 

Cumulative Impacts 

The cumulative analysis considers the effects of impact-producing factors related to OCS oil- and 

gas-related activities along with non-OCS oil- and gas-related impact-producing factors. The OCS oiland gas-related factors that could impact the demographics of any area consist of routine activities and 

accidental events arising from prior, current, and future OCS lease sales, including impact-producing 

factors that cause employment impacts (i.e., exploration and delineation activities, development and 

production activities, and coastal infrastructure development) as well as oil spills and vessel collisions. 

The impacts to population arising from the CPA proposed action are projected to be minimal (<1% of the 

total population) for any EIA in the Gulf of Mexico region based on the employment estimates from the 

mathematical model MAG-PLAN for low-case and high-case scenarios for OCS oil- and gas-related 

activities. Accidental events should not have long-term effects on the demographic characteristics of the 

Gulf coastal communities because population movements from such events are typically short-term. For 

a detailed discussion of the employment and demographic impacts of a low-probability catastrophic spill, 

which is not part of the CPA proposed action and not likely expected to occur, refer to Appendix B. 

There are numerous non-OCS oil- and gas-related factors that could impact demographics, including 

fluctuations in workforce, net migration, relative income, oil and gas activity in State waters, offshore 

LNG activity, trends in tourism activities (refer to Chapter 4.1.1.21), and other economic factors (refer to 

Chapter 4.1.1.23.3). Common approaches in analyzing cumulative effects begin by assembling a list of 

other projects and actions that will likely be associated with the CPA proposed action. However, no such 

list of future projects and actions could be assembled that would be sufficiently current and 

comprehensive to support a cumulative analysis for all 133 of the coastal counties and parishes in the 

analysis area over a 40-year period. Instead, this analysis uses the economic and demographic projections 

from Woods & Poole Economics, Inc. (2015) as a reasonable approximation to define the contributions of 

other likely projects, actions, and trends to the cumulative case.

The CPA proposed action would contribute to the population impacts arising from the overall OCS 

Program. The CPA proposed action is projected to have an incremental contribution of less than 1 

percent to the population level in any of the EIAs, in comparison with other factors influencing 

population growth, such as the status of the overall economy, fluctuations in workforce, net migration, 

health trends, and changes in income. Given both the low levels of population growth and industrial 

expansion associated with the CPA proposed action, it is expected that the baseline age and racial 

distribution patterns will continue through the analysis period. 
4-96 Central Planning Area Lease Sale 247 Supplemental EIS

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

BOEM conducted a search of Internet resources and known data sources related to demographics. 

The primary source of new information is Woods & Poole Economics, Inc. (2015), which is an annual 

update of the data that were used in the CPA 241/247 Supplemental EIS. Woods & Poole Economics, 

Inc. (2015) provides projections of economic and demographic variables at the county/parish level. In 

Chapter 4.1.1.23.3, BOEM introduced new EIAs that aggregate counties based on trade, commuting, and 

demographic data. Table 4-3 aggregates Woods and Poole data by EIA and presents each EIA’s 

population, employment, gross regional product, income per capita, median age, male percentage, and 

race composition. The largest EIAs (in terms of population and employment) are TX-3 (which includes 

Houston and Galveston), FL-5 (which includes Tampa), and TX-1 (which includes Cameron and Hidalgo 

Counties). The smallest EIAs are TX-6, MS-2, and LA-2. Table 4-4 presents Woods and Poole’s 

forecasted levels of economic and demographic variables in 2050. From 2015 through 2050, the fastest 

population and employment growth is forecast in TX-1, TX-3, FL-6, and FL-4; the slowest growth is 

forecast in LA-6, TX-5, AL-2, and MS-1. 

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change impact conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. This incomplete or unavailable information relates to translating 

employment impacts of OCS oil- and gas-related activities into estimated population impacts. This 

information cannot be obtained at this time due to data limitations and the complexity of methodologies 

needed to accurately estimate population impacts arising from OCS oil- and gas-related activities. BOEM 

plans to initiate a study project to analyze population impacts more fully, although this potential study 

project will not be completed within the timeline contemplated in the NEPA analysis of this Supplemental 

EIS. BOEM used reasonably accepted scientific methodologies to extrapolate from existing information 

in completing this analysis and formulating the conclusions here. For example, BOEM used data from 

Woods & Poole Economics, Inc. (2015), which provides projections of the evolution of the total 

population in all EIAs in future years. These projections assume the continuation of existing social, 

economic, and technological trends at the time of the forecast. This incomplete or unavailable 

information is unlikely to significantly impact BOEM’s estimates of the impacts of OCS lease sales on 

demographics, in part because these impacts are fairly limited. In addition, increases in population arising 

from lease sales are generally positive, not adverse, impacts. Therefore, BOEM has determined that the 

incomplete or unavailable information is not essential to a reasoned choice among alternatives.

Summary and Conclusion

BOEM has reexamined the analysis for demographics presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented above. No new significant information was 

discovered that would alter the impact conclusion for demographics presented in those NEPA documents 

because the new Woods and Poole Economics, Inc. data did not change much from what was presented in 

those documents. The analysis and potential impacts in those documents still apply for proposed CPA 

Lease Sale 247.

4.1.1.23.3. Economic Factors

BOEM has reexamined the analysis for economic factors presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented below. No new significant information was 

discovered that would alter the impact conclusion for economic factors presented in those NEPA

documents. The analysis and potential impacts discussed in those documents still apply for proposed 

CPA Lease Sale 247.

A detailed description of the affected environment and the full analyses of the potential impacts on 

economic factors from routine activities, accidental events, and cumulative events associated with the 
Description of the Environment and Impact Analysis 4-97

CPA proposed action are presented in Chapter 4.2.1.23.3 of the 2012-2017 WPA/CPA Multisale EIS. 

Updated information is provided in Chapter 4.2.1.23.3 of the WPA 233/CPA 231 Supplemental EIS and 

Chapter 4.1.1.23.3 of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 

Supplemental EISs. The following is a summary of the resource description and impact analysis 

incorporated from those NEPA documents. Any new information that has become available since those 

documents were published is presented below. 

Impacts of Routine Activities and Accidental Events

Impact-producing factors such as exploration and delineation activities, development and production 

activities, and coastal infrastructure development can have some impacts on the economic characteristics, 

such as employment, of a particular area. The expected economic impacts of the OCS oil and gas 

industry are estimated using the mathematical model MAG-PLAN. The MAG-PLAN estimates the 

direct, indirect, and induced employment arising from a particular scenario for oil and gas exploration and 

development activities; these scenarios include estimates of activities such as drilling, platform 

installations, and structure removals. As a result of proposed CPA Lease Sale 247, there would be only 

minor economic changes in the Texas, Louisiana, Mississippi, Alabama, and Florida EIAs. This is 

because the demand would be met primarily with the existing population and labor force. Most of the 

employment related to proposed CPA Lease Sale 247 is expected to occur in the coastal areas of Texas 

and Louisiana. The CPA proposed action, irrespective of whether one analyzes the high-case or low-case 

production scenario, would not cause employment effects >1 percent in any EIA along the Gulf Coast. 

Accidental events associated with the CPA proposed action, such as oil spills, can cause a number of 

disruptions to local economies. Many of these effects are due to industries that depend on damaged 

resources. However, the impacts of an oil spill can be somewhat broader if companies further along 

industry supply chains are affected. These effects depend on issues such as the duration, methods, and 

logistics of the cleanup operations and the responses of policymakers to a spill. However, the impacts of 

small- to medium-sized spills should be localized and temporary.

Cumulative Impacts 

The cumulative analysis considers the effects of OCS oil- and gas-related impact-producing factors 

along with non-OCS oil- and gas-related impact-producing factors that may occur and adversely affect 

economic factors in the same general area of the CPA proposed action. BOEM uses the model 

MAG-PLAN to determine the direct, indirect, and induced employment arising from a particular scenario 

for oil and gas exploration and development activities (i.e., drilling, platform installations, and structure 

removals). The CPA proposed action would not cause employment effects >1 percent in any EIA along 

the Gulf Coast. Oil spills can cause a number of disruptions to local economies; however, small- to 

medium-sized spills should have localized, temporary impacts. A low-probability catastrophic spill, 

which is not part of the CPA proposed action and not likely expected to occur, would have more 

noticeable impacts to the economy. However, the likelihood of another spill of this scale is quite low. A 

detailed analysis of a low-probability catastrophic spill can be found in Appendix B. 

Non-OCS oil- and gas-related impact-producing factors that can affect economic trends in economic 

areas in the Gulf of Mexico region include commercial, military, recreation/tourism (refer to Chapter 

4.1.1.21), and numerous other offshore and coastal activities. To estimate the cumulative impacts to 

economic factors from non-OCS oil- and gas-related impact-producing factors, BOEM employs the 

economic and demographic projections from Woods & Poole Economics, Inc. These projections are 

based on local, regional, and national trend data, as well as likely changes to local, regional, and national 

economic and demographic conditions. Therefore, the projections include employment associated with 

the continuation of current patterns in OCS oil- and gas-related leasing activity, as well as the 

continuation of trends in other industries important to the region. For example, these forecasts include the 

contributions of State oil and gas activities, renewable energy activities, coastal land use, and tourismrelated activities. The cumulative impacts of the CPA proposed action would be determined by the 

expected path of the economy and by the expected progression of the OCS oil and gas industry in 

upcoming years. The expected path of the overall economy is projected using the data provided by 

Woods and Poole Economics, Inc. The expected economic impacts of the OCS oil and gas industry in 
4-98 Central Planning Area Lease Sale 247 Supplemental EIS

upcoming years are estimated using the mathematical model MAG-PLAN. The cumulative impacts of 

the CPA proposed action to the economies along the Gulf Coast are expected to be relatively small.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/ 241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

BOEM examined a variety of Internet sources, as well as known data providers, for new information 

regarding the impacts of the CPA proposed action on economic factors. Beginning with this 

Supplemental EIS, BOEM will use new definitions of EIAs along the Gulf Coast. These EIAs were 

developed through a cooperative agreement with Louisiana State University (Fannin and Varnado, 

official communication, 2015). These EIAs aggregate counties based on analysis of trade, commuting, 

and demographic data; Figure 4-5 presents these 23 EIAs. These EIAs will be used to present various 

data, including demographic data (refer to Chapter 4.1.1.23.2) and data on the scales of recreation and 

tourism along the Gulf Coast (refer to Chapter 4.1.1.21).

The DOE’s Energy Information Administration (201(5i) presents forecasts of energy markets in 2015 

and 2016, which improves BOEM’s estimates of the cumulative impacts to economic factors. For 

example, this report forecasts that oil prices will remain low in the near-term, averaging $49.62/bbl in 

2015 and $54.42/bbl in 2016. Lower energy prices have caused slowdowns in offshore drilling activities 

(Beaubouef, 2015) and rig construction (Odell, 2015). However, GOM offshore oil production is forecast 

to increase from an average of 1.4 MMbbl per day in the fourth quarter of 2014 to more than 1.6 MMbbl 

per day in the fourth quarter of 2016 (USDOE, Energy Information Administration, 2015i). This 

production increase reflects the contributions of 13 Gulf of Mexico projects that are expected to come 

online in 2015 and 2016. 

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the impact conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. This information primarily relates to the onshore geographic 

distributions of economic impacts arising from the OCS Program, which would allow BOEM to better 

estimate routine and cumulative impacts. This information is difficult to obtain since most data sources 

do not adequately differentiate between onshore and offshore oil and gas activities. BOEM used 

reasonably accepted scientific methodologies to extrapolate from existing information in completing the 

relevant analysis and formulating the conclusions presented here. In particular, BOEM used the model 

MAG-PLAN to estimate the impacts of the CPA proposed action and the OCS Program. In addition, the 

economic impacts arising from the OCS Program are generally positive, not adverse. Therefore, BOEM 

has determined that the incomplete or unavailable information is not essential to a reasoned choice among 

alternatives.

Summary and Conclusion 

BOEM has reexamined the analysis for economic factors presented in the prior 2012-2017 Gulf of 

Mexico EISs based on the additional information presented above. No new significant information was 

discovered that would alter the impact conclusion for economic factors presented those NEPA documents. 

The analysis and potential impacts discussed in those documents still apply for proposed CPA Lease Sale 

247. 

4.1.1.23.4. Environmental Justice

BOEM has reexamined the analysis for environmental justice presented in the prior 2012-2017 Gulf 

of Mexico EISs based on the additional information presented below. No new significant information 

was discovered that would alter the impact conclusion for environmental justice presented in those NEPA

documents. The analyses and potential impacts discussed in those documents still apply for proposed 

CPA Lease Sale 247.
Description of the Environment and Impact Analysis 4-99

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.23.4 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.23.4 of the WPA 233/CPA 231 Supplemental EIS, and Chapter 4.1.1.23.4 of 

the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The 

following information is a summary of the resource description and impact analysis incorporated from 

those NEPA documents. Any new significant information that has become available since those 

documents were published is presented below. 

The oil and gas industry and its associated support sectors are interlinked and widely distributed along 

the Gulf Coast. Offshore OCS oil- and gas-related industry operations within the CPA may utilize 

onshore facilities located within the WPA, CPA, or both planning areas. This analysis focuses on 

potential disproportionate impacts to minority and low-income populations living onshore. BOEM 

conducts a county-level analysis to determine the concentration of minority and low-income populations 

located in the same counties/parishes as oil- and gas-related onshore coastal infrastructure (refer to 

Chapter 4.2.1.23.4.1 and Figures 4-26 through 4-35 of the 2012-2017 WPA/CPA Multisale EIS). 

In seeking public input under NEPA, the Bureau of Ocean Energy Management strives to include all 

perspectives and to make the process accessible to anyone who wishes to comment. Therefore, BOEM 

provides opportunities for public input, which includes minority and low-income populations. Some of 

the numerous avenues for public outreach employed by BOEM include the following: specific types of 

notices that are (1) mailed to public libraries, interest groups, industry, the general public, local, State, and 

Federal agencies, and federally recognized Indian Tribes; (2) published in local newspapers; (3) posted on 

the Internet; and (4) published in the Federal Register. These notices reflect the stages of the NEPA 

process and include the Notice of Intent to Prepare an EIS (NOI), the Call for Information (Call), and 

Notice of Availability (NOA) for the Draft Supplemental EIS. A series of specified time periods after the 

NOI, Call, and NOA allow for public comments. All public comments are considered and addressed. 

The formal scoping process is initiated by the NOI and Call, and public scoping meetings are held in 

several geographically separate cities to allow for public discussion and questions, and to identify 

concerns of all interested parties. All public comments and responses to comments are published in the 

Draft and Final Supplemental EISs. A detailed discussion of the complete scoping process can be found 

in Chapter 1.4. A summary of the scoping comments for this Supplemental EIS can be found in 

Chapter 5.3.2. 

Impacts of Routine Activities and Accidental Events

The potential routine impact-producing factors associated with the proposed CPA action that could 

affect environmental justice include the following: possible infrastructure changes or expansions 

including fabrication yards, support bases, and onshore disposal sites for offshore waste; increased 

commuter and truck traffic; and employment changes and immigration. Given the existing extensive and 

widespread support system for the OCS oil- and gas-related industry and its associated labor force, the 

effects of routine operations related to the CPA proposed action are expected to be widely distributed and 

to have little impact because the CPA proposed action would not significantly change the already existing 

conditions, such as traffic or the amount of infrastructure. Impacts related to routine operations are 

expected to be primarily economic in nature and to have a limited but positive effect because the CPA 

proposed action would contribute to the sustainability of the current industry, related support services, and 

associated employment, especially in Louisiana where an extensive concentration of OCS oil- and gasrelated infrastructure is located, e.g., Port Fourchon in Lafourche Parish. BOEM’s county-level analysis 

determined that there are limited concentrations of minority and low-income population adjacent to OCS 

oil- and gas-related coastal infrastructure. The routine operations associated with the CPA proposed 

action are not expected to have a disproportionate negative effect on these populations. Rather, the CPA 

proposed action would contribute to the maintenance of current OCS oil- and gas-related activity and 

employment levels, resulting in some beneficial direct and indirect effects to low-income and minority 

populations. 

Accidental disturbances resulting from the CPA proposed action, including oil spills, vessel collision, 

and chemical/ drilling fluids spills, have the potential to negatively affect minority and low-income 

populations through direct exposure to oil, dispersants, degreasers, and other chemicals that can affect 

human health; decreased access to natural resources due to environmental damages, fisheries closures, or 
4-100 Central Planning Area Lease Sale 247 Supplemental EIS

wildlife contamination; and proximity to onshore disposal sites used in support of oil and chemical spill 

cleanup efforts. Oil, chemical, and drilling fluid spills may be associated with exploration, production, or 

transportation activities that result from the CPA proposed action. Low-income and minority populations 

might be more sensitive to spills in coastal waters than are the general population because of their 

potentially higher dietary reliance on wild coastal resources, reliance on these resources for other 

subsistence purposes such as sharing and bartering, limited flexibility in substituting wild resources with 

purchased ones, and likelihood of participating in cleanup efforts and other mitigating activities.

Little is known about subsistence along the Gulf Coast, and BOEM is currently funding a study to 

better document subsistence in the region.

As studies of past oil spills have highlighted, different cultural groups can possess varying capacities 

to cope with these types of events (Palinkas et al., 1992). Some minority and/or low-income groups may 

be more reliant on natural resources and/or less equipped to substitute contaminated or inaccessible 

natural resources with private market offerings than higher income level and/or nonminority groups. 

Because lower-income and/or minority populations may live near and may be directly involved with spill 

cleanup efforts, the vectors of exposure can be higher for them than for the general population, increasing 

the potential risks of long-term health effects. However, small-scale accidental oil spills, vessel collision, 

and chemical/drilling fluids spills are not likely to be of sufficient size or duration to have adverse and 

disproportionate long-term effects for minority and low-income populations in the analysis area. 

Cumulative Impacts 

The cumulative analysis considers impacts that may result from the CPA proposed action within the 

context of OCS oil- and gas-related and non-OCS oil- and gas-related impact-producing factors for 

environmental justice. The OCS oil- and gas-related impact-producing factors include OCS leasing, 

exploration, development, and production activities and the accidental events arising from these OCS oiland gas-related activities. Non-OCS oil- and gas-related impact-producing factors include all human 

activities and natural events and processes. The context in which people may find themselves and how 

that context affects their ability to respond to an additional change in the socioeconomic or physical 

environment is the heart of an environmental justice analysis.

The OCS oil- and gas-related impact-producing factors include the OCS Program, which includes 

OCS oil and gas leasing, exploration, development, and production activities that could result in potential 

infrastructure changes/expansions, including fabrication yards, support bases, and onshore disposal sites 

for offshore waste; increased commuter and truck traffic; and employment changes and immigration, as 

well as accidental events arising from these OCS oil- and gas-related activities, such as oil spills, vessel 

collisions, chemical/drilling-fluid spills, and the resultant cleanup that may temporarily affect low-income 

populations who may experience direct exposure to contaminants through subsistence and cleanup 

operations. However, this exposure is expected to be small scale and short term and not result in 

disproportionate long-term effects because of the small scale and size of these events. A detailed analysis 

of a low-probability catastrophic event, such as the Deepwater Horizon explosion, oil spill, and response, 

can be found in Appendix B. In general, the cumulative OCS oil- and gas-related effects are expected to 

be economic, widely distributed, and to have a limited but positive effect on low-income and minority 

populations. In Louisiana, these positive economic effects are expected to be greater because of the 

existence of an extensive and widespread support system for OCS oil- and gas-related activities and 

associated labor force, especially in Lafourche Parish, Louisiana, where Port Fourchon is located. Given 

the existing distribution of the OCS oil and gas industry and the limited concentrations of minority and 

low-income populations near oil and gas infrastructure, based on county-level analysis, the CPA proposed 

action and the cumulative OCS Program are not expected to have disproportionate high/adverse 

environmental or health effects on minority or low-income populations. 

Non-OCS oil- and gas-related cumulative effects cover a wide range of potential impact-producing 

factors, including all human activities and natural events and processes that are not related to OCS oiland gas-related activities in Federal waters. Some of the human activities that may disproportionately 

affect low-income and minority populations include, but are not limited to, the following: urbanization; 

pollution (air, light, noise, garbage dumping, and contaminated runoff); commercial/residential/

agricultural development; zoning ordinances; community development strategies (multi-purpose and 

single-use); expansions to the Federal, State and local highway systems; expansions to regional port 

facilities; military activities; demographic shifts (in-migration and out-migration); economic shifts on the 
Description of the Environment and Impact Analysis 4-101

national, State and local levels (job creation and job losses); educational systems (quality, availability, 

expansions or contractions); family support systems (availability, proximity and quality of mental health 

services, foster care, charity hospital systems, addictive disorders rehabilitation centers, family planning 

services, early learning programs, etc.); governmental functions (municipal waterworks systems, sewage 

systems, tax structures, revenue collection, law enforcement, fire protection, traffic control, voting 

processes, legislative processes, court procedures and processes, real estate property assessments, 

construction permits, environmental protection services, land-use permits, etc.); contraction or expansion 

of the tourism industry; financial system (banking and investment services); State renewable energy

activities; river channelization; dredging of waterways; State oil and gas activity; existing infrastructure

associated with downstream activities such as petrochemical processing; and public health issues.

While human activities are extensive and nearly all-encompassing, there are a substantial number of 

natural events and processes that may be classified as non-OCS oil- and gas-related cumulative effects 

that may disproportionally affect low-income and minority populations including: oyster reef 

degradation; saltwater intrusion; sedimentation of rivers; sediment deprivation; barrier island migration 

and erosion; fish kills; red tide; beach strandings; coastal erosion/subsidence; sea-level rise; and coastal 

storms. Both human-induced and natural factors, unrelated to OCS oil- and gas-related activities, could 

affect minority and low-income populations through exposure to high levels of pollution, job loss, 

reduced social services, adverse infrastructure siting, decreased tourism, public health issues, 

displacement, and increased risk of adverse impacts from storm surge, reduced opportunities for 

subsistence activities, and vulnerability of coastal communities to name a few. For a detailed discussion 

of these non-OCS oil- and gas-related cumulative effects on low income and minority populations, refer 

to Chapter 4.1.1.23.4 of the CPA 235/241/247 Supplemental EIS.

To summarize, the cumulative effects of the CPA proposed action on minority and low-income 

populations would be concentrated in coastal areas, and particularly in Louisiana. Most OCS Program 

effects are expected to make a positive contribution to minority and low-income populations by helping to 

maintain current employment levels and contributing to economic stimulation. The contribution of the 

cumulative OCS Program to the cumulative impacts of all factors affecting environmental justice is 

expected to be minor; therefore, the incremental contribution of the CPA proposed action to the 

cumulative impacts would also be minor. State offshore leasing programs have similar, although more 

limited, effects due to their smaller scale. Cumulative effects from onshore infrastructure, including 

waste facilities, are also expected to be minor because existing infrastructure is regulated, because little 

new infrastructure is expected to result in the cumulative case, and because any new infrastructure will be 

subject to relevant permitting requirements. While all human activities and natural events and processes 

also may raise environmental justice issues, the cumulative consequences to environmental justice cannot 

be determined. The enormity of such a task i.e., the time, labor, and funds that would be necessary to 

assess and analyze the entirety of non-OCS oil- and gas-related factors’ impacts, would not be cost 

effective or even possible to accomplish. When added to existing State and Federal leasing programs, the 

associated onshore infrastructure, onshore and offshore OCS oil- and gas-related activities and all of the 

non-OCS oil- and gas-related impacting factors, a single proposed CPA lease sale would make miniscule 

contributions to the cumulative effects on minority and low-income populations. 

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS

A search of various information sources and trade publications (U.S. Department of Health and 

Human Services, National Institutes of Health; USEPA; USDOC, Bureau of the Census and Bureau of 

Labor Statistics; U.S. Department of Homeland Security, Federal Emergency Management Agency; 

RestoreTheGulf.gov website; Deepwater Horizon Claims Center; Deepwater Horizon Oil Spill Portal; 

Louisiana Department of Environmental Quality; Mississippi Department of Environmental Quality; 

Alabama Department of Environmental Management; State of Florida Department of Environmental 

Protection; Louisiana Recovery Authority; Louisiana Office of Community Development; The Greater 

Lafourche Port Commission; LA1 Coalition; Reuters; Rigzone; Oil and Gas Journal; and The Oil Drum), 

as well as recently published journal articles, was conducted to determine the availability of recent 

information on environmental justice. The search revealed the following new information on claims and 

human health impacts from the Deepwater Horizon explosion, oil spill, and response. This information is 
4-102 Central Planning Area Lease Sale 247 Supplemental EIS

important because it expands our knowledge of the baseline environment following the Deepwater 

Horizon explosion, oil spill, and response. 

Legal proceedings that could benefit some members of minority and low-come populations have 

come to a close. The Deepwater Horizon Economic and Property Damages Settlement was finalized on 

June 8, 2015, 1 year and 4 months after the effective date of the Medical Benefits Settlement on 

February 12, 2014 (Deepwater Horizon Claims Center, 2015). The Federal Government and five Gulf 

Coast States settled a law suit with BP and other parties in the summer of 2015; this settlement paves the 

way for billions of dollars in money to be channeled to coastal restoration and other projects (Schleifstein, 

2015). While these monies may eventually benefit minority and low-income populations indirectly, none 

of this new information would alter the impact conclusion for environmental justice presented in the prior 

2012-2017 Gulf of Mexico EISs. The analysis and potential impacts discussed in those NEPA documents 

still apply for proposed CPA Lease Sale 247.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions from the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in this Supplemental EIS, as well as in the 

previously mentioned NEPA documents, BOEM has identified unavailable information regarding the 

impacts of the Deepwater Horizon explosion, oil spill, and response related to environmental justice. 

This information cannot be obtained because long-term health impact studies, subsistence studies, and the 

NRDA process are ongoing, and data from these efforts will be unavailable and unobtainable until the 

studies and NRDA process are complete. In order to fill this data gap, BOEM used existing information 

and reasonably accepted scientific methodologies to extrapolate from available information in completing 

the relevant analysis including limited information that has been released after the Deepwater Horizon

explosion, oil spill, and response and studies of past oil spills, which indicate that a low-probability, 

catastrophic oil spill, which is not part of the CPA proposed action and not likely expected to occur, may 

have significant adverse impacts on lower-income and minority communities. Long-term effects are 

unknown at this time, but so far there has been little concrete evidence that health or subsistence effects 

have occurred (Brown et al., 2011; Dickey, 2012; King and Gibbons, 2011; Middlebrook et al., 2012; 

U.S. Dept. of Labor, Occupational Safety and Health Administration, 2010a and 2010b), although there is 

some dispute in the scientific community about proper risk assessment standards in seafood 

contamination research (Rotkin-Ellman et al., 2012; Rotkin-Ellman and Soloman, 2012). In addition, 

some studies have shown that different cultural groups can possess varying levels of coping capacities 

(Palinkas, 1992), and impacts to social cohesion, including increased distrust in government and other 

institutions, contributed to community anxiety (Tuler et al., 2009). Also, because lower-income and/or 

minority populations may live near and be involved directly with spill cleanup efforts, the vectors of 

exposure can be higher for them than for the general population, increasing the potential risks of longterm health effects. Therefore, because long-term health and subsistence impacts and to low-income and 

minority populations are unknown, this information may be relevant to the evaluation of impacts from the 

Deepwater Horizon explosion, oil spill, and response to environmental justice. However, a subsistence 

study and long-term health studies are pending and will not be available within the timeline contemplated 

in the NEPA analysis of this Supplemental EIS. BOEM will continue to seek additional information as it 

becomes available and bases the previous analysis on the best information currently available. Although 

long-term health or subsistence impacts to minority and low-income populations may be relevant to this 

analysis, BOEM has determined that the incomplete information is not essential to a reasoned choice 

among alternatives based on the information discussed above.

Summary and Conclusion

BOEM has reexamined the analysis for environmental justice presented in the prior 2012-2017 Gulf 

of Mexico EISs based on the additional information presented above. No new significant information 

was discovered that would alter the impact conclusion for environmental justice presented in those NEPA

documents because of the available scientifically credible evidence in this analysis and based upon 

accepted scientific methods and approaches. The analysis and potential impacts in those documents still 

apply for proposed CPA Lease Sale 247. 
Description of the Environment and Impact Analysis 4-103

4.1.1.24. Species Considered due to U.S. Fish and Wildlife Service Concerns

BOEM has reexamined the analysis for species considered due to FWS concerns presented in the 

prior 2012-2017 Gulf of Mexico EISs based on the additional information presented below. No new 

significant information was discovered that would alter the impact conclusion for species considered due 

to FWS concerns presented in those NEPA documents. The analysis and potential impacts discussed in 

those documents still apply for proposed CPA Lease Sale 247. 

A detailed description of the affected environment and the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with the CPA proposed action are 

presented in Chapter 4.2.1.24 of the 2012-2017 WPA/CPA Multisale EIS. Updated information is 

provided in Chapter 4.2.1.24 of the WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.24 of the 

CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS. The following 

information is a summary of the resource description and impact analysis incorporated from those NEPA

documents. Any new information that has become available since those documents were published is 

presented below. 

The species considered are the Louisiana black bear (Ursus americanus luteolus), gopher tortoise 

(Gopherus polyphemus), Alabama red-belly turtle (Pseudemys alabamensis), ringed map turtle 

(Graptemys oculifera), black pine snake (Pituophis melanoleucus lodingi), yellow-blotched map turtle 

(Graptemys flavimaculata), eastern indigo snake (Drymarchon corais couperi), Mississippi gopher frog 

(Rana capito sevosa), frosted flatwoods salamander (Ambystoma cingulatum), reticulated flatwoods 

salamander (Ambystoma bishopi), pallid sturgeon (Scaphirhynchus albus), pearl darter (Percina aurora), 

inflated heelsplitter (Potamilus inflatus), Louisiana quillwort (Isoetes louisianensis), and telephus spurge 

(Euphorbia telephioides). Some species considered due to FWS concerns are discussed in other chapters 

of this Supplemental EIS. The conclusions for the following species can be found in their respective 

chapters: West Indian manatee (Trichechus manatus) (Chapter 4.1.1.12); Gulf sturgeon (Acipenser 

oxyrinchus desotoi) (Chapter 4.1.1.17); green (Chelonia mydas), hawksbill (Eretmochelys imbricata), 

Kemp’s ridley (Lepidochelys kempii), leatherback (Dermochelys coriacea), and loggerhead (Caretta 

caretta) sea turtles (Chapter 4.1.1.13); Alabama beach mouse (Peromyscus polionotus ammobates) and 

Perdido Key beach mouse (Peromyscus polionotus trissyllepsis) (Chapter 4.1.1.15); and red knot 

(Calidris canutus rufa), piping plover (Charadrius melodus), whooping crane (Grus americana), redcockaded woodpecker (Picoides borealis), least tern (Sterna antillarum), Mississippi sandhill crane (Grus 

canadensis pulla), wood stork (Mycteria americana), and mountain plover (Charadrius montanus) 

(Chapter 4.1.1.16).

Impacts of Routine Activities and Accidental Events

Adverse impacts due to routine activities resulting from the CPA proposed action, such as operational 

discharges, noise, and marine debris, are possible but unlikely. Lethal effects could occur from ingestion 

of released plastic materials from OCS oil- and gas-related vessels and facilities. However, there have 

been no reports to date on such incidences. Because of the mitigations that may be implemented 

(Chapter 2.3.1.3), routine activities (e.g., operational discharges, noise, and marine debris) related to the

CPA proposed action are not expected to have long-term adverse effects on the size and productivity of 

any of these species or populations in the Gulf of Mexico. Greatly improved handling of waste and trash

by industry and annual awareness training required by the marine debris mitigations are reducing the 

amount of plastics in the ocean, and therefore minimizing the devastating effects on offshore and coastal 

marine life. The routine activities of the CPA proposed action are unlikely to have significant adverse 

effects on the size and recovery of any of the above-mentioned species or populations in the GOM due to 

the distance of most activities, the heavy regulation of infrastructure and pipelines, and permitting and 

siting requirements.

Accidental oil spills and spill-response activities resulting from the CPA proposed action have the 

potential to impact small to large areas in the Gulf of Mexico with physical oiling and habitat destruction. 

The severity of impacts depends on the magnitude and frequency of accidents, the ability to respond to 

accidents, the location and date of accidents, and various meteorological and hydrological factors 

(including tropical storms). Adverse impacts due to accidental events are also likely to be minimal 

because the habitats used by the species considered are far from OCS oil- and gas-related activities and 
4-104 Central Planning Area Lease Sale 247 Supplemental EIS

are inland. Therefore, the CPA proposed action would be expected to have little or no effect on these 

species of concern.

Cumulative Impacts 

The cumulative analysis considers activities that have occurred, are currently occurring, and could 

occur and adversely affect species considered due to FWS concerns. The OCS oil- and gas-related 

activities that could impact species considered due to FWS concerns include operational discharges, 

noise, marine debris, oil spills, and spill-response activities. Routine activities are not anticipated to 

impact these species because of the mitigations and regulations implemented by BOEM, and accidental 

events are expected to be minimal to these species because the habitats used by the species considered are 

far from OCS oil- and gas-related activities and are inland. A low-probability catastrophic spill, which is 

not part of the CPA proposed action and not likely expected to occur, could impact species considered 

due to FWS concerns and is discussed in Appendix B. 

Non-OCS oil- and gas-related activities that could impact species considered due to FWS concerns

include State oil and gas activities, other governmental and private projects and activities, hurricanes, and 

natural processes and events that may occur and that adversely affect wetland habitat. Non-OCS oil- and 

gas-related activities posing the greatest potential harm to species considered due to FWS concerns are 

factors such as habitat loss and ecological competition. These factors have historically proved to be of 

greater threat to these species of concern. Impacts may also occur to these species if a hurricane passes 

over an oil spill or causes spills itself. However, at this time, there is no known record of a hurricane 

crossing the path of a large oil spill; the impacts of such have yet to be determined. The experience from 

Hurricanes Katrina and Rita in 2005 was that the oil released during the storms widely dispersed as far as 

the surge reached, reducing impacts from concentrated oil exposure (USDOC, NOAA, 2010). 

Non-OCS oil- and gas-related activities have a greater potential to impact species considered due to 

FWS concerns than OCS oil- and gas-related activities, especially those factors that contribute to habitat 

loss. Because these species rely on terrestrial habitats to carry out their life-history functions at a 

considerable distance from the GOM, the activities of the CPA proposed action are unlikely to have 

significant adverse effects on the size and recovery of any of the above populations. Therefore, the 

incremental contribution of the CPA proposed action would not be likely to result in a significant 

incremental impact on these species within the CPA.

New Information Available Since Publication of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and 

CPA 241/247 and EPA 226 Supplemental EIS 

A search of information sources (FWS’s websites), as well as recently published journal articles, was 

conducted to determine the availability of recent information on species considered due to FWS concerns. 

The search revealed no new information pertinent to this Supplemental EIS. As of February 13, 2015, the 

data available in the species reports on the FWS online environmental conservation system have been 

updated to use a different set of information. The results are based on where species are believed or 

known to occur in order to provide a better representation of species occurrence.

Incomplete or Unavailable Information 

Even after evaluating the information above, BOEM has determined that the new information does 

not change the conclusions of the prior 2012-2017 Gulf of Mexico EISs; nevertheless, there is still 

incomplete or unavailable information. As discussed in Chapter 4.2.1.24 of the 2012-2017 WPA/CPA 

Multisale EIS and WPA 233/CPA 231 Supplemental EIS and Chapter 4.1.1.24 of the CPA 235/241/247 

Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS, BOEM has identified incomplete 

information on the impacts to species considered due to FWS concerns as a result of the Deepwater

Horizon explosion, oil spill, and response because little data have been released to the public. As data 

continue to be gathered and impact assessments completed, a better characterization of the full scope of 

impacts to populations in the GOM from the Deepwater Horizon explosion, oil spill, and response will be 

available. Relevant data on the status of populations after the Deepwater Horizon explosion, oil spill, and 

response may take years to acquire and analyze, and impacts from the Deepwater Horizon explosion, oil 
Description of the Environment and Impact Analysis 4-105

spill, and response may be difficult or impossible to discern from other factors. Therefore, it is not 

possible for BOEM to obtain this information within the timeline contemplated in the NEPA analysis of 

this Supplemental EIS, regardless of the cost or resources needed. In light of the incomplete or 

unavailable information, BOEM’s subject-matter experts have extrapolated from available scientifically 

credible evidence in this analysis. Based on life histories of these species and the fact that they live 

inland, BOEM has determined that these species within the CPA were not affected to any discernible 

degree by the Deepwater Horizon explosion, oil spill, and response. Although the body of available 

information is incomplete, the information extrapolated from life history of the species and distance of the 

Macondo well from their habitats was sufficient to draw reasonable conclusions that they should not have 

been impacted by the Deepwater Horizon explosion, oil spill, and response; therefore, BOEM has 

determined that the incomplete information is not essential to a reasoned choice among alternatives.

Summary and Conclusion

There is a long-standing and well-developed OCS Program of more than 50 years within the CPA, 

and there are no data to suggest that activities from the preexisting OCS Program are significantly 

impacting the above-mentioned species populations; therefore, the CPA proposed action would be 

expected to have little or no effect on the above-mentioned species. Because of the mitigations that may 

be implemented, routine activities (e.g., operational discharges, noise, and marine debris) related to the 

CPA proposed action are not expected to have long-term adverse effects on the size and productivity of 

any of these species or populations in the GOM. Lethal effects could occur from ingestion of accidentally 

released plastic materials from OCS oil- and gas-related and non-OCS oil- and gas-related vessels and 

facilities. However, there have been no reports to date on such incidences. BOEM employs several 

measures (e.g., marine debris mitigations) to reduce the potential impacts to any animal from routine 

activities associated with the CPA proposed action. Accidental oil spills and spill-response activities 

resulting from the CPA proposed action have the potential to impact small to large areas in the GOM, 

depending on the magnitude and frequency of accidents, the ability to respond to accidents, the location

and date of accidents, and various meteorological and hydrological factors (including tropical storms). 

The incremental contribution of the CPA proposed action would not be likely to result in a significant 

incremental impact on the above-mentioned species within the CPA; in comparison, non-OCS oil- and 

gas-related activities, such as habitat loss and competition, have historically proven to be a greater threat 

to the above-mentioned species.

BOEM has reexamined the analysis for species considered due to FWS concerns presented in the 

prior 2012-2017 Gulf of Mexico EISs based on the information presented above. No new significant 

information was discovered that would alter the impact conclusion for species considered due to FWS 

concerns presented in those NEPA documents. The analysis and potential impacts discussed in those 

documents still apply for proposed CPA Lease Sale 247. 

4.1.2. Alternative B—Exclude the Unleased Blocks Near Biologically Sensitive 

Topographic Features

Description of the Alternative

Alternative B differs from Alternative A (the Proposed Action) by not offering blocks that are 

possibly affected by the proposed Topographic Features Stipulation (Chapter 2.3.1.3.1 of this 

Supplemental EIS and Chapter 2.4.1.3.1 of the 2012-2017 WPA/CPA Multisale EIS). All of the 

assumptions (including the nine other potential mitigating measures) and estimates are the same as for the 

proposed action (Alternative A). A description of Alternative A is presented in Chapter 2.3.1.1. There 

are 207 blocks (962,470 ac) in the CPA in which the Topographic Features Stipulation may be applied 

(Figure 2-1). The currently unleased blocks with these features would not be available for lease under 

Alternative B during this proposed lease sale. The number of unleased blocks that would not be offered 

under Alternative B represents only a small percentage of the total number of blocks to be offered under 

Alternative A; therefore, it is assumed that the levels of activity for Alternative B would be essentially the 

same as those projected for the CPA proposed action (refer to Chapter 2.3.2 for further details). The 

estimated amount of resources projected to be developed under Alternative B is within the same scenario 

range as for Alternative A, i.e., 0.116-0.200 BBO and 0.538-0.938 Tcf of gas. 
4-106 Central Planning Area Lease Sale 247 Supplemental EIS

All of the assumptions, including the nine other potential stipulations (i.e., the Live Bottom

Stipulation; Military Areas Stipulation; Evacuation Stipulation; Coordination Stipulation; Blocks South of 

Baldwin County, Alabama, Stipulation; Protected Species Stipulation; United Nations Convention on the 

Law of the Sea Royalty Payment Stipulation; Below Seabed Operations Stipulation; and the Stipulation 

on the Agreement between the United States of America and the United Mexican States Concerning 

Transboundary Hydrocarbon Reservoirs in the Gulf of Mexico, as described in Chapter 2.2.1.3), are the 

same as for the CPA proposed action (Alternative A). A description of Alternative A is presented in 

Chapter 2.3.1.1. The Topographic Features Stipulation would not be applied with Alternative B because 

the blocks that could be affected by the Topographic Features Stipulation would not be offered for lease.

Because the incremental contribution of Alternative A (the Proposed Action) to the cumulative 

impacts on topographic features is expected to be slight and because negative impacts should be restricted 

by the implementation of the Topographic Features Stipulation and site-specific mitigations, the depths of 

the features, and water currents in the topographic feature area, Alternative A is not expected to result in 

adverse impacts greater than Alternative B. Therefore, since both Alternatives A and B minimize the 

potential for adverse impacts to Topographic Features, but since Alternative A better meets the purpose 

and need by providing a greater level of flexibility when considering oil and gas exploration, 

development, and production activities, Alternative A is BOEM’s preferred alternative.

Effects of the Alternative

The following analyses are based on the scenario for the CPA proposed action (Alternative A). The 

scenario provides assumptions and estimates on the amounts, locations, and timing for OCS oil- and gasrelated exploration, development, and production operations and facilities, both offshore and onshore. 

These are estimates only and not predictions of what would happen as a result of holding proposed CPA 

Lease Sale 247. A detailed discussion of the scenario and related impact-producing factors is presented in

Chapter 3.1 of this Supplemental EIS and in Chapter 3.1 of the 2012-2017 WPA/CPA Multisale EIS, and 

updated information is provided in Chapter 3.1 of the WPA 233/CPA 231 Supplemental EIS, CPA 

235/241/247 Supplemental EIS, and CPA 241/247 and EPA 226 Supplemental EIS. 

The analyses of impacts to the various resources under Alternative B are very similar to those for 

Alternative A. The reader should refer to the appropriate discussions under Alternative A for additional 

and more detailed information regarding impact-producing factors and their expected effects on the 

various resources. Impacts under Alternative B are expected to be the same as the CPA proposed action 

(Chapter 4.1.1) for the following resources:

— Air Quality

— Water Quality

— Coastal Barrier Beaches and Associated 

Dunes 

— Wetlands

— Seagrass Communities

— Live Bottoms (Pinnacle Trend and 

Low Relief) 

— Sargassum Communities 

— Chemosynthetic and Nonchemosynthetic 

Deepwater Benthic Communities

— Soft Bottom Benthic Communities 

— Marine Mammals

— Sea Turtles

— Diamondback Terrapins

— Beach Mice

— Coastal and Marine Birds 

— Gulf Sturgeon 

— Fish Resources and Essential Fish 

Habitat

— Commercial Fisheries

— Recreational Fishing 

— Recreational Resources

— Archaeological Resources

— Human Resources and Land Use 

— Species Considered due to U.S. Fish and 

Wildlife Service Concerns 

The impacts to some Gulf of Mexico resources under Alternative B would be slightly different from 

the impacts expected under the CPA proposed action (Alternative A). These impacts are described 

below. 
Description of the Environment and Impact Analysis 4-107

Impacts on Topographic Features 

The sources and severity in impacts associated with this alternative are those lease sale-related 

activities discussed for the CPA proposed action. The potential impact-producing factors to the 

topographic features of the CPA are anchoring and structure emplacement, effluent discharge, loss of well 

control events, oil spills, and structure removal. A more detailed discussion of these potential impactproducing factors and the appropriate mitigating measures are presented in Chapter 2.3.1.3.1 of this 

Supplemental EIS and Chapter 2.4.1.3.1 of the 2012-2017 WPA/CPA Multisale EIS. 

Impacts of Routine Activities and Accidental Events

Of the 16 topographic features in the CPA, 16 are located within water depths less than 210 m 

(689 ft). Combined, these features occupy a small portion of the CPA. Of the potential impact-producing 

factors that may affect topographic features, anchoring, structure emplacement, effluent discharge, loss of 

well control, and structure removal would be eliminated by the adoption of this alternative because blocks 

near enough to the banks for these events to have an impact on the biota of the banks would have been 

excluded from leasing under this alternative. Thus, the only impact-producing factor remaining from 

routine operations in blocks included in this alternative (i.e., those blocks not excluded by this alternative) 

is an oil spill. The potential impacts from oil spills are summarized below and are discussed further in 

Chapter 3.2.1 of this Supplemental EIS and Chapter 3.2.1 of the 2012-2017 WPA/CPA Multisale EIS, 

WPA 233/CPA 231 Supplemental EIS, CPA 235/241/247 Supplemental EIS, and CPA 241/247 and EPA 

226 Supplemental EIS. 

A subsurface spill would have no effect on a biologically sensitive feature unless the oil or its 

dissolved components comes into direct contact with the habitat. Oil from a subsurface spill is expected 

to rise to the sea surface, based on the specific gravity of Gulf of Mexico oil. An exception to this could 

occur if oil is released at the seafloor under pressures associated with depths beyond the coastal shelf. 

This can result in the atomization of oil into micro-droplets with little buoyancy. Under these conditions, 

a subsea oil plume could most likely travel laterally with the prevailing currents, although it could 

potentially travel upslope during an upwelling event. However, upwelling events are limited to a specific 

set of meteorological conditions (Zavala-Hidalgo et al., 2006; Walker, 2005; Feng et al., 2014). This can 

also happen if chemical dispersants are used underwater, forming a plume. If a subsea oil plume does 

form, the oil is expected to be swept clear of the banks because prevailing currents travel around the 

banks rather than over them (Rezak et al., 1983). As the oil travels in the water column, it will become 

diluted from its original concentration. Transient concentrations of oil below 20 ppm are not expected to 

result in lasting harm to a coral reef (Shigenaka, 2001). Another exception, although unlikely, is the 

potential mixing of oil and/or dispersant contaminated surface waters throughout the water column during 

a tropical storm (Silva et al., 2015). If surface waters were mixed to depth and were to come into contact 

with a topographic feature near the shelf edge, it is possible that there could be damage to benthic 

communities on topographic features. The fact that the topographic features are widely dispersed in the 

CPA, combined with the random nature of spill events, would serve to limit the likelihood of a spill 

occurring near a topographic feature. In addition, the exclusion of blocks adjacent to topographic features 

from the proposed CPA lease sale would further distance potential spills from the habitat. Chapter 4.2.1.7 

of the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS, and Chapter 

4.1.1.7 of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS 

discuss the risk of spills interacting with topographic features in more detail. The currents that move 

around the banks would likely steer any spilled oil around the banks rather than directly upon them, 

lessening impact severity. In the unlikely event that oil from a subsurface spill would reach the biota of a 

topographic feature, the effects would be primarily sublethal for most of the adult sessile biota. Lethal 

effects would probably be limited to a few coral colonies (CSA, 1992 and 1994). If oil from a subsurface 

spill contacted a coral-covered area, the areal extent of coral mortality would be limited, but long-lasting 

sublethal effects may be incurred by organisms surviving the initial effects of a spill (Jackson et al., 

1989). Stress resulting from the oiling of reef coral colonies could affect their resilience to natural 

disturbances (e.g., elevated water temperature and diseases) and may hamper their ability to reproduce. A 

complete recovery of such an affected area could take in excess of 10 years. Similarly, contaminated 

surface waters mixed by a tropical storm event to depth could have similar lethal and sublethal effects to 

communities of a topographic feature (Silva et al., 2015). 
4-108 Central Planning Area Lease Sale 247 Supplemental EIS

Cumulative Impacts

With the exception of the topographic features, the cumulative impacts of Alternative B on the 

environmental and socioeconomic resources of the CPA would be identical to Alternative A. The 

incremental contribution of the CPA proposed action to the cumulative impacts on topographic features is 

expected to be slight, and negative impacts should be restricted by the implementation of the Topographic 

Features Stipulation and site-specific mitigations, the depths of the features, and water currents in the 

topographic feature area.

Summary and Conclusion

Alternative B, if adopted, would prevent any OCS oil- and gas-related activity whatsoever in the 

blocks containing topographic features and their surrounding protective zones; thus, it would eliminate 

any potential direct impacts to the biota of those blocks from routine oil- and gas-related activities within 

the blocks. In the unlikely event that oil from a subsurface spill contacts the biota of a topographic 

feature, the effects would be localized and primarily sublethal for most of the adult sessile biota. Some 

lethal effects would probably occur upon oil contact to coral colonies.

Environmental impacts of Alternative B would be almost indistinguishable from Alternative A with 

the Topographic Features Stipulation in place. There would be an economic impact to the extent that 

economic returns from the excluded lease blocks would not be realized.

4.1.3. Alternative C—No Action

Description of the Alternative

Alternative C is the cancellation of the proposed CPA lease sale. If this alternative is chosen, the 

opportunity for development of the estimated 0.460-0.894 BBO and 1.939-3.903 Tcf of gas that could 

have resulted from the proposed CPA lease sale would be precluded during the current 2012-2017 FiveYear Program, but it could again be contemplated as part of a future Five-Year Program. Proposed CPA 

Lease Sale 247 is the last CPA lease sale in the current Five-Year Program. Typically, in past programs, 

there were planning area lease sales, with one CPA lease sale per year. However, the 2017-2022 

Five-Year Program may have two regionwide lease sales each year, and future lease sales will be 

dependent on decisions made in the 2017-2022 Five-Year Program, as determined in the Final Program 

document. The No Action alternative encompasses the same potential impacts as a decision to delay the 

proposed CPA lease sale to a later scheduled lease sale under the 2017-2022 Five-Year Program, when 

another decision on whether to hold that future lease sale is made. Delay of the proposed CPA lease sale 

was not considered as a separate alternative from Alternative C because the potential impacts are the 

same, namely that most impacts related to Alternative A would not occur as described below. Any 

potential environmental impacts resulting from the proposed CPA lease sale would not occur or would be 

postponed to a future lease sale decision. This alternative is also analyzed in the EIS for the 2012-2017 

Five-Year Program on a nationwide programmatic level.

Effects of the Alternative

BOEM’s predecessor agency published a report that examined previous exploration and development 

activity scenarios (USDOI, MMS, 2007). The report compared forecasted activity with the actual activity 

from 14 WPA and 14 CPA lease sales. The report shows that many lease sales contribute to the present 

level of OCS oil- and gas-related activity, and any single lease sale accounts for only a small percentage 

of the total OCS oil- and gas-related activities. In 2006, leases from 92 different sales contributed to Gulf 

of Mexico production. An average WPA lease sale contributed to 3 percent of oil production and 

3 percent of gas production in the WPA, while an average CPA lease sale contributed to 2 percent of oil 

production and 2 percent of gas production in the CPA. In 2006, leases from 15 different sales 

contributed to the installation of production structures in the Gulf of Mexico. An average WPA lease sale 

contributed to 6 percent of the installation of production structures in the WPA, while an average CPA 

lease sale contributed to 6 percent of the installation of production structures in the CPA. In 2006, leases 

from 70 different sales contributed to wells drilled in the Gulf of Mexico. An average WPA lease sale 
Description of the Environment and Impact Analysis 4-109

contributed to 6 percent of the wells drilled in the WPA, while an average CPA lease sale contributed to 

4 percent of the wells drilled in the CPA.

As in the past, the proposed CPA lease sale would contribute to maintaining the present level of OCS 

oil- and gas-related activity in the Gulf of Mexico. Exploration and development activity, including 

service-vessel trips, helicopter trips, and construction that would result from the proposed CPA lease sale 

would replace activity resulting from existing leases that have reached, or are near the end of, their 

economic life.

In the short term, however, it is important to note that activities under previous lease sales would 

continue in the Gulf of Mexico, including exploration, development, production, and decommissioning

activities. As a decision on the proposed CPA lease sale will not affect those preexisting leases and 

activities related to them, there may still be environmental impacts occurring in the Gulf in the short term, 

even if the proposed CPA lease sale is cancelled.

Environmental Impacts

If the proposed CPA lease sale were to be cancelled, the resulting development of oil and gas would 

most likely occur as the result of a future lease sale; therefore, the overall level of OCS oil- and gasrelated activity in the CPA would only be reduced by a small percentage, if any. Therefore, the 

cancellation of the proposed CPA lease sale would not significantly change the environmental impacts of 

overall OCS oil- and gas-related activity in the long term. The environmental impacts expected to result 

from the CPA proposed action, which are described above, would not occur in the short term, but they 

would likely be postponed to any future lease sale. 

Economic Impacts 

Although environmental impacts may be reduced or postponed by cancelling the proposed CPA lease 

sale, the economic impacts of cancelling the scheduled lease sale should be given consideration. Chapter 

4.2.1.23.3 of the 2012-2017 WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS, and 

Chapter 4.1.1.23.3 of the CPA 235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 

Supplemental EIS discuss the potential economic impacts of the CPA proposed action. In the event that 

the proposed CPA lease sale is cancelled or postponed, there may be impacts to employment along the 

Gulf Coast, but these are not expected to be significant (e.g., not cause employment effects >1% in any 

EIA along the Gulf Coast or less than 1% of total employment) or long term given the existing OCS 

infrastructure. 

Federal, State, and local governments would also have to forgo the revenue that would have been 

received from the proposed CPA lease sale. There could be minor impacts on global energy prices from 

cancelling the proposed CPA lease sale, along with minor changes in energy consumption patterns that 

would result from these price changes.

Other factors may minimize or exacerbate the economic impacts of cancelling the proposed CPA 

lease sale. For example, the longer-term economic impacts of cancelling the CPA proposed lease sale 

could be minimized if they were offset by a larger lease sale at a later date. The economic impacts may 

be exacerbated if additional lease sales are cancelled. The OCS industry is dependent on high capital 

investment costs and there may be long lags between the lease sale and the majority of production 

activities. Therefore, firms’ investment and spending decisions are dependent on their confidence that the 

OCS Program will be maintained in the future. In addition, while firms in the OCS industry are generally 

likely to be able to weather the cancellation of a single lease sale, the cancellation of multiple lease sales 

could lead to broader damage to firms and workers in the industry or decisions to operate in areas other 

than the Gulf. These economic impacts would be particularly damaging to the coastal counties and 

parishes in Texas and Louisiana for which the OCS industry as a whole is an important component of 

their economies. 

Summary and Conclusion

Cancelling the proposed CPA lease sale would eliminate the effects described for Alternative A 

(Chapter 4.1.1); however, any single lease sale in the CPA accounts for only a small percentage of the 

total OCS oil- and gas-related activities in the GOM. If the proposed CPA lease sale were to be 

cancelled, the resulting development of oil and gas would most likely be postponed to a future lease sale; 
4-110 Central Planning Area Lease Sale 247 Supplemental EIS

therefore, the overall level of OCS oil- and gas-related activity in the CPA would only be reduced by a 

small percentage, if any. Therefore, the cancellation of the proposed CPA lease sale would not 

significantly change the environmental impacts of overall OCS oil- and gas-related activity in the long 

term.

Federal, State, and local governments would have to forgo the revenue that would have been received 

from the proposed CPA lease sale. There could be minor impacts on global energy prices from cancelling 

the proposed CPA lease sale, along with minor changes in energy consumption patterns that would result 

from these price changes. Other factors may minimize or exacerbate the economic impacts of cancelling 

the proposed CPA lease sale.

4.2. UNAVOIDABLE ADVERSE IMPACTS OF THE PROPOSED ACTION

Unavoidable adverse impacts associated with the CPA proposed action are expected to be primarily 

short term and localized in nature and are summarized below. Adverse impacts from low-probability 

catastrophic events, which are not a part of the CPA proposed action and not likely expected to occur,

could be of longer duration and extend beyond the local area. All OCS oil- and gas-related activities 

involve temporary and exclusive use of relatively small areas of the OCS over the lifetimes of specific 

projects. Lifetimes for these activities can be days, as in the case of seismic surveys; or decades, as in the 

case of a production structure or platform. No activities in the OCS Program involve the permanent or 

temporary use or “taking” of large areas of the OCS on a semicontinuous basis. Cumulatively, however, 

a multitude of individual projects results in a major use of OCS space.

Sensitive Coastal Habitats: If an oil spill contacts beaches or barrier islands, the removal of beach 

sand during cleanup activities could result in adverse impacts if the sand is not replaced. In addition, a 

beach could experience several years of tarballs washing ashore over time, causing an aesthetic impact. 

Sand borrowing on the OCS for coastal restorations involves the taking of a quantity of sand from the 

OCS and depositing it onshore, essentially moving small products of the deltaic system to another 

location. If sand is left where it is, it would eventually be lost to the deltaic system by redeposition or 

burial by younger sediments; if transported onshore, it would be lost to burial and submergence caused by 

subsidence and sea-level rise.

If an oil spill contacts coastal wetlands, adverse impacts could be high in localized areas. In more 

heavily oiled areas, wetland vegetation could experience suppressed productivity for several years; in 

more lightly oiled areas, wetland vegetation could experience die-back for one season. Epibionts on 

wetland vegetation and grasses in the tidal zone could be killed, and the productivity of tidal marshes for 

the vertebrates and invertebrates that use them to spawn and develop could be impaired. Much of the 

wetland vegetation would recover over time, but some wetland areas could be converted to open water. 

Some unavoidable impacts could occur during pipeline and other related coastal construction, but 

regulations are in place to avoid and minimize these impacts to the maximum extent practicable. 

Unavoidable impacts resulting from dredging, wake erosion, and other secondary impacts related to 

channel use and maintenance would occur as a result of the CPA proposed action.

Sensitive Coastal and Offshore Biological Habitats: Unavoidable adverse impacts would take place 

if an oil spill occurred and contacted sensitive coastal and offshore biological habitats, such as Sargassum 

at the surface; fish, turtles, and marine mammals in the water column; or benthic habitats on the bottom. 

There could be some adverse impacts on organisms contacted by oil, dispersant chemicals, or emulsions 

of dispersed oil droplets and dispersant chemicals that, at this time, are not completely understood, 

particularly in subsurface environments.

Water Quality: Routine offshore operations would cause some unavoidable adverse impacts to 

varying degrees on the quality of the surrounding water. Drilling, construction, overboard discharges of 

drilling mud and cuttings, and pipelaying activities would cause an increase in the turbidity of the affected 

waters for the duration of the activity periods. This, however, would only affect water in the immediate 

vicinity of the construction activity or in the vicinity of offshore structures, rigs, and platforms. The 

discharge of treated sewage from manned rigs and platforms would increase the levels of suspended 

solids, nutrients, chlorine, and biochemical oxygen demand in a small area near the discharge point for a 

short period of time. Accidental spills from platforms and the discharge of produced waters could result 

in increases of hydrocarbon levels and trace metal concentrations in the water column in the vicinity of 

the platforms. Spilled oil from a tanker collision would affect the water surface in combination with 

dispersant chemicals used during spill response. A subsurface loss of well control would subject the 
Description of the Environment and Impact Analysis 4-111

surface, water column, and near-bottom environment to spilled oil and gas released from solution, 

dispersant chemicals, or emulsions of dispersed oil droplets and dispersant chemicals.

Unavoidable impacts to onshore water quality would occur as a result of chronic point- and nonpointsource discharges such as runoff and effluent discharges from existing onshore infrastructure used in 

support of lease sale activities. Vessel traffic contributes to the degradation of water quality by chronic 

low-quantity oil leakage, treated sanitary and domestic waste, bilge water, and contaminants known to 

exist in ship paints. Regulatory requirements of the State and Federal water authorities and some local 

jurisdictions would be applicable to point-source discharges from support facilities such as refineries and 

marine terminals.

Air Quality: Unavoidable short-term impacts on air quality could occur after large oil spills because 

of evaporation and volatilization of the lighter components of crude oil, combustion from surface burning, 

and aerial spraying of dispersant chemicals. Short-term effects from spill events are uncontrollable and 

are likely to be aggravated or mitigated by the time of year the spills take place. Mitigation of long-term 

effects from offshore engine combustion during routine operations would be accomplished through 

existing regulations and the development of new control emission technology. 

Threatened and Endangered Species: Because the proposed CPA lease sale does not in and of itself 

make any irreversible or irretrievable commitment of resources that would foreclose the development or 

implementation of any reasonable and prudent measures to comply with the Endangered Species Act, 

BOEM may proceed with publication of this Supplemental EIS and finalize a decision among these 

alternatives even if consultation is not complete, consistent with Section 7(d) of the ESA (also refer to 

Chapter 5.7). Irreversible loss of individuals that are ESA-listed species may occur after a large oil spill

from the acute impact of being oiled or the chronic impact of oil having eliminated, reduced, or rendered 

suboptimal the food species upon which they were dependent. 

Nonendangered and Nonthreatened Marine Mammals: Unavoidable adverse impacts to 

nonendangered and nonthreatened marine mammals would be those that also affect endangered and 

threatened marine mammal species. Routine operation impacts (such as seismic surveys, water quality

and habitat degradation, helicopter disturbance, vessel collision, and discarded trash and debris) would be 

negligible or minor to a population, but they could be lethal to individuals as in the case of a vessel 

collision. A large oil spill would temporarily degrade habitat if spilled oil, dispersant chemicals, or 

emulsions of dispersed oil droplets and dispersant chemicals contact free-ranging pods or spawning 

grounds. 

Coastal and Marine Birds: Unavoidable adverse impacts from routine operations on coastal birds 

could result from helicopter and OCS service-vessel traffic, facility lighting, and floating trash and debris. 

Marine birds could be affected by noise, platform lighting, aircraft disturbances, and trash and debris 

associated with offshore activities. Cross-Gulf migrating species could be affected by lighted platforms, 

helicopter and vessel traffic, and floating trash and debris. If a large oil spill occurs and contacts coastal 

or marine bird habitats, some birds could experience lethal and sublethal impacts from oiling, and birds 

feeding or resting in the water could be oiled and die. Coastal birds coming into contact with oil may 

migrate more deeply into marsh habitats, out of reach from spill responders seeking to count them or 

collect them for rehabilitation. Oil spills and oil-spill cleanup activities could also affect the food species 

for coastal, marine, and migratory bird species. Depending on the time of year, large oil spills could 

decrease the nesting success of species that concentrate nests in coastal environments due to direct effects 

of the spill and also disruption from oil-spill cleanup activities.

Fish Resources, Commercial Fisheries, and Recreational Fishing: Unavoidable adverse impacts 

from routine operations are loss of open ocean or bottom areas desired for fishing by the presence or 

construction of OCS oil- and gas-related facilities and pipelines. Loss of gear could occur from bottom 

obstructions around platforms and subsea production systems. Routine discharges from vessels and 

platforms are minor given the available area for fish habitat. If a large oil spill occurs, the oil, dispersant

chemicals, or emulsions of oil droplets and dispersant chemicals could temporarily displace mobile fish 

species on a population or local scale. There could also be impacts on prey and sublethal effects on fish. 

It is unlikely that fishermen would want, or be permitted, to harvest fish in the area of an oil spill, as 

spilled oil could coat or contaminate commercial fish species, rendering them unmarketable.

Recreational Beaches: Unavoidable adverse impacts from routine operations may result in the 

accidental loss overboard of some floatable debris that may eventually come ashore on frequented 

recreational beaches. A large oil spill could make landfall on recreational beaches, leading to local or 

regional economic losses and stigma effects, causing potential users to avoid the area after acute impacts 
4-112 Central Planning Area Lease Sale 247 Supplemental EIS

have been removed. Some recreational beaches become temporarily soiled by weathered crude oil, and 

tarballs may come ashore long after stranded oil has been cleaned from shoreline areas.

Economic Activity: Net economic, political, and social benefits accrue from the production of 

hydrocarbon resources. Once these benefits become routine, unavoidable adverse impacts from routine 

operations follow trends in supply and demand based on the commodity prices for oil, gas, and refined 

hydrocarbon products. Declines in oil and gas prices can lead to activity ramp downs by operators until 

prices rise. A large oil spill would cause temporary increases in economic activity associated with spillresponse activity. An increase in economic activity from the response to a large spill could be offset by 

temporary work stoppages that are associated with spill-cause investigations and would involve a transfer 

or displacement of demand to different skill sets. An oil spill could also negatively impact industries such 

as tourism and fishing. Routine operations affected by new regulations that are incremental would not 

have much effect on the baseline of economic activity; however, temporary work stoppages or the 

introduction of several new requirements at one time, which are costly to implement, could cause a dropoff of activity as operators adjust to new expectations or use the opportunity to move resources to other 

basins where they have interests.

Archaeological Resources: Unavoidable adverse impacts from routine operations could lead to the 

loss of unique or significant archaeological information if unrecognized at the time an area is disturbed. 

Required archaeological surveys significantly reduce the potential for this loss by identifying potential 

archaeological sites prior to an interaction occurring, thereby making avoidance or mitigation of impacts 

possible. A large oil spill that makes landfall on or near protected archaeological landmarks could cause 

loss of aesthetic value, contamination of material remains, loss of radiocarbon-dating potential, direct 

impacts from oil-spill cleanup activities, and/or looting. 

4.3. IRREVERSIBLE AND IRRETRIEVABLE COMMITMENT OF RESOURCES

Irreversible or irretrievable commitment of resources refers to impacts or losses to resources that 

cannot be reversed or recovered. Examples are when a species becomes extinct or when wetlands are 

permanently converted to open water. In either case, the loss is permanent.

Wetlands: An irreversible or irretrievable loss of wetlands and associated biological resources could 

occur if wetlands are permanently lost because of impacts caused by dredging and construction activities 

that displace existing wetlands or from oil spills severe enough to cause permanent die-back of vegetation 

and conversion to open water. Construction and emplacement of onshore pipelines in coastal wetlands 

displace coastal wetlands in disturbed areas that are then subject to indirect impacts like saltwater 

intrusion or erosion of the marsh soils along navigation channels and canals. Ongoing natural and 

anthropogenic processes in the coastal zone, only one of which is OCS oil- and gas-related activity, can 

result in direct and indirect loss of wetlands. Natural losses as a consequence of the coastal area 

becoming hydrologically isolated from the Mississippi River that built it, sea-level rise, and subsidence of 

the delta platform in the absence of new sediment added to the delta plain appear to be much more 

dominant processes impacting coastal wetlands. 

Sensitive Nearshore and Offshore Biological Resources: An irreversible loss or degradation of 

ecological habitat caused by cumulative activity tends to be incremental over the short term. Irretrievable 

loss may not occur unless or until a critical threshold is reached. It can be difficult or impossible to 

identify when that threshold is, or would be, reached. Oil spills and chronic low-level pollution can injure 

and kill organisms at virtually all trophic levels. Mortality of individual organisms can be expected to 

occur, and possibly a reduction or even elimination of a few small or isolated populations. The proposed 

biological stipulations, however, are expected to eliminate most of these risks.

Threatened and Endangered Species: Irreversible loss of individuals that are protected species may 

occur after a large oil spill from the acute impact of being oiled or the chronic impact of oil having 

eliminated, reduced, or rendered suboptimal the food species upon which they were dependent. 

Fish Resources and Commercial Fisheries: Irreversible loss of fish and coral resources, including 

commercial and recreational species, are caused by structure removal using explosives. Fish in proximity 

to an underwater explosion can be killed. Without the structure to serve as habitat area, sessile, attached 

invertebrates and the fish that live among them are absent. Removing structures eliminates these special 

and local habitats and the organisms living there, including such valuable species as red snapper. 

Continued structure removal, regardless of the technique used, would reduce the net benefits to 

commercial fishing due to the presence of these structures.
Description of the Environment and Impact Analysis 4-113

Recreational Beaches: Impacts on recreational beaches from a large oil spill may, at the time, seem 

irreversible, but the impacts are generally temporary. Beaches fouled by a large oil spill would be 

temporarily unavailable to the people who would otherwise frequent them, but only during the period 

between landfall and cleanup of the oil, followed by an indefinite lag period during which stigma effects 

recede from public consciousness.

Archaeological Resources: Irreversible loss of a prehistoric or historic archaeological resource can 

occur if bottom-disturbing activity takes place without the surveys, where required, to demonstrate its 

absence before work proceeds. A resource can be completely destroyed, severely damaged, or the 

scientific context badly impaired by well drilling, subsea completions, and platform and pipeline

installation, or sand borrowing. 

Oil and Gas Development: Leasing and subsequent development and extraction of hydrocarbons as a 

result of the CPA proposed action represents an irreversible and irretrievable commitment by the removal 

and consumption of nonrenewable oil and gas resources. The estimated amount of resources to be 

recovered as a result of the CPA proposed action is presented in Table 3-1. 

Loss of Human and Animal Life: The OCS oil and gas exploration, development, production, and 

transportation are carried out under comprehensive, state-of-the-art, enforced regulatory procedures 

designed to ensure public and work place safety and environmental protection. Nevertheless, some loss 

of human and animal life may be inevitable from unpredictable and unexpected acts of man and nature 

(i.e., unavoidable accidents, accidents caused by human negligence or misinterpretation, human error, 

willful noncompliance, and adverse weather conditions). Some normal and required operations, such as 

structure removal, can kill sea life in proximity to explosive charges or by removal of the structure that 

served as the framework for invertebrates living on it and the fish that lived with it.

4.4. RELATIONSHIP BETWEEN THE SHORT-TERM USE OF MAN’S ENVIRONMENT 

AND THE MAINTENANCE AND ENHANCEMENT OF LONG-TERM PRODUCTIVITY

The short-term effects on various components of the environment in the vicinity of the CPA proposed 

action are related to long-term effects and the maintenance and enhancement of long-term productivity. 

Short-Term Use

Short-term refers to the total duration of oil and gas exploration and production activities. Extraction 

and consumption of offshore oil and natural gas is a short-term benefit. Discovering and producing 

domestic oil and gas now reduces the Nation’s dependency on foreign imports. Depleting a 

nonrenewable resource now removes these domestic resources from being available for future use. The 

production of offshore oil and natural gas as a result of the CPA proposed action would provide shortterm energy, and as it delays the increase in the Nation’s dependency on foreign imports, it can also allow 

additional time for ramp-up and development of long-term renewable energy sources or substitutes for 

nonrenewable oil and gas. Economic, political, and social benefits would accrue from the availability of 

these natural resources.

The principle short-term use of the leased areas in the Gulf of Mexico would be for the production of 

0.460-0.894 BBO and 1.939-3.903 Tcf of gas from a typical CPA proposed action. The cumulative 

impacts scenario in this Supplemental EIS extends approximately from 2012 to 2051. The 40-year time 

period is used because it is the approximate longest life span of activities conducted on an individual 

lease. The 40 years following the proposed CPA lease sale is the period of time during which the 

activities and impacting factors that follow as a consequence of the proposed CPA lease sale would be 

influencing the environment. 

The specific impacts of the CPA proposed action vary in kind, intensity, and duration according to the 

activities occurring at any given time (Chapter 3). Initial activities, such as seismic surveying and 

exploration drilling, result in short-term, localized impacts. Development drilling and well workovers 

occur sporadically throughout the life of the CPA proposed action but also result in short-term, localized 

impacts. Activities during the production life of a platform may result in chronic impacts over a longer 

period of time (over 25 years), potentially punctuated by more severe impacts as a result of accidental 

events or a spill. Platform removal is also a short-term activity with localized impacts, including removal 

of the habitat for encrusting invertebrates and fish living among them. Many of the effects on physical, 

biological, and socioeconomic resources discussed in Chapters 4.1 and 4.2 are considered to be short 
4-114 Central Planning Area Lease Sale 247 Supplemental EIS

term (being greatest during the construction, exploration, and early production phases). These impacts 

would be further reduced by the mitigating measures discussed in Chapter 2.2.2. 

The OCS oil- and gas- related development off Louisiana, Mississippi, and Alabama has enhanced 

recreational and commercial fishing activities, which in turn has stimulated the manufacture and sale of 

larger private fishing vessels and specialized recreational fishing equipment. Commercial enterprises 

such as charter boats have become heavily dependent on offshore structures for satisfying recreational 

customers. The CPA proposed action could increase these incidental benefits of offshore development. 

Offshore fishing and diving have gradually increased in the past three decades, with offshore structures 

and platforms becoming the focus of much of that activity. As mineral resources become depleted, 

platform removals would occur and may result in a decline in these activities.

The short-term exploitation of hydrocarbons for the OCS Program in the Gulf of Mexico may have 

long-term impacts on biologically sensitive coastal and offshore resources and areas if a large oil spill

occurs. A spill and spill-response activity could temporarily interfere with commercial and recreational 

fishing, beach use, and tourism in the area where the spill makes landfall and in a wider area based on 

stigma effects. The proposed leasing may also result in onshore development and population increases 

that could cause very short-term adverse impacts to local community infrastructure, particularly in areas 

of low population and minimal existing industrial infrastructure (Chapter 4.2.1.23.1 of the 2012-2017 

WPA/CPA Multisale EIS and WPA 233/CPA 231 Supplemental EIS, and Chapter 4.1.1.23.1 of the CPA 

235/241/247 Supplemental EIS and CPA 241/247 and EPA 226 Supplemental EIS).

Relationship to Long-Term Productivity

Long-term refers to an indefinite period beyond the termination of oil and gas production. Over a 

period of time after peak oil production has occurred in the Gulf of Mexico, a gradual easing of the 

specific impacts caused by oil and gas exploration and production would occur as the productive 

reservoirs in the Gulf have been discovered and produced, and have become depleted. The Oil Drum 

(2009) showed a graphic demonstrating that peak oil production in the Gulf occurred in June 2002 at 

1.73 MMbbl per day. Whether or not this date is correct can only be known in hindsight and only after a 

period of years while production continues. At this time, however, the trend is fairly convincing (The Oil 

Drum, 2009). There is disagreement on what future production trends may be in the Gulf of Mexico after 

several operators, BP among them, announced discoveries over the last 5 years (Oil and Gas Journal, 

2009) in the Lower Tertiary in ultra-deepwater (>5,000 ft; 1,524 m) with large projected reserves. These 

claims are as yet unproven and there are questions as to the difficulties that may be encountered 

producing these prospects because of their geologic age; burial depth and high-temperature, high-pressure 

in-situ conditions; lateral continuity of reservoirs; and the challenges of producing from ultra-deepwater 

water depths.

The Gulf of Mexico’s large marine ecosystem is considered a Class II, moderately productive 

ecosystem (mean phytoplankton primary production 150-300 g Chlorophyll a/m2

-yr [The Encyclopedia 

of Earth, 2008]) based on Sea-viewing Wide Field-of-view Sensor (SeaWiFS) global primary 

productivity estimates (USDOC, NASA, 2003). After the completion of oil and gas production, a gradual 

ramp-down to economic conditions without OCS oil- and gas-related activity would be experienced, 

while the marine environment is generally expected to remain at or return to its normal long-term 

productivity levels that, in recent years, has been described as stressed (The Encyclopedia of Earth, 2008). 

The Gulf of Mexico’s large marine ecosystem shows signs of ecosystem stress in bays, estuaries, and 

coastal regions (Birkett and Rapport, 1999). There is shoreline alteration, pollutant discharge, oil and gas 

development, and nutrient loading. The overall condition for the U.S. section of this large marine 

ecosystem, according to the USEPA’s seven primary indicators (Jackson et al., 2000), is good dissolved 

oxygen, fair water quality, poor coastal wetlands, poor eutrophic condition, and poor sediment, benthos, 

and fish tissue (The Encyclopedia of Earth, 2008). 

To help sustain the long-term productivity of the Gulf of Mexico ecosystem, the OCS Program 

provides structures to use as site-specific artificial reefs and fish-attracting devices for the benefit of 

commercial and recreational fishermen and to sport divers and spear fishers. Additionally, the OCS 

Program continues to improve the knowledge and mitigation practices used in offshore development. 

Approximately 10 percent of the oil and gas structures removed from the OCS are eventually used for 

State artificial reef programs.
CHAPTER 5 

CONSULTATION AND COORDINATION

Consultation and Coordination 5-3 

5. CONSULTATION AND COORDINATION

5.1. DEVELOPMENT OF THE PROPOSED ACTION

This Supplemental EIS addresses one proposed oil and gas lease sale in the CPA (Lease Sale 247) of 

the Gulf of Mexico, as scheduled in the Five-Year Program (USDOI, BOEM, 2012a) (Figure 1-1). 

BOEM conducted early coordination with appropriate Federal and State agencies and other concerned 

parties to discuss and coordinate the prelease process for the proposed lease sale and this Supplemental 

EIS. Key agencies and organizations included the National Oceanic and Atmospheric Administration, 

NOAA’s National Marine Fisheries Service, FWS, National Park Service, U.S. Coast Guard, U.S.

Department of Defense, USEPA, State Governors’ offices, Tribal Nations, nongovernmental 

organizations, and industry groups.

5.2. CALL FOR INFORMATION AND NOTICE OF INTENT TO PREPARE A

SUPPLEMENTAL EIS 

On July 9, 2012, the Call for Information (Call) for proposed CPA Lease Sales 231, 235, 241, and 

247 was published in the Federal Register (2012b). The 30-day comment period closed on August 8, 

2012. BOEM received two comment letters in response to the Call. These comments are summarized 

below in Chapter 5.3.1. 

On August 17, 2015, the Notice of Intent to Prepare a Supplemental EIS (NOI) for proposed CPA 

Lease Sale 247 was published in the Federal Register. Additional public notices were distributed via 

local newspapers, the U.S. Postal Service, and the Internet. The 30-day comment period for the NOI 

closed on September 16, 2015. Federal, State, and local governments, Tribal Nations, nongovernmental 

organizations, and other interested parties were invited to send written comments to the Gulf of Mexico 

OCS Region on the scope of the Supplemental EIS. BOEM received one comment letter, three emails, 

and one submission to www.regulations.gov in response to the NOI. The comments that the National 

Park Service provided by letter and email were the same. These comments are summarized below in 

Chapter 5.3.2. 

5.3. DEVELOPMENT OF THE DRAFT SUPPLEMENTAL EIS 

Scoping for the Draft Supplemental EIS was conducted in accordance with CEQ regulations for 

implementing NEPA. Scoping provides those with an interest in the OCS Program an opportunity to 

provide comments on the proposed action. In addition, scoping provides BOEM an opportunity to update 

the Gulf of Mexico OCS Region’s environmental and socioeconomic information base. Public scoping 

meetings were held in Alabama, Mississippi, and Louisiana on the following dates and at the times and

locations indicated below: 

Tuesday, September 1, 2015 Wednesday, September 2, 2015

4:00 p.m. CDT 6:00 p.m. CDT

Hilton Garden Inn Mobile West Courtyard Marriott, Gulfport Beachfront

828 West I-65 Service Road South 1600 East Beach Boulevard

Mobile, Alabama 36609 Gulfport, Mississippi 39501

3 registered attendees 0 registered attendees

1 speaker 0 speakers
5-4 Central Planning Area Lease Sale 247 Supplemental EIS

Thursday, September 3, 2015

1:00 p.m. CDT

Bureau of Ocean Energy Management 

Gulf of Mexico OCS Region

1201 Elmwood Park Blvd.

New Orleans, Louisiana 70123

4 registered attendees

1 speaker

5.3.1. Summary of Comments Received in Response to the Calls for Information

In response to the Call for proposed CPA Lease Sales 231, 235, 241, and 247, BOEM received two 

comment letters: one letter from the Louisiana Department of Natural Resources and one letter from the 

American Petroleum Institute (API). The Louisiana Department of Natural Resources hopes that BOEM 

will be more attentive to the State of Louisiana’s comments during the prelease planning phase, believes 

that a better appraisal of coastal effects is necessary, and believes that BOEM must more efficiently 

revisit reviews of earlier OCS lease sales to determine whether the models and predictive techniques used 

were accurate. The API states that annual, predictable lease sales in these planning areas are needed to 

help ensure continued offshore exploration and production in the future because production from lease 

sales will take many years to develop. The API further encourages BOEM to pursue legislation that will 

allow the entry into force of the “Agreement between the United States of America and the United 

Mexican States Concerning Transboundary Hydrocarbon Reservoirs in the Gulf of Mexico” (Agreement). 

This Agreement, which was signed after issuance of the Call and entered into force on July 18, 2014, 

governs the development of reservoirs of petroleum and natural gas straddling the U.S.-Mexico maritime 

and continental shelf boundary in the Gulf of Mexico. 

5.3.2. Summary of Scoping Comments

Comments (both verbal and written) were received from the NOI and three scoping meetings from 

Federal and State government agencies; interest groups; industry; businesses; and the general public on 

the scope of this Supplemental EIS, significant issues that should be addressed, alternatives that should be 

considered, and mitigating measures. All scoping comments received, which were appropriate for a lease 

sale NEPA document, were considered in the preparation of the Draft Supplemental EIS. BOEM 

received one comment letter via mail on the NOI, three comments via email, and one comment via 

www.regulations.gov during the scoping process. The comments that the National Park Service provided 

by letter and email were the same. A total of two speakers provided comments at the three scoping 

meetings. The following is a summary of the comments that were provided during the scoping process. 

U.S. Department of the Interior, National Park Service (letter and email dated 

September 15, 2015) 

• The National Park Service (NPS) accepts the invitation to become a cooperating 

agency in developing the Supplemental EIS. General comments from the NPS 

emphasized NPS’s authority for managing the islands and surrounding waterbottoms, 

the designation of Horn and Petit Bois Islands as wilderness, and additional 

authorizations that the NPS has been given to protect and manage the Gulf Islands 

National Seashore (GUIS). 

• Comments from the NPS had three overarching recommendations: (1) develop an 

alternative that excludes lease sales within 15 mi (24 km) of the GUIS; (2) add an 

NPS consultation stipulation to alternatives that include lease sales within 15 mi 

(24 km) of the GUIS; and (3) undertake a robust environmental analysis that

acknowledges the scenic and wilderness character of the GUIS.

• The NPS also included six specific comments: (1) a request that the Supplemental 

EIS analyze the potential for subsidence at the barrier islands of the GUIS as a result 
Consultation and Coordination 5-5 

of oil and gas drilling; (2) an analysis of the direct and adverse effects to natural 

resources, including wildlife, of the GUIS from routine OCS oil- and gas-related 

operations; (3) an analysis of water quality and natural resource impacts from 

incidental oil or chemical spills and an offer to participate in the development of a 

spill prevention plan; (4) a request for more studies to be included in this 

Supplemental EIS, i.e., studies that quantify the potential adverse visual impacts to 

the GUIS, and an offer to develop standard lighting design feature requirements and 

conduct a visual impact analysis; (5) a request that this Supplemental EIS analyze the 

degradation of aesthetics and the wilderness character of Horn and Petit Bois Islands; 

and (6) a request that this Supplemental EIS include appropriate surveys and analysis 

of the potential impacts on any sensitive maritime archaeological resources in the 

project area.

Louisiana Department of Natural Resources, Office of Coastal Management (email dated

September 15, 2014) 

• The Louisiana Office of Coastal Management recommends that BOEM exert greater 

effort to quantify all secondary, indirect, and cumulative losses to their coastal zone 

from offshore energy development and a plan for compensatory mitigation. 

• The State of Louisiana supports exploration and development while acknowledging 

that the continued support of these activities is tied to the resiliency of the coast and 

coastal communities.

American Petroleum Institute (email dated September 15, 2015) 

• The API supports analysis of the environmental and socioeconomic impacts 

associated with development activities stemming from upcoming lease sales and the 

timely preparation of this Supplemental EIS.

• BOEM must focus EIS analyses on currently available new information and should 

not speculate on future results from ongoing studies.

• BOEM should also take into consideration the new safety and regulatory 

improvements since the Deepwater Horizon explosion, oil spill, and response as a 

part of the new information analyzed.

• The API suggests that this Supplemental EIS be designed specifically for use as a 

tiering document for future environmental reviews and that data from the bestavailable, peer-reviewed scientific literature should be the basis of environmental 

analyses, and not speculation.

General Public (comment via www.regulations.gov dated August 21, 2015) 

• The general public recommended that the proposed lease sale be cancelled because of 

concerns over pollution. 

Verbal Comments Received at the Scoping Meetings

• Operation Home Care raised concerns about the proposed lease sale due to potential 

future and ongoing human health and fisheries impacts, which the commenter tied to 

the Deepwater Horizon explosion, oil spill, and response. The commenter also raised 

concerns about Agency oversight, regulation, and monitoring of oil- and gas-related 

activities.

• The Acadian Group of the Sierra Club raised concerns about a series of issues, 

including pipeline safety in coastal Louisiana, potential pollution impacts from crew 
5-6 Central Planning Area Lease Sale 247 Supplemental EIS

and supply support-vessel discharges to coastal and offshore fisheries resources, the 

State/Federal revenue sharing for revenues generated on OCS lands, and the 

environmental impacts of produced waters and drilling wastes. In addition, the 

Acadian Group of the Sierra Club recommended that a monitoring system that 

incorporates the use of offshore buoys be installed to track oil movement in the event 

of future large offshore spills. 

5.3.3. Additional Scoping Opportunities

Although the scoping process is formally initiated by the publication of the NOI and Call, scoping 

efforts and other coordination meetings have proceeded and will continue to proceed throughout the 

NEPA processes. Scoping and coordination opportunities were also available during BOEM’s requests 

for information, comments, input, and review of its other NEPA documents, including the following: 

• scoping and comments on the 2012-2017 Five-Year Program EIS;

• scoping and comments on the 2012-2017 WPA/CPA Multisale EIS;

• scoping and comments on the WPA 233/CPA 231 Supplemental EIS; 

• scoping and comments on the CPA 235/241/247 Supplemental EIS; and 

• scoping and comments on the CPA 241/247 and EPA 226 Supplemental EIS.

5.3.4. Cooperating Agency

According to Part 516 of the DOI Departmental Manual, BOEM must invite eligible governmental 

entities to participate as cooperating agencies when developing an EIS in accordance with the 

requirements of NEPA and CEQ regulations. BOEM must also consider any requests by eligible 

government entities to participate as a cooperating agency with respect to a particular EIS, and then to 

either accept or deny such requests.

The NOI, which was published on August 17, 2015, included an invitation to other Federal agencies 

and State, Tribal, and local governments to consider becoming cooperating agencies in the preparation of 

this Supplemental EIS. In addition to this invitation, BOEM issued a letter to NPS inquiring if they 

would like to be a cooperating agency on this Supplemental EIS. This request was sent as a courtesy 

since NPS participated as a cooperating agency on the CPA 241/247 and EPA 226 Supplemental EIS. By 

their email and letter dated September 15, 2015, the NPS confirmed their interest to participate as a 

cooperating agency. 

BOEM has reviewed CEQ implementing regulations of NEPA specific to cooperating agencies. The 

CEQ regulation sets two criteria for which agencies may be cooperating agencies: 

(1) jurisdiction by law (40 CFR § 1508.15) – for example, agencies with the authority to 

grant permits for implementing the action; or

(2) special expertise (40 CFR § 1508.26) – cooperating agency status for specific 

purposes linked to special expertise requires more than an interest in a proposed 

action (Federal and non-Federal agencies may be requested [40 CFR §§ 1501.6 and

1508.5]). 

While the GUIS is not within the jurisdictional authority of BOEM, nor does NPS have jurisdictional 

authority for the OCS or OCS-related actions, NPS identified their special expertise regarding the 

resources and the values of the GUIS and the surrounding areas. The NPS indicated that their 

participation was to ensure that pertinent NPS mission statements, legislative authorities, and policies are 

duly considered when developing any alternatives related to management action or options that could 

potentially affect units of the NPS. BOEM has engaged in a deliberative process to evaluate this request 

and determine if the cooperating agency will provide additional analysis or data that BOEM does not 

already have.
Consultation and Coordination 5-7 

BOEM has entered into a Memorandum of Agreement (MOA) with NPS to establish expectations 

between the two agencies that apply for the duration of this Supplemental EIS, whereupon it terminates. 

This MOA outlines the responsibilities agreed to by BOEM and NPS for this Supplemental EIS project. 

A copy of the MOA is provided in Appendix A. BOEM provided NPS the opportunity to respond and 

provide any additional objective and analytical information to be included in the Draft Supplemental EIS.

5.4. DISTRIBUTION OF THE DRAFT SUPPLEMENTAL EIS FOR REVIEW AND 

COMMENT

BOEM sent copies of the Draft Supplemental EIS to the government, public, and private agencies and 

groups listed below. Local libraries along the Gulf Coast were provided copies of this Supplemental EIS; 

a list of these libraries is available on BOEM’s Internet 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

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 
5-8 Central Planning Area Lease Sale 247 Supplemental EIS

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

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. 
Consultation and Coordination 5-9 

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 

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
5-10 Central Planning Area Lease Sale 247 Supplemental EIS

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

5.5. COASTAL ZONE MANAGEMENT ACT

If a Federal agency’s activities or development projects within or outside of the coastal zone will have 

reasonably foreseeable coastal effects in the coastal zone, then the activity is subject to a Federal 

Consistency Determination (CD). A consistency review will be performed pursuant to the Coastal Zone 

Management Act (CZMA), and CDs will be prepared for each CZMA State prior to the proposed lease 

sale. To prepare the CDs, BOEM reviews each CZMA State’s Coastal Management Plan and analyzes 

the potential impacts as outlined in this Supplemental EIS, new information, and applicable studies as 

they pertain to the enforceable policies of each Coastal Management Program (CMP). The CZMA 

requires that Federal actions that are reasonably likely to affect any land or water use or natural resource 

of the coastal zone be “consistent to the maximum extent practicable” with relevant enforceable policies 

of the State’s federally approved coastal management program (15 CFR part 930 subpart C). 

Based on these and other analyses, BOEM’s Gulf of Mexico OCS Region’s Regional Director makes 

an assessment of consistency, which is then sent to the CZMA States of Texas and Louisiana for 

proposed WPA lease sales or to Louisiana, Mississippi, Alabama, and Florida for proposed CPA and/or 

EPA lease sales. If a CZMA State concurs, BOEM can proceed with the proposed lease sale. A CZMA 

State’s concurrence may be presumed when a CZMA State does not provide a response within the 60-day 

review period. A CZMA State may request an extension of time to review the CD within the 60-day 

period, which the Federal agency shall approve for an extension of 15 days or less. If a CZMA State 

objects, it must do the following under the CZMA: 

(1) indicate how BOEM’s prelease proposal is inconsistent with the State’s CMP and 

suggest alternative measures to bring BOEM’s proposal into consistency with the 

State’s CMP; or 

(2) describe the need for additional information that would allow a determination of 

consistency. In the event of an objection, the Federal and State agencies should use 

the remaining portion of the 90-day review period to attempt to resolve their 

differences (15 CFR § 930.43(b)). 

At the end of the 90-day review period, the Federal agency shall not proceed with the activity over a 

CZMA State agency’s objection unless the Federal agency concludes that, under the “consistent to the 

maximum extent practicable” standard described in 15 CFR § 930.32, consistency with the enforceable 

policies of the CMP is prohibited by existing law applicable to the Federal agency and the Federal agency

has clearly described, in writing, to the State agency the legal impediments to full consistency; or, the 

Federal agency has concluded that its proposed action is fully consistent with the enforceable policies of 

the CMP, though the CZMA State agency objects. Unlike the consistency process for specific OCS plans 

and permits, there is no procedure for administrative appeal to the Secretary of Commerce for a Federal 
Consultation and Coordination 5-11

CD for prelease activities. In the event that there is a serious disagreement between BOEM and a CZMA 

State, either agency may request mediation. Mediation is voluntary, and the Secretary of Commerce 

would serve as the mediator. Whether there is mediation or not, the final CD is made by DOI, and it is 

the final administrative action for the prelease consistency process. Each Gulf State’s CMP is described 

in Appendix F of the 2012-2017 WPA/CPA Multisale EIS. 

5.6. ENDANGERED SPECIES ACT

The Endangered Species Act of 1973 (16 U.S.C. §§ 1531 et seq.), as amended, establishes a national 

policy designed to protect and conserve threatened and endangered species and the ecosystems upon 

which they depend. BOEM and BSEE are currently in consultation with NMFS and FWS regarding the 

OCS oil and gas program in the Gulf of Mexico. BOEM is acting as the lead agency in the ongoing 

consultation, with BSEE’s assistance and involvement. The programmatic consultation was expanded in 

scope after the reinitiation of consultation by BOEM following the Deepwater Horizon explosion and oil 

spill, and it will include both existing and future OCS oil and gas leases in the Gulf of Mexico over a 

10-year period. This consultation also considers any changes in baseline environmental conditions 

following the Deepwater Horizon explosion, oil spill, and response. The programmatic consultation will 

also include postlease activities associated with OCS oil- and gas-related activities in the Gulf of Mexico, 

including G&G and decommissioning activities. While the programmatic Biological Opinion is in 

development, BOEM and NMFS have agreed to interim consultations on postlease approvals. 

With consultation ongoing, BOEM and BSEE will continue to comply with all reasonable and 

prudent measures and the terms and conditions under the existing consultations, along with implementing 

the current BOEM- and BSEE-required mitigation, monitoring, and reporting requirements. Based on the 

most recent and best available information at the time, BOEM and BSEE will also continue to closely 

evaluate and assess risks to listed species and designated critical habitat in upcoming environmental 

compliance documentation under NEPA and other statutes.

5.7. MAGNUSON-STEVENS FISHERY CONSERVATION AND MANAGEMENT ACT

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 oiland gas-related activities authorized by BOEM may result in adverse effects to EFH, and therefore, 

require EFH consultation. 

Following the Deepwater Horizon explosion, oil spill, and response, NMFS requested a 

comprehensive review of the existing EFH consultation in a response letter dated September 24, 2010. In 

light of this request, Regional staff of BOEM and NMFS agreed on procedures that would incorporate a 

new programmatic EFH consultation into each prepared Five-Year Program EIS and that began with the 

2012-2017 Five-Year Program. BOEM has EFH Assessments for all planning areas in the GOM 

(Appendix D of the 2012-2017 WPA/CPA Multisale EIS and EPA 225/226 EIS) that describe the OCS 

proposed activities, analyzes the effects of the proposed activities on EFH, and identifies the proposed 

mitigating measures. The programmatic EFH consultation, which covers proposed CPA Lease Sale 247, 

was initiated with the distribution and review of the 2012-2017 WPA/CPA Multisale EIS and with the 

subsequent written communications between BOEM and the NMFS. These documents formalized the 

conservation recommendations put forth by NMFS and by BOEM’s acceptance and response to these 

recommendations. 

While the necessary components of the EFH consultation are complete (as per BOEM’s June 8, 2012, 

response letter to NMFS), there is ongoing coordination among NMFS, BOEM, and BSEE. This 

coordination includes annual reports from BOEM to NMFS, meetings with Regional staff, and 

discussions of mitigation and relevant topics. All agencies will continue to communicate for the duration 

of the Five-Year Program.
5-12 Central Planning Area Lease Sale 247 Supplemental EIS

5.8. NATIONAL HISTORIC PRESERVATION ACT

In accordance with the National Historic Preservation Act (54 U.S.C. §§ 300101 et seq.), Federal 

agencies are required to consider the effect of their undertakings on historic properties. The 

implementing regulations for Section 106 of the National Historic Preservation Act (54 U.S.C. §§ 300101 

et seq.), issued by the Advisory Council on Historic Preservation (36 CFR part 800), specify the required 

review process. Because of the extensive geographic area analyzed in this Supplemental EIS and because 

there will be no adverse effects to historic properties as a result of the proposed CPA lease sale, BOEM 

will complete its Section 106 review process once BOEM has performed the necessary site-specific 

analysis of postlease permitted or approved activities. Additional consultations with the Advisory 

Council on Historic Places, State historic preservation offices, federally recognized Indian Tribes, and 

other consulting parties may take place at that time, if appropriate. Refer to Chapter 4.1.1.22 for more 

information on this review process.

As an early planning effort, BOEM initiated a request for comment on the NOI for proposed CPA 

Lease Sale 247 via formal letters on August 17, 2015. Those letters were addressed to each of the 

affected Gulf Coast States (i.e., Louisiana, Mississippi, Alabama, and Florida). A 30-day comment 

period was provided and no responses were received. A separate letter initiating a request to determine 

interest in participation for the Supplemental EIS was sent to the federally recognized Indian Tribes, 

including the Alabama-Coushatta Tribe of Texas, Caddo Nation of Oklahoma, Chitimacha Tribe of 

Louisiana, Choctaw Nation of Oklahoma, Coushatta Tribe of Louisiana, Jena Band of Choctaw Indians, 

Miccosukee Tribe of Indians of Florida, Mississippi Band of Choctaw Indians, Poarch Band of Creek 

Indians, Seminole Tribe of Florida, Seminole Nation of Oklahoma, and Tunica-Biloxi Indian Tribe of 

Louisiana. Federally recognized Tribes are not bound by public comment deadlines, and their input will 

be considered throughout the development process of this Supplemental EIS. 

BOEM will also continue to impose mitigating measures and monitoring and reporting requirements 

to ensure that historic properties are not affected by the proposed undertakings. BOEM will reinitiate the 

consultation process with the affected parties should such circumstances warrant further consultation.

In 1977, the Historic Preservation Fund (54 U.S.C. §§ 303101-303103) was established to assist State 

and Tribal Historic Preservation Officers in their efforts to protect and preserve historic properties as set 

forth in the requirements of the National Historic Preservation Act. The Historic Preservation Fund is 

authorized at $150 million per year and is fully funded from OCS oil and gas revenues payable to the 

United States under Section 9 of the Outer Continental Shelf Lands Act (43 U.S.C. § 1338). However, 

these funds are available for expenditure only when appropriated by Congress, which has never fully 

appropriated the available funds. Since its inception, approximately $3.3 billion of the Historic 

Preservation Fund remains unappropriated (National Conference of State Historic Preservation Officers,

2015). 

The Historic Preservation Fund may be used directly by State Historic Preservation Officers/Tribal 

Historic Preservation Officers or passed on as subgrants and contracts to public and private agencies, 

nonprofit organizations, educational institutions, and individuals. Eligible preservation projects include 

historic properties’ survey and inventory, National Register of Historic Places’ nominations, preservation 

education, architectural planning, historic structure reports, community preservation planning, and brick 

and mortar repairs to buildings (USDOI, NPS, 2014). These historic preservation programs can further 

catalyze community and neighborhood revitalization, job creation, and economic development, primarily 

through heritage tourism and the rehabilitation of historic properties through the Historic Tax Credit, 

which is administered by the State Historic Preservation Officers. Since the Historic Preservation Fund

was implemented in 1977, the Historic Tax Credit program has rehabilitated nearly 39,000 buildings

nationwide, has created 2.4 million jobs, has created 140,000 low- and moderate-income housing units, 

and has leveraged $109 billion in non-Federal investment (National Conference of State Historic 

Preservation Officers, 2014; USDOI, NPS, 2014). In Fiscal Year 2015, Congress allocated a total of 

$56.41 million from the Historic Preservation Fund, of which $46.925 million was awarded to State 

Historic Preservation Officers and $8.985 million was awarded to Tribal Historic Preservation Officers. 

An additional $500,000 was awarded for projects that will increase diversity in the National Register of 

Historic Places and the National Historic Landmarks programs (National Conference of State Historic 

Preservation Officers, 2015). 
Consultation and Coordination 5-13

5.9. GOVERNMENT-TO-GOVERNMENT

In accordance with Executive Order 13175, “Consultation and Coordination with Indian Tribal 

Governments,” Federal agencies are required to establish regular and meaningful consultation and 

collaboration with Tribal officials in the development of Federal policies that have Tribal implications, to 

strengthen the United States’ government-to-government relationships with Indian Tribes, and to reduce 

the imposition of unfunded mandates upon Indian Tribes. BOEM initiated a request to determine interest 

in participation for this Supplemental EIS via a formal letter. That letter was addressed to each of the 

federally recognized Indian Tribes having Gulf Coast affiliation, including the Alabama-Coushatta Tribe 

of Texas, Caddo Nation of Oklahoma, Chitimacha Tribe of Louisiana, Choctaw Nation of Oklahoma, 

Coushatta Tribe of Louisiana, Jena Band of Choctaw Indians, Miccosukee Tribe of Indians of Florida, 

Mississippi Band of Choctaw Indians, Poarch Band of Creek Indians, Seminole Tribe of Florida, 

Seminole Nation of Oklahoma, and Tunica-Biloxi Indian Tribe of Louisiana. 

CHAPTER 6 

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Wannamaker, C.M. and J.A. Rice. 2000. Effects of hypoxia on movements and behavior of selected 

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CHAPTER 7 

PREPARERS

Preparers 7-3 

7. PREPARERS

Gary D. Goeke, Chief, Environmental Assessment Section

Lissa Lyncker, Unit Supervisor, Environmental Protection Specialist 

Tershara Matthews, NEPA Co-Coordinator, Unit Supervisor, Environmental Protection Specialist 

Beth Nord, NEPA Coordinator, Environmental Scientist 

Poojan Tripathi, Headquarters’ Coordinator, Environmental Specialist 

Robert Arpino, Physical Scientist

Bruce Baird, Marine Biologist 

Mark Belter, Marine Biologist

Idrissa Boube, Environmental Scientist 

Darice K. Breeding, Environmental Protection Specialist 

Brian Cameron, Jr., Environmental Scientist 

Sindey Chaky, Environmental Protection Specialist

Leonard Coats, Supervisor, Geographer 

Kasey Couture, Program Analyst

Thierry DeCort, Chief, Geological and Geophysical Section 

Ross Del Rio, Environmental Scientist 

Chris DuFore, Oceanographer

Stephanie Gambino, Chief, Biological Sciences Section 

Donald (Tre) W. Glenn III, Protected Species Biologist 

Stephen Gonzales, Geographer 

Mike Gravois, Geographer 

Allison Hernandez, Protected Species Biologist 

Chin (Chester) Hua Huang, Meteorologist 

Nicole Hughes, Protected Species Biologist

Jack Irion, Unit Supervisor, Marine Archaeologist 

Mark Jensen, Economist 

Matthew Johnson, Marine Biologist

Doug Jones, Senior Marine Archaeologist

Agatha-Marie Kaller, Unit Supervisor, Marine Biologist 

Ariel Kay, Environmental Scientist

Paula (Kaye) London, Protected Species Biologist 

Harry Luton, Lead Social Scientist

Charles (Jay) McCreery, Physical Scientist

Margaret Metcalf, Chief, Physical/Chemical Sciences Section

Deborah H. Miller, Technical Editor

David P. Moran, Biologist 

Mark Mueller, Marine Ecologist

S. Erin O’Reilly, Physical Scientist

Trevis Olivier, Environmental Scientist

Christopher Oos, Geographer

Catherine A. Rosa, Environmental Assessment Program Specialist

Scott Sorset, Marine Archaeologist 

Shane Stradley, Geographer 

Toby Wraye, Information Management Specialist

CHAPTER 8 

GLOSSARY

Glossary 8-3 

8. GLOSSARY 

Acute—Sudden, short term, severe, critical, 

crucial, intense, but usually of short duration. 

Anaerobic—Capable of growing in the absence of 

molecular oxygen. 

Annular preventer—A component of the 

pressure control system in the BOP that forms 

a seal in the annular space around any object 

in the wellbore or upon itself, enabling well 

control operations to commence.

Anthropogenic—Coming from human sources, 

relating to the effect of humankind on nature. 

API gravity—A standard adopted by the 

American Petroleum Institute for expressing 

the specific weight of oil.

Aromatic—Class of organic compounds 

containing benzene rings or benzenoid 

structures.

Attainment area—An area that is shown by 

monitored data or by air-quality modeling 

calculations to be in compliance with primary 

and secondary ambient air quality standards 

established by USEPA. 

Barrel (bbl)—A volumetric unit used in the 

petroleum industry; equivalent to 42 U.S. 

gallons or 158.99 liters. 

Benthic—On or in the bottom of the sea. 

Biological Opinion—The FWS or NMFS 

evaluation of the impact of a proposed action 

on endangered and threatened species, in 

response to formal consultation under 

Section 7 of the Endangered Species Act.

Block—A geographical area portrayed on official 

BOEM protraction diagrams or leasing maps 

that contains approximately 2,331 ha (9 mi2

).

Blowout—An uncontrolled flow of fluids below 

the mudline from appurtenances on a wellhead 

or from a wellbore.

Blowout preventer (BOP)—One of several 

valves installed at the wellhead to prevent the 

escape of pressure either in the annular space 

between the casing and drill pipe or in open 

hole (i.e., hole with no drill pipe) during 

drilling completion operations. Blowout 

preventers on jackup or platform rigs are 

located at the water’s surface; on floating 

offshore rigs, BOP’s are located on the 

seafloor.

Bottom kill—A wild well-control procedure 

involving the intersection of an uncontrolled 

well with a relief well for the purpose of 

pumping heavy mud or cement into the wild 

well to stanch the flow of oil or gas (the wellcontrol strategy for the Macondo spill 

deployed in mid-July 2010 that resulted in the 

successful capping of the well). 

Cetacean—Aquatic mammal of the order Cetacea, 

such as whales, dolphins, and porpoises. 

Chemosynthetic—Organisms that obtain their 

energy from the oxidation of various inorganic 

compounds rather than from light 

(photosynthetic). 

Coastal waters—Waters within the geographical 

areas defined by each State’s Coastal Zone 

Management Program.

Coastal wetlands—forested and nonforested 

habitats, mangroves, and marsh islands 

exposed to tidal activity. These areas directly 

contribute to the high biological productivity 

of coastal waters by input of detritus and 

nutrients, by providing nursery and feeding 

areas for shellfish and finfish, and by serving 

as habitat for birds and other animals.

Coastal zone—The coastal waters (including the 

lands therein and thereunder) and the adjacent 

shorelands (including the waters therein and 

thereunder) strongly influenced by each other 

and in proximity to the shorelines of several 

coastal states; the zone includes islands, 

transitional and intertidal areas, salt marshes, 

wetlands, and beaches, and it extends seaward 

to the outer limit of the United States 

territorial sea. The zone extends inland from 

the shorelines only to the extent necessary to 

control shorelands, the uses of which have a 

direct and significant impact on the coastal 

waters. Excluded from the coastal zone are 

lands the use of which is by law subject to the 

discretion of or which is held in trust by the 

Federal Government, its officers, or agents

(also refer to State coastal zone boundaries). 

Completion—Conversion of a development well 

or an exploration well into a production well.

Condensate—Liquid hydrocarbons produced with 

natural gas; they are separated from the gas by 

cooling and various other means. Condensates 

generally have an API gravity of 50o

-120o. 
8-4 Central Planning Area Lease Sale 247 Supplemental EIS

Continental margin—The ocean floor that lies 

between the shoreline and the abyssal ocean 

floor, includes the continental shelf, 

continental slope, and continental rise.

Continental shelf—General term used by 

geologists to refer to the continental margin 

province that lies between the shoreline and 

the abrupt change in slope called the shelf 

edge, which generally occurs in the Gulf of 

Mexico at about the 200-m (656-ft) water 

depth. The continental shelf is characterized 

by a gentle slope (about 0.1o

). This is 

different from the juridical term used in 

Article 76 of the United Nations Convention

on the Law of the Sea Royalty Payment (refer 

to the definition of Outer Continental Shelf). 

Continental slope—The continental margin 

province that lies between the continental 

shelf and continental rise, characterized by a 

steep slope (about 3o

-6o).

Critical habitat—Specific areas essential to the 

conservation of a protected species and that 

may require special management 

considerations or protection. 

Crude oil—Petroleum in its natural state as it 

emerges from a well or after it passes through 

a gas-oil separator, but before refining or 

distillation. An oily, flammable, bituminous 

liquid that is essentially a complex mixture of 

hydrocarbons of different types with small 

amounts of other substances. 

Delineation well—A well that is drilled for the 

purpose of determining the size and/or volume 

of an oil or gas reservoir.

Demersal—Living at or near the bottom of the 

sea.

Development—Activities that take place 

following discovery of economically 

recoverable mineral resources, including 

geophysical surveying, drilling, platform 

construction, operation of onshore support 

facilities, and other activities that are for the 

purpose of ultimately producing the resources. 

Development and Production Plan (DPP)—A 

document that must be prepared by the 

operator and submitted to BOEM for approval 

before any development and production 

activities are conducted on a lease or unit in 

any OCS area other than the western Gulf of 

Mexico.

Development Operations Coordination 

Document (DOCD)—A document that must 

be prepared by the operator and submitted to 

BOEM for approval before any development 

or production activities are conducted on a 

lease in the western Gulf of Mexico.

Development well—A well drilled to a known 

producing formation to extract oil or gas; a 

production well; distinguished from a wildcat 

or exploration well and from an offset well. 

Direct employment—Consists of those workers 

involved in the primary industries of oil and 

gas exploration, development, and production 

operations (Standard Industrial Classification 

Code 13—Oil and Gas Extraction). 

Discharge—Something that is emitted; flow rate 

of a fluid at a given instant expressed as 

volume per unit of time. 

Dispersant—A suite of chemicals and solvents 

used to break up an oil slick into small 

droplets, which increases the surface area of 

the oil and hastens the processes of weathering 

and microbial degradation. 

Dispersion—A suspension of finely divided 

particles in a medium. 

Drilling mud—A mixture of clay, water or 

refined oil, and chemical additives pumped 

continuously downhole through the drill pipe 

and drill bit, and back up the annulus between 

the pipe and the walls of the borehole to a 

surface pit or tank. The mud lubricates and 

cools the drill bit, lubricates the drill pipe as it 

turns in the wellbore, carries rock cuttings to 

the surface, serves to keep the hole from 

crumbling or collapsing, and provides the 

weight or hydrostatic head to prevent 

extraneous fluids from entering the well bore 

and to downhole pressures; also called drilling 

fluid.

Economically recoverable resources—An 

assessment of hydrocarbon potential that takes 

into account the physical and technological 

constraints on production and the influence of 

costs of exploration and development and 

market price on industry investment in OCS 

exploration and production. 

Effluent—The liquid waste of sewage and 

industrial processing. 

Effluent limitations—Any restriction established 

by a State or the USEPA on quantities, rates, 

and concentrations of chemical, physical, 
Glossary 8-5 

biological, and other constituents discharged 

from point sources into U.S. waters, including 

schedules of compliance.

Epifaunal—Animals living on the surface of hard 

substrate.

Essential habitat—Specific areas crucial to the 

conservation of a species and that may 

necessitate special considerations. 

Estuary—Coastal semienclosed body of water 

that has a free connection with the open sea 

and where freshwater meets and mixes with 

seawater.

Eutrophication—Enrichment of nutrients in the 

water column by natural or artificial methods 

accompanied by an increase of respiration, 

which may create an oxygen deficiency.

Exclusive Economic Zone (EEZ)—The maritime 

region extending 200 nmi (230 mi; 370 km)

from the baseline of the territorial sea, in 

which the United States has exclusive rights 

and jurisdiction over living and nonliving 

natural resources.

Exploration Plan (EP)—A plan that must be 

prepared by the operator and submitted to 

BOEM for approval before any exploration or 

delineation drilling is conducted on a lease. 

Exploration well—A well drilled in unproven or 

semi-proven territory to determining whether 

economic quantities of oil or natural gas 

deposit are present.

False crawls—Refers to when a female sea turtle 

crawls up on the beach to nest (perhaps) but 

does not and returns to the sea without laying 

eggs.

Field—An accumulation, pool, or group of pools 

of hydrocarbons in the subsurface. A 

hydrocarbon field consists of a reservoir in a 

shape that will trap hydrocarbons and that is 

covered by an impermeable, sealing rock.

Floating production, storage, and offloading 

(FPSO) system—A tank vessel used as a 

production and storage base; produced oil is 

stored in the hull and periodically offloaded to 

a shuttle tanker for transport to shore.

Gathering lines—A pipeline system used to bring 

oil or gas production from a number of 

separate wells or production facilities to a 

central trunk pipeline, storage facility, or 

processing terminal. 

Geochemical—Of or relating to the science 

dealing with the chemical composition of and 

the actual or possible chemical changes in the 

crust of the earth.

Geophysical survey—A method of exploration in 

which geophysical properties and relationships 

are measured remotely by one or more 

geophysical methods.

Habitat—A specific type of environment that is 

occupied by an organism, a population, or a 

community. 

Hermatypic coral—Reef-building corals that 

produce hard, calcium carbonate skeletons and 

that possess symbiotic, unicellular algae 

within their tissues.

Harassment—An intentional or negligent act or 

omission that creates the likelihood of injury 

to wildlife by annoying it to such an extent as 

to significantly disrupt normal behavior 

patterns that include, but are not limited to, 

feeding or sheltering.

Hydrocarbons—Any of a large class of organic 

compounds containing primarily carbon and 

hydrogen. Hydrocarbon compounds are 

divided into two broad classes: aromatic and 

aliphatics. They occur primarily in petroleum, 

natural gas, coal, and bitumens. 

Hypoxia—Depressed levels of dissolved oxygen 

in water, usually resulting in decreased 

metabolism.

Incidental take—Takings that result from, but are 

not the purpose of, carrying out an otherwise 

lawful activity (e.g., fishing) conducted by a 

Federal agency or applicant (refer to Taking).

Indirect employment—Secondary or supporting 

oil- and gas-related industries, such as the 

processing of crude oil and gas in refineries, 

natural gas plants, and petrochemical plants. 

Induced employment—Tertiary industries that 

are created or supported by the expenditures of 

employees in the primary or secondary 

industries (direct and indirect employment), 

including consumer goods and services such 

as food, clothing, housing, and entertainment. 

Infrastructure—The facilities associated with oil 

and gas development, e.g., refineries, gas 

processing plants, etc.

Jack-up rig—A barge-like, floating platform with 

legs at each corner that can be lowered to the 
8-6 Central Planning Area Lease Sale 247 Supplemental EIS

sea bottom to raise the platform above the 

water.

Kick—A deviation or imbalance, typically sudden 

or unexpected, between the downward 

pressure exerted by the drilling fluid and the 

upward pressure of in-situ formation fluids or 

gases.

Landfall—The site where a marine pipeline 

comes to shore.

Lease—Authorization that is issued under 

Section 8 or maintained under Section 6 of the 

Outer Continental Shelf Lands Act and that 

authorizes exploration for, and development 

and production of, minerals. 

Lease sale—The competitive auction of leases 

granting companies or individuals the right to 

explore for and develop certain minerals under 

specified conditions and periods of time.

Lease term—The initial period for oil and gas 

leases, usually a period of 5, 8, or 10 years 

depending on water depth or potentially 

adverse conditions. 

Lessee—A party authorized by a lease, or an 

approved assignment thereof, to explore for 

and develop and produce the leased deposits in 

accordance with regulations at 30 CFR part 

250 and 30 CFR part 550. 

Lower marine riser package—The head 

assembly of a subsurface well at the point 

where the riser connects to a blowout 

preventer.

Macondo—Prospect name given by BP to the 

Mississippi Canyon Block 252 exploration 

well that the Deepwater Horizon rig was 

drilling when a blowout occurred on April 20, 

2010.

Macondo spill—The name given to the oil spill 

that resulted from the explosion and sinking of 

the Deepwater Horizon rig from the period 

between April 24, 2010, when search and 

recovery vessels on site reported oil at the sea 

surface, and September 19, 2010, when the 

uncontrolled flow from the Macondo well was 

capped. 

Marshes—Persistent, emergent, nonforested 

wetlands characterized by predominantly 

cordgrasses, rushes, and cattails.

Military warning area—An area established by 

the U.S. Department of Defense within which 

military activities take place.

Minerals—As used in this document, minerals 

include oil, gas, sulphur, and associated 

resources, and all other minerals authorized by 

an Act of Congress to be produced from 

public lands as defined in Section 103 of the 

Federal Land Policy and Management Act of 

1976. 

Naturally occurring radioactive materials 

(NORM)—naturally occurring material that 

emits low levels of radioactivity, originating 

from processes not associated with the 

recovery of radioactive material. The 

radionuclides of concern in NORM are 

Radium-226, Radium-228, and other isotopes 

in the radioactive decay chains of uranium and 

thorium. 

Nepheloid—A layer of water near the bottom that 

contains significant amounts of suspended 

sediment.

Nonattainment area—An area that is shown by 

monitoring data or by air-quality modeling 

calculations to exceed primary or secondary 

ambient air quality standards established by 

USEPA.

Nonhazardous oil-field wastes (NOW)—Wastes 

generated by exploration, development, or 

production of crude oil or natural gas that are 

exempt from hazardous waste regulation under 

the Resource Conservation and Recovery Act 

(Regulatory Determination for Oil and Gas 

and Geothermal Exploration, Development 

and Production Wastes, dated June 29, 1988, 

53 FR 25446; July 6, 1988). These wastes 

may contain hazardous substances.

Offloading—Unloading liquid cargo, crude oil, or 

refined petroleum products. 

Operational discharge—Any incidental 

pumping, pouring, emitting, emptying, or 

dumping of wastes generated during routine 

offshore drilling and production activities. 

Operator—An individual, partnership, firm, or 

corporation having control or management of 

operations on a leased area or portion thereof. 

The operator may be a lessee, designated 

agent of the lessee, or holder of operating 

rights under an approved operating agreement.

Organic matter—Material derived from living 

plants or animals.

Outer Continental Shelf (OCS)—All submerged 

lands that comprise the continental margin 
Glossary 8-7 

adjacent to the United States and seaward of 

State offshore lands.

Pelagic—Of or pertaining to the open sea; 

associated with open water beyond the direct 

influence of coastal systems.

Plankton—Passively floating or weakly motile 

aquatic plants (phytoplankton) and animals 

(zooplankton). 

Platform—A steel or concrete structure from 

which offshore development wells are drilled.

Play—A prospective subsurface area for 

hydrocarbon accumulation that is 

characterized by a particular structural style or 

depositional relationship. 

Primary production—Organic material produced 

by photosynthetic or chemosynthetic 

organisms.

Produced water—Total water discharged from 

the oil and gas extraction process; production 

water or production brine. 

Production—Activities that take place after the 

successful completion of any means for the 

extraction of resources, including bringing the 

resource to the surface, transferring the 

produced resource to shore, monitoring 

operations, and drilling additional wells or 

workovers.

Province—A spatial entity with common geologic 

attributes. A province may include a single 

dominant structural element such as a basin or 

a fold belt, or a number of contiguous related 

elements.

Ram—The main component of a blowout 

preventer designed to shear casing and tools in 

a wellbore or to seal an empty wellbore. A 

blind shear ram accomplishes the former and a 

blind ram the latter.

Recoverable reserves—The portion of the 

identified hydrocarbon or mineral resource 

that can be economically extracted under 

current technological constraints.

Recoverable resource estimate—An assessment 

of hydrocarbon or mineral resources that takes 

into account the fact that physical and 

technological constraints dictate that only a 

portion of resources can be brought to the 

surface.

Recreational beaches—Frequently visited, sandy 

areas along the Gulf of Mexico shorefront that 

support multiple recreational activities at the 

land-water interface. Included are National 

Seashores, State Park and Recreational Areas, 

county and local parks, urban beachfronts, and 

private resorts.

Refining—Fractional distillation of petroleum, 

usually followed by other processing (e.g., 

cracking).

Relief—The difference in elevation between the 

high and low points of a surface. 

Reserves—Proved oil or gas resources.

Rig—A structure used for drilling an oil or gas 

well.

Riser insertion tube tool—A “straw” and gasket 

assembly improvised during the Macondo spill 

response that was designed to siphon oil and 

gas from the broken riser of the Deepwater 

Horizon rig lying on the sea bottom (an early 

recovery strategy for the Macondo spill in 

May 2010). 

Royalty—A share of the minerals produced from 

a lease paid in either money or “in-kind” to the 

landowner by the lessee.

Saltwater intrusion—Saltwater invading a body 

of freshwater.

Sciaenids—Fishes belonging to the croaker family 

(Sciaenidae).

Seagrass beds—More or less continuous mats of 

submerged, rooted, marine, flowering vascular 

plants occurring in shallow tropical and 

temperate waters. Seagrass beds provide 

habitat, including breeding and feeding 

grounds, for adults and/or juveniles of many 

of the economically important shellfish and 

finfish.

Sediment—Material that has been transported and 

deposited by water, wind, glacier, 

precipitation, or gravity; a mass of deposited 

material.

Seeps (hydrocarbon)—Gas or oil that reaches the 

surface along bedding planes, fractures, 

unconformities, or fault planes. 

Sensitive area—An area containing species, 

populations, communities, or assemblages of 

living resources, that is susceptible to damage 

from normal OCS oil- and gas-related 

activities. Damage includes interference with 

established ecological relationships.

Shear ram—The component in a BOP that cuts, 

or shears, through the drill pipe and forms a 
8-8 Central Planning Area Lease Sale 247 Supplemental EIS

seal against well pressure. Shear rams are 

used in floating offshore drilling operations to 

provide a quick method of moving the rig 

away from the hole when there is no time to 

trip the drill stem out of the hole.

Shoreline Cleanup and Assessment Team—The 

on-the-scene responders for post-spill 

shoreline protection who established priorities, 

standardized procedures, and terminology. 

Spill of National Significance—Designation by 

the USEPA Administrator under 40 CFR § 

300.323 for discharges occurring in the inland 

zone and the Commandant of the U.S. Coast 

Guard for discharges occurring in the coastal 

zone, authorizing the appointment of a 

National Incident Commander for spillresponse activity.

State coastal zone boundary—The State coastal 

zone boundaries for each CZMA-affected 

State are defined at http://

coastalmanagement.noaa.gov/mystate/docs/

StateCZBoundaries.pdf. 

Structure—Any OCS facility that extends from 

the seafloor to above the waterline; in 

petroleum geology, any arrangement of rocks 

that may hold an accumulation of oil or gas. 

Subarea—A discrete analysis area.

Subsea isolation device—An emergency 

disconnection and reconnection assembly for 

the riser at the seafloor. 

Supply vessel—A boat that ferries food, water, 

fuel, and drilling supplies and equipment to an 

offshore rig or platform and returns to land 

with refuse that cannot be disposed of at sea.

Taking—To harass, harm, pursue, hunt, shoot, 

wound, kill, trap, capture, or collect any 

endangered or threatened species, or to 

attempt to engage in any such conduct 

(including actions that induce stress, adversely 

impact critical habitat, or result in adverse 

secondary or cumulative impacts). 

Harassments are the most common form of 

taking associated with OCS Program 

activities.

Tension-leg platform (TLP)—A production 

structure that consists of a buoyant platform 

tethered to concrete pilings on the seafloor 

with flexible cable.

Total dissolved solids—The total amount of 

solids that are dissolved in water.

Total suspended particulate matter—The total 

amount of suspended solids in water. 

Total suspended solids—The total amount of 

suspended solids in water. 

Trunkline—A large-diameter pipeline receiving 

oil or gas from many smaller tributary 

gathering lines that serve a large area; 

common-carrier line; main line.

Turbidity—Reduced water clarity due to the 

presence of suspended matter. 

Volatile organic compound (VOC)—Any 

organic compound that is emitted to the 

atmosphere as a vapor.

Water test areas—Areas within the eastern Gulf 

where U.S. Department of Defense research, 

development, and testing of military planes, 

ships, and weaponry take place.

Weathering (of oil)—The aging of oil due to its 

exposure to the atmosphere, causing marked 

alterations in its physical and chemical 

makeup. 
FIGURES

Figures Figures-3

Figure 1-1. Gulf of Mexico Planning Areas, Proposed CPA Lease Sale Area, and Locations of Major Cities.
Figures-4 Central Planning Area Lease Sale 247 Supplemental EIS

Figure 2-1. Location of Proposed Stipulations and Deferrals.
Figures Figures-5

Figure 2-2. Military Warning Areas and Eglin Water Test Areas in the Gulf of Mexico.
Figures-6 Central Planning Area Lease Sale 247 Supplemental EIS

Figure 3-1. Offshore Subareas in the Gulf of Mexico.
Figures Figures-7 

Figure 4-1. Distribution of Bottom-Water Dissolved Oxygen from July 28 to August 3, West of the Mississippi 

River Delta (black-lined areas, i.e., the areas in red to deep red, have very little dissolved oxygen) 

(USDOC, NOAA, 2015). 

Figure 4-2. OCS Leasing Activity Near the Gulf Islands National Seashore.
Figures-8 Central Planning Area Lease Sale 247 Supplemental EIS

Figure 4-3. Photograph of Remaining OCS Structures taken from Petit Bois Island Looking South (modified and 

reprinted with permission from Marsh, 2014). (Petit Bois Island is within the Gulf Islands National 

Seashore and is a National Park Service-designated wilderness area.)
Figures Figures-9 

Figure 4-4. Federal OCS Lease Blocks Subject to the Gulf Islands National Seashore Information to Lessees. 
Figures-10 Central Planning Area Lease Sale 247 Supplemental EIS

Figure 4-5. Economic Impact Areas in the Gulf of Mexico.
Figures Figures-11

Reference

U.S. Dept. of Commerce. National Oceanic and Atmospheric Administration. 2015. 2015 Gulf of 

Mexico dead zone ‘above average’: Heavy June rains, high July nutrient runoff levels likely cause 

for increased size. Internet website: http://www.noaanews.noaa.gov/stories2015/080415-gulf-ofmexico-dead-zone-above-average.html. Posted August 4, 2015. Accessed October 8, 2015. 

TABLES

Tables Tables-3 

Table 3-1

Projected Oil and Gas in the Gulf of Mexico OCS

Typical Lease Sale OCS Cumulative

(2012-2051)

Western Planning Area

 Reserve/Resource Production

 Oil (BBO) 0.116-0.200 2.510-3.696

 Gas (Tcf) 0.538-0.938 12.539-18.434

Central Planning Area

 Reserve/Resource Production

 Oil (BBO) 0.460-0.894 15.825-21.733

 Gas (Tcf) 1.939-3.903 63.347-92.691

Eastern Planning Area

 Reserve/Resource Production

 Oil (BBO) 0-0.071 0-0.211

 Gas (Tcf) 0-0.162 0.502

BBO = billion barrels of oil

Tcf = trillion cubic feet
Tables-4 Central Planning Area Lease Sale 247 Supplemental EIS

Table 3-2

Offshore Scenario Information Related to a Typical Lease Sale in the Central Planning Area

Offshore Subareas1

Total CPA2

0-60 m 60-200 m 200-800 m 800-1,600 m 1,600-2,400 m >2,400 m

Wells Drilled

 Exploration and Delineation Wells 62-121 24-46 21-42 15-29 18-36 28-55 168-329

 Development and Production Wells 78-152 32-58 26-53 20-38 24-46 35-70 215-417

 Producing Oil Wells 11-21 5-8 16-32 12-23 15-29 22-43 81-156

 Producing Gas Wells 58-115 23-44 7-15 5-10 6-11 9-19 108-241

Production Structures

 Installed 28-54 3-6 1-2 1 1-2 1-2 35-67

 Removed Using Explosives 18-36 2-4 0 0 0 0 20-40

 Total Removed 25-49 3-5 1-2 1 1-2 1-2 32-61

Method of Transportation3

 Percent Piped >99% >99% >99% >99% 90->99% 93->99%

 Percent Barged <1% 0% 0% 0% 0% <1%

 Percent Tankered4 0% 0% 0% 0% 0-10% 0-6%

Length of Installed Pipelines (km)5 216-586 NA NA NA NA NA 628-1870

Service-Vessel Trips (1,000’s round trips) 32-61 5-10 3-6 17-19 18-35 19-37 94-168

Helicopter Operations (1,000’s operations) 557-1,470 63-163 21-54 14-36 21-54 21-54 696-1,815

1 Refer to Figure 3-1. 2 Subareas totals may not add up to the planning area total because of rounding. 3 100% of gas is assumed to be piped. 4 Tankering is forecasted to occur only in water depths >1,600 m.

5 Projected length of pipelines does not include length in State waters.

NA = not available.
Tables Tables-5

Table 3-3

Offshore Scenario Information Related to OCS Program Activities in the Gulf of Mexico (WPA, CPA, and EPA) for 2012-2051

Offshore Subareas1

Total OCS2

0-60 m 60-200 m 200-800 m 800-1,600 m 1,600-2,400 m >2,400 m

Wells Drilled

 Exploration and Delineation Wells 2,730-3,900 990-1,390 920-1,350 700-960 770-1,030 790-1,170 6,910-9,827

 Development and Production Wells 3,380-4,820 1,240-1,730 1,130-1,670 860-1,190 950-1,280 970-1,450 8,530-12,180

 Producing Oil Wells 520-701 215-278 704-1,030 574-783 663-873 620-915 3,296-4,605

 Producing Gas Wells 2,510-3,629 885-1,272 306-470 196-287 187-267 250-385 4,334-6,320

Production Structures

 Installed 1,210-1,720 110-160 26-40 25-30 32-33 32-38 1,435-2,026

 Removed Using Explosives 796-1,139 69-104 3-4 0 0 0 868-1,247

 Total Removed 1,090-1,560 100-150 24-34 20-28 23-30 22-33 1,279-1,837

Method of Transportation3

 Percent Piped >99% >99% >99% >99% 87->99% 92->99%

 Percent Barged <1% 0% 0% 0% 0% <1%

 Percent Tankered4 0% 0% 0% 0% 0-13% 0-7%

Length of Installed Pipelines (km)5 10,482-21,121 NA NA NA NA NA 30,428-69,749

Service-Vessel Trips (1,000’s round trips) 1,366-1,942 196-280 111-162 466-619 584-626 587-719 3,310-4,382

Helicopter Operations (1,000’s operations) 24,221-47,322 2,297-4,444 595-1,174 574-1,111 676-1,287 888-1,738 28,710-55,605

1 Refer to Figure 3-1. 2 Subareas totals may not add up to the planning area total because of rounding.

3 100% of gas is assumed to be piped.

4 Tankering is forecasted to occur only in water depths >1,600 m.

5 Projected length of pipelines does not include length in State waters.

NA = not available.
Tables-6 Central Planning Area Lease Sale 247 Supplemental EIS

Table 3-4

Offshore Scenario Information Related to OCS Program Activities in the Central Planning Area for 2012-2051

Offshore Subareas1

Total CPA2

0-60 m 60-200 m 200-800 m 800-1,600 m 1,600-2,400 m >2,400 m

Wells Drilled

 Exploration and Delineation Wells 2,230-3,160 820-1,160 700-1,030 540-730 700-940 730-1,090 5,720-8,110

 Development and Production Wells 2,760-3,900 1,020-1,440 860-1,270 670-900 870-1,160 900-1,350 7,080-10,020

 Producing Oil Wells 446-592 188-240 534-775 449-592 609-796 575-848 2,801-3,843

 Producing Gas Wells 2,034-2,918 722-1,050 236-365 151-218 171-244 235-362 3,549-5,157

Production Structures

 Installed 990-1,390 90-130 20-30 20-25 30 30-35 1,180-1,640

 Removed Using Explosives 650-920 55-83 2-3 0 0 0 707-1,006

 Total Removed 890-1,260 80-120 18-26 16-21 21-27 21-31 1,046-1,485

Method of Transportation3

 Percent Piped >99% >99% >99% >99% 90->99% 93->99%

 Percent Barged <1% 0% 0% 0% 0% >1%

 Percent Tankered4 0% 0% 0% 0% 0-10% 0-6%

Length of Installed Pipelines (km)5 8,515-16,993 NA NA NA NA NA 25,204-57,177

Service-Vessel Trips (1,000’s round trips) 1,117-1,570 161-230 85-126 371-469 546-569 549-663 2,829-3,627

Helicopter Operations (1,000’s operations) 19,975-37,825 1,902-3,560 404-801 404-668 595-801 595-890 23,780-44,500

1 Refer to Figure 3-1. 2 Subareas totals may not add up to the planning area total because of rounding.

3 100% of gas is assumed to be piped.

4 Tankering is forecasted to occur only in water depths >1,600 m.

5 Projected length of pipelines does not include length in State waters.

NA = not available.
Tables Tables-7 

Table 3-5 

Annual Volume of Produced Water Discharged by Depth

(millions of bbl)

Year Shelf

0-60 m

Shelf

60-200 m

Slope

200-400 m

Deepwater

400-800 m

Deepwater

800-1,600 m

UltraDeepwater

1,601-2,400 m

UltraDeepwater

>2,400 m

Total

2000 370.6 193.1 35.5 25.6 12.2 0.0 0.0 637.0

2001 364.2 185.2 35.0 32.0 16.6 0.0 0.0 633.0

2002 344.6 180.4 32.5 35.2 21.4 0.0 0.0 614.1

2003 359.4 182.9 31.2 39.0 35.5 0.2 0.0 648.2

2004 346.7 160.5 29.3 36.9 39.2 1.8 0.0 614.4

2005 270.0 113.5 23.1 33.5 43.0 5.8 0.0 488.9

2006 260.3 99.6 20.6 35.1 61.6 12.4 0.0 489.6

2007 307.0 139. 3 22.2 40.0 70.6 15.5 0.1 594.7

2008 252.7 118.6 15.9 32.7 60.1 16.1 0.1 496.3

2009 265.2 109.2 19.9 39.2 65.6 25.0 0.1 524.2

2010 278.4 115.7 20.9 40.7 56.8 32.5 0.1 545.1

2011 273.7 117.0 20.7 39.7 67.7 32.2 0.1 551.1

2012 240.7 108.9 20.0 35.0 71.4 32.3 0.1 509.2

2013 248.8 104.2 20.0 33.1 75.9 36.9 0.3 519.2

2014 226.6 91.9 17.1 32.0 72.1 45.0 0.9 485.6

Source: Gonzales, official communication, 2015.

Table 4-1

Unusual Mortality Event Cetacean Data for the Northern Gulf of Mexico

Cetaceans Stranded Phase of Oil-Spill Response Dates

114 cetaceans stranded Prior to the response phase for the oil 

spill

February 1, 2010-April 29, 2010

122 cetaceans stranded or 

were reported dead offshore

During the initial response phase to 

the oil spill

April 30, 2010-November 2, 2010

1,206 cetaceans stranded* After the initial response phase ended November 3, 2010-November 29, 

2015**

Note: Numbers are preliminary and may be subject to change. As of November 29, 2015, the unusual mortality 

event involves 1,442 cetacean “strandings” in the northern Gulf of Mexico (USDOC, NMFS, 2015).

* This number includes 15 dolphins that were killed incidental to fish-related scientific data collection and 

1 dolphin that was killed incidental to trawl relocation for a dredging project.

** The initial response phase ended for all four states on November 2, 2010, but then reopened for eastern and 

central Louisiana on December 3, 2010, and then closed again on May 25, 2011.
Tables-8 Central Planning Area Lease Sale 247 Supplemental EIS

Table 4-2

Recreational and Tourism Employment and Value-Added in BOEM’s Economic Impact Areas in 2013

Economic Impact 

Area (EIA)

Recreational 

Employment

Recreational 

Value-Added

Tourism 

Employment

Tourism 

Value-Added

TX-1 68,769 2,596,402,975 19,081 1,203,931,388

TX-2 48,362 1,868,401,512 15,225 739,484,187

TX-3 366,048 15,331,216,510 123,709 8,466,549,982

TX-4 5,033 188,869,415 1,227 100,190,697

TX-5 18,829 709,291,174 4,763 395,566,972

TX-6 1,417 53,257,782 387 23,864,658

LA-1 14,399 683,645,908 6,149 293,572,508

LA-2 2,799 105,494,355 775 46,049,357

LA-3 32,869 1,315,185,525 9,639 566,173,408

LA-4 17,725 788,255,437 6,269 274,186,740

LA-5 50,188 2,028,801,718 14,122 975,127,188

LA-6 89,036 4,458,755,918 34,493 1,976,234,240

LA-7 23,637 948,326,917 6,577 379,903,898

MS-1 33,103 1,560,781,492 14,167 545,645,437

MS-2 1,475 54,100,278 391 19,098,912

AL-1 37,649 1,274,887,170 10,477 681,999,085

AL-2 3,483 120,034,728 873 73,873,691

FL-1 72,212 2,756,594,208 24,852 1,233,121,800

FL-2 31,357 1,173,072,208 10,300 445,046,333

FL-3 7,954 278,409,013 2,438 114,397,442

FL-4 67,758 2,497,491,474 18,301 1,153,527,693

FL-5 254,735 11,239,013,764 80,319 4,948,465,196

FL-6 115,642 5,472,107,011 45,683 2,263,684,576

Texas EIAs 508,457 20,747,439,369 164,393 10,929,587,884

Louisiana EIAs 230,653 10,328,465,778 78,023 4,511,247,338

Mississippi EIAs 34,578 1,614,881,770 14,558 564,744,348

Alabama EIAs 41,132 1,394,921,898 11,349 755,872,776

Florida EIAs 549,658 23,416,687,679 181,891 10,158,243,038

All EIAs 1,364,478 57,502,396,493 450,215 26,919,695,385

Sources: Eastern Research Group (2014) and IMPLAN Group LLC (2015).
Tables Tables-9

Table 4-3

Economic and Demographic Information for BOEM’s Economic Impact Areas in 2015

Economic Variables Demographic Variables

EIA Population Employment Gross Regional 

Product*

Income 

Per Capita

Median 

Age

Male 

Percent White Black Hispanic Native American Asian

TX-1 1,713,140 752,177 45,961,422 32,038 32.2 49.0% 7.4% 0.5% 91.1% 0.1% 0.9%

TX-2 757,829 440,230 40,665,099 38,469 39.3 50.0% 37.8% 4.9% 55.4% 0.3% 1.6%

TX-3 6,340,375 3,897,727 433,804,883 48,201 35.9 49.8% 37.1% 17.1% 37.5% 0.3% 7.9%

TX-4 163,193 59,934 4,119,292 35,597 40.2 49.5% 75.9% 9.0% 13.9% 0.4% 0.7%

TX-5 374,402 205,831 18,218,742 41,889 37.1 50.9% 53.7% 25.9% 17.0% 0.4% 3.0%

TX-6 50,558 22,415 1,388,043 30,964 41.6 50.0% 74.6% 18.4% 5.8% 0.5% 0.7%

LA-1 204,559 119,065 10,819,182 36,778 38.5 48.8% 70.2% 24.9% 3.0% 0.5% 1.4%

LA-2 89,805 41,414 4,077,567 35,581 34.1 52.0% 75.1% 14.5% 7.2% 1.3% 1.8%

LA-3 588,935 337,248 34,334,083 34,397 36.7 49.2% 68.5% 26.7% 3.1% 0.5% 1.2%

LA-4 364,662 219,030 23,652,206 41,208 37.6 49.3% 67.4% 23.4% 4.6% 3.0% 1.6%

LA-5 858,991 533,746 49,605,913 37,132 37.3 48.7% 56.6% 37.0% 4.0% 0.3% 2.2%

LA-6 934,399 612,228 59,338,051 38,990 36.3 48.5% 46.3% 39.8% 9.9% 0.4% 3.7%

LA-7 425,178 207,007 16,064,830 35,795 38.4 48.7% 73.8% 19.9% 4.6% 0.4% 1.2%

MS-1 442,571 230,577 16,142,025 32,617 39.2 49.5% 71.4% 20.6% 5.1% 0.5% 2.5%

MS-2 68,605 21,814 1,132,099 25,130 38.2 52.1% 79.7% 18.0% 1.6% 0.4% 0.3%

AL-1 620,990 338,439 22,529,209 34,669 40.0 48.2% 66.7% 27.3% 3.4% 0.9% 1.8%

AL-2 115,636 51,498 3,406,314 29,539 42.2 49.2% 57.7% 37.5% 1.6% 2.8% 0.4%

FL-1 913,655 499,506 34,545,257 37,887 39.2 50.4% 75.8% 14.1% 6.2% 0.8% 3.1%

FL-2 513,271 273,299 18,167,329 27,898 40.4 50.8% 61.9% 29.5% 5.9% 0.5% 2.2%

FL-3 237,107 89,044 5,422,707 25,750 41.3 54.5% 70.5% 22.0% 6.3% 0.5% 0.8%

FL-4 1,436,702 604,746 36,362,418 31,692 48.6 48.7% 75.7% 11.2% 10.2% 0.3% 2.5%

FL-5 4,151,943 2,229,968 164,060,192 40,530 45.4 48.6% 67.0% 11.9% 17.6% 0.3% 3.2%

FL-6 1,495,975 752,134 47,563,571 36,586 45.5 49.8% 68.4% 7.9% 21.8% 0.3% 1.5%

*Gross Regional Product is presented in thousands of dollars.

Source: Woods & Poole Economics, Inc., 2015.
 

Tables-10 Central Planning Area Lease Sale 247 Supplemental EIS

Table 4-4

Economic and Demographic Information for BOEM’s Economic Impact Areas in 2050

Economic Variables Demographic Variables

EIA Population Employment Gross Regional 

Product

Income Per 

Capita

Median 

Age

Male 

Percent White Black Hispanic Native American Asian

TX-1 3,211,678 1,510,514 122,978,193 53,332 37.1 49.6% 3.9% 0.5% 94.8% 0.0% 0.8%

TX-2 901,108 594,209 74,012,799 63,066 39.3 50.9% 26.1% 6.4% 64.8% 0.3% 2.5%

TX-3 11,318,207 7,262,133 1,095,629,086 71,185 37.7 50.1% 18.8% 14.1% 53.8% 0.2% 13.0%

TX-4 244,211 93,227 7,722,339 52,521 41.2 49.8% 61.6% 10.3% 26.3% 0.5% 1.4%

TX-5 407,234 257,973 29,621,937 60,544 40.4 53.4% 32.9% 23.2% 40.0% 0.3% 3.5%

TX-6 63,947 34,006 2,596,031 46,265 40.6 49.9% 52.4% 30.0% 15.5% 0.6% 1.4%

LA-1 248,184 158,977 18,087,099 51,816 40.5 48.8% 65.3% 26.8% 4.9% 0.7% 2.3%

LA-2 108,507 56,413 7,166,445 54,645 35.8 51.3% 68.3% 15.5% 12.1% 1.5% 2.6%

LA-3 776,541 522,500 71,038,683 52,350 40.2 49.5% 62.4% 30.6% 4.9% 0.5% 1.6%

LA-4 428,273 322,607 46,645,705 64,164 41.5 49.6% 56.0% 26.2% 11.3% 3.6% 3.0%

LA-5 1,253,207 823,740 94,931,543 54,332 42.7 49.2% 49.4% 41.3% 6.1% 0.3% 3.0%

LA-6 924,191 755,835 94,351,565 56,896 39.5 49.3% 32.7% 42.0% 19.6% 0.4% 5.3%

LA-7 647,551 335,006 34,109,728 51,203 41.5 48.5% 64.4% 23.5% 9.6% 0.4% 2.0%

MS-1 527,738 298,996 21,694,991 46,692 41.0 49.2% 63.0% 24.4% 9.3% 0.4% 2.8%

MS-2 87,917 28,786 1,880,313 36,234 41.1 53.1% 72.0% 24.9% 2.4% 0.3% 0.4%

AL-1 840,489 525,223 43,583,841 50,977 41.9 47.9% 61.7% 28.6% 6.2% 0.8% 2.7%

AL-2 116,672 66,584 5,802,458 45,800 46.3 50.7% 45.4% 46.6% 2.9% 4.2% 0.9%

FL-1 1,271,987 756,445 67,816,779 55,604 42.5 51.9% 69.3% 16.9% 9.3% 0.6% 3.9%

FL-2 721,561 396,668 33,967,696 38,977 45.2 52.1% 53.3% 37.6% 5.9% 0.4% 2.8%

FL-3 335,944 132,391 10,488,863 36,453 44.1 56.4% 64.1% 26.4% 7.9% 0.4% 1.2%

FL-4 2,445,932 1,050,736 78,635,995 47,113 52.0 50.3% 69.2% 12.7% 14.7% 0.3% 3.1%

FL-5 6,237,613 3,589,267 365,775,112 63,788 45.0 49.5% 45.3% 14.1% 34.0% 0.2% 6.4%

FL-6 2,465,544 1,320,017 117,042,429 57,573 47.0 51.0% 50.9% 7.4% 40.0% 0.2% 1.5%

*Gross Regional Product is presented in thousands of dollars.

Source: Woods & Poole Economics, Inc., 2015.
Tables Tables-11

References 

Gonzales, S. 2015. Official communication. Email regarding updated produced water data through 

2014. February 5, 2015. 

U.S. Dept. of Commerce. National Marine Fisheries Service. 2015. Cetacean unusual mortality event in 

the northern Gulf of Mexico (2010-present). Internet website: http://www.nmfs.noaa.gov/pr/health/

mmume/cetacean_gulfofmexico.htm. Updated November 29, 2015. Accessed December 4, 2015. 

Woods & Poole Economics, Inc. 2015. The 2015 complete economic and demographic data source 

(CEDDS) on CD-ROM.

APPENDIX A 

 

MEMORANDUM OF AGREEMENT

BETWEEN THE BUREAU OF OCEAN ENERGY MANAGEMENT 

AND THE NATIONAL PARK SERVICE

Memorandum of Agreement A-3 
A-4 Central Planning Area Lease Sale 247 Supplemental EIS
Memorandum of Agreement A-5 

APPENDIX B 

 

CATASTROPHIC SPILL EVENT ANALYSIS: 

HIGH-VOLUME, EXTENDED-DURATION OIL SPILL

RESULTING FROM LOSS OF WELL CONTROL 

ON THE GULF OF MEXICO OUTER CONTINENTAL SHELF

Catastrophic Spill Event Analysis B-iii

TABLE OF CONTENTS

Page

FIGURES .................................................................................................................................................. B-v

TABLES ................................................................................................................................................... B-v

B. CATASTROPHIC SPILL EVENT ANALYSIS: HIGH-VOLUME, EXTENDED-DURATION 

OIL SPILL RESULTING FROM LOSS OF WELL CONTROL ON THE GULF OF MEXICO 

OUTER CONTINENTAL SHELF .................................................................................................... B-1

B.1. Introduction ............................................................................................................................. B-1

B.1.1. What is a Catastrophic Event? .................................................................................. B-1

B.1.2. Methodology ............................................................................................................ B-2

B.1.2.1. Geographic Scope ................................................................................... B-2

B.1.2.2. Impact-Producing Factors and Scenario ................................................. B-3

B.1.2.3. OSRA Catastrophic Run ......................................................................... B-3

B.1.2.4. Environmental and Socioeconomic Impacts ........................................... B-3

B.1.3. How to Use This Analysis ........................................................................................ B-3

B.2. Impact-Producing Factors and Scenario (Phases 1-4) ............................................................ B-4

B.2.1. Phase 1—Initial Event .............................................................................................. B-4

B.2.2. Phase 2—Offshore Spill ........................................................................................... B-4

B.2.2.1. Duration of Spill ...................................................................................... B-4

B.2.2.1.1. Shallow Water ...................................................................... B-5

B.2.2.1.2. Deep Water ........................................................................... B-5

B.2.2.2. Area of Spill ............................................................................................ B-5

B.2.2.3. Volume of Spill ....................................................................................... B-5

B.2.2.3.1. Shallow Water ...................................................................... B-6

B.2.2.3.2. Deep Water ........................................................................... B-6

B.2.2.4. Oil in the Environment: Properties and Persistence ............................... B-6

B.2.2.5. Release of Natural Gas ............................................................................ B-7

B.2.2.6. Deepwater Subsea Containment ............................................................. B-7

B.2.2.7. Offshore Cleanup Activities .................................................................... B-9

B.2.2.7.1. Shallow Water ...................................................................... B-9

B.2.2.7.2. Deep Water ......................................................................... B-10

B.2.2.7.3. Vessel Decontamination Stations ....................................... B-10

B.2.2.8. Severe Weather ..................................................................................... B-11

B.2.3. Phase 3—Onshore Contact ..................................................................................... B-11

B.2.3.1. Duration ................................................................................................ B-11

B.2.3.1.1. Shallow Water .................................................................... B-12

B.2.3.1.2. Deep Water ......................................................................... B-12

B.2.3.2. Volume of Oil Contacting Shore ........................................................... B-12

B.2.3.3. Length of Shoreline Contacted .............................................................. B-12

B.2.3.3.1. Shallow Water .................................................................... B-13

B.2.3.3.2. Deep Water ......................................................................... B-13

B.2.3.4. Severe Weather ..................................................................................... B-13

B.2.3.5. Onshore Cleanup Activities .................................................................. B-14

B.2.3.5.1. Shallow Water .................................................................... B-14

B.2.3.5.2. Deep Water ......................................................................... B-14
B-iv Central Planning Area Lease Sale 247 Supplemental EIS

B.2.3.5.3. Response Considerations for Sand Beaches for Both 

Shallow-Water and Deepwater Spills ................................. B-14

B.2.3.5.4. Response Considerations for Marshes for Both ShallowWater and Deepwater Spills ............................................... B-15

B.2.3.5.5. Response Considerations for Nearshore Waters for Both 

Shallow-Water and Deepwater Spills ................................. B-15

B.2.4. Phase 4—Post-Spill, Long-Term Recovery ........................................................... B-15

B.2.4.1. Response Considerations for Sand Beaches, Marshes, and Nearshore 

Waters for both Shallow-Water and Deepwater Spills ......................... B-16

B.3. Description of the Environment and Impact Analysis .......................................................... B-17

B.3.1. Long Duration—Large Volume Spill within the Gulf of Mexico .......................... B-17

B.3.1.1. Air Quality ............................................................................................ B-17

B.3.1.2. Water Quality ........................................................................................ B-19

B.3.1.3. Coastal Barrier Beaches and Associated Dunes .................................... B-24

B.3.1.4. Wetlands ................................................................................................ B-25

B.3.1.5. Seagrass Communities .......................................................................... B-28

B.3.1.6. Live Bottoms (Pinnacle Trend and Low Relief) ................................... B-30

B.3.1.7. Topographic Features ............................................................................ B-36

B.3.1.8. Sargassum Communities ....................................................................... B-42

B.3.1.9. Chemosynthetic Deepwater Benthic Communities ............................... B-45

B.3.1.10. Nonchemosynthetic Deepwater Benthic Communities ......................... B-50

B.3.1.11. Soft Bottom Benthic Communities ....................................................... B-54

B.3.1.12. Marine Mammals .................................................................................. B-60

B.3.1.13. Sea Turtles ............................................................................................. B-63

B.3.1.14. Diamondback Terrapins ........................................................................ B-66

B.3.1.15. Beach Mice ........................................................................................... B-69

B.3.1.16. Coastal, Marine, and Migratory Birds ................................................... B-70

B.3.1.17. Fish Resources and Essential Fish Habitat ............................................ B-76

B.3.1.18. Commercial Fisheries............................................................................ B-79

B.3.1.19. Recreational Fishing.............................................................................. B-81

B.3.1.20. Recreational Resources ......................................................................... B-82

B.3.1.21. Archaeological Resources ..................................................................... B-84

B.3.1.22. Land Use and Coastal Infrastructure ..................................................... B-87

B.3.1.23. Demographics ....................................................................................... B-88

B.3.1.24. Economic Factors .................................................................................. B-89

B.3.1.25. Environmental Justice ........................................................................... B-90

B.3.1.26. Species Considered due to U.S. Fish and Wildlife Service Concerns .. B-94

B.4. Preparers ............................................................................................................................... B-96

B.5. References ............................................................................................................................. B-96
Catastrophic Spill Event Analysis B-v 

FIGURES

Page

Figure B-1. Location of Seven Hypothetical Oil-Spill Launch Points for OSRA within the 

Gulf of Mexico. ............................................................................................................... B-124

Figure B-2. Spatial Frequency (%) of the Watermass Associated with the Loop Current in the 

Eastern Gulf of Mexico based on Data for the Period 1976-2003 .................................. B-125

Figure B-3. Summary of Avian Species Collected by Date Obtained from the U.S. Fish and 

Wildlife Service as Part of the Deepwater Horizon Post-Spill Monitoring and 

Collection Process through May 12, 2011 ...................................................................... B-126

TABLES

Page

Table B-1. Blowout Scenarios and Key Differences in Impacts, Response, and/or Intervention ..... B-127

Table B-2. Properties and Persistence by Oil Component Group ..................................................... B-128

Table B-3. Annual Volume of Produced Water Discharged by Depth (millions of barrels) ............ B-129

Table B-4. Description of the Scenario for a Catastrophic Spill Event Occurring in Shallow 

Water or Deep Water (assumptions are described in detail in the text) ......................... B-130

Table B-5. Birds Collected and Summarized by the U.S. Fish and Wildlife Service: 

Post-Deepwater Horizon Explosion, Oil Spill, and Response in the Gulf of Mexico .... B-133

Table B-6. Federally Listed Avian Species Considered by State and Associated Planning Area 

in the Gulf of Mexico ...................................................................................................... B-140

Catastrophic Spill Event Analysis B-1 

B. CATASTROPHIC SPILL EVENT ANALYSIS: HIGH-VOLUME, 

EXTENDED-DURATION OIL SPILL RESULTING FROM LOSS 

OF WELL CONTROL ON THE GULF OF MEXICO OUTER 

CONTINENTAL SHELF

B.1. INTRODUCTION

In 1986, the Council on Environmental Quality (CEQ) regulations were amended to rescind the 

requirement to prepare a “worst-case analysis” for an environmental impact statement (EIS) (refer to 

40 CFR § 1502.22(b)(4)). The regulation, as amended, states that catastrophic, low-probability impacts 

must be analyzed if the analysis is “supported by credible scientific evidence, is not based on pure 

conjecture, and is within the rule of reason.”

The August 16, 2010, CEQ report, prepared following the Deepwater Horizon explosion, oil spill, 

and response in the Gulf of Mexico, recommended that the Bureau of Ocean Energy Management 

(BOEM), formerly the Minerals Management Service (MMS) and Bureau of Ocean Energy Management, 

Regulation and Enforcement (BOEMRE), should “ensure that National Environmental Policy Act 

(NEPA) documents provide decisionmakers with a robust analysis of reasonably foreseeable impacts, 

including an analysis of reasonably foreseeable impacts associated with low-probability catastrophic 

spills for oil and gas activities on the Outer Continental Shelf” (CEQ, 2010). This evaluation is a robust 

analysis of the impacts from low-probability catastrophic spills and will be made available to all 

applicable decisionmakers including, but not limited to, the Secretary of the Department of the Interior 

(USDOI) for the National Five-Year Program, the Assistant Secretary of Land and Minerals Management 

for an oil and gas lease sale, and the Regional Supervisors of the Gulf of Mexico OCS Region’s Office of 

Environment and Office of Leasing and Plans.

It should be noted that the analysis presented here is intended to be a general overview of the 

potential effects of a catastrophic spill in the Gulf of Mexico. As such, the Catastrophic Spill Event 

Analysis should be read with the understanding that further detail about accidental oil impacts on a 

particular resource may be found in the analysis in this Supplemental EIS or the analyses in the “prior 

2012-2017 Gulf of Mexico EISs”: Gulf of Mexico OCS Oil and Gas Lease Sales: 2012-2017; Western 

Planning Area Lease Sales 229, 233, 238, 246, and 248; Central Planning Area Lease Sales 227, 231, 

235, 241, and 247, Final Environmental Impact Statement (2012-2017 WPA/CPA Multisale EIS; 

USDOI, BOEM, 2012); Gulf of Mexico OCS Oil and Gas Lease Sales: 2013-2014; Western Planning 

Area Lease Sale 233; Central Planning Area Lease Sale 231, Final Supplemental Environmental Impact 

Statement (WPA 233/CPA 231 Supplemental EIS; USDOI, BOEM, 2013a); Gulf of Mexico OCS Oil and 

Gas Lease Sales: 2015-2017; Central Planning Area Lease Sales 235, 241, and 247, Final Supplemental 

Environmental Impact Statement (CPA 235/241/247 Supplemental EIS, USDOI, BOEM, 2014a); and 

Gulf of Mexico OCS Oil and Gas Lease Sales: 2016 and 2017; Central Planning Area Lease Sales 241 

and 247; Eastern Planning Area Lease Sale 226, Final Supplemental Environmental Impact Statement 

(CPA 241/247 and EPA 226 Supplemental EIS; USDOI, BOEM, 2015). 

B.1.1. What is a Catastrophic Event?

As applicable to NEPA, Eccleston (2008) defines a catastrophic event as “large-scale damage 

involving destruction of species, ecosystems, infrastructure, or property with long-term effects, and/or 

major loss of human life.” For oil and gas activities on the Outer Continental Shelf (OCS), a catastrophic 

event is a high-volume, extended-duration oil spill regardless of the cause, whether natural disaster (i.e., 

hurricane) or manmade (i.e., human error and terrorism). This high-volume, extended-duration oil spill, 

or catastrophic spill, has been further defined by the National Oil and Hazardous Substances Pollution 

Contingency Plan as a “spill of national significance” or “a spill which, because of its severity, size, 

location, actual or potential impact on the public health and welfare or the environment, or the necessary 

response effort, is so complex that it requires extraordinary coordination of federal, state, local, and 

responsible party resources to contain and cleanup the discharge” (40 CFR part 300, Appendix E). 

Each oil-spill event is unique; its outcome depends on several factors, including time of year and 

location of release relative to winds, currents, land, and sensitive resources; specifics of the well (i.e., 
B-2 Central Planning Area Lease Sale 247 Supplemental EIS

flow rates, hydrocarbon characteristics, and infrastructure damage); and response effort (i.e., speed and 

effectiveness). For this reason, the severity of impacts from an oil spill cannot be predicted based on 

volume alone, although a minimum volume of oil must be spilled to reach catastrophic impacts. 

Though large spills may result from a pipeline rupture, such events will not result in a catastrophic 

spill because the ability to detect leaks and shut off pipelines limits the amount of the spill to the contents 

of the pipeline. The largest, non-blowout-related spill on the Gulf of Mexico OCS occurred in 1967, a 

result of internal pipeline corrosion following initial damage by an anchor. In 13 days, 160,638 barrels 

(bbl) of oil leaked (USDOI, BSEE, 2015); however, no significant environmental impacts were recorded 

as a result of this spill.

Although loss of well control is defined as the uncontrolled flow of reservoir fluid that may result in 

the release of gas, condensate, oil, drilling fluids, sand, or water, it is a broad term that includes very 

minor well control incidents as well as the most severe well control incidents. Historically, loss of well 

control incidents occurred during development drilling operations, but loss of well control incidents can 

occur during exploratory drilling, production, well completions, or workover operations. These losses of 

well control incidents may occur between formations penetrated in the wellbore or at the seafloor.

Prior to the Deepwater Horizon explosion, oil spill, and response, the two largest spills resulting from 

a loss of well control in U.S. waters of the Gulf of Mexico occurred in 1970 and released 30,000 and 

53,000 bbl of oil, respectively (USDOI, BSEE, 2015). These incidents resulted in four human fatalities. 

Although these incidents occurred only 8-14 miles (mi) (13-26 kilometers [km]) from shore, there was 

minor shoreline contact with oil (USDOC, NOAA, Office of Response and Restoration, 2010a and 

2010b). In 1987, a blowout of the Mexican exploratory oil well, YUM II, resulted in a spill of 58,640 bbl 

and 75 mi (121 km) of impacted shoreline (USDOC, NOAA, Hazardous Materials Response and 

Assessment Division, 1992). However, none of these spills met the previously described definitions of a 

catastrophic event or spill.

A blowout is a more severe loss of well control incident that creates a greater risk of a large oil spill 

and serious human injury. Two blowouts that resulted in catastrophic spills have occurred in U.S. and 

Mexican waters of the Gulf of Mexico. On June 3, 1979, the Ixtoc I well blowout in shallow water (water 

depth of 164 feet [ft] [50 meters [m]] and 50 mi [80 km] offshore in the Bay of Campeche, Mexico) 

spilled 3.5 million barrels (MMbbl) of oil in 10 months (USDOC, NOAA, Office of Response and 

Restoration, 2010c; USDOC, NOAA, Hazardous Materials Response and Assessment Division, 1992; 

ERCO, 1982). On April 20, 2010, the Macondo well blowout (Deepwater Horizon explosion, oil spill, 

and response) in deep water (4,992 ft; 1,522 m) 48 mi (77 km) offshore in Mississippi Canyon Block 252, 

spilled an estimated 4.9 MMbbl of oil until it was capped approximately 3 months later. Due to being 

classified as catastrophic, the Ixtoc I and Macondo well blowouts and spills were utilized to develop the 

catastrophic spill event scenario in this analysis.

B.1.2. Methodology

Two general approaches are utilized to analyze a catastrophic event under NEPA. The first approach 

is a bounding analysis for each individual resource category (e.g., marine mammals and sea turtles). A 

bounding analysis involves selecting and evaluating a different set of factors and scenarios for each 

resource in the context of a worst-case analysis. The second approach involves the selection of a single 

set of key circumstances that, when combined, result in catastrophic consequences. The second approach 

is used for a site-specific analysis and, consequently, its possible application is more limited. 

Accordingly, this analysis combines the two approaches, relying on a generalized scenario while 

identifying site-specific severity factors for individual resources. This combined approach allows for the 

scientific investigation of a range of possible, although not necessarily probable, consequences of a 

catastrophic blowout and oil spill in the Gulf of Mexico.

B.1.2.1. Geographic Scope

The Gulf of Mexico is a semi-enclosed basin with an extensive history of oil and gas activities and 

unique environmental conditions and hydrocarbon reservoir properties; consequently, this analysis is only 

applicable to the Gulf of Mexico OCS and is not intended for other OCS regions.
Catastrophic Spill Event Analysis B-3 

B.1.2.2. Impact-Producing Factors and Scenario

A hypothetical, yet feasible, scenario (Chapter B.2) was developed to provide a framework for 

identifying the impacts of an extended oil spill from an uncontrolled blowout. Unless noted, this scenario 

is based on the large magnitude, blowout-related oil spills that have occurred in the Gulf of Mexico, i.e., 

Ixtoc I and Macondo well blowouts and spills (discussed in Chapter B.1.1). As noted above, because 

each spill event is unique, its outcome depends on many factors. Therefore, the specific impacts from 

future spills cannot be predicted based on this scenario.

B.1.2.3. OSRA Catastrophic Run

A special Oil-Spill Risk Analysis (OSRA) model run was conducted to estimate the impacts of a 

possible future catastrophic or high-volume, extended-duration oil spill. This analysis emphasized 

modeling a spill that continued for 90 consecutive days by launching spills on each of 90 consecutive 

days, with each trajectory tracked for up to 60 days. The OSRA was conducted for only the trajectories 

of oil spills from hypothetical spill locations to various onshore and offshore environmental resources. 

Data from three hypothetical spill locations located in the Central Planning Area (CPA) and two 

hypothetical spill locations located in the Eastern Planning Area (EPA) were included and are intended 

for use as examples of this type of exercise (Figure B-1). Information on previous catastrophic OSRA 

runs for the CPA can be found in Appendix C of the CPA 235/241/247 Supplemental EIS and 2012-2017 

WPA/CPA Multisale EIS.

The probability of an oil spill contacting a specific resource within a given time of travel from a spill 

point is termed a conditional probability; the condition being that a spill is assumed to have occurred. 

Each trajectory was allowed to continue for as long as 60 days. However, once a hypothetical spill 

contacts land, the spill trajectory is terminated, and the contact is recorded. Although, overall OSRA is 

designed for use as a risk-based assessment, for this analysis, only the conditional probability, the 

probability of contact to the resource, was calculated. The probability of a catastrophic spill occurring 

was not calculated; thus, the combination of the probability of a spill and the probability of contact to the 

resources from the hypothetical spill locations were not calculated. Results from this trajectory analysis 

provide input to the final product by estimating where spills might travel on the ocean’s surface and what 

environmental resources might be contacted if and when another catastrophic spill occurs, but it does not 

provide input on the probability of another catastrophic spill occurring. Further detail on this catastrophic 

OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS. 

B.1.2.4. Environmental and Socioeconomic Impacts

This analysis evaluates the impacts to the Gulf of Mexico’s biological, physical, and socioeconomic 

resources from a catastrophic blowout, oil spill, and associated cleanup activities.

Although the most recent EISs prepared by this Agency for oil and gas lease sales in the Gulf of 

Mexico analyze the potential impacts from smaller oil spills that are more reasonably foreseeable 

(USDOI, MMS, 2007 and 2008), this analysis focuses on the most likely and most significant impacts 

created by a high-volume, extended-duration spill. Because catastrophic consequences may not occur for 

all resources, factors affecting the severity of impacts are identified by the individual resource.

B.1.3. How to Use This Analysis

The purpose of this technical analysis is to assist BOEM in meeting CEQ requirements that require a 

discussion of impacts from catastrophic events. This analysis, based on credible scientific evidence, 

identifies the most likely and most significant impacts from a high-volume blowout and oil spill that 

continues for an extended period of time. The scenario and impacts discussed in Chapters B.2 and B.3

should not be confused with the scenario and impacts anticipated to result from routine activities or the 

more reasonably foreseeable accidental events of the CPA proposed action.

Chapter B.2 is intended to clearly describe the scenario presented for all four phases of a catastrophic 

blowout event and identify the impact-producing factors associated with each phase. Chapter B.3 is 

intended to analyze the impacts of each phase of a catastrophic blowout on various environmental 

resources. These chapters can be used to differentiate the conditions of a catastrophic spill from the 

routine activities and accidental events described in this Supplemental EIS.
B-4 Central Planning Area Lease Sale 247 Supplemental EIS

This technical analysis is designed to be incorporated by reference in future NEPA documents and 

consultations. Therefore, factors that affect the severity of impacts of a high-volume, extended-duration 

spill on individual resources are highlighted for use in subsequent site-specific analyses.

To analyze a hypothetical catastrophic event in an area such as the Gulf of Mexico, several 

assumptions and generalizations were made. However, future project-specific analyses should also 

consider specific details such as potential flow rates for the specific proposed activity, the properties of 

the targeted reservoir, and the proximity to environmental resources of the proposed activities. 

B.2. IMPACT-PRODUCING FACTORS AND SCENARIO (PHASES 1-4)

For the purposes of this analysis, an event similar to the Ixtoc I well blowout and spill that occurred in 

1979 in 160-ft (50-m) water depth will be used as the basis for a shallow water spill and an event similar 

to the Macondo well blowout and spill that occurred in 2010 in the Mississippi Canyon area in 5,000-ft 

(1,524-m) water depth will be used to represent a deepwater spill.

B.2.1. Phase 1—Initial Event

Phase 1 of the scenario is the initiation of a catastrophic blowout incident. While most of the 

environmental and socioeconomic impacts of a catastrophic blowout would occur during the ensuing 

high-volume, extended-duration spill (refer to Chapter B.3), it is important to acknowledge the deadly 

events that could occur in the initial phase of a catastrophic blowout. The following scenario was 

developed to provide a framework for identifying the most likely and most significant impacts during the 

initial phase.

Impacts, response, and intervention depend on the spatial location of the blowout and release. While 

there are several points where a blowout could occur, four major distinctions that are important to the 

analysis of impacts are described in Table B-1. 

For this analysis, an explosion and subsequent fire are assumed to occur. If a blowout associated with 

the drilling of a single exploratory well occurs, a fire could result that would burn for 1 or 2 days. If a 

blowout occurs on a production platform, other wells could feed the fire, allowing it to burn for over a 

month (USDOC, NOAA, Office of Response and Restoration, 2010b). The drilling rig or platform may 

sink. If the blowout occurs in shallow water, the sinking rig or platform may land in the immediate 

vicinity; if the blowout occurs in deep water, the rig or platform could land a great distance away, beyond 

avoidance zones. For example, when the drilling rig Deepwater Horizon sank, it landed 1,500 ft (457 m) 

away on the seafloor. Regardless of water depth, the immediate response would be from search and 

rescue vessels and aircraft, such as U.S. Coast Guard (USCG) cutters, helicopters, and rescue planes.

B.2.2. Phase 2—Offshore Spill

Phase 2 of the analysis focuses on the spill and response in Federal and State offshore waters.

B.2.2.1. Duration of Spill

The duration of the offshore spill from a blowout depends on the time needed for intervention and the 

time the remaining oil persists offshore. If a blowout occurs and the damaged surface facilities preclude 

well reentry operations, a relief well may be needed to regain control. The time required to drill the relief 

well depends on the complexity of the intervention, the location of a suitable rig, the type of operation 

that must be terminated to release the rig (e.g., casing may need to be run before releasing the rig), and the 

logistics in mobilizing personnel and equipment to the location. A blown-out well may also be 

successfully capped prior to completion of relief wells, as occurred in the Macondo well blowout. In 

terms of persistence of spilled oil on surface waters, oil from the Macondo well blowout did not persist 

for more than 30 days (OSAT, 2010). However, based on BOEM’s weathering modeling (refer to 

Appendix C of the CPA 235/241/247 Supplemental EIS), it is assumed that oil could persist on surface 

waters for as long as 1-2 months, depending on the season and year. 
Catastrophic Spill Event Analysis B-5 

B.2.2.1.1. Shallow Water

If a blowout occurs in shallow water, it is estimated that the entire well intervention effort including 

drilling relief wells, if deemed necessary, could take 2 weeks to 3 months. This estimate would include 

1-3 weeks to transport the drilling rig to the well site. Spilled surface oil is not expected to persist more 

than 1-2 months (depending upon the season and environmental conditions) after the flow is stopped. 

Spilled oil is more likely to persist in the offshore environment during colder weather and during wind 

and hydrodynamic conditions that keep the oil offshore. Therefore, the estimated spill duration resulting 

from a shallow water blowout is 11⁄2-5 months (approximately 2 weeks to 3 months for active spillage and 

1-2 months for oil persistence in the environment). 

B.2.2.1.2. Deep Water

If a blowout occurs in deep water, it is estimated that it would take 2-4 weeks to remove debris and to 

install a capping stack or a cap and flow system on a well, if conditions allow this type of intervention. 

The entire intervention effort, if it required drilling relief wells, could take 3-4 months (USDOI, MMS, 

2000; Regg, 2000). This includes 2-4 weeks to transport the drilling rig to the well site. Spilled surface 

oil is not expected to persist more than 1-2 months (depending upon the season and environmental 

conditions) after the flow is stopped. Spilled oil is more likely to persist in the offshore environment 

during colder weather and during wind and hydrodynamic conditions that keep the oil offshore. 

Therefore, the estimated spill duration from a deepwater blowout is 11⁄2-6 months (approximately 2 weeks 

to 4 months for active spillage and 1-2 months for oil persistence in the environment). 

B.2.2.2. Area of Spill

When oil reaches the sea surface, it spreads. The speed and extent of spreading depends on the type 

and volume of oil that is spilled. However, a catastrophic spill would likely spread to hundreds of square 

miles. Also, the oil slick may break into several smaller slicks, depending on local wind patterns that 

drive the surface currents in the spill area.

Subsurface oil observed during both the Ixtoc I and Macondo well blowouts and spills could also 

spread to significant distances depending on environmental conditions (such as hydrodynamics), oil 

chemistry and weathering, and the application of subsea dispersants or mechanical conditions at the 

release point that would diffuse the oil.

B.2.2.3. Volume of Spill

After 50 years of oil and gas exploration and development activity on the continental shelf of the Gulf 

of Mexico, most of the largest oil and natural gas reservoirs thought to exist in shallow-water areas of the 

GOM at drill depths less than 15,000 ft (4,572 m) subsea have been identified. Large undiscovered 

hydrocarbon reservoirs are still thought to exist in shallow-water areas. However, results taken from 

BOEM’s most recent resource assessment study and a review of the more recent shallow-water drilling 

and leasing activity suggest that future discoveries of large reservoirs in the shallow-water areas of the 

GOM are likely to exist greater than 15,000 ft (4,572 m) below sea level where geologic conditions are 

more favorable for natural gas reservoirs to exist than oil reservoirs. In contrast to the shallow-water 

areas of the GOM where the discovery of a new, large, prolific oil reservoir is considered a lowprobability event, the results from BOEM’s resource assessment study pertaining to the deeper water 

areas of the GOM suggest that there is a high probability that many large oil and gas reservoirs have yet 

to be discovered in deep water. BOEM’s forecast for deep water has support from other public and 

private sector resource studies. The forecast is also supported by the results of BOEM’s analysis of 

deepwater leasing and drilling activity, which indicates that the industry is leasing acreage in deepwater 

areas of the GOM where large prospects can be identified and where the majority of exploration and 

development drilling activity targets potentially thick oil reservoirs capable of achieving the high 

production rates necessary to offset the high costs associated with deep water oil development in the 

GOM.
B-6 Central Planning Area Lease Sale 247 Supplemental EIS

B.2.2.3.1. Shallow Water

For this analysis, an uncontrolled flow rate of 30,000 bbl per day is assumed for a catastrophic 

blowout in shallow water. This assumption is based upon the results of well tests in shallow water and 

the maximum flow rate from the 1979 Ixtoc I well blowout, which occurred in shallow water. Using this 

flow rate, the total volume of oil spilled from a catastrophic blowout in shallow water is estimated at 

900,000 bbl to 3 MMbbl from spillage occurring over 1-3 months. In addition to the flow rate, it is 

assumed that any remaining diesel fuel from a sunken drilling rig or platform would also leak. 

B.2.2.3.2. Deep Water

For the purposes of this analysis, an uncontrolled flow rate of 30,000-60,000 bbl per day is assumed 

for a catastrophic blowout in deep water. This flow rate is based on the assumption in Chapter B.2.2.3.1

above, well test results, and the maximum flow rate estimated for the Macondo well blowout and spill 

occurred in deep water. Therefore, the total volume of oil spilled is estimated to be 0.9-7.2 MMbbl over 

1-4 months. In addition, deepwater drilling rigs or platforms hold a large amount of diesel fuel 

(10,000-20,000 bbl). Therefore, it is assumed that any remaining diesel fuel from a sunken structure 

would also leak and add to the spill.

B.2.2.4. Oil in the Environment: Properties and Persistence

The fate of oil in the environment depends on many factors, such as the source and composition of the 

oil, as well as its persistence (NRC, 2003). Persistence can be defined and measured in different ways 

(Davis et al., 2004), but the National Research Council (NRC) generally defines persistence as how long 

oil remains in the environment (NRC, 2003; page 89). Once oil enters the environment, it begins to 

change through physical, chemical, and biological weathering processes (NRC, 2003). These processes 

may interact and affect the properties and persistence of the oil through the following: 

• evaporation (volatilization);

• emulsification (the formation of a mousse); 

• dissolution;

• oxidation (including respiration); and 

• transport processes (NRC, 2003; Scholz et al., 1999). 

Horizontal transport takes place via spreading, advection, dispersion, and entrainment while vertical 

transport takes place via dispersion, entrainment, Langmuir circulation, sinking, overwashing, 

partitioning, and sedimentation (NRC, 2003). The persistence of an oil slick is influenced by the 

effectiveness of oil-spill response efforts and affects the resources needed for oil recovery (Davis et al., 

2004). The persistence of an oil slick may also affect the severity of environmental impacts as a result of 

the spilled oil. 

Crude oils are not a single chemical, but instead are complex mixtures with varied compositions. 

Thus, the behavior of the oil and the risk the oil poses to natural resources depends on the composition of 

the specific oil encountered (Michel, 1992). Generally, oils can be divided into three groups of 

compounds: (1) light-weight; (2) medium-weight; and (3) heavy-weight components. On average, these 

groups are characterized as outlined in Table B-2. 

Of the oil reservoirs sampled in the Gulf of Mexico OCS, the majority fall within the light-weight 

category, while less than one quarter are considered medium-weight and a small portion are considered 

heavy-weight. Oil with an American Petroleum Institute (API) gravity of 10.0 or less would sink and has 

not been encountered in the Gulf of Mexico OCS; therefore, it is not analyzed in this Appendix (USDOI, 

BOEMRE, 2010a).

Heavy-weight oil may persist in the environment longer than the other two types of oil, but the 

medium-weight components within oil present the greatest risks to organisms because, with the exception 

of the alkanes, these medium-weight components are persistent, bioavailable, and toxic (Michel, 1992). 
Catastrophic Spill Event Analysis B-7 

Previous studies (e.g., Johansen et al., 2001) supported the theory that most, if not all, released oil 

would reach the surface of the water column. However, data and observations from the Macondo well 

blowout and spill challenge that theory. While analyses are in their preliminary stages, it appears that 

measurable amounts of hydrocarbons (dispersed or otherwise) were detected in the water column as 

subsurface “plumes” and on the seafloor in the vicinity of the release. While not all of these 

hydrocarbons have been definitively traced back to releases from the Macondo well, these early 

measurements and results warrant a reassessment of previous theories of the ultimate fate of hydrocarbons 

from unintended subsurface releases. It is important to note that the North Sea experiment (Johansen 

et al., 2001) did not include the use of dispersants at or near the source of the subsea oil discharge. 

B.2.2.5. Release of Natural Gas

The quality and quantity of components in natural gas vary widely by the field, reservoir, or location 

from which the natural gas is produced. Although there is not a “typical” makeup of natural gas, it is 

primarily composed of methane (NaturalGas.org, 2012). Thus, if natural gas were to leak into the 

environment, methane may be released into the environment. Limited research is available for the 

biogeochemistry of hydrocarbon gases in the marine environment (Patin, 1999, page 233). Theoretically, 

methane could stay in the marine environment for long periods of time (Patin, 1999, page 237) as 

methane is highly soluble in seawater at the high pressures and cold temperatures found in deepwater 

environments (NRC, 2003, page 108). Methane diffusing through the water column would likely be 

oxidized in the aerobic zone and would rarely reach the air-water interface (Mechalas, 1974, page 23). 

Methane is a carbon source and its introduction into the marine environment could result in diminished 

dissolved oxygen concentrations due to microbial degradation. 

The Macondo well blowout and spill resulted in the emission of an estimated 9.14 x 109

 to 1.29 x 1010

moles of methane from the wellhead (Kessler et al., 2011; Valentine et al., 2010) with maximum 

subsurface methane concentrations of 183-315 micromoles measured in May/June 2010 (Valentine et al., 

2010; Joye et al., 2011). This methane release corresponded to a measurable decrease in oxygen in the 

subsurface plume due to respiration by a community of methanotrophic bacteria. During the Macondo

well blowout and spill, methane and oxygen distributions were measured at 207 stations throughout the 

affected region (Kessler et al., 2011). Based on these measurements, it was concluded that within 

~120 days from the onset of release ~3.0 x 1010 to 3.9 x 1010 moles of oxygen were respired, primarily by 

methanotrophs, and left behind a residual microbial community containing methanotrophic bacteria. The 

researchers further suggested that a vigorous deepwater bacterial bloom respired nearly all the released 

methane within this time and that by analogy, large-scale releases of methane from hydrates in the deep 

ocean are likely to be met by a similarly rapid methanotrophic response. However, hypoxic conditions 

were never reached (OSAT, 2010). Hypoxic conditions are generally agreed to occur when dissolved 

oxygen falls below 2 milligrams/liter (1.4 milliliter/liter) (OSAT, 2010). Note that methane released from 

the Macondo well blowout and spill was generally confined to the subsurface, with minimal amounts 

reaching the atmosphere (Kessler et al., 2011; Ryerson et al., 2011).

B.2.2.6. Deepwater Subsea Containment

The NTL 2010-N10 requires that offshore operators address containment system expectations to be 

able to rapidly contain a spill as a result of a loss of well control from a subsea well. This resulted in the 

development of rapid response containment systems that are available through either the Marine Well 

Containment Company or Helix Well Ops in the Gulf of Mexico. In addition, industry has a multitude of 

vendors available within the GOM region that can provide the services and supplies necessary for debris 

removal capability, dispersant injection capability, and top-hat deployment capability. Many of these 

vendors are already cited for use by the Marine Well Containment Company and Helix Well Ops. The 

Bureau of Safety and Environmental Enforcement (BSEE) has indicated to BOEM that it will not allow 

an operator to begin drilling operations until adequate subsea containment and collection equipment, as 

well as subsea dispersant capability, is determined by BSEE to be available to the operator and is 

sufficient for use in response to a potential incident from the proposed well(s). 
B-8 Central Planning Area Lease Sale 247 Supplemental EIS

Marine Well Containment Company

The Marine Well Containment Company’s (MWCC’s) containment system includes two modular 

capture vessels (MCVs); enhanced subsea umbilical, risers, and flowlines (SURF) equipment; three 

capping stacks; and additional ancillary equipment. The capping stack is uniquely designed to shut off 

the flow of fluid from the well or to provide a conduit to safely flow well fluids to the two MCVs. The 

processing equipment on the MCVs can separate sand and process liquids and gases flowed from a 

damaged subsea well. The MWCC Containment System is built for use in the deepwater U.S. Gulf of 

Mexico, defined as water depths from 500-1,000 ft to 10,000 ft (152-305 m to 3,048 m), in temperatures 

up to 350 °F (177 °C), and under pressure up to 15,000 pounds per square inch (psi). The MWCC’s suite 

of containment equipment enables the company to mobilize and deploy the most appropriate well 

containment technology based upon the unique well control incident and equipment requirements. The 

system has the capacity to contain up to 100,000 bbl of liquid per day (4.2 million gallons/day) and 

handle up to 200 million standard cubic feet of gas per day. The containment system combines 

equipment from the company’s previous interim containment system and the expanded containment 

system. This system is designed to fully contain oil flow in the event of a potential future underwater 

blowout and to address a variety of scenarios. It is envisioned that this system could be fully operational 

within days to weeks after a spill event occurs (MWCC, 2015).

The Marine Well Containment Company’s SURF equipment, which is used to flow fluid from the 

capping stack to the MCVs, as well as to provide dispersant and hydrate mitigation injection, is staged in 

Theodore, Alabama. The MWCC houses, stores, and tests the processing equipment for the two MCVs, 

as well as its capping stacks in Ingleside, Texas. The companies that originated this system have formed 

a nonprofit organization, the Marine Well Containment Company, to operate and maintain the system 

(MWCC, 2015). The MWCC will provide fully trained crews to operate the system, will ensure the 

equipment is operational and ready for rapid response, and will conduct research on new containment 

technologies (MWCC, 2015). 

In the summer of 2012, a full-scale deployment of MWCC’s critical well-control equipment to 

exercise the oil and gas industry’s response to a potential subsea blowout in the deepwater of the Gulf of 

Mexico was conducted by BSEE. The MWCC’s 15,000-psi capping stack system, a 30-ft (9-m) tall, 

100-ton piece of equipment similar to the one that stopped the flow of oil from the Macondo well 

following the Deepwater Horizon explosion in 2010, was successfully tested during this deployment drill. 

During this exercise, the capping stack was deployed from its storage location in Ingleside, Texas, to an 

area in the Gulf of Mexico nearly 200 mi (322 km) from shore. Once on site, the system was lowered to a 

simulated wellhead (a pre-set parking pile) on the ocean floor in nearly 7,000 ft (2,134 m) of water, 

connected to the wellhead, and then pressurized to 10,000 psi. 

Helix Well Ops

Another option for source control and containment in the Gulf of Mexico is through Helix Well Ops. 

Helix Well Ops contracted the equipment that it found useful in the Deepwater Horizon explosion, oil 

spill, and response and offered it to oil and gas producers for use beginning January 1, 2011. This system 

focused on the utilization of the Helix Producer I and the Q4000 vessels. Each of these vessels played a 

role in the response to the Deepwater Horizon explosion and oil spill, and was continually working in the 

Gulf of Mexico. Helix Well Ops’ system, which is referred to as the Helix Fast Response System 

(HFRS), currently has the ability to fully operate in up to 10,000 ft (3,048 m) of water and has 

intervention equipment to cap and contain a well with the mechanical integrity to be shut-in. The HFRS 

also has the ability to capture and process 57,000 bbl of oil per day, 72,000 bbl of liquid per day, and 

120 million standard cubic feet per day at 10,000 psi (Helix Energy Solutions Group, 2014).

In April-May 2013, a full-scale deployment of Helix Well Ops’ critical well-control equipment to 

exercise the oil and gas industry’s response to a potential subsea blowout in the deep water of the Gulf of 

Mexico was conducted by BSEE. Helix Well Ops’ capping stack system is a 20-ft (6-m) tall, 

146,000 pound piece of equipment similar to the one that stopped the flow of oil from the Macondo well 

following the Deepwater Horizon explosion in 2010, It was successfully tested during this unannounced 

deployment drill. The capping stack was deployed from its storage location and once onsite, the system 

was lowered to a simulated wellhead (a pre-set parking pile) on the ocean floor in nearly 5,000 ft 

(1,524 m) of water, connected to the wellhead, and then pressurized to 8,400 psi. 
Catastrophic Spill Event Analysis B-9 

B.2.2.7. Offshore Cleanup Activities

As demonstrated by the Ixtoc I and Macondo well blowouts and spills, a large-scale response effort is 

certain to follow a catastrophic blowout. The number of vessels and responders would steadily increase 

as the spill continued. In the event of a spill, particularly a loss of well control, there is no single method 

of containment and removal that would be 100 percent effective. Removal and containment efforts to 

respond to an ongoing spill offshore would likely require multiple technologies, including source 

containment, mechanical cleanup, in-situ burning of the slick, and chemical dispersants. Even with the 

deployment of all of these spill-response technologies, it is likely that, with the operating limitations of 

today’s spill-response technology, not all of the oil could be contained and removed offshore. 

B.2.2.7.1. Shallow Water

The following are estimates for the deployment of equipment and personnel during a shallow-water 

spill response. Within the first week of an oil spill originating in shallow water, 25 vessels are estimated 

to respond, which would steadily increase to over 3,000 by the end of the spill. This includes about 

25 skimmers in the vicinity of the well at any given time. In addition, recovered oil may be barged to 

shore from recovery vessels. Within the first week, over 500 responders are estimated to be deployed to a 

spill originating in shallow water, which would steadily increase up to 25,000 before the well is capped or 

killed within 2-4 months. Up to 25 planes and 50 helicopters are estimated to respond per day by the end 

of a shallow-water spill. Response to an oil spill in shallow water is expected to involve over 10,000 ft 

(3,048 m) of boom within the first week and would steadily increase up to 5 million feet (~950 mi; 

~1,520 km) for use offshore and nearshore; the amount is dependent upon the location of the potentially 

impacted shoreline, environmental considerations, and agreed upon protection strategies involving the 

local potentially impacted communities.

Dispersant use must be in accordance with the Regional Response Team’s (RRT) Preapproved 

Dispersant Use Manual and with any conditions outlined within an RRT’s site-specific, dispersant 

approval given after a spill event. Consequently, dispersant use would be in accordance with the 

restrictions for specific water depths, distances from shore, and monitoring requirements. At this time, 

this manual does not give preapproval for the application of dispersant use subsea. Aerial dispersants 

would likely be applied from airplanes as a mist, which settles on the oil on the water’s surface. Along 

the Gulf Coast, surface dispersants are presently preapproved for use greater than 3 nautical miles (nmi) 

(3.5 mi; 5.6 km) from shore and in water depths greater than 33 ft (10 m), with the exception of Florida 

(U.S. Dept. of Homeland Security, CG, 2010). At this time, pursuant to a letter from the Florida 

Department of Environmental Protection dated May 5, 2011, sent to USCG, preapproval for dispersant 

use is not approved for any Florida State waters. However, the U.S. Environmental Protection Agency 

(USEPA) is presently revisiting these RRT preapprovals in light of the dispersant issues, such as subsea 

application that arose during the Macondo well blowout and spill response. In addition, revisions are 

presently being made to the RRT IV and VI’s Preapproved Dispersant Use Manuals. The USEPA issued 

a letter dated December 2, 2010, that provided interim guidance on the use of dispersants for major spills 

that are continuous and uncontrollable for periods greater than 7 days and for expedited approval of 

subsurface applications. This letter outlined the following exceptions to the current preapprovals until 

they are updated:

• dispersants may not be applied to major spills that are continuous in nature and 

uncontrollable for a period greater than 7 days; 

• additional dispersant monitoring protocols and sampling plans may be developed that 

meet the unique needs of the incident; and 

• subsurface dispersants may be approved on an incident-specific basis as requested by 

the USCG On-Scene Commander.

More robust documentation of dispersant usage may be required. This documentation would include 

daily reports that contain the products used, the specific time and locations of application, equipment used 

for each application, spotter aircraft reports, photographs, vessel data, and analytical data. In addition to 
B-10 Central Planning Area Lease Sale 247 Supplemental EIS

dispersants, controlled burns may also occur. It is estimated that 5-10 controlled burns would be 

conducted per day in suitable weather. About 500 burns in all would remove 5-10 percent of the oil.

B.2.2.7.2. Deep Water

The following are estimates for the deployment of equipment and personnel during a deepwater spill 

response. Within the first week of an oil spill originating in deep water, 50 vessels are estimated to 

respond, which would steadily increase to over 7,000 by the end of the spill. This includes about 

25 skimmers in the vicinity of the well at a time. In addition, recovered oil may be shuttle tankered to 

shore from recovery vessels. For an oil spill in deep water, over 1,000 responders are estimated to be 

deployed within the first week, which would steadily increase up to 50,000 before capping or killing the 

well within 4-5 months. Over 20,000 ft (6,096 m) of boom is estimated to be deployed within the first 

week of a deepwater spill, which would steadily increase up to 13.5 million feet (~2,257 mi; ~4,115 km) 

offshore and nearshore. The amount of boom would be dependent upon the location of the potentially 

impacted shoreline, environmental considerations, and agreed upon protection strategies involving the 

local potentially impacted communities. Up to 50 planes and 100 helicopters are estimated to respond per 

day by the end of a deepwater spill.

With the exception of special Federal management areas or designated exclusion areas, dispersants 

have been preapproved in the vicinity of a deepwater blowout (U.S. Dept. of Homeland Security, CG, 

2010). However, USEPA is presently examining these preapprovals, and restrictions are anticipated 

regarding the future use of dispersants as a result. No preapproval presently exists for the use of subsea 

dispersants, and approval must be obtained before each use of this technology. The use of subsea 

dispersants depends on the location of the blowout, as discussed in Table B-1. Aerial dispersants are 

usually applied from airplanes as a mist, which settles on the oil on the water’s surface. Major spills that 

are continuous and uncontrollable for periods greater than 7 days and the approval of subsurface 

dispersant application are presently subject to the guidance outlined in USEPA’s letter dated December 2, 

2010. This letter provides interim guidance on the use of dispersants for major spills and outlines 

exceptions to the current preapprovals until they are updated, as discussed more fully in Chapter 

B.2.2.7.1. For a deepwater spill, dispersant application may be a preferred response in the open-water 

environment to prevent oil from reaching a coastal area, in addition to mechanical response. However, 

the window of opportunity for successful dispersant application may be somewhat narrower for some 

deepwater locations depending on the physical and chemical properties of the oil, which tend to be 

somewhat heavier or more likely to emulsify than those found closer to shore. A significant reduction in 

the window of opportunity for dispersant application may render this response option ineffective. 

In addition to dispersants, controlled burns may also occur. It is estimated that 5-10 controlled burns 

would be conducted per day in suitable weather. About 500 burns in all would remove 5-10 percent of 

the oil.

B.2.2.7.3. Vessel Decontamination Stations

To avoid contaminating inland waterways, multiple vessel decontamination stations may be 

established offshore in Federal and State waters. The selected locations to conduct decontamination of 

oiled vessels will, due to the unique aspects of each spill response, be decided by the Unified Command 

during the spill response effort. Since the Unified Command includes representatives of the affected 

state(s), the states will have a prominent voice regarding whether a location in State waters will be 

acceptable.

Vessels responding to the spill and commercial and recreational vessels passing through the spill 

would anchor, awaiting inspection. If decontamination is required, work boats would use fire hoses to 

clean oil from the sides of the vessels. This could result in some oiling of otherwise uncontaminated 

waters. While these anchorage areas would be surveyed for buried pipelines that could be ruptured by 

ship anchors, they may not be surveyed adequately for benthic communities or archaeological sites. 

Therefore, some damage to benthic communities or archaeological sites may occur because of vessel 

decontamination activities associated with an oil spill (Alabama State Port Authority, 2010; State of 

Florida, Office of the Governor, 2010; Nodar, 2010; Unified Incident Command, 2010a-c; USDOC, 

NOAA, 2010a; USEPA, 2012).
Catastrophic Spill Event Analysis B-11

B.2.2.8. Severe Weather

A hurricane could accelerate biodegradation, increase the area affected by the spill, and slow or stop 

the response effort. The movement of oil would depend on the track, wind speed, and size of a hurricane. 

The official Atlantic hurricane season runs from June 1st through November 30th, with a peak of 

hurricane probability in September. In an average Atlantic season, there are 11 named storms, 

6 hurricanes, and 2 Category 3 or higher storms (USDOC, NOAA, National Weather Service, 2010). As 

a result of a hurricane, high winds and seas would mix and weather the oil from an oil spill. This can help 

accelerate the biodegradation process (USDOC, NOAA, National Weather Service, 2012). The high 

winds may distribute oil over a wider area (USDOC, NOAA, National Weather Service, 2012). 

Weather has been recognized as one of the most important factors in predicting oil-spill fate and 

behavior and in predicting the success of an oil-spill response. During an oil spill, booms, skimmers, oil 

burn, and the use of dispersants have been used to remove oil from the water surface. Adverse weather 

conditions will affect the use, performance, and effectiveness of booms and skimmers. Skimmers work 

best in calm wind; for wave heights greater than 1 m (3 ft), some skimmers will not work effectively. 

Conventional booms will not work at a current velocity of 0.5 meters per second (m/sec) (1.6 feet per 

second [ft/sec]) or greater. For oil burn, ignition cannot be carried out at wind speeds greater than 

10 m/sec (33 ft/sec). The minimum wind speed for dispersant use is about 5 m/sec (16 ft/sec), and the 

maximum wind speed for the limit of dispersant applications is about 12-14 m/sec (39-46 ft/sec) (Fingas, 

2004). 

There are tradeoffs in deciding where and when to place boom because, once deployed, boom is time 

consuming to tend and to relocate. As previously noted, booming operations are sensitive to wind, wave, 

and currents, and those sections of boom need to be tethered and secured to keep them from moving. 

Furthermore, it was discovered during the Deepwater Horizon explosion, oil spill, and response that hard 

boom often did more damage than anticipated in the marsh it was intended to protect after weather 

conditions ended up stranding the boom back into the marsh. Due to time constraints prior to a hurricane 

event, it is therefore unlikely that much effort could be expended to move large amounts of deployed 

boom, particularly given the effort that would be required to move skimming equipment to safer locations 

inland and to move large numbers of response personnel to safer areas. However, since the conditions for 

each spill response are unique, these considerations would be examined and a site-specific hurricane 

response plan developed during the actual spill response effort by the Unified Command at the beginning 

of the official hurricane season.

In addition, adverse weather would reduce ability to respond to the spill and could result in delayed 

transport and placement of the capping stack. The action of wind on the water surface will generate 

waves. Typically, waves greater than 3 ft (1 m) will prevent smaller vessels from skimming in offshore 

waters; waves greater than 5 ft (1.5 m) will prevent even the larger vessels from getting offshore to skim. 

The new high-speed skimmers under development are very promising; some skimmers have recovered oil 

with wave heights of up to 10 ft (3 m) with corresponding winds of up to 15 m/sec (49 ft/sec). 

In the event of a hurricane, vessels would evacuate the area, delaying response efforts, including the 

drilling of relief wells and any well capping or collection efforts. Severe weather, such as a hurricane, 

would delay the transport and placement of the capping stack. If a cap is applied and oil is flowed to a 

collection vessel, severe weather would cause the collection vessel to vacate its location and the oil would 

flow until the collection vessel could return and resume collection. Severe weather could also require that 

response assets be relocated inland. The response would be delayed because following the severe weather 

event the assets would need to be transported back to the staging areas. The speed with which the assets 

could be brought back to the locations would depend upon on the condition of the roads and bridges for 

traffic resumption and the amount of debris potentially blocking the roads. 

B.2.3. Phase 3—Onshore Contact

B.2.3.1. Duration

The duration of shoreline oiling is measured from initial shoreline contact until the well is capped or 

killed and the remaining oil dissipates offshore. The time needed to cap or kill a well may vary, 

depending on, among other things, the well’s water depth, its location, the well and geologic formation 

characteristics, and the associated debris. Depending on the spill’s location in relation to winds and 

currents and the well’s distance to shore, oil could reach the coast within 1 week to 1 month, based on 
B-12 Central Planning Area Lease Sale 247 Supplemental EIS

evidence from previous spills in the Gulf of Mexico OCS (e.g., it was nearly 4 weeks after the Macondo

well blowout and spill). While it is assumed that the majority of spilled oil would dissipate offshore 

within 30-60 days of stopping the flow, some oil may remain in coastal areas for some time after a spill, 

as was observed along the Gulf Coast following the Macondo well blowout and spill. 

B.2.3.1.1. Shallow Water

Due to the distance from shore, oil spilled as a result of a blowout in shallow water could reach shore 

within 1-3 weeks and could continue until the well is killed or capped and the oil dissipates offshore. 

Therefore, it is estimated that initial shoreline oiling would likely occur for 2-5 months following a 

catastrophic blowout. Some shoreline areas could be re-oiled during this timeframe dependent upon the 

weather conditions at the time of the spill as well as the persistence of the spilled oil.

B.2.3.1.2. Deep Water

Intervention is more difficult and would take longer in deeper water, in part, because at these water 

depths these intervention efforts are conducted by remotely operated vehicles. In general, most of the 

deep water in the Gulf of Mexico is located farther from shore and, therefore, it is assumed that oil would 

reach shore within 2-4 weeks. However, for the few deepwater areas that are located closer to shore, such 

as in the Mississippi Canyon Area, the amount of estimated time until shoreline contact could be the same 

as the shallow-water scenario above (1-3 weeks). The length of shoreline oiled would continue to 

increase and previously oiled areas could be re-oiled until the well is killed or capped (3-4 months) and 

the oil dissipates offshore (1-2 months). Therefore, initial shoreline oiling could occur from 3 months up 

to 6 months following a catastrophic blowout. Persistent shoreline oiling is discussed in Chapter B.2.4

(Phase 4) below.

B.2.3.2. Volume of Oil Contacting Shore

In the event of a catastrophic spill, not all of the oil spilled would contact shore. The amount of oil 

recovered and chemically or naturally dispersed would vary. For example, the following are recovery and 

cleanup rates from previous high-volume, extended spills:

• 10-40 percent of oil recovered or cleaned up (including burned, chemically dispersed, 

and skimmed); 

• 25-40 percent of oil naturally dispersed, evaporated, or dissolved; and 

• 20-65 percent of the oil remains available for offshore or inshore contact. 

In the case of the Macondo well blowout and spill, the “expected” scenario, developed by the Oil 

Budget Calculator Science and Engineering Team of The Federal Interagency Solutions Group, suggests 

that more than one quarter (29%) was naturally or chemically dispersed into Gulf waters, while burning, 

skimming, and direct recovery from the wellhead removed one quarter (25%) of the oil released. Less 

than one quarter (23%) of the total oil naturally evaporated or dissolved. The residual amount, just under 

one quarter (23%), remained in the Gulf of Mexico as a light sheen or as tarballs that have washed ashore 

or are buried in sand and other sediments (The Federal Interagency Solutions Group, 2010). 

For planning purposes, USCG estimates that 5-30 percent of oil will reach shore in the event of an 

offshore spill (33 CFR part 154, Appendix C, Table 2). Using the USCG assumptions, a catastrophic spill 

could result in a large amount of oil reaching shore. 

B.2.3.3. Length of Shoreline Contacted

While larger spill volumes increase the chance of oil reaching the coast, other factors that influence 

the length and location of shoreline contacted include the duration of the spill and the well’s location in 

relation to winds, currents, and the shoreline. Depending upon winds and currents throughout the spill 

event, already impacted areas could be re-oiled. As seen with the Deepwater Horizon oil spill, as the spill 

continued, the length of oiled shoreline at any one time increased by orders of magnitude as follows: 
Catastrophic Spill Event Analysis B-13

Duration of Spill Length of Shoreline Oiled1

30 days 0-50 miles

60 days 50-100 miles

90 days 100-1,000 miles

120 days >1,000 miles2

1 Not cumulative.

2 Length was extrapolated.

Source: USDOC, NOAA, 2011a.

B.2.3.3.1. Shallow Water

While a catastrophic spill from a shallow-water blowout is expected to be lower in volume than a 

deepwater blowout, as explained in Chapter B.2.2.3, the site would typically be closer to shore, allowing 

less time for oil to be weathered, dispersed, and recovered. This could result in a more concentrated and 

toxic oiling of the shoreline. 

B.2.3.3.2. Deep Water

While a catastrophic spill from a deepwater blowout is expected to have a much greater volume than 

a shallow-water blowout (refer to Chapter B.2.2.3), the site would typically be farther from shore, 

allowing more time for oil to be weathered, dispersed, and recovered. This could result in broader, 

patchier oiling of the shoreline.

Translocation of the spilled oil via winds and currents is also a factor in the length of shoreline 

contacted. For example, oil could enter the Loop Current and then the Gulf Stream. However, the longer 

it takes oil to travel, the more it would degrade, disperse, lose toxicity, and break into streamers and 

tarballs (USDOC, NOAA, Office of Response and Restoration, 2010d). 

B.2.3.4. Severe Weather

The official Atlantic hurricane season runs from June 1st through November 30th, with a peak in 

hurricane probability in September. In an average Atlantic season, there are 11 named storms, 

6 hurricanes, and 2 Category 3 or higher storms (USDOC, NOAA, National Weather Service, 2010). In 

the event of a hurricane, vessels would evacuate the area, delaying response efforts, including the drilling 

of relief wells. The storm surge may push oil to the coastline and inland as far as the surge reaches, or the 

storm surge may remove the majority of oil from shore, as seen in some of the previous spills reviewed.

Movement of oil during a hurricane would depend greatly on the track of the hurricane in relation to 

the slick. A hurricane’s winds rotate counter-clockwise. In general, a hurricane passing to the west of the 

slick could drive oil to the coast, while a hurricane passing to the east of the slick could drive the oil away 

from the coast.

Severe weather may distribute spilled oil over a wide area. Storm surge may carry oil into the coastal 

and inland waters and shore. Debris resulting from severe weather may be contaminated by oil. Thus, 

the responders need to take proper precautions if weathered oil is present. Weather that results in waves 

greater than 3 ft (1 m) prevents skimming in coastal waters so there is greater likelihood of contact with 

the shoreline. Severe weather would also displace or destroy shoreline boom so that oil could come into 

contact with the shoreline until responders put the boom back in place. Severe weather could require that 

assets be relocated inland. The response would be delayed because following the severe weather event 

the assets would need to be transported back to the staging areas. The speed with which the assets could 

be brought back to the locations would depend upon on the condition of the roads and bridges for traffic 

resumption and the amount of debris potentially blocking the roads. 

The USEPA, USCG, other Federal response agencies, and applicable State agencies would work 

together to address oil spills reported to the National Response Center or reported by emergency 

responders before, during, or after a hurricane occurs. Response personnel will cleanup significant spills 

and take other actions appropriate to protect public health and the environment. This response would 

cover any OCS spills that may occur as a result of the hurricane or preexisting at the time of the 
B-14 Central Planning Area Lease Sale 247 Supplemental EIS

hurricane. Response activities may be interrupted or complicated during a hurricane event. Oil from an 

ongoing OCS spill event may be washed ashore during a hurricane event; could be weathered, diluted, or 

washed farther inland; and could be mixed with other contaminants from other sources released during a 

hurricane event (e.g., heating oil or industrial chemicals). For example, onshore sources account for most 

of the oil spilled during the past few hurricane seasons that has resulted in oiled property. After 

Hurricane Sandy, some oil heating tanks flooded and caused oiling of a property owner’s own building(s). 

As such, depending on circumstances, a hurricane event during an OCS spill event could complicate and 

exacerbate spill impacts and response operations, but could also increase weathering and dilution. 

B.2.3.5. Onshore Cleanup Activities

A large-scale response effort would be expected for a catastrophic blowout. The number of vessels 

and responders would increase steadily as the spill continued. In addition to the response described in 

Chapter B.2.2.7, the following response is also estimated to occur once the spill contacts the shore.

B.2.3.5.1. Shallow Water

• There would be 5-10 staging areas established.

• Weather permitting, about 200-300 skimmers could be deployed near shore to protect 

coastlines.

B.2.3.5.2. Deep Water

• There would be 10-20 staging areas established.

• Weather permitting, about 500-600 skimmers could be deployed near shore to protect 

coastlines. As seen in Louisiana following the Macondo well blowout and spill, a 

few hundred coastal skimmers could still be in operation a few months after the well 

is capped or killed (State of Louisiana, 2010).

B.2.3.5.3. Response Considerations for Sand Beaches for Both Shallow-Water and 

Deepwater Spills

• No mechanical techniques allowed in some areas.

• Surface residence balls (SRBs), also commonly known as tarballs, and surface 

residence patties (SRPs) are subject to smearing during the day; therefore, much of 

the beach cleanup can be expected to be conducted at night, if the weather is warm. 

• There are marked differences in the sediments on the central Louisiana coast as 

compared with the Gulf beaches of Alabama, Florida, and Mississippi; therefore, no 

single technique will be universally applicable for cleaning sand beaches.

• Typically, sand sieving, shaking, and sifting beach cleaning machines will be 

utilized. The depth of cut below the sand surface can be expected to typically range 

from 0 to 12 inches (in) (0 to 30 centimeters [cm]) when using this equipment.

• It is anticipated that the responders will be instructed that no disturbance will be 

allowed below 18 in (46 cm). However, oil can be expected down to a depth of 

24-26 in (61-66 cm) below the sand surface. 

• Repetitive tilling and mixing may be used at beaches such as Grand Isle, using 

agriculture plows and discs in combination with beach cleaning machines. Sand 

washing treatment also may take place at beaches such as Grand Isle’s beach. Sand 

washing includes a sand sieve/shaker to remove debris and large oil particles and a 

heated washing system. Average daily throughput for these systems would be 
Catastrophic Spill Event Analysis B-15

290 cubic yards per day. Sand treated in this manner is typically treated by sediment 

relocation, which is where the sand is moved to an active intertidal zone

B.2.3.5.4. Response Considerations for Marshes for Both Shallow-Water and 

Deepwater Spills

• Lightly oiled marsh may be allowed to recover naturally; the oil may be allowed to 

degrade in place or to be removed by tidal or wave action. 

• Moderately or heavily oiled marsh could be cleaned by vacuuming or skimming from 

boats in conjunction with flushing to enhance oil recovery rates, low pressure 

flushing (with water comparable to marsh type), manual removal by hand or 

mechanized equipment, or vegetation cutting. 

• In some heavily oiled areas, in-situ burning may be an option if water covers the 

sediment surface. This technique is only considered when the source is contained 

due to potential re-oiling of the area. Surface washing agents are also a technique

that might be utilized.

• Bioremediation may be utilized but mostly as a secondary treatment after bulk 

removal.

B.2.3.5.5. Response Considerations for Nearshore Waters for Both Shallow-Water 

and Deepwater Spills

• Nearshore submerged oil is difficult to recover and hard to locate; vacuums and 

snares could be used.

• In the vicinity of marsh areas, skimming techniques with flushing could be utilized 

where warranted. In areas too shallow to use skimmers, oil removal could be 

accomplished using vacuum systems, in conjunction with flushing as needed. 

Booming could also be used to temporarily contain mobile slicks until they are 

recovered.

B.2.4. Phase 4—Post-Spill, Long-Term Recovery

During the final phase of a catastrophic blowout and spill, it is presumed that the well has been 

capped or killed and that cleanup activities are concluding. While it is assumed that the majority of 

spilled oil floating on surface waters would be dissipated within 30-60 days of stopping the flow, oil has 

the potential to persist in the environment long after a spill event and has been detected in sediment 

30 years after a spill dependent upon the affected environment (USDOI, FWS, 2004). On sandy beaches, 

oil can sink deep into the sediments. In tidal flats and salt marshes, oil may seep into the muddy bottoms 

(USDOI, FWS, 2010a). 

The multiple-year response required for the Deepwater Horizon explosion, oil spill, and response 

provided one example of a long-term recovery to a catastrophic spill in the Gulf of Mexico. After the 

Deepwater Horizon explosion, oil spill, and response, a multi-agency Operational Science Advisory 

Team (OSAT), under the direction of the USCG, was convened to provide information to help guide 

response activities and to provide a better understanding of the potential environmental and health risks 

after the Deepwater Horizon explosion, oil spill, and response. A summary of the OSAT findings include 

the following:

• OSAT, issued in December 2010, concluded that no recoverable Macondo oil 

remained in the water column. In addition, none of the roughly 17,000 water samples 

collected and analyzed exceeded the USEPA’s benchmarks for protection of human 

health (OSAT, 2010). 
B-16 Central Planning Area Lease Sale 247 Supplemental EIS

• OSAT-2, issued in February 2011, found that residual oil in nearshore and sandy 

shoreline areas was highly weathered, and concentrations of constituents of concern 

were well below levels of concern for human health (OSAT, 2011a). 

• The OSAT Ecotoxicity Addendum, issued in July 2011, found that, with respect to 

the indicators considered in the OSAT (2010) report, the results discussed in this 

addendum are consistent with the OSAT conclusions that “no exceedances of the 

USEPA’s dispersant benchmarks were observed” and that “since 3 August 2010 (last 

day with potentially recoverable oil on the ocean surface), <1% of water samples and 

~1% of sediment samples exceeded EPA’s aquatic life benchmarks for polycyclic 

aromatic hydrocarbons (PAH’s).” In addition, results of the toxicity tests support the 

conclusions of the OSAT report regarding the distribution of actionable (i.e., 

amenable to removal actions) oil and dispersant-related constituents (OSAT, 2011b).

• OSAT-3, finalized in early 2014, used a sophisticated scientific approach to identify 

potential discrete pockets of subsurface material. The OSAT-3 information was used 

to locate and recover potential subsurface material (British Petroleum, 2014). The 

OSAT-3 report also identified actions to be taken for reducing potential recurrence of 

oil along the northeastern shores of the Gulf of Mexico. In addition, the report 

evaluated the feasibility of each action taken to recover or remove Macondo oil and 

the net environmental benefit of employing each recovery technique recommended. 

This scientific support was provided to the Federal On-Scene Coordinator with 

shoreline segment-specific information to facilitate the operational decisionmaking 

process to recover residual Macondo oil (OSAT, 2013).

If a shoreline is oiled, the selection of the type of shoreline remediation to be used will depend on the 

following: (1) the type and amount of oil on the shore; (2) the nature of the affected coastline; (3) the 

depth of oil penetration into the sediments; (4) the accessibility and the ability of vehicles to travel along 

the shoreline; (5) the possible ecological damage of the treatment to the shoreline environment; 

(6) weather conditions; (7) the current state of the oil; and (8) jurisdictional considerations. To determine 

which cleanup method is most appropriate during a spill response, decisionmakers must assess the 

severity and nature of the injury using Shoreline Cleanup and Assessment Team survey observations. 

These onsite decisionmakers must also estimate the time it will take for an area to recover in the absence 

of cleanup (typically considering short term to be 1-3 years, medium term to be 3-5 years, and long term 

greater than 5 years) (National Response Team, 2010).

B.2.4.1. Response Considerations for Sand Beaches, Marshes, and Nearshore 

Waters for both Shallow-Water and Deepwater Spills

Once oiled, it can be expected that the shoreline response techniques employed in the initial phase of 

a response will become more extensive and continue for some time (Chapters B.2.3.5.3, B.2.3.5.4, and 

B.2.3.5.5). For example, spill response post-Macondo continued for years in some of the more heavily 

oiled areas in Louisiana and in other areas, such as Florida, Mississippi, and Alabama, which experienced 

periodic re-oiling from submerged oil mats that lie in the inshore surf zone in troughs between the sand 

bars or from buried oil onshore that resurfaces. The three types of oil residue that were identified as 

challenging or potentially damaging to the environment if removed includes the following: (1) supra-tidal 

buried oil (buried below the 6-in [15-cm] surface cleaning depth restriction near sensitive habitats); 

(2) small surface residual balls, which are oil residue left behind after beaches are cleaned; and (3) surf 

zone submerged oil mats. Active shoreline cleanup ended in June 2013 for the States of Florida, 

Mississippi, and Alabama. Active shoreline cleanup for Louisiana ended on April 15, 2014 (British 

Petroleum, 2014). However, efforts will continue to clean up any reported re-oiled shoreline in the GOM 

area as it is reported to the USCG. Although the re-oiling of some areas was anticipated to sporadically 

continue, it was determined that a better and more efficient long-term cleanup effort at this stage could be 

handled through the USCG. As of April 15, 2014, aerial reconnaissance flights were flown across 

approximately 14,000 mi (22,531 km) of shoreline during this spill response effort. Nearly 4,400 mi 

(7,081 km) were ground-surveyed, with teams identifying 1,104 mi (1,777 km) that experienced some 

level of oiling and 778 mi (1,252 km) that required some measure of cleaning (British Petroleum, 2014). 
Catastrophic Spill Event Analysis B-17

Amenity beaches were generally cleaned to depths of up to 5 ft (1.5 m), using mechanical equipment 

that sifts out residual oil and other debris from below the beach surface while returning clean sand to the 

beach. Nonrecreational beaches and environmentally sensitive areas were generally hand-cleaned to 

depths of up to 6 in (15 cm), but they were cleaned deeper if it was ecologically safe and approved by the 

USCG, stakeholders, and others. Multiple techniques were used to treat oiled marsh areas, with the goal 

of promoting natural attenuation without causing further damage. A scientific effort was launched in 

mid-2012 to locate and remove potential pockets of subsurface material in Louisiana. During this effort, 

more than 40,000 holes and pits were excavated across seven barrier islands. The vast majority either had 

no visible oil or levels so low that treatment was not appropriate or required. For example, just 3 percent 

of the more than 16,000 auger holes had oiling levels that required cleanup and less than 2 percent of the 

over 24,000 pits had heavy or moderate oiling. Assessment teams continuously surveyed the shoreline 

and recommended treatment options. More than 100,000 tons of material were collected from the 

cleanup efforts. The total consists of not only the mixed residual material, which was typically 

10-15 percent residual oil and 85-90 percent sand, shells, and water but, during the first year of 

operations, it also included other solid material such as debris and protective clothing (British Petroleum, 

2014a). Additional information regarding shoreline response considerations can be found in Chapter 

3.2.1.9. 

B.3. DESCRIPTION OF THE ENVIRONMENT AND IMPACT ANALYSIS

B.3.1. Long Duration—Large Volume Spill within the Gulf of Mexico

The following resource descriptions and impact analyses examined only the applicable portions of the 

scenario (described fully in Chapter 3 and summarized in Table B-4).

B.3.1.1. Air Quality

Phase 1—Initial Event

A catastrophic blowout close to the water surface would initially emit large amounts of methane and 

other gases into the atmosphere. If high concentrations of sulfur are present in the produced gas, 

hydrogen sulfide (H2S) could present a hazard to personnel. The natural gas H2S concentrations in the 

Gulf of Mexico OCS are generally low; however, there are areas such as the Norphlet formation in the 

northeastern Gulf of Mexico, for example, that contain levels of H2S up to 9 percent. Ignition of the 

blowout gas and subsequent fire would result in emissions of nitrogen oxides (NOx), sulfur oxides (SOx), 

carbon monoxide (CO), volatile organic compounds (VOCs), particulate matter (PM10), and fine 

particulate matter (PM2.5). The fire could also produce PAHs, which are known to be hazardous to human 

health. The pollutant concentrations would decrease with downwind distance. A large plume of black 

smoke would be visible at the source and may extend a considerable distance downwind. However, with 

increasing distance from the fire, the gaseous pollutants would undergo chemical reactions, resulting in 

the formation of fine particulate matter (PM2.5) that includes nitrates, sulfates, and organic matter. The 

PM2.5 concentrations in the plume would have the potential to temporarily degrade visibility in any 

affected Prevention of Significant Deterioration (PSD) Class I areas (i.e., National Wilderness Areas and 

National Parks) and other areas where visibility is of significant value. Organic aerosols formed 

downwind from the Macondo well blowout and spill (de Gouw et al., 2011), during which the lightest 

compounds, the VOCs, in the oil from the Macondo well blowout and spill evaporated within hours and 

during which the heavier compounds took longer to evaporate, contributing to the formation of air 

pollution particles downwind.

Phase 2—Offshore Spill

In the Gulf of Mexico, evaporation from the oil spill would result in concentrations of VOCs in the 

atmosphere, including chemicals that are classified as being hazardous. The VOC concentrations would 

occur anywhere where there is an oil slick, but they would be highest at the source of the spill because the 

rate of evaporation depends on the volume of oil present at the surface. The VOC concentrations would 

decrease with distance as the layer of oil gets thinner. The lighter compounds of VOCs would be most 

abundant in the immediate vicinity of the spill site. The heavier compounds would be emitted over a 
B-18 Central Planning Area Lease Sale 247 Supplemental EIS

longer period of time and over a larger area. Some of the compounds emitted could be hazardous to 

workers in close vicinity of the spill site. The hazard to workers can be reduced by monitoring and using 

protective gear, including respirators, as well as limiting exposure through limited work shifts, rotating 

workers out of high exposure areas, and pointing vessels into the wind. During the Macondo well 

blowout and spill, air samples collected by individual offshore workers of British Petroleum (BP), the 

Occupational Safety and Health Administration (OSHA), and USCG showed levels of benzene, toluene, 

ethylbenzene, and xylene that were mostly under detection levels. All samples had concentrations below 

the OSHA permissible exposure limits and the more stringent ACGIH (American Conference of 

Governmental Industrial Hygienists) threshold limit values (U.S. Dept. of Labor, OSHA, 2010a). 

The VOC emissions that result from the evaporation of oil contribute to the formation of particulate 

matter (PM2.5) in the atmosphere. In addition, VOCs could cause an increase in ozone levels, especially if 

the release were to occur on a hot, sunny day with sufficient concentrations of NOx present in the lower 

atmosphere. However, because of the distance of the proposed CPA lease sale area from shore, the oil 

slick would not likely have any effects on onshore ozone concentrations; however, if there were any 

effects to onshore ozone concentrations, they would likely only be temporary in nature and last at most 

the length of time of the spill duration.

It is assumed that response efforts would include hundreds of in-situ or controlled burns, which would 

remove an estimated 5-10 percent of the volume of oil spilled. This could be as much as 720,000 bbl of 

oil for a spill of 60,000 bbl per day for 90 days. In-situ burning would result in ambient concentrations of 

CO, NOx, SO2, PM10, and PM2.5 very near the site of the burn and would generate a plume of black 

smoke. The levels of PM2.5 could be a hazard to personnel working in the area, but this could be 

effectively mitigated through monitoring and relocating vessels to avoid areas of highest concentrations. 

In an experiment of an in-situ burn off Newfoundland, it was found that CO, SO2, and NO2 were 

measured only at background levels and were frequently below detection levels (Fingas et al., 1995). 

Limited amounts of formaldehyde and acetaldehyde were measured, but concentrations were close to 

background levels. Measured values of dioxins and dibenzofurans were at background levels. 

Measurements of PAH in the crude oil, the residues, and the air indicated that the PAH in the crude oil are 

largely destroyed during combustion (Fingas et al., 1995). 

While containment operations may be successful in capturing some of the escaping oil and gas, 

recovery vessels may not be capable of storing the crude oil or may not have sufficient storage capacity. 

In this case, excess oil would be burned; captured gas cannot be stored or piped to shore so it would be 

flared. For example, in the Macondo well blowout and spill, gas was flared at the rate of 100-200 million 

cubic feet per day and oil burned at the rate of 10,000-15,000 bbl per day. The estimated NOx emissions 

are about 13 tons per day. The SO2 emissions would be dependent on the sulfur content of the crude oil. 

For crude oil with a sulfur content of 0.5 percent, the estimated SO2 emissions are about 16 tons per day. 

Particulate matter in the plume would also affect visibility. Flaring or burning activities upwind of a PSD 

Class I area, e.g., the Breton National Wilderness Area, could adversely affect air quality there because of 

increased levels of SO2, PM10, and PM2.5, and because of reduced visibility. 

Phase 3—Onshore Contact

As the spill nears shore, there would be low-level concentrations of odor-causing pollutants 

associated with evaporative emissions from the oil spill. These may cause temporary eye, nose, or throat 

irritation, nausea, or headaches, but the doses are not thought to be high enough to cause long-term harm 

(USEPA, 2010a). However, responders could be exposed to levels higher than OSHA occupational 

permissible exposure levels (U.S. Department of Labor, OSHA, 2010b). During the Deepwater Horizon

explosion, oil spill, and response, USEPA took air samples at various onshore locations along the length 

of the Gulf coastline. All except three measurements of benzene were below 3 parts per billion (ppb). 

The highest level was 91 ppb. Emissions of benzene to the atmosphere result from gasoline vapors, auto 

exhaust, and chemical production and user facilities. Ambient concentrations of benzene up to and 

greater than 5 ppb have been measured in industrial areas such as Houston, Texas; in various urban areas 

during rush hour; and inside the homes of smokers (U.S. Dept. of Health and Human Services, 2007). 

The following daily median benzene air concentrations were reported in the Volatile Organic Compound 

National Ambient Database (1975-1985): remote (0.16 ppb); rural (0.47 ppb); suburban (1.8 ppb); urban 

(1.8 ppb); indoor air (1.8 ppb); and workplace air (2.1 ppb). The outdoor air data represent 300 cities in 

42 states, while the indoor air data represent 30 cities in 16 states (Shah and Singh, 1988). 
Catastrophic Spill Event Analysis B-19

During the Deepwater Horizon explosion, oil spill, and response, air samples collected by BP, 

OSHA, and USCG near shore showed levels of benzene, toluene, ethylbenzene, and xylene that were 

mostly under detection levels. Among the 28,000 personal benzene samples taken by BP, there was only 

1 sample where benzene exceeded the OSHA occupational permissible exposure limits, and 6 additional 

validated constituents were in excess of the ACGIH threshold limit value. All other sample 

concentrations were below the more stringent ACGIH threshold limit values (U.S. Department of Labor, 

OSHA, 2010a). All measured concentrations of toluene, ethylbenzene, and xylene were well within the 

OSHA occupational permissible exposure levels and ACGIH threshold limit values.

Phase 4—Post-Spill, Long-Term Recovery and Response 

There would be some residual air quality impacts after the well is capped or killed. As most of the oil 

would have been burned, evaporated, or weathered over time, air quality would return to pre-oil spill 

conditions. While impacts to air quality are expected to be localized and temporary, adverse effects that 

may occur from the exposure of humans and wildlife to air pollutants could have long-term consequences.

Overall Summary and Conclusion (Phases 1-4) 

The OCS oil- and gas-related catastrophic event could include the release of oil, condensate, or 

natural gas or chemicals used offshore or pollutants from the burning of these products. The air pollutants 

include criteria National Ambient Air Quality Standards (NAAQS) pollutants, volatile and semi-volatile 

organic compounds, H2S, and methane. If a fire was associated with the event, it would produce a broad 

array of pollutants, including all NAAQS-regulated primary pollutants, including NO2, CO, SOx, VOC, 

PM10, and PM2.5. Response activities that could impact air quality include in-situ burning, the use of 

flares to burn gas and oil, and the use of dispersants applied from aircraft. Measurements taken during an 

in-situ burning show that a major portion of compounds was consumed in the burn; therefore, pollutant 

concentrations would be expected to be within the NAAQS. In a recent analysis of air in coastal 

communities, low levels of dispersant components, which are also used in everyday household products, 

were identified. These response activities are temporary in nature and occur offshore; therefore, there are 

little expected impacts from these actions to onshore air quality. Catastrophic events involving high 

concentrations of H2S could result in deaths as well as environmental damage. Regulations and NTLs 

mandate safeguards and protective measures, which are in place, to protect workers from H2S releases. 

Other emissions of pollutants into the atmosphere from catastrophic events are not projected to have 

significant impacts on onshore air quality because of the prevailing atmospheric conditions, emissions 

height, emission rates, and the distance of these emissions from the coastline.

Overall, since loss of well-control events, blowouts, and fires are rare events and of short duration, 

potential impacts to air quality are not expected to be significant except in the rare case of a catastrophic 

event. To date, air monitoring conducted following the Macondo well blowout and spill, has not found 

any pollutants at levels expected to cause long-term harm (USEPA, 2010b). 

B.3.1.2. Water Quality

Phase 1—Initial Event

Offshore Water Quality

During the initial phase of a catastrophic blowout, water quality impacts include the disturbance of 

sediments and the release and suspension of oil and natural gas (primarily methane) into the water 

column. These potential impacts are discussed below. As this chapter deals with the immediate effects of 

a blowout that would be located at least 3 nmi (3.5 mi; 5.6 km) from shore, it is assumed that there would 

be no impacts on coastal water quality during this initial stage.

Disturbance of Sediments

A catastrophic blowout below the seafloor, outside the wellbore (Table B-1) has the potential to 

resuspend sediments and disperse potentially large quantities of bottom sediments. Some sediment could 

travel several kilometers, depending on particle size and subsea current patterns. In the deep Gulf of 
B-20 Central Planning Area Lease Sale 247 Supplemental EIS

Mexico, surficial sediments are mostly composed of silt and clay, and, if resuspended, could stay in the 

water column for several hours to days. Bottom current measurements in the deep Gulf of Mexico were 

synthesized as part of the MMS Deepwater Reanalysis study and have been measured to reach 

90 centimeters/second (cm/sec) (35.4 inches/second [in/sec]) with mean flows of 0.4-21 cm/sec 

(0.2-8.3 in/sec) (Nowlin et al., 2001). At these mean flow rates, resuspended sediment could be 

transported 0.3-18 km per day (0.2-11 mi per day). 

Sediment resuspension can lead to a temporary change in the oxidation-reduction chemistry in the 

water column, including a localized and temporal release of any formally sorbed metals, as well as 

nutrient recycling (Caetano et al., 2003; Fanning et al., 1982). Sediments also have the potential to 

become contaminated with oil components.

A subsea release also has the potential to destabilize the sediments and create slumping or larger scale 

sediment movements along depth gradients. These types of events would have the potential to move 

and/or damage any infrastructure in the affected area.

Release and Suspension of Oil into the Water Column 

A subsea release of hydrocarbons at a high flow rate has the potential to disperse and suspend plumes 

of oil droplets (chemically dispersed or otherwise) within the water column and to induce large patches of 

sheen and oil on the surface. These dispersed hydrocarbons may adsorb onto marine detritus (marine 

snow), suspended sediments, or may be mixed with drilling mud and deposited near the source. 

Mitigation efforts such as burning may introduce hydrocarbon byproducts into the marine environment, 

which would be distributed by surface currents. The acute and chronic sublethal effects of these dilute 

suspended “plumes” are not well understood and require future research efforts.

As a result of the Macondo well blowout and spill, a subsurface oil and gas plume was discovered in 

deep waters between ~1,100 and 1,300 m (3,609 and 4,265 ft) (e.g., Diercks et al., 2010) in addition to the 

surface slick. Measurable amounts of hydrocarbons (dispersed or otherwise) were detected in the 

subsurface plumes and on the seafloor in the vicinity of the release (e.g., Diercks et al., 2010; OSAT, 

2010). In the Macondo well blowout and spill subsurface plume, half-lives were estimated for petroleum 

hydrocarbons and n-alkanes on the order of 1 month and several days, respectively, indicating the impacts 

of various weathering processes (Reddy et al., 2011 and references therein). After the Ixtoc I well 

blowout and spill in 1979, which was located 50 mi (80 km) offshore in the Bay of Campeche, Mexico, 

some subsurface oil was also observed dispersed within the water column (Boehm and Fiest, 1982); 

however, the scientific investigations were limited (Reible, 2010). The water quality of offshore waters 

would be affected by the dissolved components and oil droplets that are small enough that they do not rise 

to the surface or are mixed down by surface turbulence. In the case of subsurface oil plumes, it is 

important to remember that these plumes would be affected by subsurface currents, dilution, and natural 

physical, chemical, and biological degradation processes including weathering.

Large quantities of oil put into offshore water may alter the chemistry of the sea with unforeseeable 

results. The properties and persistence of oil, including oil in the Gulf of Mexico, is further discussed in 

Chapter B.2.2.4. The VOCs, including benzene, toluene, ethylbenzene, and xylenes (also referred to as 

BTEX), are highly soluble and can have acutely toxic effects; however, VOCs are light-weight oil 

components and tend to evaporate rather than persist in the environment (Michel, 1992). Middle-weight 

organic components tend to pose the greatest risk in the environment because they are more persistent in 

the environment, are more bioavailable, and include PAHs, which have high toxicities (Michel, 1992). 

To determine the overall toxicity of PAHs in water or sediment, the contributions of every individual 

PAH compound in the petroleum mixture must be included (USEPA, 2011). This approach was used 

during the Macondo well blowout, spill and response in determining the potential risk of PAHs in both 

water and sediment to humans or animals in the environment (OSAT, 2010). Heavier components of 

crude oil tend to pose less risk of toxicity because they are not very soluble in water and therefore are less 

bioavailable.

The oil that entered the Gulf of Mexico from the Macondo well blowout and spill was a South 

Louisiana sweet crude oil (i.e., low in sulfur) (USDOC, NOAA, 2010b). This oil is less toxic than other 

crude oils in general because this oil is lower in PAHs than many other crude oils. Studies indicate that 

the oil contained approximately 3.9 percent PAHs by weight, which results in an estimated release of 

2.1 x 1010 grams of PAHs (Reddy et al., 2011; Reddy, official communication, 2012). The oil was also 

fairly high in alkanes (organic compounds containing only carbon and hydrogen and single bonds, 
Catastrophic Spill Event Analysis B-21

sometimes called paraffin or aliphatic compounds) (USDOC, NOAA, 2010b). Because alkanes are 

simple hydrocarbons, these oils are likely to undergo biodegradation more easily (USDOC, NOAA, 

2010b). 

Release of Natural Gas (Methane) into the Water Column 

A catastrophic blowout could release natural gas into the water column; the amount of gas released is 

dependent upon the water depth, the natural gas content of the formation being drilled, and its pressure. 

Methane is the primary component of natural gas. Methane may stay in the marine environment for long 

periods of time (Patin, 1999; page 237), as methane is highly soluble in seawater at the high pressures and 

cold temperatures found in deepwater environments (NRC, 2003; page 108). However, methane 

diffusing through the water column would likely be oxidized in the aerobic zone and would rarely reach 

the air-water interface (Mechalas, 1974; page 23). In addition to methane, natural gas contains smaller 

percentages of other gases such as ethane, propane, and to a much lesser degree H2S (NaturalGas.org, 

2012), which can be toxic in the environment. The majority of natural gas components including methane 

are carbon sources, and their introduction into the marine environment could result in reducing the 

dissolved oxygen levels because of microbial degradation potentially creating hypoxic or “dead” zones. 

Unfortunately, little is known about methane toxicity in the marine environment, but there is concern as to 

how methane in the water column might affect fish. Further discussion of natural gas released during the 

Macondo well blowout and spill is given in Chapter B.2.2.5.

Phase 2—Offshore Spill

Offshore Water Quality

The water offshore of the Gulf’s coasts can be divided into two regions: the continental shelf and 

slope (<1,000 ft; 305 m) and deep water (>1,000 ft; 305 m). Waters on the continental shelf and slope are 

heavily influenced by the Mississippi and Atchafalaya Rivers, the primary sources of freshwater, 

sediment, nutrients, and pollutants from a huge drainage basin encompassing 55 percent of the continental 

U.S. (Murray, 1998). Lower salinities are characteristic nearshore where freshwater from the rivers mix 

with Gulf waters. The presence or extent of a nepheloid layer, a body of suspended sediment at the sea 

bottom (Kennett, 1982, page 524), affects water quality on the shelf and slope. Deep waters east of the 

Mississippi River are affected by the Loop Current and associated warm-core (anti-cyclonic) eddies, 

which flush the area with clear, low-nutrient water (Muller-Karger et al., 2001) (Figure B-2). However, 

cold-core cyclonic eddies (counter-clockwise rotating) also form at the edge of the Loop Current and are 

associated with upwelling and nutrient-rich, high-productivity waters, although the extent of this flushing 

can vary seasonally.

While response efforts would decrease the fraction of oil remaining in Gulf waters, significant 

amounts of oil would remain. Natural processes will physically, chemically, and biologically aid the 

degradation of oil (NRC, 2003). The physical processes involved include evaporation, emulsification, 

and dissolution, while the primary chemical and biological degradation processes include photo-oxidation 

and biodegradation (i.e., microbial oxidation). Water quality would not only be impacted by the oil, gas, 

and their respective components, but also to some degree, from cleanup and mitigation efforts, such as 

from increased vessel traffic and the addition of dispersants and methanol to the marine environment. 

In the case of a catastrophic subsea blowout in deep water, it is assumed that large quantities of 

subsea dispersants would be used. The positive effect of using dispersants is that the oil, once dispersed, 

may be more available to be degraded (however, we note that contrary findings for beached oil were 

presented by Hamdan and Fulmer, 2011). The negative effect is that the oil, once dispersed, is also more 

bioavailable to have toxic effects to microorganisms as well. The toxicity of dispersed oil in the 

environment would depend on many factors, including the effectiveness of the dispersion, temperature, 

salinity, degree of weathering, type of dispersant, and degree of light penetration in the water column 

(NRC, 2005). The toxicity of dispersed oil is primarily because of the toxic components of the oil itself 

(Australian Maritime Safety Authority, 2010). 

As a result of the use of dispersants, it would be more likely for clouds or plumes of dispersed oil to 

occur near the blowout site as was seen during the Macondo well blowout and spill. Dissolved oxygen 

levels are a concern with any release of a carbon source, such as oil and natural gas, and became a 

particular concern during the Macondo well blowout and spill since dispersants were used in deep waters 
B-22 Central Planning Area Lease Sale 247 Supplemental EIS

for the first time. In areas where plumes of dispersed oil were previously found, dissolved oxygen levels 

decreased by about 20 percent from long-term average values in the GOM of ~6.9 milligrams/liter (spring 

climatological mean at 1,500-m [4,921 -ft] depth); however, scientists reported that these levels stabilized 

and were not low enough to be considered hypoxic (Joint Analysis Group, 2010; USDOC, NOAA, 

2010c). The drop in oxygen, which did not continue over time, has been attributed to microbial 

degradation of the oil.

Phase 3—Onshore Contact

Coastal Water Quality 

Water quality governs the suitability of waters for plant, animal, and human use. Water quality is 

important in the bays, estuaries, and nearshore coastal waters of the Gulf because these waters provide 

feeding, breeding, and/or nursery habitat for many invertebrates and fishes, as well as sea turtles, birds, 

and marine mammals. A catastrophic spill would significantly impact coastal water quality in the Gulf of 

Mexico. Water quality prior to the Macondo well blowout and spill was rated as fair while sediment 

quality was rated as poor (USEPA, 2008). In addition, the coastal habitat index, a rating of wetlands 

habitat loss, was also rated as poor. Both the sediment quality and the coastal habitat index affect water 

quality. 

Though response efforts would decrease the amount of oil remaining in Gulf waters and reduce the 

amount of oil contacting the coastline, significant amounts of oil would remain. Coastal water quality 

would be impacted not only by the oil, gas, and their respective components but also to some degree from 

cleanup and mitigation efforts. Increased vessel traffic, hydromodification, and the addition of 

dispersants and methanol in an effort to contain, mitigate, or clean up the oil may also tax the 

environment. 

The use of dispersants as a response tool involves a tradeoff. The purpose of chemical dispersants is 

to facilitate the movement of oil into the water column in order to encourage weathering and biological 

breakdown of the oil (i.e., biodegradation) (NRC, 2005; Australian Maritime Safety Authority, 2010). 

Thus, the tradeoff is generally considered to be oiling of the shoreline and surface of the water versus the 

water column and benthic resources (NRC, 2005). If the oil moves into the water column and is not on 

the surface of the water, it is less likely to reach sensitive shore areas (USEPA, 2010a). Since sea birds 

are often on the surface of the water or in shore areas, dispersants are also considered to be very effective 

in reducing the exposure of sea birds to oil (Australian Maritime Safety Authority, 2010). In addition to 

dispersion being enhanced by artificial processes, oil may also be dispersed from natural processes 

including both (bio)chemical and physical processes. For instance, microbial metabolism of crude oil 

results in the dispersion of oil (Bartha and Atlas, 1983), and conditions at the source of the oil/gas leak 

(e.g., orifice size and shape) may cause physical dispersion of the oil. Dispersion has both positive and 

negative effects. The positive effect is that the oil, once dispersed, is more available to be degraded. The 

negative effect is that the oil, once dispersed, is also more bioavailable to have toxic effects to 

microorganisms as well. For example, a recent study using mesocosm experiments suggested that 

dispersed oil could disrupt coastal microbial foodwebs in the northern Gulf of Mexico, reducing the flow 

of carbon to higher trophic levels (Ortmann et al., 2012). The toxicity of dispersed oil in the environment 

will depend on many factors, including the effectiveness of the dispersion, temperature, salinity, the 

degree of weathering, type of dispersant, and the degree of light penetration in the water column (NRC, 

2005). The toxicity of dispersed oil is primarily because of the toxic components of the oil itself 

(Australian Maritime Safety Authority, 2010). 

Oxygen and nutrient concentrations in coastal waters vary seasonally. The zone of hypoxia (depleted 

oxygen) on the Louisiana-Texas shelf occurs seasonally and is affected by the timing of freshwater 

discharges from the Mississippi and Atchafalaya Rivers. The hypoxic conditions continue until local 

wind-driven circulation mixes the water again. The 2010 hypoxic zone could not be linked to the 

Macondo well blowout and spill in either a positive or a negative manner (Louisiana Universities Marine 

Consortium, 2010). Nutrients from the Mississippi River nourished phytoplankton and contributed to the 

formation of the hypoxic zone.
Catastrophic Spill Event Analysis B-23

Phase 4—Post-Spill, Long-Term Recovery and Response 

The leading source of contaminants that impairs coastal water quality in the Gulf of Mexico is urban 

runoff. It can include suspended solids, heavy metals, pesticides, oil, grease, and nutrients (such as from 

lawn fertilizer). Urban runoff increases with population growth, and the Gulf Coast region has 

experienced a 109 percent population growth since 1970, with an additional expected 15 percent increase 

expected by 2020 (USDOC, NOAA, 2011b). Other pollutant source categories include (1) agricultural 

runoff, (2) municipal point sources, (3) industrial sources, (4) hydromodification (e.g., dredging), and 

(5) vessel sources (e.g., shipping, fishing, and recreational boating). The NRC (2003, Table I-4, 

page 237) estimated that, on average, approximately 26,324 bbl of oil per year entered Gulf waters from 

petrochemical and oil refinery industries in Louisiana and Texas. The Mississippi River introduced 

approximately 3,680,938 bbl per year (NRC, 2003, Table I-9, page 242) into the waters of the Gulf. 

Hydrocarbons also enter the Gulf of Mexico through natural seeps in the Gulf at a rate of approximately 

980,392 bbl per year (a range of approximately 560,224-1,400,560 bbl per year) (NRC, 2003, page 191). 

Produced water (formation water) is, by volume, the largest waste stream from the oil and gas industry 

that enters Gulf waters (e.g., Table B-3). The NRC has estimated the quantity of oil in produced water 

entering the Gulf per year to be 473,000 bbl (NRC, 2003, page 200, Table D-8).1

 These sources total 

about 5.5 MMbbl of oil per year that routinely enters Gulf of Mexico waters. In comparison, a 

catastrophic spill of 30,000-60,000 bbl per day for 90-120 days would spill a total of 2.7-7.2 MMbbl of 

oil. When added to the other sources of oil listed above, this would result in a 48- to 129-percent increase 

in the volume of oil entering the water during the year of the spill. In addition, the oil from a catastrophic 

spill will be much more concentrated in some locations than the large number of other activities that 

release oil into the Gulf of Mexico. Chapter B.2.2.4 discusses the properties and persistence of oil in the 

environment. 

Overall Summary and Conclusion (Phases 1-4) 

During Phase 1 of the catastrophic blowout scenario, impacts are not expected to coastal water 

quality. Instead, the initial impacts will include degradation of offshore water quality, disturbance and 

degradation of sediments, and the release and suspension of oil and natural gas into the water column, 

including the possible formation of plumes. Fine sediments could be transported away from the spill site.

As the spill continues during Phase 2, response efforts and natural degradation processes would 

decrease the amount of oil in the Gulf, but significant amounts of oil would remain to impact water and 

sediment quality. Water and sediment quality would not only be impacted by the oil, gas, and their 

respective components but also to some degree from cleanup and mitigation efforts. The use of 

dispersants as a response tool may make the oil more available to degradation, but it can also make the oil 

more bioavailable to have toxic effects on microorganisms as well. Furthermore, dispersed oil is more 

likely to form a plume.

Onshore contact is made during Phase 3, so coastal sediment and water quality will be significantly 

impacted during this phase despite response efforts. Response efforts may even tax the coast to some 

degree. Natural and chemical dispersion may reduce the contact of oil with the shoreline but result in 

more oil in the water column and greater bioavailability of the dispersed oil.

The long-term recovery (Phase 4) of the water and sediment quality of the Gulf will depend on the 

properties and persistence of the oil as noted in Chapter B.2.2.4. Though the spill will increase the 

amount of oil entering the Gulf of Mexico, oil regularly enters the Gulf through sources such as oil 

refineries, the Mississippi River, produced water, and natural seeps. However, oil from a spill will be 

more concentrated than the oil input from these other sources. 

 1 These numbers were generated from converting the units reported in the noted reference and do not imply any 

level of significance.
B-24 Central Planning Area Lease Sale 247 Supplemental EIS

B.3.1.3. Coastal Barrier Beaches and Associated Dunes

Phase 1—Initial Event

There would likely be no adverse impacts to coastal barrier beaches and associated dunes as a result 

of the events and the potential impact-producing factors that could occur throughout Phase 1 of a 

catastrophic spill event because these resources would not be contacted until the oil reached the shoreline.

Phase 2—Offshore Spill

There would likely be no adverse impacts to coastal barrier beaches and associated dunes as a result 

of the events and the potential impact-producing factors that could occur throughout Phase 2 of a 

catastrophic spill event because these resources would not be contacted until the oil reached the shoreline.

Phase 3—Onshore Contact

Barrier islands make up more than two-thirds of the northern Gulf of Mexico shore. Each of the 

barrier islands is either high profile or low profile, depending on the elevations and morphology of the 

island (Morton et al., 2004). The distinguishing characteristics of the high- and low-profile barriers relate 

to the width of the islands along with the continuity of the frontal dunes. Low-profile barriers are narrow 

with discontinuous frontal dunes easily overtopped by storm surge, which makes the island susceptible to 

over wash and erosion. This over wash can create channels to bring sand onto the island or into lagoons 

formed on these islands. High-profile barrier islands are generally wider than the low-profile islands and 

have continuous, vegetated, frontal dunes with elevations high enough to prevent over wash from major 

storm surge and, therefore, are less susceptible to erosion. The sand stored in these high-profile dunes 

allows the island to withstand prolonged erosion and therefore prevents breaching, which could result in 

damaging the island core. 

The effects from oil spills depend on the geographic location, volume, and rate of the spill; type of 

oil; oil-slick characteristics; oceanic conditions and season at the time of the spill; and response and 

cleanup efforts. The effects could include changes in plant species diversity that could result in changes 

in forage areas for species using microfauna as a food base (Teal and Howarth, 1984). Further detail on 

this catastrophic OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS.

As a result of a catastrophic spill, many of the barrier islands and beaches would receive varying 

degrees of oiling. The depth of oiling would be variable, based on the wave environment and sediment 

source at a particular beach head. Layering of oil and sand could occur if it was not cleaned before 

another tidal cycle. However, most areas of oiling are expected to be light, and sand removal during 

cleanup activities should be minimized. The severity of oiling dictates the appropriate cleanup method to 

be utilized (refer to Table B-4).

In areas designated as natural wilderness areas (e.g., Breton National Wildlife Refuge and Gulf 

Islands National Seashore), land managers may require little to no disruption of the natural system. In 

these environments, it is preferred to let the oil degrade naturally without aggressive and intrusive cleanup 

procedures. Manual rather than mechanized removal techniques would be used in these areas and only if 

heavy oiling has occurred. Thus, these areas may not be treated as thoroughly as other shorelines. Oil 

would remain in place longer, weathering gradually while continuing to contaminate habitat, though 

mechanical disturbance would be minimized. 

Once oil has reached the beaches and barrier islands and becomes buried or sequestered, it becomes 

difficult to treat. The oil is generally toxic to barrier beach vegetation (Ko and Day, 2004). During wave 

events when the islands and beaches erode, the oil can become remobilized and transported (Daylander 

et al., 2014). Thus, the fate of oil is not as simple as either reaching land, becoming sequestered, or being 

treated; but, it must be considered in terms of a continuing process of sequestration, remobilization, and 

transport.

For spilled oil to move onto beaches or across dunes, strong southerly winds must persist for an 

extended time prior to or immediately after the spill to elevate water levels. Strong winds, however, 

could reduce the impact severity at a landfall site by accelerating the processes of oil-slick dispersal, spill 

spreading, and oil weathering. 

The oil from the Deepwater Horizon explosion was documented by shoreline assessment teams to 

have oiled 901 km (560 mi) of beach shoreline (Michel et al., 2013). Bik et al. (2012) found that, despite 
Catastrophic Spill Event Analysis B-25 

the disappearance of visible surface oil on heavily oiled Gulf beaches impacted by the oil spill, microbial 

communities showed significant changes in community structure, with a decrease in diversity and a shift 

toward dominance by fungal taxa, particularly known hydrocarbon-degrading genera. Numerous studies 

have shown that bacterial communities present in beaches gradually degrade the oil (Urbano et al., 2013; 

Newton et al., 2013; Kostka et al., 2011). Due to the distance of beaches from deepwater blowouts and 

the combination of weathering and dispersant treatment of the oil offshore, the toxicity and quantity of the 

oil reaching shore should be greatly reduced, thereby minimizing the chances of irreversible damage to 

the impacted areas. A blowout in shallower waters near shore may have equal or greater impacts because 

of a shorter period of weathering and dispersion prior to shoreline contact, even though a smaller volume 

of spilled oil would be expected. 

Phase 4—Post-Spill, Long-Term Recovery and Response 

Oil or its components that remain in the sand after cleanup may be (1) released periodically when 

storms and high tides resuspend or flush beach sediments, (2) decomposed by biological activity, or 

(3) volatilized and dispersed. While it is assumed that the majority of spilled oil would be dissipated 

offshore within 1-2 months (depending on season and temperature) of stopping the flow, oil has the 

potential to persist in the environment long after a spill event. For example on sandy beaches, oil can sink 

deep into the sediments. As stranded oil weathers, some oil may become buried through natural beach 

processes and appear as surface residual balls (SRBs; <10 cm [4 in]) or as surface residual patties (SRPs; 

10 cm to 1 m [4 in to 3 ft]) (Table B-4). Such balls continue to provide a source of contamination with 

accompanying toxic effects. For at least 4 years after the Deepwater Horizon explosion, oil spill, and 

response, tarballs were observed washing up on Alabama beaches, and submerged oil mats were observed 

between the shoreline and the longshore sandbar (Hayworth et al., 2015). 

The cleanup impacts of a catastrophic spill could result in short-term (up to 2 years) adjustments in 

beach profiles and configurations as a result of sand removal and disturbance during cleanup operations. 

Mechanical sifting of sand to remove oil also removes wrack and organisms that are present, impacting 

community ecology of the beach. Some oil contact to lower areas of sand dunes is expected. This 

contact would not result in significant destabilization of the dunes. The long-term stressors to barrier 

beach communities caused by the physical effects and chemical toxicity of an oil spill may lead to 

decreased primary production, plant dieback, and hence, further erosion (Ko and Day, 2004). 

The protection once afforded to inland marshes by coastal barrier beaches has been greatly reduced 

because of decreased elevations and the continued effect of subsidence, sea-level rise, and saltwater 

intrusion. A catastrophic spill has the potential to contribute to this reduction through increased erosion 

as a result of plant dieback and cleanup efforts.

Overall Summary and Conclusion (Phases 1-4) 

As a result of a catastrophic spill, many of the barrier islands and beaches would receive varying 

degrees of oiling. However, most areas of oiling are expected to be lightly oiled, and sand removal 

during cleanup activities should be minimal. The long-term stressors to barrier beach communities 

caused by the physical effects and chemical toxicity of an oil spill may lead to decreased primary 

production, plant dieback, and hence, further erosion. 

B.3.1.4. Wetlands

Phase 1—Initial Event

There would likely be no adverse impacts to wetlands as a result of the events and the potential 

impact-producing factors that could occur throughout Phase 1 of a catastrophic spill event because these 

resources would not be contacted until the oil reached the shoreline.

Phase 2—Offshore Spill

There would likely be no adverse impacts to wetlands as a result of the events and the potential 

impact-producing factors that could occur throughout Phase 2 of a catastrophic spill event because these 

resources would not be contacted until the oil reached the shoreline.
B-26 Central Planning Area Lease Sale 247 Supplemental EIS

Phase 3—Onshore Contact

Coastal wetland habitats in the Gulf of Mexico occur as bands around waterways; broad expanses of 

saline, brackish, and freshwater marshes; mud and sand flats; and forested wetlands of cypress-tupelo 

swamps and bottomland hardwoods. Offshore oil spills would have a low probability of contacting and 

damaging any wetlands along the Gulf Coast, except in the case of a catastrophic event. This is because 

of the distance of the spill to the coast, the likely weathered condition of oil (through evaporation, 

dilution, and biodegradation) should it reach the coast, and because wetlands are generally protected by 

barrier islands, peninsulas, sand spits, and offshore currents. 

While a catastrophic spill from a shallow-water blowout is expected to be lower in volume than a 

deepwater blowout, a potential shallow-water site could be closer to shore, allowing less time for oil to be 

weathered, dispersed, and recovered before it impacted coastal resources. 

The oil from the Deepwater Horizon explosion was documented by shoreline assessment teams to 

have oiled 776 km (482 mi) of marsh shoreline (Michel et al., 2013). One study of the impacts of the 

Deepwater Horizon explosion, oil spill, and response to salt marshes in Louisiana estimated the area 

affected to be between 350 and 400 km2 (135 and 154 mi2), based on decreased primary production 

(Mishra et al., 2012). Further detail on the catastrophic OSRA run is contained in Appendix C of the 

CPA 235/241/247 Supplemental EIS. 

The NOAA Environmental Sensitivity Index (ESI) ranks shorelines according to their sensitivity to 

oil, the natural persistence of oil, and the expected ease of cleanup after an oil spill. These factors affect 

the impacts of oil spills in coastal and estuarine areas (USDOI, MMS, 2010). According to the ESI, the 

most sensitive shoreline types (i.e., sheltered tidal flats, vegetated low banks, salt/brackish-water marshes, 

freshwater marshes/swamps, and scrub-shrub wetlands) tend to accumulate oil and are difficult to clean, 

thus causing oil to persist in these coastal and estuarine areas (USDOI, MMS, 2010). 

In the case of catastrophic spills in the GOM, preemptive oil-response strategies would be initiated 

and include the deployment of oil booms, skimmer ships, and barge barriers to protect the beaches and 

adjacent wetlands. Boom deployment must also include plans for monitoring and maintaining the 

protective boom systems to assure that these systems are installed and functioning properly and that they 

are not damaging the wetlands they are trying to protect. In most cases, the beach face would take the 

most oil; however, in areas where the marsh is immediately adjacent to the beach face or embayments, or 

in the case of small to severe storms, marshes would be oiled. Severe weather could push oil into the tidal 

pools and back beach areas that support tidal marsh vegetation. 

The primary factors that affect vegetation responses to oil are toxicity of the oil and extent of plant 

coverage, amount of contact with and penetration of the soil, plant species affected, oiling frequency, 

season, and cleanup activities (Mendelssohn et al., 2012). Previous studies of other large spills have 

shown that, when oil has a short residence time in the marsh and it is not incorporated into the sediments, 

the marsh vegetation has a high probability of survival, even though aboveground die-off of marsh 

vegetation may occur (Lin et al., 2002). However, if re-oiling occurs after the new shoots from an initial 

oiling are produced, such that the new shoots are killed, then the marsh plants may not have enough 

stored energy to produce a second round of new shoots. Other studies noted the utilization of dispersants 

in the proper dosages results in a reduction in marsh damage from oiling (Lin and Mendelssohn, 2009). 

The works of several investigators (Webb et al., 1981 and 1985; Alexander and Webb, 1983 and 1987; 

Lytle, 1975; Delaune et al., 1979; Fischel et al., 1989) evaluated the effects of potential spills to area 

wetlands. For wetlands along the central Louisiana coast, the critical oil concentration is assumed to be 

0.025 gallons per ft2 (1.0 liter per m2

) of marsh. Concentrations less than this may cause diebacks for one 

growing season or less, depending upon the concentration and the season during which contact occurs. 

The duration and magnitude of a spill resulting from a catastrophic blowout could result in concentrations 

above this critical level and would result in longer term effects to wetland vegetation, including some 

plant mortality and loss of land. 

Due to the distance of deep water from shore, the possibility of a spill from a deepwater blowout 

reaching coastal wetlands with the toxicity to significantly impact the coastal wetlands is low because of 

the response procedures implemented during a catastrophic spill. (It is assumed that oil would reach 

shore within 2-4 weeks.) Therefore, a spill from a shallow-water blowout is more likely to contribute to 

wetland damage. However, for the few deepwater areas that are located closer to shore, such as in the 

Mississippi Canyon Area, the amount of time before shoreline contact could occur could be estimated to 

be the same as the estimate given for the shallow-water scenario, i.e., 1-3 weeks.
Catastrophic Spill Event Analysis B-27

Offshore skimming, burning, and dispersal treatments for the oil near the spill site would result in 

capture, detoxification, and dilution of the majority of oil spilled. The utilization of nearshore booming 

protection for beaches and wetlands could also help to reduce oiling of these resources, if done correctly. 

Booms deployed adjacent to marsh shorelines can be lifted by wave action onto marsh vegetation, 

resulting in plant mortality under the displaced booms. After the Deepwater Horizon explosion and oil 

spill, the use of barriers such as booms and sand berms did not work as well as planned (Martinez et al., 

2011; Jones and Davis, 2011; Zengel and Michel, 2013). The activity of oil cleanup can result in 

additional impacts on wetlands if not done properly. During the Deepwater Horizon explosion, oil spill, 

and response, aggressive onshore and marsh cleanup methods (such as the removal by mechanized 

equipment, in-situ burning, etc.) were not extensively utilized. The severity of oiling is the main factor 

that dictates the appropriate marsh cleanup method to be utilized (refer to Table B-4).

Phase 4—Post-Spill, Long-Term Recovery and Response 

Wetlands serve a number of important ecological functions. For example, Louisiana’s coastal 

wetlands support more than two-thirds of the wintering waterfowl population of the Mississippi Flyway 

(Louisiana Department of Wildlife and Fisheries, 2012). Therefore, loss of wetlands would also impact a 

significant portion of the waterfowl population. Another important ecological function of wetlands is 

their use as a nursery for estuarine-dependent species of fish and shellfish. Wetland loss would reduce the 

available nursery habitat.

The duration and magnitude of a spill resulting from a catastrophic blowout could result in high 

concentrations of oil that would result in long-term effects to wetland vegetation, including some plant 

mortality and loss of land. Silliman et al. (2012) found that after the Macondo well blowout and spill, oil 

coverage of Louisiana salt marshes was primarily concentrated on their seaward edges. Oil-driven plant 

death on the edges of these marshes more than doubled the rates of shoreline erosion, further driving 

marsh platform loss that is likely to be permanent. Eighteen months after the Macondo well blowout and 

spill, in previously oiled, noneroded areas, marsh grasses had largely recovered, and the elevated 

shoreline retreat rates observed at oiled sites had decreased to levels at reference marsh sites. Studies of 

impacted wetlands have demonstrated that wetlands can recover from the impacts of oil spills, but the 

recovery process varies from extremely slow in mangrove swamps (Burns et al., 1993 and 1994) to 

relatively rapid in grass-dominated marshes subject to in-situ burning of oil (Baustian et al., 2010). 

Land loss caused by the oiling of wetlands would add to continuing impacts of other factors, such as 

hurricanes, subsidence, saltwater intrusion, and sea-level rise. The wetlands along the Gulf Coast have 

already been severely damaged by the 2005 and 2008 hurricane seasons, leaving the mainland less 

protected. It was estimated in 2000 that coastal Louisiana would continue to lose land at a rate of 

approximately 2,672 hectares/year (10 mi2

/year) over the next 50 years. Further, it was estimated that an 

additional net loss of 132,794 hectares (512 mi2

) may occur by 2050, which is almost 10 percent of 

Louisiana’s remaining coastal wetlands (Barras et al., 2003). Barras (2006) indicated an additional 

562 km2 (217 mi2

) of land lost during the 2005 hurricane season. A catastrophic spill occurring nearshore 

would contribute further to this landloss. Following Hurricanes Katrina and Rita, another series of 

hurricanes (Gustav and Ike) made landfall along the Louisiana and Texas coasts in September 2008. 

Hurricane Gustav made landfall as a Category 2 storm near Cocodrie, Louisiana, pushing large surges of 

saline water into the fresh marshes and coastal swamps of Louisiana from Grand Isle westward. While 

Hurricane Gustav did not impact the quantity of wetlands that Hurricanes Katrina and Rita impacted, it 

did have a severe and continuing effect on the coastal barrier islands and the wetlands associated with 

backshore (back of the island) and foreshore (front of the island). While Hurricane Gustav affected the 

eastern portion of the Louisiana coast closer to Grand Isle and Houma, Hurricane Ike concentrated on 

Louisiana’s western coast. The Texas coast received the brunt of Hurricane Ike where it made landfall 

slightly east of Galveston. The storm surge heavily eroded the dune systems and significantly lowered 

the beach elevations along the eastern portion of the Texas coast near Galveston and the Bolivar 

Peninsula. The erosion and wash-over associated with Hurricane Ike’s tidal surge breeched beach ridges 

and opened the inland freshwater ponds and their associated wetlands to the sea. As a result of the four 

successive storms, the Louisiana and Texas coasts have lost protective elevations, barrier islands, and 

wetlands, and they now have the potential for transitioning to a less productive salt-marsh system in areas 

where fresh-marsh systems once existed. In addition, the loss of these protective elevations has increased 

the vulnerability of coastal wetlands to catastrophic oil-spill events.
B-28 Central Planning Area Lease Sale 247 Supplemental EIS

A poorly executed oil cleanup can result in additional impacts. Aggressive onshore and marsh 

cleanup methods (such as removal by mechanized equipment, in-situ burning, marsh cutting, and foot 

entry into the marsh for manual removal) probably would not be initiated until the oil spill has been 

stopped. Depending on the marsh remediation methods used, further impacts to the wetlands may occur 

from cleanup activities. Zengel and Michel (2013) found that, while natural recovery was the preferred 

response for the vast majority of oiled salt marsh shorelines, the most effective treatment of the 

~1 percent most heavily oiled shorelines was a treatment that involved mechanized grappling, vegetation 

raking and cutting, and scraping. Careful use of walk boards reduced the impact of the response to the 

marsh vegetation. Follow-up work showed that mechanical treatment followed by vegetation planting 

was the most effective in restoring the marsh (Zengel et al., 2014). Boat traffic in marsh areas from the 

thousands of response vessels associated with a catastrophic spill would produce an incremental increase 

in erosion rates, sediment resuspension, and turbidity (i.e., an adverse but not significant impact to coastal 

wetland and seagrass habitats).

Overall Summary and Conclusion (Phases 1-4) 

A spill from a catastrophic blowout could impact a few to several hundred square kilometers of 

wetland shoreline depending on the depth of inland penetration (Burdeau and Collins, 2010; Mishra et al., 

2012). This would vary from moderate to heavy oiling. Impacts to wetlands would vary according to the 

severity of the oiling. The duration and magnitude of the spill could result in severe oiling of wetlands in 

some areas, causing long-term effects to wetland vegetation, including some plant mortality and loss of 

land. 

B.3.1.5. Seagrass Communities

Phase 1—Initial Event

There would likely be no adverse impacts to submerged vegetation as a result of the events and the 

potential impact-producing factors that could occur throughout Phase 1 of a catastrophic spill event 

because of the likely distance from the spill event to the nearest submerged vegetation beds.

Phase 2—Offshore Spill

There would likely be no adverse impacts to submerged vegetation as a result of the events and the 

potential impact-producing factors that could occur throughout Phase 2 of a catastrophic spill because of 

the likely distance from the spill event to the nearest submerged vegetation beds.

Phase 3—Onshore Contact

According to the most recent and comprehensive data available, approximately 500,000 hectares 

(1.25 million acres; 505,857 hectares) of submerged seagrass beds are estimated to exist in exposed, 

shallow coastal waters and embayments of the northern Gulf of Mexico, and over 80 percent of this area 

is in Florida Bay and Florida coastal waters (calculated from Handley et al., 2007). Submerged 

vegetation distribution and composition depend on an interrelationship among a number of environmental 

factors that include water temperature, depth, turbidity, salinity, turbulence, and substrate suitability 

(Kemp, 1989; Onuf, 1996; Short et al., 2001). Marine seagrass beds generally occur in shallow, relatively 

clear, protected waters with predominantly sand bottoms (Short et al., 2001). Freshwater submerged 

aquatic vegetation (SAV) species occur in the low-salinity waters of coastal estuaries (Castellanos and 

Rozas, 2001). Seagrasses and freshwater SAVs provide important nursery and permanent habitat for 

sunfish, killifish, immature shrimp, crabs, drum, trout, flounder, and several other nekton species, and 

they provide a food source for species of wintering waterfowl and megaherbivores (Rozas and Odum, 

1988; Rooker et al., 1998; Castellanos and Rozas, 2001; Heck et al., 2003; Orth et al., 2006). Further 

detail on this catastrophic OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental 

EIS.

If oil comes into areas with submerged beds, increased water turbulence from waves, storms, or 

vessel traffic could break apart the surface oil sheen and disperse some oil into the water column or mix 

oil with sediments that would settle and coat an entire plant. Coating of the plat from the oil and sediment 
Catastrophic Spill Event Analysis B-29

mixture would cause reduced chlorophyll production and could lead to a decrease in vegetation (Teal and 

Howarth, 1984; Burns et al., 1994; Erftemeijer and Lewis, 2006). This coating situation also happens 

when oil is treated with dispersants because the dispersants break down the oil and it sinks into the water 

column (Thorhaug et al., 1986; Runcie et al., 2004). However, as reviewed in Runcie et al. (2004), oil 

mixed with dispersants has shown an array of effects on seagrass depending on the species and dispersant 

used. With a greater distance from shore, there is a greater chance of the oil being weathered by natural 

and mechanical processes by the time it reaches the nearshore habitat.

Depending on the species and environmental factors (e.g., temperature and wave action), seagrasses 

may exhibit minimal impacts, such as localized loss of pigmentation, from a spill; however, communities 

residing within the beds could accrue greater negative outcomes (den Hartog and Jacobs, 1980; Jackson 

et al., 1989; Kenworthy et al., 1993; Taylor et al., 2006). Community effects could range from either 

direct mortality due to smothering or indirect mortality from loss of food sources and habitat to a decrease 

in ecological performance of the entire system depending on the severity and duration of the spill event 

(Zieman et al., 1984). 

Prevention and cleanup efforts could also affect the health of submerged vegetation communities 

(Zieman et al., 1984). Many physical prevention methods such as booms, barrier berms, and diversions 

can alter hydrology, specifically changing salinity and water clarity. These changes would harm certain 

species of submerged vegetation because they are tolerant to specific salinities and light levels (Zieman 

et al., 1984; Kenworthy and Fonseca, 1996; Frazer et al., 2006). With cleanup, there is increased boat and 

human traffic in these sensitive areas that generally are protected from this degree of human disturbance 

prior to the response. Increased vessel traffic would lead to elevated water turbidity and increased 

propeller scarring. While the elevated levels of water turbidity from vessels would be short-term and the 

possible damages from propellers could be longer, both events would be localized during the prevention 

and cleanup efforts (Zieman, 1976; Dawes et al., 1997). 

Phase 4—Post-Spill, Long-Term Recovery and Response 

According to the most recent and comprehensive data available, approximately 500,000 hectares 

(1.25 million acres; 505,857 hectares) of submerged seagrass beds are estimated to exist in exposed, 

shallow coastal waters and embayments of the northern Gulf of Mexico, and over 80 percent of this area 

is in Florida Bay and Florida coastal waters (calculated from Handley et al., 2007). Submerged 

vegetation distribution and composition depend on an interrelationship among a number of environmental 

factors that include water temperature, depth, turbidity, salinity, turbulence, and substrate suitability 

(Kemp, 1989; Onuf, 1996; Short et al., 2001). Seagrasses and freshwater SAVs provide important 

nursery and permanent habitat for sunfish, killifish, immature shrimp, crabs, drum, trout, flounder, and 

several other nekton species, and they provide a food source for species of wintering waterfowl and 

megaherbivores (Rozas and Odum, 1988; Rooker et al., 1998; Castellanos and Rozas, 2001; Heck et al., 

2003; Orth et al., 2006).

A source of potential long-term impacts to submerged beds from a catastrophic spill event is the 

possibility of buried or sequestered oil becoming resuspended after a disturbance, which would have 

similar effects as the original oiling event. This could occur in the event of hurricane impacts, which 

exacerbate the problem with numerous other short-terms stresses, such as turbidity, abrasion, breakage, 

uprooting SAV and seagrasses, and the alteration of bottom profiles and hydrology. Because different 

species have different levels of sensitivity to oil, it is difficult to compare studies and extrapolate what 

variables caused the documented differences in vegetation and community health (Thorhaug et al., 1986; 

Runcie et al., 2004). In general, studied seagrasses did not show significant negative effects from an oil 

spill (den Hartog and Jacobs, 1980; Kenworthy et al., 1993; Taylor et al., 2006 and 2007). 

If bays and estuaries accrue oil, there is an assumption that there would be a decrease in seagrass 

cover and negative community impacts. Submerged vegetation serves important ecological functions. 

For example, seagrasses and freshwater SAVs provide important habitat and are a food source for a wide 

range of species in multiple life history stages (Castellanos and Rozas, 2001; Short and Coles, 2001; 

Caldwell, 2003). Therefore, loss of submerged vegetation would adversely impact these species with a 

loss of valuable habitat and food. 
B-30 Central Planning Area Lease Sale 247 Supplemental EIS

Overall Summary and Conclusion (Phases 1-4) 

Because of the likely distance of an initial catastrophic spill event to submerged vegetation 

communities, there would be no adverse impacts to submerged vegetation resulting from the initial event 

(Phase 1). Also, with regards to an offshore spill event, there would likely be no adverse impacts to 

submerged vegetation before the spill reaches shore (Phase 2). An estimated probability of oil contacting 

its coastline from the CPA example OSRA run can be found in Appendix C of the CPA 235/241/247 

Supplemental EIS (Phase 3). It is assumed when these coastlines are contacted with oil, all associated 

habitat are considered oiled. If oil comes into areas with submerged beds, oil mixed with sediments or 

with dispersants could settle and coat an entire plant and could cause reduced chlorophyll production and 

could lead to a decrease in vegetation. Depending on the species and environmental factors (e.g., 

temperature and wave action), seagrasses may exhibit minimal impacts, such as localized loss of 

pigmentation, from an oil spill; however, communities residing within the beds could accrue greater 

negative outcomes. Increased vessel traffic from cleanup efforts would lead to elevated water turbidity 

and increased propeller scarring. A source of potential long-term impacts to submerged beds from a 

catastrophic spill event is the possibility of buried or sequestered oil becoming resuspended after a 

disturbance, which would have similar effects as the original oiling event (Phase 4). While there are 

impacts on submerged vegetation from an oiling event, the probabilities of an event to occur and contact 

coastlines are generally low and any impacts that can occur depend on a variety of factors (e.g., plant 

species, oil type, current environmental conditions, etc.). In general, studied seagrasses did not show 

significant negative effects from a spill (den Hartog and Jacobs, 1980; Kenworthy et al., 1993; Taylor 

et al., 2006 and 2007).

B.3.1.6. Live Bottoms (Pinnacle Trend and Low Relief)

The Gulf of Mexico has hard bottom features upon which encrusting and epibenthic organisms attach 

on the continental shelf in water depths less than 300 m (984 ft). Live bottom features occur in the 

northeastern portion of the CPA and in the EPA. The Pinnacle Trend is located in the northeastern 

portion of the central Gulf of Mexico at the outer edge of the Mississippi-Alabama shelf between the 

Mississippi River and De Soto Canyon. Live bottom (Pinnacle Trend) features are defined in NTL 

2009-G39 as “small, isolated, low to moderate relief carbonate reefal features or outcrops of unknown 

origin or hard substrates exposed by erosion that provide area for the growth of sessile invertebrates and 

attract large numbers of fish.” Fish are attracted to outcrops that provide hard substrate for sessile 

invertebrates to attach. BOEM does not allow bottom-disturbing activities to occur within 30 m (98 ft) of 

any hard bottoms/pinnacles in 74 lease blocks in the CPA (each block is typically 3 mi x 3 mi).

Live bottom (low-relief) features are defined in NTL 2009-G39 as “seagrass communities; areas that 

contain biological assemblages consisting of sessile invertebrates living upon and attached to naturally 

occurring hard or rocky formations with rough, broken, or smooth topography; and areas where hard 

substrate and vertical relief may favor the accumulation of turtles, fishes, or other fauna.” These features 

also include the reef communities like those found on the Florida Escarpment. BOEM has stipulations to 

protect these features from impacts, including bottom-disturbing activity. This chapter discusses the hard 

substrate, as seagrasses are covered in Chapter B.3.1.5. 

Phase 1—Initial Event

A blowout from an oil well could result in a catastrophic spill event. A catastrophic blowout would 

result in released oil rapidly rising to the sea surface because all known reserves in the GOM have 

specific gravity characteristics that would preclude oil from sinking immediately after release at a 

blowout site. The oil would surface almost directly over the source location. However, if the oil is 

ejected under high pressure, micro-droplets of oil may form and become entrained in the water column 

(Boehm and Fiest, 1982; Adcroft et al., 2010). The upward movement of the oil may be reduced if 

methane mixed with the oil is dissolved into the water column, reducing the oil’s buoyancy (Adcroft 

et al., 2010). Large oil droplets would rise to the sea surface, but smaller droplets, formed by vigorous 

turbulence in the plume or the injection of dispersants, may remain neutrally buoyant in the water column, 

creating a subsurface plume (Adcroft et al., 2010; Joint Analysis Group, 2010). Dispersed oil in the water 
Catastrophic Spill Event Analysis B-31

column begins to biodegrade and may flocculate with particulate matter, promoting sinking of the 

particles. Subsea plumes or sinking oil on particulates may contact live bottom features. 

A catastrophic blowout outside the well casing and below the seafloor or at the seafloor-water 

interface could resuspend large quantities of bottom sediments and create a large crater, destroying many 

organisms within a few hundred meters of the wellhead. Some fine sediment could travel up to a few 

thousand meters before redeposition, negatively impacting a localized area of benthic communities. If a 

blowout were to occur close enough to a live bottom feature, suspended sediment may impact the 

organisms living on the feature. 

A catastrophic blowout that occurs above the seabed (at the rig, along the riser between the seafloor 

and sea surface, or through leak paths on the BOP/wellhead) would not disturb the sediment. 

The use of subsea dispersants would increase the exposure of offshore benthic habitats to dispersed 

oil droplets in the water column, as well as the chemicals used in the dispersants. The use of subsea 

dispersants is not likely to occur for seafloor blowouts outside the well casing. 

Impacts to Live Bottom Features

Impacts that occur to benthic organisms on live bottom features as a result of a blowout would depend 

on the type of blowout, distance from the blowout, relief of the biological feature, and surrounding 

physical characteristics of the environment (e.g., turbidity). The distancing of bottom-disturbing activities 

from Pinnacle and live bottom, low-relief features helps to prevent blowouts in the immediate vicinity of 

a live bottom feature or its associated biota. Much of the oil released from a blowout would rise to the sea 

surface, therefore minimizing the impact to benthic communities by direct oil exposure. However, small 

droplets of oil that are entrained in the water column for extended periods of time may migrate into areas 

that have live bottom features. Although these small oil droplets will not sink themselves, they may 

attach to suspended particles in the water column and then be deposited on the seafloor (McAuliffe et al., 

1975). The resultant long-term impacts, such as reduced recruitment success, reduced growth, and 

reduced coral or other epibenthic cover, as a result of impaired recruitment, are discussed in Phase 4 

(“Post-Spill, Long-Term Recovery and Response”). Also, if the blowout were to occur beneath the 

seabed, suspension and subsequent deposition of disturbed sediment may smother localized areas of live 

bottom communities. 

Following a catastrophic, subsurface blowout, benthic communities on a live bottoms exposed to 

large amounts of resuspended and then deposited sediments could be subject to sediment suffocation, 

exposure to resuspended toxic contaminants and to reduced light availability. Impacts to fauna found on 

hard bottoms as a result of sedimentation would vary based on species, the height to which the organism 

grows, degree of sedimentation, length of exposure, burial depth, and the organism’s ability to clear the 

sediment. Impacts may range from sublethal effects (such as reduced or slower growth, alteration in 

form, and reduced recruitment and productivity) to suffocation and death (Rogers, 1990; Fucik et al., 

1980). 

The initial blowout impact would be greatest to communities located in clear waters that experience 

heavy sedimentation. The most sensitive organisms are typically elevated above soft sediments, making 

them less likely to be buried, and it is unlikely that corals would experience heavy sedimentation because 

they are located within Live Bottom (Low Relief) Stipulation blocks that distance bottom-disturbing 

activity from the features. None of the Live Bottom Stipulation blocks were included in the current 

proposed lease sale, farther distancing oil and gas activity from live bottoms. In addition, BOEM 

conducts case-by-case reviews of plans submitted by operators to ensure that the proposed activity will 

not impact sensitive seafloor features. It is possible, however, for some live bottoms to experience some 

turbidity or sedimentation impacts from a blowout if they are downstream of a current transporting 

sediment. Corals may experience discoloration or bleaching as a result of sediment exposure, although 

recovery from such exposure may occur within 1 month (Wesseling et al., 1999). 

Initial impacts would be much less extreme in a turbid environment (Rogers, 1990). For example, the 

Pinnacle Trend community exists in a relatively turbid environment, starting just 65 km (37 mi) east of 

the mouth of the Mississippi River and trending to the northeast, and many low-relief live bottoms are 

frequently covered with a thin sand veneer that moves with waves and bottom currents, exposing and 

covering up areas with movement (Phillips et al., 1990; Gittings et al., 1992). Sediment from a blowout, 

if it occurred nearby, may have a reduced impact on these communities compared with an open-water reef 

community, as these organisms are more tolerant of suspended sediment (Gittings et al., 1992). Many of 
B-32 Central Planning Area Lease Sale 247 Supplemental EIS

the organisms that predominate in this community also grow tall enough to withstand the sedimentation 

that results from their turbid environment or have flexible structures that enable the passive removal of 

sediments (Gittings et al., 1992). Those organisms that have a lesser relief could experience 

sedimentation, abrasion, and suffocation. However, many organisms present in the lower relief, live 

bottom habitat are motile, can burrow in the sediment, or have mechanisms for dealing with turbidity and 

can be tolerant of short-term high turbidity events. For example, bivalves can reduce their filtration rates 

if the suspended sediment concentrations become elevated and can reject excess sediment through 

pseudofeces (Clarke and Wilber, 2000). Many crustaceans are able to tolerate high levels of suspended 

sediment; for example, crabs and shrimp spend a portion of their lives in estuaries and nearshore waters 

that are turbid (Wilber et al., 2005). These organisms are also able to move away from turbid areas that 

have sediment concentrations that become too high (Clarke and Wilber, 2000; Wilber et al., 2005). 

Oysters, on the other hand, are not able to move away from turbidity, but they are tolerant of this 

environmental factor as they tend to live near the mouths of rivers that deposit sediment into their habitat 

(Wilber et al., 2005). Many of these organisms can also rapidly repopulate an area affected by 

sedimentation (Fucik et al., 1980).

A portion or the entire rig may sink to the seafloor as a result of a blowout. The benthic features and 

communities upon which the rig settles would be destroyed or smothered. Encrusting organisms would 

be crushed by a rig if it lands on a live bottom feature. A settling rig may suspend sediments, which may 

smother nearby benthic communities if the sediment is redeposited on sensitive features. The habitats 

beneath the rig may be permanently lost; however, the rig itself may become an artificial reef upon which 

epibenthic organisms may settle. The surrounding benthic communities that were smothered by sediment 

would repopulate from nearby stocks through spawning recruitment and immigration if the hard substrate 

upon which they live was not physically destroyed. Destruction of a live bottom community by a sinking 

rig is highly unlikely because BOEM requires infrastructure to be distanced from live bottoms.

Phase 2—Offshore Spill

A spill from a shallow-water blowout could impact benthic communities on the continental shelf 

because of the blowout’s proximity to these habitats. The scenario (Table B-4) for a catastrophic spill on 

the continental shelf is assumed to last 2-5 months and to release 30,000 bbl per day. A total volume of 

0.9-3.0 MMbbl of South Louisiana midrange paraffinic sweet crude oil could be released, which will float 

(APIo >10). An anticipated 35,000 bbl of dispersant may be applied to the surface waters. 

A spill from a deepwater blowout could also impact shelf communities if surface oil is transported to 

these areas. The scenario (Table B-4) for a catastrophic spill in deep water is assumed to last 4-6 months 

and to release 30,000-60,000 bbl per day. A total volume of 2.7-7.2 MMbbl of South Louisiana midrange 

paraffinic sweet crude oil will be released, which will float (APIo >10). Oil properties may change as it 

passes up the well and through the water column, and it may become emulsified. An anticipated 

33,000 bbl of dispersant may be applied to the surface waters and 16,500 bbl may be applied subsea. 

Weathering and dilution of the oil will also occur as it travels from its release point. It is unlikely that a 

subsurface plume from a deepwater blowout would impact shelf communities. The oil is anticipated to 

remain in deep water and to be directed by water currents in the deep water. These currents do not 

typically transit from deep water up onto the shelf (Pond and Pickard, 1983; Inoue et al., 2008). 

Impacts to Live Bottom Features

Impacts from Surface Oil

Sensitive live bottom communities can flourish on hard bottoms in the Gulf of Mexico. The eastern 

Gulf of Mexico contains scattered, low-relief live bottoms, including areas of flat limestone shelf rock 

and the Pinnacle Trend area, located on the Mississippi Alabama continental shelf, which includes lowand high-relief features that are 60-120 m (197-394 ft) below the sea surface. The depth at which 

Pinnacles and most live bottom, low-relief features flourish below the sea surface helps to protect these 

habitats from a surface oil spill. Rough seas may mix the oil into subsurface water layers, where it may 

impact sessile biota. In general, the longer the seas are rough, the greater the amount of oil from a surface 

slick would be mixed into the water column. Silva et al. (2015) hypothesize that unusually strong wave 

action from Tropical Storm Bonnie in July 2010 may have submerged injurious amounts of surface oil 

from the Deepwater Horizon oil spill to depths of at least 75 m (246 ft) and caused the documented coral 
Catastrophic Spill Event Analysis B-33

pathologies in the Pinnacles Trend area. The submerged oil likely reached the live bottom features in 

relatively undiluted concentrations, leading to lethal and sublethal impacts. This result, though 

demonstrably possible, required a highly unusual combination of conditions in order to occur: (1) a very 

large amount of surface oil associated with a catastrophic level spill event; and (2) unusually strong winds 

and surface waves that are only expected during tropical storm-level weather. Therefore, though this 

result is noteworthy and demonstrably possible, it likely represents an extreme case that would not 

normally be expected under normal meteorological and oceanographic conditions. Under more typical 

conditions, measurable amounts of oil have been documented to mix from the surface down to a 10-m 

(33-ft) depth, although modeling exercises have indicated such oil may reach a depth of 20 m (66 ft). At 

this depth, however, the oil is found at concentrations several orders of magnitude lower than the amount 

shown to have an effect on corals and other benthic organisms (Lange, 1985; McAuliffe et al., 1975 and 

1981a; Knap et al., 1985; Scarlett et al., 2005; Hemmer et al., 2010; George-Ares and Clark, 2000). Lowrelief, live bottom habitats located in shallow coastal water may be at greater risk of surface oil mixing to 

the depth where their active growth occurs; however, because oil and gas activities currently take place 

far from the coastlines where nearshore live bottoms are located, the surface oil will be well dispersed and 

diluted by the time it reaches waters above the shallow live bottoms. Further detail on this catastrophic 

OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS. 

Impacts from Subsurface Oil

The presence of a subsurface oil plume on the continental shelf from a shallow-water blowout may 

affect benthic communities on live bottom features. A majority of oil released is expected to rise rapidly 

to the sea surface above the release point because of the specific gravity characteristics of the oil reserves 

in the GOM, thus not impacting sensitive benthic communities. If oil is ejected under high pressure, oil 

droplets may become entrained in the water column (Boehm and Fiest, 1982; Adcroft et al., 2010). The 

upward movement of the oil may be reduced if methane mixed with the oil is dissolved into the water 

column, reducing the oil’s buoyancy (Adcroft et al., 2010). Large oil droplets would rise to the sea 

surface, but smaller droplets, formed by vigorous turbulence in the plume or the injection of dispersants, 

may remain neutrally buoyant in the water column, creating a subsurface plume (Adcroft et al., 2010; 

Joint Analysis Group, 2010). Dispersed oil in the water column begins to biodegrade and may flocculate 

with particulate matter, promoting sinking of the particles. A sustained spill would continuously create 

surface slicks and possibly subsurface spill plumes. Some of the oil in the water column will become 

diluted or evaporated over time, reducing any localized transport to the seafloor (Vandermeulen, 1982). 

In addition, microbial degradation of the oil occurs in the water column so that the oil would be less toxic 

as it travels from the source (Hazen et al., 2010). However, subsurface plumes generated by highpressure dissolution of oil may come in contact with live bottom habitats, and a sustained spill may result 

in elevated exposure concentrations to benthic communities if the plume reaches them. The longer the 

spill takes to stop, the longer the exposure time and the higher the exposure concentration may be. 

Live bottom, low-relief features have a greater chance of being impacted by subsea plumes than some 

Pinnacle features because currents may sweep around the larger features, as they do with topographic 

features (Rezak et al., 1983; McGrail, 1982). The lower relief live bottoms (including low-relief features 

in the Pinnacle Trend) may fall in the path of the plume because the feature is not large enough to divert a 

current. Low-level exposures of organisms to oil from a subsea plume may result in chronic or temporary 

impacts. For example, feeding activity or reproductive ability may be reduced when coral is exposed to 

low levels of oil; however, impacts may be temporary or unable to be measured over time. Experiments 

indicated that oil exposure reduced the normal feeding activity of coral, and oiled reefs produced smaller 

gonads than unoiled reefs, resulting in reproductive stress (Lewis, 1971; Guzmán and Holst, 1993). In 

addition, photosynthesis and growth may be reduced with oil exposure, and petroleum may be 

incorporated into coral tissue (Cook and Knap, 1983; Dodge et al., 1984; Burns and Knap, 1989; Knap 

et al., 1982; Kennedy et al., 1992). Sublethal responses of other marine invertebrates on live bottoms may 

result in population level changes (Suchanek, 1993) at concentrations as low as 1-10 ppb (Hyland and 

Schneider, 1976). Sublethal impacts may include reduced feeding rates, reduced ability to detect food, 

erratic movement, ciliary inhibition, tentacle retraction, reduced movement, decreased aggression, and 

altered respiration (Scarlett et al., 2005; Suchanek, 1993). Embryonic life stages of benthic organisms 

may experience toxic effects at lower levels than adult stages (Fucik et al., 1995; Suchanek, 1993; Beiras 

and Saco-Álvarez, 2006; Byrne, 1989).
B-34 Central Planning Area Lease Sale 247 Supplemental EIS

It is unlikely that a subsurface plume from a deepwater blowout would impact live bottom shelf 

communities. The oil is anticipated to remain in deep water and be directed by water currents in the deep 

water. These currents do not typically transit from deep water up onto the shelf (Pond and Pickard, 1983; 

Inoue et al., 2008). 

Impacts from Dispersed Oil

If dispersants are used at the sea surface, oil may mix into the water column. If applied subsea, they 

can travel with currents through the water, and they may contact or settle on sensitive features. Note that, 

as indicated above, a deepwater plume would not travel onto the continental shelf, but a plume formed on 

the continental shelf could impact live bottom features. If near the source, the dispersed oil could be 

concentrated enough to harm the community. If the oil remains suspended for a longer period of time, it 

would be more dispersed and present at lower concentrations. Reports on dispersant usage on surface oil 

indicate that a majority of the dispersed oil typically remains in the top 10 m (33 ft) of the water column, 

with 60 percent of the oil in the top 2 m (6 ft) (McAuliffe et al., 1981a). However, Silva et al. (2015) 

present evidence that unusually rough seas associated with Tropical Storm Bonnie in July 2010 may have 

submerged large amounts of oil at the surface and in the upper water column following the Deepwater 

Horizon oil spill in 2005. The authors conclude that this mechanism may have led to acute exposure of 

several species of octocorals to toxic oil at two mesophotic coral communities in the Pinnacle Trend area, 

causing the documented lethal and sublethal impacts. 

Dispersant usage also reduces the oil’s ability to stick to particles in the water column, minimizing oil 

adhering to sediments and traveling to the seafloor (McAuliffe et al., 1981a). There is very little 

information on the mixing and dispersion of subsea dispersants. 

Dispersed oil reaching live bottoms in the Gulf of Mexico would be expected to occur at very low 

concentrations (<1 part per million [ppm]) (McAuliffe et al., 1981a). Such concentrations would not be 

life threatening to larval or adult stages at this depth below the sea surface based on experiments 

conducted with benthic organisms. Any dispersed oil in the water column that comes in contact with live 

bottoms may evoke short-term negative responses by the organisms (Wyers et al., 1986; Cook and Knap, 

1983; Dodge et al., 1984; Scarlett et al., 2005; Renzoni, 1973). 

The impact of dispersants on benthic organisms is dependent on the dispersant used, length of 

exposure, and the physical barriers the organism has to protect itself from the dispersant. Organisms with 

shells appear to be more tolerant of dispersants than those with only a tissue barrier (Scarlett et al., 2005). 

In addition, organisms that produce mucus, such as coral, have an elevated tolerance for oil exposure 

(Mitchell and Chet, 1975; Ducklow and Mitchell, 1979). Concentrations of 100 ppm and 1,000 ppm oil 

plus dispersant in a ratio of 4:1 were necessary for oyster and mussel fertilization and development to 

become reduced when the larvae was exposed to the mixture (Renzoni, 1973). After 48 hours of 

exposure to dispersants, the blue mussel (Mytilus edulis) died at dispersant concentrations of 250 ppm, 

although reduced feeding rates were observed at 50 ppm (Scarlett et al., 2005). The snakelocks anemone 

(Anemonia viridis), which does not have a protective shell, was much more sensitive to dispersants. It 

retracted its tentacles and failed to respond to stimuli after 48 hours of exposure to 40 ppm dispersant 

(Scarlett et al., 2005). Corals exposed to dispersed oil showed mesenterial filament extrusion, extreme 

tissue contraction, tentacle retraction, localized tissue rupture, and reduced photosynthesis (Wyers et al., 

1986; Cook and Knap, 1983). Respiratory damage to organisms does not appear to be reversible; 

however, if the exposure is short enough, nervous system damage may be reversed and organisms may 

recover (Scarlett et al., 2005). Experiments using both anemones and corals showed recovery after 

exposure to dispersants (Scarlett et al., 2005; Wyers et al., 1986). 

Concentrations used in historical experiments are generally much higher than the exposure that would 

occur in the field (Renzoni, 1973; George-Ares and Clark, 2000). Although historical experiments seem 

to indicate that the toxicity of oil increases with the addition of the dispersant, the toxicity of the oil 

actually remains the same as it was when it was not dispersed, but exposure increases due to the dispersed 

components of the oil (George-Ares and Clark, 2000). However, the increase of oil into the water column 

with the addition of dispersants is temporary, as the dispersed oil is more easily diluted with the 

surrounding water and biodegraded by bacteria (George-Ares and Clark, 2000). Therefore, concentrated 

dispersants are not anticipated to reach live bottoms, and any impacts that do occur should be sublethal 

and temporary. 
Catastrophic Spill Event Analysis B-35

Impacts from Oil Adhering to Sediments

BOEM’s policy, described in NTL 2009-G39, prevents wells from being placed immediately adjacent 

to sensitive communities. In the event of a seafloor blowout, however, some oil could be carried to live 

bottoms as a result of oil droplets adhering to suspended particles in the water column. Oiled sediment 

that settles to the seafloor may affect organisms attached to hard-bottom substrates. Impacts may include 

reduced recruitment success, reduced growth, and reduced benthic cover as a result of impaired 

recruitment. Experiments have shown that the presence of oil on available substrate for larval coral 

settlement has inhibited larval metamorphosis and larval settlement in the area. Oil exposure also 

increased the number of deformed polyps after metamorphosis occurred (Kushmaro et al., 1997). In 

addition, exposure to oiled sediment has also been shown to reduce the growth rate of clams (Dow, 1975). 

The majority of organisms exposed to sedimented oil, however, are anticipated to experience only 

low-level concentrations, particularly because oiled sediments would have been widely dispersed before 

settling to the seafloor. Many organisms on live bottoms will be able to protect themselves from low 

levels of oiled sediment that may settle out of the water column. Organisms with shells will not 

experience direct contact with the oil, and mobile organisms will be able to move away from areas where 

oiled sediment has accumulated. Coral may also be able to protect itself from low concentrations of 

sedimented oil that settles from the water column through mucus that will not only act as a barrier to 

protect coral from the oil in the water column but which also been shown to aid in the removal of oiled 

sediment on coral surfaces (Bak and Elgershuizen, 1976). In addition, because many organisms in live 

bottom habitats are tolerant of turbidity and sedimentation, slight addition of sediment to the area should 

not impact survival.

Impacts from Oil-Spill Response Activity

Oil-spill-response activity may also impact sessile benthic features. Booms anchored to the seafloor 

are sometimes used to control the movement of oil at the water surface. Boom anchors can physically 

impact sessile benthic organisms, especially when booms are moved around by waves (USDOC, NOAA, 

2010d). Vessel anchorage and decontamination stations set up during response efforts may also break or 

kill live bottoms that have unmapped locations if anchors are set on the habitat. Injury to live bottom 

habitat as a result of anchor impact may result in long-lasting damage or failed recovery. Effort should be 

made to keep vessel anchorage areas as far from sensitive benthic features as possible to minimize 

impact.

Drilling muds comprised primarily of barite may be pumped into a well to stop a blowout. If a “kill” 

is not successful, the mud (possibly tens of thousands of barrels) may be forced out of the well and 

deposited on the seafloor near the well site. Any organisms beneath the extruded drilling mud would be 

buried. Based on stipulations as described in NTL 2009-G39, a well should be far enough away from a 

Pinnacle feature to prevent extruded drilling muds from smothering sensitive benthic communities. 

However, if drilling muds were to travel far enough or high enough in the water column to contact a 

sensitive community, the fluid would smother the existing community. Burial may lead to the elimination 

of a live bottom community. 

Phase 3—Onshore Contact

There would likely be no adverse impacts to live bottom features as a result of the events and the 

potential impact-producing factors that could occur throughout Phase 3 of a catastrophic spill because the 

live bottom features are located offshore.

Phase 4—Post-Spill, Long-Term Recovery and Response

Live bottoms exposed to large amounts of resuspended sediments following a catastrophic, 

subsurface blowout could be subject to sediment suffocation, exposure to resuspended toxic 

contaminants, and reduced light penetration. The greatest impacts would occur to communities that exist 

in clear water with very low turbidity, such as the live bottoms off Florida. The consequences of a 

blowout near one of these features could be long lasting, although the occurrence of a blowout near such 

sensitive communities is unlikely because of stipulations described in NTL 2009-G39, which distances 

bottom-disturbing activity from live bottom features. In addition, BOEM conducts case-by-case reviews 
B-36 Central Planning Area Lease Sale 247 Supplemental EIS

of submitted plans and pipelines so that sensitive seafloor habitat is avoided. Impacts to a community in 

more turbid waters, such as those on the Mississippi-Alabama Shelf, would be greatly reduced, as the 

species are tolerant of suspended sediments, and recovery would occur quicker. Recovery time from 

sediment exposure would depend on the amount of sediment an organism was exposed to, if an entire 

population was demolished, and the extent of the loss. 

Impacts may also occur from low-level or long-term oil exposure. This type of exposure has the 

potential to impact live bottom communities, resulting in impaired health. Long-term impacts such as 

reduced recruitment success, reduced growth, and reduced organism cover as a result of impaired 

recruitment may occur. Recovery may be fairly rapid from brief, low-level exposures, but it could be 

much longer if acute concentrations of oil contact organisms. Recovery time would then depend on 

recruitment from outside populations that were not affected by oiling. 

Overall Summary and Conclusion (Phases 1-4) 

A catastrophic spill on the continental shelf would have a greater impact on live bottom features than 

a deepwater spill. Surface oil from a deepwater spill would be weathered and diluted by the time it 

reaches the surface waters over live bottom features (if it ever reaches them), and it would be unlikely, 

except in shallow coastal waters or during the most severe storms (e.g., Silva et al., 2015), that it would 

mix to the depth of the live bottoms in concentrations that could cause toxicity. Subsea plumes formed in 

deep water would not travel onto the continental shelf because deep-sea currents do not travel up a slope.

A catastrophic blowout and spill on the continental shelf has a greater chance to impact live bottom 

features. If a blowout on the continental shelf occurs close enough to sensitive features, the organisms 

may be smothered by settling sediment that is displaced by the blowout. The farther a feature is from the 

blowout, the lower its chance of being covered with settling sediment or sediment upon which oil 

adhered. The distancing of oil and gas activity from live bottom features helps to prevent heavy 

sedimentation, as well as features being crushed by a sinking rig.

In most cases, the impacts from oil would be sublethal. Surface oil is not expected to mix to the zone 

of active growth, and any oil components that do reach that depth would be at sublethal concentrations. 

Subsea plumes may contact the live bottom features; however, because currents tend to travel around 

instead of over large seafloor features, the Pinnacle features should be protected from subsea plumes, 

while lower relief live bottoms may be impacted. The current oil and gas activity in the GOM, however, 

is distanced from low-relief live bottoms because no live bottom, low-relief blocks have been leased with 

the current proposed lease sales. Overall impacts of dispersed oil would be similar to subsea plumes. 

Spill response activity may impact low-relief, live bottom features if they are unmarked on nautical charts 

and vessels anchor on the features, but it is doubtful that a vessel would anchor on a marked Pinnacle 

feature.

Overall, a catastrophic spill would have a fairly low probability of impacting live bottom features 

because the bottom-disturbing activities of oil and gas activities are distanced from live bottom features 

within the Live Bottom Stipulation blocks, as described in NTL 2009-G39, and because BOEM conducts 

a case-by-case review of all plans to ensure that activities do not impact these seafloor features. In 

addition, the Live Bottom Stipulation blocks have not been leased as part of these proposed lease sales, 

creating farther distance between oil and gas activities and live bottoms. Also, live bottom features are 

protected by the limited mixing depth of surface oil compared with the depth of the live bottom features, 

currents sweeping around larger features, and the weathering and dispersion of oil that would occur with 

distance from the source as it travels toward the features. Low-relief features could have impacts from a 

blowout as their relief would not divert currents. In addition, the locations of these features are not all 

known so accidental anchor impacts may result in breakage of the features and possibly destruction. 

These low-relief features, however, would be protected by the regulated distance of current oil and gas 

activities, which increases the chance of oil becoming well dispersed before it reaches the features.

B.3.1.7. Topographic Features

The Gulf of Mexico has a series of topographic features (banks or seamounts) on the continental shelf 

in water depths less than 300 m (984 ft). Topographic features are isolated areas of moderate to high 

relief that provide habitat for hard-bottom communities of high biomass and moderate diversity. These 

features support prolific algae, invertebrate, and fish communities, and they provide shelter and food for 
Catastrophic Spill Event Analysis B-37

large numbers of commercially and recreationally important fish. There are 37 named topographic 

features in the Gulf of Mexico with specific BOEM protections, including the Flower Garden Banks. 

BOEM has created “No Activity Zones” around topographic features in order to protect these habitats 

from disruption by oil and gas activities. A “No Activity Zone” is a protective perimeter drawn around 

each feature that is associated with a specific isobath (depth contour) surrounding the feature in which 

structures, drilling rigs, pipelines, and anchoring are not allowed. These “No Activity Zones” are areas 

where activity is prohibited based on BOEM’s policy. The NTL 2009-G39 recommends that drilling 

should not occur within 152 m (500 ft) of a “No Activity Zone” of a topographic feature. 

Potentially sensitive biological features (PSBFs) are features that have moderate to high relief (8 ft 

[2 m] or higher), provide hard surface for sessile invertebrates, and attract fish, but they are not located 

within the “No Activity Zone” of topographic features. These features are frequently located near 

topographic features. No bottom-disturbing activities that may cause impact to these features are 

permitted. 

Phase 1—Initial Event

A blowout from an oil well could result in a catastrophic spill event. A catastrophic blowout would 

result in released oil rapidly rising to the sea surface because all known reserves in the GOM have 

specific gravity characteristics that would preclude oil from sinking immediately after release at a 

blowout site. The oil would surface almost directly over the source location. However, if the oil is 

ejected under high pressure, micro-droplets of oil may form and become entrained in the water column 

(Boehm and Fiest, 1982; Adcroft et al., 2010). The upward movement of the oil may be reduced if 

methane mixed with the oil is dissolved into the water column, reducing the oil’s buoyancy and slowing 

its rise to the surface (Adcroft et al., 2010). Large oil droplets would rise to the sea surface, but smaller 

droplets, formed by vigorous turbulence in the plume or the injection of dispersants, may remain neutrally 

buoyant in the water column, creating a subsurface plume (Adcroft et al., 2010; Joint Analysis Group, 

2010). Dispersed oil in the water column begins to biodegrade and may flocculate with particulate 

matter, promoting sinking of the particles. Subsea plumes or sinking oil on particulates may contact 

topographic features.

A catastrophic blowout outside the well casing and below the seafloor or at the seafloor-water 

interface could resuspend large quantities of bottom sediments and create a large crater, destroying many 

organisms within a few hundred meters of the wellhead. Fine sediment could travel up to a few thousand 

meters before redeposition, negatively impacting a localized area of benthic communities. If a blowout 

were to occur near a topographic feature, suspended sediment may impact the organisms living on the 

lower levels of the topographic feature (since water currents flow around the banks rather than traveling 

uphill). 

A catastrophic blowout that occurs above the seabed (at the rig, along the riser between the seafloor 

and sea surface, or through leak paths on the BOP/wellhead) would not disturb the sediment. 

The use of subsea dispersants would increase the exposure of offshore benthic habitats to dispersed 

oil droplets in the water column, as well as the chemicals used in the dispersants. The use of subsea 

dispersants is not likely to occur for seafloor blowouts outside the well casing. 

Impacts to Topographic Features 

Impacts that occur to benthic organisms on topographic features as a result of a blowout would 

depend on the type of blowout, distance from the blowout, relief of the biological feature, and 

surrounding physical characteristics of the environment (e.g., turbidity). The NTL 2009-G39 

recommends the use of buffers to prevent blowouts in the immediate vicinity of a topographic feature or 

its associated biota. Much of the oil released from a blowout would rise to the sea surface, therefore 

minimizing the impact to benthic communities by direct oil exposure. However, small droplets of oil that 

are entrained in the water column for extended periods of time may migrate into No Activity Zones that 

surround the topographic feature. In addition, they may come in contact with PSBFs. Although these 

small oil droplets will not sink themselves, they may attach to suspended particles in the water column 

and then be deposited on the seafloor (McAuliffe et al., 1975). The resultant long-term impacts, such as 

reduced recruitment success, reduced growth, and reduced coral cover as a result of impaired recruitment, 

are discussed in Phase 4 (Post-Spill, Long-Term Recovery and Response). Also, if the blowout were to 
B-38 Central Planning Area Lease Sale 247 Supplemental EIS

occur beneath the seabed, suspension and subsequent deposition of disturbed sediment may smother 

localized areas of benthic communities, possibly including organisms within No Activity Zones or on 

PSBFs.

Benthic communities on a topographic feature or PSBF exposed to large amounts of resuspended and 

deposited sediments following a catastrophic, subsurface blowout could be subject to sediment 

suffocation, exposure to resuspended toxic contaminants, and reduced light availability. Impacts to corals 

as a result of sedimentation would vary based on coral species, the height to which the coral grows, 

degree of sedimentation, length of exposure, burial depth, and the coral’s ability to clear the sediment. 

Impacts may range from sublethal effects such as reduced growth, alteration in form, and reduced 

recruitment and productivity to slower growth or death (Rogers, 1990). Corals may also experience 

discoloration or bleaching as a result of sediment exposure, although recovery from such exposure may 

occur within 1 month (Wesseling et al., 1999). 

The initial blowout impact would be greatest to communities located in clear waters with little 

suspended sediment that experience heavy sedimentation as a result of the blowout. Reef-building corals 

are sensitive to turbidity and may be killed by heavy sedimentation (Rogers, 1990; Rice and Hunter, 

1992). However, it is unlikely that reef-building corals would experience heavy sedimentation as a result 

of a blowout because drilling activity is not allowed near sensitive organisms in the No Activity Zones 

based on the lease stipulations as described in NTL 2009-G39. The most sensitive organisms are also 

typically elevated above soft sediments, making them less likely to be buried. The lower levels of 

topographic banks and the PSBFs, which are generally small features with only a few meters of relief, 

typically experience turbid conditions. Vigorous bottom currents (often generated by storms) frequently 

resuspend bottom sediments and bathe these features in turbid waters, which results in sedimentation. As 

a result, the organisms that live in this environment near the seafloor are those adapted to frequent 

sedimentation. 

Initial impacts would be much less extreme in a turbid environment (Rogers, 1990). For example, the 

South Texas Banks exist in a relatively turbid environment (the Nepheloid Zone). They generally have 

lower relief than the farther offshore banks at the shelf edge, may have a sediment cover, and exhibit 

reduced biota. Sediment from a blowout, if it occurred nearby, may have a reduced impact on these 

communities compared with an open-water reef community, as these organisms are more tolerant of 

suspended sediment (Gittings et al., 1992). Many of the organisms that predominate in this community 

also grow tall enough to withstand the sedimentation that results from their turbid environment or have 

flexible structures that enable the passive removal of sediments (Gittings et al., 1992). 

A portion or the entire rig may sink to the seafloor as a result of a blowout. The benthic features and 

communities upon which the rig settles would be destroyed or smothered. Encrusting organisms would 

be crushed by a rig if it lands on a topographic feature or PSBF. A settling rig may suspend sediments, 

which may smother nearby benthic communities if the sediment is redeposited on sensitive features. The 

habitats beneath the rig may be permanently lost; however, the rig itself may become an artificial reef 

upon which epibenthic organisms may settle. The surrounding benthic communities that were smothered 

by sediment would repopulate from nearby stocks through spawning recruitment and immigration if the 

hard substrate upon which they live was not physically destroyed. 

Phase 2—Offshore Spill

A spill from a shallow-water blowout could impact benthic communities on the continental shelf 

because of the blowout’s proximity to these habitats. The scenario (Table B-4) for a catastrophic spill on 

the continental shelf is assumed to last 2-5 months and to release 30,000 bbl per day. A total volume of 

0.9-3.0 MMbbl of South Louisiana midrange paraffinic sweet crude oil could be released, which will float 

(APIo >10). An anticipated 35,000 bbl of dispersant may be applied to the surface waters. 

A spill from a deepwater blowout could also impact shelf communities if surface oil is transported to 

these areas. The scenario (Table B-4) for a catastrophic spill in deep water is assumed to last 4-6 months 

and to release 30,000-60,000 bbl per day. A total volume of 2.7-7.2 MMbbl of South Louisiana midrange 

paraffinic sweet crude oil will be released, which will float (APIo >10). Oil properties may change as it 

passes up the well and through the water column, and it may become emulsified. An anticipated 

33,000 bbl of dispersant may be applied to the surface waters and 16,500 bbl may be applied subsea. 

Weathering and dilution of the oil will also occur as it travels from its release point. It is unlikely that a 

subsurface plume from a deepwater blowout would impact shelf communities. The oil is anticipated to 
Catastrophic Spill Event Analysis B-39

remain in deep water and be directed by water currents in the deep water. These currents do not typically 

transit from deep water up onto the shelf (Pond and Pickard, 1983; Inoue et al., 2008). 

Impacts to Topographic Features 

Impacts from Surface Oil 

Sensitive reef communities flourish on topographic features and PSBFs in the Gulf of Mexico. Their 

depth below the sea surface helps to protect these habitats from a surface oil spill. Rough seas may mix 

the oil into subsurface water layers, where it may impact sessile biota. The longer the amount of time the 

seas are rough, the greater the amount of oil from a surface slick would be mixed into the water column. 

Measurable amounts of oil have been documented to mix from the surface down to a 10-m (33-ft) water 

depth, although modeling exercises have indicated such oil may reach a water depth of 20 m (66 ft). At 

this depth, however, the oil is found at concentrations several orders of magnitude lower than the amount 

shown to have an effect on corals (Lange, 1985; McAuliffe et al., 1975 and 1981a; Knap et al., 1985). 

None of the topographic features or PSBFs in the GOM are shallower than 10 m (33 ft), and only the 

Flower Garden Banks are shallower than 20 m (66 ft). Further detail on this catastrophic OSRA run is 

contained in Appendix C of the CPA 233/241/247 Supplemental EIS. 

Impacts from Subsurface Oil 

The presence of a subsurface oil plume on the continental shelf from a shallow-water blowout may 

affect benthic communities on topographic features and PSBFs. A majority of the oil released is expected 

to rise rapidly to the sea surface above the release point because of the specific gravity characteristics of 

the oil reserves in the GOM, thus not impacting sensitive benthic communities. If the oil is ejected under 

high pressure, oil droplets may become entrained in the water column (Boehm and Fiest, 1982; Adcroft 

et al., 2010). The upward movement of the oil may be reduced if methane mixed with the oil is dissolved 

into the water column, reducing the oil’s buoyancy and slowing its rise to the surface (Adcroft et al., 

2010). Large oil droplets would rise to the sea surface, but smaller droplets, formed by vigorous 

turbulence in the plume or the injection of dispersants, may remain neutrally buoyant in the water column, 

creating a subsurface plume (Adcroft et al., 2010; Joint Analysis Group, 2010). Dispersed oil in the water 

column begins to biodegrade and may flocculate with particulate matter, promoting sinking of the 

particles. Subsurface plumes generated by high-pressure dissolution of oil may come in contact with 

topographic features and PSBFs. A sustained spill would continuously create surface slicks and possibly 

subsurface spill plumes. Some of the oil in the water column will become diluted or evaporated over 

time, reducing any localized transport to the seafloor (Vandermeulen, 1982). In addition, microbial 

degradation of the oil occurs in the water column so that the oil would be less toxic as it travels from the 

source (Hazen et al., 2010). However, a sustained spill may result in elevated exposure concentrations to 

benthic communities if the plume reaches them. The longer the spill takes to stop, the longer the 

exposure time and higher the exposure concentration may be. 

The PSBFs have a greater chance of being impacted by subsea plumes than topographic features 

because currents tend to sweep around topographic features (Rezak et al., 1983; McGrail, 1982). The 

lower relief PSBFs may fall in the path of the plume because the feature is not large enough to divert a 

current. Low-level exposures of corals to oil from a subsea plume may result in chronic or temporary 

impacts. For example, feeding activity or reproductive ability may be reduced when coral is exposed to 

low levels of oil; however, impacts may be temporary or unable to be measured over time. Experimental 

simulations of exposure indicated that normal feeding activity of Porites porites and Madracis asperula

were reduced when exposed to 50 ppm oil (Lewis, 1971). In addition, reefs of Siderastrea siderea that 

were oiled in a spill produced smaller gonads than unoiled reefs, resulting in reproductive stress (Guzmán 

and Holst, 1993). 

Elevated concentrations of oil may be necessary to measure reduced photosynthesis or growth in 

corals. Photosynthesis of the zooxanthellae in Diplora strigosa exposed to approximately 18-20 ppm 

crude oil for 8 hours was not measurably affected, although other experiments indicate that 

photosynthesis may be impaired at higher concentrations (Cook and Knap, 1983). Measurable growth of 

Diploria strigosa exposed to oil concentrations up to 50 ppm for 6-24 hours did not show any reduced 

growth after 1 year (Dodge et al., 1984). 
B-40 Central Planning Area Lease Sale 247 Supplemental EIS

Corals exposed to subsea oil plumes may incorporate petroleum hydrocarbons into their tissue. 

Records indicate that Siderastrea siderea, Diploria strigosa, and Montastrea annularis accumulate oil 

from the water column and incorporate petroleum hydrocarbons into their tissues (Burns and Knap, 1989; 

Knap et al., 1982; Kennedy et al., 1992). Most of the petroleum hydrocarbons are incorporated into the 

coral tissues, not their mucus (Knap et al., 1982). However, hydrocarbon uptake may also modify lipid 

ratios of coral (Burns and Knap, 1989). If lipid ratios are modified, mucus synthesis may be impacted, 

adversely affecting the coral’s ability to protect itself from oil through mucus production (Burns and 

Knap, 1989).

It is unlikely that a subsurface plume from a deepwater blowout would impact shelf communities. 

The oil is anticipated to remain in deep water and be directed by water currents in the deep water. These 

currents do not typically transit from deep water up onto the shelf (Pond and Pickard, 1983; Inoue et al., 

2008). 

Impacts from Dispersed Oil 

If dispersants are used at the sea surface, oil may mix into the water column, or if applied subsea, they 

can travel with currents through the water and may contact or settle on sensitive features. Note that, as 

indicated above, a deepwater plume would not travel onto the continental shelf, but a plume formed on 

the continental shelf could impact topographic features and PSBFs. If located near the source, the 

dispersed oil could be concentrated enough to harm the community. If the oil remains suspended for a 

longer period of time, it would be more dispersed and exist at lower concentrations. Reports on 

dispersant usage on surface oil indicate that a majority of the dispersed oil remains in the top 10 m (33 ft) 

of the water column, with 60 percent of the oil in the top 2 m (6 ft) (McAuliffe et al., 1981a). Dispersant 

usage also reduces the oil’s ability to stick to particles in the water column, minimizing oil adhering to 

sediments and traveling to the seafloor (McAuliffe et al., 1981a). However, after the Deepwater Horizon

oil spill, there was the formation of a dense layer of marine snow that aggregated and collected everything 

that it came in contact with it as it fell through the water column and settled on the seafloor (Passow et al., 

2012). 

Dispersed oil reaching the topographic features and PSBFs in the Gulf of Mexico would be expected 

to be at very low concentrations (<1 ppm) (McAuliffe et al., 1981a). Such concentrations would not be 

life threatening to larval or adult stages at the depth of the features based on experiments conducted with 

coral. Any dispersed oil in the water column that comes in contact with corals may evoke short-term 

negative responses by the organisms (Wyers et al., 1986; Cook and Knap, 1983; Dodge et al., 1984). 

Reductions in feeding and photosynthesis could occur in coral exposed to dispersed oil. Short-term, 

sublethal responses of Diploria strigosa were reported after exposure to dispersed oil at a concentration of 

20 ppm for 24 hours. Although concentrations in this experiment were higher than what is anticipated for 

dispersed oil at depth, effects exhibited included mesenterial filament extrusion, extreme tissue 

contraction, tentacle retraction, and localized tissue rupture (Wyers et al., 1986). Normal behavior 

resumed within 2 hours to 4 days after exposure (Wyers et al., 1986). Diploria strigosa exposed to 

dispersed oil (20:1, oil:dispersant) showed an 85 percent reduction in zooxanthellae photosynthesis after 

8 hours of exposure to the mixture (Cook and Knap, 1983). However, the response was short term, as 

recovery occurred between 5 and 24 hours after exposure and return to clean seawater. Investigations 

1 year after Diploria strigosa was exposed to concentrations of dispersed oil between 1 and 50 ppm for 

periods between 6 and 24 hours did not reveal any impacts to growth (Dodge et al., 1984). 

Historical studies indicate dispersed oil to be more toxic to coral species than oil or dispersant alone. 

The greater toxicity may be a result of an increased number of oil droplets caused by the use of 

dispersant, resulting in greater contact area between oil, dispersant, and water (Elgershuizen and 

De Kruijf, 1976). The dispersant causes a higher water-soluble amount of oil to contact the cell 

membranes of the coral (Elgershuizen and De Kruijf, 1976). The mucus produced by coral, however, can 

protect the organism from oil. Both hard and soft corals have the ability to produce mucus, and mucus 

production has been shown to increase when corals are exposed to crude oil (Mitchell and Chet, 1975; 

Ducklow and Mitchell, 1979). Dispersed oil, however, which has very small oil droplets, does not appear 

to adhere to coral mucus, and larger untreated oil droplets may become trapped by the mucus barrier 

(Knap, 1987; Wyers et al., 1986). However, entrapment of the larger oil droplets may increase the coral’s 

long-term exposure to oil if the mucus is not shed in a timely manner (Knap, 1987; Bak and Elgershuizen, 
Catastrophic Spill Event Analysis B-41

1976). Additionally, more recent field studies, using more realistic concentrations of dispersants did not 

result in the toxicity historically reported (Yender and Michel, 2010).

Although historical studies indicated dispersed oil may be more toxic than untreated oil to corals 

during exposure experiments, untreated oil may remain in the ecosystem for long periods of time, while 

dispersed oil does not (Baca et al., 2005; Ward et al., 2003). Twenty years after an experimental oil spill 

in Panama, oil and impacts from untreated oil were still observed at oil treatment sites, but no oil or 

impacts were observed at dispersed oil or reference sites (Baca et al., 2005). Long-term recovery of the 

coral at the dispersed oil site had already occurred as reported in a 10-year monitoring update, and the site 

was not significantly different from the reference site (Ward et al., 2003).

Impacts from Oil Adhering to Sediments

BOEM’s policy, as described in NTL 2009-G39, prevents wells from being placed immediately 

adjacent to sensitive communities. In the event of a seafloor blowout, however, some oil could be carried 

to topographic features or PSBFs as a result of oil droplets adhering to suspended particles in the water 

column. Oiled sediment that settles to the seafloor may affect organisms attached to hard-bottom 

substrates. Impacts may include reduced recruitment success, reduced growth, and reduced coral cover as 

a result of impaired recruitment. Experiments have shown that the presence of oil on available substrate 

for larval coral settlement has inhibited larval metamorphosis and larval settlement in the area. An 

increase in the number of deformed polyps after metamorphosis also took place because of exposure to oil 

(Kushmaro et al., 1997). 

The majority of organisms exposed to sedimented oil are expected to experience low-level 

concentrations because as the oiled sediments settle to the seafloor they are widely distributed. Coral may 

also be able to protect itself from low concentrations of sedimented oil that settles from the water column. 

Coral mucus may not only act as a barrier to protect coral from the oil in the water column, but it has also 

been shown to aid in the removal of oiled sediment on coral surfaces (Bak and Elgershuizen, 1976). 

Coral may use a combination of increased mucus production and the action of cilia to rid themselves of 

oiled sediment (Bak and Elgershuizen, 1976). 

Impacts from Oil-Spill-Response Activity

Oil-spill-response activity may also impact sessile benthic features. Booms anchored to the seafloor 

are sometimes used to control the movement of oil at the water surface. Boom anchors can physically 

impact corals and other sessile benthic organisms, especially when booms are moved around by waves 

(USDOC, NOAA, 2010d). Vessel anchorage and decontamination stations set up during response efforts 

may also break or kill PSBFs if their location is unmapped and anchors are set on the features. Injury to 

coral reefs as a result of anchor impact may result in long-lasting damage or failed recovery (Rogers and 

Garrison, 2001). Effort should be made to keep vessel anchorage areas as far from sensitive benthic 

features as possible to minimize impact.

Drilling muds comprised primarily of barite may be pumped into a well to stop a blowout. If a “kill” 

is not successful, the mud (possibly tens of thousands of barrels) may be forced out of the well and 

deposited on the seafloor near the well site. Any organisms beneath the extruded drilling mud would be 

buried. Based on stipulations as described in NTL 2009-G39, a well should be far enough away from a 

topographic feature to prevent extruded drilling muds from smothering sensitive benthic communities. 

However, if drilling muds were to travel far enough or high enough in the water column to contact a 

sensitive community, the fluid would smother the existing community. Experiments indicate that corals 

perish faster when buried beneath drilling mud than when buried beneath carbonate sediments 

(Thompson, 1980). Burial may lead to the elimination of a live bottom community. 

Phase 3—Onshore Contact

There would likely be no adverse impacts to topographic features and PSBFs as a result of the events 

and the potential impact-producing factors that could occur throughout Phase 3 of a catastrophic spill 

because the topographic features and PSBFs are located offshore.
B-42 Central Planning Area Lease Sale 247 Supplemental EIS

Phase 4—Post-Spill, Long-Term Recovery and Response 

Topographic features and PSBFs exposed to large amounts of resuspended sediments following a 

catastrophic, subsurface blowout could be subject to sediment suffocation, exposure to resuspended toxic 

contaminants, and reduced light penetration. The greatest impacts would occur to communities that exist 

in clear water with very low turbidity. The consequences of a blowout along, directly on, or near one of 

these features could be long lasting, although the occurrence of a blowout near such sensitive 

communities is unlikely because of stipulations described in NTL 2009-G39, which prevents drilling 

activity near sensitive hard bottom habitats. Impacts to a community in more turbid waters, such as the 

South Texas Banks, would be greatly reduced, as the species on these features are tolerant of suspended 

sediments, and recovery would occur quicker. 

Impacts may also occur from low-level or long-term oil exposure. This type of exposure has the 

potential to impact reef communities, resulting in impaired health. Recovery may be fairly rapid from 

brief, low-level exposures, but it could be much longer with acute concentrations or long-term exposure 

to oil, such as in observations from Panama where untreated oil remained in the ecosystem for long 

periods of time, inhibiting coral recovery (Baca et al., 2005; Ward et al., 2003). Recovery time would 

therefore depend on recruitment from outside populations that were not affected by oiling and residence 

time of oil in an ecosystem.

Overall Summary and Conclusion (Phases 1-4) 

A catastrophic spill on the continental shelf would have a greater impact on topographic features and 

PSBFs than a deepwater spill. Surface oil from a deepwater spill would be weathered and diluted by the 

time it reaches the surface waters over topographic features and PSBFs (if it ever reaches them), and it 

would be unlikely that it would mix to the depth of active growth in concentrations that could cause 

toxicity. Subsea plumes formed in deepwater would not travel onto the continental shelf because deepsea currents do not travel up a slope.

A catastrophic blowout and spill on the continental shelf has a greater chance to impact topographic 

features and PSBFs. If the blowout occurs close enough to sensitive features, the organisms may be 

smothered by settling sediment that was displaced by the blowout. The farther the feature is from the 

blowout, the less its chance of being covered with settling sediment or sediment upon which oil adhered. 

In addition, distancing oil and gas activities from topographic features prevents the settlement of a sinking 

rig on top of a topographic feature, although it may destroy a PSBF. 

In most cases, impacts from oil would be sublethal. Surface oil is not expected to mix to the zone of 

active growth, and any oil components that do reach that depth would be in sublethal concentrations. 

Subsea plumes may contact the features; however, because currents tend to travel around, instead of over, 

topographic features, the topographic features should be protected from subsea plumes, while lower relief 

PSBFs may be impacted. Overall impacts of dispersed oil would be similar to subsea plumes. Spill 

response activity should not impact topographic features because it is unlikely that vessels would anchor 

on the features, but they could anchor on unmapped, lower relief PSBFs. 

Overall, a catastrophic spill would have a low probability of impacting topographic features because 

of the distancing requirements included in leases, as described in NTL 2009-G39, of oil and gas activities 

from topographic features, the depth of mixing of surface oil compared with the depth of the active 

growing zone, currents that sweep around the topographic features, and the weathering and dispersion of 

oil that would occur with distance from the source as it travels toward the features. The PSBFs could 

have greater impacts from a blowout as oil and gas activities are not as far distanced from them as 

topographic features; they have a lower relief than topographic features, which would not divert currents; 

and the locations of these features are not all known so accidental anchor impacts may result in breakage 

of the features and possibly destruction. The PSBFs would, however, have similar protection as for 

topographic features from surface oil.

B.3.1.8. Sargassum Communities

Pelagic Sargassum algae is a floating brown algae that occurs in all parts of the GOM throughout the 

year. It has a seasonal cycle so that its abundance greatly increases spring through fall, when it is carried 

by water currents around the south of Florida and then up the east coast (Gower and King, 2011). It 

occurs in patches, floating on and near the sea surface. Wind and water currents commonly drive it into 
Catastrophic Spill Event Analysis B-43

long lines or windrows; when conditions are turbulent, it becomes more scattered and mixed into the 

upper water column. A key to understanding impacts to Sargassum is that the algae is ubiquitous and 

occurs in scattered patches in the very top part of the water column. Sargassum also provides habitat for 

pelagic species, including fish, invertebrates, and sea turtles.

Phase 1—Initial Event

During the initial phase of a catastrophic blowout, impacts may include disturbance of sediments, 

destruction of the drilling rig, release of oil and natural gas (methane), and emergency response efforts. 

This chapter deals with the immediate effects of a blowout that would be located at least 3 nmi (3.5 mi; 

5.6 km) from shore. 

Since Sargassum is a floating pelagic (open ocean) algae, it would only be affected by impacts that 

occur in the top-most part of the water column. In deep water (≥ 300 m, 984 ft), sediment disturbed by 

the blowout would not affect Sargassum because the sediment would not reach the surface waters. 

However, in shallow water, sediment from a blowout could have minor effects on Sargassum algae in the 

immediate vicinity. The sediment would have little effect on the algae itself, producing only slight, 

temporary silting that could reduce photosynthesis. If the sediment is contaminated with oil, then the oil 

could have adverse effects on the algae. Depending on the severity of oiling, the algae could be damaged 

or destroyed; but this would only affect the algae in the local vicinity of the blowout. Sediment and oil 

would have a more acute effect on the associated invertebrate, fish, and sea turtle community that utilizes 

the habitat of the Sargassum. Impacts to these organisms may include “changes in respiration rate, 

abrasion and puncturing of structures, reduced feeding, reduced water filtration rates, smothering, delayed 

or reduced hatching of eggs, reduced larval growth or development, abnormal larval development, or 

reduced response to physical stimulus” (Anchor Environmental CA, L.P., 2003). 

Destruction of the oil drilling rig and associated equipment could have an acute effect on patches of 

Sargassum algae that happen to be caught in the structure (if it sinks) or destroyed by fuel leaks and 

possible fire on the sea surface. This could destroy local patches of Sargassum, but it would have no 

measurable effect on the Sargassum community as a whole. 

The release of oil during the initial blowout event would be expected to cover local patches of 

Sargassum algae with oil, destroying the algae and associated organisms. Methane gas may also bathe 

local patches of algae as it rises through the sea surface; it would have little effect on the algae itself but 

may poison associated organisms. The initiation of oil and gas release (as defined for this phase) at the 

site of the blowout event would affect only local patches of Sargassum, but it would have no measurable 

effect on the Sargassum community as a whole.

Emergency response activities would have minor impacts to Sargassum algae that comes in contact 

with vessels. This is mostly the simple impingement of the algae on the ships’ water intake screens, 

including water that may be pumped in fire-fighting efforts. This minor and local effect would have no 

measurable effect on the Sargassum community as a whole. 

Phase 2—Offshore Spill

During the second phase of a catastrophic blowout, the major impact of concern is the release of oil 

and methane over time. Response efforts may produce additional minor impacts to Sargassum. This 

chapter deals with the growing effects of a blowout that releases oil and methane into the offshore 

environment. 

Since Sargassum is a floating pelagic (open ocean) algae, it would be affected by impacts that occur 

in the top-most part of the water column. This makes Sargassum habitat particularly susceptible to

damage from offshore oil spills. Oceanographic processes that concentrate Sargassum into mats and rafts 

would also concentrate toxic substances. Therefore, it may be assumed that Sargassum would be found in 

areas where oil, dispersants, and other chemicals have accumulated following a catastrophic spill. Oil 

spreads on the sea surface to form extremely thin layers (0.01-0.1 micrometers) that cover large areas 

(MacDonald et al., 1996). Since Sargassum is ubiquitous in surface waters of the GOM, oil spreading on 

the sea surface can be expected to coincide with floating mats of the algae. The larger the quantity of 

spill and the longer it flows, the larger the area of sea surface it would cover. A catastrophic spill would 

cover a large area and result in impacts to a large quantity of Sargassum algae. For example, Macondo

well oil spill covered up to one-third of the northern GOM (McCrea-Strub and Pauly, 2011; USDOC, 
B-44 Central Planning Area Lease Sale 247 Supplemental EIS

NMFS, 2011a) and may have affected about one-third of the Sargassum algae in the northern GOM at the 

time.

The severity of oiling to Sargassum depends largely on physical conditions. Factors include the 

quantity of oil at a particular launch point and its physical state, distance from the source, weather 

conditions, and the possible use of dispersants. Further detail on this catastrophic OSRA run is contained 

in Appendix C of the CPA 235/241/247 Supplemental EIS. 

Obviously, more oil leads to increased oiling, but the physical state of the oil changes as it weathers, 

biodegrades, dissipates, and emulsifies over time and distance. Storms can mix oil into the water column 

(expected maximum of 10-20 m [33-66 ft]; Lange, 1985; McAuliffe et al., 1975 and 1981a; Knap et al., 

1985; Scarlett et al., 2005; Hemmer et al., 2010; George-Ares and Clark, 2000), possibly increasing its 

contact with Sargassum as it also mixes the Sargassum into the water column. However, when storms are 

not mixing the oil, they are also not mixing the Sargassum, so the Sargassum would float near the sea 

surface, just as the oil would. Convergence zones, places in the ocean where strong opposing currents 

meet, would collect both oil and Sargassum. Sea turtles, especially post-hatchlings and juveniles, use 

these areas for food and cover. Witherington et al. (2012) surveyed sea turtles in the eastern Gulf of 

Mexico and Atlantic Ocean off Florida and found that 89 percent of the turtles documented were observed 

within 1 m (3 ft) of floating Sargassum. The use of dispersants on surface oil slicks could increase the 

exposure of Sargassum to oil by promoting mixing of oil into the upper few meters of the water column. 

This also promotes the dispersion of oil, speeding its decline toward low concentrations that would be less 

toxic. Regardless, any exposure that is enough to cause visible oiling can be expected to have significant 

detrimental effects on the organisms associated with Sargassum and, likely, effects on the Sargassum

itself. Heavy oiling of Sargassum near the source of the spill would destroy the affected algae. Very

light exposure far from the oil source may have little effect.

The specific effects of oil on Sargassum depend on the severity of oiling. High to moderate levels of 

oiling would likely cause complete mortality. Low levels of exposure may result in a range of sublethal 

effects to the algae and its associated community. Powers et al. (2013) suggest that exposure to oil and/or 

dispersants can result in direct, sublethal, and indirect effects to Sargassum, resulting in death or a 

decrease in Sargassum-related ecosystem services. Sublethal responses in organisms associated with 

Sargassum may occur at concentrations as low as 1-10 ppb (Hyland and Schneider, 1976). Rogers (1990) 

documented impacts such as reduced growth, alteration in form, and reduced recruitment and 

productivity. Other sublethal impacts may include reduced feeding rates, reduced ability to detect food, 

erratic movement, ciliary inhibition, tentacle retraction, reduced movement, decreased aggression, and 

altered respiration (Scarlett et al., 2005; Suchanek, 1993). Embryonic life stages of organisms may 

experience toxicity at lower levels than the adult stages (Fucik et al., 1995; Suchanek, 1993; Beiras and 

Saco-Álvarez, 2006; Byrne, 1989). The algae itself would be less sensitive than many of its associates, 

since the algae produces oils of its own and has a waxy coating that may protect it from physical oiling. 

Response efforts aimed at removing oil from the affected area would have minor impacts on 

Sargassum algae as well. Response vessels would impinge a small amount of the algae on their 

propellers and cooling-water intakes. Cleanup processes such as booming, skimming, and in-situ burning 

would also trap and destroy patches of Sargassum; however, these activities would take place in areas of 

high concentration of surface oil, where Sargassum would likely be destroyed by oil contamination even 

if the cleanup activity were absent.

Phase 3—Onshore Contact

This third phase of a catastrophic blowout focuses on the approach of oil to the shoreline. This 

involves the possible oiling of coastal resources including beaches, wetlands, SAV and seagrasses, the 

shallow seafloor, and any resources drifting in the water column (e.g., Sargassum). Response efforts can 

produce additional serious impacts.

There would likely be little additional impact to pelagic Sargassum algae as oil approaches a 

shoreline. Since both the algae and surface oil approaching shore would be guided by the same forces 

(wind and water currents), they would likely be already traveling together, with the algae already 

contaminated. Once it is onshore, the Sargassum would die, regardless of oil contamination. Sargassum

that washes ashore has some value to the ecosystem as it provides food and shelter for some organisms as 

it decays. This value would be mostly lost if the Sargassum is oiled when it reaches shore.
Catastrophic Spill Event Analysis B-45

Phase 4—Post-Spill, Long-Term Recovery and Response 

The final phase of a catastrophic blowout is the long-term response of the ecosystem and its recovery. 

Both, the natural rate of recovery and the persistence of oil in natural habitats over time determine the 

long-term effects. Contaminants biodegrade over time, but they may become sequestered as inert forms 

(e.g., buried in sediment) until disturbed (by storms) and re-activated, producing renewed impacts.

Sargassum algae has a yearly seasonal cycle of growth and a yearly cycle of migration from the GOM 

to the western Atlantic. A catastrophic spill could affect a large portion of the annual crop of the algae. 

A large event, such as the Macondo well blowout and spill, could reduce the standing crop of Sargassum

in the GOM and subsequently in the western Atlantic if it coincided with a period when Sargassum

distribution was limited to the northwest GOM in an area known to be a nursery area. This could have a 

cascading effect down current (in the Atlantic) that would stress the cycles of other organisms that depend 

on the Sargassum habitat. However, the effect can be expected to diminish with remoteness from the 

direct impacts of the spill, i.e., the algae community itself would be most affected, with lesser effects on 

organisms that utilize the habitat as a nursery, for feeding, as shelter, or other purposes.

While a large spill event could affect a large portion of the standing crop of Sargassum, several 

factors contribute to the quick recovery of the habitat. Sargassum algae is predominately found in the 

open-ocean pelagic habitat. Once the spill event subsides, the pelagic habitat would quickly regain its 

typically very high water quality. 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 event 

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 

event may be similar to populations of any other year. Relatively small populations survive each winter, 

subsequently repopulating the habitat each year. With this pattern, recovery from the effects of a 

catastrophic event is expected within 1-2 growing seasons. 

Overall Summary and Conclusion (Phases 1-4) 

Pelagic Sargassum algae is one of the most likely habitats to be affected by a catastrophic offshore oil 

spill; however, because of its ubiquitous distribution and seasonal cycle, recovery is expected within 

1-2 years. Sargassum algae floats on and near the sea surface and occurs in patches that can be collated 

into windrows by wind and water currents. Oil from a spill offshore would accumulate in the same 

waters, making it inevitable that some patches of Sargassum would be severely affected.

The initial catastrophic event (Phase 1) could destroy Sargassum patches in the immediate vicinity of 

the accident. Impingement, fire, and the initial concentrated spillage of oil and fuels would destroy local 

patches. Sediments disturbed by the accident would only affect Sargassum if the event occurred in 

shallow waters.

The duration of the spill event (Phase 2) would have the most effect on floating Sargassum algae. 

Patches of algae within the entire coverage of the oil slick would be subject to severe damage and death. 

Algae in areas farther from the spill, receiving lower level impacts, may still suffer damage, especially the 

sensitive invertebrate and fish communities associated with the habitat. Efforts to remove the oil could 

gather Sargassum with the oil, but these algae patches would likely be destroyed by the oil anyway since 

the collection activities would occur in areas of concentrated oil.

As oil approaches shore (Phase 3), impacts to floating Sargassum algae would not increase much, as 

the algae would likely already be exposed to the oil since wind and water currents drive both the algae 

and the oil. 

The recovery of floating Sargassum algae (Phase 4) may occur within 1-2 years because the algae has 

a yearly cycle of subsidence and re-growth. As long as the nursery grounds are not completely saturated 

with oil, the pelagic habitat would quickly regain its high level of water quality after the cessation of a 

spill. Not all of the Sargassum habitat would be affected, even by a catastrophic spill; healthy algae 

would continue to grow and replenish the population. Within 1-2 years, the Sargassum algae community 

may have completely recovered from the impacts of a catastrophic spill.

B.3.1.9. Chemosynthetic Deepwater Benthic Communities

Deepwater benthic communities of the Gulf of Mexico include chemosynthetic communities and 

nonchemosynthetic communities (also termed “deepwater coral communities” [refer to Chapter 
B-46 Central Planning Area Lease Sale 247 Supplemental EIS

B.3.1.10]) that are dependent on the presence of hard substrates. Certain deepwater coral species, such as 

Lophelia pertusa, attach to exposed hard substrates and can create complex three-dimensional structural 

microhabitats, sometimes termed “framework forming” corals. These structures are often used by benthic 

invertebrates, including echinoderms (e.g., brittle stars and basket stars), sea anemones, crustaceans, and 

various other benthic megafauna. Other species of soft corals and gorgonians (commonly known as sea 

whips and sea fans) may also provide a lesser degree of usable habitat for other benthic megafauna. Deep 

water is defined here as water depths >300 m (984 ft). These types of deepwater coral communities are 

relatively rare in shallower waters. The possible impacts to deepwater coral communities from a 

catastrophic blowout depend on the location and the nature of the event. 

Phase 1—Initial Event

During the initial phase of a catastrophic blowout, impacts may include the disturbance of sediments, 

destruction of the drilling rig, release of oil and natural gas (methane), and emergency response efforts. 

This chapter deals with the immediate effects of a blowout located at least 3 nmi (3.5 mi; 5.6 km) from 

shore. 

A catastrophic blowout outside the well casing and below the seafloor or at the seafloor-water 

interface could resuspend large quantities of bottom sediments and create a large crater, destroying many 

organisms within a few hundred meters of the wellhead. Some fine sediment could travel up to a few 

thousand meters before redeposition, negatively impacting a localized area of benthic communities. If a 

blowout were to occur close enough to a chemosynthetic community, suspended sediment may impact the 

organisms. Restrictions described in NTL 2009-G40 require drilling to be sufficiently distanced from 

possible chemosynthetic communities. During a blowout, sediment may become contaminated with oil 

and subsequently deposit that oil down-current from the source. The highest concentrations of 

contamination would be nearest the well, and concentrations would diminish with distance. A 

catastrophic blowout that occurs above the seabed (at the rig, along the riser between the seafloor and sea 

surface, or through leak paths on the BOP/wellhead) would not disturb the sediment. 

Destruction of the oil drilling rig and associated equipment could have an acute effect on any 

chemosynthetic communities caught under the direct impact of the equipment when it falls to the seafloor. 

However, the distancing requirements described in NTL 2009-G40 reduce the probability that a rig would 

settle directly on sensitive habitat.

A catastrophic blowout would likely result in released oil rapidly rising to the sea surface because 

typical reserves in the GOM have specific gravity characteristics that are much lighter than water (refer to 

Chapter 3.2.1.3 of this Supplemental EIS; Environment Canada, 2011; Trudel et al., 2001). The oil 

would surface almost directly over the source location. Oil floating to the sea surface would be 

effectively removed from affecting chemosynthetic communities on the seafloor. Even oil treated with 

chemical dispersants on the sea surface would not be expected to have widespread impacts to deepwater 

communities. Reports on dispersant usage on surface oil indicate that a majority of the dispersed oil 

remains in the top 10 m (33 ft) of the water column, with 60 percent of the oil in the top 2 m (6 ft) 

(McAuliffe et al., 1981a; Lewis and Aurand, 1997). Lubchenco et al. (2010) reports that chemically 

dispersed surface oil from the Macondo well blowout and oil spill remained in the top 6 m (20 ft) of the 

water column where it mixed with surrounding waters and biodegraded. However, if the oil is ejected 

under high pressure, micro-droplets of oil may form and become entrained in the water column (Boehm 

and Fiest, 1982; Adcroft et al., 2010). Upward movement of oil may also be reduced if methane mixed 

with the oil is dissolved into the water column, reducing the buoyancy of the oil/gas stream (Adcroft 

et al., 2010). Large oil droplets would rise to the sea surface, but smaller droplets, formed by vigorous 

turbulence in the plume or the injection of dispersants, may remain neutrally buoyant in the water column, 

creating a subsurface plume (Adcroft et al., 2010; Joint Analysis Group, 2010a). The likelihood that a 

chemosynthetic community would be affected by the initial stage of a catastrophic event would be 

reduced with adherence to the NTL 2009-G40 requirements distancing drilling activities from sensitive 

habitats because released oil would rise rapidly to a level above the habitat and because surface oil would 

not mix to the depths of the chemosynthetic communities. The required separation distance would also 

allow for a subsea plume to mix with the surrounding water and become diluted before it reached a 

deepwater community.
Catastrophic Spill Event Analysis B-47

Phase 2—Offshore Spill

During the second phase of a catastrophic blowout, the major impact of concern is the release of oil 

and methane over time. Response efforts may produce additional impacts. This chapter deals with the 

growing effects of a blowout that releases oil and methane into the offshore environment.

Oil and chemical spills that originate at the sea surface are not considered to be a potential source of 

measurable impacts on chemosynthetic communities because of the water depths at which these 

communities are located. Oil spills at the surface would tend not to sink, and the risk of weathered 

components of a surface slick reaching the benthos in any measurable concentration would be very small. 

Large concentrations of surface oil are unlikely to physically mix to the depths of deepwater communities 

under natural conditions (Lange, 1985; McAuliffe et al., 1975 and 1981a; Tkalich and Chan, 2002).

A catastrophic spill resulting from a loss of well control in deep water has the potential to impact 

offshore benthic communities, particularly if the use of chemical dispersants increases exposure time by 

creating subsurface plumes. Sublethal effects are possible for communities that receive a lower level of 

impact. Examples of these effects could include temporary reductions in feeding, expenditure of energy 

to remove the oil, loss of gametes and reproductive delays, and loss of tissue mass.

Oil plumes that remain in the water column for longer periods would disperse and decay, having only 

a minimal effect. Depending on how long it remains in the water column, oil may be thoroughly 

degraded by biological action before contacting the seafloor. Water currents can carry a plume to contact 

the seafloor directly but a more likely scenario would be for oil to adhere to other particles and precipitate 

to the seafloor, much like rainfall, and which is sometimes called “marine snow” (Kingston et al., 1995; 

International Tanker Owners Pollution Federation Limited, 2011; Passow et al., 2012). Oil would also 

reach the seafloor through planktonic consumption and associated excretion, which is distributed over the 

seafloor (International Tanker Owners Pollution Federation Limited, 2011). These mechanisms would 

result in a wide distribution of small amounts of oil (or oil by-products). This oil would be in the process 

of biodegradation from bacterial action, which would continue on the seafloor, resulting in scattered 

microhabitats with an enriched carbon environment (Hazen et al., 2010). Habitats directly under the path 

of the oil plume as it disperses and “rains” down to the seafloor may experience minor effects; however, 

since the oil would be deposited in a widely scattered and decayed state, little overall effect is anticipated.

For example, White et al. (2012) documented a deepwater coral site at a depth of 1,370 m (4,495 ft) 

that was severely damaged following the Deepwater Horizon explosion, oil spill, and response. The site 

is in Mississippi Canyon Block 294, 11 km (7 mi) southwest of the spill location. Flocculent material 

was observed covering these corals, and biomarker signatures from residual hydrocarbon compounds 

matched that of Deepwater Horizon oil. Associated invertebrates also exhibited signs of stress. Fisher 

et al. (2014) described two additional deepwater coral communities with negative impacts attributed to 

the Deepwater Horizon oil spill: Mississippi Canyon Block 297 (6 km [4 mi] south of the Macondo

wellhead) and Mississippi Canyon Block 344 (22 km [14 mi] southeast of the Macondo wellhead). 

Observed impacts at Mississippi Canyon Block 297 were roughly similar to those seen in Mississippi 

Canyon Block 294 (White et al., 2012), but the impacts at Mississippi Canyon Block 344 were less 

severe. Numerous other deepwater coral communities investigated since the spill have remained healthy 

(White et al., 2012; Fisher et al., 2014). Although damage to chemosynthetic communities in the vicinity 

of the Macondo well has not been reported to date, despite numerous research efforts in that vicinity 

(Shedd, official communication, 2015), the above studies illustrate the potential for damage via “marine 

snow.” 

Although (as shown in the Deepwater Horizon oil spill) subsurface plumes can be generated when oil 

is ejected under high pressure or dispersants are used subsea, in most cases, a majority of the oil 

originating from a seafloor blowout in deep water is expected to rise rapidly to the sea surface. Upward 

movement of the oil may also be reduced if methane mixed with the oil is dissolved into the water 

(Adcroft et al., 2010). A sustained spill would continuously create surface slicks and possibly subsurface 

spill plumes. Some of the oil in the water column would become diluted over time, reducing transport to 

the seafloor (Vandermeulen, 1982). Concentrations of dispersed and dissolved oil in the Macondo well 

blowout and spill subsea plume were reported to be in the part per million range or less and were 

generally lower away from the water’s surface and away from the wellhead (Adcroft et al., 2010; Haddad 

and Murawski, 2010; Joint Analysis Group, 2010; Lubchenco et al., 2010). In addition, microbial 

degradation of oil occurs in the water column rendering oil less toxic when it contacts the seafloor (Hazen 

et al., 2010). 
B-48 Central Planning Area Lease Sale 247 Supplemental EIS

A sustained spill may result in elevated exposure concentrations to chemosynthetic features if a 

subsea oil plume contacts them directly. Dispersed oil is mixed with water, and its movement is then 

dictated by water currents and the physical, chemical, and biodegradation pathways. BOEM’s policy 

(refer to NTL 2009-G39) prevents wells from being placed immediately adjacent to sensitive 

communities; however, in the event of a seafloor blowout, some oil could be carried to chemosynthetic 

communities by subsea plumes. Impacts may include reduced recruitment success, reduced growth, and 

reduced biological cover as a result of impaired recruitment. Concentrated oil plumes reaching 

chemosynthetic communities could cause oiling of organisms, resulting in the death of entire populations 

on localized sensitive habitats. The longer the oil remains suspended in the water column, the more 

dispersed, less concentrated, and more biodegraded it would become. Depending on how long oil 

remained suspended in the water column, it may be thoroughly degraded by biological action before 

contacting the seafloor (Hazen et al., 2010; Valentine et al., 2010). Biodegradation rates in cold, 

deepwater environments are not well understood at this time. In general, potential impacts to 

chemosynthetic communities would be localized due to the directional movement of oil plumes by the 

water currents and because the sensitive habitats have a scattered, patchy distribution. While a few patch 

habitats may be affected, the Gulfwide ecosystem of chemosynthetic communities would be expected to 

suffer no significant effects.

Drilling muds comprised primarily of barite may be pumped into a well to stop a blowout. If a “kill” 

is not successful, the mud (possibly tens of thousands of barrels) may be forced out of the well and 

deposited on the seafloor near the well site. Any organisms beneath the extruded drilling mud would be 

buried. Based on stipulations as described in NTL 2009-G40, a well should be far enough away from a 

chemosynthetic community to prevent extruded drilling muds from smothering sensitive benthic 

communities. 

Phase 3—Onshore Contact

The third phase of a catastrophic blowout focuses on the approach of oil to the shoreline. This 

involves the possible oiling of coastal resources including beaches, wetlands, SAV and seagrasses, the 

shallow seafloor, and any resources drifting in the water column. Response efforts can produce additional 

serious impacts. There would be no additional adverse impacts to chemosynthetic communities in deep 

water as a result of the events and the potential impact-producing factors that could occur throughout 

Phase 3 of a catastrophic spill because the chemosynthetic communities are located offshore in deep 

water (>300 m, 610 ft). 

Phase 4— Post-Spill, Long-Term Recovery and Response 

The final phase of a catastrophic blowout is the long-term response of the ecosystem and its recovery. 

Both the natural rate of recovery and the persistence of oil in natural habitats over time determine what 

long-term effects may occur. Contaminants degrade over time but may become sequestered as inert 

forms (e.g., buried in sediment) until disturbed and reactivated, producing renewed impacts. Valentine 

et al. (2014) found evidence of an area of approximately 3,200 km2 (1,236 mi2

) around the Macondo well 

contaminated by ~1,800 kg (±1,000 kg) (~3,968 lb [±2,205 lb]) of excess hopane (a tracer for crude oil) 

and reflecting deposition of oil from the Deepwater Horizon explosion and oil spill. Maps of the 

contaminated area in Valentine et al. (2014) were compared with BOEM’s seismic water-bottom anomaly 

database, and it appears that some chemosynthetic communities may be within the contamination 

footprint, although damage to chemosynthetic communities in the vicinity of the Macondo well has not 

been reported to date despite numerous research efforts in that vicinity (Shedd, official communication, 

2015). 

Because research specific to chemosynthetic organisms is limited, it can be useful to consider 

research regarding impacts relevant to deepwater corals, especially those associated with seeps that can be 

included in the broader definition of a chemosynthetic community, such as Callogorgia delta. Such 

research (DeLeo et al., 2015) is considered here as potentially relevant, with the major caveat that 

experiments were not performed on chemosynthetic organisms themselves and that results could be 

different. DeLeo et al. (2015) performed laboratory tests on the effects of (1) bulk oil-water mixtures, 

(2) water-accommodated oil fractions, (3) the chemical dispersant COREXIT 9500As, and (4) a 

combination of hydrocarbons and dispersants on representative, living samples of three species of 
Catastrophic Spill Event Analysis B-49

northern GOM corals (i.e., Paramuricea type B3, Callogorgia delta, and Leiopathes glaberrima) 

obtained in the field at depths of 500-1,100 m (1,640-3,609 ft), exposing the samples for a 96-hour 

period. All species showed greater health declines in response to dispersant alone (2.3-3.4 fold) and to 

the oil-dispersant mixtures (1.1-4.4 fold) than in the oil only treatments, which did not result in mortality. 

C. delta, which is found in increased abundance near natural hydrocarbon seeps and may have some 

natural adaptation to short-term oil exposure, showed less severe health declines than the other two 

species in response to oil and oil/dispersant mixtures. It can be reasonably concluded that chemosynthetic 

organisms such as tubeworms and bivalves, which intentionally consume hydrocarbons, would possess 

similar adaptations to naturally occurring levels of oil.

One recent in-situ study (White et al., 2014) following the Deepwater Horizon explosion, oil spill, 

and response evaluated possible long-term persistence of both oil and a component of the dispersant 

COREXIT used during that spill, i.e., the anionic surfactant DOSS (dioctyl sodium sulfosuccinate). 

Samples were taken from both seafloor sediments and flocculent material in an affected deepwater coral 

community in Mississippi Canyon Block 294 and compared with other Deepwater Horizon oil spillderived samples collected on coastal beaches. While this study did not measure or link toxicity of oil or 

DOSS to coral tissues, it noted that DOSS was found to persist for 6 months in the samples taken from the 

coral community and up to 4 years in the beach samples. These findings could present an additional 

concern if sediments containing DOSS are demonstrated to be toxic to deepwater benthic organisms. 

Another study of this same area (Hsing et al., 2013), however, indicated that some of the corals with the 

least damage appear to be improving in health.

If oil is ejected under high pressure or dispersants are applied at the source near the seafloor, oil 

would mix into the water column, be carried by underwater currents, and eventually contact the seafloor 

in some form, either concentrated (near the source) or dispersed and decayed (farther from the source). 

The oil could then impact patches of chemosynthetic community habitat in its path. The farther the 

dispersed oil travels, the more diluted it would become as it mixes with surrounding water. 

Chemosynthetic communities located at more than 610 m (2,000 ft) away from a blowout could 

experience minor impacts from suspended sediments that travel with currents, although the sediment 

concentration would be diluted with distance from the well. Studies indicate that periods of decades to 

hundreds of years are required to reestablish a seep community once it has disappeared (depending on the 

community type) (Powell, 1995; Fisher, 1995). There is evidence that substantial impacts on these 

communities could permanently prevent reestablishment, particularly if hard substrate required for 

recolonization is buried by resuspended sediments from a blowout. 

Overall Summary and Conclusion (Phases 1-4) 

Chemosynthetic communities would potentially be subject to detrimental effects from a catastrophic 

seafloor blowout. Sediment and oiled sediment from the initial event (Phase 1) could have lethal or 

sublethal impacts if in close proximity, but they are not likely to reach chemosynthetic communities in 

heavy amounts because of requirements described in NTL 2009-G40. Fine sediment from a blowout may 

reach the location of sensitive habitats, producing sublethal effects. The initial accident could result in the 

drilling rig and equipment falling on a sensitive seafloor habitat if the structure travels more than 610 m 

(2,000 ft) from the well site.

The ongoing spill event (Phase 2) would have the most effect on chemosynthetic communities. 

Chemosynthetic communities are at risk from subsea oil plumes that could directly contact localized 

patches of sensitive habitat. Oil plumes reaching chemosynthetic communities could cause oiling of 

organisms, resulting in the death of entire populations on localized sensitive habitats. However, potential 

impacts would be localized due to the directional movement of oil plumes by the water currents and 

because the sensitive habitats have a scattered, patchy distribution. The more likely scenario would be 

exposure to widely dispersed, biodegraded particles that “rain” down from a passing oil plume. While a 

few patch habitats may be affected, the Gulfwide ecosystem of chemosynthetic communities would be 

expected to suffer no significant effects. 

Oil reaching the shore (Phase 3) presents no additional adverse impacts to chemosynthetic 

communities because the chemosynthetic communities are located offshore in deep water (>300 m; 

610 ft).

The recovery of chemosynthetic communities (Phase 4) depends on the severity of initial impacts. A 

catastrophic spill combined with the application of dispersant has the potential to cause devastating 
B-50 Central Planning Area Lease Sale 247 Supplemental EIS

effects on local patches of habitat in the path of subsea plumes where they physically contact the seafloor. 

Studies indicate that periods from decades to hundreds of years are required to reestablish a seep 

community once it has disappeared (depending on the community type) (Powell, 1995; Fisher, 1995). 

The burial of hard substrate could permanently prevent recovery. Sublethal effects are possible for 

communities that receive a lower level of impact. Examples of these effects could include temporary 

reduction in feeding, expenditure of energy to remove the oil, loss of gametes and reproductive delays, 

and loss of tissue mass. However, most chemosynthetic community habitats are expected to experience 

no impacts from a catastrophic seafloor blowout because of the directional movement of oil plumes by the 

water currents and because chemosynthetic communities have a scattered, patchy distribution.

B.3.1.10. Nonchemosynthetic Deepwater Benthic Communities

Deepwater benthic communities of the Gulf of Mexico include chemosynthetic communities (refer to 

Chapter B.3.1.9) and nonchemosynthetic deepwater benthic communities (also termed “deepwater coral 

communities”) that are dependent on the presence of hard substrates. Certain deepwater coral species, 

such as Lophelia pertusa, attach to exposed hard substrates and can create complex three-dimensional 

structural microhabitats, sometimes termed “framework forming” corals. These structures are often used 

by benthic invertebrates, including echinoderms (e.g., brittle stars and basket stars), sea anemones, 

crustaceans, and various other benthic megafauna. Other species of soft corals and gorgonians 

(commonly known as sea whips and sea fans) may also provide a lesser degree of usable habitat for other 

benthic megafauna. Deep water is defined here as water depths >300 m (984 ft). These types of 

deepwater coral communities are relatively rare in shallower waters. The possible impacts to deepwater 

coral communities from a catastrophic blowout depend on the location and the nature of the event.

Phase 1—Initial Event

During the initial phase of a catastrophic blowout, impacts may include disturbance of sediments, 

destruction of the drilling rig, release of oil and natural gas (methane), and emergency response efforts. 

This phase deals with the immediate effects of a blowout located at least 3 nmi (3.5 mi; 5.6 km) from 

shore. 

A catastrophic blowout outside the well casing and below the seafloor or at the seafloor-water 

interface could resuspend large quantities of bottom sediments and create a large crater, destroying many 

organisms within a few hundred meters of the wellhead. A blowout that occurs outside the well casing 

can rapidly deposit 30 cm (12 in) or more of sediment within a few hundred meters and may smother 

much of the benthic community in a localized area. Some fine sediment could travel up to a few thousand 

meters before redeposition, negatively impacting a localized area of benthic communities. If a blowout 

were to occur close enough to a sensitive deepwater coral community, suspended sediment may impact a 

localized area of benthic organisms. Allers et al. (2013) demonstrated initial resilience of the structureforming deepwater coral Lophelia pertusa to sedimentation but noted lethal or sublethal impacts from 

complete burial or partial sedimentation that continued for an extended period of time. Restrictions 

described in NTL 2009-G40 require drilling to be distanced at least 610 m (2,000 ft) from possible 

deepwater coral communities. During a blowout, suspended sediment may become contaminated with oil 

and subsequently deposit that oil down-current from the source. The highest concentrations of 

contamination would be nearest the well, and concentrations would diminish with distance. A 

catastrophic blowout that occurs above the seabed (at the rig, along the riser between the seafloor and sea 

surface, or through leak paths on the BOP/wellhead) would not disturb the sediment. 

Destruction of the oil drilling rig and associated equipment could have an acute effect on any 

nonchemosynthetic communities caught under the direct impact of the equipment when it falls to the 

seafloor. However, the restrictions described in NTL 2009-G40 require drilling locations to be 610 m 

(2,000 ft) from any possible indications of sensitive deepwater benthic communities, reducing the 

probability that a rig would settle directly on sensitive habitat. 

A catastrophic blowout would likely result in released oil rapidly rising to the sea surface because 

typical reserves in the GOM have specific gravity characteristics that are much lighter than water (refer to 

Chapter 3.2.1.3 of this Supplemental EIS; Environment Canada, 2011; Trudel et al., 2001). The oil 

would surface almost directly over the source location. Oil floating to the sea surface would be 

effectively removed from affecting nonchemosynthetic communities on the seafloor. Even oil treated 
Catastrophic Spill Event Analysis B-51

with chemical dispersants on the sea surface would not be expected to have widespread impacts to 

deepwater communities. Reports on dispersant usage on surface oil indicate that a majority of the 

dispersed oil remains in the top 10 m (33 ft) of the water column, with 60 percent of the oil in the top 2 m 

(6 ft) (McAuliffe et al., 1981a; Lewis and Aurand, 1997). Lubchenco et al. (2010) report that chemically 

dispersed surface oil from the Macondo well blowout and oil spill remained in the top 6 m (20 ft) of the 

water column where it mixed with surrounding waters and biodegraded. However, if the oil is ejected 

under high pressure, micro-droplets of oil may form and become entrained in the water column (Boehm 

and Fiest, 1982; Adcroft et al., 2010). Upward movement of the oil may also be reduced if methane 

mixed with the oil is dissolved into the water column, reducing the buoyancy of the oil/gas stream 

(Adcroft et al., 2010). Large oil droplets would rise to the sea surface, but smaller droplets, formed by 

vigorous turbulence in the plume or the injection of dispersants, may remain neutrally buoyant in the 

water column, creating a subsurface plume (Adcroft et al., 2010; Joint Analysis Group, 2010). The 

likelihood that a deepwater coral community would be affected by the initial stage of a catastrophic event 

would be reduced with adherence to the NTL 2009-G40 requirements distancing drilling activities from 

sensitive habitats because released oil would rapidly rise to a level above the habitat and because surface 

oil would not mix to the depths of such communities. The required separation distance would also allow 

for a subsea plume to mix with the surrounding water and become diluted before it reached a deepwater 

community. 

Phase 2—Offshore Spill

During the second phase of a catastrophic blowout, the major impact of concern is the release of oil 

and methane over time. Response efforts may produce additional impacts. This chapter deals with the 

growing effects of a blowout that releases oil and methane into the offshore environment.

Oil and chemical spills that originate at the sea surface are not considered to be a potential source of 

measurable impacts on deepwater coral communities because of the water depths at which these 

communities are located. Oil spills at the surface would tend not to sink, and the risk of weathered 

components of a surface slick reaching the benthos in any measurable concentration would be very small. 

Large concentrations of surface oil are unlikely to physically mix to the depths of deepwater communities 

under natural conditions (Lange, 1985; McAuliffe et al., 1975 and 1981a; Tkalich and Chan, 2002).

A catastrophic spill resulting from a loss of well control in deep water has the potential to impact 

offshore benthic communities, particularly if the use of chemical dispersants increases exposure time by 

creating subsurface plumes. Sublethal effects are possible for communities that receive a lower level of 

impact. Examples of these effects could include temporary lack of feeding, expenditure of energy to 

remove the oil, loss of gametes and reproductive delays, and loss of tissue mass. Oil plumes that remain 

in the water column for longer periods would disperse and decay, having only a minimal effect. 

Depending on how long it remains in the water column, oil may be thoroughly degraded by biological 

action before contacting the seafloor. Water currents can carry a plume to contact the seafloor directly, 

but a more likely scenario would be for oil to adhere to other particles and precipitate to the seafloor, 

much like rainfall (Kingston et al., 1995; International Tanker Owners Pollution Federation Limited, 

2011; Passow et al., 2012). Oil also would reach the seafloor through consumption by plankton, with 

excretion distributed over the seafloor (International Tanker Owners Pollution Federation Limited, 2011). 

These mechanisms would result in a wide distribution of small amounts of oil (or oil by-products). This 

oil would be in the process of biodegradation from bacterial action, which would continue on the seafloor, 

resulting in scattered microhabitats with an enriched carbon environment (Hazen et al., 2010). Habitats 

directly under the path of the oil plume as it disperses and “rains” down to the seafloor may experience 

minor effects; however, because the oil would be deposited in a widely scattered and decayed state, little 

effect is anticipated.

For example, White et al. (2012) documented a deepwater coral site at a depth of 1,370 m (4,495 ft) 

that was severely damaged following the Deepwater Horizon explosion, oil spill, and response. The site 

is in Mississippi Canyon Block 294, 11 km (7 mi) southwest of the spill location. Flocculent material 

was observed covering these corals, and biomarker signatures from residual hydrocarbon compounds 

matched that of Deepwater Horizon oil. Associated invertebrates also exhibited signs of stress. Fisher 

et al. (2014) described two additional deepwater coral communities with negative impacts attributed to 

the Deepwater Horizon oil spill: Mississippi Canyon Block 297 (6 km [4 mi] south of the Macondo

wellhead) and Mississippi Canyon Block 344 (22 km [14 mi] southeast of the Macondo wellhead). 
B-52 Central Planning Area Lease Sale 247 Supplemental EIS

Observed impacts at Mississippi Canyon Block 297 were roughly similar to those seen in Mississippi 

Canyon Block 294 (White et al., 2012), but the impacts at Mississippi Canyon Block 344 were less 

severe. Numerous other deepwater coral communities investigated since the spill have remained healthy 

(White et al., 2012; Fisher et al. 2014). 

Although (as shown in the Deepwater Horizon oil spill) subsurface plumes can be generated when oil 

is ejected under high pressure or when dispersants are used subsea in most cases, a majority of the oil 

originating from a seafloor blowout in deep water is expected to rise rapidly to the sea surface. Upward 

movement of the oil may also be reduced if methane mixed with the oil is dissolved into the water 

(Adcroft et al., 2010). A sustained spill would continuously create surface slicks and possibly subsurface 

spill plumes. Some of the oil in the water column would become diluted over time, reducing transport to 

the seafloor (Vandermeulen, 1982). Concentrations of dispersed and dissolved oil in the Deepwater 

Horizon oil spill’s subsea plume were reported to be in the part per million range or less and were 

generally lower away from the water’s surface and away from the wellhead (Adcroft et al., 2010; Haddad 

and Murawski, 2010; Joint Analysis Group, 2010; Lubchenco et al., 2010). In addition, microbial 

degradation of the oil occurs in the water, rendering the oil less toxic when it contacts the seafloor (Hazen 

et al., 2010). However, as evidenced by the report of White et al. (2012), subsea plumes can still retain 

toxic concentrations over a distance of at least 11 km (7 mi).

Oil in a plume can adhere to other particles and precipitate to the seafloor, much like rainfall 

(Kingston et al., 1995; International Tanker Owners Pollution Federation Limited, 2011; Passow et al., 

2012). Oil also would reach the seafloor through consumption by plankton, with excretion distributed 

over the seafloor (International Tanker Owners Pollution Federation Limited, 2011). These mechanisms 

would result in a wide distribution of small amounts of oil. Throughout these processes, oil would be 

biodegraded from bacterial action, which would continue on the seafloor, resulting in scattered 

microhabitats with an enriched carbon environment (Hazen et al., 2010). 

A sustained spill may result in elevated exposure concentrations to deepwater coral communities if a 

subsea oil plume contacts them directly. Dispersed oil is mixed with water, and its movement is then 

dictated by water currents and the physical, chemical, and biological degradation pathways. BOEM’s 

policy (refer to NTL 2009-G40) prevents wells from being placed immediately adjacent to sensitive 

communities; however, in the event of a seafloor blowout, some oil could be carried to deepwater coral 

communities by subsea plumes. Impacts may include reduced recruitment success, reduced growth, and 

reduced biological cover as a result of impaired recruitment. Concentrated oil plumes reaching deepwater 

coral communities could cause oiling of organisms, resulting in the death of entire populations on 

localized sensitive habitats. The longer the oil remains suspended in the water column the more 

dispersed, less concentrated, and more degraded it would become. Depending on how long oil remained 

suspended in the water column, it may be thoroughly degraded by biological action before contacting the 

seafloor (Hazen et al., 2010; Valentine et al., 2010). Biodegradation rates in cold, deepwater 

environments are not well understood at this time. In general, the potential impacts to deepwater 

deepwater coral communities would be localized due to the directional movement of oil plumes by the 

water currents and because the sensitive habitats have a scattered, patchy distribution. While a few patch 

habitats may be affected, the Gulfwide ecosystem of deepwater coral communities would be expected to 

suffer no significant effects.

Drilling muds comprised primarily of barite may be pumped into a well to stop a blowout. If a “kill” 

is not successful, the mud (possibly tens of thousands of barrels) may be forced out of the well and 

deposited on the seafloor near the well site. Any organisms beneath the extruded drilling mud would be 

buried. Based on stipulations as described in NTL 2009-G40, a well should be sufficiently distanced 

from sensitive deepwater coral communities to prevent extruded drilling muds from smothering them. 

Phase 3—Onshore Contact

The third phase of a catastrophic blowout focuses on the approach of oil to the shoreline. This 

involves the possible oiling of coastal resources including beaches, wetlands, SAV and seagrasses, the 

shallow seafloor, and any resources drifting in the water column. Response efforts can produce additional 

serious impacts. There would be no adverse impacts to deepwater coral communities in deep water as a 

result of the events and the potential impact-producing factors that could occur throughout Phase 3 of a 

catastrophic spill because the communities are located offshore in deep water (>300 m; 610 ft).
Catastrophic Spill Event Analysis B-53

Phase 4—Post-Spill, Long-Term Recovery and Response 

The final phase of a catastrophic blowout is the long-term response of the ecosystem and its recovery. 

Both the natural rate of recovery and the persistence of oil in natural habitats over time determine what 

long-term effects may occur. Contaminants degrade over time, but they may become sequestered as inert 

forms (e.g., buried in sediment) until disturbed and re-activated, potentially producing renewed impacts. 

Valentine et al. (2014) found evidence of an area of approximately 3,200 km2 (1,236 mi2

) around the 

Macondo well contaminated by ~1,800 kg (±1,000 kg) (~3,968 lb [±2,205 lb]) of excess hopane (a tracer 

for crude oil), reflecting deposition of oil from the Deepwater Horizon explosion and oil spill. 

Although deepwater coral communities often live in close association with hydrocarbon seeps (since 

the carbonate substrate is precipitated by chemosynthetic communities), this does not mean they are 

necessarily tolerant to the effects of oil contamination. Natural seepage is very constant and at very low 

rates as compared with the potential volume of oil released from a catastrophic event (blowout or pipeline 

rupture). In addition, deepwater coral organisms, such as Lophelia pertusa, inhabit areas around the 

perimeter of seeps and sites where hydrocarbon seepage has reduced its flow or stopped. Typical Gulf of 

Mexico oil is light and floats rapidly to the surface rather than being carried horizontally across benthic 

communities by water currents (Johansen et al., 2001; MacDonald et al., 1995; Trudel et al., 2001). So, 

although deepwater coral communities are often found near naturally occurring oil seeps, they are not 

typically exposed to concentrated oil.

If oil is ejected under high pressure or dispersants are applied at the source near the seafloor, oil 

would mix into the water column, be carried by underwater currents, and eventually contact the seafloor 

in some form, either concentrated (near the source) or dispersed and decayed (farther from the source). 

The oil could then impact patches of deepwater coral community habitat in its path. The farther the 

dispersed oil travels, the more diluted it would become as it mixes with surrounding water. Sensitive 

deepwater coral communities distanced >610 m (2,000 ft) away from a blowout could experience minor 

impacts from suspended sediments that travel with currents, although the sediment concentration would 

become more diluted with distance. 

Laboratory tests by DeLeo et al. (2015) on the relative effects of oil, chemical dispersants, and 

chemically dispersed oil mixtures on three species of northern GOM corals (i.e., Paramuricea type B3, 

Callogorgia delta, and Leiopathes glaberrima) found much greater health declines in response to 

chemical dispersants and to oil-dispersant mixtures than to oil-only treatments, which did not result in 

mortality. The coral species Callogorgia delta, which is found in increased abundance near natural 

hydrocarbon seeps and may have some natural adaptation to short-term oil exposure, showed less severe 

health declines than the other two species in response to oil and oil/dispersant mixtures. It must always 

be noted that, generally, laboratory experimental concentrations are designed to discover toxicity 

thresholds (DeLeo et al., 2015) that exceed likely exposure concentrations in the field. These results may 

not be applicable to all deepwater coral species.

One recent in-situ study (White et al., 2014) following the Deepwater Horizon explosion, oil spill, 

and response evaluated possible long-term persistence of both oil and a component of the COREXIT 

dispersant used during that spill, i.e., the anionic surfactant DOSS (dioctyl sodium sulfosuccinate). 

Samples were taken from both seafloor sediments and flocculent material in an affected deepwater coral 

community in Mississippi Canyon Block 294 and compared with other Deepwater Horizon oil spillderived samples collected on coastal beaches. While this study did not measure or link toxicity of oil or 

DOSS to coral tissues, it noted that DOSS was found to persist for 6 months in the samples taken from the 

coral community and up to 4 years in the beach samples. These findings could present an additional 

concern if sediments containing DOSS are demonstrated to be toxic to deepwater benthic organisms. 

Another study of this same area (Hsing et al., 2013), however, indicated that some of the corals with the 

least damage appear to be improving in health.

Experiments with shallow tropical corals indicate that corals have a high tolerance to oil exposure. 

The mucus layers on coral resist penetration of oil and slough off the contaminant. Longer exposure 

times and areas of tissue where oil adheres to the coral are more likely to result in tissue damage and 

death of polyps. Corals with branching growth forms appear to be more susceptible to damage from oil 

exposure (Shigenaka, 2001). The most common deepwater coral, Lophelia pertusa, is a branching 

species. Tests with shallow tropical gorgonians indicate relatively low toxic effects to the coral (Cohen 

et al., 1977), suggesting deepwater gorgonians may have a similar response. Depending on the level of 

exposure, the response of deepwater coral to oil from a catastrophic spill would vary. Exposure to widely 
B-54 Central Planning Area Lease Sale 247 Supplemental EIS

dispersed oil adhering to organic detritus and partially degraded by bacteria may be expected to result in 

little effect. Direct contact with plumes of relatively fresh dispersed oil droplets in the vicinity of the 

incident could cause the death of affected coral polyps through exposure and potential feeding on oil 

droplets by polyps. Median levels of exposure to dispersed oil in a partly degraded condition may result 

in effects similar to those of shallow tropical corals, with often no discernible effects other than temporary 

contraction and some sloughing. The health of corals may be degraded by the necessary expenditure of 

energy as the corals respond to oiling (Shigenaka, 2001). Communities exposed to more concentrated oil 

may experience detrimental effects, including death of affected organisms, tissue damage, lack of growth, 

interruption of reproductive cycles, and loss of gametes. Many invertebrates associated with deepwater 

coral communities, particularly the crustaceans, would likely be more susceptible to damage from oil 

exposure. The recolonization of severely damaged or destroyed communities could take years or decades. 

Burial of hard substrate could permanently prevent recovery. However, because of the scarcity of 

deepwater hard bottoms, their comparatively low surface area, and the distancing requirements set by 

BOEM in NTL 2009-G40, it is unlikely that a sensitive habitat would be located adjacent to a seafloor 

blowout or that concentrated oil would contact the site. 

Overall Summary and Conclusion (Phases 1-4) 

Deepwater coral communities would potentially be subject to detrimental effects from a catastrophic 

seafloor blowout. Sediment and oiled sediment from the initial event (Phase 1) could have lethal or 

sublethal impacts if in close proximity, but they are not likely to reach sensitive deepwater coral 

communities in heavy amounts because of distancing requirements described in NTL 2009-G40. Fine 

sediment from a blowout may reach the location of sensitive habitats, producing sublethal effects. The 

initial accident could result in the drilling rig and equipment falling on a sensitive seafloor habitat if the 

structure travels more than 610 m (2,000 ft) from the well site. 

The ongoing spill event (Phase 2) would have the greatest effect on deepwater coral communities. 

These communities are at risk from subsea oil plumes that could directly contact localized patches of 

sensitive habitat. Oil plumes reaching deepwater coral communities could cause oiling of organisms, 

resulting in the death of entire populations on localized sensitive habitats. However, the potential impacts 

would be localized due to the directional movement of oil plumes by the water currents and because the 

sensitive habitats have a scattered, patchy distribution. The more likely result would be exposure to 

widely dispersed, biodegraded particles that “rain” down from a passing oil plume. While a few patch 

habitats may be affected, the Gulfwide ecosystem of deepwater coral communities would be expected to 

suffer no significant effects.

Oil reaching the shore (Phase 3) presents no additional adverse impacts to deepwater coral 

communities because the communities are located offshore in deep water (>300 m; 610 ft). 

The recovery of deepwater coral communities (Phase 4) depends on the severity of initial impacts. A 

catastrophic spill combined with the application of dispersant has the potential to cause devastating 

effects on local patches of sensitive habitat in the path of subsea plumes where they physically contact the 

seafloor. The recolonization of severely damaged or destroyed communities could take years or decades. 

Burial of hard substrate could permanently prevent recovery. Sublethal effects are possible for 

communities that receive a lower level of impact. Examples of these effects could include temporary 

reduction in feeding, expenditure of energy to remove the oil, loss of gametes and reproductive delays, 

and loss of tissue mass. However, most deepwater coral community habitats are expected to experience 

no impacts from a catastrophic seafloor blowout because of the directional movement of oil plumes by the 

water currents and because the habitats have a scattered, patchy distribution. 

B.3.1.11. Soft Bottom Benthic Communities

The seafloor on the continental shelf in the Gulf of Mexico consists primarily of muddy to sandy 

sediments. Benthic organisms found on the seafloor include infauna (animals that live in the substrate, 

including mostly burrowing worms, crustaceans, and mollusks) and epifauna (animals that live on or are 

attached to the substrate; mostly crustaceans, as well as echinoderms, mollusks, hydroids, sponges, soft 

and hard corals, and demersal fishes). Infauna is comprised of meiofauna, small organisms (63-500 μm) 

that live among the grains of sediment; and macroinfauna, slightly larger organisms (>0.5 mm; 0.02 in) 

that live in the sediment (Dames and Moore, Inc., 1979). Shrimp and demersal fish are closely associated 
Catastrophic Spill Event Analysis B-55

with the benthic community. The most abundant organisms on the continental shelf are the depositfeeding polychaetes. The slope and deep sea consist of vast areas of primarily fine sediments that support 

benthic communities with lower densities and biomass but higher diversity than the continental shelf 

(Rowe and Kennicutt, 2001). 

Phase 1—Initial Event

A blowout from an oil well could result in a catastrophic spill event. A catastrophic blowout would 

result in released oil rapidly rising to the sea surface because all known reserves in the GOM have 

specific gravity characteristics that would preclude oil from sinking immediately after release at a 

blowout site. The oil would surface almost directly over the source location. However, if the oil is 

ejected under high pressure, micro-droplets of oil may form and become entrained in the water column 

(Boehm and Fiest, 1982; Adcroft et al., 2010). The upward movement of the oil may be reduced if 

methane mixed with the oil is dissolved into the water column, reducing the oil’s buoyancy (Adcroft 

et al., 2010). Large oil droplets would rise to the sea surface, but smaller droplets, formed by vigorous 

turbulence in the plume or the injection of dispersants, may remain neutrally buoyant in the water column, 

creating a subsurface plume (Adcroft et al., 2010; Joint Analysis Group, 2010). Dispersed oil in the water 

column begins to biodegrade and may flocculate with particulate matter, promoting sinking of the 

particles. Subsea plumes or sinking oil on particulates may contact portions of the seafloor. 

A catastrophic blowout outside the well casing and below the seafloor or at the seafloor-water 

interface could resuspend large quantities of bottom sediments and create a large crater, destroying many 

organisms within a few hundred meters of the wellhead. Some fine sediment could travel up to a few 

thousand meters before redeposition, negatively impacting a localized area of benthic communities. The 

localized seafloor habitat around which a seafloor blowout occurs would be impacted by suspended and 

redeposited sediment.

A catastrophic blowout that occurs above the seabed (at the rig, along the riser between the seafloor 

and sea surface, or through leak paths on the BOP/wellhead) would not disturb the sediment.

The use of subsea dispersants would increase the exposure of offshore benthic habitats to dispersed 

oil droplets in the water column, as well as the chemicals used in the dispersants. The use of subsea 

dispersants is not likely to occur for seafloor blowouts outside the well casing. 

Impacts to Soft Bottom Benthic Communities

Impacts that occur to benthic organisms as a result of a blowout would depend on the type of blowout 

and their distance from the blowout. Also, if the blowout were to occur beneath the seabed, soft sediment 

habitat would be destroyed by the formation of a crater, and the suspension and subsequent deposition of 

disturbed sediment would smother localized areas of benthic communities. A blowout that occurs outside 

the well casing can rapidly deposit 30 cm (12 in) or more of sediment within a few hundred meters and 

may smother much of the soft bottom community in a localized area. Benthic communities exposed to 

large amounts of resuspended and deposited sediments following a catastrophic, subsurface blowout 

could be subject to smothering, sediment suffocation, and exposure to resuspended toxic contaminants. 

Impacts to organisms as a result of sedimentation would vary based on species tolerance, degree of 

sedimentation, length of exposure, burial depth, and vertical migration ability through sediment. 

A portion or the entire rig may sink to the seafloor as a result of a blowout. The benthic features and 

communities upon which the rig settles would be destroyed or smothered. A settling rig may suspend 

sediments, which may smother nearby benthic communities. The habitats beneath the rig may be 

permanently lost; however, the rig itself may become an artificial reef upon which epibenthic organisms 

may settle. The surrounding benthic communities that were smothered by sediment would repopulate 

from nearby stocks through spawning recruitment and immigration if the hard substrate upon which they 

live was not physically destroyed.

Phase 2—Offshore Spill

A spill from a shallow-water blowout could impact benthic communities on the continental shelf. 

The scenario (Table B-4) for a catastrophic spill on the continental shelf is assumed to last 2-5 months 

and to release 30,000 bbl per day. A total volume of 0.9-3.0 MMbbl of South Louisiana midrange 
B-56 Central Planning Area Lease Sale 247 Supplemental EIS

paraffinic sweet crude oil could be released, which would float (APIo >10). An anticipated 35,000 bbl of 

dispersant may be applied to the surface waters.

A spill from a deepwater blowout could also impact shelf communities and deepwater communities. 

The scenario (Table B-4) for a catastrophic spill in deep water is assumed to last 4-6 months and to 

release 30,000-60,000 bbl per day. A total volume of 2.7-7.2 MMbbl of South Louisiana midrange 

paraffinic sweet crude oil could be released, which would float (APIo >10). Oil properties may change as 

it passes up the well and through the water column, and it may become emulsified. An anticipated 

33,000 bbl of dispersant may be applied to the surface waters and 16,500 bbl may be applied subsea. 

Weathering and dilution of the oil would also occur as it travels from its launch point. It is unlikely that a 

subsurface plume from a deepwater blowout would impact shelf communities. The oil is anticipated to 

remain in deep water and be directed by water currents in the deep water. These currents do not typically 

transit from deep water up onto the shelf (Pond and Pickard, 1983; Inoue et al., 2008). 

Impacts to Soft Bottom Benthic Communities

Impacts from Surface Oil

Surface oil slicks can spread over a large area; however, the majority of the slick is comprised of a 

very thin surface layer of oil moved by winds and currents (Lewis and Aurand, 1997). The potential of 

surface oil slicks to affect benthic habitats is limited by its ability to mix into the water column. Soft 

bottom benthic communities below 10-m (33-ft) water depth are protected from surface oil because of its 

lack of ability to mix with water (Lange, 1985; McAuliffe et al., 1975 and 1981a; Tkalich and Chan, 

2002). Benthic organisms would not become physically coated or smothered by surface oil. However, if 

this surface oil makes its way into the water column through physical mixing, the use of dispersants, or 

the sedimenting to particles in the water column, benthic communities may be impacted. These scenarios 

are discussed in later sections.

Disturbance of the sea surface by storms can mix surface oil into the water column, but the effects are 

generally limited to the upper 10-20 m (33-66 ft) (Lange, 1985; McAuliffe et al., 1975 and 1981a; Tkalich 

and Chan, 2002). Therefore, soft bottom benthic communities located in shallow water have the potential 

to be fouled by oil that is floating on shallow water and mixes to the depth of the seafloor. Nearshore oil 

deposits that occur in sheltered areas, such as bays, may remain in the sediment and impact organisms for 

long periods. Oil in nearshore sediments was found in high concentrations 8 years following the Exxon 

Valdez spill (Dean and Jewett, 2001). Benthic communities located in deeper water would not be 

impacted by oil physically mixed into the water column. However, if dispersants are used, they would 

enable oil to mix into the water column and possibly impact organisms in deeper water. Dispersants are 

discussed later in this chapter. Further detail on this catastrophic OSRA run is contained in Appendix C 

of the CPA 235/241/247 Supplemental EIS. 

Impacts from Subsurface Oil

The presence of a subsurface oil plume on the continental shelf from a shallow-water blowout may 

affect soft bottom benthic communities. A majority of the oil released is expected to rise rapidly to the 

sea surface above the launch point because of the specific gravity characteristics of the oil reserves in the 

GOM, thus not directly sinking to the seafloor and smothering benthic communities. If the oil is ejected 

under high pressure, oil droplets may become entrained in the water column (Boehm and Fiest, 1982; 

Adcroft et al., 2010). The upward movement of the oil may be reduced if methane mixed with the oil is

dissolved into the water column, reducing the oil’s buoyancy (Adcroft et al., 2010). Large oil droplets 

would rise to the sea surface, but smaller droplets, formed by vigorous turbulence in the plume or the 

injection of dispersants, may remain neutrally buoyant in the water column, creating a subsurface plume 

(Adcroft et al., 2010; Joint Analysis Group, 2010). Dispersed oil in the water column begins to 

biodegrade and may flocculate with particulate matter, promoting sinking of the particles. Subsurface

plumes generated by high-pressure dissolution of oil may come in contact with portions of the seafloor as 

it travels from the source. A sustained spill would continuously create surface slicks and possibly 

subsurface plumes. Some of the oil in the water column will become diluted or evaporated over time, 

reducing any localized transport to the seafloor (Vandermeulen, 1982). In addition, microbial degradation 

of the oil occurs in the water column so that the oil would be less toxic as it travels from the source 

(Hazen et al., 2010). However, a sustained spill may result in elevated exposure concentrations to benthic 
Catastrophic Spill Event Analysis B-57 

communities if the plume reaches them. The longer the spill takes to stop, the longer the exposure time 

and higher the exposure concentration may be.

Soft bottom infaunal communities that come into direct contact with oil may experience sublethal 

and/or lethal effects. The greatest effects of oil exposure would occur close to the well and impacts 

would decrease with distance. A subsurface plume that contacts the seafloor may result in acute toxicity. 

The water accommodated fraction (WAF) or water soluble fraction (WSF) of oil that dissolves in water 

may be the most toxic to organisms, especially larvae and embryos in the water column or at the water 

sediment interface. Lethal effects for marine invertebrates have been reported at exposures between 

0.10 ppm to 100 ppm WSF of oil (Suchanek, 1993). The WSF of petroleum hydrocarbons was reportedly 

highly toxic to the embryos of oysters and sea urchins, while sediment containing weathered fuel was not 

toxic to the same species (Beiras and Saco-Álvarez, 2006). Quahog clam embryos and larvae also 

experienced toxicity and deformation of several different crude oils at WSF concentrations between 

0.10 ppm and 10 ppm (Byrne and Calder, 1977). An experiment indicated that the WSF of No. 2 fuel oil 

at a concentration of 5 ppm disrupted the cellular development of 270 out of 300 test organisms within 

3 hours of exposure (Byrne, 1989). After 48 hours exposure, all of the test organisms died and the 

48-hour LC50 (lethal concentration for 50% of the test population) was calculated to be 0.59 ppm (Byrne, 

1989). Another experiment indicated that a WSF of 0.6 ppm and greater of No. 2 fuel oil depressed 

respiration, reduced mobility of sperm, interfered with cell fertilization and embryonic cleavage, and 

retarded larval development of sand dollar eggs (Nicol et al., 1977). Experiments that exposed sea urchin 

embryos to 10-30 ppm WSF of diesel oil for 15-45 days resulted in defective embryonic development and 

nonviable offspring (Vashchenko, 1980). Therefore, any dissolved petroleum hydrocarbon constituents 

that reach larval benthic organisms may cause acute toxicity and other developmental effects to this life 

stage. The WAF and WSF, however, should be considered “worst-case scenario” values as they are 

based on a closed system at equilibrium with the contaminant and, due to its size and complexity, the 

GOM will not reach equilibrium with released oil. 

Oil in the water column may impact pelagic eggs and larvae of invertebrates. Toxicity tests indicated 

that eggs of many species were killed by diesel oil in seawater, and in general, the smaller eggs died 

earlier (Chia, 1973). Bivalve fertilization and sperm fertility were depressed with exposure to crude oil 

(Renzoni, 1975). The WSF of crude oil was also highly toxic to gametes, embryos, and larvae of bivalves 

(Renzoni, 1975). Oil concentrations of 0.1 and 1 ppm caused a decrease in fertilization, development of 

embryos, survival or larvae, and larval growth in the bivalves Crassostrea virginica and Mulinia lateralis

(Renzoni, 1975). Another experiment, however, calculated the LC50 for a 6-hour exposure of the 

gametes, eggs, and larvae of three bivalves (Crassostrea angulata, Crassostrea gigas, and Mytilus 

galloprovincialis) to be 1,000 ppm oil and 1,000 ppm oil plus dispersant (Renzoni, 1973). Toxicity varies 

widely among species and oil types.

Sublethal responses of marine invertebrates may result in population level changes (Suchanek, 1993). 

Such sublethal responses may occur at concentrations as low as 1-10 ppb (Hyland and Schneider, 1976). 

Sublethal impacts may include reduced feeding rates, reduced ability to detect food, ciliary inhibition, 

reduced movement, decreased aggression, and altered respiration (Suchanek, 1993). 

The farther a subsea plume travels, the more physical and biological changes occur to the oil before it 

reaches benthic organisms. Oil would become diluted as it physically mixes with the surrounding water, 

and significant evaporation occurs from surface slicks. The most toxic compounds of oil are lost within 

the first 24 hours of a spill, leaving the heavier, less toxic compounds in the system (Ganning et al., 

1984). An even greater component of the lighter fuel oils dissipates through evaporation. Water currents 

could carry a plume to contact the seafloor directly, but a likely scenario would be for the oil to adhere to 

other particles and precipitate to the seafloor, much like rainfall (International Tanker Owners Pollution 

Federation Limited, 2011; Kingston et al., 1995). Oil also would reach the seafloor through consumption 

by plankton, with excretion distributed over the seafloor (International Tanker Owners Pollution 

Federation Limited, 2011). The longer and farther a subsea plume travels in the sea, the more dilute the 

oil would be (Vandermeulen, 1982; Tkalich and Chan, 2002). In addition, microbial degradation of the 

oil occurs in the water column, reducing toxicity (Hazen et al., 2010; McAuliffe et al., 1981b). The oil 

would move in the direction of prevailing currents (S.L. Ross Environmental Research Ltd., 1997) and, 

although the oil would weather with the distance it travels, low levels of oil transported in subsea plumes 

would impact benthic communities. These mechanisms would result in a wide distribution of small 

amounts of oil. This oil would be in the process of biodegradation from bacterial action, which would 
B-58 Central Planning Area Lease Sale 247 Supplemental EIS

continue on the seafloor, resulting in scattered microhabitats with an enriched carbon environment (Hazen 

et al., 2010). 

Localized areas of lethal effects would be recolonized by populations from neighboring soft bottom 

substrate once the oil in the sediment has been sufficiently reduced to a level able to support marine life 

(Sanders et al., 1980; Lu and Wu, 2006; Ganning et al., 1984; Gómez Gesteira and Dauvin, 2000; Dean 

and Jewett, 2001). This initial recolonization process may be fairly rapid, but full recovery may take up 

to 10 years depending on the species present, substrate in the area, toxicity of oil spilled, concentration 

and dispersion of oil spilled, and other localized environmental factors that may affect recruitment 

(Kingston et al., 1995; Gómez Gesteira and Dauvin, 2000; Sanders et al., 1980; Conan, 1982). 

Opportunistic species would take advantage of the barren sediment, repopulating impacted areas first. 

These species may occur within the first recruitment cycle of the surrounding populations or from species 

immigration from surrounding stocks and may maintain a stronghold in the area until community 

succession begins (Rhodes and Germano, 1982; Sanders et al., 1980). 

It is unlikely that a subsurface plume from a deepwater blowout would impact shelf communities. 

The oil is anticipated to remain in deep water and be directed by water currents in the deep water. These 

currents do not typically transit from deep water up onto the shelf (Pond and Pickard, 1983; Inoue et al., 

2008). However, the impacts to deepwater soft bottom benthic communities as a result of a blowout 

would similar to those on the continental shelf.

Impacts from Dispersed Oil

If dispersants are used at the sea surface, oil may mix into the water column, and if they are applied 

subsea, dispersed oil can travel with currents and contact the seafloor. Chemically dispersed oil from a 

surface slick is not anticipated to result in lethal exposures to organisms on the seafloor. The chemical 

dispersion of oil may increase the weathering process and allow surface oil to be diluted by greater 

amounts of water. Reports on dispersant usage on surface plumes indicate that a majority of the dispersed 

oil remains in the top 10 m (33 ft) of the water column, with 60 percent of the oil in the top 2 m (6 ft) 

(McAuliffe et al., 1981a). Dispersant usage also reduces the oil’s ability to stick to particles in the water 

column, minimizing oiled sediments from traveling to the seafloor (McAuliffe et al., 1981a). If applied, 

subsea benthic communities near the source could be exposed to dispersed oil that is concentrated enough 

to harm the benthic community. If the oil remains suspended for a longer period of time, it would be 

more dispersed and less concentrated. There is very little information on the behavior of subsea 

dispersants. 

Dispersed oil used at the sea surface reaching the benthic communities in the Gulf of Mexico would 

be expected to be at very low concentrations (<1 ppm) (McAuliffe et al., 1981a). Such concentrations 

would not be life threatening to larval or adult stages on the seafloor based on experiments conducted 

with benthic and pelagic species (Scarlett et al., 2005; Hemmer et al., 2010; George-Ares and Clark, 

2000). Any dispersed oil in the water column that comes in contact with benthic communities may evoke 

short-term negative responses by the organisms (Scarlett et al., 2005). Sublethal responses may include 

reduced feeding rate, erratic movement, and tentacle retraction (Scarlett et al., 2005). In addition, 

although dispersants were detected in waters off Louisiana after the Macondo well blowout and spill, they 

were below USEPA benchmarks of chronic toxicity (OSAT, 2010). The rapid dilution of dispersants in 

the water column and lack of transport to the seafloor was also reported by OSAT (2010) where no 

dispersants were detected in sediment on the Gulf floor following the Macondo well blowout and spill. 

Impacts from Oil Adhering to Sediments

Oiled sediment that settles to the seafloor may affect organisms upon which it settles. The greatest 

impacts would be closest to the well where organisms may become smothered by particles and exposed to 

hydrocarbons. High concentrations of suspended sediment in the water column may lend to large 

quantities of oiled sediment (Moore, 1976). Deposition of oiled sediment is anticipated to begin 

occurring within days or weeks of the spill and may be fairly deep near the source (Ganning et al., 1984; 

Gómez Gesteira and Dauvin, 2000). Oily sand layers were reported to be 10 cm (4 in) deep on the 

seafloor near the Amoco Cadiz spill (Gómez Gesteira and Dauvin, 2000). Acute toxicity may occur near 

the spill, eliminating benthic communities. 
Catastrophic Spill Event Analysis B-59

Much of the oil released from a blowout would rise to the sea surface, therefore dispersing the 

released oil before it makes its way back to the seafloor through flocculation, by deposition from 

organisms that pass it through their systems with food, and by adhering to sinking particles in the water 

column. In addition, small droplets of oil that are entrained in the water column for extended periods of 

time may migrate a great distance from their point of release and may attach to suspended particles in the 

water column and later be deposited on the seafloor (McAuliffe et al., 1975). The majority of organisms 

exposed to oiled sediment are anticipated to experience low-level concentrations because as the oiled 

sediments settle to the seafloor they are widely dispersed. Impacts may include reduced recruitment 

success, reduced growth, and altered community composition as a result of impaired recruitment.

Impacts from Oil-Spill-Response Activity

Continued localized disturbance of soft bottom communities may occur during oil-spill response 

efforts. Anchors used to set booms to contain oil or vessel anchors in decontamination zones may affect 

infaunal communities in the response activity zone. Infaunal communities may be altered in the anchor 

scar, and deposition of suspended sediment may result from the setting and resetting of anchors. The 

disturbed benthic community should begin to repopulate from the surrounding communities during their 

next recruitment event and through immigration of organisms from surrounding stocks. Any 

decontamination activities, such as cleaning vessel hulls of oil, may also contaminate the sediments of the 

decontamination zone, as some oil may settle to the seabed, impacting the underlying benthic community. 

If a blowout occurs at the seafloor, drilling muds (primarily barite) may be pumped into a well in 

order to “kill” it. If a kill is not successful, the mud (possibly tens of thousands of barrels) may be forced 

out of the well and deposited on the seafloor near the well site. Any organisms beneath heavy layers of 

the extruded drilling mud would be buried. Base fluids of drilling muds are designed to be low in toxicity 

and biodegradable in offshore marine sediments (Neff et al., 2000). However, as bacteria and fungi break 

down the drilling fluids, the sediments may temporarily become anoxic (Neff et al., 2000). Benthic 

macrofaunal recovery would occur when drilling mud concentrations are reduced to levels that enable the 

sediment to become re-oxygenated (Neff et al., 2000). Complete community recovery from drilling mud 

exposure may take 3-5 years, although microbial degradation of drilling fluids, followed by an influx of 

tolerant opportunistic species, is anticipated to begin almost immediately (Neff et al., 2000). In addition, 

the extruded mud may bury hydrocarbons from the well, making them a hazard to the infaunal species 

and difficult to remove. 

Phase 3—Onshore Contact

There would likely be no additional adverse impacts to soft bottom benthic communities as a result of 

events and the potential impact producing factors that could occur throughout Phase 3 of a catastrophic 

spill because these soft bottom benthic communities are located below the water line.

Phase 4—Post-Spill, Long-Term Recovery and Response 

Benthic Habitats

In situations where soft bottom infaunal communities are negatively impacted, recolonization by 

populations from neighboring soft bottom substrate would be expected over a relatively short period. 

Recolonization would begin with recruitment and immigration of opportunistic species from surrounding 

stocks. More complex communities would follow with time. Repopulation could take longer for areas 

affected by direct oil contact in higher concentrations. 

Many of the organisms on soft bottoms live within the sediment and have the ability to migrate 

upward in response to burial by sedimentation. A blowout that occurs outside the well casing can rapidly 

deposit 30 cm (12 in) or more of sediment within a few hundred meters and may smother much of the soft 

bottom community in a localized area. In situations where soft bottom infaunal communities are 

negatively impacted, recolonization by populations from neighboring soft bottom substrate would be 

expected over a relatively short period of time for all size ranges of organisms, in a matter of days for 

bacteria, and probably less than 1 year for most macrofauna and megafauna species. Recolonization 

could take longer for areas affected by direct contact of concentrated oil. Initial repopulation from nearby 

stocks of pioneering species, such as tube-dwelling polychaetes or oligochaetes, may begin with the next 
B-60 Central Planning Area Lease Sale 247 Supplemental EIS

recruitment event (Rhodes and Germano, 1982). Full recovery would follow as later stages of 

successional communities overtake the pioneering species (Rhodes and Germano, 1982). The time it 

takes to reach a climax community may vary depending on the species and degree of impact. Full benthic 

community recovery may take years to decades if the benthic habitat is heavily oiled (Gómez Gesteira 

and Dauvin, 2000; Sanders et al., 1980; Conan, 1982). A slow recovery rate would result in a community 

with reduced biological diversity and possibly a lesser food value for predatory species.

Localized areas of lethal effects would be recolonized by populations from neighboring soft bottom 

substrate once the oil in the sediment has been sufficiently reduced to a level able to support marine life 

(Sanders et al., 1980; Lu and Wu, 2006; Ganning et al., 1984; Gómez Gesteira and Dauvin, 2000; Dean 

and Jewett, 2001). This initial recolonization process may be fairly rapid, but full recovery may take up 

to 10 years depending on the species present, substrate in the area, toxicity of oil spilled, concentration 

and dispersion of oil spilled, and other localized environmental factors that may affect recruitment 

(Kingston et al., 1995; Gómez Gesteira and Dauvin, 2000; Sanders et al., 1980; Conan, 1982). 

Opportunistic species would take advantage of the barren sediment, repopulating impacted areas first. 

These species may occur within the first recruitment cycle of the surrounding populations or from species 

immigration from surrounding stocks and may maintain a stronghold in the area until community 

succession begins (Rhodes and Germano, 1982; Sanders et al., 1980). 

Overall Summary and Conclusion (Phases 1-4) 

A catastrophic blowout and spill would have the greatest impact on the soft bottom benthic 

communities in the immediate vicinity of the spill. Turbidity, sedimentation, and oiling would be 

heaviest closest to the source, and decrease with distance from the source. Complete loss of benthic 

populations may occur with heavy sedimentation and oil deposition. Farther from the well, a less thick 

layer of sediment would be deposited and oil would be dispersed from the source, resulting in sublethal 

impacts. The recovery of benthic populations would begin with recruitment from surrounding areas fairly 

rapidly. 

B.3.1.12. Marine Mammals

Phase 1—Initial Event

Phase 1 of the scenario is the initiation of a catastrophic blowout event. Impacts, response, and 

intervention depend on the spatial location of the blowout and leak. For this analysis, an explosion and 

subsequent fire are assumed to occur. If a blowout associated with the drilling of a single exploratory 

well occurs, this could result in a fire that would burn for 1 or 2 days. If a blowout occurs on a production 

platform, other wells could feed the fire, allowing it to burn for over a month. The drilling rig or platform 

may sink. If the blowout occurs in shallow water, the sinking rig or platform may land in the immediate 

vicinity; if the blowout occurs in deep water, the rig or platform could land a great distance away, beyond 

avoidance zones. Regardless of water depth, the immediate response would be from search and rescue 

vessels and aircraft, such as USCG cutters, helicopters, and rescue planes, and firefighting vessels. 

Potential impacts reflect the explosion, subsequent fire for 1-30 days, and the sinking of the platform in 

the immediate vicinity and up to 1 mi (1.6 km) from the well. 

Depending on the type of blowout, the pressure waves and noise generated by the eruption of gases 

and fluids would likely be significant enough to harass, injure, or kill marine mammals, depending on the 

proximity of the animal to the blowout. A high concentration of response vessels could result in 

harassment or displacement of individuals and could place marine mammals at a greater risk of vessel 

collisions, which would likely cause fatal injuries. 

The scenarios for each phase, including cleanup methods, can be found in Table B-4. 

Phase 2—Offshore Spill

Phase 2 of the analysis focuses on the spill and response in Federal and State offshore waters. A 

catastrophic spill would likely spread hundreds of square miles. Also, the oil slick may break into several 

smaller slicks, depending on local wind patterns that drive the surface currents in the spill area. Potential 

impacts reflect spill and response in Federal and State offshore waters. Season and temperature variations 
Catastrophic Spill Event Analysis B-61

can result in different resource impacts due to variations in oil persistence and oil and dispersant toxicity 

and because of differences in potential exposure of the resources throughout various life cycle stages.

An oil spill and related spill-response activities can impact marine mammals that come into contact 

with oil and remediation efforts. The marine mammals’ exposure to hydrocarbons persisting in the sea 

may result in sublethal impacts (e.g., decreased health, reproductive fitness, longevity, and increased 

vulnerability to disease), some soft tissue irritation, respiratory stress from inhalation of toxic fumes, food 

reduction or contamination, direct ingestion of oil and/or tar, fouling of baleen plates, and temporary 

displacement from preferred habitats or migration routes. More detail on the potential range of effects to 

marine mammals from contact with spilled oil can be found in Geraci and St. Aubin (1990). The best 

available information does not provide a complete understanding of the effects of the spilled oil and 

active response/cleanup activities on marine mammals.

The increased human presence after an oil spill (e.g., vessels) would likely add to changes in behavior 

and/or distribution, thereby potentially stressing marine mammals further and perhaps making them more 

vulnerable to various physiologic and toxic effects. In addition, the large number of response vessels 

could place marine mammals at a greater risk of vessel collisions, which could cause fatal injuries.

The potential biological removal (PBR) level is defined by the Marine Mammal Protection Act as the 

maximum number of animals, not including natural mortalities that may be removed from a marine 

mammal stock while allowing that stock to reach or maintain its optimum sustainable population. 

However, in the Gulf of Mexico, many marine mammal species have unknown PBRs or PBRs with 

outdated abundance estimates, which are considered undetermined. The biological significance of any 

injury or mortality would depend, in part, on the size and reproductive rates of the affected stocks, as well 

as the number, age, and size of the marine mammals affected.

The Deepwater Horizon explosion, oil spill, and response in Mississippi Canyon Block 252 

(including use of dispersants) have impacted marine mammals that have come into contact with oil and 

remediation efforts. According to the “2010 Gulf of Mexico Oil Spill: Sea Turtles, Dolphins, and 

Whales” website, within the designated Deepwater Horizon explosion, oil spill, and response area, 

14 dolphins and whales stranded alive while over 150 dolphins and whales were found dead during the 

oil-spill response (USDOC, NMFS, 2015a). All marine mammals collected either alive or dead were 

found east of the Louisiana/Texas border through Franklin County, Florida. Due to known low-detection 

rates of carcasses, it is possible that the number of deaths of marine mammals is underestimated 

(Williams et al., 2011). It is also important to note that evaluations have not yet confirmed the cause of 

death, and it is possible that many, some, or no carcasses collected were related to the Deepwater Horizon

explosion, oil spill, and response. These stranding numbers are significantly greater than reported in past 

years; though it should be further noted that stranding coverage (i.e., effort in collecting strategies) has 

increased considerably due to the Deepwater Horizon explosion, oil spill, and response. Further detail on 

this catastrophic OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS.

Phase 3—Onshore Contact

Phase 3 focuses on nearshore (e.g., inside bays and in close proximity to shoreline) and onshore spill 

response and oil initially reaching the shoreline during the spill event or while the oil still persists in the 

offshore environment once the spillage has been stopped. It is likely that Phases 2 and 3 could occur 

simultaneously. The duration of the initial shoreline oiling is measured from initial shoreline contact until 

the well is capped or killed and the remaining oil dissipates offshore. Re-oiling of already cleaned or 

previously impacted areas could be expected during Phase 3. In addition to the response described in 

Phase 2, nearshore and onshore efforts would be introduced in Phase 3 as oil entered coastal areas and 

contacted shore. Potential impacts reflect the spill and response in very shallow coastal waters and once 

along the shoreline. Season and temperature variations can result in different resource impacts due to 

variations in oil persistence and oil and dispersant toxicity and because of differences in potential 

exposure of the resources throughout various life cycle stages.

A high-volume oil spill lasting 90 days could directly impact over 22 species of marine mammals. As 

a spill enters coastal waters, manatees and coastal and estuarine dolphins would be the most likely to be 

affected.

Manatees primarily inhabit open coastal (shallow nearshore) areas and estuaries, and they are also 

found far up in freshwater tributaries. Florida manatees have been divided into four distinct regional 

management units: the Atlantic Coast Unit that occupies the east coast of Florida, including the Florida 
B-62 Central Planning Area Lease Sale 247 Supplemental EIS

Keys and the lower St. Johns River north of Palatka, Florida; the Southwest Unit that occurs from Pasco 

County, Florida, south to Whitewater Bay in Monroe County, Florida; the Upper St. Johns River Unit that 

occurs in the river south of Palatka, Florida; and the Northwest Unit that occupies the Florida Panhandle 

south to Hernando County, Florida (Waring et al., 2012). Manatees from the Northwest Unit are more 

likely to be seen in the northern GOM, and they can be found as far west as Texas; however, most 

sightings are in the eastern GOM (Fertl et al., 2005).

During warmer months (June to September), manatees are common along the Gulf Coast of Florida 

from the Everglades National Park northward to the Suwannee River in northwestern Florida. Although 

manatees are less common farther westward, manatee sightings increase during the warmer summer 

months. Winter habitat use is primarily influenced by water temperature as animals congregate at natural 

(springs) and/or artificial (power plant outflows) warm water sources (Alves-Stanley et al., 2010). 

Manatees are infrequently found as far west as Texas (Powell and Rathbun, 1984; Rathbun et al., 1990; 

Schiro et al., 1998). If a catastrophic oil spill reached the Florida coast when manatees were in or near 

coastal waters, the spill could have population-level effects.

It is possible that manatees could occur in coastal areas where vessels traveling to and from the spill 

site could affect them. A manatee present where there is vessel traffic could be injured or killed by a 

vessel strike (Wright et al., 1995). Due to the large number of vessels responding to a catastrophic spill 

both in coastal waters and traveling through coastal waters to the offshore site, manatees would have an 

increased risk of collisions with boats. Vessel strikes are the primary cause of death of manatees.

In February 2014, there were 114 manatee carcasses collected in Florida, 20 of these animals died of 

human causes (Florida Fish and Wildlife Conservation Commission, 2014). Human causes included water 

control structures, entanglement in and ingestion of marine debris, entrapment in pipes/culverts, and 

collisions with watercraft. Seventy percent of the manatees that died of human causes were killed by 

watercraft (Florida Fish and Wildlife Conservation Commission, 2014). Therefore, if a catastrophic spill 

and response vessel traffic occurred near manatee habitats in the eastern Gulf of Mexico, population-level 

impacts could occur because the possibility exists for the number of mortalities to exceed the potential 

biological removal.

There have been no experimental studies and only a few observations suggesting that oil impacts have 

harmed any manatees (St. Aubin and Lounsbury, 1990). Types of impacts to manatees and dugongs from 

contact with oil include (1) asphyxiation because of inhalation of hydrocarbons, (2) acute poisoning 

because of contact with fresh oil, (3) lowering of tolerance to other stress because of the incorporation of 

sublethal amounts of petroleum components into body tissues, (4) nutritional stress through damage to 

food sources, and (5) inflammation or infection and difficulty eating because of oil sticking to the sensory 

hairs around their mouths (Preen, 1989, in Sadiq and McCain, 1993; Australian Maritime Safety 

Authority, 2003). For a population whose environment is already under great pressure, even a localized 

incident could be significant (St. Aubin and Lounsbury, 1990). Spilled oil might affect the quality or 

availability of aquatic vegetation, including seagrasses, upon which manatees feed.

Bottlenose dolphins were the most affected species of marine mammals from the Deepwater Horizon

explosion, oil spill, and response. Bottlenose dolphins can be found throughout coastal waters in the Gulf 

of Mexico. Like manatees, dolphins could be affected, possibly to population level, by a catastrophic oil 

spill if it reaches the coast (as well as affecting them in the open ocean), through direct contact, 

inhalation, ingestion, and stress, as well as through collisions with cleanup vessels. 

Phase 4—Post-Spill, Long-Term Recovery and Response 

Phase 4 focuses on long term recovery once the well has been capped and the spill has stopped. 

During the final phase of a catastrophic blowout and spill, it is presumed that the well has been capped or 

killed and cleanup activities are concluding. While it is assumed that the majority of spilled oil would be 

dissipated offshore within 1-2 months (depending on season and temperature) of stopping the flow, oil 

has the potential to persist in the environment long after a spill event and has been detected in sediment 

30 years after a spill. On sandy beaches, oil can sink deep into the sediments. In tidal flats and salt 

marshes, oil may seep into the muddy bottoms. Potential impacts reflect long term persistence of oil in 

the environment and residual and long term cleanup efforts. 

Even after the spill is stopped, oilings or deaths of marine mammals would still likely occur because 

of oil and dispersants persisting in the water, past marine mammal/oil or dispersant interactions, and 

ingestion of contaminated prey. The animals’ exposure to hydrocarbons persisting in the sea may result 
Catastrophic Spill Event Analysis B-63

in sublethal impacts (e.g., decreased health, reproductive fitness, and longevity; and increased 

vulnerability to disease) and some soft tissue irritation, respiratory stress from inhalation of toxic fumes, 

food reduction or contamination, direct ingestion of oil and/or tar, and temporary displacement from 

preferred habitats or migration routes. A catastrophic oil spill could lead to increased mortalities, 

resulting in potential population-level effects for some species/populations (USDOC, NMFS, 2010a). 

On December 13, 2010, NMFS declared an unusual mortality event (UME) for cetaceans (whales and 

dolphins) in the Gulf of Mexico. An UME is defined under the Marine Mammal Protect Act as a 

“stranding that is unexpected, involves a significant die-off of any marine mammal population, and 

demands immediate response.” Evidence of the UME was first noted by NMFS as early as February 1, 

2010, before the Deepwater Horizon explosion, oil spill, and response. As of November 29, 2015, a total 

of 1,442 cetaceans (6% stranded alive and 94% stranded dead) have stranded since the start of the UME, 

with a vast majority of these strandings between Franklin County, Florida, and the Louisiana/Texas 

border. After the initial response phase ended, there were 15 dolphins killed during a fish-related 

scientific study and one dolphin killed incidental to trawl relocation for a dredging project. More detail 

on the UME can be found on NMFS’s website (USDOC, NMFS, 2015b). 

On May 9, 2012, NOAA declared an UME for bottlenose dolphins in five Texas counties. The cause 

of this UME is unknown and cannot be attributed directly to the Deepwater Horizon explosion, oil spill, 

and response. The strandings were coincident with a harmful algal bloom of Karenia brevis that started 

in September 2011 in southern Texas, but researchers have not determined that was the cause of the 

event. The UME lasted from November 2011-March 2012, when 126 bottlenose dolphins stranded in 

Aransas, Calhoun, Kleberg, Galveston, and Brazoria Counties in Texas. Of the 126 animals stranded, 

only 4 were found alive. Preliminary findings included infection in the lung, poor body condition, 

discoloration of the teeth, and in four animals, a black/grey, thick mud-like substance in the stomachs was 

found. Currently, there are no red tide blooms occurring in the region, and stranding rates have returned 

to normal levels (USDOC, NMFS, 2015c). 

Overall Summary and Conclusion (Phases 1-4) 

Accidental events related to the CPA proposed action have the potential to have adverse, but not 

significant impacts to marine mammal populations in the GOM. Accidental blowouts, oil spills, and 

spill-response activities may impact marine mammals in the GOM. Characteristics of impacts (i.e., acute 

vs. chronic impacts) depend on the magnitude, frequency, location, and date of accidents; characteristics 

of spilled oil; spill-response capabilities and timing; and various meteorological and hydrological factors.

B.3.1.13. Sea Turtles

Phase 1—Initial Event

Phase 1 of the scenario is the initiation of a catastrophic blowout incident. Impacts, response, and 

intervention depend on the spatial location of the blowout and leak. For this analysis, an explosion and 

subsequent fire are assumed to occur. If a blowout associated with the drilling of a single exploratory 

well occurs, this could result in a fire that would burn for 1-2 days. If a blowout occurs on a production 

platform, other wells could feed the fire, allowing it to burn for over a month. The drilling rig or platform 

may sink. If the blowout occurs in shallow water, the sinking rig or platform may land in the immediate 

vicinity; if the blowout occurs in deep water, the rig or platform could land a great distance away, beyond 

avoidance zones. Regardless of water depth, the immediate response would be from search and rescue 

vessels and aircraft, such as USCG cutters, helicopters, and rescue planes, and firefighting vessels. 

Potential impacts reflect the explosion, subsequent fire for 1-30 days, and the sinking of the platform in 

the immediate vicinity and up to 1 mi (1.6 km) from the well. 

Five species of sea turtles are found in the waters of the Gulf of Mexico: green, leatherback, 

hawksbill, Kemp’s ridley, and loggerhead. All species are protected under the Endangered Species Act 

(ESA), and all are listed as endangered except the loggerhead turtle, which is listed as threatened. 

Depending on the type of blowout, an eruption of gases and fluids may generate significant pressure 

waves and noise that may harass, injure, or kill sea turtles, depending on their proximity to the accident. 

A high concentration of response vessels could place sea turtles at a greater risk of fatal injuries from 

vessel collisions. All sea turtle species and life stages are vulnerable to the harmful effects of oil through 

direct contact or by fouling of their habitats and prey. 
B-64 Central Planning Area Lease Sale 247 Supplemental EIS

Further, mitigation by burning puts turtles at risk because they tend to be gathered up in the corralling 

process necessary to concentrate the oil in preparation for the burning. Trained observers should be 

required during any mitigation efforts that include burning. The scenarios for each phase, including 

cleanup methods, can be found in Table B-4. 

Phase 2—Offshore Spill

Phase 2 of the analysis focuses on the spill and response in Federal and State offshore waters. A 

catastrophic spill would likely spread hundreds of square miles. Also, the oil slick may break into several 

smaller slicks, depending on local wind patterns that drive the surface currents in the spill area. Potential 

impacts reflect spill and response in Federal and State offshore waters. Season and temperature variations 

can result in different resource impacts due to variations in oil persistence and oil and dispersant toxicity 

and because of differences in potential exposure of the resources throughout various life cycle stages.

Sea turtles are more likely to be affected by a catastrophic spill in shallow water than in deep water 

because not all sea turtles occupy a deepwater habitat. For example, Kemp’s ridley sea turtles are 

unlikely to be in water depths of 160 ft (49 m) or greater. Hawksbill sea turtles are commonly associated 

with coral reefs, ledges, caves, rocky outcrops, and high energy shoals. Green sea turtles are commonly 

found in coastal benthic feeding grounds, although they may also be found in the convergence zones of 

the open ocean. Convergence zones are areas that also may collect oil. Leatherback sea turtles are 

commonly pelagic and are the sea turtle species most likely to be affected by a deepwater oil spill. As the 

spilled oil moves toward land, additional species of sea turtles are more likely to be affected.

The Deepwater Horizon explosion, oil spill, and response in Mississippi Canyon Block 252 

(including use of dispersants) have impacted sea turtles that have come into contact with oil and 

remediation efforts. For the latest available information on oiled or affected sea turtles documented in the 

area, refer to NMFS’s “2010 Gulf of Mexico Oil Spill: Sea Turtles, Dolphins, and Whales” website 

(USDOC, NMFS, 2014a).

According to this NMFS website, approximately 450 sea turtles were collected, rehabilitated, and 

released back into the wild and over 600 turtles were found dead during the Deepwater Horizon response 

as of October 10, 2014. Of these, about 75 percent of the deceased turtles were Kemp’s ridley turtles and 

95 percent of the released turtles were loggerhead sea turtles (USDOC, NMFS, 2014a). Individuals were 

documented either through strandings or directed offshore captures. Due to low detection rates of 

carcasses in prior events, it is possible that the number of deaths of sea turtles is underestimated (Epperly 

et al., 1996). It is also important to note that evaluations have not yet confirmed the cause of death, and it 

is possible that not all carcasses were related to the Deepwater Horizon explosion, oil spill, and response. 

Over the last 5 years, NOAA has documented increased numbers of sea turtle strandings in the northern 

GOM. Many of the stranded turtles were reported from Mississippi and Alabama waters, and very few 

showed signs of external oiling (believed to be related to the Deepwater Horizon explosion, oil spill, and 

response). Necropsy results from many of the stranded turtles indicate mortality due to forced 

submergence, which is commonly associated with fishery interactions. Further detail on this catastrophic 

OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS. 

The Ixtoc I well blowout and spill in the Bay of Campeche, Mexico, on June 3, 1979, resulted in the 

release of 500,000 metric tons (140 million gallons) of oil and the transport of this oil into the Gulf of

Mexico (ERCO, 1982). Three million gallons of oil impacted Texas beaches (ERCO, 1982). According 

to the ERCO study, “Whether or not hypoxic conditions could, in fact, be responsible for areawide 

reductions in [invertebrate] faunal abundance is unclear, however.” Of the three sea turtles found dead in 

the U.S., all had petroleum hydrocarbons in the tissues examined, and there was selective elimination of 

portions of this oil, indicating chronic exposure (Hall et al., 1983). Therefore, the effects of the Ixtoc I

well blowout and spill on sea turtles in waters off Texas are still unknown.

Phase 3—Onshore Contact

Phase 3 focuses on nearshore (e.g., inside bays and in close proximity to shoreline) and onshore spill 

response, and on oil initially reaching the shoreline during the spill event or while the oil still persists in 

the offshore environment once the spillage has been stopped. It is likely that Phases 2 and 3 could occur 

simultaneously. The duration of the initial shoreline oiling is measured from initial shoreline contact until 

the well is capped or killed and the remaining oil dissipates offshore. The re-oiling of already cleaned or 
Catastrophic Spill Event Analysis B-65

previously impacted areas could be expected during Phase 3. In addition to the response described in 

Phase 2, nearshore and onshore efforts would be introduced in Phase 3 as oil entered coastal areas and 

contacted shore. Potential impacts reflect the spill and response in very shallow coastal waters and once 

along the shoreline. Season and temperature variations can result in different resource impacts due to 

variations in oil persistence and oil and dispersant toxicity and because of differences in potential 

exposure of the resources throughout various life cycle stages.

Out of the five species of sea turtle that occur in the Gulf of Mexico, only four nest in the GOM. The 

largest nesting location for the Kemp’s ridley sea turtle is in Rancho Nuevo, Mexico, but they also nest in 

Texas and Alabama. Loggerhead sea turtles nest in all states around the Gulf of Mexico. Green sea 

turtles have been cited nesting in Texas, Alabama, and Florida. Leatherback sea turtles mostly nest on the 

east coast of Florida but are recorded in Texas. Kemp’s ridley, loggerhead, and green sea turtles are 

therefore most likely to be affected by a catastrophic oil spill when there is onshore and/or offshore 

contact. 

Several recent reports are available concerning Gulf of Mexico loggerheads’ nesting habitats and 

movements (Hart et al., 2013); post-nesting behavior (Foley et al., 2013); foraging sites (Foley et al., 

2014); and body size effects on growth rates (Bjorndal et al., 2013). These reports confirm the 

importance of Gulf of Mexico beaches, specifically for loggerheads. On September 22, 2011, NMFS 

issued the final rule to list 9 Distinct Population Segments (DPSs) of loggerhead sea turtles under the 

ESA and designated the GOM as the Northwest Atlantic Ocean DPS (Federal Register, 2011).

Female sea turtles seasonally emerge during the warmer summer months to nest on beaches. 

Thousands of sea turtles nest along the Gulf Coast, and turtles could build nests on oiled beaches. Nests 

could also be disturbed or destroyed by cleanup efforts. Untended booms could wash ashore and become 

a barrier to sea turtle adults and hatchlings (USDOC, NOAA, 2010c). Hatchlings, with a naturally high 

mortality rate, could traverse the beach through oiled sand and swim through oiled water to reach 

preferred habitats of Sargassum floats. Response efforts could include mass movement of eggs from 

hundreds of nests or thousands of hatchlings from Gulf Coast beaches to the east coast of Florida or to the 

open ocean to prevent hatchlings entering oiled waters (Jernelöv and Lindén, 1981; USDOI, FWS, 

2010b). Due to poorly understood mechanisms that guide female sea turtles back to the beaches where 

they hatched, it is uncertain if relocated hatchlings would eventually return to the Gulf Coast to nest 

(Florida Fish and Wildlife Conservation Commission, 2010). Therefore, shoreline oiling and response 

efforts may affect future population levels and reproduction (USDOI, NPS, 2010). Sea turtle hatchling 

exposure to, fouling by, or consumption of tarballs persisting in the sea following the dispersal of an oil 

slick would likely be fatal. 

As a preventative measure during the Deepwater Horizon explosion, oil spill, and response, NMFS 

and FWS translocated a number of sea turtle nests and eggs that were located on beaches affected or 

potentially affected by spilled oil. The NMFS stranding network website (USDOC, NMFS, 2014a) 

translocated a total of 275 nests from GOM beaches to the east coast of Florida. These nests were mainly 

for hatchlings that would enter waters off Alabama and Florida’s northwest Gulf Coast. The translocation 

effort ended August 19, 2010, at the time when biologists determined that risks to hatchlings emerging 

from beaches and entering waters off Alabama and Florida’s northwest Gulf Coast had diminished 

significantly and that the risks of translocating nests during late incubation to the east coast of Florida 

outweighed the risks of letting hatchlings emerge into the Gulf of Mexico. The hatchlings resulting from 

the translocations were all released as of September 9, 2010.

In addition to the impacts from direct contact with hydrocarbons, spill-response activities could 

adversely affect sea turtle habitat and cause displacement from suitable habitat to inadequate areas. 

Impacting factors might include artificial lighting from night operations, booms, machine and human 

activity, equipment on beaches and in intertidal areas, sand removal and cleaning, and changed beach 

landscape and composition. Some of the resulting impacts from cleanup could include interrupted or 

deterred nesting behavior, crushed nests, entanglement in booms, and increased mortality of hatchlings 

because of predation during the increased time required to reach the water (Newell, 1995; Lutcavage 

et al., 1997). The strategy for cleanup operations should vary, depending on the season.

Phase 4—Post-Spill, Long-Term Recovery and Response 

Phase 4 focuses on long-term recovery once the well has been capped and the spill has stopped. 

During the final phase of a catastrophic blowout and spill, it is presumed that the well has been capped or 
B-66 Central Planning Area Lease Sale 247 Supplemental EIS

killed and that cleanup activities are concluding. While it is assumed that the majority of spilled oil 

would be dissipated offshore within 1-2 months (depending on season and temperature) of stopping the 

flow, oil has the potential to persist in the environment long after a spill event and has been detected in 

sediment 30 years after a spill. On sandy beaches, oil can sink deep into the sediments. In tidal flats and 

salt marshes, oil may seep into the muddy bottoms. Potential impacts reflect long-term persistence of oil 

in the environment and residual and long-term cleanup efforts.

Sea turtles take many years to reach sexual maturity. Green sea turtles reach maturity between 20 and 

50 years of age; loggerheads may be 35 years old before they are able to reproduce; and hawksbill sea 

turtles typically reach lengths of 27 in (69 cm) for males and 31 in (79 cm) for females before they can 

reproduce (USDOC, NMFS, 2010a). Declines in the food supply for sea turtles, which include 

invertebrates and sponge populations, could also affect sea turtle populations. While all of the pathways 

that an oil spill or the use of dispersants can affect sea turtles is poorly understood, some pathways may 

include the following: (1) oil or dispersants on the sea turtle’s skin and body can cause skin irritation, 

chemical burns, and infections; (2) inhalation of volatile petroleum compounds or dispersants can damage 

the respiratory tract and lead to diseases; (3) ingesting oil or dispersants may cause injury to the 

gastrointestinal tract; and (4) chemicals that are inhaled or ingested may damage internal organs. In most 

foreseeable cases, exposure to hydrocarbons persisting in the sea following the dispersal of an oil slick 

would result in sublethal impacts (e.g., decreased health, reproductive fitness, and longevity and increased 

vulnerability to disease) to sea turtles. Other possible internal impacts might include harm to the liver, 

kidney, and brain function, as well as causing anemia and immune suppression, or they could lead to 

reproductive failure or death. The deaths of subadult and adult sea turtles may also drastically reduce the 

population. 

Since January 1, 2011, a notable increase in sea turtle strandings has occurred in the northern GOM, 

primarily in Mississippi. While turtle strandings in this region typically increase in the spring, the recent 

increase is a cause for concern. The Sea Turtle Stranding and Salvage Network is monitoring and 

investigating this increase. The network encompasses the coastal areas of the 18 states from Maine 

through Texas and includes portions of the U.S. Caribbean. There are many possible reasons for the 

increase in strandings in the northern GOM, both natural and human caused (USDOC, NMFS, 2014a). 

One sea turtle had a small amount of tar from the Deepwater Horizon explosion, oil spill, and response on 

its shell. No visible external or internal oil was observed in any other animals. These sea turtle species 

include loggerhead, green, Kemp’s ridley, leatherback, hawksbill, and unidentified. The NMFS has also 

identified strandings in Texas (upper Texas coast—Zone 18). Refer to Chapter 4.1.1.12 for updated 

turtle stranding data for the Gulf of Mexico. 

Overall Summary and Conclusion (Phases 1-4) 

Accidental blowouts, oil spills, and spill-response activities resulting from the CPA proposed action 

have the potential to impact small to large numbers of sea turtles in the GOM, depending on the 

magnitude and frequency of accidents, the ability to respond to accidents, the location and date of 

accidents, and various meteorological and hydrological factors. Impacts on sea turtles from smaller 

accidental events are likely to affect individual sea turtles in the spill area, but they are unlikely to rise to

the level of population effects (or significance) given the size and scope of such spills.

Unavailable information on the effects to sea turtles from the Deepwater Horizon explosion, oil spill, 

and response and increased stranding events (and thus changes to the sea turtle baseline in the affected 

environment) makes an understanding of the effects less clear.

For low-probability catastrophic spills, this analysis concludes that there is a potential for a lowprobability catastrophic event to result in significant, population-level effects on affected sea turtle 

species.

B.3.1.14. Diamondback Terrapins

Phase1—Initial Event

Phase 1 of the scenario is the initiation of a catastrophic blowout event. Impacts, response, and 

intervention depend on the spatial location of the blowout and leak. For this analysis, an explosion and 

subsequent fire are assumed to occur. If a blowout associated with the drilling of a single exploratory 

well occurs, this could result in a fire that would burn for 1-2 days. If a blowout occurs on a production 
Catastrophic Spill Event Analysis B-67

platform, other wells could feed the fire, allowing it to burn for over a month. The drilling rig or platform 

may sink. If the blowout occurs in shallow water, the sinking rig or platform may land in the immediate 

vicinity; if the blowout occurs in deep water, the rig or platform could land a great distance away, beyond 

avoidance zones. Regardless of water depth, the immediate response would be from search and rescue 

vessels and aircraft, such as USCG cutters, helicopters, and rescue planes, and firefighting vessels. 

Potential impacts reflect the explosion, subsequent fire for 1-30 days and the sinking of the platform in 

the immediate vicinity and up to 1 mi (1.6 km) from the well. 

The scenarios for each phase, including cleanup methods, can be found in Table B-4. 

There would likely be no adverse impacts to diamondback terrapins as a result of the events and the 

potential impact-producing factors that could occur throughout Phase 1 of a catastrophic spill event 

because these species exclusively inhabit estuarine waters and salt marshes. 

Phase 2—Offshore Spill

Phase 2 of the analysis focuses on the spill and response in Federal and State offshore waters. A 

catastrophic spill would likely spread hundreds of square miles. Also, the oil slick may break into several 

smaller slicks, depending on local wind patterns that drive the surface currents in the spill area. Potential 

impacts reflect spill and response in Federal and State offshore waters. Season and temperature variations 

can result in different resource impacts due to variations in oil persistence and oil and dispersant toxicity 

and because of differences in potential exposure of the resources throughout various life cycle stages.

There would likely be no adverse impacts to diamondback terrapins as a result of the events and the 

potential impact-producing factors that could occur throughout Phase 2 of a catastrophic spill event 

because these species exclusively inhabit estuarine waters and salt marshes. 

Phase 3—Onshore Contact

Phase 3 focuses on nearshore (e.g., inside bays and in close proximity to shoreline) and onshore spill 

response and on oil initially reaching the shoreline during the spill event or while the oil still persists in 

the offshore environment once the spillage has been stopped. It is likely that Phases 2 and 3 could occur 

simultaneously. The duration of the initial shoreline oiling is measured from initial shoreline contact until 

the well is capped or killed and the remaining oil dissipates offshore. The re-oiling of already cleaned or 

previously impacted areas could be expected during Phase 3. In addition to the response described in 

Phase 2, nearshore and onshore efforts would be introduced in Phase 3 as oil entered coastal areas and 

contacted shore. Potential impacts reflect the spill and response in very shallow coastal waters and once 

along the shoreline. Season and temperature variations can result in different resource impacts due to 

variations in oil persistence and oil and dispersant toxicity and because of differences in the potential 

exposure of the resources throughout various life cycle stages.

The major impact-producing factors resulting from the low-probability catastrophic event at may 

affect the five terrapin subspecies that occur in the CPA include offshore and coastal oil spills and spillresponse activities.

Terrapins inhabit brackish waters including coastal marshes, tidal flats, creeks, and lagoons behind 

barrier beaches (Hogan, 2003). Their diet consists of fish, snails, worms, clams, crabs, and marsh plants 

(Cagle, 1952). Courtship and mating occur in March and April, and the nesting season extends through 

July, with possibly multiple clutches (U.S. Dept. of the Army, COE, 2002; Butler et al., 2006). Terrapins 

nest on dunes, beaches, sandy edges of marshes, islands, and dike roads (Roosenburg, 1994). The 

common factor for proper egg development is sandy soil, which does not clog eggshell pores, thus 

allowing sufficient gas exchange between the developing embryo and the environment (Roosenburg, 

1994). Nesting occurs primarily in the daytime during high tide on high sand dunes with gentle slopes 

and minimal vegetation (Burger, 1977). Clutch size ranges from 4 to 22 eggs, and incubation time ranges 

from 61 to 104 days (Butler et al., 2006; Burger, 1977). Female terrapins may nest 2-3 times in the same 

nesting season. Gender determination is temperature dependent. Hatching occurs from July through 

October in northeastern Florida (Butler et al., 2004). 

Spending most of their lives at the aquatic-terrestrial boundary in estuaries, terrapins are susceptible 

to habitat destruction from oil-spill cleanup efforts as well as direct contact with oil. However, most 

impacts cannot be quantified at this time. Even after oil is no longer visible, terrapins may still be 

exposed while they forage in the salt marshes lining the edges of estuaries, where oil may have 
B-68 Central Planning Area Lease Sale 247 Supplemental EIS

accumulated under the sediments and within the food chain. Terrapin nests can also be disturbed or 

destroyed by cleanup efforts. The range of the possible chronic effects from contact with oil and 

dispersants include lethal or sublethal oil-related injuries that may include skin irritation from the oil or 

dispersants, respiratory problems from the inhalation of volatile petroleum compounds or dispersants, 

gastrointestinal problems caused by the ingestion of oil or dispersants, and damage to other organs 

because of the ingestion or inhalation of these chemicals.

Accidental blowouts, oil spills, and spill-response activities resulting from the CPA proposed action 

have the potential to impact small to large numbers of terrapins within their habitat, depending on the 

magnitude and frequency of accidents, the ability to respond to accidents, the location and date of 

accidents, and various meteorological and hydrological factors. Populations of terrapins in the Gulf may 

be exposed to residuals of oils spilled as a result of the CPA proposed action during their lifetimes. 

Chronic or acute exposure may result in the harassment, harm, or mortality to terrapins occurring in the 

GOM. In the most likely scenarios, exposure to hydrocarbons persisting within the wetlands following 

the dispersal of an oil slick could result in sublethal impacts (e.g., decreased health, reproductive fitness, 

and longevity; and increased vulnerability to disease). Terrapin hatchling exposure to, fouling by, or 

consumption of tarballs persisting inland following the dispersal of an oil slick could likely be fatal but 

unlikely. Impacts from the dispersants are unknown, but they may have similar irritants to tissues and 

sensitive membranes as are known to occur in seabirds and sea turtles (NRC, 2005). The impacts to 

diamondback terrapins from chemical dispersants could include nonlethal injury (e.g., tissue irritation and 

inhalation), long-term exposure through bioaccumulation, and potential shifts in distribution from some 

habitats. 

Burger (1994) described the behavior of 11 female diamondback terrapins that were oiled during the 

January 1990 spill of No. 2 fuel oil in Arthur Kill, New York. The terrapins were hibernating at the time 

of the spill, and when they emerged from hibernation, they were found to be oiled. The terrapins voided 

oil from their digestive tracks for 2 weeks in rehabilitation. At 3 weeks, the terrapins scored low on 

strength tests and were slow to right themselves when placed on their backs. At 4 weeks, they developed 

edema and appetite suppression. Eight of the 11 died; these animals had traces of oil in their tissues and 

exhibited lesions in their digestive tract consistent with oil exposure (Burger, 1994). Further detail on this 

catastrophic OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS. 

The Deepwater Horizon explosion, oil spill, and response may have potentially impacted the terrapin 

community. Impacts from a catastrophic spill may impact terrapin communities. Impacts can be either 

direct (mortality or injury) or indirect (e.g., reduced prey availability); however, most impacts cannot be 

quantified at this time. The best available information does not provide a complete understanding of the 

effects of the spilled oil and active response/cleanup activities on the potentially affected terrapin 

environment. Current available information includes photographic evidence of one terrapin found oiled 

on Grand Terre Island, Louisiana, on June 8, 2010 (State of Louisiana, Coastal Protection and 

Restoration, 2012). 

Phase 4—Post-Spill, Long-Term Recovery and Response 

Phase 4 focuses on long term recovery once the well has been capped and the spill has stopped. 

During the final phase of a catastrophic blowout and spill, it is presumed that the well has been capped or 

killed and cleanup activities are concluding. While it is assumed that the majority of spilled oil would be 

dissipated offshore within 1-2 months (depending on season and temperature) of stopping the flow, oil 

has the potential to persist in the environment long after a spill event and has been detected in sediment 

30 years after a spill. On sandy beaches, oil can sink deep into the sediments. In tidal flats and salt 

marshes, oil may seep into the muddy bottoms. Potential impacts reflect long term persistence of oil in 

the environment and residual and long-term cleanup efforts.

The Deepwater Horizon explosion, oil spill, and response and associated oil spill may have impacted 

the terrapin community and associated brackish habitats. According to OSAT-2 (2011a), possible 

environmental effects from the Deepwater Horizon explosion, oil spill, and response could occur within 

terrapin marsh habitat via food or to nesting habitat since no active intervention (natural remediation) is 

the preferred protocol.

Behavioral effects and nonfatal exposure to or intake of OCS oil- and gas-related contaminants or 

discarded debris may stress and/or weaken individuals of a local group or population and predispose them 

to infection from natural or anthropogenic sources. Even after the oil is no longer visible, terrapins may 
Catastrophic Spill Event Analysis B-69

still be exposed while they forage in the salt marshes lining the edges of estuaries where oil may have 

accumulated under the sediments and within the food chain (Burger, 1994; Roosenburg et al., 1999). 

Nests can also be disturbed or destroyed by cleanup efforts. Through NRDA, ongoing research and 

analysis of the presence of contaminants in terrapin eggs following the Deepwater Horizon oil spill is 

being conducted (USDOC, NOAA, 2012a). Hatching success studies at various oiled nesting sites of the 

northern diamondback terrapin suggest that spills may result in a reduction in nest size and increased 

mortality of spring emergers (hatched turtles) at the oiled sites (Wood and Hales, 2001). However, 

research on the PAH exposure and toxicology of eggs in the vicinity of a spill site found no correlation to 

substrate PAHs when compared with egg toxicology. The level of PAHs found in the eggs may be the 

result of maternal transfer and represent the exposure level of the nesting female rather than 

environmental exposure to PAHs from oil at the site of the nest (Holliday et al., 2008).

Habitat destruction, road construction, drowning in crab traps, and nest predation are the most recent 

threats to diamondback terrapins. Tropical storms, hurricanes, and beach erosion threaten their preferred 

nesting habitats. Destruction of the remaining habitat because of a catastrophic spill and response efforts 

could drastically affect future population levels and reproduction. 

Overall Summary and Conclusion (Phases 1-4) 

Impacts on diamondback terrapins from smaller accidental events are likely to affect individual 

diamondback terrapins in the spill area, as described above, but are unlikely to rise to the level of 

population effects (or significance) given the probable size and scope of such spills. Possible catastrophic 

environmental effects from an oil spill and cleanup could occur within terrapin marsh habitat via food or 

to the nesting habitat. Since terrapins do not move far from where they are hatched, it is possible that 

entire subpopulations could incur high mortality rates and community disruptions, though this would be 

highly localized depending on the time, place, and size of the spill. 

The OSRA analyses in this Supplemental EIS conclude that there is a low probability for catastrophic 

spills and that there is a potential for a low-probability catastrophic event to result in significant, 

population-level effects on affected diamondback terrapin species.

For those terrapin populations that may not have been impacted by the Deepwater Horizon explosion, 

oil spill, and response, it is unlikely that a future accidental event related to the CPA proposed action 

would result in significant impacts due to the distance of most terrapin habitat from offshore OCS energyrelated activities.

B.3.1.15. Beach Mice

Phase 1—Initial Event

There would likely be no adverse impacts to beach mice as a result of the events and the potential 

impact-producing factors that could occur throughout Phase 1 of a catastrophic spill event because 

Phase 1 is the initiation of a catastrophic blowout incident, and initiation would occur well offshore from 

beach mouse habitat.

Phase 2—Offshore Spill

There would likely be no adverse impacts to beach mice as a result of the events and the potential 

impact-producing factors that could occur throughout Phase 2 of a catastrophic spill event because 

Phase 2 of the analysis focuses on the spill and response in Federal and State offshore waters away from 

beach mouse habitat.

Phase 3—Onshore Contact

Five subspecies of the field mouse, collectively known as beach mice, live along the Gulf Coast, and 

two beach mouse subspecies live on the Atlantic Coast of Florida. Five subspecies of beach mice 

(Alabama, Perdido Key, Choctawhatchee, St. Andrew, and Anastasia Island) are listed as State and 

federally endangered; also, the southeastern beach mouse is listed as federally threatened. Beach mice are 

restricted to the coastal barrier sand dunes along the Gulf Coasts of Alabama and Florida. Erosion caused 

by the loss of vegetation because of oiling would likely cause more damage than the direct oiling of beach 
B-70 Central Planning Area Lease Sale 247 Supplemental EIS

mice because of the degradation or loss of habitat. In addition, vehicular traffic and activity associated 

with cleanup can trample or bury beach mice nests and burrows or cause displacement from preferred 

habitat. Improperly trained personnel and vehicle and foot traffic during shoreline cleanup of a 

catastrophic spill would disturb beach mouse populations and would degrade or destroy habitat. 

The Alabama, Choctawhatchee, St. Andrew, Perdido Key, Anastasia Island, and southeastern beach 

mice are designated as protected species under the Endangered Species Act, mostly because of the loss 

and fragmentation of coastal habitat (Federal Register, 1989; USDOI, MMS, 2007). Some of the 

subspecies have coastal habitat that is designated as their critical habitat. For example, the endangered 

Alabama beach mouse’s (Peromyscus polionotus ammobates) designated critical habitat is 1,211 acres 

(450 hectares) of frontal dunes covering just 10 mi (16 km) of shoreline (USDOI, FWS, 2007). Critical 

habitat is the specific geographic areas that are essential for the conservation of a threatened or 

endangered species.

All designated critical habitat for beach mice officially extends landward from the mean high water 

line (Federal Register, 2006; USDOI, FWS, 2007). Therefore, spilled oil could contact critical habitat 

even without a concurrent storm surge; contact would require only that the water level would be at mean 

high tide. However, a concurrent storm surge of considerable height would be required to oil the portion 

of the critical habitat substantially landward of the mean high water line (over the tops of the primary, 

secondary, and tertial dunes). With the potential oiling of over 1,000 mi (1,609 km) of shoreline that 

could result from a catastrophic spill event and a concurrent storm surge of considerable height that 

occurs within a close proximity to the critical habitat, there is the potential for the entire critical habitat 

for a subspecies of beach mice to be completely oiled. Thus, destruction of critical habitat because of a 

catastrophic spill, a concurrent storm surge of considerable height and over a considerable length of 

shoreline, and cleanup activities would increase the threat of extinction of several subspecies of beach

mice. Further detail on this catastrophic OSRA run is contained in Appendix C of the CPA 235/241/247 

Supplemental EIS. 

Phase 4—Post-Spill, Long-Term Recovery and Response 

Within the last 20-30 years, the combination of habitat loss because of beachfront development, the 

isolation of the remaining beach mouse habitat areas and populations, and the destruction of the 

remaining habitat by tropical storms and hurricanes has increased the threat of extinction of several 

subspecies of beach mice. On sandy beaches, oil can sink deep into the sediments and become exposed 

again after erosion of sand by wave action. Oil may therefore persist near beach mouse habitat for the 

long term. The destruction of the remaining habitat because of a catastrophic spill and cleanup activities 

would increase the threat of extinction. 

Overall Summary and Conclusion (Phases 1-4) 

Impacts to beach mice would vary according to the severity of the oiling. Further detail on this 

catastrophic OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS. 

B.3.1.16. Coastal, Marine, and Migratory Birds

Phase 1—Initial Event

Some migratory birds use offshore platforms or rigs as stopover sites during their long-distance 

migrations across the GOM during the spring and fall (Russell, 2005). In addition, it has been well 

documented that seabirds are attracted to offshore platforms and rigs for a myriad of reasons; e.g.., 

concentrations of baitfish, roost sites, etc. (Tasker et al., 1986; Wiese et al., 2001; Burke et al., 2012). 

The numbers of birds present at a platform or rig tend to be greater on platforms or rigs closer to shore, 

particularly during drilling operations (Baird, 1990). Birds resting on the drilling rig or platform during a 

catastrophic blowout at the surface (similar to the Deepwater Horizon explosion, oil spill, and response) 

are more likely to be killed by the explosion. While it is assumed that most birds in trans-Gulf migration 

would likely avoid the fire and smoke plume during the day, it is possible that the light from the fire could 

interfere with nocturnal migration, especially during poor visibility conditions, i.e., fog or low clouds. It 

has been documented that seabirds are attracted to natural gas flares at rigs and platforms (Russell, 2005; 

Wiese et al., 2001); therefore, additional bird fatalities could result from the fire following the blowout. 
Catastrophic Spill Event Analysis B-71

Though different species migrate differentially throughout the year, the largest number of species 

migrates through the proposed area from mid-April through mid-May (spring migration back north) and 

from mid-August through early November (fall migration south) (Russell, 2005, Table 6.12; Farnsworth 

and Russell, 2007). A blowout during this time would potentially result in a greater number of bird 

fatalities (see below).

Of the four phases considered herein, avian mortality associated with this Phase is certainly expected 

to be much lower than avian mortality associated with either Phase 2 or Phase 3. However, this 

anticipated result is highly dependent on the location of the platform and the timing of the event. The 

only scenario considered is the case where a blowout and explosion occurred at the surface (Table B-4). 

If the catastrophic event, in this case a blowout and explosion at the surface (refer to Table B-4), occurs 

more proximal to the coast during the breeding season or during a peak migration period (late March to 

late May and mid-August to early November), then the level of avian mortality is expected to be higher. 

In comparison, a blowout and explosion at the surface on a platform more distant from the coast (greater 

than or equal to the distance of the Macondo well from the coast) would result in much lower avian 

mortality, particularly if the event did not overlap temporally with either the breeding season or either of 

the trans-Gulf migrations.

While the species composition and species-specific mortality estimates are unknown and would be 

dependent on the blowout location and time of year, the initial mortalities would almost certainly not

result in population-level impacts for species present at the time of the blowout and resulting fire (Arnold 

and Zink, 2011; also refer to Table 4-7 of the 2012-2017 WPA/CPA Multisale EIS). If the event occurred 

during the breeding season or wintering period, species of seabirds or diving birds would have the 

greatest potential to be affected, whereas if the event occurred during either the spring or fall migration, 

species of passerines would most likely have the greatest potential to be affected due to the diversity and 

sheer numbers of individuals in this avian species group (Rappole and Ramos, 1994; Lincoln et al., 1998; 

Russell, 2005; also refer to Chapters 4.1.1.16 and 4.2.1.16 of this Supplemental EIS, Chapter 4.2.1.16.1 

of the 2012-2017 WPA/CPA Multisale EIS, Chapter 4.2.1.16 of the WPA 233/CPA 231 Supplemental 

EIS, and Chapter 4.1.1.16 of the CPA 235/241/247 Supplemental EIS). 

Phase 2—Offshore Spill

During Phase 2 of a catastrophic spill, the primary concern for marine and migratory birds would be 

their vulnerability to oiling or ingesting oil, which is primarily a function of their behavior and diets. 

Wading birds (e.g., herons, egrets, etc.) and species that feed by plunge-diving into the water to catch 

small fish (e.g., pelicans, gannets, terns, gulls, and pelagic birds) and those that use water as a primary 

means of locomotion, foraging (e.g., black skimmers), or resting and preening (e.g., diving ducks, 

cormorants, pelicans, etc.) are highly vulnerable to becoming oiled and also to ingesting oil (Table B-5 of 

this Supplemental EIS; also refer to Table 4-13 and Figure 4-13 of the 2012-2017 WPA/CPA Multisale 

EIS). Seabirds, in particular, tend to feed and concentrate in convergence zones, eddies, upwellings, and 

near Sargassum mats (Haney, 1986a-c; Moser and Lee, 2012). In addition to concentrating prey, these 

areas are also known to aggregate oil (Unified Incident Command, 2010d). Oiling interferes with the 

birds’ ability to fly (and thus to obtain food) and compromises the insulative characteristics of down and 

contour feathers, making it difficult to regulate body temperature. Attempts by oiled birds to remove the 

oil via preening can cause them to ingest oil and may result in mortality. In addition, the ingestion of 

contaminated prey can result in physiological impairment and even death. Refer to Chapter 4.2.1.16.3 of 

the 2012-2017 WPA/CPA Multisale EIS for additional detailed information on oiling effects to birds. 

Though several species or species groups are mentioned above, the most vulnerable species to spilled 

oil in the offshore environment in the GOM during Phase 2 would be representatives of the diving bird 

(≤10 species) and seabird (≥20 species) groups (King and Sanger, 1979; Ribic et al., 1997; Davis et al., 

2000). It is highly probable that representative species of diving birds and seabirds would be 

differentially impacted (Table B-5 of this Supplemental EIS; also refer to Table 4-12 of the 2012-2017 

WPA/CPA Multisale EIS). Table 4-12 of the 2012-2017 WPA/CPA Multisale EIS shows the actual 

number of birds identified to the species level for each of the species groups collected after the Deepwater 

Horizon explosion, oil spill, and response. This number is fairly representative of the suite of species 

available to be oiled. Search effort likely declined dramatically once the Macondo well was 

plugged/capped. The species composition and species-specific mortality estimates associated with a 

Phase 2 catastrophic event are unknown and would be dependent primarily on the blowout location, as 
B-72 Central Planning Area Lease Sale 247 Supplemental EIS

well as the distribution, coverage, and proximity to the shoreline of spilled oil. Overall, avian mortalities 

for this Phase would probably not result in population-level impacts for species present at the time of the 

blowout (refer to Table B-5 of this Supplemental EIS and to Figure 4-13 of the 2012-2017 WPA/CPA 

Multisale EIS). However, it should be clear that many species of seabirds and diving birds have lifehistory strategies that do not allow subpopulations to recover quickly from major mortality events or 

perturbations (Ricklefs, 1983 and 1990; Russell, 1999; Saether et al., 2004; also refer to Table 4-13 and 

Figure 4-18 of the 2012-2017 WPA/CPA Multisale EIS). 

Some discussion of available information provided from the Deepwater Horizon explosion, oil spill, 

and response is relevant here with respect to temporal aspects of oiled birds (Figure B-3). The first oiled 

bird (northern gannet, a seabird) recovered after the Macondo well event was collected just 10 days postblowout. While gannets breed in coastal colonies in the Canadian North Atlantic, the population, 

including a major concentration in the northern GOM, over-winters in the deeper waters of the offshore 

environment. Belanger et al. (2010) provided some interesting results relative to live versus dead birds 

collected based on the actual date each bird was collected. Interestingly, they documented a dramatic and 

statistically significant decline in the number of live birds collected after 110 days compared with live 

birds collected during the first 72 days. These authors also documented a dramatic and statistically 

significant increase in the number of dead birds collected after 110 days (Belanger et al., 2010, Figures 2 

and 3). As a temporal reference, oil reached the shoreline near Venice, Louisiana, ≥10 days postblowout, covering a distance of approximately 90 mi (145 km) (Oil Spill Commission, 2011; also refer to 

Chapter 4.2.1.3.1 of the 2012-2017 WPA/CPA Multisale EIS and Chapter 4.2.1.3 of the WPA 233/CPA 

231 Supplemental EIS) (Figure B-3). It should be understood that, for the Phase 2 scenario considered 

here, it is assumed that spilled oil will not contact the shoreline.

Overall, avian mortality estimates are unknown and are difficult to predict given the uncertainty 

(Conroy et al., 2011, pages 1209-1210; Williams, 2011, page 1348) associated with the scenario and 

specific characteristics associated with the spill (refer to Appendix C of the WPA 238/246/248 

Supplemental EIS), as well as environmental conditions that are probably a function of spill location and 

timing. Even recognizing the uncertainty associated with the scenario, spill characteristics, and the 

environmental conditions at the time of the spill, Phase 2 would likely be second only to Phase 3 in total 

avian mortality. Phase 3 would include much greater avian species diversity and abundance due to the oil 

reaching nearshore, coastal beach/dune, salt- and brackish marsh habitats (Table B-5 of this 

Supplemental EIS; also refer to Table 4-12 of the 2012-2017 WPA/CPA Multisale EIS).

Phase 3—Onshore Contact

Gulf coastal habitats are essential to the annual cycles of many species of breeding, wintering, and 

migrating diving birds, seabirds, shorebirds, passerines, marsh- and wading birds, and waterfowl (refer to 

Chapters 4.1.1.16 and 4.2.1.16 of this Supplemental EIS, Chapter 4.2.1.16.1 of the 2012-2017 

WPA/CPA Multisale EIS, Chapter 4.2.1.16 of the WPA 233/CPA 231 Supplemental EIS, and Chapter 

4.1.1.16 of the CPA 235/241/247 Supplemental EIS). For example, the northern Gulf Coast supports a 

large proportion of populations of several beach-nesting bird species (USDOI, FWS, 2010c). During 

Phase 3, oil is expected to contact not only the beach but also other important habitats used by a diverse 

and abundant assemblage of avian species. Habitats potentially impacted by a catastrophic spill would 

also likely include the nearshore environment, as well as the salt- and brackish marsh habitats. Potential 

impacts and total avian mortality from Phase 3 would be greater than any of the other phases considered 

herein due to (1) avian diversity and abundance in the nearshore environment (Table B-5 of this 

Supplemental EIS; also refer to Tables 4-9 through 4-11 of the 2012-2017 WPA/CPA Multisale EIS) and 

(2) the dispersion of oil from a catastrophic spill, which would reach the shoreline and enter the salt- and 

brackish marsh environments. Similar to Phases 1 and 2, the timing and location of the spill are 

important factors in determining the severity of impacts to the avian community. In addition, the duration 

of potential oil exposure to various species of birds would also be important. 

Figure 4-13 of the 2012-2017 WPA/CPA Multisale EIS should provide reasonable estimates of oiling 

rates for the seven avian species groups in the northern Gulf of Mexico if another catastrophic spill were 

to occur and the timing, oil spill characteristics, and spill behavior were similar to the Deepwater Horizon

explosion, oil spill, and response. It should be noted that the top five most impacted (based on number 

collected) avian species from the Deepwater Horizon explosion, oil spill, and response were all 

representatives of the seabird group: laughing gull (n = 2,981, 40% oiling rate); brown pelican (n = 826, 
Catastrophic Spill Event Analysis B-73

41% oiling rate); northern gannet (n = 475, 63% oiling rate); royal tern (n = 289, 52% oiling rate); and 

black skimmer (n = 253, 22% oiling rate) (Table B-5 of this Supplemental EIS and Figure 4-13 of the 

2012-2017 WPA/CPA Multisale EIS).

Additional information is provided from an OSRA catastrophic oil-spill analysis (refer to Appendix C 

of the CPA 235/241/247 Supplemental EIS, Tables C-4 and C-5). 

It should be noted that oil from the Deepwater Horizon explosion and oil spill reached the shoreline 

less than 14 days after the blowout occurred (Oil Spill Commission, 2011). The OSRA does not take into 

account or consider the following with respect to avian resources and their habitats: (1) species-specific 

densities; (2) species-specific habitat preferences, food habits, or behavior; (3) relative vulnerabilities to 

oiling among the avian species groups or among species within each of the groups (Table B-5 of this 

Supplemental EIS and Figure 4-13 of the 2012-2017 WPA/CPA Multisale EIS; also refer to Williams 

et al., 1995; Camphuysen, 2006); and (4) species-specific life-history strategies, their demography, or a 

species’ recovery potential (refer to Table 4-13 and Figures 4-18 and 4-19 of the 2012-2017 WPA/CPA 

Multisale EIS).

In summary, Phase 3 of a catastrophic oil spill has the greatest potential for negative impacts (e.g.., 

direct mortality) to avian resources due to its contact with the shoreline and inundation of other habitats 

occupied by a much greater diversity and abundance of birds, particularly during the breeding season. 

Avian mortality estimates are presently unknown and are difficult to predict with any level of precision 

given the uncertainty associated with the scenario, specific characteristics associated with the spill, spatial 

and temporal variation in environmental conditions, and recognition that the avian resources (both species 

diversity and abundance) available to be oiled will also vary temporally and spatially. A worst-case 

scenario in the event of a catastrophic oil spill that reached the nearshore environment would occur in the 

presence of a hurricane with strength or magnitude similar to Hurricanes Katrina, Rita, or Ike during the 

breeding season. Such an overlap of two low-probability events during the breeding season could 

potentially push spilled oil even farther inland and also distribute oil vertically into the vegetation. Such 

an event would not only negatively impact diving birds, seabirds, shorebirds, marsh- and wading birds, 

and waterfowl, but also the more terrestrial avian species groups including passerines and raptors. Such 

effects would most likely be long-term (due to direct mortality of individuals, but also due to major 

habitat loss) and could potentially result in population-level impacts to a number of avian species. 

Threatened and endangered avian species would likely be the most severely impacted by such an event, 

depending on the spatial and temporal aspects of both the spill and the hurricane. 

Endangered and Threatened Birds 

A detailed discussion of threatened and endangered species is provided for the CPA in Chapter 

4.2.1.16.1 of the 2012-2017 WPA/CPA Multisale EIS. Of the 17 species considered, 11 species are 

known to occur in the CPA (Table B-6). However, only the piping plover (Charadrius melodus), roseate 

tern (Sterna dougallii dougallii), wood stork (Mycteria americana), whooping crane (Grus americana), 

Mississippi sandhill crane (Grus canadensis pulla), bald eagle (Haliaeetus leucocephalus), eastern brown 

pelican (Pelecanus occidentalis), and red knot (Calidris canutus rufa) were analyzed and are considered 

further here. The bald eagle and brown pelican were delisted. Phase 3 would likely result in the greatest 

net negative impacts (primarily direct mortality) to threatened and endangered avian species due to 

contact with the shoreline and potential movement of spilled oil inland to other habitats during this phase 

(Table B-4). In addition, the presence of spilled oil would result in indirect and potentially long-term 

effects to threatened and endangered avian species’ habitats and their preferred foods. Phases 1 and 2 

would likely result in very limited impacts, if any, due to the scenarios as defined with oil restricted to the 

offshore environment. 

In general, the potential direct impact (i.e., mortality) to any or all of these threatened or endangered 

(including recently delisted and candidate) species is directly a function of their presence at the time of a 

catastrophic oil spill. Indirect effects from a catastrophic oil spill could negatively affect the quality and 

functional availability of their habitats and the availability, distribution, and energetic benefits of their 

preferred foods in the absence of a given species. Of the species listed, the wood stork, Mississippi 

sandhill crane, bald eagle, eastern brown pelican, and Cape Sable seaside sparrows are year-round 

residents, whereas the piping plover, roseate tern, whooping crane, and red knot represent either wintering 

species or transients that utilize coastal habitats in the GOM as staging areas during migration. Part of the 

brown pelican population is migratory. There are “resident” whooping cranes considered as 
B-74 Central Planning Area Lease Sale 247 Supplemental EIS

“nonessential, experimental flocks” within the Gulf Coast States of Alabama, Louisiana, Mississippi, and 

Florida. These birds would be considered as “resident,” whereas the component of the ESA-listed species 

occurring primarily as a wintering flock in Texas (i.e., the Aransas National Wildlife Refuge) is 

considered a migratory flock. It is important to recognize these differences relative to whether or not 

individuals of a given species would be present and available to be oiled should a catastrophic oil spill 

event occur. Similarly, species-specific differences in habitat use and behavior would further separate 

which species would be most vulnerable to a spill given the timing of the spill, spill distribution, and 

other spill-related characteristics.

Of the species considered, probably only the eastern brown pelican and possibly the bald eagle 

(ingestion of contaminated fish and birds) would potentially be impacted during Phases 1 and 2. The 

other species are restricted to the nearshore, coastal, salt- and brackish, and upland habitats, which would 

not be impacted during these phases given the scenario (Table B-4). Phase 4 impacts to threatened and 

endangered avian species would probably be limited to short-term disturbance-related effects and 

potential impacts to habitats including destruction, alteration, or fragmentation from associated recovery 

activities (American Bird Conservancy, 2010; National Audubon Society, Inc, 2010). 

As the Macondo well blowout and spill is the only historic catastrophic oil spill to occur in U.S. 

waters in the GOM, the information obtained from the Deepwater Horizon explosion, oil spill, and 

response relative to avian mortality may be reasonably relevant for any future catastrophic spills, 

recognizing of course the variation and uncertainty associated with individual oil spills. Of the threatened 

and endangered avian species considered, only a single, unoiled piping plover was collected as part of the 

post-Deepwater Horizon explosion, oil spill, and response monitoring program (Table B-5). There were 

106 least terns (Sterna antillarum) collected (n = 106, 46% oiling rate), but these individuals were 

considered as members of the coastal breeding population and not the ESA-listed population (Interior or 

noncoastal population). Of the species considered, only the eastern brown pelican was impacted by the 

Deepwater Horizon explosion, oil spill, and response (n = 826, 41% oiling rate); this species was delisted 

on November 17, 2009 (Federal Register, 2009). No other carcasses of threatened and endangered 

species were collected as part of the post-Deepwater Horizon explosion, oil spill, and response

monitoring efforts (Table B-5; USDOI, FWS, 2011a). 

Additional information is provided from an OSRA catastrophic oil-spill analysis (refer to Appendix C 

of the CPA 235/241/247 Supplemental EIS, Tables C-4 and C-5). 

Caveats regarding the OSRA catastrophic run with respect to avian resources were addressed above 

and would also apply to threatened and endangered avian resources considered here. 

Phase 4—Post-Spill, Long-Term Recovery and Response 

There is a high probability of underestimating the impacts of oil spills on avian species potentially 

encountering oil. Despite being oiled, some birds are capable of flight and may later succumb to the 

oiling for a myriad of reasons (refer to Chapter 4.2.1.14 of the 2012-2017 WPA/CPA Multisale EIS for 

additional detailed information). Often overlooked and understudied are the long-term, sublethal, chronic 

effects due to sublethal exposure to oil (Butler et al., 1988; Alonso-Alvarez et al., 2007; Pérez et al., 

2010). Also, individuals having been oiled in the Gulf of Mexico as the result of a catastrophic oil spill 

during the overwinter period or while staging in the GOM could exhibit carry-over effects to the northern 

breeding grounds. Affected individuals in poor body condition may arrive at their breeding grounds later 

than nonaffected individuals, which could, in turn, negatively affect habitat-use decisions, territory 

establishment, pairing success, and ultimately lead to reduced reproductive success (Norris, 2005; Norris 

et al., 2006; Harrison et al., 2011). Some oiled individuals may forego breeding altogether (Zabala et al., 

2010). If oil-affected, long-distance migrants represent important prey items for various species of 

raptors, then the ingestion of affected individuals could also negatively affect individual birds of prey 

(Zuberogoitia et al., 2006). The effects from disturbance due to oil-spill cleanup from the Deepwater 

Horizon explosion were only observed at sites with high cleanup activity, suggesting that the impact of 

oil-spill cleanup on shorebirds may be minimized by limiting cleanup activities to specific areas and times 

of day (Henkel et al., 2014). The types of disturbance analyzed included mechanical cleanup, 

nonmechanical cleanup, and people walking, sometimes with dogs (Henkel et al., 2014). The long-term 

impacts of potential food-induced stress for bird species from an altered ecosystem due to a catastrophic 

spill are unknown, but disturbances to the ecosystem can cause long-term sublethal impacts, including 

reduced food intake, prey switching, increased energy expenditures, decreased reproductive success, and 
Catastrophic Spill Event Analysis B-75

decreased survival. Decreases in either reproductive success or survival (or both) could result in 

population-level effects, as was observed for certain avian species more than 10 years after the Exxon 

Valdez catastrophic spill (Esler et al., 2002 and 2010; Golet et al., 2002). Long-term, sublethal, chronic 

effects may exceed immediate losses (i.e., direct mortality of oiled birds) if residual effects influence a 

significant proportion of the population or disproportionately impact an important aspect of the 

population demographic, e.g.., breeding-age females (Croxall and Rothery, 1991; Oro et al., 2004). 

Depending on the effects and the life-history strategy of impacted species, some populations could take 

years or decades before reaching pre-spill population numbers and age-sex structure; some populations 

for some species may never recover (refer to Figure 4-13 of the 2012-2017 WPA/CPA Multisale EIS; 

refer to Peterson et al., 2003, but also to Wiens et al., 2010).

In general, potential effects associated with Phase 4 should be limited to short-term disturbance

effects (personnel and equipment) and potential indirect effects to various avian species groups due to 

habitat loss, alteration, or fragmentation from restoration efforts. There may be cases whereby incubating 

individuals are flushed from nests exposing their eggs or young to either weather-related mortality or 

depredation by avian or mammalian predators (American Bird Conservancy, 2010; National Audubon 

Society, Inc., 2010). However, efforts to minimize potential effects of post-oil spill monitoring and 

restoration efforts, particularly during the breeding season, should be sufficient to protect nesting birds as 

a function of oversight by Federal and State agencies charged with the conservation of migratory bird 

resources.

Overall, the Deepwater Horizon explosion, oil spill, and response appears to have directly resulted in 

far fewer dead, oiled birds than the Exxon Valdez catastrophic spill. Total seabird mortality from the 

Deepwater Horizon explosion, oil spill, and response is useful knowledge because it gives an indication 

of the baseline shift in population sizes. Total seabird mortality (not a per annum estimate but instead 

accounting for all bird deaths) seaward of 40 km (25 mi) 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 procellariiforms; 9,000 for one pelecaniform; 

and 96,000-500,000 for three charadriiforms (Haney et al., 2014a). Total bird mortality (not a per annum 

estimate but instead accounting for all bird deaths) shoreward of 40 km (25 mi) from shore was estimated 

by two models, culminating in estimates of 600,000 birds using one model and 800,000 birds using the 

other (Haney et al., 2014b). 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 Gulf of Mexico (Haney et al., 2014b). This new information estimates a small 

negative shift in baseline numbers due to the calculated mortality of hundreds of thousands of Gulf of 

Mexico seabirds after the Deepwater Horizon explosion, oil spill, and response. No data are available on 

any recovery since the analyses by Haney et al. (2014a and 2014b), but the initial negative shift was 

insufficient to cause a change in the expected impacts to seabirds from a catastrophic spill.

It should be recognized that the avian-related mortality associated with the Deepwater Horizon

explosion, oil spill, and response (considered a catastrophic event) represents a small fraction of birds 

killed when compared with collisions with offshore oil and gas platforms. Russell (2005, page 304) 

states, “an average Gulf platform may cause 50 deaths by collision [only] per year,” so using this number, 

the number of deaths the Deepwater Horizon rig would have caused through collisions had it remained 

intact for its 40-year term would be about 2,000. That is about 5,258 less than the number of avian 

carcasses collected due to the Deepwater Horizon explosion, oil spill, and response just given above. In 

the GOM, an estimated 200,000-321,000 avian deaths occur annually; primarily due to collisions with 

platforms (Table 4-7 of the 2012-2017 WPA/CPA Multisale EIS; also refer to Russell, 2005). Over the 

life of the GOM platform archipelago, the estimated total avian mortality is on the order of 7-12 million 

birds (refer to Figure 4-15 of the 2012-2017 WPA/CPA Multisale EIS). Oil spills, regardless of size, are 

just one of a myriad of anthropogenic avian mortality sources. No Gulf of Mexico regional estimates are 

available for annual mortality rates for these sources. However, recent quantitative national estimates 

(Loss et al., 2013, 2014a, and 2014b) allow a qualitative but not quantitative extrapolation to the Gulf of 

Mexico. The national estimates include songbirds, and these are relevant because they may be impacted 

during trans-Gulf migration. To give perspective, an estimated range of national annual mortality from 

collision with vehicles is 62-275 million birds per year, national annual mortality from collision with 

buildings is estimated at 599 million birds per year, and annual mortality from predation by free-ranging 

domestic cats is estimated at 1.4-3.7 billion birds per year. These mortality estimates are nationwide, not 

just for the northern Gulf of Mexico; therefore, impacts would be much lower. Loss et al. (2014b) 
B-76 Central Planning Area Lease Sale 247 Supplemental EIS

provide unprecedented state-of-the-art science (Machtans and Thogmartin, 2014) using species-specific 

local mortality estimates and an explicit treatment of known biases with acknowledged uncertainty in the 

final national estimate. These techniques allowed more reasonable extrapolation to total bird mortality on 

a national scale. The innovative estimates by Loss et al. (2014b) were compiled from many previously 

available local studies that were never designed to be used for extrapolation but were successfully used 

for that anyway (Machtans and Thogmartin, 2014).

Overall Summary and Conclusion (Phases 1-4) 

While the species composition and species-specific mortality estimates are unknown and would be 

dependent on the blowout location and time of year, the mortalities for the initial event (Phase 1) would 

almost certainly not result in population-level impacts for species present at the time of the blowout and 

resulting fire. Seabirds are highly vulnerable to becoming oiled and also to ingesting oil during Phase 2 

(the offshore spill). Even recognizing the uncertainty associated with the scenario, spill characteristics, 

and the environmental conditions at the time of the spill, Phase 2 would likely be second only to Phase 3 

(onshore contact) in total avian mortality. Phase 3 would include greater impacts to avian species’ 

richness and abundance (particularly during the breeding season) due to oil reaching habitats, including 

the nearshore, coastal beaches and dunes, and salt and brackish marshes. In general, the potential effects 

associated with Phase 4 (long-term recovery and response) should be limited to short-term disturbance 

effects (by cleanup personnel and equipment) and potential indirect effects to various bird species groups 

from habitat loss, alteration, or fragmentation from restoration efforts.

Phases 1 (initial event) and 2 (offshore spill) would likely result in very limited impacts to threatened 

and endangered bird species because the two scenarios have oil restricted to the offshore environment. 

Phase 3 (onshore contact) would likely result in the greatest net negative impacts to threatened and 

endangered bird species due to contact with the shoreline and potential movement of spilled oil inland to 

other habitats during this phase. 

B.3.1.17. Fish Resources and Essential Fish Habitat

Phase 1—Initial Event

Depending on the type of blowout and the proximity of marine life to it (Table B-1), an eruption of 

gases and fluids may generate not only a toxic effect but also pressure waves and noise significant enough 

to injure or kill local biota. Within a few thousand meters of the blowout, resuspended sediments may 

clog fish gills and interfere with respiration. Settlement of resuspended sediments may, in turn, smother 

invertebrates or interfere with their respiration. Essential fish habitat (EFH) in the vicinity of the blowout 

could have adverse effects from the event. These EFH resources are discussed in the water quality 

(Chapter B.3.1.2), live bottoms (Chapter B.3.1.6), topographic features (Chapter B.3.1.7), Sargassum

communities (Chapter B.3.1.8), chemosynthetic and nonchemosynthetic deepwater benthic communities 

(Chapters B.3.1.9 and B.3.1.10, respectively), and soft bottom benthic communities (Chapter B.3.1.11) 

chapters.

Phase 2—Offshore Spill

With the initiation of a catastrophic blowout incident, an explosion and subsequent fire are assumed 

to occur. If a blowout associated with the drilling of a single exploratory well occurs, this could result in 

a fire that would burn for 1 or 2 days, but if a blowout occurs on a production platform and other wells 

feed the fire, it could burn for over a month. The drilling rig or platform may sink, and if this occurs in 

shallow water, the sinking rig or platform may land in the immediate vicinity. If the blowout occurs in 

deep water, the rig or platform could land a great distance away and could be beyond avoidance zones. 

Regardless of water depth, the immediate response would be from search and rescue vessels and aircraft, 

such as USCG cutters, helicopters, rescue planes, and firefighting vessels.

Early life stages of animals are usually more sensitive to oil than adults (Boesch and Rabalais, 1987; 

NRC, 2005). Weathered crude oil has been shown in laboratory experiments to cause malformation, 

genetic damage, and even mortality at low levels in fish embryos of Pacific herring (Carls et al., 1999). 

Because natural crude oil found in the Gulf of Mexico would generally float on the surface, fish species 

whose eggs and larvae are found at or near the water surface are most at risk from an offshore spill. 
Catastrophic Spill Event Analysis B-77

Species whose spawning periods coincide with the timing of the highest oil concentrations would be at 

greatest risk.

Adult fish may be less at risk than earlier life stages, in part because they are less likely to concentrate 

at the surface and may avoid contact with floating oil. The effects of oil on organisms can include direct 

lethal toxicity, sublethal disruption of physiological processes (internal lesions), the effects from direct 

coating by oil (suffocation by coating gills), incorporation of hydrocarbons in organisms (tainting or 

accumulation in the food chain), and changes in biological habitat (decreased dissolved oxygen) (Moore 

and Dwyer, 1974). The extent of the impacts of the oil would depend on the properties of the oil and the 

time of year of the event.

If there is a subsea catastrophic blowout, it is assumed dispersants would be used. Then there could 

be effects on multiple life history stages and trophic levels. There is limited knowledge of the toxicity of 

dispersants mixed with oil to specific species or life stages of ichthyoplankton and the likely extent of 

mortality because the combination of factors is difficult to determine. The combined toxic effects of the 

oil and any dispersants that may be used would not be apparent unless a significant portion of a year-class 

is absent from next year’s fishery (e.g., shrimps, crabs, snapper, and tuna). An example of a catastrophic 

event in the CPA was modeled using OSRA (Appendix C of the CPA 235/241/247 Supplemental EIS, 

Tables C-4 and C-5). Because fish occur throughout the GOM, it is assumed that some individuals would 

be contacted with oil. Specific habitats that are discussed with regards to the Central Planning Area 

OSRA examples and in the Appendix are water quality (Chapter B.3.1.2), wetlands (Chapter B.3.1.4), 

seagrass communities (Chapter B.3.1.5), live bottoms (Chapter B.3.1.6), topographic features (Chapter 

B.3.1.7), Sargassum communities (Chapter B.3.1.8), chemosynthetic and nonchemosynthetic deepwater 

communities (Chapters B.3.1.9 and B.3.1.10, respectively), and soft bottom benthic communities 

(Chapter B.3.1.11).

Studies by USEPA, Office of Research and Development (2010) using representative species provide 

some indication of the relative toxicity of Louisiana sweet crude oil, dispersants, and oil/dispersant mixes. 

Bioassays were conducted using two Gulf species—a mysid shrimp (Amercamysis bahia) and a small 

estuarine fish, the inland silverside (Menidia beryllinina)—to evaluate the acute toxic effects of oil, eight 

dispersants, and oil/dispersant mixtures. In addition, USEPA used standard in vitro techniques using the 

same dispersants to (1) evaluate the acute toxicity on three cell lines over a range of concentrations and 

(2) evaluate the effects of these dispersants on androgen and estrogen function using human cell lines (to 

see if they are likely to disrupt hormonal systems). All dispersants showed cytotoxicity in at least one cell 

type at concentrations between 10 and 110 ppm. Results of the in vitro toxicity tests were similar to the 

whole animal tests. For all eight dispersants, for both species, the dispersants alone were less toxic than 

the dispersant/oil mixture. Louisiana sweet crude oil alone was determined to be more toxic to both the 

mysid shrimp and silverside fish than the dispersants alone. The results of the testing for disruption of 

androgen and estrogen function indicate that the dispersants do not show biologically significant 

endocrine activity via androgen or estrogen pathways (USEPA, Office of Research and Development, 

2010). 

The GOM waters out to 100 fathoms (182 m; 600 ft) have EFHs described and identified for managed 

species (GMFMC, 2005; USDOC, NOAA, 2009). There are Fisheries Management Plans for shrimp, red 

drum, reef fishes, coastal migratory pelagics, spiny lobsters, coral and coral reefs, and highly migratory 

species (GMFMC, 2004; USDOC, NOAA, 2009). These species could use the GOM for EFH at different 

life history stages. The Highly Migratory Species Fisheries Management Plan was recently amended to 

update EFH and Habitat Areas of Particular Concerns for the Atlantic bluefin tuna spawning area 

(USDOC, NOAA, 2009).

These EFHs in the Gulf of Mexico are discussed in various chapters of this Appendix: water column 

(Chapter B.3.1.2); wetlands (Chapter B.3.1.4); seagrass communities (Chapter B.3.1.5), live bottoms 

(Chapter B.3.1.6); topographic features (Chapter B.3.1.7), Sargassum communities (Chapter B.3.1.8); 

chemosynthetic and nonchemosynthetic deepwater benthic communities (Chapters B.3.1.9 and B.3.1.10, 

respectively), and soft bottom benthic communities (Chapter B.3.1.11); these EFHs are also summarized 

in Appendix D of the 2012-2017 WPA/CPA Multisale EIS. There are current NTLs (NTL 2009-G39 and 

NTL 2009-G40), stipulations, and mitigations that provide guidance and clarification of the regulations 

with respect to many of these biologically sensitive underwater features and areas and benthic 

communities, which are considered EFH.
B-78 Central Planning Area Lease Sale 247 Supplemental EIS

Plankton 

Open-water organisms, such as phytoplankton and zooplankton, are essential to the marine food web. 

They play an important role in regulating climate, contribute to marine snow, and are an important source 

of nutrients for mesopelagic and benthic habitats. Also, monthly ichthyoplankton collections over the 

years 2004-2006 offshore of Alabama have confirmed that peak seasons for ichthyoplankton 

concentrations on the shelf are spring and summer (Hernandez et al., 2010). If a catastrophic blowout 

occurs in the spring and summer, it could cause greater harm to fish populations and not just individual 

fish. Therefore, an offshore oil spill would not only have an impact on these populations but also on the 

species that depend on them. 

The microbial community can also be affected by an offshore oil spill. The microbial loop is an 

essential part of the marine ecosystem. Changes in the microbial community because of an oil spill could 

have significant impacts on the rest of the marine ecosystem. However, several laboratory and field 

experiments and observations have shown that impacts to planktonic and marine microbial populations 

are generally short lived and do not affect all groups evenly, and in some cases stimulate growth of 

important species (Gonzalez et al., 2009; Graham et al., 2010; Hing et al., 2011). 

Phase 3—Onshore Contact

It is estimated that shoreline oiling would last 1-5 months from a shallow-water catastrophic spill 

event and 3-4 months from a deepwater catastrophic spill. It is estimated that there would be contact to 

the shoreline within 30 days of the spill for both shallow-water and deepwater spill locations. Though 

response methods would be monitored, there would also be some impact from these efforts on contacted 

coastal habitats. Further detail on this catastrophic OSRA run is contained in Appendix C of the CPA 

235/241/247 Supplemental EIS.

The life history of estuarine-dependent species involves spawning on the continental shelf; the 

transportation of eggs, larvae, or juveniles back to the estuary nursery grounds; and migration of the 

adults back to the sea for spawning (Deegan, 1989; Beck et al., 2001). Estuaries in the Gulf of Mexico 

are extremely important nursery areas and are considered EFH for fish and other aquatic life (Beck et al., 

2001). Oiling of these areas, depending on the severity, can destroy nutrient-rich marshes and erode 

coastlines that have been significantly damaged by recent hurricanes.

The Gulf of Mexico supports a wide variety of finfish, and most of the commercial finfish resources 

are linked either directly or indirectly to the estuaries that ring the Gulf of Mexico. Darnell et al. (1983) 

observed that the density distribution of fish resources in the Gulf was highest nearshore off of the central 

Gulf Coast. For all seasons, the greatest abundance occurred between Galveston Bay and the mouth of 

the Mississippi River. Oyster beds could be damaged by freshwater diversions that release tens of 

thousands of cubic feet of freshwater per second for months in an effort to keep oil out of the marshes. 

Adult oysters survive well physiologically in salinities from those of estuarine waters (about 7.5 parts per 

thousand sustained) to full strength seawater (Davis, 1958). While oysters may tolerate small changes in 

salinity for a few weeks, a rapid decrease in salinity over months would kill oysters. In the event of a 

catastrophic oil spill, at least 1 year’s oyster production in the area receiving fresh water would be lost 

because of exposure to freshwater and/or oil.

Phase 4—Post-Spill, Long-Term Recovery and Response 

In addition to possible small fish kills because of direct impacts (as described under Phases 2 and 3), a 

catastrophic spill could affect fish populations in the long term. Due to a catastrophic spill, a significant 

portion of a year class of fish could be absent from the following year’s fishery, reducing overall 

population numbers. However, sublethal impacts, especially for long-lived species (e.g., snapper and 

grouper), could be masked by reduced fishing pressure because of closures. In addition, healthy fish 

resources and fishery stocks depend on ideal habitat (EFH) for spawning, breeding, feeding, and growth 

to maturity. There could be long-term effects to coastal habitats from buried or sequestered oil becoming 

resuspended after a disturbance. Thus, a catastrophic spill that affects these areas could result in longterm impacts, including destruction to a portion of their natural habitats. 
Catastrophic Spill Event Analysis B-79

Overall Summary and Conclusion (Phases 1-4) 

Depending on the type of blowout and the proximity of marine life to it, an eruption of gases and 

fluids may generate not only a toxic effect but also pressure waves and noise significant enough to injure 

or kill local biota and destroy habitat in the immediate vicinity (Phase 1). Adult fish may be less at risk 

than earlier life stages, in part because they are less likely to concentrate at the surface and may avoid 

contact with floating oil. Effects of oil on organisms can include direct lethal toxicity, sublethal 

disruption of physiological processes (internal lesions), the effects from direct coating by oil (suffocation 

by coating gills), incorporation of hydrocarbons in organisms (tainting or accumulation in the food chain), 

and changes in biological habitat (decreased dissolved oxygen) (Phase 2). Estuaries in the Gulf of 

Mexico are extremely important nursery areas and are considered EFH for fish and other aquatic life 

(Beck et al., 2001). Oiling of these areas, depending on the severity, can destroy nutrient-rich marshes 

and erode coastlines that have been significantly damaged by recent hurricanes (Phase 3). Due to a 

catastrophic spill, a significant portion of a year class of fish could be absent from the following year’s 

fishery, reducing overall population numbers. However, sublethal impacts, especially for long-lived 

species (e.g., snapper and grouper), could be masked by reduced fishing pressure because of closures 

(Phase 4). 

B.3.1.18. Commercial Fisheries

Phase 1—Initial Event

The initial explosion and fire could endanger commercial fishermen in the immediate vicinity of the 

blowout. Although commercial fishing vessels in the area would likely aid in initial search-and-rescue 

operations, the subsequent fire could burn for over a month, during which time commercial vessels would 

be expected to avoid the area so as to not interfere with response activities. This could impact the 

livelihood and income of these commercial fishermen. The extent of the economic impact on the fishing 

community would depend largely on the season during which the blowout occurred, the depth of water in 

which it occurred, and its distance from shore.

Phase 2—Offshore Spill

The Gulf of Mexico is one of the largest producers of seafood in the continental United States. In 

2012, the Gulf of Mexico provided 38 percent of the commercial fishery landings in the continental U.S. 

(excluding Alaska), with over 1.7 billion pounds valued at $763 million (USDOC, NMFS, 2014b4). 

Various commercial species are fished from State waters through the Exclusive Economic Zone and are 

found throughout the water column as well as at the surface and near the seafloor. Commercial species 

occupy many different habitats throughout the area, and many commercial species occupy different 

habitats during different life stages. Most commercial species spend at least part of their life cycles in the 

productive shelf and estuarine habitat. In the event of a catastrophic offshore spill, it is assumed that a 

large quantity of oil would be released daily whether this spill occurred in State or Federal waters. 

Although the oil would generally float, it is also assumed that dispersants would be used preventing much 

of the oil from reaching the surface. 

As an example of the areas that could be affected by such a catastrophic oil spill in the CPA, OSRA 

model runs were performed using three different launch points as described in Chapter B.1.2.3. The 

resulting tables show conditional probabilities (expressed as percent chance) of an oil spill contacting 

resources in the GOM for each launch point and for each season, the condition being that a spill is 

assumed to have occurred at the given location. Because the commercial species are so widespread over 

the GOM, all of the tables are referenced (Appendix C of the CPA 235/241/247 Supplemental EIS, Tables 

C-4 and C-5). 

Oil that is not volatilized, dispersed, or emulsified by dispersants has the potential to affect finfish 

through direct ingestion of hydrocarbons or ingestion of contaminated prey. Finfish are, however, mobile 

and generally avoid adverse conditions. Less mobile species or planktonic larval stages are more 

susceptible to the effects of oil and dispersants.

Actual effects of any oil that is released and comes in contact with populations of commercially 

important species will depend on the API gravity of the oil, its ability to be metabolized by 

microorganisms, and the time of year of the spill. The effects on the populations will be at a maximum 
B-80 Central Planning Area Lease Sale 247 Supplemental EIS

during the spawning season of any commercially important population, exposing larvae and juveniles to

oil. The effects on commercial species may also include tainting of flesh or the perception of tainting in 

the market. This can, depending on the extent and duration of the spill, affect marketability of 

commercial species.

Even though sensory testing may show no detectable oil or dispersant odors or flavors and the 

chemical test results could be well below the known levels of concern, NOAA Fisheries would be 

expected to close large portions of the Gulf of Mexico during a high-volume spill. This would be done as 

a precautionary measure to ensure public safety and to assure consumer confidence in Gulf seafood 

(USDOC, NMFS, 2010b). Up to 40 percent of the Gulf of Mexico’s Exclusive Economic Zone could be 

closed to commercial fishing as the spill continues and expands (USDOC, NMFS, 2010c). This area 

could represent 50-75 percent of the Gulf’s seafood production (Flynn, 2010). The size of the closure 

area may peak about 50 days into the spill and could persist another 2-3 months until the well is killed or

capped and the remaining oil is recovered or dissipates. During this period, portions or all of individual 

State waters would also be closed to commercial fishing.

The economic impacts of closures on commercial fishing are difficult to predict because they are 

dependent on the season and would vary by fishery. If fishers cannot make up losses throughout the 

remainder of the season, a substantial part of their annual income would be lost. In some cases, 

commercial fishers will leave the industry and some may move to areas still open to fishing, but at a 

greater cost because of longer transit times. Marketing issues are also possible; even if the catch is 

uncontaminated, the public may lack confidence in the product. The duration of the public’s perception 

of seafood tainting is also difficult to predict and depends to some extent on the duration of the spill and 

public awareness of the spill.

Phase 3—Onshore Contact

Shoreline contact of oil is estimated to persist from 1 to 5 months in the event of a shallow-water 

catastrophic spill and for up to 6 months from a deepwater catastrophic spill. The OSRA probability 

tables show the conditional probabilities (expressed as percent chance) for a shoreline contact for each 

season, the condition being that a spill is assumed to have occurred at the given location. Further detail 

on this catastrophic OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS. 

This scenario, depending on the sea son of occurrence, would cause disruption in commercial fishing 

activity because many commercial fishermen operate inshore in State waters.

In addition to closures in Federal waters, portions of individual State waters would also be closed to 

commercial fishing. The economic impacts of closures on commercial fishing are complicated to predict 

because it is dependent on season and would vary by fishery. If fishers cannot make up losses in the 

remainder of the season, a substantial part of their annual income will be lost. In some cases, commercial 

fishers may move to areas still open to fishing, but at a greater cost because of longer transit times and, in 

some instances, additional license costs. Some commercial fishermen may also augment their income by 

aiding in the cleanup effort and/or renting the boats as vessels of opportunity.

Phase 4—Post-Spill, Long-Term Recovery and Response 

The Gulf of Mexico is an important biological and economic area in terms of commercial seafood 

production and recreational fishing. Commercial fishermen in the Gulf of Mexico harvested over 

1.7 billion pounds of finfish and shellfish in 2012 (USDOC, NMFS, 2014b). The economic impacts of 

closures on commercial fishing are complicated to predict because the economic effects are dependent on 

season and would vary by fishery. If fishermen cannot make up losses by fishing the remainder of the 

season or by participating as contractors in the cleanup, a substantial part of their annual income could be 

lost and may force them out of the industry. While the commercial fishing industry of Texas did not 

sustain measurable direct or indirect economic effects following the 1979 Ixtoc I blowout and spill 

(Restrepo et al., 1982), there is a documented phenomenon that, long after an incident, the perception of 

tainted fish and shellfish from the impacted area persists (Keithly and Diop, 2001). Data regarding the 

duration of the negative perception of Gulf seafood following the Deepwater Horizon explosion, oil spill, 

and response are not yet available. It is reasonable to assume that a negative perception could impact the 

value of commercial fish resources for several seasons.
Catastrophic Spill Event Analysis B-81

Overall Summary and Conclusion (Phases 1-4) 

The Gulf of Mexico is one of the largest producers of seafood in the continental United States. 

Various commercial species are fished from State waters through the Exclusive Economic Zone and are 

found throughout the water column. The primary economic impacts of oil spill on commercial fisheries 

are the closure of State or Federal waters to fishing and the perception of seafood tainting by the market. 

Both of these factors are difficult to predict. Closures depend on the size, timing, depth of water, and 

location of the spill as well as the fishery involved. Perception depends on length of the spill and public 

perception. Both of these factors could affect the livelihood of the fishing community. 

B.3.1.19. Recreational Fishing

Phase 1—Initial Phase

About 20 percent of the recreational fishing activity in the Gulf of Mexico occurs within 300 ft 

(91 m) of oil and gas structures (Hiett and Milon, 2002). Therefore, an explosion and fire could endanger 

recreational fishermen and divers in the immediate vicinity of the blowout, especially if the blowout is 

located close to shore. Recreational vessels in the area would likely aid in initial search-and-rescue 

operations but they would also be in danger during the explosion and subsequent fire. The subsequent 

fire could burn for up to a month, during which recreational vessels would be expected to avoid the area 

and to not interfere with response activities. It is also possible that recreational fishing could be impacted 

in areas beyond the immediate area of the event due to the perceptions of the public. 

Phase 2—Offshore Spill

If a catastrophic spill were to occur, a substantial portion of ocean waters could be closed. For 

example, 88,522 square miles (mi2

) (229,271 square kilometers [km2]) were closed to recreational fishing 

activity at the peak of the Macondo well oil spill. However, the majority of recreational fishing activity 

occurs fairly close to shore. Therefore, while the spill remains offshore, the impacts would be particularly 

felt with respect to fishing of offshore species such as king mackerel and red snapper (the impacts of a 

catastrophic spill on fish populations are discussed in Chapter B.3.1.17). The NOAA’s Center for 

Coastal Monitoring and Assessment (USDOC, NOAA, Center for Coastal Monitoring and Assessment,

2012b) provides a set of maps that display the locations in the Gulf of Mexico where certain fish species 

are prevalent. However, even while the spill remains offshore, there could be impacts to inshore 

recreational fishing due to misperceptions regarding the extent of the spill or due to concerns regarding 

the tainting of fish species. These misperceptions could also reduce tourism activity, which would impact 

tourism-based recreational fishing activity.

In 2011, the percent of each Gulf Coast State’s recreational fishing activity that occurred in State and 

Federal ocean waters combined (i.e., not inland waters) were as follows: Texas (6%); Louisiana (5%); 

Mississippi (2%); Alabama (42%); and West Florida (34%) (USDOC, NMFS, 2012; Texas Parks and 

Wildlife Department, 2012). Chapter 4.1.1.17 of this Supplemental EIS provides a further breakdown of 

recreational fishing activity by state. Further detail on this catastrophic OSRA run is contained in 

Appendix C of the CPA 235/241/247 Supplemental EIS. 

Phase 3—Onshore Contact

If a catastrophic spill were to reach shore, there would likely be noticeable impacts to recreational 

fishing activity. Since most recreational fishing activity occurs fairly close to shore, there would be a 

number of direct impacts to angler activity due to the fishing closures that would likely arise. This is 

particularly true since anglers would find it more difficult to find substitute fishing sites in the case of a 

catastrophic spill. In 2011, the percent of each Gulf State’s recreational fishing activity that occurred

inland were as follows: Texas (94%); Louisiana (95%); Mississippi (98%); Alabama (58%); and West 

Florida (66%) (USDOC, NMFS, 2012; Texas Parks and Wildlife Department, 2012). The impacts to 

recreational fishing would also depend on the time of year of the spill. In 2011, 31 percent of angler trips 

in the Gulf occurred between January and April, 41 percent of angler trips occurred between May and 

August, and 28 percent of angler trips occurred between September and December (USDOC, NMFS, 

2012). In addition, fishing tournaments are often scheduled for the summer months and would be 
B-82 Central Planning Area Lease Sale 247 Supplemental EIS

difficult to reschedule in the aftermath of a catastrophic spill. Further detail on this catastrophic OSRA 

run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS.

There would also be various economic impacts along the recreational fishing supply chain. Gentner 

Consulting Group (2010) estimates that recreational fishing activity supports $9.8 million in direct 

expenditures and $23 million in total sales per day in the Gulf of Mexico. There could be further impacts 

if the fishing closures persisted long enough to affect purchases of boats and other durable fishing 

equipment. There could also be further impacts if the loss of opportunities for recreational fishing 

activity exacerbated the fall in tourism activity that would arise due to the spill.

Phase 4—Post-Spill, Long-Term Recovery and Response 

The long-term impacts of a catastrophic spill on recreational fishing activity would primarily depend 

on the extent to which fish populations recover (refer to Chapter B.3.1.17 for more information). 

However, the longer term impacts of a spill on recreational fishing activity would also depend on the 

extent to which public perceptions of fish tainting can be assuaged. In addition, the longer-term impacts 

would depend on the extent to which the various firms that serve the recreational fishing industry would 

be able to weather the downturn in activity resulting from the spill. 

Overall Summary and Conclusion (Phases 1-4) 

Recreational fishing activity could be noticeably impacted in the event of a catastrophic spill. This is 

particularly the case if the spill reached shore or if the spill occurred during peak times and places of 

recreational fishing activity. The long-term impacts of a catastrophic spill would depend on the extent to 

which fish populations recover and the length of time it would take to convince the public that it was 

again safe to fish in the affected areas.

B.3.1.20. Recreational Resources

Phase 1—Initial Event

The most immediate impacts of a catastrophic spill would be on the recreational fishing and 

recreational diving activity in the vicinity of the blowout. About 20 percent of the recreational fishing 

activity and 90 percent of the recreational diving activity in the Gulf of Mexico from Alabama to Texas 

occurs within 300 ft (91 m) of oil and gas structures (Hiett and Milon, 2002). The impacts on recreational 

fishing and recreational diving would be greater the closer the blowout occurred to shore. The immediate 

response activities could also impact ocean-based recreational activity. Finally, there could be impacts to 

tourism activity since a catastrophic spill would likely receive a large amount of media attention.

Phase 2—Offshore Spill

While the spill is still offshore, there could be some ocean-dependent recreation that is affected (e.g., 

fishing, diving, and boating), as discussed above. In addition, there may be some effects due either to 

perceived damage to onshore recreational resources that has not yet materialized or to general hesitation 

on the part of travelers to visit the overall region because of the spill. A Congressional hearing into this 

matter (U.S. House of Representatives, 2010) provides a broad overview of some of the effects that were 

felt along the Gulf Coast subsequent to the Deepwater Horizon explosion, oil spill, and response. For 

example, a representative of Pinellas County estimated that this area had lost roughly $70 million in hotel 

revenue even though beaches in this area did not receive any oil damage. This type of effect could be due 

to misperceptions about the spill, uncertainty about the future of the spill, or concerns about whether a 

tourism experience will be affected even if the destination is only within close proximity to a spill.

As previously mentioned, recreational diving is one offshore recreational activity that would be 

particularly affected by a catastrophic oil spill. Further detail on this catastrophic OSRA run is contained 

in Appendix C of the CPA 235/241/247 Supplemental EIS.
Catastrophic Spill Event Analysis B-83

Phase 3—Onshore Contact

A catastrophic spill has the potential to noticeably impact the Gulf Coast recreation and tourism 

industries. The water-dependent and beach-dependent components of these industries would be 

particularly vulnerable. Environmental Sensitivity Indexes (ESIs) provide overall measures of the 

sensitivity of a particular coastline to a potential oil spill. The ESIs rank coastlines from 1 (least 

sensitive) to 10 (most sensitive). Marshes and swamps are examples of resources that have ESIs of 10 

due to the extreme difficulty of removing oil from these areas; marsh and swamp areas are particularly 

prevalent in Louisiana. The ESIs for beach areas generally range from 3 to 6, depending on the type of 

sand and the extent to which gravel is mixed into the beach area; beach areas are particularly prevalent in 

Texas, Mississippi, Alabama, and Florida. The ESI maps for any coastline along the Gulf of Mexico can 

be viewed using the National Oceanic and Atmospheric Administration’s ERMA mapping system 

(USDOC, NOAA, 2012b and USDOC, NOAA, Office of Response and Restoration, 2014). The ESI 

maps also provide point indicators for recreational resources.

A catastrophic spill would also raise a number of issues regarding recreational activity that is based 

on tourism. One important point is that a spill of the Deepwater Horizon’s dimensions can influence a 

much broader range of individuals and firms than can a smaller spill. For example, a small, localized spill 

may lead some travelers to seek substitute recreational opportunities in nearby areas. However, a large 

spill is more likely to dissuade travelers from visiting a broader economic region. Similarly, small- and 

mid-sized restaurant chains and hotels may be able to find other customers or to simply weather a smaller 

spill. However, a spill the size of the Deepwater Horizon is more likely to affect these types of firms 

since they are less able to diversify their customer base. These effects can be seen in the makeup of those 

who filed damage claims with BP (Gulf Coast Claims Facility, 2012); the Gulf Coast Claims Facility 

closed in early 2012 subsequent to preliminary court approval of a settlement program. For example, the 

bulk of the claims by individuals have been made in the food, beverage, and lodging sector and in the 

retail, sales, and service sector. Claims have also been made by individuals and firms in a broad range of 

geographic regions, many of which were not directly impacted by oil. 

Murtaugh (2010) provides data on the change in hotel and sales tax receipts for individual Gulf Coast 

counties in the months immediately following the Deepwater Horizon explosion, oil spill, and response. 

During the summer of 2010, the spill caused substantial declines in hotel receipts in the following 

counties: Baldwin, Alabama (33.2% decline); Santa Rosa, Florida (24.8% decline); Okaloosa, Florida 

(24.1% decline); Walton, Florida (12.3% decline); and Bay, Florida (7.4% decline). However, coastal 

counties west of Baldwin, Alabama (as far west as St. Mary, Louisiana), generally experienced noticeable 

increases in hotel receipts. This was particularly true in Mobile, Alabama; Jackson, Mississippi; and in 

the coastal parishes of Louisiana. For example, in Louisiana, St. Mary, Terrebonne, and Lafourche 

Parishes each reported increases in hotel tax receipts of over 80 percent in the summer of 2010. These 

effects are likely due to the influx of oil-spill relief workers to these areas in the immediate aftermath of 

the Deepwater Horizon explosion, oil spill, and response. Overall sales tax receipts in counties from 

Baldwin, Alabama, eastward also generally fell during 2010, although to a lesser extent than hotel tax 

receipts. Sales tax receipts in counties and parishes west of Baldwin, Alabama, did not show as clear a 

pattern as did hotel tax receipts. For example, overall sales tax receipts fell by 12.5 percent in Hancock 

County (Mississippi), receipts were almost unchanged in Harrison County (Mississippi), and receipts 

increased by 8.3 percent in Orleans Parish (Louisiana). These results suggest that the impacts of a future 

catastrophic spill will be influenced by the structure of a particular county/parish’s recreational economy, 

as well as by the extent to which oil-spill-response activities will mitigate some of the negative impacts of 

the spill in certain areas.

There could also be effects on tourist activities in areas far away from the areas directly affected by 

oil. For example, in Texas subsequent to the Deepwater Horizon explosion, oil spill, and response, some 

tourists may have stayed away from Texas Gulf Coast beaches due to misperceptions regarding the extent 

to which these beaches were damaged due to the spill. Conversely, there may have been some 

substitution of beach visitation away from beaches in the eastern Gulf towards the beaches in Texas, 

which were farther from the spill. While it is difficult to quantify these effects, some anecdotal evidence 

regarding this substitution effect can be found in Pack (2010). Hotel occupancy data suggest that these 

two effects may have largely offset each other. Source Strategies Inc. (2010) reports that total hotel 

occupancy in the three metro regions in Texas closest to the Gulf Coast increased just 1.9 percent during 
B-84 Central Planning Area Lease Sale 247 Supplemental EIS

the third quarter of 2010 compared with the third quarter of 2009. Further detail on this catastrophic 

OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental EIS. 

Phase 4—Post-Spill, Long-Term Recovery and Response 

The longer-term implications of a catastrophic event on tourism would depend on the extent to which 

any structural/ecological damage can be repaired and the extent to which economic mitigation actions 

would occur. The long-term implications of a catastrophic spill would also depend on the extent to which 

public confidence in the various components of the recreational and tourism economies can be restored. 

For example, restaurants in the region would be impacted to the extent to which they are perceived to use 

seafood products caught or raised in contaminated waters. Similarly, although beaches can be 

decontaminated not long after a spill has been stopped, lingering perceptions can be expected to 

negatively impact tourism even after a spill has ended.

Oxford Economics (2010) attempts to quantify these effects by analyzing the impacts of recent 

catastrophic events on recreational economies. For example, they analyzed the Ixtoc I well blowout and 

spill of 1979, the scale and nature of which was reasonably similar to the Macondo well blowout and spill 

of 2010. In this example, it took approximately 3 years for beaches to be cleaned and for recreational 

activity to return to similar levels as before the spill. They also looked at the Prestige oil spill of 2002 off 

the coast of Spain. Given the nature and size of that spill, recreational activity was able to return to prespill levels in approximately 1 year. Alaska’s tourism economy took approximately 2 years to recover 

from the Exxon Valdez spill.

Overall Summary and Conclusion (Phases 1-4) 

A catastrophic spill can cause noticeable impacts to recreational resources such as beaches. A 

catastrophic spill can also have complex effects on recreational activity that depends on tourism. The 

longer-term implications of a catastrophic oil spill on tourism would depend on the extent to which any 

structural/ecological damage can be repaired, the extent to which economic mitigation actions would 

occur, and the speed at which public confidence in the various components of the affected recreational 

and tourism economies would be restored. 

B.3.1.21. Archaeological Resources

Phase 1—Initial Event

Offshore Archaeological Resources

BOEM protects all known, discovered, and potentially historic and prehistoric archaeological 

resources on the OCS by requiring appropriate avoidance criteria as well as directives to investigate these 

resources. Onshore archaeological resources, prehistoric and historic sites, would not be immediately 

impacted during the initial phase of a catastrophic blowout because the distance of a blowout site from 

shore is at least 3 nmi (3.5 mi; 5.6 km). However, offshore catastrophic blowouts, when compared with 

spills of lesser magnitude, may initially impact multiple archaeological resources. Resources adjacent to 

a catastrophic blowout could be damaged by the high volume of escaping gas, buried by large amounts of 

dispersed sediments, crushed by the sinking of the rig or platform, destroyed during emergency relief well 

drilling, or contaminated by the hydrocarbons. 

Based on historical information, over 2,100 potential shipwreck locations have been identified on the 

Gulf of Mexico OCS (USDOI, MMS, 2007). This number is a conservative estimate and is heavily 

weighted toward post-19th century, nearshore shipwrecks, where historic records documenting the loss of 

the vessels were generated more consistently. BOEM currently has confirmed locational data for 

approximately 380 potential wreck sites, though the historic significance for the majority of these sites 

has not been determined. 

BOEM’s Regional Director may require the preparation of an archaeological report to accompany the 

exploration plan, development operations coordination document, or development and production plan, 

under 30 CFR § 550.194, and BSEE’s Regional Director may do likewise under 30 CFR § 250.194 if a 

potential wreck is encountered during operations. As part of the environmental reviews conducted for 

postlease activities, available information is evaluated regarding the potential presence of archaeological 
Catastrophic Spill Event Analysis B-85

resources within the CPA proposed action area to determine if additional archaeological resource surveys 

and mitigations are warranted. Having complete knowledge of seafloor resources before a spill occurs 

would enable responders to quickly plan countermeasures in a way that would minimize adverse effects 

occurring from the spill response. 

Phase 2—Offshore Spill

Offshore Archaeological Resources

Due to the response methods (i.e., subsea dispersants) and magnitude of the response (i.e., thousands 

of vessels), a catastrophic blowout and spill have a greater potential to impact offshore archaeological 

resources than other accidental events.

Deep Water

In contrast to smaller spills or spills in shallow water, large quantities of subsea dispersants could be 

used for a catastrophic subsea blowout in deep water. This could result in currently unknown effects from 

dispersed oil droplets settling to the seafloor. Though information on the actual impacts to submerged 

cultural resources is inconclusive at this time, oil settling to the seafloor could come in contact with 

archaeological resources. At present, there is no evidence of this having occurred. A recent experimental 

study has suggested that, while the degradation of wood in terrestrial environments is initially retarded by 

contamination with crude oil, at later stages, the biodeterioration of wood is accelerated (Ejechi, 2003). 

While there are different environmental constraints that affect the degradation of wood in terrestrial and 

waterlogged environments, soft-rot fungal activity, one of the primary wood degrading organisms in 

submerged environments, was shown to be increased in the presence of crude oil (Ejechi, 2003). There is 

a possibility that oil from a catastrophic blowout could come in contact with wooden shipwrecks and 

artifacts on the seafloor and accelerate their deterioration.

Ancillary damages from vessels associated with oil-spill-response activities (e.g., anchoring) in deep 

water are unlikely because of the use of dynamically positioned vessels responding to a deepwater 

blowout. If response and support vessels were to anchor near a deepwater blowout site, the potential to 

damage undiscovered vessels in the area would be high because of the required number and the size of 

anchors and the length of mooring chains needed to safely secure vessels. Additionally, multiple offshore 

vessel decontamination stations would likely be established in shallow water outside of ports or entrances 

to inland waterways, as seen for the Deepwater Horizon explosion, oil spill, and response. The anchoring 

of vessels could result in damage to both known and undiscovered archaeological sites; the potential to 

impact archaeological resources increases as the density of anchoring activities in these areas increases.

Shallow Water

The potential for damaging archaeological resources increases as the oil spill and related response 

activities progress landward. In shallower waters, most of the damage would be associated with oil 

cleanup and response activities. Thousands of vessels would respond to a shallow-water blowout and 

would likely anchor, potentially damaging both known and undiscovered archaeological sites. Additional 

anchoring would be associated with offshore vessel decontamination stations, as described above. As the 

spill moves into the intertidal zone, the chance of direct contact between the oil and archaeological 

resources increases. As discussed above, this could result in increased degradation of wooden shipwrecks 

and artifacts.

Additionally, in shallower waters, shipwrecks often act as a substrate to corals and other organisms, 

becoming an essential component of the marine ecosystem. These organisms often form a protective 

layer over the shipwreck, virtually encasing the artifacts and hull remains. If these fragile ecosystems 

were destroyed as a result of the oil spill and the protective layer was removed, the shipwreck would then 

be exposed to increased degradation until it reaches a new level of relative stasis with its surroundings.

Regardless of water depth, because oil is a hydrocarbon, heavy oiling could contaminate organic 

materials associated with archaeological sites, resulting in erroneous dates from standard radiometric 

dating techniques (e.g., 14C-dating). Interference with the accuracy of 14C-dating would result in the loss 

of valuable data necessary to understand and interpret the sites.
B-86 Central Planning Area Lease Sale 247 Supplemental EIS

Phase 3—Onshore Contact

Onshore Archaeological Resources

Regardless of the water depth in which the catastrophic blowout occurs, it is assumed that more than 

1,000 mi (1,609 km) of shoreline could be oiled to some degree. Onshore prehistoric and historic sites 

would be impacted to some extent by a high-volume spill from a catastrophic blowout that reaches shore. 

Sites on barrier islands could suffer the heaviest impact, and a few prehistoric sites located inland from 

the coastline, in the marsh, and along bayous could also experience some light oiling. Impacts would 

include the loss of ability to accurately date organic material from archaeological sites because of 

contamination or increased research costs to clean samples for analysis. Efforts to prevent coastal cultural 

resources from becoming contaminated by oil would likely be overwhelmed in the event of a hurricane 

and by the magnitude of shoreline impacted. 

The most significant damage to archaeological sites could be related to cleanup and response efforts. 

Fortunately, important lessons were learned from the Exxon Valdez spill in Alaska in 1989, in which the 

greatest damage to archaeological sites was related to cleanup activities and looting by cleanup crews 

rather than from the oil itself (Bittner, 1996). As a result, cultural resources were recognized as 

significant early in the Deepwater Horizon response and cleanup, and archaeologists were embedded in 

Shoreline Cleanup Assessment Teams (SCAT) and consulting with cleanup crews. Historic preservation 

representatives were present at both the Joint Incident Command as well as each Area Command under 

the general oversight of the National Park Service to coordinate response efforts (Odess, official 

communication, 2010). Despite these efforts, some archaeological sites suffered damage from looting or 

from spill cleanup activities, most notably the parade ground at Fort Morgan, Alabama (Odess, official 

communication, 2011). 

Phase 4—Post-Spill, Long-Term Recovery and Response 

Onshore Archaeological Resources

Regardless of the water depth in which the catastrophic blowout occurs, it is assumed that more than 

1,000 mi (1,609 km) of shoreline could be oiled to some degree. Onshore prehistoric and historic sites 

would be impacted to some extent by a high-volume spill from a catastrophic blowout that reaches shore. 

A few prehistoric sites in Louisiana, located inland from the coastline in the marsh and along bayous, 

could experience some light oiling. As discussed above, impacts would include the permanent loss of 

ability to accurately date organic material from archaeological sites because of contamination. The most 

significant damage to archaeological sites would be related to cleanup and response efforts. Long-term 

recovery would prove difficult if not impossible. Historic structures such as coastal forts that are exposed 

to oiling are generally constructed of brick or other porous, friable materials that are difficult to clean 

without causing further damage (Chin and Church, 2010). Funding for any sort or archaeological 

recovery is problematic outside of Federal lands because of existing laws and regulations (Varmer, 2014). 

Most coastal prehistoric sites in Louisiana, for example, are on private lands where there is no mechanism 

to recover damages. Section 106 of the National Historic Preservation Act is triggered by a Federal 

undertaking, which in the case of a spill, would be the response and not the actual spill. The Natural 

Resource Damage Assessment (NRDA) process codified by the Oil Pollution Act of 1990 is a legal 

process to determine the type and amount of restoration needed to compensate the public for harm to 

natural resources that occurs as a result of an oil spill, but it does not cover cultural, archaeological, or 

historic properties. 

Overall Summary and Conclusion (Phases 1-4) 

Archaeological resources are finite, unique, irreplaceable, nonrenewable records of mankind’s past, 

which, once destroyed or damaged, are gone forever. In the event of a catastrophic oil spill, the most 

likely source of irreversible impact is, ironically, from the spill response, and the danger increases 

dramatically as the response approaches the shoreline. This damage can, to a large extent, be mitigated 

by the early integration of archaeologists and State and Tribal historic preservation officers in the 

response to protect sites from impact. Mitigation of impacts from the oil itself is likely to meet with 

varied success depending upon the type of site and availability of funding. 
Catastrophic Spill Event Analysis B-87

B.3.1.22. Land Use and Coastal Infrastructure

Phase 1—Initial Event

There would likely be no adverse impacts to land use and coastal infrastructure as a result of the 

events and the potential impact-producing factors that could occur throughout Phase 1 of a catastrophic 

spill event because of the long distance (>3 nmi; 3.5 mi; 5.6 km) from shore and the short duration of the 

initial event, fire, and/or explosion. 

Phase 2—Offshore Spill

Impacts to tourism and recreational resources are addressed in Chapter B.3.1.20. Possible fisheries 

closures are addressed in Chapters B.3.1.18 and B.3.1.19. As cleanup and remediation efforts evolve, 

there would be increased activity at ports and coastal cities, leading to increased traffic on road 

infrastructure and at port facilities. This follows from consideration of BOEM’s scenario estimates of up 

to 3,000 vessels, 25-50 planes/helicopters, and up to 25,000 workers for a shallow-water event and up to 

7,000 vessels, 50-100 planes/helicopters, and up to 50,000 workers for a deepwater event. Waste disposal 

activities associated with boom deployment and retrieval would increase demand at waste disposal 

facilities. BOEM’s scenario estimates 5 million feet (1.5 million meters) of boom deployment and 

35,000 bbl of dispersant applied at the surface for a shallow-water event or 11 million feet (3.4 million 

meters) of boom deployment and 33,000 bbl of dispersant applied at the surface and 16,500 bbl of 

dispersant applied subsea for a deepwater event. Also, vessel decontamination sites would be set up 

offshore and the staffing/maintenance of these sites would contribute to increased activity at port facilities 

and traffic congestion on coastal waterways and highways.

Phase 3—Onshore Contact

In the event of a catastrophic spill, impacts on land use and infrastructure would be temporary and 

variable in nature. The scale of impact would depend on the nature of the event and whether it occurs in 

shallow or deep water. These impacts would include land use in staging areas, waste disposal locations 

and capacities, and potential delays because of vessel decontamination stations near ports, as described 

below. 

For a shallow-water event, BOEM estimates 5-10 staging areas and 200-300 skimmers. For a 

deepwater event, scenario estimates call for 10-20 staging areas and 500-600 skimmers. Given these 

estimates and the several thousand responders that would be involved in the effort, BOEM expects a 

further increase in traffic congestion and some possible competing land-use issues near the staging areas, 

depending on the real estate market at the time of the event. Some infrastructure categories, such as 

vessels, ports, docks and wharves, would likely become very engaged in response activities and this could 

result in a shortage of space and functionality at infrastructure facilities if ongoing drilling activities were 

simultaneously occurring. However, if drilling were to be suspended, conflicting demands on 

infrastructure facilities would likely fail to materialize.

In the category of waste disposal, the impacts would be more visible as thousands of tons of oily 

liquid and solid wastes from the oil-spill cleanup would be disposed of in onshore landfills. As was the 

case in the Deepwater Horizon explosion, oil spill, and response, USEPA, in consultation with USCG, 

would likely issue solid-waste management directives to address the issue of contaminated materials and 

solid or liquid wastes that are recovered as a result of cleanup operations (USEPA, 2010c and 2010d). 

For navigation and port use, there would also be the potential for delays in cargo handling and slow 

vessel traffic because of decontamination operations at various sites along the marine transportation

system (USDOT, 2010). However, vessel decontamination activities most likely would be complete 

within a year of the event, so impacts would be expected to be limited in duration. 

Phase 4—Post-Spill, Long-Term Recovery and Response 

Based on the rapid recovery of infrastructure that was heavily damaged by the catastrophic 2005 

hurricane season and the region’s experience in the few years since the Deepwater Horizon explosion, oil 

spill, and response, BOEM would not expect any long-term impacts to land use and coastal infrastructure 

as a result of a catastrophic oil-spill event. However, if a catastrophic oil spill were to occur, BOEM 
B-88 Central Planning Area Lease Sale 247 Supplemental EIS

would (as it is currently with regard to the Deepwater Horizon explosion, oil spill, and response) monitor 

the post-spill, long-term recovery phase of the event for any changes that indicate otherwise. A 

catastrophic spill could generate several thousand tons of oil-impacted solid materials disposed in 

landfills along the Gulf Coast. This waste may contain debris, beach, or marsh material (sand/silt/clay), 

vegetation, and personal protection equipment collected during cleanup activities. BOEM does not 

expect that landfill capacity would be an issue at any phase of the oil-spill event or the long-term 

recovery. In the case of the Deepwater Horizon explosion, oil spill, and response, USEPA reported that 

existing landfills receiving oil-spill waste had plenty of capacity to handle waste volumes; the Deepwater 

Horizon explosion, oil spill, and response’s waste that was disposed of in landfills represented less than 

7 percent of the total daily waste normally accepted at these landfills (USEPA, 2012).

It is not expected that any long-term, land-use impacts would arise from properties that are utilized 

for restoration activities and would somehow have their future economic use compromised. The rise or 

fall of property values would not be solely a function of some kind of economic impact from a 

catastrophic oil-spill event. There are many other factors that influence the value of property and its best 

economic use. To date, it is not clear from past experiences whether vegetation loss or erosion created by 

a spill could result in changes in land use. The amount and location of erosion and vegetation loss could 

be influenced by the time of year the spill occurs, its location, and weather patterns, including hurricane 

landfalls.

Overall Summary and Conclusion (Phases 1-4) 

There would likely be no adverse impacts to land use and coastal infrastructure throughout Phase 1 of 

a catastrophic spill event. Response efforts in Phases 2 and 3 would require considerable mobilization of 

equipment and people. While these efforts might temporarily displace traditional users of coastal land 

and infrastructure, these interruptions would not be long lasting. The post-spill, long-term recovery and 

response efforts during Phase 4 could generate several thousand tons of oil-impacted solid materials 

disposed in landfills along the Gulf Coast, but this would account for no more than 7 percent of the total

daily waste normally accepted in these landfills. It is also not expected that any properties utilized for 

restoration activities throughout Phase 3 would not suffer any long-term land use or economic impacts.

B.3.1.23. Demographics

Phase 1—Initial Event

The impacts of a catastrophic spill on demographics would primarily be driven by the spill’s impacts 

on employment (refer to Chapter B.3.1.24). Since the impacts of a catastrophic spill on employment 

would take time to evolve, the initial impacts on demographics would be minimal. Therefore, there 

would likely be no adverse impacts to demographics as a result of the events and the potential impactproducing factors that could occur throughout Phase 1 of a catastrophic spill event. 

Phase 2—Offshore Spill

The impacts of a catastrophic spill on demographics would primarily be driven by the spill’s impacts 

on employment (refer to Chapter B.3.1.24). For example, there could be some suspension of oil/gas 

activities in the immediate aftermath of the spill. This could cause some workers to seek employment 

outside of the OCS industry, for example in onshore oil/gas extraction or on overseas offshore projects. 

However, since the OCS oil and gas industry would likely eventually recover, the long-term impacts on

demographics would be small. There could also be impacts on demographics if employment in 

recreation, tourism, or fishing industries were affected, due to either actual or perceived impacts of the 

spill. However, the impacts on these industries would become more acute if the spill were to reach shore.

Phase 3—Onshore Contact

The impacts of a catastrophic spill on demographics would primarily be driven by the spill’s impacts 

on employment (refer to Chapter B.3.1.24). For example, impacts to recreation/tourism and recreational 

and commercial fishing activities would become more acute if the spill were to reach shore. There would 

also be a larger presence of cleanup workers in some areas if the spill were to reach shore. For example, 
Catastrophic Spill Event Analysis B-89 

48,200 workers were employed in response activities at the peak of the response effort following the 

Macondo well blowout and spill (RestoreTheGulf.gov, 2011). However, these impacts would be 

temporary and would be governed by the dynamics of the particular spill. There could also be impacts to 

demographics if there were impacts on the response workers’ health or if the demographics of the 

response workers were noticeably different from the local population.

Phase 4—Post-Spill, Long-Term Recovery and Response 

The impacts of a catastrophic spill on demographics would primarily be driven by the spill’s impacts 

on employment (refer to Chapter B.3.1.24). The spill’s impacts on employment, and therefore 

demographics, would primarily be felt in the oil/gas, recreational fishing, commercial fishing, and 

recreation/tourism industries. However, it is unlikely that a catastrophic spill would cause substantial 

long-term changes to a region’s demographics. For example, the demographics data in Woods and Poole 

Economics, Inc. (2011) did not suggest large demographic changes to any Gulf regions subsequent to the 

Deepwater Horizon explosion, oil spill, and response. 

Overall Summary and Conclusion (Phases 1-4) 

The impacts of a catastrophic spill on demographics would primarily be driven by the spill’s impacts 

on employment (refer to Chapter B.3.1.24). These impacts would likely be temporary and would be 

governed by the particular dynamics of the spill. 

B.3.1.24. Economic Factors

Phase 1—Initial Event

The most immediate economic impacts of a catastrophic spill would be on the oil/gas production and 

employment associated with the area of the spill. There could also be impacts on commercial fishing 

(Chapter B.3.1.18), recreational fishing (Chapter B.3.1.19), and recreational resources (Chapter 

B.3.1.20). However, the primary economic impacts of a catastrophic spill would depend how the spill 

evolves, which is discussed in subsequent sections.

Phase 2—Offshore Spill

In contrast to a less severe accidental event, suspension of some oil and gas activities would be likely 

following a catastrophic event. Depending on the duration and magnitude, this could impact hundreds of 

oil-service companies that supply the steel tubing, engineering services, drilling crews, and marine supply 

boats critical to offshore exploration. An interagency economic report estimated that the suspension 

arising from the Deepwater Horizon explosion, oil spill, and response may have directly and indirectly 

resulted in up to 8,000-12,000 fewer jobs along the Gulf Coast (USDOC, Economics and Statistics 

Administration, 2010). Greater New Orleans, Inc. (2012) provides an overview of the impacts of 

decreased oil and gas industry operations subsequent to the Deepwater Horizon explosion, oil spill, and 

response. This report provides survey evidence regarding the various economic strains felt by businesses 

in Louisiana due to the Deepwater Horizon explosion, oil spill, and response. For example, this report 

found that 41 percent of the respondents were not making a profit due to the slowdown in operations. The 

economic impacts of a catastrophic spill would likely be more heavily concentrated in smaller businesses 

than in the larger companies due to their difficulty in finding substitute revenue sources. Much of the 

employment loss would be concentrated in coastal oil-service parishes in Louisiana (St. Mary, 

Terrebonne, Lafourche, Iberia, and Plaquemines Parishes) and counties/parishes where drilling-related 

employment is most concentrated (Harris County, Texas, in which Houston is located, and Lafayette 

Parish, Louisiana). There could also be economic impacts due to the impacts on commercial fishing 

(Chapter B.3.1.18), recreational fishing (Chapter B.3.1.19), and recreational resources (Chapter 

B.3.1.20).
B-90 Central Planning Area Lease Sale 247 Supplemental EIS

Phase 3—Onshore Contact

By the end of a catastrophic spill, a large number of personnel (up to 25,000 in the event of a shallowwater spill and up to 50,000 in the event of a deepwater spill) would be expected to have responded to 

protect the shoreline and wildlife and to cleanup vital coastlines. The degree to which new cleanup jobs 

offset job losses would vary greatly from county to county (or parish to parish). However, these new jobs 

would not make up for lost jobs, in terms of dollar revenue. In most cases, cleanup personnel are paid 

less (e.g., $15-$18 per hour compared with roughly $45 per hour on a drilling rig), resulting in consumers 

in the region having reduced incomes overall and thus, spending less money in the economy (Aversa, 

2010). In addition, the economic impacts of relief workers would likely vary by county or parish, causing 

noticeable positive economic impacts to some counties or parishes while having fairly small positive 

impacts in other counties or parishes (Murtaugh, 2010). However, the influx of relief workers could also 

cause some negative impacts if it disrupted some of the normal functioning of economies. In addition, if 

the spill reaches shore, the impacts to commercial fishing (Chapter B.3.1.18), recreational fishing 

(Chapter B.3.1.19), and recreational resources (Chapter B.3.1.20) would likely be greater.

In the unfortunate event of a future disaster, the creation of a large financial claims administration 

process, similar to the Gulf Coast Claims Facility, would be likely. This administrative body would be 

responsible for distributing funds made available by the responsible party to parties financially hurt by the 

disaster. As demonstrated by the actions of Gulf Coast Claims Facility recipients following the 

Deepwater Horizon explosion, oil spill, and response, funds will likely be used by individuals to pay for 

necessities such as mortgages or groceries, while businesses who receive funds will likely use them to 

maintain payroll and current payments on equipment. As of March 2012, over $6 billion had been paid 

through the Gulf Coast Claims Facility, which mitigated some of the economic impacts of the Deepwater 

Horizon explosion, oil spill, and response (Gulf Coast Claims Facility, 2012). 

Phase 4—Post-Spill, Long-Term Recovery and Response 

While a catastrophic spill could immediately impact several Gulf Coast States for several months 

through fishing closures, loss of tourism, and any suspension of oil and gas activities, anticipating the 

long-term economic and employment impacts in the Gulf of Mexico is a difficult task. Many of the 

potentially affected jobs, like fishing charters, are self-employed. Thus, they would not necessarily file 

for unemployment and will not be included in business establishment surveys used to estimate State 

unemployment levels. In addition, unemployment numbers in states are based on nonagricultural jobs, 

and the fishing industry is considered within the agriculture category. On the other side, it is also a 

challenge to estimate how many of these displaced workers have been hired to clean up the spill. For 

example, while thousands of vessels of opportunity would be active in the spill response, not all of these 

would be displaced commercial fishermen from the affected areas. The positive employment impacts 

related to response activities are likely to be shorter term than the negative impacts discussed above. 

However, the long-term economic impacts of a catastrophic spill will likely depend on the speed at which 

the oil/gas, commercial fishing, recreational fishing, and recreational industries recover. 

Overall Summary and Conclusion (Phases 1-4) 

There would be a number of economic impacts that would arise from a catastrophic oil spill. The 

most direct effects would be on the recreation/tourism, commercial fishing, and recreational fishing 

industries that depend on damaged resources. There could also be substantial negative effects on the 

oil/gas industry due to moratoriums or rule changes that would arise. Finally, there could be substantial 

impacts due to the relief operations and economic mitigation activities that would occur in the aftermath 

of a catastrophic spill.

B.3.1.25. Environmental Justice

Phase 1—Initial Event

There would likely be no adverse impacts to environmental justice as a result of the events and the 

potential impact-producing factors that could occur throughout Phase 1 of a catastrophic spill event 
Catastrophic Spill Event Analysis B-91

because of the long distance (>3 nmi; 3.5 mi; 5.6 km) from shore and the short duration of the initial 

event, fire, and/or explosion. 

Phase 2—Offshore Spill

The environmental justice policy, based on Executive Order 12898 of February 11, 1994, directs 

agencies to incorporate into NEPA documents an analysis of potentially disproportionate and detrimental 

environmental and health effects of their proposed actions on minorities and low-income populations and 

communities. While the spill is still offshore, the primary environmental justice concern would be large 

commercial fishing closures disproportionately impacting minority fishers. In the event of a catastrophic 

spill, Federal and State agencies would be expected to close substantial portions of the Gulf to 

commercial and recreational fishing (USDOC, NOAA, 2010e). While oystering occurs “onshore,” oyster 

beds are also likely to be closed to harvests during Phase 2 of a catastrophic spill because of concerns 

about oil contamination and increased freshwater diversions to mitigate oil intrusion into the marshes. 

These closures would directly impact commercial fishermen and oystermen, and indirectly impact such 

downstream activities as shrimp processing facilities and oyster shucking houses. The mostly AfricanAmerican communities of Phoenix, Davant, and Point à la Hache in Plaquemines Parish, Louisiana, are 

home to families with some of the few black-owned oyster leases. Just as these leases have been 

threatened by freshwater diversion projects for coastal restoration, they could be threatened by Phase 2 of 

a catastrophic spill (Mock, 2010). 

The Gulf Coast hosts multiple minority and low-income groups whose use of natural resources of the 

offshore and coastal environments make them vulnerable to fishing closures. While not intended as an 

inventory of the area’s diversity, we have identified several Gulf Coast populations of particular concern. 

An estimated 20,000 Vietnamese American fishermen and shrimpers live along the Gulf Coast; by 1990, 

over 1 in 20 Louisiana fishers and shrimpers had roots in Southeast Asia even though they comprised less 

than half a percent of the State’s workforce (Bankston and Zhou, 1996). Vietnamese Americans account 

for about one-third of all the fishermen in the central Gulf of Mexico (Ravitz, 2010). Islaños, African 

Americans, and Native American groups are also engaged in commercial fishing and oystering. 

Historically, Vietnamese Americans and African Americans have worked in the fish processing and 

oyster shucking industries. Shucking houses particularly, have provided an avenue into the mainstream 

economy for minority groups. 

Therefore, fishing closures during Phase 2 of a catastrophic spill impacting the central Gulf of 

Mexico may disproportionately affect such minority groups as the Vietnamese Americans, Native 

Americans, African Americans, and Islaños (Hemmerling and Colten, 2003). 

Phase 3—Onshore Contact

While most coastal populations along the Gulf Coast are not generally minority or low income, 

several communities on the coasts of St. Mary, Lafourche, Terrebonne, St. Bernard, and Plaquemines 

Parishes, Louisiana, have minority or low-income population percentages that are higher than their state 

average. These minority populations are predominately Native American, Isleños, or African American. 

For example, a few counties or parishes along the Gulf Coast have more than a 2-percent Native 

American population (USDOI, MMS, 2007); about 2,250 Houma Indians (a State of Louisiana 

recognized tribe) are concentrated in Lafourche Parish, Louisiana, comprising 2.4 percent of the parish’s 

population, and about 800 Chitimacha (a federally recognized tribe) make up 1.6 percent of St. Mary 

Parish’s population. While these are not significant numbers on their own, viewed in the context of 

Louisiana’s overall 0.6 percent Native American average, these communities take on greater 

environmental justice importance.

Gulf Coast minority and low-income groups are particularly vulnerable to the coastal impacts of a 

catastrophic oil spill due to their greater than average dependence on the natural resources in the offshore 

and coastal environments. Besides their economic reliance on commercial fishing and oystering, coastal 

low-income and minority groups rely heavily on these fisheries and other traditional subsistence fishing, 

hunting, trapping, and gathering activities to augment their diets and household incomes (refer to 

Hemmerling and Colton, 2003, for an evaluation of environmental justice considerations for south 

Lafourche Parish). Regular commuting has continued this reliance on the natural resources of the coastal 
B-92 Central Planning Area Lease Sale 247 Supplemental EIS

environments even when populations have been forced to relocate because of landloss and the destruction 

from hurricane events.

State fishery closures because of a catastrophic oil spill could disproportionately affect minority and 

low-income groups. Shoreline impacts could generate additional subsistence-related effects. Therefore, 

these minority groups may be disproportionately affected if these coastal areas were impacted by a 

catastrophic spill and the resulting response.

Phase 4—Post-Spill, Long-Term Recovery and Response

After the spill is stopped, the primary environmental justice concerns relate to possible long-term 

health impacts to cleanup workers, a predominately minority population, and to possible disposal of oilimpacted solid waste in predominantly minority areas.

An analysis of socioeconomic characteristics shows that people of Cajun ethnicity in the Gulf Coast 

States are often found to be of a comparatively low socioeconomic status and to work jobs in the textile 

and oil industries (Henry and Bankston, 1999). Past studies suggest that a healthy offshore petroleum 

industry also indirectly benefits low-income and minority populations (Tolbert, 1995). One BOEMfunded study in Louisiana found income inequality decreased during the oil boom of the 1980’s and 

increased with the decline (Tolbert, 1995). If there is a suspension of oil and gas activities in response to 

a catastrophic spill, many oil- and gas-related service industries would attempt to avoid massive layoffs 

by cutting costs and deferring maintenance during the recovery. This was the case with the Deepwater 

Horizon explosion, oil spill, and response, and the long-term impacts are still not fully understood.

Onshore and Offshore Cleanup Workers 

By the end of a catastrophic spill, up to 25,000 (shallow water) or 50,000 (deepwater) personnel 

would be expected to be responding to the spill. The majority of these would be field responders (United 

Incident Command, 2010e). As seen by the Deepwater Horizon explosion, oil spill, and response, the 

racial composition of cleanup crews was so conspicuous that Ben Jealous, the president of the National 

Association for the Advancement of Colored People, sent a public letter to BP Chief Operations Officer 

Tony Hayward on July 9, 2010, demanding to know why African Americans were over-represented in 

“the most physically difficult, lowest paying jobs, with the most significant exposure to toxins” (National 

Association for the Advancement of Colored People, 2010). While regulations require the wearing of 

protective gear and only a small percentage of cleanup workers suffer immediate illness and injuries 

(Centers for Disease Control and Prevention, 2010), exposure could have long-term health impacts (e.g., 

increased rates of some types of cancer) (Savitz and Engel, 2010; Kirkeleit et al., 2008). Aguilera et al. 

(2010) compiled and reviewed existing studies on the repercussions of spilled oil exposure on human 

health for patterns of health effects and found evidence of the relationship between exposure and “acute 

physical, psychological, genotoxic, and endocrine effects in the exposed individuals.” Acute symptoms 

from exposure to oil, dispersants, and degreasers include headaches, nausea, vomiting, diarrhea, sore 

eyes, runny nose, sore throat, cough, nose bleeds, rash, blisters, shortness of breath, and dizziness 

(Sathiakumar, 2010). The USEPA’s monitoring data have not shown that the use of dispersants during 

the Deepwater Horizon explosion, oil spill, and response resulted in a presence of chemicals that 

surpassed human health benchmarks (Trapido, 2010). The potential for the long-term human health 

effects are largely unknown. However, the National Institute of Environmental Health Sciences is 

conducting a study known as the “Gulf Long-Term Follow-Up Study” that should provide a better 

understanding of the long-term and cumulative health impacts, such as the consequences of working close 

to a spill and of consuming contaminated seafood. The “Gulf Long-Term Follow-up Study” will monitor 

oil-spill cleanup workers for 10 years and represents a national effort to determine if the Gulf oil spill led 

to physical or mental health problems (U.S. Dept. of Health and Human Services, NIEHS, 2010). The 

study has a target goal of 55,000 participants. As of October 2012, the National Institute of 

Environmental Health Sciences announced that over 29,000 cleanup workers and volunteers have 

enrolled in the “Gulf Long-Term Follow-up Study” (U.S. Dept. of Health and Human Services, NIEHS, 

2012). Prior research on post-spill cleanup efforts found that the duration of cleaning work was a risk 

factor for acute toxic symptoms and that seamen had the highest occurrence of toxic symptoms compared 

with volunteers or paid workers. Therefore, participants in the “Vessels of Opportunity” program, which 

recruited local boat owners (including Cajun, Houma Indian, and Vietnamese American fishermen) to 
Catastrophic Spill Event Analysis B-93

assist in cleanup efforts, would likely be one of the most exposed groups. African Americans are thought 

to have made up a high percentage of the cleanup workforce. The Occupational Safety and Health 

Administration (OSHA) released two matrices of gear requirements for onshore and offshore Gulf 

operations that were organized by task (U.S. Dept. of Labor, OSHA, 2010a). Of past oil-spill workers, 

uninformed and poorly informed workers were at more risk of exposure and symptoms, demonstrating the 

importance of education and proper training of workers (Sathiakumar, 2010). Therefore, a catastrophic 

spill may disproportionately affect seamen and onshore workers such as Cajuns, Vietnamese Americans, 

Houma Indian, and African Americans. 

Solid-Waste Disposal 

Following a catastrophic spill, environmental justice concerns arise related to the disposal of cleanuprelated wastes near minority and/or low-income communities (Schleifstein, 2010). It is estimated that a 

catastrophic spill could generate several thousand tons of oil-impacted solid materials that would be 

disposed in landfills along the Gulf Coast. While no new landfills would be built because of a 

catastrophic spill, the use of existing landfills might exacerbate existing environmental justice issues. For 

example, Mobile, Alabama, and Miami, Florida, are majority minority urban centers with a majority of 

minority residents living within a 1-mi (1.6-km) radius of chosen landfills or liquid processing centers. 

While only a small percentage of Deepwater Horizon explosion, oil spill, and response waste was sent to 

these facilities—13 percent of the liquid waste to Liquid Environmental Solutions in Mobile and only 

0.28 percent of the total liquid waste to Cliff Berry in Miami—they may receive more from potential 

future spills. Disposal procedures for the Deepwater Horizon explosion, oil spill, and response involved 

sorting waste materials into standard “waste stream types” at small, temporary stations, and then sending 

each type to existing facilities that were licensed to dispose of them. The location of temporary sorting 

stations was linked to the location of containment and cleanup operations. Hence, future locations of any 

sorting stations are not predictable since they would be determined by the needs of cleanup operations. 

However, waste disposal locations were determined by the specializations of existing facilities and by 

contractual relationships between them and the cleanup and containment firms. Louisiana received about 

82 percent of the Deepwater Horizon explosion, oil spill, and response liquid waste recovered; of this, 

56 percent was manifested to mud facilities located in Venice in Plaquemines Parish, Louisiana, and to 

Port Fourchon in Lafourche Parish, Louisiana, and then transferred to a processing facility in Port Arthur, 

Texas. The waste remaining after processing was sent to deep well injection landfills located in Fannett 

and Big Hill, Texas. The sites located in Venice and Port Fourchon, Louisiana, and in Port Arthur, 

Fannett, and Big Hill, Texas, have low-minority populations, but a few of these areas have substantial 

poverty rates relative to State and parish/county means.

Overall Summary and Conclusion (Phases 1-4) 

For Phase 1 (Initial Event) of a catastrophic spill, there would likely be no adverse impacts to 

minority and low-income communities because of the long distance (>3 nmi; 3.5 mi; 5.6 km) from shore, 

as well as the short duration of the initial event, fire, and/or explosion. The primary environmental justice 

concerns during Phase 2 (Offshore Spill) would be large-scale fishing closures, oyster bed contamination 

and closures, and subsequent impacts to downstream activities such as shrimp processing facilities and 

oyster shucking houses. These may disproportionately affect such minority groups as the Vietnamese 

Americans, Native Americans, African Americans, and Islaños. Phase 3 (Onshore Contact), depending 

on the location, could result in disproportional impacts to those groups that rely heavily on oystering, 

commercial fishing, and other traditional subsistence fishing, hunting, trapping, and gathering activities to 

augment their diets and household incomes. During Phase 4 (Post-Spill, Long-Term Recovery and 

Response), the primary environmental justice concerns relate to possible long-term health impacts to 

cleanup workers, a predominately minority population, and to the possible disposal of oil-impacted solid 

waste in predominantly minority areas. As in the case of the Deepwater Horizon explosion, oil spill, and 

response, understanding long-term impacts would be dependent on the outcome of ongoing research by 

various interested parties, such as the National Institutes of Health and BOEM. Overall, depending on a 

number of mainly geographic variables such as the location of fisheries closures and oyster bed 

contamination and closures, as well as the demographic composition of cleanup workers, and if waste 
B-94 Central Planning Area Lease Sale 247 Supplemental EIS

disposal was not distributed across the region at many different facilities, a catastrophic oil-spill event 

may have disproportionate effects on minority and low-income populations. 

B.3.1.26. Species Considered due to U.S. Fish and Wildlife Service Concerns

Phase 1—Initial Event

Phase 1 of the scenario is the initiation of a catastrophic blowout incident. Impacts, response, and 

intervention depend on the spatial location of the blowout and leak. For this analysis, an explosion and 

subsequent fire are assumed to occur. If a blowout associated with the drilling of a single exploratory 

well occurs, this could result in a fire that would burn for 1 or 2 days. If a blowout occurs on a production 

platform, other wells could feed the fire, allowing it to burn for over a month. The drilling rig or platform 

may sink. If the blowout occurs in shallow water, the sinking rig or platform may land in the immediate 

vicinity; if the blowout occurs in deep water, the rig or platform could land a great distance away, beyond 

avoidance zones. Regardless of water depth, the immediate response would be from search and rescue 

vessels and aircraft, such as USCG cutters, helicopters, and rescue planes, and firefighting vessels. The 

potential impacts reflect the explosion, subsequent fire for 1-30 days, and the sinking of the platform in 

the immediate vicinity and up to 1 mi (1.6 km) from the well. 

The scenarios for each phase, including cleanup methods, can be found Table B-4. 

BOEM has only focused on species within coastal counties and parishes because those are the species 

that could be potentially impacted by oil and gas development activities, including a potential OCS spill. 

There would likely be no adverse impacts to the species considered due to FWS concerns as a result of 

the events and the potential impact-producing factors that could occur throughout Phase 1 of a 

catastrophic spill event due to the distance of most activities, the heavy regulation of infrastructure and 

pipelines, and permitting and siting requirements. 

Phase 2—Offshore Spill

Phase 2 of the analysis focuses on the spill and response in Federal and State offshore waters. A 

catastrophic spill would likely spread hundreds of square miles. Also, the oil slick may break into several 

smaller slicks, depending on local wind patterns that drive the surface currents in the spill area. The 

potential impacts reflect spill and response in Federal and State offshore waters. Season and temperature 

variations can result in different resource impacts due to variations in oil persistence and oil and 

dispersant toxicity and because of differences in potential exposure of the resources throughout various 

life cycle stages.

There would likely be no adverse impacts to the species considered due to FWS concerns as a result 

of the events and the potential impact-producing factors that could occur throughout Phase 2 of a 

catastrophic spill event due to the distance of most activities, the heavy regulation of infrastructure and 

pipelines, and permitting and siting requirements. 

Phase 3—Onshore Contact

Phase 3 focuses on nearshore (e.g., inside bays and in close proximity to shoreline) and onshore spill 

response and oil initially reaching the shoreline during the spill event or while the oil still persists in the 

offshore environment once the spillage has been stopped. It is likely that Phases 2 and 3 could occur 

simultaneously. The duration of the initial shoreline oiling is measured from initial shoreline contact until 

the well is capped or killed and the remaining oil dissipates offshore. Re-oiling of already cleaned or 

previously impacted areas could be expected during Phase 3. In addition to the response described in 

Phase 2, nearshore and onshore efforts would be introduced in Phase 3 as oil entered coastal areas and 

contacted shore. The potential impacts reflect the spill and response in very shallow coastal waters and 

once along the shoreline. Season and temperature variations can result in different resource impacts due 

to variations in oil persistence and oil and dispersant toxicity and because of differences in potential 

exposure of the resources throughout various life cycle stages.

The FWS has explicitly communicated interest in specific species within State boundaries along the 

Gulf Coast. The species within Louisiana, Mississippi, Alabama, and Florida have been designated as 

endangered, threatened, candidate, listed with critical habitat, proposed nonessential experimental 

population, or distinct vertebrate population. The greatest threats to the majority of these species are the 
Catastrophic Spill Event Analysis B-95

loss of and/or modification to suitable habitat caused by urban and agricultural development. Further 

detail on this catastrophic OSRA run is contained in Appendix C of the CPA 235/241/247 Supplemental 

EIS.

At this time, there is no known record of a hurricane crossing the path of a large oil spill; the impacts 

of such have yet to be determined. The experience from Hurricanes Katrina and Rita in 2005 was that the 

oil released during the storms widely dispersed as far as the surge reached (USDOC, NOAA, National 

Weather Service, 2012). Due to their reliance on terrestrial habitats to carry out their life-history 

functions at a considerable distance from the GOM, the activities of the CPA proposed action are unlikely 

to have significant adverse effects on the size and recovery of any of the FWS-mentioned species or 

populations in Texas, Louisiana, Mississippi, Alabama, and Florida. 

There would likely be no adverse impacts to the species considered due to FWS concerns as a result 

of the events and the potential impact-producing factors that could occur throughout Phase 3 of a 

catastrophic spill event due to the distance of most activities, the heavy regulation of infrastructure and 

pipelines, and permitting and siting requirements. 

Phase 4—Post-Spill, Long-Term Recovery and Response 

Phase 4 focuses on long-term recovery once the well has been capped and the spill has stopped. 

During the final phase of a catastrophic blowout and spill, it is presumed that the well has been capped or 

killed and cleanup activities are concluding. While it is assumed that the majority of spilled oil would be 

dissipated offshore within 1-2 months (depending on season and temperature) of stopping the flow, oil 

has the potential to persist in the environment long after a spill event and has been detected in sediment 

30 years after a spill. On sandy beaches, oil can sink deep into the sediments. In tidal flats and salt 

marshes, oil may seep into the muddy bottoms. The potential impacts reflect long-term persistence of oil 

in the environment and residual and long-term cleanup efforts.

As data continue to be gathered and impact assessments completed, a better characterization of the 

full scope of impacts to populations in the GOM from the Deepwater Horizon explosion, oil spill, and 

response will be available. Relevant data on the status of populations after the Deepwater Horizon

explosion, oil spill, and response may take years to acquire and analyze, and impacts from the Deepwater 

Horizon explosion, oil spill, and response may be difficult or impossible to discern from other factors. 

Therefore, it is not possible for BOEM to obtain this information within the timeline contemplated in this 

Supplemental EIS, regardless of the cost or resources needed. In light of the incomplete or unavailable 

information, BOEM’s subject-matter experts have used available scientifically credible evidence in this 

analysis and applied it using accepted methods and approaches. Nevertheless, a complete understanding 

of the missing information is not essential to a reasoned choice among alternatives for this Supplemental 

EIS. As of January 2016, there are 3,505 active leases in the CPA with either ongoing or the potential for 

exploration, drilling, and production activities. In addition, non-OCS energy-related activities will 

continue to occur in the CPA irrespective of the CPA proposed action (i.e., habitat loss and competition). 

The potential for effects from changes to the affected environment (post-Deepwater Horizon explosion, 

oil spill, and response), accidental spills (including low-probability catastrophic spills), and cumulative 

effects remains whether or not the No Action or an Action alternative is chosen under this Supplemental 

EIS.

There would likely be no adverse impacts to the species considered due to FWS concerns as a result 

of the events and the potential impact-producing factors that could occur throughout Phase 4 of a 

catastrophic spill event due to the distance of most activities, the heavy regulation of infrastructure and 

pipelines, and permitting and siting requirements. 

Overall Summary and Conclusion (Phases 1-4) 

Accidental blowouts, oil spills, and spill-response activities resulting from the CPA proposed action 

have the potential to impact small to large areas in the GOM, depending on the magnitude and frequency 

of accidents, the ability to respond to accidents, the location and date of accidents, and various 

meteorological and hydrological factors (including tropical storms). The incremental contribution of the 

CPA proposed action would not be likely to result in a significant incremental impact on the FWSmentioned species within the CPA; in comparison, non-OCS-related activities, such as habitat loss and 

competition, have historically proved to be of greater threat to the FWS-mentioned species.
B-96 Central Planning Area Lease Sale 247 Supplemental EIS

In conclusion, within the CPA, there is a long-standing and well-developed OCS Program (more than 

50 years); there are no data to suggest that activities from the preexisting OCS Program are significantly 

impacting the FWS mentioned species populations; therefore, the CPA proposed action would be 

expected to have little or no effect on the FWS-mentioned species.

B.4. PREPARERS

Pat Adkins, Information Management Specialist 

Bruce Baird, Biologist 

Mark Belter, Marine Biologist

Darice Breeding, Physical Scientist

Sindey Chaky, Social Scientist

Chris DuFore, Oceanographer

Stephanie Gambino, Chief, Biological/Social Sciences Section 

Donald (Tre) W. Glenn III, Protected Species Biologist 

Gary D. Goeke, Chief, Environmental Assessment Section 

Allison Hernandez, Protected Species Biologist 

Chester Huang, Meteorologist 

Nicole Hughes, Protected Species Biologist

Jack Irion, Unit Supervisor, Marine Archaeologist, Social Sciences Unit

Mark D. Jensen, Economist

Matthew Johnson, Marine Biologist

Doug Jones, Marine Archaeologist 

Arie R. Kaller, Unit Supervisor, Environmental Scientist, Biological Sciences Unit 

Lissa Lyncker, Unit Supervisor, Environmental Scientist, Environmental Assessment Section 

Jessica Mallindine, Protected Species Biologist

Megan Milliken, Economist

Tershara Matthews, Unit Supervisor, Environmental Scientist, Environmental Assessment Section

Margaret Metcalf, Chief, Physical/Chemical Sciences Unit

Deborah H. Miller, Technical Editor

David P. Moran, Biologist 

Mark Mueller, Marine Ecologist

Erin O’Reilly, Physical Scientist

Catherine A. Rosa, Environmental Assessment Program Specialist

Toby Wraye, Information Management Specialist 

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B-124 Central Planning Area Lease Sale 247 Supplemental EIS

Figure B-1. Location of Seven Hypothetical Oil-Spill Launch Points for OSRA within the Gulf of Mexico. 

(Spatial variability of the Loop Current is from Vukovich [2007] and is shown as percent of time that 

the Loop Current watermass is associated with a particular location.)
Catastrophic Spill Event Analysis B-125

Figure B-2. Spatial Frequency (%) of the Watermass Associated with the Loop Current in the Eastern Gulf of 

Mexico based on Data for the Period 1976-2003 (Vukovich, 2005).
B-126 Central Planning Area Lease Sale 247 Supplemental EIS

Figure B-3. Summary of Avian Species Collected by Date Obtained from the U.S. Fish and Wildlife Service as 

Part of the Deepwater Horizon Post-Spill Monitoring and Collection Process through May 12, 2011 

(USDOI, FWS, 2011a). (This figure represents the date the data were released and reported and does 

not represent the actual date individual birds were collected. Data on the Y-axis reflect the 

cumulative # of individual birds collected, identified, and summarized by date; data on the Z-axis 

reflect proportional change from one reporting date to the next. The data used in this figure are 

verified as per FWS’s QA/QC processes. The mean # of birds collected between intervals is 

184.4 + 89.3 SE [-807 min, 526 max for 13 collection intervals] and the mean % change between 

intervals is 3.0 + 1.3% [-11.12% min., 8.27% max]. We have no data on change in search effort 

temporally (or spatially) and also lack data prior to September 14, 2010; therefore, data at that point 

represent the baseline or “0” for determining interval differences. Disclaimer: All data should be 

considered provisional, incomplete, and subject to change. For more information, refer to FWS’s 

Weekly Bird Impact Data and Consolidated Wildlife Reports [USDOI, FWS, 2011a]; for additional 

information on the chronological change in number of birds collected, refer to Belanger et al., 2010).
Catastrophic Spill Event Analysis B-127

Table B-1

Blowout Scenarios and Key Differences in Impacts, Response, and/or Intervention

Location of Blowout and Leak Key Differences in Impacts, Response, and/or Intervention

Blowout occurs at the sea surface 

(i.e., at the rig)

Offers the least chance for oil recovery because of the restricted access to the 

release point; therefore, greater impacts to coastal ecosystems. In addition to 

relief wells, there is potential for other intervention measures such as capping 

and possible manual activation of blowout-preventer (BOP) rams.

Blowout occurs along the riser 

anywhere from the seafloor to the 

sea surface. However, a severed 

riser would likely collapse, 

resulting in a leak at the seafloor.

In deep water, the use of subsea dispersants, if approved, may reduce impacts 

to coastal ecosystems; however, their use may increase exposure of deepwater 

marine resources to dispersed oil. There is a possibility for limited recovery of 

oil at the source. In addition to relief wells, there is potential for other 

intervention measures, such as capping and possible manual activation of BOP 

rams.

At the seafloor, through leak paths 

on the BOP/wellhead

In deep water, the use of subsea dispersant, if approved, may reduce impacts to 

coastal ecosystems; however, their use may increase exposure of deepwater 

marine resources to dispersed oil.

With an intact subsea BOP, intervention may involve the use of drilling mud to 

kill the well. If the BOP and well stack are heavily compromised, the only 

intervention method may be relief wells. Greatest possibility for recovery of 

oil at the source, until the well is capped or killed.

Below the seafloor, outside the 

wellbore (i.e., broached)

Disturbance of a large amount of sediments resulting in the burial of benthic 

resources in the immediate vicinity of the blowout. The use of subsea 

dispersants would likely be more difficult (PCCI Marine and Environmental 

Engineering, 1999). Stopping this kind of blowout would probably involve 

relief wells. Any recovery of oil at the seabed would be very difficult.
B-128 Central Planning Area Lease Sale 247 Supplemental EIS

Table B-2

Properties and Persistence by Oil Component Group

Properties and

Persistence Light-Weight Medium-Weight Heavy-Weight

Hydrocarbon 

Compounds

Up to 10 carbon atoms 10-22 carbon atoms >20 carbon atoms

API o >31.1o 31.1o-22.3o <22.3o

Evaporation Rate Rapid (within 1 day) and 

complete

Up to several days; not 

complete at ambient 

temperatures

Negligible

Solubility in Water High Low (at most a few 

milligrams/liter)

Negligible

Acute Toxicity High because of 

monoaromatic 

hydrocarbons (BTEX)

Moderate because of 

diaromatic hydrocarbons 

(naphthalenes—2 ring 

PAHs)

Low except because of 

smothering (i.e., heavier oils 

may sink)

Chronic Toxicity None, does not persist 

because of evaporation

PAH components (e.g., 

naphthalenes—2 ring 

PAHs)

PAH components (e.g., 

phenanthrene, anthracene—

3 ring PAHs)

Bioaccumulation 

Potential

None, does not persist 

because of evaporation

Moderate Low, may bioaccumulate 

through sediment sorption

Compositional 

Majority

Alkanes and cycloalkanes Alkanes that are readily 

degraded

Waxes, asphaltenes, and 

polar compounds (not 

significantly bioavailable or

toxic)

Persistence Low because of 

evaporation

Alkanes readily degrade, 

but the diaromatic 

hydrocarbons are more 

persistent

High; very low degradation 

rates and can persist in 

sediments as tarballs or 

asphalt pavements

API = American Petroleum Institute.

BTEX = benzene, ethylbenzene, toluene, and xylene

PAH = polycyclic aromatic hydrocarbon

Sources: Michel, 1992; Canadian Center for Energy Information, 2010.
Catastrophic Spill Event Analysis B-129

Table B-3

Annual Volume of Produced Water Discharged by Depth

(millions of barrels)

Year Shelf

0-60 m

Shelf

60-200 m

Slope

200-400 m

Deepwater

400-800 m

Deepwater

800-1,600 m

UltraDeepwater

1,601-2,400 m

UltraDeepwater

>2,400 m

Total

2000 370.6 193.1 35.5 25.6 12.2 0.0 0.0 637.0

2001 364.2 185.2 35.0 32.0 16.6 0.0 0.0 633.0

2002 344.6 180.4 32.5 35.2 21.4 0.0 0.0 614.1

2003 359.4 182.9 31.2 39.0 35.5 0.2 0.0 648.2

2004 346.7 160.5 29.3 36.9 39.2 1.9 0.0 614.5

2005 270.1 113.5 23.1 33.5 43.0 5.8 0.0 489.0

2006 260.3 99.7 20.6 35.1 61.5 12.4 0.0 489.6

2007 307.0 139.4 22.2 40.0 70.3 15.5 0.1 594.5

2008 252.7 118.6 15.9 32.7 60.1 16.5 0.1 496.6

2009 263.9 108.3 19.9 39.2 65.3 25.0 0.1 521.7

Source: USDOI, BOEMRE, 2010b.
 B-130 Central Planning Area Lease Sale 247 Supplemental EIS

Table B-4 

Description of the Scenario for a Catastrophic Spill Event Occurring in Shallow Water or Deep Water 

(assumptions are described in detail in the text)

Scenario Shallow-Water Location Deepwater Location

Phase 1. Initial Event

Vertical Location of Blowout 4 possible locations including sea surface, along 

the riser, at the seafloor, and below the seafloor

4 possible locations including sea surface, along the riser, at 

the seafloor, and below the seafloor

Duration of Uncontrolled Fire 1-30 days 1-30 days

Phase 2. Offshore Spill

Duration of Spill 2-5 months 4-6 months

Rate of Spill 30,000 bbl per day 30,000-60,000 bbl per day

Total Volume of Spill (1) 0.9-3.0 MMbbl crude oil 2.7-7.2 MMbbl crude oil

10,000-20,000 bbl diesel fuel 

APIo Gravity Fresh oil will float (APIo >10) Fresh oil will float (APIo >10)

Characteristics of Oil Released Typical South Louisiana midrange paraffinic 

sweet crude oil 

Typical South Louisiana midrange paraffinic sweet crude 

oil; crude properties changed after oil traveled up the 

wellbore and passed through the water column, undergoing 

rapid depressurization and turbulence. Oil reached the 

surface as an emulsion stripped of many of its volatile 

components.

Response

Number of Vessels Up to 3,000 Up to 7,000

Number of Workers Up to 25,000 Up to 50,000

Number of Planes/Helicopters 25/50 50/100

Boom (million feet) 5 13.5

Dispersant Application

(surface application) (2)

35,000 bbl 33,000-bbl surface application and 16,500-bbl subsea 

application 

Number of Miles of Shoreline 

Requiring Some Measure of 

Mechanical or Manual Cleaning

778 778

In-situ Burn Yes, will occur Yes, will occur

Vessel Decontamination Stations Yes Yes

Severe Weather The potential for severe weather is noted, which 

could temporarily halt containment and response 

efforts.

The potential for severe weather is noted, which could 

temporarily halt containment and response efforts.

Fisheries Closure During the peak, anticipate approximately 37% or 

88,522 mi2 (229,270 km2) closed to recreational and 

commercial fishing.
Catastrophic Spill Event Analysis

B-131

Table B-4. Description of the Scenario for a Catastrophic Spill Event Occurring in Shallow Water or Deep Water (assumptions are described in detail in 

the text) (continued).

Scenario Shallow-Water Location Deepwater Location

Phase 3. Onshore Contact

Shoreline Oiling Duration 1-5 months 3-6 months

Response

Number of Staging areas 5-10 10-20

Number of Skimmers 200-300 500-600

Length of Shoreline Contacted

30 days1 = 0-50 miles2 30 days1 = 0-50 miles2

60 days = 50-100 miles 60 days = 50-100 miles

90 days = 100-1,000 miles 90 days = 100-1,000 miles

120 days = >1,000 miles 120 days = >1,000 miles 1 Not cumulative.

2 Length was extrapolated

Oil Characteristics and Appearance —Essentially stable emulsions mixed with sand.

—Typically initially stranded as surface layers and as 

discrete droplets/summer 2010.

Response Considerations for Sand 

Beaches

—No mechanical techniques allowed in some 

areas.

—Much of the beach cleanup conducted at night.

—Typically sand sieving, shaking, and sifting 

beach cleaning machines.

—Repetitive tilling and mixing using agriculture 

plows and discs in combination with beach 

cleaning machines.

—Sand washing treatment—sand sieve/shaker to 

remove debris and large oil particles and heated 

washing systems.

—Nearshore submerged oil difficult to recover 

and hard to locate; vacuums and snares could be 

used.

—No mechanical techniques allowed in some areas.

—Much of the beach cleanup conducted at night.

—Typically sand sieving, shaking, and sifting beach 

cleaning machines.

—Repetitive tilling and mixing using agriculture plows and 

discs in combination with beach cleaning machines.

—Sand washing treatment—sand sieve/shaker to remove 

debris and large oil particles and heated washing systems.

—Nearshore submerged oil difficult to recover and hard to 

locate; vacuums and snares could be used.

Response Considerations for Marshes —Lightly oiled—allowed to recovery naturally; 

degrade in place or removed by tidal or wave 

action.

—Moderately/heavily oiled—vacuumed or 

skimmed from boats possibly in conjunction with 

flushing; low-pressure flushing (with water 

comparable to marsh type); manual removal by 

—Lightly oiled—allowed to recovery naturally; degrade in 

place or removed by tidal or wave action.

—Moderately or heavily oiled—vacuumed or skimmed 

from boats possibly in conjunction with flushing; lowpressure flushing (with water comparable to marsh type); 

manual removal by hand or mechanized equipment; and 

vegetation cutting.
 B-132 Central Planning Area Lease Sale 247 Supplemental EIS

hand or mechanized equipment; and vegetation 

cutting.

—Heavily oiled areas—in-situ burning may be an 

option if water covers the sediment surface.

—Bioremediation may be utilized but mostly as a 

secondary treatment after bulk removal. 

—Heavily oiled areas—in-situ burning may be an option if 

water covers the sediment surface.

—Bioremediation may be utilized but mostly as a 

secondary treatment after bulk removal.

Response Considerations for 

Nearshore Waters

Marsh areas—skimming and vacuum (in areas too 

shallow to use skimmers) systems used in 

conjunction with flushing, and booming to 

temporarily contain mobile slicks.

Marsh areas—skimming and vacuum (in areas too shallow 

to use skimmers) systems used in conjunction with flushing, 

and booming to temporarily contain mobile slicks.

Phase 4. Recovery Phase

Response

Number of Vessels 

– 24-36 months post-spill/greater 

than 36 months

Fewer than 10/0 designated—called up only if 

new residual oil reported 

Fewer than 10/0 designated—called up only if new residual 

oil reported

Number of Workers 

– 24-36 months post-spill/greater 

than 36 months

230/0 designated—called up only if new residual 

oil reported 

230/0 designated—called up only if new residual oil 

reported

Miles of Shoreline Undergoing 

Regular Patrolling and 

Maintenance 

– 30-36 months post-spill/greater 

than 36 months

Fewer than 20/0 Fewer than 20/0

End Date for Dispersant 

Application

No dispersant usage 2 weeks after spillage ends No dispersant usage 2 weeks after spillage ends

Remaining Sources of Unrecoverable 

Weathered Oil

Buried or in surface pockets in coastal sand, 

sediment, or muddy bottoms and in pockets on the 

seafloor.

Buried or in surface pockets in coastal sand, sediment, or 

muddy bottoms and in pockets on the seafloor.

Oil Characteristics and Appearance As stranded oil weathered, some became buried through 

natural beach processes and appeared as surface residual 

balls (SRB) <10 cm (4 in) or as patties (SRP) 10 cm-1 m 

(4 in-3 ft).

Response Considerations for Sand 

Beaches, Marshes, and Nearshore 

Waters

See Phase 3 above. See Phase 3 above.

(1) A blowout may contain crude oil, natural gas, and condensate. Because the majority of environmental damage is due to the release of oil, this text 

assumes the spill to be an oil spill. However, a natural gas release would result in a less visible and less persistent adverse impact than an oil release.

(2) Subsea dispersal application must be individually approved.

Source: British Petroleum, 2014b.
Catastrophic Spill Event Analysis

B-133

Table B-5 

Birds Collected and Summarized by the U.S. Fish and Wildlife Service: 

Post-Deepwater Horizon Explosion, Oil Spill, and Response in the Gulf of Mexico1, 2

Common Name Species 

Group3

Grand 

Total

Visibly Oiled Not Visibly Oiled Unknown Oiling Oiling 

Rate4 Dead Alive Total Dead Alive Total Dead Alive Total

Amer. Coot Marsh/Wading 3 2 2 2 0 0 0 1 0 1 0.67

Amer. Oystercatcher Shorebird 13 7 3 7 3 0 3 1 3 3 0.54

Amer. Redstart Passerine 1 0 0 0 1 0 1 0 0 0 0.00

Amer. White Pelican Seabird 19 5 3 8 4 0 4 4 8 7 0.42

Audubon’s Shearwater Seabird 36 1 1 1 35 0 35 0 2 0 0.03

Barn Owl Raptor 1 0 0 0 1 0 1 0 0 0 0.00

Barn Swallow Passerine 1 1 0 1 0 0 0 0 0 0 1.00

Belted Kingfisher Passerine 1 0 0 0 1 0 1 0 1 0 0.00

Bl.-crown. Night Heron Marsh/Wading 18 6 3 8 7 0 7 1 4 3 0.44

Black Skimmer Seabird 253 51 16 55 153 0 153 40 14 45 0.22

Black Tern Seabird 9 1 0 1 7 0 7 1 3 1 0.11

Bl.-bell. Whistl. Duck Waterfowl 2 0 0 0 0 0 0 0 2 2 0.00

Black-necked Stilt Shorebird 3 0 0 0 3 0 3 0 0 0 0.00

Blue-winged Teal Waterfowl 6 0 0 0 6 0 6 0 0 0 0.00

Boat-tailed Grackle Passerine 1 0 0 0 1 0 1 0 1 0 0.00

Broad-winged Hawk Raptor 1 0 0 0 1 0 1 0 1 0 0.00

Brown Pelican Seabird 826 152 227 339 248 0 248 177 149 239 0.41

Brown-headed Cowbird Passerine 1 0 0 0 0 0 0 0 1 1 0.00

Bufflehead Waterfowl 1 0 1 1 0 0 0 0 0 0 1.00

Canada Goose Waterfowl 4 0 1 1 1 0 1 1 2 2 0.25

Caspian Tern Seabird 17 7 3 8 4 0 4 2 6 5 0.47

Cattle Egret Marsh/Wading 36 4 4 7 25 0 25 3 4 4 0.19

Clapper Rail Marsh/Wading 120 27 5 29 64 0 64 20 14 27 0.24
 B-134 Central Planning Area Lease Sale 247 Supplemental EIS

Table B-5. Birds Collected and Summarized by the U.S. Fish and Wildlife Service: Post-Deepwater Horizon Explosion, Oil Spill, and Response in the 

Gulf of Mexico1, 2 (continued).

Common Name Species 

Group3

Grand 

Total

Visibly Oiled Not Visibly Oiled Unknown Oiling Oiling 

Rate4

Dead Alive Total Dead Alive Total Dead Alive Total

Common Loon Diving 75 33 27 39 24 0 24 4 20 12 0.52

Common Moorhen Marsh/Wading 4 1 0 1 3 0 3 0 0 0 0.25

Common Nighthawk Passerine 1 0 0 0 0 0 0 0 1 1 0.00

Common Tern Seabird 25 15 12 16 9 0 9 0 0 0 0.64

Common Yellowthroat Passerine 2 0 0 0 2 0 2 0 0 0 0.00

Cooper’s Hawk Raptor 1 0 0 0 1 0 1 0 1 0 0.00

Cory’s Shearwater Seabird 4 0 0 0 3 0 3 0 1 1 0.00

Dbl-crest. Cormorant Diving 23 2 1 2 17 0 17 2 7 4 0.09

Eastern Kingbird Passerine 2 1 0 1 1 0 1 0 0 0 0.50

Eastern Meadowlark Passerine 1 0 0 0 1 0 1 0 0 0 0.00

Eur. Collared-dove Passerine 1 0 0 0 1 0 1 0 0 0 0.00

Eur. Starling Passerine 2 0 1 1 1 0 1 0 0 0 0.50

Forster’s Tern Seabird 40 17 8 20 12 0 12 6 7 8 0.50

Fulvous Whistl. Duck Waterfowl 1 0 0 0 0 0 0 0 1 1 0.00

Glossy Ibis Marsh/Wading 2 1 1 1 1 0 1 0 0 0 0.50

Great Blue Heron Marsh/Wading 42 5 3 6 26 0 26 4 16 10 0.14

Great Cormorant Diving 1 0 0 0 1 0 1 0 0 0 0.00

Great Egret Marsh/Wading 31 6 6 7 15 0 15 8 3 9 0.23

Great-horned Owl Raptor 1 0 0 0 1 0 1 0 0 0 0.00

Greater Shearwater Seabird 89 7 4 7 55 0 55 27 4 27 0.08

Green Heron Marsh/Wading 16 2 0 2 8 0 8 1 6 6 0.13

Gull-billed Tern Seabird 4 0 0 0 2 0 2 2 4 2 0.00

Herring Gull Seabird 31 10 11 13 10 0 10 2 13 8 0.42

House Sparrow Passerine 2 0 0 0 2 0 2 0 1 0 0.00

Killdeer Shorebird 3 0 0 0 3 0 3 0 0 0 0.00
Catastrophic Spill Event Analysis

B-135

Table B-5. Birds Collected and Summarized by the U.S. Fish and Wildlife Service: Post-Deepwater Horizon Explosion, Oil Spill, and Response in the 

Gulf of Mexico1, 2 (continued).

Common Name Species 

Group3

Grand 

Total

Visibly Oiled Not Visibly Oiled Unknown Oiling Oiling 

Rate4

Dead Alive Total Dead Alive Total Dead Alive Total

King rail Marsh/Wading 1 0 0 0 0 0 0 0 1 1 0.00

Laughing Gull Seabird 2,981 1,025 355 1,182 1,390 0 1,390 304 371 409 0.40

Leach’s Storm-petrel Seabird 1 1 0 1 0 0 0 0 1 0 1.00

Least Bittern Marsh/Wading 4 0 0 0 4 0 4 0 2 0 0.00

Least Tern Seabird 106 46 7 49 43 0 43 12 3 14 0.46

Less. Bl.-backed Gull Seabird 4 1 1 1 1 0 1 1 2 2 0.25

Less. Scaup Waterfowl 1 0 0 0 0 0 0 1 0 1 0.00

Little Blue Heron Marsh/Wading 5 0 0 0 4 0 4 1 1 1 0.00

Long-bill. Dowitcher Shorebird 1 0 0 0 0 0 0 0 1 1 0.00

Magnif. Frigatebird Seabird 8 3 3 4 2 0 2 1 2 2 0.50

Mallard Waterfowl 26 5 4 6 16 0 16 0 7 4 0.23

Manx Shearwater Seabird 6 1 0 1 5 0 5 0 0 0 0.17

Masked Booby Seabird 9 4 3 4 1 0 1 0 4 4 0.44

Mottled Duck Waterfowl 6 0 0 0 5 0 5 1 1 1 0.00

Mourning Dove Passerine 15 3 1 3 8 0 8 0 6 4 0.20

Muscovy Duck Waterfowl 1 0 0 0 1 0 1 0 1 0 0.00

Neotropic Cormorant Diving 5 0 0 0 2 0 2 3 0 3 0.00

Northern Cardinal Passerine 3 0 0 0 3 0 3 0 0 0 0.00

Northern Gannet Seabird 475 225 189 297 99 0 99 30 107 79 0.63

Northern Mockingbird Passerine 5 0 0 0 4 0 4 0 2 1 0.00

Osprey Raptor 11 2 1 3 6 0 6 0 3 2 0.27

Pied-billed Grebe Diving 32 18 24 24 7 0 7 1 3 1 0.75

Piping Plover Shorebird 1 0 0 0 1 0 1 0 0 0 0.00

Purple Gallinule Marsh/Wading 2 0 0 0 2 0 2 0 0 0 0.00

Purple Martin Passerine 5 1 0 1 3 0 3 0 1 1 0.20
 B-136 Central Planning Area Lease Sale 247 Supplemental EIS

Table B-5. Birds Collected and Summarized by the U.S. Fish and Wildlife Service: Post-Deepwater Horizon Explosion, Oil Spill, and Response in the 

Gulf of Mexico1, 2 (continued).

Common Name Species 

Group3

Grand 

Total

Visibly Oiled Not Visibly Oiled Unknown Oiling Oiling 

Rate4

Dead Alive Total Dead Alive Total Dead Alive Total

Red-breasted Merg. Waterfowl 2 1 1 1 1 0 1 0 1 0 0.50

Reddish Egret Marsh/Wading 2 1 1 1 1 0 1 0 1 0 0.50

Red-shouldered Hawk Raptor 1 0 0 0 0 0 0 0 1 1 0.00

Red-tailed Hawk Raptor 1 0 0 0 1 0 1 0 0 0 0.00

Red-winged Blackbird Passerine 1 0 0 0 1 0 1 0 0 0 0.00

Ring-billed Gull Seabird 2 0 1 1 1 0 1 0 0 0 0.50

Rock Dove (pigeon) Passerine 16 2 2 3 4 0 4 2 10 9 0.19

Roseate Spoonbill Marsh/Wading 15 7 3 7 3 0 3 5 1 5 0.47

Royal Tern Seabird 289 116 66 149 104 0 104 19 47 36 0.52

Ruddy Duck Waterfowl 1 1 0 1 0 0 0 0 0 0 1.00

Ruddy Turnstone Shorebird 13 1 3 3 8 0 8 1 5 2 0.23

Sanderling Shorebird 26 4 2 4 20 0 20 1 6 2 0.15

Sandwich Tern Seabird 70 28 20 34 25 0 25 8 14 11 0.49

Seaside Sparrow Passerine 9 4 0 4 5 0 5 0 0 0 0.44

Semipalm. Sandpiper Shorebird 3 2 1 3 0 0 0 0 0 0 1.00

Short-bill. Dowitcher Shorebird 1 0 0 0 1 0 1 0 0 0 0.00

Snowy Egret Marsh/Wading 22 12 9 14 6 0 6 2 3 2 0.64

Sooty Shearwater Seabird 1 0 0 0 0 0 0 0 1 1 0.00

Sooty Tern Seabird 3 0 1 1 2 0 2 0 1 0 0.33

Sora Marsh/Wading 5 2 1 2 1 0 1 2 0 2 0.40

Spotted Sandpiper Shorebird 1 0 0 0 1 0 1 0 0 0 0.00

Surf Scoter Waterfowl 1 1 1 1 0 0 0 0 0 0 1.00

Tri-colored Heron Marsh/Wading 31 9 5 11 7 0 7 11 2 13 0.35

Virginia Rail Marsh/Wading 3 0 0 0 3 0 3 0 1 0 0.00

White Ibis Marsh/Wading 7 1 1 1 4 0 4 2 3 2 0.14
Catastrophic Spill Event Analysis

B-137

Table B-5. Birds Collected and Summarized by the U.S. Fish and Wildlife Service: Post-Deepwater Horizon Explosion, Oil Spill, and Response in the 

Gulf of Mexico1, 2 (continued).

Common Name Species 

Group3

Grand 

Total

Visibly Oiled Not Visibly Oiled Unknown Oiling Oiling 

Rate4

Dead Alive Total Dead Alive Total Dead Alive Total

White-tail. Tropicbird Seabird 1 0 0 0 1 0 1 0 0 0 0.00

White-wing. Dove Passerine 1 0 0 0 1 0 1 0 0 0 0.00

Willet Shorebird 13 2 1 3 8 0 8 1 3 2 0.23

Wilson’s Plover Shorebird 3 0 0 0 2 0 2 1 0 1 0.00

Yellow-billed Cuckoo Passerine 2 2 0 2 0 0 0 0 0 0 1.00

Yel.-cr. Night Heron Marsh/Wading 9 1 0 1 7 0 7 0 3 1 0.11

Unid. Blackbird Passerine 1 0 0 0 0 0 0 0 1 1 0.00

Unid. Booby Seabird 1 0 0 0 1 0 1 0 1 0 0.00

Unid. Cormorant Diving 14 3 0 3 10 0 10 1 0 1 0.21

Unid. Dowitcher Shorebird 2 1 0 1 1 0 1 0 1 0 0.50

Unid. Duck Waterfowl 2 0 0 0 1 0 1 1 0 1 0.00

Unid. Egret Marsh/Wading 15 2 0 2 11 0 11 2 1 2 0.13

Unid. Flycatcher Passerine 1 1 0 1 0 0 0 0 0 0 1.00

Unid. Grebe Diving 4 2 1 2 2 0 2 0 0 0 0.50

Unid. Gull Seabird 248 79 1 80 134 0 134 33 4 34 0.32

Unid. Hawk Raptor 2 0 0 0 2 0 2 0 0 0 0.00

Unid. Heron Marsh/Wading 15 5 0 5 8 0 8 1 1 2 0.33

Unid. Loon Diving 7 2 2 4 3 0 3 0 1 0 0.57

Unid. Mockingbird Passerine 1 0 0 0 1 0 1 0 0 0 0.00

Unid. Owl Raptor 1 0 0 0 1 0 1 0 0 0 0.00

Unid. Passerine Passerine 1 0 0 0 1 0 1 0 0 0 0.00

Unid. Pelican Seabird 25 5 1 5 15 0 15 4 1 5 0.20

Unid. Pigeon Passerine 14 2 1 3 6 0 6 1 6 5 0.21

Unid. Rail Marsh/Wading 4 1 0 1 3 0 3 0 0 0 0.25

Unid. Raptor Raptor 1 0 0 0 1 0 1 0 0 0 0.00
 B-138 Central Planning Area Lease Sale 247 Supplemental EIS

Table B-5. Birds Collected and Summarized by the U.S. Fish and Wildlife Service: Post-Deepwater Horizon Explosion, Oil Spill, and Response in the 

Gulf of Mexico1, 2 (continued).

Common Name Species 

Group3

Grand 

Total

Visibly Oiled Not Visibly Oiled Unknown Oiling Oiling 

Rate4

Dead Alive Total Dead Alive Total Dead Alive Total

Unid. Sandpiper Shorebird 2 0 0 0 2 0 2 0 2 0 0.00

Unid. Shearwater Seabird 6 0 0 0 5 0 5 1 0 1 0.00

Unid. Shorebird Shorebird 3 2 0 2 0 0 0 1 0 1 0.67

Unid. Skimmer Seabird 6 0 0 0 5 0 5 1 0 1 0.00

Unid. Sparrow Passerine 3 0 0 0 1 0 1 2 0 2 0.00

Unid. Swallow Passerine 1 0 0 0 1 0 1 0 0 0 0.00

Unid. Tern Seabird 132 38 1 39 79 0 79 13 2 14 0.30

Unid. Warbler Passerine 1 0 0 0 1 0 1 0 0 0 0.00

Unknown spp. 593 51 2 53 451 0 451 88 1 89 0.09

Other 106 31 3 34 52 0 52 7 14 20 0.32

Column Totals 7,258 2,121 2,642 3,387 3,387 873 1,229 0.24 1 Data obtained from the U.S. Fish and Wildlife Service (FWS) as part of the Deepwater Horizon post-spill monitoring and collection process are summarized for May 12, 

2011 (USDOI, FWS, 2011a). The data used in this table are verified as per FWS’s QA/QC processes. Disclaimer: All data should be considered provisional, incomplete, 

and subject to change (USDOI, FWS, 2011a). For more information, refer to the Weekly Bird Impact Data and Consolidated Wildlife Reports. Numbers in this table have

been verified against the original data from FWS’s website (USDOI, FWS, 2011a). 2 As of May 12, 2011, 104 avian species had been collected and identified through the Deepwater Horizon post-spill monitoring and collection process (USDOI, FWS, 

2011a). Note: Though the process was triggered by the Deepwater Horizon explosion and oil spill, not all birds recovered were oiled (36% = oiled, 47% = unoiled, 17% = 

unknown), suggesting that “search effort” alone accounted for a large proportion of the total (n = 7,258) birds collected (Piatt et al., 1990a, page 127). Some of the live 

birds collected may have been incapable of flight due to age or molt, and some of the dead birds collected may have died due to natural mortality, predation, or other 

anthropogenic sources of mortality. The overall oiling rate across species including “others” and “unknowns” was 0.24 versus 0.25 for individuals identified to species. 

The oiling rate for the Top 5 (see bold rows in table) most-impacted avian species was 0.43 and included representatives only from the seabird group. These are listed in 

descending order based on the number collected: laughing gull (2,981 collected, 0.40 oiling rate); brown pelican (826 collected, 0.41 oiling rate); northern gannet 

(475 collected, 0.63 oiling rate); royal tern (289 collected, 0.52 oiling rate); and black skimmer (253 collected, 0.22 oiling rate). Note: There is a difference between the 

table structure here compared with the original table on FWS’s website. Herein, columns for live birds that later died were not included. Totals associated with each larger 

grouping are correct and sum to those column totals for the May 12, 2011, Collection Report values. Six new species or rows were added and 3 species were removed 

between the December 14, 2010, Collection Report (USDOI, FWS, 2010d) and the May 12, 2011, Collection Report (USDOI, FWS, 2011a). The major difference in 

number (-807) between the more recent and older versions was due to an ~10% overestimate in the previous report representing live birds that later died, as these individuals 

were counted twice in the December 14, 2010, Collection Report (USDOI, FWS, 2010d). 3 For additional information on oiling rates by Species Group and additional statistics, refer to Table 4-12 of the 2012-2017 WPA/CPA Multisale EIS.
Catastrophic Spill Event Analysis

B-139

Table B-5. Birds Collected and Summarized by the U.S. Fish and Wildlife Service Post-Deepwater Horizon Explosion, Oil Spill, and Response in the Gulf 

of Mexico1, 2 (continued).

4 Oiling Rate: For each species, an oiling rate was calculated by dividing the “total” number of oiled individuals (∑ alive + dead) /∑ of total individuals collected for a given 

species/row. In general, it has been well documented that the number of birds collected after a spill event represents a small fraction of the total oiled population (direct 

mortality) due to various factors: species-specific differences in vulnerability to spilled oil, species-specific differences in distribution, habitat use and behavior; speciesspecific differences in abundance; species-specific differences in carcass deposition rates, persistence rates, and detection probabilities; overall search effort and temporal 

and spatial variation in search effort; and carcass loss due to predation, habitat, weather, tides, and currents (Piatt et al., 1990a and 1990b; Ford et al., 1996; Piatt and Ford, 

1996; Fowler and Flint, 1997; Flint and Fowler, 1998; Flint et al., 1999; Hampton and Zafonte, 2005; Ford, 2006; Castège et al., 2007; Ford and Zafonte, 2009; Byrd et al., 

2009; Flint et al., 2010). For example, Piatt and Ford (1996, Table 1) estimated a mean carcass recovery rate of only 17% for a number of previous oil-bird impact studies. 

Burger (1993) and Wiese and Jones (2001) estimated recovery rates of 20% with the latter study based on a drift-block design to estimate carcass recovery rate from 

beached-bird surveys. Due to the fact that the coastline directly inshore of the well blowout location is primarily marsh and not sandy beaches, due to the distance from the 

blowout location to the coast, and due to predominant currents and wind directions during the event, the number of birds collected will likely represent a recovery estimate 

in the lower ranges of those provided in the literature to date (≤10%). A range of mortality estimates given the total number of dead birds collected through May 12, 2011, 

of 7,258 birds x recovery rates from the literature (0-59% in Piatt and Ford, 1996, Table 1) suggests a lower range of 12,302 birds* (59% recovery rate), an upper range of 

725,800 birds* (0% recovery rate), and 42,694 birds based on the 17% mean recovery rate from Piatt and Ford (1996). The lower range of estimates (i.e., high carcass 

recovery rates) is likely biased low because it assumes no search effort after May 2011 (i.e., no more birds were collected after that date) and does not account for any of the 

detection probability parameters that are currently unknown. The actual avian mortality estimate will likely not be available until the NRDA process has been completed; 

this should include a combination of carcass drift experiments, drift-block experiments, corrections for carcass deposition and persistence rates, scavenger rates, and 

detection probability with additional modeling to more precisely derive an estimate. For additional information on oiling rates by Species Group and additional statistics, 

refer to Table 4-12 of the 2012-2017 WPA/CPA Multisale EIS. Note: Spill volume tends to be a poor predictor of bird mortality associated with an oil spill (Burger, 1993), 

though it should be considered for inclusion in any models to estimate total bird mortality, preferably with some metric of species composition and abundance (preferably 

density) pre-spill (Wilhelm et al., 2007). 

* Corrected values are based on revisiting the original calculations after publication of the 2012-2017 WPA/CPA Multisale EIS. An additional estimate for total mortality 

based on Piatt and Ford (1996) is also provided.
 B-140 Central Planning Area Lease Sale 247 Supplemental EIS

Table B-6 

Federally Listed Avian Species Considered by State and Associated Planning Area in the Gulf of Mexico1

Species Status Critical Habitat IUCN Red List

Status2 States Planning Area

Red-cockaded Woodpecker Endangered No rules published Vulnerable AL, FL, LA, MS, TX WPA, CPA, EPA

Least Tern3 Endangered No rules published Least Concern AL, LA, TX (FL, MS) WPA, CPA, EPA

Piping Plover Threatened Designated Near Threatened AL, FL, LA, MS, TX WPA, CPA, EPA

Roseate Tern Threatened No rules published Least Concern FL only EPA

Wood Stork Endangered No rules published Least Concern AL, FL, MS CPA, EPA

Whooping Crane Endangered Designated Endangered TX, LA4, FL4 WPA, CPA, EPA

Mississippi Sandhill Crane Endangered Designated Not Yet Assessed MS only CPA

Attwater’s Prairie Chicken Endangered No rules published Not Yet Assessed TX only WPA

N. Aplomado Falcon Endangered No rules published Not Yet Assessed TX only WPA

Everglades Snail Kite Endangered Designated Not Yet Assessed FL only EPA

Cape Sable Seaside Sparrow Endangered Designated Not Yet Assessed FL only EPA

Audubon’s Crested Caracara Threatened No rules published Not Yet Assessed FL only EPA

Sprague’s Pipit Candidate NA – Priority 2 Vulnerable LA, TX WPA, CPA

Bald Eagle Delisted No rules published Least Concern AL, FL, LA, MS, TX WPA, CPA, EPA

Peregrine Falcon Delisted Designated Least Concern AL, FL, LA, MS, TX WPA, CPA, EPA

Eastern Brown Pelican Delisted No rules published Least Concern AL, FL, LA, MS, TX WPA, CPA, EPA

Red Knot Proposed 

Threatened

NA – proposed threatened Least Concern FL, LA, TX WPA, CPA, EPA

1 Information contained in this table was obtained via an email attachment from the U.S. Fish and Wildlife Service (FWS) on April 6, 2012 (USDOI, FWS, 2012) and from 

FWS’s “Endangered Species” website and associated queries for “species” available from FWS’s website (USDOI, FWS, 2011b). Additional information for each species 

can be found at NatureServe Explorer (2011). Note: All species listed in this table are considered, but only the piping plover, roseate tern, whooping crane, wood stork, 

Mississippi sandhill crane, bald eagle, eastern brown pelican, and red knot will be analyzed. 2 International Union for Conservation of Nature (IUCN) – The Red List classifies species as imperiled (Critically Endangered, Endangered, or Vulnerable), not imperiled 

(Near Threatened or Least Concern), extinct (Extinct, Extinct in the Wild), or Data Deficient (Butchart et al., 2004 and 2005; Harris et al., 2012). If species meet the 

quantitative thresholds of any of the following criteria, they will be added to the Red List: (1) decline in population size; (2) small geographic range; (3) small population 

size plus decline; (4) very small population size; or (5) quantitative analysis. 3 The Interior population of the least tern was listed as endangered on May 28, 1985 (Federal Register, 1985) throughout much of its breeding range in the Midwest. This 

designation does not provide or extend Endangered Species Act (ESA) protection to the breeding population of Gulf Coast “population” of least terns. Similarly, ESA 

protection for breeding least terns only applies to certain segments or areas (inland rivers and lakes ~50 mi [80 km] inland) of Louisiana, Mississippi, and Texas. 4 The whooping crane is considered endangered throughout its range in the U.S. except where nonessential, experimental flocks have been established. More recently, a 

release site (White Lake Wetlands Conservation Area, Vermilion Parish) was added in Louisiana (Table 4-14 of the 2012-2017 WPA/CPA Multisale EIS) with a release of

10 birds on February 22, 2011. To date, only 3 of the original 10 released cranes remain; an additional release of 16 cranes occurred on December 1, 2011. The Gulf Coast 

States that have these nonessential, experimental flocks include Alabama, Louisiana, Mississippi, and Florida; as well, wild whooping cranes may rarely occur as transients 

in Mississippi and Alabama, but they are not known to breed in either state. 5 The red knot is currently a proposed threatened species as of September 30, 2013 (Federal Register, 2013).
KEYWORD INDEX

Keyword Index Keywords-3 

KEYWORD INDEX

Air Quality, x, 1-16, 2-6, 2-7, 2-8, 3-10, 3-13, 4-7, 4-8, 4-9, 4-10, 4-11, 4-65, 4-106, 4-111 

Alternate Use, 4-13 

Alternative Energy, 4-13 

Archaeological Resources, x, xiv, 1-16, 2-6, 2-7, 2-8, 3-6, 4-8, 4-84, 4-85, 4-86, 4-87, 4-88, 4-89, 4-90, 

4-106, 4-112, 4-113 

Artificial Reefs, xiv, 1-16, 2-6, 3-28, 3-30, 3-31, 4-29, 4-73, 4-79, 4-80, 4-85, 4-86, 4-88, 4-89, 4-114 

Beach Mice, 4-62, 4-63, 4-64, 4-103, 4-106 

Blowout Preventer, 3-25 

Blowouts, 1-8, 3-25 

Catastrophic Spill, viii, xi, xiv, 2-9, 3-18, 3-19, 4-4, 4-5, 4-8, 4-9, 4-13, 4-15, 4-19, 4-20, 4-21, 4-22, 4-23, 

4-25, 4-27, 4-30, 4-31, 4-32, 4-33, 4-39, 4-40, 4-41, 4-42, 4-43, 4-44, 4-45, 4-46, 4-47, 4-53, 4-54, 

4-55, 4-57, 4-59, 4-60, 4-63, 4-65, 4-70, 4-71, 4-74, 4-77, 4-79, 4-83, 4-85, 4-88, 4-91, 4-95, 4-97, 

4-100, 4-102, 4-104, 4-110 

Chemosynthetic Communities, xii, 1-16, 2-6, 3-11, 4-39, 4-40, 4-41, 4-42, 4-44 

Chemosynthetic Deepwater Benthic Communities, 2-9, 4-39, 4-72 

Coastal and Marine Birds, x, xiii, 2-7, 2-8, 2-9, 4-5, 4-64, 4-65, 4-66, 4-67, 4-68, 4-69, 4-106, 4-111 

Coastal Barrier Beaches, x, xi, 2-7, 2-8, 4-17, 4-18, 4-19, 4-20, 4-21, 4-106 

Coastal Infrastructure, xiv, 2-7, 2-9, 3-3, 3-15, 3-16, 3-27 

Coastal Spills, 3-14, 3-20, 3-21 

Coastal Zone Management, x, 1-6, 1-13, 1-16, 4-4, 5-8 

Collisions, viii, xi, xiv, xv, 3-25, 3-26, 3-33, 4-12, 4-15, 4-18, 4-23, 4-30, 4-56, 4-66, 4-67, 4-68, 4-69, 

4-91, 4-95, 4-99, 4-100, 4-110, 4-111 

Commercial Fisheries, x, xiii, 2-7, 2-9, 4-67, 4-76, 4-77, 4-78, 4-106, 4-111, 4-112 

Commercial Fishing, x, xiii, 2-5, 4-67, 4-76, 4-77, 4-78, 4-106, 4-111, 4-112 

Consultation and Coordination, viii, 1-6, 1-7, 2-5, 3-17, 5-11 

Cumulative Activities, viii, xiii, 3-26, 3-27, 3-28, 3-29, 3-30, 3-31, 4-4, 4-61, 4-63 

Cumulative Impacts, viii, x, 1-5, 3-27, 3-28, 3-32, 4-3, 4-4, 4-8, 4-9, 4-10, 4-11, 4-12, 4-13, 4-14, 4-15, 

4-17, 4-19, 4-21, 4-22, 4-24, 4-25, 4-26, 4-27, 4-28, 4-30, 4-31, 4-33, 4-35, 4-36, 4-37, 4-39, 4-40, 

4-41, 4-43, 4-44, 4-45, 4-47, 4-48, 4-49, 4-50, 4-51, 4-52, 4-55, 4-56, 4-57, 4-59, 4-60, 4-62, 4-63, 

4-64, 4-66, 4-69, 4-70, 4-71, 4-72, 4-74, 4-76, 4-77, 4-78, 4-79, 4-80, 4-81, 4-83, 4-84, 4-85, 4-87, 

4-88, 4-90, 4-91, 4-92, 4-95, 4-97, 4-98, 4-99, 4-100, 4-101, 4-103, 4-104, 4-106, 4-108, 4-113, 5-4 

Decommissioning, xii, xiv, 1-16, 2-6, 3-14, 3-15, 3-25, 3-30, 3-32, 4-29, 4-30, 4-32, 4-33, 4-39, 4-43, 

4-48, 4-50, 4-51, 4-56, 4-57, 4-73, 4-74, 4-76, 4-77, 4-79, 4-80, 4-81, 4-84, 4-85, 4-88, 4-97, 4-107, 

4-109, 4-112, 4-113, 5-9 

Deepwater, x, xii, xiv, 1-7, 1-11, 2-4, 2-5, 2-7, 2-8, 3-7, 3-13, 3-14, 3-16, 3-18, 3-19, 3-20, 3-23, 3-24, 

3-25, 3-26, 3-29, 3-31, 4-4, 4-5, 4-6, 4-7, 4-8, 4-10, 4-13, 4-17, 4-20, 4-21, 4-24, 4-25, 4-28, 4-31, 4-33, 

4-34, 4-37, 4-38, 4-39, 4-40, 4-41, 4-42, 4-43, 4-44, 4-45, 4-46, 4-47, 4-49, 4-51, 4-52, 4-53, 4-54, 

4-55, 4-57, 4-58, 4-59, 4-61, 4-63, 4-64, 4-67, 4-68, 4-71, 4-73, 4-74, 4-75, 4-78, 4-80, 4-93, 4-100, 

4-101, 4-102, 4-104, 4-114, 5-9 
Keywords-4 Central Planning Area Lease Sale 247 Supplemental EIS

Deepwater Horizon, x, xiv, 1-7, 1-11, 2-8, 3-18, 3-19, 3-20, 3-23, 3-24, 3-25, 3-29, 4-4, 4-5, 4-6, 4-7, 4-8, 

4-10, 4-13, 4-17, 4-20, 4-21, 4-24, 4-25, 4-28, 4-31, 4-33, 4-34, 4-37, 4-38, 4-41, 4-42, 4-45, 4-46, 

4-47, 4-49, 4-52, 4-53, 4-54, 4-55, 4-57, 4-58, 4-59, 4-61, 4-63, 4-64, 4-67, 4-68, 4-71, 4-74, 4-75, 

4-78, 4-80, 4-93, 4-100, 4-101, 4-102, 4-104, 5-9 

Demographics, xiv, 2-7, 2-9, 4-8, 4-94, 4-95, 4-96 

Diamondback Terrapins, x, xiii, 4-59, 4-60, 4-61, 4-62 

Discharges, x, xi, xii, xiii, 2-10, 3-10, 3-12, 3-14, 3-17, 3-24, 4-12, 4-13, 4-14, 4-15, 4-29, 4-30, 4-32, 

4-33, 4-35, 4-36, 4-39, 4-40, 4-43, 4-44, 4-49, 4-50, 4-56, 4-62, 4-65, 4-66, 4-69, 4-70, 4-72, 4-73, 

4-74, 4-76, 4-79, 4-103, 4-104, 4-105, 4-110, 4-111 

Dispersants, xi, xv, 3-20, 3-24, 4-9, 4-12, 4-15, 4-18, 4-24, 4-31, 4-34, 4-37, 4-40, 4-41, 4-44, 4-45, 4-46, 

4-51, 4-70, 4-85, 4-86, 4-88, 4-89, 4-99, 4-107, 4-110, 4-111 

Dunes, x, xi, 2-7, 2-8, 4-17, 4-18, 4-19, 4-20, 4-21, 4-37, 4-64, 4-106 

Economic Factors, xiv, 2-7, 2-9, 4-8, 4-80, 4-83, 4-93, 4-95, 4-96, 4-97, 4-98 

Employment, xiv, 4-10, 4-81, 4-83, 4-95, 4-96, 4-97, 4-99, 4-100, 4-101, 4-109 

Endangered Species Act, xiii, 1-6, 2-10, 5-9 

Environmental Justice, x, xv, 1-7, 2-7, 2-9, 4-8, 4-98, 4-99, 4-100, 4-101, 4-102, 5-11 

Essential Fish Habitat, x, xiii, 1-6, 2-7, 2-9, 4-4, 4-32, 4-72, 4-73, 4-74, 4-75, 4-76, 4-78, 4-106, 4-111, 

4-112, 5-9 

Explosive Removals, 4-70 

Fish Resources, x, xiii, 2-7, 2-9, 4-72, 4-73, 4-74, 4-75, 4-76, 4-78, 4-106, 4-111, 4-112 

Fisheries, xiii, xv, 1-12, 1-16, 2-5, 2-8, 4-5, 4-45, 4-47, 4-57, 4-66, 4-71, 4-74, 4-76, 4-77, 4-78, 4-80, 

4-99, 5-3, 5-5, 5-6, 5-7, 5-9 

Flaring, 1-9, 1-16, 4-9 

Flower Garden Banks, ix, 1-12, 2-4, 2-6, 2-7, 2-10, 2-11, 4-29, 4-33, 4-34 

Gulf Sturgeon, 4-69, 4-70, 4-71, 4-72, 4-103, 4-106 

Human Resources, 2-7, 2-9, 4-90, 4-106 

Hurricanes, x, 1-10, 1-12, 3-33, 4-10, 4-12, 4-19, 4-22, 4-23, 4-25, 4-30, 4-33, 4-36, 4-52, 4-54, 4-61, 

4-63, 4-74, 4-80, 4-86, 4-89, 4-104 

Income, xv, 2-12, 4-80, 4-95, 4-96, 4-99, 4-100, 4-101, 4-102, 5-10, 5-11 

Infrastructure, vii, x, xii, xiii, xiv, xv, 1-12, 1-14, 2-6, 3-3, 3-4, 3-11, 3-12, 3-15, 3-16, 3-25, 3-27, 3-28, 

3-31, 3-32, 3-33, 4-8, 4-17, 4-19, 4-22, 4-23, 4-28, 4-32, 4-48, 4-57, 4-69, 4-72, 4-76, 4-79, 4-81, 4-83, 

4-85, 4-88, 4-90, 4-91, 4-92, 4-93, 4-94, 4-95, 4-97, 4-99, 4-100, 4-101, 4-103, 4-109, 4-111, 4-114 

Land Use, x, xiv, 2-7, 2-9, 3-15, 4-8, 4-81, 4-90, 4-91, 4-92, 4-93, 4-94, 4-97, 4-101, 4-106 

Live Bottoms, 1-7, 4-28, 4-29, 4-30, 4-31, 4-33, 4-34, 4-41, 4-43, 4-44, 4-45, 4-46, 4-47, 4-72, 4-73, 

4-106, 4-107, 4-108, 4-112 

Loss of Well Control, vii, xi, 3-24, 3-25, 4-12, 4-15, 4-29, 4-30, 4-32, 4-40, 4-42, 4-44, 4-46, 4-88, 4-107, 

4-110 

Low Relief, 4-28, 4-29, 4-30, 4-31, 4-73, 4-106 

Macondo, 4-6, 4-41, 4-42, 4-45, 4-47, 4-61, 4-105 

Marine Mammals, x, xii, 1-6, 1-16, 2-6, 2-7, 2-9, 4-4, 4-50, 4-51, 4-52, 4-53, 4-54, 4-55, 4-56, 4-58, 

4-106, 4-110, 4-111, 5-6 

Mercury, 4-16 
Keyword Index Keywords-5 

Meteorological Conditions, 3-23, 4-107 

Mitigating Measures, vii, ix, xi, xii, 1-12, 1-13, 1-16, 2-3, 2-4, 2-5, 2-6, 2-9, 2-11, 4-5, 4-6, 4-22, 4-27, 

4-39, 4-40, 4-81, 4-105, 4-107, 4-114, 5-4, 5-9, 5-10 

Mitigation, ix, 1-13, 1-14, 1-16, 2-4, 2-5, 2-6, 4-6, 4-13, 4-22, 4-30, 4-32, 4-33, 4-34, 4-39, 4-40, 4-41, 

4-43, 4-50, 4-56, 4-71, 4-73, 4-74, 4-76, 4-82, 4-94, 4-103, 4-104, 4-105, 4-106, 4-108, 4-111, 4-112, 

4-114, 5-9 

NEPA, viii, ix, 1-4, 1-5, 1-6, 1-12, 1-13, 1-14, 1-16, 2-3, 2-4, 2-5, 2-7, 4-3, 4-4, 4-5, 4-6, 4-7, 4-8, 4-11, 

4-12, 4-14, 4-17, 4-21, 4-22, 4-25, 4-26, 4-28, 4-31, 4-32, 4-34, 4-35, 4-38, 4-39, 4-42, 4-43, 4-47, 

4-49, 4-50, 4-54, 4-55, 4-59, 4-62, 4-63, 4-64, 4-65, 4-68, 4-69, 4-72, 4-75, 4-76, 4-78, 4-79, 4-80, 

4-81, 4-84, 4-86, 4-87, 4-89, 4-90, 4-93, 4-94, 4-96, 4-97, 4-98, 4-99, 4-102, 4-103, 4-105, 5-3, 5-4, 5-5 

Noise, xii, xiii, xiv, 3-6, 3-10, 3-13, 4-50, 4-51, 4-52, 4-56, 4-57, 4-65, 4-66, 4-67, 4-81, 4-100, 4-103, 

4-104, 4-105, 4-111 

Nonchemosynthetic Deepwater Benthic Communities, xii, 2-9, 4-43, 4-44, 4-46, 4-47, 4-72, 4-106 

Offshore Spills, xiii, 3-14, 3-20, 3-21, 3-22, 3-23 

Oil Spills, vii, x, xi, xii, xiii, xiv, xv, 1-7, 1-11, 1-16, 2-8, 2-9, 2-10, 3-14, 3-17, 3-18, 3-19, 3-20, 3-21, 

3-22, 3-23, 3-24, 3-25, 3-33, 4-4, 4-5, 4-6, 4-7, 4-10, 4-12, 4-13, 4-17, 4-18, 4-19, 4-20, 4-22, 4-23, 

4-24, 4-25, 4-26, 4-27, 4-28, 4-29, 4-30, 4-31, 4-32, 4-33, 4-34, 4-37, 4-38, 4-40, 4-42, 4-44, 4-45, 

4-46, 4-47, 4-48, 4-49, 4-50, 4-51, 4-52, 4-53, 4-54, 4-55, 4-56, 4-57, 4-58, 4-59, 4-60, 4-61, 4-62, 

4-63, 4-64, 4-65, 4-66, 4-67, 4-68, 4-70, 4-71, 4-72, 4-74, 4-75, 4-77, 4-78, 4-79, 4-80, 4-82, 4-83, 

4-85, 4-86, 4-88, 4-91, 4-93, 4-95, 4-97, 4-99, 4-100, 4-101, 4-102, 4-103, 4-104, 4-105, 4-107, 4-110, 

4-111, 4-112, 4-113, 4-114, 5-4, 5-9 

OSRA, 1-12, 3-19, 3-20, 3-22 

Physical Oceanography, 1-11, 3-33, 4-87, 4-90 

Pinnacle Trend, 4-28, 4-29, 4-30, 4-31, 4-73, 4-106 

Pipelines, x, xi, xii, xiii, xiv, 1-9, 1-16, 2-5, 2-6, 3-11, 3-13, 3-14, 3-15, 3-18, 3-20, 3-21, 3-23, 3-25, 3-27, 

3-28, 3-29, 3-31, 4-9, 4-12, 4-14, 4-15, 4-16, 4-17, 4-18, 4-19, 4-22, 4-23, 4-26, 4-27, 4-28, 4-29, 4-32, 

4-40, 4-44, 4-48, 4-66, 4-69, 4-70, 4-72, 4-74, 4-76, 4-77, 4-79, 4-84, 4-85, 4-86, 4-88, 4-89, 4-90, 

4-91, 4-103, 4-110, 4-111, 4-112, 4-113, 5-5 

Port Fourchon, xiv, 3-24, 4-25, 4-91, 4-99, 4-100 

Produced Waters, 3-12, 4-28, 4-39, 4-43, 4-65, 4-66, 4-72, 4-76, 4-110 

Public Services, x

Recreational Fishing, x, xiv, 2-7, 2-9, 4-8, 4-51, 4-57, 4-74, 4-77, 4-79, 4-80, 4-81, 4-83, 4-106, 4-111, 

4-114 

Recreational Resources, x, xiv, 2-7, 2-9, 4-8, 4-81, 4-82, 4-83, 4-84, 4-106 

Renewable Energy, 1-4, 1-15, 3-28, 3-31, 4-15, 4-85, 4-86, 4-89, 4-97, 4-101, 4-113 

Resource Estimates, 3-3, 3-4 

Sargassum, x, xii, 2-7, 2-8, 4-35, 4-36, 4-37, 4-38, 4-58, 4-72, 4-106, 4-110 

Sea Turtles, x, xii, 1-16, 2-6, 2-7, 2-9, 4-36, 4-37, 4-55, 4-56, 4-57, 4-58, 4-59, 4-103, 4-106 

Seagrass Communities, x, xi, 2-7, 2-8, 4-22, 4-26, 4-27, 4-28, 4-72, 4-74, 4-106 

Service Base, 3-15, 3-16, 4-23, 4-90, 4-91 

Site Clearance, xiv, 1-16, 2-5 

Soft Bottoms, x, xii, 2-7, 2-8, 3-30, 4-7, 4-32, 4-46, 4-47, 4-48, 4-49, 4-50, 4-72, 4-106 

Spill Response, 1-4, 1-16, 3-17, 3-22, 3-23, 3-24 
Keywords-6 Central Planning Area Lease Sale 247 Supplemental EIS

Spills, viii, xi, xii, xiii, xiv, xv, 1-16, 2-12, 3-14, 3-17, 3-18, 3-19, 3-20, 3-21, 3-22, 3-23, 3-25, 3-26, 3-33 

Stipulation, ix, xii, xiii, 1-6, 1-16, 2-3, 2-4, 2-5, 2-9, 2-10, 2-11, 3-30, 4-5, 4-6, 4-27, 4-28, 4-29, 4-30, 

4-32, 4-33, 4-34, 4-48, 4-52, 4-56, 4-57, 4-60, 4-73, 4-105, 4-106, 4-108, 4-112 

Submerged Vegetation, 4-26, 4-27 

Synthetic-Based Drilling Fluids, 3-26 

Topographic Features, ix, x, xii, 2-4, 2-5, 2-6, 2-7, 2-9, 2-11, 3-11, 4-29, 4-31, 4-32, 4-33, 4-34, 4-72, 

4-73, 4-105, 4-106, 4-107, 4-108 

Tourism, x, 1-11, 4-19, 4-80, 4-81, 4-83, 4-95, 4-97, 4-98, 4-101, 4-112, 4-114, 5-6, 5-10 

Trash, x, 1-11, 3-17, 4-50, 4-56, 4-57, 4-59, 4-60, 4-61, 4-62, 4-63, 4-66, 4-81, 4-103, 4-111 

Waste Disposal, 4-16, 4-23, 4-90, 4-91 

Wastes, xi, 2-6, 3-10, 3-12, 3-13, 3-17, 3-28, 4-15, 4-16, 4-22 

Water Quality, x, xi, xii, 1-11, 2-6, 2-7, 2-8, 3-15, 4-7, 4-11, 4-12, 4-13, 4-14, 4-15, 4-17, 4-36, 4-50, 

4-56, 4-69, 4-70, 4-72, 4-73, 4-74, 4-80, 4-106, 4-110, 4-111, 4-114 

Wetlands, x, xi, 1-7, 2-6, 2-7, 2-8, 3-32, 4-5, 4-7, 4-17, 4-18, 4-20, 4-21, 4-22, 4-23, 4-24, 4-25, 4-26, 

4-27, 4-72, 4-74, 4-77, 4-80, 4-82, 4-83, 4-104, 4-106, 4-110, 4-112, 4-114, 5-4 

The Department of the Interior Mission

As the Nation’s principal conservation agency, the Department of the Interior 

has responsibility for most of our nationally owned public lands and natural 

resources. This includes fostering the sound use of our land and water 

resources; protecting our fish, wildlife, and biological diversity; preserving the 

environmental and cultural values of our national parks and historical places; 

and providing for the enjoyment of life through outdoor recreation. The 

Department assesses our energy and mineral resources and works to ensure 

that their development is in the best interests of all our people by encouraging 

stewardship and citizen participation in their care. The Department also has a 

major responsibility for American Indian reservation communities and for 

people who live in island communities. 

The Bureau of Ocean Energy Management Mission 

The Bureau of Ocean Energy Management (BOEM) promotes energy 

independence, environmental protection, and economic development through 

responsible, science-based management of offshore conventional and 

renewable energy.