U.S. Department of the Interior

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

OCS EIS/EA

BOEM 2017-013

Gulf of Mexico OCS Lease Sale

Draft Supplemental Environmental Impact Statement 2018

U.S. Department of the Interior

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

OCS EIS/EA

BOEM 2017-013

Gulf of Mexico OCS Lease Sale

Draft Supplemental Environmental Impact Statement 2018

Author

Bureau of Ocean Energy Management

Gulf of Mexico OCS Region

Published by

New Orleans

March 2017



v 

COVER SHEET

Draft Supplemental Environmental Impact Statement

for the

Proposed 2018 Gulf of Mexico OCS Lease Sales 

Draft (x) Final ( ) 

Type of Action: Administrative (x) Legislative ( ) 

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

Texas, Louisiana, Mississippi, Alabama, and northwestern 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

Robert Martinson

U.S. Department of the Interior

Bureau of Ocean Energy Management

45600 Woodland Road (VAM-OEP) 

Sterling, VA 20166-9216

703-787-1574

Michelle K. Nannen

504-731-6682

Greg Kozlowski

504-736-2512

ABSTRACT

This Draft Supplemental Environmental Impact Statement (EIS) addresses a proposed Gulf 

of Mexico OCS oil and gas lease sale as scheduled in the 2017-2022 Outer Continental Shelf Oil 

and Gas Leasing: Proposed Final Program (Five-Year Program). This Supplemental EIS is 

expected to be used to inform decisions for each of the two proposed regionwide lease sales 

scheduled for 2018 and to be used and supplemented as necessary for decisions on future Gulf of 

Mexico proposed regionwide lease sales. This Supplemental EIS contains analyses of the potential 

environmental impacts that could result from a proposed regionwide lease sale in the Gulf of Mexico 

as scheduled in the Five-Year Program, but the analyses may be applied and supplemented as 

necessary to inform decisions for each remaining proposed lease sale scheduled in the Five-Year 

Program.

The proposed action (lease sale) is a Federal action requiring an environmental review. This 

Draft Supplemental EIS provides the following information in accordance with the National 

Environmental Policy Act and its implementing regulations, and it will be used in making a decision 

on the proposed action. This document includes the purpose and background of the proposed 

action, identification of the alternatives, description of the affected environment, and an analysis of 
vi

the potential environmental impacts of the 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 proposed action are also analyzed.

Hypothetical scenarios were developed on the levels of activities, accidental events that are 

foreseeable (such as oil spills), and potential impacts that might result if the proposed action is 

adopted. Activities and disturbances associated with the proposed action on biological, physical, 

and socioeconomic resources are considered in the analyses. 

This Draft Supplemental EIS analyzes the potential impacts of the proposed action on air 

and water quality, coastal habitats, deepwater benthic communities, Sargassum, live bottom 

habitats, fishes and invertebrates, birds, protected species, commercial and recreational fisheries, 

recreational resources, archaeological resources, human resources, and land use. It is important to 

note that this Draft 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.

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

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

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

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

http://www.boem.gov/nepaprocess/. 
Executive Summary vii

EXECUTIVE SUMMARY

PURPOSE OF AND NEED FOR THE PROPOSED ACTIONS

This Supplemental Environmental Impact 

Statement (EIS) addresses a proposed Federal 

action – a regionwide lease sale. This Supplemental 

EIS is expected to be used to inform decisions for

proposed Outer Continental Shelf (OCS) oil and gas 

Lease Sales 250 and 251 in the Gulf of Mexico, as 

scheduled in the 2017-2022 Outer Continental Shelf 

Oil and Gas Leasing: Proposed Final Program

(Five-Year Program; USDOI, BOEM, 2016a). This 

Supplemental EIS is expected to be used to inform 

decisions for each of the two lease sales scheduled in 2018 and to be used and supplemented as 

necessary for decisions for each of the remaining proposed regionwide lease sales scheduled in the 

Five-Year Program. This Supplemental EIS contains analyses of the potential environmental 

impacts that could result from a proposed regionwide lease sale in the Gulf of Mexico (GOM) as 

scheduled in the Five-Year Program, but the analyses may be applied and supplemented as 

necessary to inform decisions for each of the remaining proposed lease sales scheduled in the 

Five-Year Program. This Supplemental EIS tiers from and updates the Gulf of Mexico OCS Oil and 

Gas Lease Sales: 2017-2022; Gulf of Mexico Lease Sales 249, 250, 251, 252, 253, 254, 256, 257, 

259, and 261—Final Multisale Environmental Impact Statement (2017-2022 GOM Multisale EIS; 

USDOI, BOEM, 2017a) and provides analyses for the remaining proposed GOM lease sales in that 

document. This Supplemental EIS incorporates by reference all of the relevant material in the 

2017-2022 GOM Multisale EIS. The decision on whether and how to proceed with proposed Lease 

Sale 250 will be made following the completion of this National Environmental Policy Act (NEPA) 

analysis. A separate decision will be made for the second proposed lease sale of 2018, i.e., Lease 

Sale 251. Decisions on the remaining proposed GOM lease sales in the Five-Year Program will be 

made based on additional NEPA review that may update this Supplemental EIS as necessary.

The Bureau of Ocean Energy Management (BOEM) has issued the Five-Year Program 

(USDOI, BOEM, 2016a), which proposes 10 regionwide GOM oil and gas lease sales on the OCS. 

Five regionwide lease sales are tentatively scheduled in August of each year from 2017 through

2021 and five regionwide lease sales are tentatively scheduled in March of each year from 2018 

through 2022. The lease sales proposed in the GOM in the Five-Year Program are regionwide lease 

sales comprised of the Western, Central, and a small portion of the Eastern Planning Areas (WPA, 

CPA, and EPA, respectively) not subject to Congressional moratorium (Figure 1).

The development of the Five-Year Program initiates region-specific NEPA reviews for each 

of the proposed lease sales. Region-specific reviews are conducted by Program Area, and this 

Supplemental EIS contains analyses for the Gulf of Mexico OCS Region. Even though the 

Five-Year Program includes regionwide lease sales in the GOM, any individual lease sale could still 

be scaled back during the prelease sale process, including for example to employ the separate 

2017-2022 Schedule of Proposed 

Gulf of Mexico OCS Region 

Lease Sales

Lease Sale Number Year

249 2017

250 and 251 2018

252 and 253 2019

254 and 256 2020

257 and 259 2021

261 2022
viii 2018 Gulf of Mexico Supplemental EIS

planning area model used in the Proposed Final Outer Continental Shelf Oil & Gas Leasing 

Program: 2012-2017 (2012-2017 Five-Year Program; USDOI, BOEM, 2012), should circumstances 

warrant.

Figure 1. Proposed Regionwide Lease Sale Area Combining the Western, Central, and Eastern 

Planning Areas. 

The Proposed Action

The proposed action evaluated in this Supplemental EIS is to hold a regionwide lease sale in 

the GOM according to the schedule of proposed lease sales set forth by the Five-Year Program. 

This Supplemental EIS has been prepared to inform decisions for the proposed 2018 GOM lease 

sales and analyzes a single proposed action (i.e., a single proposed lease sale in the Gulf of Mexico) 

as scheduled in the Five-Year Program. Since each of the 10 proposed lease sales in the GOM 

region are very similar and occur in close timeframes, BOEM prepared an EIS for a proposed action, 

looking at the 10 proposed lease sales in the Five-Year Program cumulatively (i.e., the 2017-2022 

GOM Multisale EIS). The analysis in the 2017-2022 GOM Multisale EIS will be used to inform each 

of the 10 proposed lease sale decisions. This Supplemental EIS tiers from and updates the 

2017-2022 GOM Multisale EIS and contains analyses of the potential environmental impacts that 

could result from a single proposed lease sale (e.g., Lease Sale 250, but the analyses may be 

applied and supplemented as necessary to inform decisions for each of the remaining proposed 

lease sales scheduled in the Five-Year Program. However, pursuant to the OCSLA’s staged leasing 

process, BOEM must make an individual decision on whether and how to proceed with each 

proposed lease sale. Therefore, in order to make an informed decision on a single proposed lease 

sale, the analyses contained in this Supplemental EIS examine impacts from a single proposed 

lease sale (e.g., Lease Sale 250). The decision on whether and how to proceed with proposed 

Lease Sale 250, which is the first GOM lease sale proposed for 2018, will be made following the 
Executive Summary ix

“It is hereby declared to be the 

policy of the United States that . . . 

the Outer Continental Shelf is a 

vital national resource held by the 

Federal Government for the public, 

which should be made available for 

expeditious and orderly 

development, subject to 

environmental safeguards, in a 

manner which is consistent with 

the maintenance of competition 

and other national needs."

OCSLA, 43 U.S.C. §§ 1331 et seq.

completion of this NEPA analysis. A separate decision will be made for proposed Lease Sale 251, 

which is the second GOM lease sale proposed for 2018. Decisions on the remaining proposed 

GOM lease sales in the Five-Year Program will be made based on additional NEPA reviews that 

may update this Supplemental EIS as necessary.

Purpose of the Proposed Action

The Outer Continental Shelf Lands Act of 1953, as 

amended (43 U.S.C. §§ 1331 et seq. [1988]), hereafter 

referred to as the OCSLA, establishes the Nation’s policy 

for managing the vital energy and mineral resources of the 

OCS. Section 18 of the OCSLA requires the Secretary of 

the Interior to prepare and maintain a schedule of proposed

OCS oil and gas lease sales determined to “best meet 

national energy needs for the 5-year period following its 

approval or reapproval” (43 U.S.C. § 1344). The Five-Year 

Program establishes a schedule that the U.S. Department 

of the Interior (USDOI or DOI) will use as a basis for 

considering where and when leasing might be appropriate 

over a 5-year period.

The purpose of the proposed Federal action addressed in this Supplemental EIS (i.e., a 

proposed regionwide lease sale) is to offer for lease those areas that may contain economically 

recoverable oil and gas resources in accordance with the OCSLA, which specifically states that 

these areas “should be made available for expeditious and orderly development, subject to 

environmental safeguards” (OCSLA, 43 U.S.C. §§ 1331 et seq.). Each individual proposed lease 

sale would provide qualified bidders the opportunity to bid upon and lease available acreage in the 

Gulf of Mexico OCS in order to explore, develop, and produce oil and natural gas. This 

Supplemental EIS will determine the potential environmental impacts that could result from a single 

proposed lease sale (e.g., Lease Sale 250) scheduled in the Five-Year Program, but the analyses 

may be applied and supplemented as necessary for each remaining Federal action (lease sale) 

scheduled in the Five-Year Program. 

Need for the Proposed Action

The need for the proposed action (i.e., a proposed regionwide lease sale) is to manage the 

development of OCS resources in an environmentally and economically responsible manner as 

required under Section 18 of the OCSLA. Oil serves as the feedstock for liquid hydrocarbon 

products, including gasoline, aviation and diesel fuel, and various petrochemicals. Oil from the Gulf 

of Mexico OCS contributes to meeting domestic demand and enhances national economic security. 

Since the U.S. is expected to continue to rely on oil and natural gas to meet its energy needs, each 

proposed action would contribute to meeting domestic demand and reducing the need for importing

these resources.
x 2018 Gulf of Mexico Supplemental EIS

THE DECISION TO BE MADE

This Supplemental EIS has been prepared to inform decisions for each of the proposed 2018 

GOM lease sales. After completion of the NEPA process for this Supplemental EIS, a decision will 

be made for proposed Lease Sale 250, which is scheduled for March 2018 (i.e., prepare a Record of 

Decision for proposed Lease Sale 250). A second NEPA review will be conducted for proposed 

Lease Sale 251, which is scheduled for August 2018, to consider any relevant new information; a 

second Record of Decision will be prepared for proposed Lease Sale 251. As discussed in 

Chapter 1.4.1, individual decisions will be made on each subsequent proposed lease sale in the 

Five-Year Program after completion of the appropriate NEPA review and supplementation of this EIS 

if necessary.

PUBLIC INVOLVEMENT

Pursuant to the OCSLA, the Bureau of Ocean Energy Management published a Call for 

Information (Call) to request and gather information to determine the Area Identification (Area ID) for 

each proposed lease sale in the Draft Proposed Outer Continental Shelf Oil & Gas Leasing Program: 

2017-2022 (2017-2022 Draft Proposed Program), which is the draft nationwide schedule of 

proposed lease sales published for public input. The Call was published in the Federal Register

(2015a) on September 4, 2015, and invited potential bidders to nominate areas of interest within the 

program area(s) included in the 2017-2022 Draft Proposed Program. Using information provided in 

response to the Call and from scoping comments, BOEM then developed an Area ID 

recommendation memorandum. The Area ID is an administrative prelease step that describes the 

geographic area for environmental analysis and consideration for leasing. On November 20, 2015, 

the Area ID decision was made. One Area ID was prepared for all proposed lease sales. The 

Area ID memorandum recommended keeping the entire GOM regionwide area included in the Draft 

Proposed Program for consideration in the 2017-2022 GOM Multisale EIS and supplemental NEPA 

analyses such as this Supplemental EIS. The area identified for lease includes all of the available 

unleased blocks in the GOM not subject to Congressional moratorium pursuant to the Gulf of Mexico 

Energy Security Act of 2006.

BOEM conducted a public scoping process for this Supplemental EIS that extended from 

August 19 to September 19, 2016. Public scoping meetings were held in four cities (Gulfport, 

Mississippi; Mobile, Alabama; Houston, Texas; and New Orleans, Louisiana). In addition to 

accepting oral and written comments at each public meeting, BOEM accepted written comments by 

mail and through the regulations.gov web portal (http://www.regulations.gov). BOEM received a 

total of 433 comments in response to the Notice of Intent to Prepare an EIS and 8 additional 

comments at the scoping meetings, for a total of 441 comments). 

Almost 380 individual comments were received in support of the proposed lease sales, 

356 of which were form letters. Commenters stated that future leases are vital to the national 

economy and security, and are integral to the State of Louisiana and local economies and jobs. 

Several noted that oil and gas companies and employees must be good stewards of the 
Executive Summary xi

environment and continue to provide more emphasis on safety. Several commenters stated that the 

recent downturn in oil and gas prices is hurting small towns and southern states in general.

Twenty-three individual comments were received that opposed future lease sales. 

Commenters stated that renewable energy should be pursued instead of oil and gas, fossil fuels 

should be left in the ground, and new lease sales are not compatible with the U.S. commitment to 

reduce greenhouse gas emissions under the Paris Agreement, which the U.S. joined on April 22, 

2016. Issues of concern included the impacts of oil and gas on greenhouse gas emission and global 

climate change, the impacts of climate change on the GOM’s environmental resources, warmer 

oceans, increased storms and flooding events, and land loss. Several commenters also expressed 

concern about continuing oil and chemical spill risks, continuing effects of past oil and chemical 

spills, leaking wells and pipelines, and a lack of reasonable alternatives. Environmental resources of 

concern included protected species (i.e., marine mammals, sea turtles, beach mice, protected birds, 

and corals), wetlands, fish nurseries, coral reefs, safety of seafood, and environmental justice. 

Comments were received expressing concerns for environmental justice related to those living 

nearby petrochemical processing facilities.

ALTERNATIVES

A proposed action is to hold a lease sale in the GOM according to the schedule of proposed 

lease sales set forth by the Five-Year Program. BOEM has identified four action alternatives, and a 

No Action Alternative, to be analyzed in this Supplemental EIS. These alternatives are briefly 

described below. The mitigating measures (pre- and postlease), including the proposed stipulations, 

are summarized in Chapter 2 of this Supplemental EIS and and are fully described in Chapter 2 and

Appendices B and D of the 2017-2022 GOM Multisale EIS, as are the deferred alternatives not 

analyzed in detail.

Alternative A—Regionwide OCS Lease Sale (The Preferred Alternative)

Alternative A would allow for a proposed regionwide lease sale encompassing all three 

planning areas within the U.S. portion of the Gulf of Mexico OCS. This is BOEM’s preferred 

alternative. This alternative would offer for lease all available unleased blocks within the WPA, CPA, 

and EPA portions of the proposed lease sale area for oil and gas operations (Figure 2), with the 

following exceptions:

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

of 2006 (discussed in the OCS Regulatory Framework white paper [Cameron 

and Matthews, 2016]); 

(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; and

(3) whole and partial blocks within the current boundary of the Flower Garden 

Banks National Marine Sanctuary.
xii 2018 Gulf of Mexico Supplemental EIS

Figure 2. Proposed Regionwide Lease Sale Area, Encompassing the Available Unleased Blocks within 

All Three Planning Areas (approximately 91.93 million acres with approximately 

75.7 million acres available for lease as of February 2017).

Alternative B—Regionwide OCS Lease Sale Excluding Available Unleased Blocks in the WPA

Portion of the Proposed Lease Sale Area

Alternative B would allow for a proposed lease sale encompassing the CPA and EPA within 

the U.S. portion of the Gulf of Mexico OCS (Figure 3). Available blocks within the WPA would not

be considered under this alternative. This alternative would offer for lease all available unleased 

blocks within the CPA and EPA portions of the proposed lease sale area for oil and gas operations, 

with the following exceptions:

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

of 2006 (discussed in the OCS Regulatory Framework white paper [Cameron 

and Matthews, 2016]); 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. 
Executive Summary xiii

Figure 3. Proposed Lease Sale Area for Alternative B, Excluding the Available Unleased Blocks in the 

WPA (approximately 63.35 million acres with approximately 49.8 million acres available for 

lease as of February 2017).

Alternative C—Regionwide OCS Lease Sale Excluding Available Unleased Blocks in the 

CPA/EPA Portions of the Proposed Lease Sale Area

Alternative C would allow for a proposed lease sale encompassing the WPA within the U.S. 

portion of the Gulf of Mexico OCS (Figure 4). Available blocks within the CPA and EPA would not

be considered under this alternative. This alternative would offer for lease all available unleased 

blocks within the WPA portion of the proposed lease sale area for oil and gas operations, with the 

following exception:

(1) whole and partial blocks within the current boundary of the Flower Garden Banks 

National Marine Sanctuary. 
xiv 2018 Gulf of Mexico Supplemental EIS

Figure 4. Proposed Lease Sale Area for Alternative C, Excluding the Available Unleased Blocks in the 

CPA and EPA (approximately 28.58 million acres with approximately 25.9 million acres

available for lease as of February 2017).

Alternative D—Alternative A, B, or C, with the Option to Exclude Available Unleased Blocks 

Subject to the Topographic Features, Live Bottom (Pinnacle Trend), and/or Blocks South of 

Baldwin County, Alabama, Stipulations

Alternative D could be combined with any of the action alternatives above (i.e., Alternative A, 

B, or C) and would allow the flexibility to offer leases under any alternative with additional 

exclusions. Under Alternative D, the decisionmaker could exclude from leasing any available 

unleased blocks subject to any one and/or combination of the following stipulations:

• Topographic Features Stipulation; 

• Live Bottom (Pinnacle Trend) Stipulation; and

• Blocks South of Baldwin County, Alabama, Stipulation (not applicable to 

Alternative C). 

This alternative considered blocks subject to these stipulations because these areas have 

been emphasized in scoping, can be geographically defined, and adequate information exists 

regarding their ecological importance and sensitivity to OCS oil- and gas-related activities, as shown 
Executive Summary xv

in Figure 5. All of the assumptions (including the other potential mitigating measures) and estimates 

would remain the same as described for any given alternative.

Figure 5. Identified Topographic Features, Pinnacle Trend, and Baldwin County Stipulation Blocks in the 

Gulf of Mexico.

Alternative E—No Action

Alternative E is the cancellation of a single proposed GOM lease sale within the Five-Year 

Program. The opportunity for development of the estimated oil and gas that could have resulted 

from a proposed action (i.e., a single proposed lease sale) or alternative to a proposed action, as 

described above, would be precluded or postponed to a future lease sale. Any potential 

environmental impacts resulting from a proposed lease sale would not occur. Activities related to 

previously issued leases and permits (as well as those that may be issued in the future under a 

separate decision) related to the OCS oil and gas program would continue. If a lease sale were to 

be cancelled, the resulting development of oil and gas would most likely be postponed to a future 

lease sale; therefore, the overall level of OCS oil- and gas-related activity would only be reduced by 

a small percentage, if any.
xvi 2018 Gulf of Mexico Supplemental EIS

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. Mitigating measures in 

the form of lease stipulations are added to the lease terms and are therefore enforceable as part of 

the lease. The 10 lease stipulations being considered are 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 (Transboundary Stipulation). The United Nations Convention on the Law of the Sea 

Royalty Payment Stipulation is applicable to a proposed lease sale even though it is not an 

environmental or military stipulation. The Topographic Features and Live Bottom (Pinnacle Trend) 

Stipulations have been applied as programmatic mitigation in the Outer Continental Shelf Oil and 

Gas Leasing Program: 2017-2022; Final Programmatic Environmental Impact Statement (Five-Year 

Program EIS (USDOI, BOEM, 2016b) and therefore, these stipulations would apply to all leases 

issued under the Five-Year Program in the designated lease blocks. Refer to Chapter 2.2.3 for 

BOEM’s mitigating measures. Chapter 2.2.4 and Appendix D of the 2017-2022 GOM Multisale EIS 

provide a more detailed analysis of the 10 lease stipulations and their effectiveness.

Application of lease stipulations will be considered by the decisionmaker. The inclusion of 

the stipulations as part of the analysis of the proposed actions does not ensure that the 

decisionmaker will make a decision to apply the stipulations to leases that may result from a 

proposed 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 warrant. 

However, the Topographic Features and Live Bottom (Pinnacle Trend) Stipulations have been 

applied as programmatic mitigation in the Five-Year Program EIS and therefore, these stipulations 

would apply to all leases issued under the Five-Year Program in the designated lease blocks. Any 

lease stipulations or mitigating measures to be included in a lease sale will be described in the Final 

Notice of Sale. In addition, mitigations may be added to plan and/or permits for OCS oil- and 

gas-related activities (Chapter 2.2.3.3). For more information on mitigating measures that are 

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

2017-2022 GOM Multisale EIS. 

DIRECT AND INDIRECT ACTIONS ASSOCIATED WITH A PROPOSED LEASE SALE

BOEM describes the potentially occurring actions associated with a single proposed lease 

sale and the cumulative activities that provide a framework for a detailed analysis of the potential 

environmental impacts. Exploration and development scenarios describe the infrastructure and 

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

GOM. They also include a set of ranges for resource estimates, projected exploration and 

development activities, and impact-producing factors.
Executive Summary xvii

Offshore activities are described in the context of scenarios for a proposed action 

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

these scenarios to provide a framework for detailed analyses of potential impacts of a proposed 

lease sale. The scenarios are presented as ranges (low to high) of the amounts of undiscovered, 

unleased hydrocarbon resources estimated to be leased and produced as a result of a proposed 

action. The scenarios encompass a range of activities (e.g., the installation of platforms, drilling 

wells, and installing pipelines, and the number of helicopter operations and service-vessel trips, etc.) 

that would be needed to develop and produce the amount of forecasted oil and gas

resources.Environmental Impacts

The affected environment and the potential impacts of a single proposed lease sale under 

each alternative have been described and analyzed by resource. Analysis of the alternatives for 

each resource considers routine activities, accidental events, cumulative impact analysis, incomplete 

or unavailable information, and conclusions for each resource. This Supplemental EIS also 

considers baseline data in the assessment of impacts from a proposed action on the resources and

the environment (Chapter 4). 

The major issues that frame the environmental analyses in this Supplemental EIS 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, wastewater discharges and water 

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

removal, vessel and helicopter traffic, multiple-use conflicts, support services, population 

fluctuations, land-use planning, impacts to recreation and beaches, aesthetic interference, 

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

resources and activities identified during the scoping process that warrant an environmental analysis 

include air quality, water quality, coastal habitats (including wetlands and seagrasses), barrier 

beaches and associated dunes, live bottom habitats (including topographic features and pinnacle 

trends), Sargassum and associated communities, deepwater benthic communities, marine 

mammals, sea turtles, birds, fishes and invertebrate resources, commercial fisheries, recreational 

fishing, recreational resources, archaeological resources, and socioeconomic factors (including 

environmental justice), and within the CPA only, beach mice.

Within each resource summary in Chapter 4 and within the full analysis in the 2017-2022 

GOM Multisale EIS, the cumulative analysis considers environmental and socioeconomic impacts 

that may result from the incremental impact of a proposed action when added to all past, present, 

and reasonably foreseeable future OCS oil- and gas-related activities (OCS Program), as well as 

non-OCS oil- and gas-related activities (e.g., import tankering and commercial fishing). 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, impacts from natural occurrences, such 

as hurricanes, are analyzed.
xviii 2018 Gulf of Mexico Supplemental EIS

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 several years, the Gulf Coast 

States and Gulf of Mexico oil and gas activities have been impacted by major hurricanes. The 

description of the affected environment includes impacts from these relevant issues on the physical 

environment, biological environment, and socioeconomic activities, and on OCS oil- and gas-related 

infrastructure.

Impact Conclusions

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

with a proposed action (lease sale) and a proposed action’s incremental contribution to the 

cumulative impacts are described in the individual resource discussions in Chapter 4. A summary 

of the potential impacts from a proposed action on each environmental and socioeconomic resource 

and the conclusions of the analyses can be found in the following discussions. Table 1 provides a 

comparison of expected impact levels by alternative and is derived from the analysis of each 

resource in Chapter 4. The findings for Alternatives A-E would be a proposed action’s incremental 

contribution to the cumulative impacts from past, present, and future activities in the GOM. These 

activities would include both OCS oil- and gas-related and non-OCS oil- and gas-related activities 

that would be expected regardless of whether or not a lease sale was to occur. The impact-level 

ratings have been specifically tailored and defined for each resource within the Chapter 4 impact 

analysis. Cumulative impacts of current, past, and reasonably foreseeable future activities, 

however, would continue to occur under Alternative E. 

Table 1. Alternative Comparison Matrix.

Impact Level Key1

Beneficial2 Negligible Minor Moderate Major

Alternative

Resource A B C D E 

Air Quality Minor Minor Minor Minor None

Water Quality Negligible Negligible Negligible Negligible None

Coastal Habitats

Estuarine Systems Moderate Moderate Minor Moderate Negligible

Coastal Barrier Beaches 

and Associated Dunes Minor Minor Negligible to Negligible to Negligible Minor Minor

Deepwater Benthic 

Communities Negligible Negligible Negligible Negligible None

Sargassum and 

Associated Communities Negligible Negligible Negligible Negligible None
Executive Summary xix

Impact Level Key1

Beneficial2 Negligible Minor Moderate Major

Alternative

Resource A B C D E

Live Bottoms

Topographic Features Negligible Negligible Negligible Negligible None

Pinnacles and 

Low-Relief Features

Negligible to Negligible to Negligible Negligible None

Minor Minor

Fishes and Invertebrate 

Resources Minor Minor Minor Minor None

Birds Moderate Moderate Moderate Moderate None

Protected Species

Marine Mammals Negligible Negligible Negligible Negligible None

Sea Turtles Negligible Negligible Negligible Negligible None

Beach Mice Negligible Negligible Negligible Negligible None

Protected Birds Negligible Negligible Negligible Negligible None

Protected Corals Negligible Negligible Negligible Negligible None

Commercial Fisheries Beneficial to Beneficial to Beneficial to Beneficial to Negligible Minor Minor Minor Minor

Recreational Fishing Beneficial to Beneficial to Beneficial to Beneficial to Negligible Minor Minor Minor Minor

Recreational Resources Beneficial to Beneficial to Beneficial to Beneficial to Negligible Minor Minor Minor Minor

Archaeological Resources Negligible3 Negligible3 Negligible3 Negligible3 None

Human Resources and 

Land Use

Land Use and Coastal 

Infrastructure

Economic Factors

Minor Minor Minor Minor None

Beneficial to Beneficial to Beneficial to Beneficial to Negligible to

Minor Minor Minor Minor Minor

Social Factors 

(including 

Environmental Justice)

Minor Minor Minor Minor None
xx 2018 Gulf of Mexico Supplemental EIS

Impact Level Key1

Beneficial2 Negligible Minor Moderate Major

Alternative

Resource A B C D E

Note: Some resources have a range for the impact levels to account for certain variables such as the 

uncertainty of non-OCS oil- or gas-related activities, the level and magnitude of potential 

accidental events, and the minimization of the OCS oil- or gas-related impacts through lease 

stipulations, mitigations, and/or regulations. The impact level ratings have been specifically 

tailored and defined for each resource within the Chapter 4 impact analysis.

1 The findings for Alternatives A-D are the incremental contribution of a proposed action added to what 

would be expected to occur under the No Action Alternative (i.e., no lease sale). Therefore, each 

impact determination under Alternatives A-D assumes that the conditions and impacts (i.e., past, 

present, and future activities as a result of past lease sales) under the No Action Alternative would still 

be present.

2 The level of beneficial impacts is specified in the analysis, which could range from low, medium, or 

high.

3 The level of impacts for archaeological resources ranges between negligible to major and is dependent 

upon whether a survey is performed, mitigation is imposed, mitigation is followed, or a site is identified 

prior to the activity.

Air Quality

Air quality is the degree at which the ambient air is free of pollution; it is assessed by 

measuring the pollutants in the air. To protect public health and welfare, the Clean Air Act 

established National Ambient Air Quality Standards (NAAQS) for certain common and widespread 

pollutants. The six common "criteria pollutants" are particle pollution (also known as particulate 

matter, PM2.5 and PM10), carbon monoxide (CO); nitrogen dioxide (NO2); sulfur dioxide (SO2); lead 

(Pb); and ozone (O3). Air emissions from OCS oil and gas development in the Gulf of Mexico would 

arise from emission sources related to drilling and production with associated vessel support, flaring 

and venting, decommissioning, fugitive emissions, and oil spills. Associated activities that take place 

as a result of a proposed action support and maintain the OCS oil and gas platform sources. Air 

emissions from non-OCS oil- and gas-related emissions in the Gulf of Mexico would arise from 

emission sources related to State oil and gas programs, onshore industrial and transportation 

sources, and natural events. Since the primary NAAQS are designed to protect human health, 

BOEM focuses on the impact of these activities on the States, where there are permanent human 

populations.

In the “Air Quality Modeling in the Gulf of Mexico Region” study (Appendices B-D), 

photochemical grid modeling was conducted to assess the impacts to nearby states of existing and 

proposed future OCS oil and gas exploration, development, and production. This draft interim 

assessment is being used to disclose potential cumulative and incremental air quality impacts of the 

proposed lease sales; the final results are expected in fall 2017. The air quality modeling study 

examines the potential impacts of the proposed lease sales with respect to the NAAQS for the 

criteria pollutants O3, NO2, SO2, CO, PM2.5, PM10; the air quality-related values (AQRVs), including 

visibility and acid deposition (sulfur and nitrogen) in nearby Class I and sensitive Class II areas; and 

the incremental impacts of Prevention of Significant Deterioration (PSD) pollutants (NO2, PM10, 

PM2.5) with respect to PSD Class I and Class II increments. (Note: This analysis does not constitute 
Executive Summary xxi

a regulatory PSD increment consumption analysis as would be required for major sources subject to 

the New Source Review program requirements of the Clean Air Act). An assessment of the final 

study results will be discussed in future NEPA documents.

A regionwide lease sale has not previously been analyzed and historic trend data are limited. 

In the scenario in Chapter 3.1 of this Supplemental EIS and Chapter 3.1 of the 2017-2022 GOM 

Multisale EIS, the projected activities of a single regionwide lease sale is based on a range of 

historic observations and provides a reasonable expectation of oil and gas production anticipated 

from a single proposed lease sale. The projected activities of 10 proposed regionwide lease sales’ 

mid-case scenario, which was used in the model, falls within the range of a single proposed lease 

sale. To understand how these results would apply to a single proposed lease sale, the level of 

projected activity was compared between the modeled highest year of the 10 proposed lease sales 

to a single proposed lease sale. This is conservative because the current price of oil equals the low 

range of the scenario. Using these assumptions, the potential impacts of a single proposed lease 

sale would be minor. More specifically, the potential impacts of a single proposed lease sale to the 

Breton Wilderness Area would be moderate, whereas the overall potential impacts of a single 

proposed lease sale would be minor for all other areas. However, since these potential impacts are 

conservative given the current prices of oil and gas, BOEM anticipates future modeling. A full 

analysis of air quality can be found in Chapter 4.1. 

The incremental contribution of a proposed lease sale to the cumulative impacts would most 

likely have a minor effect on coastal nonattainment areas because most impacts on the affected 

resource could be avoided with proper mitigation. Portions of the Gulf Coast onshore areas have 

ozone levels that exceed the Federal air quality standard, but the incremental contribution from a 

proposed lease sale would be very small and would not on their own cause an exceedance.

As previously stated, BOEM contracted an air quality modeling study in the GOM region to 

assess the impacts of OCS oil- and gas-related development to nearby States, as required under the 

OCSLA. The data from forecasted emissions resulting from the 10 proposed lease sales was 

annualized using BOEM’s Resource Evaluation’s mid-case scenario. These results are presented in 

Appendices B-D. The cumulative impacts from all 10 proposed lease sales would be minor to 

moderate. More specifically, the cumulative impacts of 10 proposed lease sales to the Breton 

Wilderness Area and Gulf Islands National Seashore would be moderate, whereas the overall 

cumulative impacts of 10 proposed lease sales would be minor to moderate. 

The cumulative impacts, in addition to the past, present, and future activities, of 10 proposed 

lease sales would most likely have a moderate effect on coastal nonattainment areas for certain 

pollutants. Portions of the Gulf Coast onshore areas have ozone levels that exceed the Federal air 

quality standard, but the cumulative impacts from 10 proposed lease sales do not on their own 

cause an exceedance. A full analysis of air quality can be found in Chapter 4.1. 
xxii 2018 Gulf of Mexico Supplemental EIS

Water Quality

Water quality is a term used to describe the condition or environmental health of a waterbody 

or resource, reflecting its particular biological, chemical, and physical characteristics and the ability 

of the waterbody to maintain the ecosystems it supports and influences. It is an important measure 

for both ecological and human health. The largest impact-producing factors affecting water quality 

are operational discharges and wastes, drilling fluid spills, chemical and waste spills, and oil spills. 

The impacts of OCS Program-related routine operational discharges (Chapter 3.1.5.1 of the 

2017-2022 GOM Multisale EIS and summarized in Table 3-8 of this Suppplemental EIS) on water 

quality are considered negligible (beyond 1,000 meters [m]; 3,281 feet [ft]) to moderate (within 

1,000 m; 3,281 ft) of the source. The potential impacts from OCS Program-related oil spills on water 

quality are considered moderate, even with the implementation of mitigating measures. This is 

because activities to address oil spills may cause secondary impacts to water quality, such as the 

introduction of additional hydrocarbons into the dissolved phase through the use of dispersants and 

the sinking of hydrocarbon residuals from burning. The impacts from a proposed action are a small 

addition to the cumulative impacts on water quality when compared with inputs from hypoxia, 

potentially leaking shipwrecks, chemical weapon dumpsites, natural oil seeps, and natural turbidity. 

The incremental contribution of the routine activities and accidental events associated with a

proposed action to the cumulative impacts on water quality is expected to be negligible for any of 

the action alternatives. For Alternative E, the cancellation of a proposed lease sale would result in 

no new activities associated with a proposed lease sale; therefore, the incremental impacts would be 

none. Cumulative impacts of current and past activities (OCS oil- and gas-related and non-OCS 

oil- and gas-related), however, would continue to occur under this alternative. An analysis of water 

quality can be found in Chapter 4.2. 

Coastal Habitats

Estuarine Systems (Wetlands and Seagrasses/Submerged Vegetation)

The estuarine system is the transition zone between freshwater and marine environments. It 

can consist of many habitats, including wetlands and those containing submerged vegetation. The 

largest impact-producing factors affecting estuarine systems are navigation channel maintenance 

dredging, vessel operation, and oil spills. The impacts to these habitats from routine activities 

associated with a proposed action are expected to be minor to moderate. Minor impacts would be 

due to the projected low probability for any new pipeline landfalls (0-1 projected), the minimal 

contribution to the need for maintenance dredging, and the mitigating measures expected to be used 

to further reduce or avoid these impacts (e.g., the use of modern techniques such as directional 

drilling). However, impacts caused by vessel operations related to a proposed action over 50 years 

would be moderate considering the permanent loss of hundreds of acres of wetlands. Overall, 

impacts to estuarine habitats from oil spills associated with activities related to a proposed action 

would be expected to be minor because of the distance of most postlease activities from the coast, 

the expected weathering of spilled oil over that distance, the projected low probability of large spills 

near the coast, the resiliency of wetland vegetation, and the available cleanup techniques.
Executive Summary xxiii

Cumulative impacts to estuarine habitats are caused by a variety of factors, including the 

OCS oil- and gas-related and non-OCS oil- and gas-related activities outlined in Chapter 4.3 of the 

2017-2022 GOM Multisale EIS and human and natural impacts. Development pressures in the

coastal regions of the GOM have been largely the result of tourism and residential beach-side 

development, and this trend is expected to continue. Storms will continue to impact the coastal 

habitats and have differing impacts. The incremental contribution of a proposed action to the 

cumulative impacts on estuarine habitats is expected to be minor to moderate depending on the 

selected alternative. Under Alternative E, the cancellation of a proposed lease sale would result in 

no new activities associated with a proposed lease sale. There could, however, be some 

incremental increase in impacts caused by a compensatory increase in imported oil and gas to offset 

reduced OCS production, but it would likely be negligible. Cumulative impacts of current and past 

activities (OCS oil- and gas-related and non-OCS oil- and gas-related), however, would continue to 

occur under this alternative. An analysis of estuarine habitats can be found in Chapter 4.3.1. 

Coastal Barrier Beaches and Associated Dunes

The coastal barrier beaches and associated dunes are those beaches and dunes that line 

the coast of the northern GOM, including both barrier islands and beaches on the mainland. The 

largest impact-producing factors affecting estuarine systems are navigation channel maintenance 

dredging and oil spills. The impacts to coastal barrier beaches and dunes from routine activities 

associated with a proposed action are expected to be minor due to the minimal number of projected 

onshore pipelines, the minimal contribution to vessel traffic and to the need for maintenance 

dredging, and the mitigating measures that would be used to further reduce or avoid these impacts. 

The greater threat from an oil spill to coastal beaches is from a coastal spill as a result of a 

nearshore vessel accident or pipeline rupture, and cleanup activities. Overall, impacts to coastal 

barrier beaches and dunes from oil spills associated with OCS oil- and gas-related activities related 

to a proposed action would be expected to be minor because of the distance of most of the resulting 

activities from the coast, expected weathering of spilled oil, projected low probability of large spills 

near the coast, and available cleanup techniques.

Cumulative impacts to coastal barrier beaches and dunes are caused by a variety of factors, 

including the OCS oil- and gas-related and non-OCS oil- and gas-related activities outlined in 

Chapter 4.3.2 of the 2017-2022 GOM Multisale EIS and other human and natural impacts. 

Cumulative OCS oil- and gas-related spills resulting from all past and present leasing activities, 

including the millions of barrels that entered the Gulf of Mexico from the Deepwater Horizon oil spill, 

are estimated to have had a major impact on coastal barrier beaches and dunes. However, the 

incremental increase in impacts from reasonably foreseeable oil spills related to a proposed action is 

expected to be minor. Development pressures in the coastal regions of the GOM have been largely 

the result of tourism and residential beach-side development, and this trend is expected to continue. 

Efforts to stabilize the GOM shoreline through the construction of manmade structures can deprive 

natural restoration of the barrier beaches, i.e., sediment nourishment and sediment transport, which 

has adversely impacted coastal beach landscapes. Storms will continue to impact the coastal 

habitats and have differing impacts. The incremental contribution of a proposed action to the 
xxiv 2018 Gulf of Mexico Supplemental EIS

cumulative impacts on coastal barrier beaches and dunes is expected to be minor. Under 

Alternative E, the cancellation of a proposed lease sale, the resulting additional impacts to coastal 

barrier beaches and dunes would be negligible; however, cumulative impacts from all sources, 

including OCS oil- and gas-related and non-OCS oil- and gas-related sources, would remain. 

Cumulative impacts of current and past activities (OCS oil- and gas-related and non-OCS oil- and 

gas-related), however, would continue to occur under this alternative. An analysis of coastal barrier 

beaches and associated dunes can be found in Chapter 4.3.2. 

Deepwater Benthic Communities

BOEM defines “deepwater benthic communities” as including both chemosynthetic 

communities (chemosynthetic organisms plus seep-associated fauna) and deepwater coral 

communities (deepwater coral plus associated fauna). These communities are typically found in 

water depths of 984 ft (300 m) or deeper throughout the GOM, although deepwater benthic habitats 

are relatively rare compared with ubiquitous soft bottom habitats.

The OCS oil- and gas-related impact-producing factors for deepwater benthic communities 

can be grouped into three main categories: (1) bottom-disturbing activities; (2) drilling-related 

sediment and waste discharges; and (3) noncatastrophic oil spills. These impact-producing factors 

have the potential to damage individual deepwater habitats and disrupt associated benthic 

communities if insufficiently distanced or otherwise mitigated. However, impacts from individual 

routine activities and accidental events are usually temporary, highly localized, and expected to 

impact only small numbers of organisms and substrates at a time. Moreover, use of the expected 

site-specific plan reviews/mitigations will distance activities from deepwater benthic communities, 

greatly diminishing the potential effects. Therefore, at the regional, population-level scope of this 

analysis, and assuming adherence to all expected regulations and mitigations, the incremental 

contribution would be expected to be negligible for any of the action alternatives. Impacts from 

accidental events would be expected to be negligible to minor for any of the action alternatives. 

The expected OCS oil- and gas-related activities from a proposed action would also contribute 

incrementally to the overall OCS oil- and gas-related and non-OCS oil- and gas-related cumulative 

effects experienced by deepwater benthic communities, but only by a negligible amount. Under 

Alternative E, the potential for impacts would be none because new impacts to deepwater benthic 

communities related to a cancelled lease sale would be avoided entirely. The overall OCS oil- and 

gas-related cumulative impacts to deepwater benthic communities are estimated to be negligible to 

minor. Non-OCS oil- and gas-related activities such as commercial fishing (currently negligible) and 

shifting baseline environmental conditions related to climate change (currently negligible but likely to 

increase to major over time should current trends continue or worsen) could cause more noticeable 

impacts on deepwater benthic communities over the next 50 years. Cumulative impacts of current 

and past activities (OCS oil- and gas-related and non-OCS oil- and gas-related), however, would 

continue to occur under this alternative. An analysis of deepwater benthic communities can be 

found in Chapter 4.4. 
Executive Summary xxv

Sargassum and Associated Communities

Sargassum in the GOM is comprised of S. natans and S. fluitans, and is characterized by a 

brushy, highly branched thallus with numerous leaf-like blades and berrylike pneumatocysts. The 

Sargassum cycle is truly expansive, encompassing most of the western Atlantic Ocean and the Gulf 

of Mexico with the growth, death, and decay of these plant and epiphytic communities, which may 

play a substantial role in the global carbon cycle. Several impacting factors can affect Sargassum, 

including vessel-related operations, oil and gas drilling discharges, operational discharges, 

accidental spills, non-OCS oil- and gas-related vessel activity, and coastal water quality. Routine 

vessel operations and accidental events that occur during drilling operations or vessel operations, 

and oiling due to an oil spill were the impact-producing factors that could be reasonably expected to 

impact Sargassum populations in the GOM. All of these impact-producing factors would result in the 

death or injury to the Sargassum plants or to the organisms that live within or around the plant 

matrix. However, the unique and transient characteristics of the life history of Sargassum and the 

globally widespread nature of the plants and animals that use the plant matrix buffer against impacts 

that could occur at any given location. Impacts to the overall population of the Sargassum

community are therefore expected to be negligible from either routine activities or reasonably 

foreseeable accidental events for any of the action alternatives. The incremental contribution of a 

proposed action on the population of Sargassum would be negligible when considered in the 

context of cumulative impacts to the population. Under Alternative E, a proposed lease sale would 

be cancelled and the potential for impacts from routine activities and accidental events would be 

none. Cumulative impacts of current and past activities (OCS oil- and gas-related and non-OCS 

oil- and gas-related), however, would continue to occur under this alternative. Impacts from 

changing water quality would be much more influential on Sargassum than OCS development and 

would still occur without the presence of OCS oil- and gas-related activities. An analysis of 

Sargassum and associated communities can be found in Chapter 4.5. 

Live Bottoms

Topographic Features

Defined topographic features (Chapter 4.6.1) are a subset of GOM live bottom habitats that 

are large enough to have an especially important ecological role, with specific protections defined in 

the proposed Topographic Features Stipulation. Within the Gulf of Mexico, BOEM has identified 

37 topographic features where some degree of protection from oil and gas development may be 

warranted based on geography and ecology. Of all the possible impact-producing factors, it was 

determined that bottom-disturbing activities associated with drilling, exploration, and vessel 

operations were the only impact-producing factors from routine activities that could be reasonably 

expected to substantially impact topographic features. The impact-producing factors resulting from 

accidental events include bottom-disturbing activities from drilling, exploration, and vessel 

operations, as well as the release of sediments and toxins during drilling operations. Oil-spill

response activities were also considered to be a source of potential impacts to topographic features.
xxvi 2018 Gulf of Mexico Supplemental EIS

Adherence to the Topographic Features Stipulation (a required mitigation as a result of the 

Five-Year Program’s Record of Decision) is analyzed in each action alternative and is detailed in 

Appendix D of the 2017-2022 GOM Multisale EIS. Application of the Topographic Features 

Stipulation would assist in preventing or at least minimizing potential impacts to topographic feature 

communities by increasing the distance of OCS oil- and gas-related activities from these features. 

The historical application of this stipulation has resulted in negligible impacts of a proposed action 

to topographic features from routine activities and accidental events. The incremental contribution of 

a proposed action to the overall cumulative impacts is also expected to be negligible with 

adherence to the required Topographic Features Stipulation. Under Alternative E, the potential for 

new incremental impacts to topographic features from a cancelled lease sale would be none

because they would be avoided entirely. Cumulative impacts of current and past activities (OCS

oil- and gas-related and non-OCS oil- and gas-related), however, would continue to occur under this 

alternative. Impacts ranging from negligible to moderate may still be expected from non-OCS 

oil- and gas-related activities such as fishing, pollution, and climate change; however, the 

incremental impact of the proposed activities should not result in a meaningful augmentation of the 

overall expected impacts. An analysis of topographic features can be found in Chapter 4.6.1. 

Pinnacles and Low-Relief Features

The Pinnacle Trend is an approximately 64 x 16 mile (103 x 26 kilometer) high-relief area in 

water depths ranging from approximately 200 to 650 ft (60 to 200 m). It is in the northeastern portion 

of the CPA at the outer edge of the Mississippi-Alabama shelf between the Mississippi River and 

De Soto Canyon (Figures 2-4 and 4-2). Outside of the Pinnacle Trend area, low-relief live bottom 

epibenthic communities occur in isolated locations in shallow waters (<984 ft; 300 m) throughout the 

GOM, wherever there exists suitable hard substrate and other physical conditions (e.g., depth, 

turbidity, etc.), allowing for community development. Hard bottom habitats occur throughout the 

GOM but are relatively rare compared with ubiquitous soft bottoms. The impact-producing factors 

for pinnacles and low-relief live bottom features and associated communities can be grouped into 

three main categories: (1) bottom-disturbing activities; (2) drilling-related sediment and waste 

discharges; and (3) oil spills. These impact-producing factors have the potential to damage 

individual pinnacle and low-relief feature habitats and disrupt associated benthic communities if 

insufficiently distanced or otherwise mitigated. The Live Bottom Stipulation (which is a required 

mitigation as a result of the Five-Year Program’s Record of Decision), along with site-specific 

reviews of permit applications and associated distancing requirements, would mitigate potential 

impacts to the communities as a result of both routine activities and accidental events. At the broad 

geographic and temporal scope of this analysis, and assuming adherence to all expected lease 

stipulations and typically applied regulations and mitigations, routine activities are expected to have 

largely localized and temporary effects. Although accidental events have the potential to cause 

severe damage to specific pinnacle and low-relief feature communities, the number of such events is 

expected to be very small. Therefore, at the regional, population-level scope of this analysis, the 

incremental contribution of impacts from reasonably foreseeable routine activities and accidental 

activities to the overall cumulative impacts is expected to be negligible to minor. Proposed OCS 

oil- and gas-related activities would also contribute incrementally to the overall OCS and non-OCS 
Executive Summary xxvii

oil- and gas-related cumulative impacts experienced by pinnacle and low-relief feature habitats. 

Under Alternative E, the potential for impacts to pinnacle and low-relief feature communities related 

to a cancelled lease sale would be none because new impacts would be avoided entirely. 

Cumulative impacts of current and past activities (OCS oil- and gas-related and non-OCS oil- and 

gas-related), however, would continue to occur under this alternative. The OCS oil- and gas-related 

cumulative impacts to live bottom communities are estimated to be negligible to minor. A full 

analysis of pinnacles and low-relief features can be found in Chapter 4.6.2. 

Fish and Invertebrate Resources

The distribution of fishes and invertebrates varies widely, and species may be associated 

with different habitats at various life stages, which is discussed further in Chapter 4.7 of the 

2017-2022 GOM Multisale EIS. The impact-producing factors affecting these resources are 

anthropogenic sound, bottom-disturbing activities, habitat modification, and accidental oil spills. The 

impacts from routine activities, excluding infrastructure emplacement, would be expected to be 

negligible or minor due to short-term localized effects. The installation of OCS oil- and gas-related 

infrastructure constitutes a long-term modification of the local habitat and is hypothesized to have 

resulted over the life of the program in moderate changes in the distribution of some species. 

Although this effect is not necessarily adverse and infrastructure is expected to be decommissioned 

and sites restored to natural habitat, the cumulative impact over the life of the OCS Program 

extensively pertains to time and space. Accidental spills have been historically low-probability 

events and are typically small in size. The expected impact to fishes and invertebrate resources 

from accidental oil spills is negligible. Commercial and recreational fishing are expected to have 

the greatest direct effect on fishes and invertebrate resources, resulting in impact levels ranging from 

negligible for most species to potentially moderate for some targeted species (e.g., hogfish spp., 

gray triggerfish [Balistes capriscus], and greater amber jack [Seriola dumerili]). The analysis of 

routine activities and accidental events indicates the incremental contribution to the overall 

cumulative impacts on fishes and invertebrate resources as a result of a single proposed lease sale 

would be minor. Under Alternative E, the cancellation of a proposed lease sale, the expected 

impacts on fish and invertebrate resources would be none. Cumulative impacts of current and past 

activities (OCS oil- and gas-related and non-OCS oil- and gas-related), however, would continue to 

occur under this alternative. An analysis of fish and invertebrate resources can be found in

Chapter 4.7. 

Birds

The affected species of birds include both terrestrial songbirds and many groups of 

waterbirds. Routine impacts to coastal, marine, and migratory birds that were considered include 

routine discharges and wastes, noise, platform severance with explosives (barotrauma), geophysical 

surveys with airguns (barotrauma), platform presence and lighting, and pipeline landfalls. The 

impacts to birds from routine OCS oil-and gas-related activities are similar wherever they may occur 

in the GOM, and all are considered negligible to minor. Negligible to minor impacts would not 

affect a substantial number of birds. Any impacts would be acute and reversible. As used here, 

acute means short-term, as it does in the context of short-term toxicity exposure and tests. Further, 
xxviii 2018 Gulf of Mexico Supplemental EIS

no injury to or mortality of a small number of individuals or a small flock would occur. Accidental 

impacts to birds are caused by oil spills, spill cleanup activities, and emergency air emissions. 

Seabirds may not always experience the greatest impacts from a spill, but it may take longer for 

populations to recover because of their unique population ecology (demography). Some species of 

seabirds, such as gulls, have larger clutches (laughing gulls usually have 3 eggs per clutch except in 

the tropics) and may recover quite quickly. However, many species of seabirds can have a clutch 

size of just one egg, and they have relatively long life spans and often have delayed age at first 

breeding. Because of the latter case, impacts on seabirds from overall accidental events would be

expected to be moderate. Impacts from overall accidental events on other waterbirds farther 

inshore would also be expected to be moderate because of the extensive overlap of their 

distributions with oiled inshore areas and shorelines expected from a large oil spill (≥1,000 barrels 

[bbl]). Moderate impacts would affect a substantial abundance of birds.

The incremental contribution of a proposed action to the overall cumulative impacts is 

considered moderate, but only because of the potential impacts that could result from a large oil 

spill (≥1,000 bbl). This conclusion is based on the increment of a proposed action compared with all 

cumulative OCS oil- and gas-related and non-OCS oil- and gas-related impacts. Alternative E would 

offer no new lease blocks for exploration and development; therefore, incremental impacts to birds 

would be none. However, there would be continuing impacts associated with the existing OCS 

oil- and gas-related activities from previously permitted activities and previous lease sales. An 

analysis of birds can be found in Chapter 4.8. 

Protected Species

Marine Mammals

The Gulf of Mexico marine mammal community is diverse and distributed throughout the 

GOM, with the greatest abundances and diversity of species inhabiting oceanic and OCS waters. 

The major potential impact-producing factors affecting marine mammals in the GOM as a result of 

cumulative past, present, and reasonably foreseeable OCS oil- and gas-related activities are 

decommissioning activities, operational discharges, G&G activities, noise, transportation, marine 

debris, and accidental oil spills and spill-response activities. Accidental events involving large spills, 

particularly those continuing to flow fresh hydrocarbons into oceanic and/or outer shelf waters for 

extended periods (i.e., days, weeks, or months), pose an increased likelihood of impacting marine 

mammal populations inhabiting GOM waters. While accidental events cannot be predicted and have 

the potential to impact marine mammal species, the number of such events is expected to be very 

small based on Oil Spill Risk Analysis. 

Proposed OCS oil- and gas-related activities would also contribute incrementally to the 

overall OCS oil- and gas-related and non-OCS oil- and gas-related cumulative effects experienced 

by marine mammal populations. At the regional, population-level scope of this analysis, impacts 

from reasonably foreseeable routine activities and accidental events could be negligible to 

moderate for any of the action alternatives. However, the incremental contribution of a proposed 

action to cumulative impacts to marine mammal populations, depending upon the affected species 
Executive Summary xxix

and their respective population estimate, even when taking into consideration the potential impacts 

of the Deepwater Horizon explosion, oil spill, and response; non-OCS oil- or gas-related activities; 

and the minimization of the OCS oil- or gas-related impacts through lease stipulations and 

regulations, would be expected to be negligible. Under Alternative E, the cancellation of a 

proposed lease sale, the impacts on marine mammals within the Gulf of Mexico would be none. 

However, cumulative impacts from previous lease sales and non-OCS oil- and gas-related activities 

would remain. An analysis of marine mammals can be found in Chapter 4.9.1. 

Sea Turtles

Five ESA-listed sea turtle species are present throughout the northern GOM year-round; 

however, only Kemp’s ridley and loggerhead sea turtles commonly nest on beaches in the GOM 

during the nesting season. Due to the expected implementation of mitigations (e.g., BOEM and 

BSEE proposed compliance with Notices to Lessees and Operators under the proposed Protected 

Species Stipulation and conditions of approval on postlease activities), routine activities (e.g., noise 

or transportation) and accidental events (e.g., oil spills) related to a proposed action are not 

expected to have long-term adverse effects on the population size or productivity of any sea turtle 

species or populations in the northern GOM. Lethal effects could occur from chance collisions with 

OCS oil- and gas-related service vessels or ingestion of accidentally released plastic materials from 

OCS oil- and gas-related vessels and facilities. Most routine activities and accidental events as a 

result of a proposed action are therefore expected to have negligible to moderate impacts. For 

example, a minor impact might be a behavioral change in response to noise while a moderate 

impact might be a spill contacting an individual and causing injury or mortality.

Historically, intense harvesting of eggs, loss of suitable nesting beaches, and fisheriesrelated mortality led to the rapid decline of sea turtle populations. Anthropogenic actions continue to 

pose the greatest threat to sea turtles since their listing under the Endangered Species Act (ESA), 

as well as different natural threats including climate change, disease, and natural disasters. The 

incremental contribution of a proposed action to the cumulative impacts on sea turtles would be 

expected to be negligible. Population-level impacts are not anticipated. Under Alternative E, the 

cancellation of a proposed lease sale, the impacts on sea turtles within the Gulf of Mexico would be 

none. However, cumulative impacts from previous lease sales and non-OCS oil- and gas-related 

activities would remain. An analysis of sea turtles can be found in Chapter 4.9.2. 

Beach Mice

The four subspecies of beach mouse (Peromyscus polionotus ssp.) are small coastal 

rodents that are only found along beaches in parts of Alabama and northwest Florida, and are 

federally listed as endangered. Beach mice rely on dune systems as favorable habitat for foraging 

and maintaining burrows. Due to the distance between beach mouse habitat and OCS oil- and 

gas-related activities, impacts from routine activities are not likely to affect beach mouse habitat 

except under very limited situations. Pipeline emplacement or construction, for example, could 

cause temporary degradation of beach mouse habitat; however, these activities are not expected to 

occur in areas of designated critical habitat. Accidental oil spills and associated spill-response 
xxx 2018 Gulf of Mexico Supplemental EIS

efforts are not likely to impact beach mice or their critical habitat because the species live above the 

intertidal zone where contact is less likely. Habitat loss from non-OCS oil- and gas-related activities 

(e.g., beachfront development) and predation have the greatest impacts to beach mice. Overall, the 

incremental contribution of impacts from reasonably foreseeable routine activities and accidental 

events to the overall cumulative impacts on beach mice is expected to be negligible. Under 

Alternative E, the cancellation of a proposed lease sale, the impacts on beach mice would be none. 

However, cumulative impacts from previous lease sales and other non-OCS oil- and gas-related 

activities would remain. An analysis of beach mice can be found in Chapter 4.9.3. 

Protected Birds

Protected birds are those species or subspecies listed under the ESA by the U.S. Fish and 

Wildlife Service (FWS) as threatened or endangered due to the decrease in their population sizes or 

loss of habitat; therefore, a proposed action could have a greater impact. BOEM is undergoing 

consultation with FWS to minimize the potential impacts to ESA-listed species. Impacts from routine 

activities, which include discharges and wastes affecting air and water quality, noise, and possibly 

artificial lighting, would be negligible to protected birds. The listed bird species considered are 

typically coastal birds and would not be exposed to much of the OCS oil- and gas-related activities. 

Waste discharges to air or water produced as a result of routine activities are regulated by the U.S. 

Environmental Protection Agency and BOEM, and these discharges are subject to limits to reduce

potential impacts; therefore, due to precautionary requirements and monitoring, the impacts to 

protected birds would be negligible. The major impact-producing factors resulting from accidental 

events associated with a proposed action that may affect protected birds include accidental oil spills 

and response efforts. In the case of an accidental oil spill, impacts would be negligible to moderate

depending on the magnitude and time and place of such an event. Major impacts could occur if a 

large oil spill occurred with direct contact to a protected bird species or if the habitat became 

contaminated, resulting in mortality of a listed species. Marine debris produced by OCS oil- and 

gas-related activities as a result of accidental disposal into the water may affect protected birds by 

entanglement or ingestion. Due to the regulations prohibiting the intentional disposal of items, 

impacts would be expected to be negligible; however, impacts may scale up to moderate if the 

accidental release of marine debris caused mortality of a listed bird.

Overall, BOEM would expect negligible to moderate impacts to protected birds considering 

routine activities, accidental events, and cumulative impacts. Due to the precautionary requirements 

and monitoring discussed in Chapter 4.9.4, the incremental impacts to protected birds would be 

negligible for any of the action alternatives (i.e., Alternatives A-D). Under Alternative E, the 

cancellation of a proposed lease sale, the additional incremental impacts to ESA-protected birds or 

their habitats would be none. Cumulative impacts of current and past activities (OCS oil- and 

gas-related and non-OCS oil- and gas-related), however, would continue to occur under this 

alternative. An analysis of protected birds can be found in Chapter 4.9.4. 
Executive Summary xxxi

Protected Corals

Elkhorn, staghorn, boulder star, lobed star, and mountainous star corals are listed by the 

National Marine Fisheries Service (NMFS) as threatened due to the decrease in their population 

sizes; therefore, the relative impacts from a proposed action on a particular group of coral colonies 

could have disproportionately higher population-level effects than what might be experienced by 

other non-listed coral species. BOEM understands this and therefore consults with NMFS to 

minimize any potential impacts to these species. Though the listed species are protected (i.e., given 

ESA status), they could experience the same types of potential impact-producing factors from a 

proposed action as other coral species. Without effective mitigations, routine activities and 

accidental events resulting from a proposed action could directly impact coral habitats within the 

GOM.

The site-specific survey information required for postlease reviews of permit applications 

would allow BOEM to identify and protect live bottom features (which protected corals may inhabit) 

from potential harm by proposed OCS oil- and gas-related activities by requiring that bottomdisturbing activity be distanced from live bottom features. Assuming adherence to the expected 

lease stipulations and other postlease, protective restrictions and mitigations, the routine activities 

related to a proposed action could have short-term localized and temporary effects on protected 

corals, if any. While accidental events have the potential to cause severe damage to specific coral 

communities, the number of such events is expected to be small, and any impacts would be reduced 

or prevented by the lease stipulations and postlease distancing requirements. Furthermore, the 

OCS lease blocks in the EPA that are closest to ESA-defined critical habitat areas for listed corals 

are not being offered in a proposed lease sale due to the current leasing moratorium and are 

therefore too distant to be reasonably affected by routine activities or accidental events. In addition, 

many of the protected corals occur within the Flower Garden Banks National Marine Sanctuary, 

which under the current boundaries is not proposed for future leasing under any of the alternatives in 

this Supplemental EIS or the 2017-2022 Gulf of Mexico Multisale EIS. Therefore, the incremental 

contribution of activities resulting from a proposed action to the overall cumulative impacts on 

protected corals is expected to be negligible. Proposed OCS oil- and gas-related activities would 

contribute incrementally to the overall OCS oil- and gas-related and non-OCS oil- and gas-related 

cumulative impacts experienced by corals. The non-OCS oil- and gas-related cumulative impacts to 

protected corals are expected to be dramatically greater than any impacts related to OCS oil- and 

gas-related activities. Under Alternative E, the cancellation of a proposed lease sale, the impacts on 

protected corals would be none. However, cumulative impacts from previous lease sales and 

non-OCS oil- and gas-related activities would remain. An analysis of protected corals can be found 

in Chapter 4.9.5. 

Commercial Fisheries

A proposed action could affect commercial fisheries by affecting fish populations or by 

affecting the socioeconomic aspects of commercial fishing. The impacts of a proposed action on 

fish populations are presented in Chapter 4.7. Routine activities such as seismic surveys, drilling 

activities, and service-vessel traffic can cause space-use conflicts with fishermen. Structure 
xxxii 2018 Gulf of Mexico Supplemental EIS

emplacement could have positive or negative impacts depending on the location and species. For 

example, structure emplacement prevents trawling in the associated area and, thus, could impact 

the shrimp fishery. On the other hand, production platforms can facilitate fishing for reef fish such as 

red snapper and groupers. The eventual removal of production platforms would reverse these 

positive and negative impacts. Accidental events, such as oil spills, could cause fishing closures 

and have other impacts on the supply and demand for seafood. However, accidental events that 

could arise from a proposed action would likely be small and localized. A proposed action would be 

relatively small when compared with the overall OCS Program, State oil and gas activities, overall 

vessel traffic, tropical storms/hurricanes, economic factors, Federal and State fisheries management 

strategies, and other non-OCS oil- and gas-related factors. Therefore, the incremental contribution

of a proposed action to the cumulative impacts to commercial fisheries would range from beneficial

(low) to minor adverse effects for any of the action alternatives. The exact impacts would depend 

on the locations of activities, the species affected, the intensity of commercial fishing activity in the 

affected area, and the substitutability of any lost fishing access. Alternative E would prevent these 

impacts from occurring, except for potential negligible impacts arising from adjustments to incomes 

in the economy. Under Alternative E, the cancellation of a proposed lease sale, fisheries would still 

be subject to the impacts from the OCS Program, as well as the impacts from non-OCS oil- and 

gas-related activities. An analysis of commercial fisheries can be found in Chapter 4.10. 

Recreational Fishing

The Gulf of Mexico’s extensive estuarine habitats (Chapter 4.3.1), live bottom habitats 

(Chapter 4.6), and artificial substrates (including artificial reefs, shipwrecks, and oil and gas 

platforms) support several valuable recreational fisheries. Alternatives A-D can affect recreational 

fishing by affecting fish populations or by affecting the socioeconomic aspects of recreational fishing. 

The impacts of Alternatives A-D on fish populations are presented in Chapter 4.7. Vessel traffic can 

cause space-use conflicts with anglers. Structure emplacement generally enhances recreational 

fishing, although this positive effect will be offset during decommissioning unless a structure were 

maintained as an artificial reef. Accidental events, such as oil spills, can cause fishing closures and 

can affect the aesthetics of fishing in an area. However, accidental events that could arise would 

likely be small and localized. Alternatives A-D should also be viewed in light of overall trends in 

OCS platform decommissioning, State oil and gas activities, overall vessel traffic, tropical 

storms/hurricanes, economic factors, and Federal and State fisheries management strategies. The 

incremental impacts of Alternatives A-D on recreational fisheries are expected to be beneficial (low)

to minor. Alternative E, the cancellation of a proposed lease sale, would cause some economic 

adjustments (refer to Chapter 4.14.2), which could cause negligible impacts to recreational fishing 

activities. Cumulative impacts of current and past activities (OCS oil- and gas-related and non-OCS 

oil- and gas-related), however, would continue to occur under this alternative. An analysis of 

recreational fishing can be found in Chapter 4.11. 

Recreational Resources

Alternatives A-D would contribute to the negligible to minor space-use conflicts (from vessel 

traffic) and visual impacts (from the visibility of OCS structures) that arise due to the broader OCS 
Executive Summary xxxiii

Program. Structure emplacements can have beneficial (low) impacts on recreational fishing and 

diving because platforms often act as artificial reefs, but the eventual removal of these structures 

would lead to negligible to minor negative impacts. Oil spills can have a negligible to minor

negative affect on beaches and other coastal recreational resources. Alternatives A-D should also 

be viewed in light of of the overall OCS Program, as well as various non-OCS oil- and gas-related 

factors, such as beach/wetlands erosion, beach disruptions, economic factors, and activities, that 

can cause space-use conflicts and aesthetic impacts such as commercial and military activities. 

Because of the relatively small contribution of any given lease sale under any of the proposed action 

alternatives (i.e., Alternatives A-D) to the overall OCS Program, in addition to other non-OCS oil- and 

gas-related activities, the incremental impacts are expected to be beneficial (low) to minor adverse 

effects. Under Alternative E, the cancellation of a proposed lease sale, there could be negligible

impacts to recreational resources due to the small economic adjustments. Cumulative impacts of 

current and past activities (OCS oil- and gas-related and non-OCS oil- and gas-related), however, 

would continue to occur under this alternative. An analysis of recreational resources can be found in 

Chapter 4.12. 

Archaeological Resources

Archaeological resources are any material remains of human life or activities that are at least 

50 years of age and that are capable of providing scientific or humanistic understanding of past 

human behavior, cultural adaptation, and related topics through the application of scientific or

scholarly techniques, such as controlled observation, contextual measurement, controlled collection, 

analysis, interpretation, and explanation (30 CFR § 250.105). Archaeological resources are 

primarily impacted by any activity that directly disturbs or has the potential to disturb the seafloor. 

For the OCS Program, this includes the placement of drilling rigs and production systems on the 

seafloor; pile driving associated with platform emplacement; pipeline placement and installation; the 

use of seismic receiver nodes and cables; the dredging of new channels, as well as maintenance 

dredging of existing channels; anchoring activities; post-decommissioning activities, including 

trawling clearance; and the masking of archaeological resources from industry-related infrastructure 

and debris.

Regardless of which planning area a proposed lease sale is held, the greatest potential 

impact to an archaeological resource as a result of a proposed action under any of the action 

alternatives is site-specific and would result from direct contact between an offshore activity or 

accidental event and a site. A proposed action’s postlease activities, including the drilling of wells 

and installation of platforms, installation of pipelines, anchoring, the removal of platforms and other 

structures installed on the seafloor, and site clearance activities, as well as accidental events such 

as loss of debris, may result in negligible to major impacts to archaeological sites.

Major impacts could potentially occur if the mitigations described in Chapter 4.13 were not 

applied to postlease activities. With the identification, evaluation, and avoidance or mitigation of 

archeological resources, the incremental contribution of a proposed action is expected to result in 

negligible, long-term cumulative impacts to archaeological resources; however, if an archaeological 
xxxiv 2018 Gulf of Mexico Supplemental EIS

site were to be impacted, impacts may range from negligible to major. Under Alternative E, the 

cancellation of a proposed lease sale, the impact-producing factors discussed in Chapter 4.13

would not take place for that proposed lease sale; therefore, the impacts would be none. 

Cumulative impacts of current and past activities (OCS oil- and gas-related and non-OCS oil- and 

gas-related), however, would continue to occur under this alternative. An analysis of archaeological 

resources can be found in Chapter 4.13. 

Human Resources and Land Use (Including Environmental Justice)

Land Use and Coastal Infrastructure

Oil and gas exploration, production, and development activities on the OCS are supported by 

an expansive onshore network of coastal infrastructure that includes hundreds of large and small 

companies. Because OCS oil- and gas-related activities are supported by this long-lived, expansive 

onshore network, routine operations associated with a proposed action are not expected to produce 

any major impacts to land use and coastal infrastructure. Potential impacts from routine operations 

could range from negligible to moderate, depending on the location, scale, and type of activity. 

The impacts of reasonably foreseeable accidental events such as oil spills, chemical and drilling fluid 

spills, and vessel collisions are not likely to last long enough to adversely affect overall land use or 

coastal infrastructure in the analysis area and would therefore be negligible to moderate. The 

cumulative analysis includes impacts that could result from a proposed lease sale combined with 

baseline conditions, all past, present, and future OCS oil- and gas-related lease sales and activities, 

as well as all past, present, and reasonably foreseeable future actions that are external to OCS 

oil- and gas-related activities. Activities relating to all past, present, and future OCS oil- and 

gas-related activities are expected to minimally affect the current land use of the analysis area 

because most subareas have strong industrial bases and designated industrial parks. Non-OCS 

oil- and gas-related activities contribute substantially to the cumulative impacts on land use and 

coastal infrastructure, while only a minor incremental contribution is expected for a proposed action. 

For any of the action alternatives, the cumulative impacts on land use and coastal 

infrastructure could range from beneficial to moderate for OCS oil- and gas-related activities and 

beneficial to major for non-OCS oil- and gas-related activities depending on the specifics of each 

situation, whether the impacts are measurable, how long the impacts would last, and the size of the 

affected geographic area as defined in Chapter 4.14.1. Alternative E would result in no lease sale 

and, thus, the direct impacts as a result of a proposed lease sale would be none, and there would 

be no incremental contribution of impacts to land use and coastal infrastructure beyond a temporary 

negative economic impact for the oil and gas industry and coastal states (such as Louisiana), which

are more dependent on oil and gas revenues. Cumulative impacts of current and past activities 

(OCS oil- and gas-related and non-OCS oil- and gas-related), however, would continue to occur 

under this alternative. An analysis of land use and coastal infrastructure can be found in 

Chapter 4.14.1. 
Executive Summary xxxv

Economic Factors

A proposed lease sale would lead to beneficial (low) impacts arising from industry 

expenditures, government revenues, corporate profits, and other market impacts. Some of these 

impacts would be concentrated along the Gulf Coast, while others would be widely distributed. A 

proposed lease sale could also lead to negative economic impacts (negligible to minor) arising 

from accidental events and disruptions to other industries. There would be some differences in 

economic impacts among the alternatives, corresponding to the differences in the scales and 

distributions of likely activities. Chapter 4.14.2 of the 2017-2022 GOM Multisale EIS presents 

detailed estimates of the economic impacts of the alternatives. The alternatives should be viewed in 

light of the OCS Program, as well the numerous forces that can affect energy markets and the 

overall economy. Most of the incremental economic impacts of a proposed action are forecast to be 

beneficial, although there would be some minor adverse impacts . Alternative E, the cancellation 

of a proposed lease sale, would negatively impact firms and employees that depend on recurring 

leases; therefore, the impacts of Alternative E would be negligible to minor, with some partially 

offsetting beneficial impacts. Cumulative impacts of current and past activities (OCS oil- and 

gas-related and non-OCS oil- and gas-related), however, would continue to occur under this 

alternative. An analysis of economic factors can be found in Chapter 4.14.2. 

Social Factors (Including Environmental Justice)

Potential social impacts resulting from a proposed action would occur within the larger 

socioeconomic context of the GOM region. The affected environment of the analysis area is quite 

large geographically and in terms of population (133 counties and parishes with over 22.7 million 

residents). The impacts from routine activities related to a proposed action are expected to be 

negligible to moderate, widely distributed, and to have little impact because of the existing 

extensive and widespread support system for the petroleum industry and its associated labor force. 

Outside of a low-probability catastrophic oil spill, which is not reasonably foreseeable and not part of 

a proposed action, any potential accidental events are not likely to be of sufficient scale or duration 

to have adverse and disproportionate long-term impacts for people and communities in the analysis 

area and would therefore range from negligible to moderate. In the cumulative analysis, impacts 

from OCS oil- and gas-related activities would range from beneficial to moderate. Non-OCS 

oil- and gas-related factors, which include all human activities, natural events, and processes, 

actually contribute more to cumulative impacts than do factors related to OCS oil- and gas-related 

activities alone because of the analysis area’s complex socioeconomic framework and result in 

beneficial to major impacts. The incremental contribution of a proposed action to cumulative 

impacts would be minor. Alternative E would result in no lease sale and, thus, the overall 

incremental impacts as a result of Alternative E would be none. Cumulative impacts of current and 

past activities (OCS oil- and gas-related and non-OCS oil- and gas-related), however, would 

continue to occur under this alternative.

Coastal populations experience cumulative impacts that include all human activities and 

natural processes and events. The cumulative analysis includes impacts that could result from a 

proposed lease sale combined with baseline conditions, all past, present, and future OCS oil- and 
xxxvi 2018 Gulf of Mexico Supplemental EIS

gas-related lease sales and activities, as well as all past, present, and reasonably foreseeable future 

actions that are external to OCS oil- and gas-related activities. Within this divided analytical 

framework of OCS oil-and gas-related and non-OCS oil- and gas-related impacts, the largest 

quantity of impact-producing factors for coastal populations occur as non-OCS oil- and gas-related 

impacts because OCS oil- and gas-related activities form a very small part of the greater, complex 

socioeconomic structure in the GOM. The incremental contribution of a proposed action to 

cumulative impacts of a single proposed lease sale would be minor for communities and people in 

the Gulf Coast region.

Environmental Justice Determination: The oil and gas industry in the GOM region is 

expansive and long-lived over several decades with substantial infrastructure in place to support 

both onshore and offshore activities. BOEM’s scenario estimates call for 0-1 new gas processing 

plant and 0-1 new pipeline landfall over the 50-year life of a single proposed action. Impacts to 

GOM populations from a proposed action would be immeasurable for environmental justice since 

these low-income and minority communities are located onshore, distant from Federal OCS oil- and 

gas-related activities. Also, since these vulnerable populations are located within the larger context 

of onshore and State-regulated nearshore oil and gas activities that are connected to downstream 

infrastructure over which BOEM has no regulatory authority, BOEM has determined that a proposed 

action would not produce environmental justice impacts in the GOM region. An analysis of social 

factors and an environmental justice determination can be found in Chapter 4.14.3. 

APPENDICES

To improve the readability of this Supplemental EIS, more detailed supporting information 

has been placed in the appendices, which include a Memorandum of Agreement between BOEM 

and the National Park Service, meteorological information used for the air quality modeling, 

description of emissions generation, and photochemical modeling.

Appendix A is the Memorandum of Agreement between BOEM and the National Park 

Service; it outlines the roles and responsibilities for both agencies during the preparation of this 

Supplemental EIS.

Appendix B details the meteorological information used for the air quality modeling 

described in Chapter 4.1. Parameters such as wind speed, wind direction, air temperature, and 

humidity are required by models to determine the rate that pollutants disperse and react in the 

atmosphere. This appendix details the modeling performance evaluation of a Weather and 

Research Forecast model for 2012 used in conducting the air quality modeling summarized in 

Chapter 4.1. 

Appendix C describes how the emissions were generated for the Cumulative and Visibility 

Impact Analysis Emissions Inventory used in conducting the air quality modeling summarized in 

Chapter 4.1. 
Executive Summary xxxvii

Appendix D provides the photochemical modeling, evaluation of the modeling, and results of 

the air quality modeling summarized in Chapter 4.1. 

Table of Contents xxxix 

TABLE OF CONTENTS 

Page 

EXECUTIVE SUMMARY .................................................................................................................... vii

LIST OF FIGURES ............................................................................................................................ xlv

LIST OF TABLES ............................................................................................................................... liii

ABBREVIATIONS AND ACRONYMS ............................................................................................... lvii

CONVERSION CHART ...................................................................................................................... lxi

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

1.0 Introduction .......................................................................................................................... 1-3

1.1 Purpose of the Proposed Action .......................................................................................... 1-6

1.2 Need for the Proposed Action .............................................................................................. 1-7

1.3 OCS Oil and Gas Program Planning and Decision Process ................................................ 1-7

1.3.1 Prelease Process ..................................................................................................... 1-8 

1.3.2 Gulf of Mexico Postlease Activities ........................................................................ 1-10 

1.4 The Decision To Be Made ................................................................................................. 1-11 

1.5 Regulatory Framework ....................................................................................................... 1-12

1.6 Other OCS Oil- and Gas-Related Activities ....................................................................... 1-12

1.7 Other Pertinent Environmental Reviews or Documentation ............................................... 1-12

1.8 Format and Organization of this Supplemental EIS ........................................................... 1-13

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

2.0 Introduction .......................................................................................................................... 2-3

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

2.2 Alternatives, Mitigating Measures, and Issues ..................................................................... 2-4

2.2.1 What are the Alternatives that BOEM is Considering for Each Proposed 

Lease Sale? ............................................................................................................. 2-5

2.2.1.1 Alternative A—Regionwide OCS Lease Sale (The Preferred 

Alternative) ............................................................................................... 2-5 

2.2.1.2 Alternative B—Regionwide OCS Lease Sale Excluding Available 

Unleased Blocks in the WPA Portion of the Proposed Lease Sale 

Area .......................................................................................................... 2-7 

2.2.1.3 Alternative C—Regionwide OCS Lease Sale Excluding Available 

Unleased Blocks in the CPA/EPA Portions of the Proposed Lease 

Sale Area .................................................................................................. 2-8 

2.2.1.4 Alternative D—Alternative A, B, or C, with the Option to Exclude 

Available Unleased Blocks Subject to the Topographic Features, 

Live Bottom (Pinnacle Trend), and/or Blocks South of Baldwin County, 

Alabama, Stipulations ............................................................................... 2-9

2.2.1.5 Alternative E—No Action ........................................................................ 2-11
xl 2018 Gulf of Mexico Supplemental EIS

2.2.2 What Other Alternatives and Deferrals Has BOEM Considered But Not 

Analyzed in Detail? .................................................................................................. 2-12

2.2.3 What Types of Mitigating Measures Does BOEM Apply?....................................... 2-13

2.2.3.1 Proposed Lease Mitigating Measures (Stipulations) ............................... 2-14

2.2.3.2 Prelease Mitigating Measures (Stipulations) by Alternative .................... 2-15

2.2.3.3 Postlease Mitigating Measures ................................................................ 2-16

2.2.4 What are the Primary Topics and Resources Being Evaluated? ............................ 2-17

2.2.4.1 Issues to be Analyzed .............................................................................. 2-18

2.2.4.2 Issues Considered but Not Analyzed....................................................... 2-18

2.3 Comparison of Impacts by Alternative ................................................................................. 2-19

2.4 Summary of Impacts............................................................................................................. 2-21

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

3.0 Introduction............................................................................................................................. 3-3

3.1 Routine Activities .................................................................................................................... 3-4

3.1.1 What Activities Routinely Occur as a Result of a Single Lease Sale?...................... 3-4

3.1.1.1 Exploration and Delineation ....................................................................... 3-5 

3.1.1.2 Development .............................................................................................. 3-6 

3.1.1.3 Production .................................................................................................. 3-7 

3.1.1.4 Decommissioning and Removal Operations.............................................. 3-8

3.1.2 How Much and Where is Activity Expected to Occur as a Result of a Proposed 

Action? ..................................................................................................................... 3-10

3.1.2.1 Exploration Scenario ................................................................................ 3-14

3.1.2.2 Development Scenario............................................................................. 3-17

3.1.2.3 Production Scenario................................................................................. 3-19

3.1.2.4 Decommissioning Scenario...................................................................... 3-22 

3.1.2.5 Transportation Scenario........................................................................... 3-23

3.1.3 Summary of Routine Impact Producing Factors...................................................... 3-24

3.2 Accidental Events ................................................................................................................. 3-31

3.2.1 What Events Might Accidentally Occur as a Result of Operations Following 

a Lease Sale? .......................................................................................................... 3-31

3.2.1.1 Releases into the Environment ................................................................ 3-31 

3.2.1.2 Collisions .................................................................................................. 3-32 

3.2.1.3 Spill Response.......................................................................................... 3-32

3.2.2 How Many Oil Spills Could Occur as a Result of a Proposed Lease Sale?............ 3-32 

3.2.3 What is the Response to Accidental Events?.......................................................... 3-39

3.2.4 Summary of Accidental Impact-Producing Factors ................................................. 3-40

3.3 Cumulative Impacts.............................................................................................................. 3-43

3.3.1 What Activities, Not Considered a Part of a Proposed Action, has BOEM 

Considered?............................................................................................................. 3-43 

3.3.2 Summary of Cumulative Activities ........................................................................... 3-43

3.3.2.1 Cumulative OCS Oil and Gas Program Scenario.................................... 3-43 

3.3.2.2 Non-OCS Oil- and Gas-Related Impact-Producing Factors .................... 3-46
Table of Contents xli

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

4.0 Overview................................................................................................................................. 4-3

4.0.1 What Encompasses the Affected Environment for a Gulf of Mexico Lease Sale? ... 4-6 

4.0.2 How are the Potential Environmental Consequences Determined? ......................... 4-7

4.0.2.1 Routine Activities........................................................................................ 4-9 

4.0.2.2 Accidental Events..................................................................................... 4-10

4.0.2.3 Cumulative Impacts.................................................................................. 4-10

4.0.2.4 Incomplete or Unavailable Information .................................................... 4-11

4.0.2.5 Alternatives............................................................................................... 4-12

4.0.2.6 Summary .................................................................................................. 4-13

4.1 Air Quality ............................................................................................................................. 4-14

4.1.1 Description of the Affected Environment ................................................................. 4-17

4.1.2 Environmental Consequences................................................................................. 4-25

4.1.2.1 Routine Activities...................................................................................... 4-28

4.1.2.2 Accidental Events..................................................................................... 4-31

4.1.2.3 Cumulative Impacts.................................................................................. 4-34

4.1.2.3.1 Impacts Assessment............................................................... 4-39

4.1.2.4 Incomplete or Unavailable Information .................................................... 4-52

4.1.2.5 Alternative A—Regionwide OCS Lease Sale (The Preferred 

Alternative) ............................................................................................... 4-53

4.1.2.6 Alternative B—Regionwide OCS Proposed Lease Sale Excluding 

Available Unleased Blocks in the WPA Portion of the Proposed 

Lease Sale Area....................................................................................... 4-54

4.1.2.7 Alternative C—Regionwide OCS Proposed Lease Sale Excluding 

Available Unleased Blocks in the CPA/EPA Portions of the Proposed 

Lease Sale Area....................................................................................... 4-54

4.1.2.8 Alternative D—Alternative A, B, or C, with the Option to Exclude 

Available Unleased Blocks Subject to the Topographic Features, 

Live Bottom (Pinnacle Trend), and/or Blocks South of Baldwin County, 

Alabama, Stipulations............................................................................... 4-54

4.1.2.9 Alternative E—No Action.......................................................................... 4-54

4.2 Water Quality........................................................................................................................ 4-55

4.3 Coastal Habitats ................................................................................................................... 4-60

4.3.1 Estuarine Systems (Wetlands and Seagrass/Submerged Vegetation)................... 4-60

4.3.2 Coastal Barrier Beaches and Associated Dunes..................................................... 4-65

4.4 Deepwater Benthic Communities......................................................................................... 4-70

4.5 Sargassum and Associated Communities ........................................................................... 4-77

4.6 Live Bottom Habitats ............................................................................................................ 4-83

4.6.1 Topographic Features and Associated Communities.............................................. 4-84

4.6.2 Pinnacles and Low-Relief Features and Associated Communities......................... 4-92

4.7 Fishes and Invertebrate Resources ...................................................................................4-100

4.8 Birds....................................................................................................................................4-106
xlii 2018 Gulf of Mexico Supplemental EIS

4.9 Protected Species ..............................................................................................................4-111

4.9.1 Marine Mammals....................................................................................................4-118

4.9.2 Sea Turtles.............................................................................................................4-126

4.9.3 Beach Mice (Alabama, Choctawhatchee, Perdido Key, and St. Andrew).............4-130

4.9.4 Protected Birds.......................................................................................................4-132

4.9.5 Protected Corals ....................................................................................................4-136

4.10 Commercial Fisheries.........................................................................................................4-139

4.11 Recreational Fishing...........................................................................................................4-143

4.12 Recreational Resources .....................................................................................................4-146

4.13 Archaeological Resources..................................................................................................4-149

4.14 Human Resources and Land Use ......................................................................................4-156

4.14.1 Land Use and Coastal Infrastructure.....................................................................4-156

4.14.2 Economic Factors ..................................................................................................4-162

4.14.3 Social Factors (Including Environmental Justice)..................................................4-165

4.14.3.1 Environmental Justice Determination.....................................................4-170

4.15 Unavoidable Adverse Impacts of a Proposed Action.........................................................4-171

4.16 Irreversible and Irretrievable Commitment of Resources ..................................................4-175

4.16.1 Coastal Habitats.....................................................................................................4-175

4.16.2 Biological Resources .............................................................................................4-175

4.16.2.1 Threatened and Endangered Species ...................................................4-176

4.16.2.2 Fish and Invertebrate Resources, Deepwater Benthic Communities, 

Commercial Fisheries, and Recreational Fishing ..................................4-176

4.16.3 Archaeological Resources .....................................................................................4-176

4.16.4 Oil and Gas Development......................................................................................4-176

4.16.5 Loss of Human and Animal Life.............................................................................4-176

4.17 Relationship Between the Short-Term Use of Man’s Environment and the 

Maintenance and Enhancement of Long-Term Productivity..............................................4-177

4.17.1 Short-Term Use......................................................................................................4-177

4.17.2 Relationship to Long-Term Productivity.................................................................4-178

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

5.0 Introduction............................................................................................................................. 5-3

5.1 Coastal Zone Management Act.............................................................................................. 5-3

5.2 Endangered Species Act........................................................................................................ 5-4

5.3 Magnuson-Stevens Fishery Conservation and Management Act ......................................... 5-5

5.4 National Historic Preservation Act.......................................................................................... 5-5

5.5 Government-to-Government Tribal Consultation................................................................... 5-7

5.6 National Environmental Policy Act ......................................................................................... 5-8

5.6.1 Development of the Proposed Action ........................................................................ 5-8

5.6.1.1 Call for Information and Area ID Memorandum ......................................... 5-8 

5.6.1.2 Notice of Intent to Prepare a Supplemental EIS........................................ 5-9
Table of Contents xliii

5.6.2 Development of the Draft Supplemental EIS............................................................ 5-9

5.6.2.1 Scoping....................................................................................................... 5-9 

5.6.2.2 Summary of Scoping Comments ............................................................. 5-10

5.6.2.3 Additional Public Input Opportunities ....................................................... 5-16

5.6.2.4 Cooperating Agencies.............................................................................. 5-16

5.6.2.5 Distribution of the Draft Supplemental EIS for Review and Comment .... 5-17

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

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

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

APPENDICES

Appendix A Cooperating Agency Memorandum of Agreement ................................................. A-3

Appendix B Air Quality: WRF Model Performance.................................................................... B-1

Appendix C Air Quality: Emissions for the Cumulative and Visibility Impacts........................... C-1

Appendix D Air Quality: Cumulative and Visibility Impacts........................................................ D-1

KEYWORD INDEX................................................................................................................Keywords-3

List of Figures xlv

LIST OF FIGURES

Page

Figure 1-1. Proposed Regionwide Lease Sale Area Combining the Western, Central, and 

Eastern Planning Areas. ............................................................................................... 1-5 

Figure 1-2. OCS Oil and Gas Program Development Process....................................................... 1-7 

Figure 1-3. BOEM's Planned Supplemental Approach Showing the Tiering Relationships 

for Proposed Gulf of Mexico Lease Sales. ................................................................... 1-9 

Figure 2-1. Proposed Regionwide Lease Sale Area, Encompassing the Available Unleased 

Blocks within All Three Planning Areas. ....................................................................... 2-6 

Figure 2-2. Proposed Lease Sale Area for Alternative B, Excluding the Available Unleased 

Blocks in the WPA......................................................................................................... 2-7 

Figure 2-3. Proposed Lease Sale Area for Alternative C, Excluding the Available Unleased 

Blocks in the CPA and EPA.......................................................................................... 2-9 

Figure 2-4. Identified Topographic Features, Pinnacle Trend, and Blocks South of Baldwin 

County, Alabama, Stipulation Blocks in the Gulf of Mexico........................................ 2-10

Figure 3-1. Phases of OCS Activity Resulting from a Single Proposed Lease Sale over 

50 Years........................................................................................................................ 3-5 

Figure 3-2. Offshore Subareas in the Gulf of Mexico.................................................................... 3-12

Figure 3-3. (A) Number of Exploration and Delineation Wells Drilled over the Course of a 

Proposed Action under Alternative A for 50 Years. (B, C) Location of Exploration 

Wells Drilled during the Entire 50-Year Period. .......................................................... 3-16

Figure 3-4. (A) Number of Production Structures and Service Vessels Operating over the 

Course of a Proposed Action under Alternative A for 50 Years. (B, C) Total 

Number of Platforms Installed in the Low and High Production Scenario by 

Water Depth. ............................................................................................................... 3-18

Figure 3-5. (A) Number of Production Wells Drilled over the Course of a Proposed Action 

under Alternative A for 50 Years. (B, C) Total Number of Development and 

Production Wells Drilled in the Low and High Production Scenario by Water Depth 

for Alternative A........................................................................................................... 3-20 

Figure 3-6. Total Oil and Gas Production (BOE) in the Gulf of Mexico in the Low and High 

Production Scenario by Water Depth. ........................................................................ 3-22 

Figure 3-7. The Oil Spill Risk Analysis Model Process. ................................................................ 3-33 

Figure 4-1. Gulf of Mexico Region with the Planning Areas, Nonattainment Areas, and 

Class I and Sensitive Class II Areas........................................................................... 4-16

Figure 4-2. Year 2011 Gulfwide Emission Inventory Results for Total Platform and 

Non-Platform Criteria Pollutant Emissions (TPY)....................................................... 4-23

Figure 4-3. Year 2011 Gulfwide Emission Inventory Results for Total Platform and 

Non-Platform Greenhouse Gas Emissions (TPY). ..................................................... 4-23

Figure 4-4. 2011 Criteria Pollutant Emissions (TPY) from Platform Sources. .............................. 4-24

Figure 4-5. 2011 Greenhouse Gases (TPY) from Platform Sources............................................ 4-24
xlvi 2018 Gulf of Mexico Supplemental EIS

Figure 4-7. Geographic Domain of the “Air Quality Modeling in the Gulf of Mexico” Region 

Study. .......................................................................................................................... 4-37

Figure 4-8. Sargassum Loop System............................................................................................ 4-79

Figure 4-9. Lease Blocks Subject to the Topographic Features and Live Bottom (Pinnacle 

Trend) Stipulations...................................................................................................... 4-84

Figure 4-10. Gulf of Mexico Protected Species’ Critical Habitats. ................................................4-114

Figure 4-11. Economic Land Use Patterns. ..................................................................................4-157

Figure 4-12. Population of BOEM’s Economic Impact Areas in the Gulf of Mexico. ....................4-167

Figure B-1. Location of the “Air Quality Modeling in the Gulf of Mexico Region” Study with 

Class I Areas and Platform Locations.......................................................................... B-1 

Figure B-2. Ozone Nonattainment Areas in the Southeastern U.S................................................ B-2

Figure B-3. Overview of the “Air Quality Modeling in the Gulf of Mexico Region” Study Tasks. ... B-4 

Figure B-4. WRF 36-km CONUS (d01), 12-km SE Regional (d02), and 4-km Gulf of Mexico 

Region (d03) Domains. ................................................................................................ B-7 

Figure B-5. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Wind Direction 

Performance for 2012. ............................................................................................... B-16

Figure B-6. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Wind Speed 

Performance for 2012. ............................................................................................... B-16

Figure B-7. BOEM Gulfof Mexico OCS Region WRF 36-km METSTAT Temperature 

Performance for 2012. ............................................................................................... B-17

Figure B-8. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Humidity 

Performance for 2012. ............................................................................................... B-17

Figure B-9. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Wind Direction 

Performance for 2012. ............................................................................................... B-18

Figure B-10. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Wind Speed 

Performance for 2012. ............................................................................................... B-18

Figure B-11. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Temperature 

Performance for 2012. ............................................................................................... B-19

Figure B-12. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Humidity 

Performance for 2012. ............................................................................................... B-19

Figure B-13. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Wind Direction 

Performance for 2012. ............................................................................................... B-20

Figure B-14. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Wind Speed 

Performance for 2012. ............................................................................................... B-20

Figure B-15. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Temperature 

Performance for 2012. ............................................................................................... B-21

Figure B-16. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Humidity 

Performance for 2012. ............................................................................................... B-21

Figure B-17. Wind Rose Locations for Port Isabel, TX (PTIT), Calcasieu, LA (CAPL), 

Gulfport, MS (KGPT), and Naples, FL (NPSF).......................................................... B-22

Figure B-18. 2012 WRF Wind Rose Compared to 2012 Observation Wind Rose from 

Gulfport, MS in 4-km Domain..................................................................................... B-23
List of Figures xlvii

Figure B-19. 2012 WRF Wind Rose) Compared to 2012 Observation Wind Rose from 

Naples, FL in 4-km Domain. ...................................................................................... B-24

Figure B-20. 2012 WRF Wind Rose Compared to 2012 Observation Wind Rose from 

Port Isabel, TX in 4-km Domain................................................................................. B-25

Figure B-21. 2012 WRF Wind Rose Compared to 2012 Observation Wind Rose from 

Calcasieu, LA in 4-km Domain................................................................................... B-26

Figure B-22. Vertical Profile Soundings Comparing the 4-km WRF to Upper-Air Observations 

Data for Brownsville, TX on August 3, 2012, and Key West, FL on January 4, 

2012, at 00 UTC......................................................................................................... B-28

Figure B-23. January 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain............... B-31

Figure B-24. February 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain. ............ B-32

Figure B-25. March 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain.................. B-33

Figure B-26. April 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain. ................... B-34

Figure B-27. May 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain..................... B-35

Figure B-28. June 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain.................... B-36

Figure B-29. July 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain. .................... B-37

Figure B-30. August 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain. ............... B-38

Figure B-31. September 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain.......... B-39

Figure B-32. October 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain............... B-40

Figure B-33. November 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain........... B-41

Figure B-34. December 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain........... B-42

Figure B-35. January 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain. ............................................................. B-44

Figure B-36. February 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain. ............................................................. B-45

Figure B-37. March 2012 TRMM Precipitation Average) and Corresponding WRF 

Precipitation Average in the 12-km Domain. ............................................................. B-46

Figure B-38. April 2012 TRMM Precipitation Average and Corresponding WRF Precipitation 

Average in the 12-km Domain. .................................................................................. B-47

Figure B-39. May 2012 TRMM Precipitation Average and Corresponding WRF Precipitation 

Average in the 12-km Domain. .................................................................................. B-48

Figure B-40. June 2012 TRMM Precipitation Average and Corresponding WRF Precipitation 

Average in the 12-km Domain. .................................................................................. B-49

Figure B-41. July 2012 TRMM Precipitation Average and Corresponding WRF Precipitation 

Average in the 12-km Domain. .................................................................................. B-50

Figure B-42. August 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain. ............................................................. B-51

Figure B-43. September 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain. ............................................................. B-52

Figure B-44. October 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain. ............................................................. B-53

Figure B-45. November 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain. ............................................................. B-54
xlviii 2018 Gulf of Mexico Supplemental EIS

Figure B-46. December 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain. ............................................................. B-55

Figure B-47. Daily Precipitation Plots from WRF, PRISM, and TRMM on August 30, 2012. ........ B-57

Figure B-48. Daily Precipitation Plots from WRF, PRISM, and TRMM Databases on June 25, 

2012............................................................................................................................ B-58

Figure C-1. Location of the “Air Quality Modeling in the Gulf of Mexico Region” Study, with 

Class I Areas and Platform Locations.......................................................................... C-1 

Figure C-2. Ozone Nonattainment Areas in the Southeastern U.S................................................ C-2 

Figure C-3. Overview of the “Air Quality Modeling in the Gulf of Mexico Region” Study Tasks. ... C-4 

Figure C-4. WRF 36-km CONUS (d01), 12-km SE Regional (d02), and 4-km Gulf of Mexico 

Region (d03) Domains Along With the PGM Grids. .................................................... C-6 

Figure C-5. 2012 Platform NOx Emissions Aggregated by Lease Block ...................................... C-11

Figure C-6. 2012 Platform VOC Emissions Aggregated by Lease Block..................................... C-12

Figure C-7. 2012 Platform PM2.5 Emissions Aggregated by Lease Block.................................... C-13

Figure C-8. 2012 Non-platform NOx Emissions ............................................................................ C-15

Figure C-9. 2012 Non-platform VOC Emissions........................................................................... C-16

Figure C-10. 2012 Non-platform PM2.5 Emissions.......................................................................... C-17

Figure C-11. Emission Estimates for all Planning Areas and Future Activities.............................. C-27

Figure C-12. Combined Annual NOx Emissions. ............................................................................ C-27

Figure C-13. Combined Annual VOC Emissions. ........................................................................... C-28

Figure C-14. Combined Annual PM2.5 Emissions. .......................................................................... C-28

Figure C-15. BOEM OCS Planning Areas and Water Depths........................................................ C-29

Figure D-1. Location of the “Air Quality Modeling in the Gulf of Mexico Region” Study, with 

Class I Areas................................................................................................................ D-1 

Figure D-2. Ozone Nonattainment Areas in the Southeastern U.S................................................ D-4 

Figure D-3. Class I and Sensitive Class II Areas in the Study Region........................................... D-6 

Figure D-4. Overview of the “Air Quality Modeling in the Gulf of Mexico Region” Study Tasks .... D-7 

Figure D-5. Meteorological (WRF model) and PGM Modeling Domains Including the 36-km 

Horizontal Grid Resolution CONUS WRF Domain, 12-km Resolution Southeast 

Regional WRF and PGM Domains (d02), and 4-km Resolution Gulf of Mexico 

OCS Region WRF and PGM Domains (d03)............................................................... D-8 

Figure D-6. BOEM’s 12-km 2012 Base Case NOx Emissions Summary in Tons per Year 

by Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ....................................................................................................................... D-20

Figure D-7. BOEM 12-km 2012 Base Case VOC Emissions Summary in Tons per Year 

by Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ....................................................................................................................... D-21

Figure D-8. BOEM 12-km 2012 Base Case PM2.5 Emissions Summary in Tons per Year 

by Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ....................................................................................................................... D-22

Figure D-9. BOEM 12-km 2012 Base Case SO2 Emissions Summary in Tons per Year 

by Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ....................................................................................................................... D-23
List of Figures xlix

Figure D-10. BOEM 12-km Future Year NOx Emissions Summary in Tons per Year by Source 

Category and State (Alabama, Florida, Louisiana, Mississippi, and Texas)............. D-24

Figure D-11. BOEM 12-km Future Year VOC Emissions Summary in Tons per Year by Source 

Category and State (Alabama, Florida, Louisiana, Mississippi, and Texas)............. D-25

Figure D-12. BOEM 12-km Future Year PM2.5 Emissions Summary in Tons per Year by Source 

Category and State (Alabama, Florida, Louisiana, Mississippi, and Texas)............. D-26

Figure D-13. BOEM 12-km Future Year SO2 Emissions Summary in Tons per Year by Source 

Category and State (Alabama, Florida, Louisiana, Mississippi, and Texas)............. D-27

Figure D-14. Spatial Distribution of NOx, VOC, SO2, and PM2.5 Emissions (tons per year) 

from New OCS Oil and Gas Production Platforms under the Proposed Action........ D-30

Figure D-15. Spatial Distribution of Emissions (tons per year) of NOx, VOC, SO2, and PM2.5 

from BOEM’s OCS Additional Oil and Gas Support Vessels and Helicopters

under the Proposed Action Scenario........................................................................ D-31

Figure D-16. Spatial Distribution of NOx, VOC, SO2, and PM2.5 Emissions (tons per year) 

from BOEM’s OCS Oil and Gas Platforms, Support Vessels, and Helicopters 

under the No Action Alternative in BOEM’s 4-km Domain. ....................................... D-32

Figure D-17. Spatial Distribution of NOx, VOC, SO2, and PM2.5 Emissions (tons per year) 

from All Other Marine Vessel Activity in the Gulf of Mexico under the Future 

Year Scenario in BOEM’s 4-km Domain.................................................................... D-33

Figure D-18. Spatial Distribution of NOx, VOC, SO2, and PM2.5 Emissions (tons per year) 

from Other Anthropogenic U.S. Sources for the Future Year Scenario within 

BOEM’s 4-km Domain................................................................................................ D-34

Figure D-19. Ozone Monitoring Sites Used in the Model Performance Evaluation: CASTNet 

Sites in the Southeastern U.S. and AQS Sites within the 4-km Modeling Domain... D-43

Figure D-20. Speciated PM Monitoring Sites Used in the Model Performance Evaluation: 

CSN Network, IMPROVE Network, and SEARCH Network...................................... D-45

Figure D-21. Monthly Normalized Mean Bias and Normalized Mean Error for Daily Maximum 

8-hour Average Ozone at AQS and CASTNet Monitoring Sites Located within 

the 4-km Modeling Domain and the 12-km Domain .................................................. D-51

Figure D-22. Fraction of Site-days during Each Month of 2012 with Observed Daily Maximum 

8-hour Ozone Exceeding 60, 65, or 70 ppb Over All Monitoring Sites in the 

4-km Domain.............................................................................................................. D-52

Figure D-23. Observed and Predicted Monthly Mean Daily Maximum 8-hour Average Ozone 

Over All Sites in the 4-km Modeling Domain. ............................................................ D-53

Figure D-24. Scatter and Scatter Density Plots for Observed vs. Predicted Daily Maximum 

8-hour Ozone in Q2 and Q3 for All AQS Monitoring Sites in the 4-km Modeling 

Domain....................................................................................................................... D-54

Figure D-25. Normalized Mean Bias (NMB) for Daily Maximum 8-hour Ozone for Q2 and Q3..... D-55

Figure D-26. Time Series of Daily Maximum 8-hour Ozone at Monitoring Sites with Highest 

Design Values in Harris, Brazoria, and Galveston Counties, Texas, for Q2 

and Q3........................................................................................................................ D-57

Figure D-27. Time Series of Daily Maximum 8-hour Ozone at Monitoring Sites in the Baton 

Rouge Nonattainment Area: LSU and Carville for Q2 and Q3.................................. D-57
l 2018 Gulf of Mexico Supplemental EIS

Figure D-28. Time Series of Daily Maximum 8-hour Ozone at the ALC188 (AlabamaCoushatta, Texas) CASTNet Monitoring Site for Q2 and Q3.................................... D-58

Figure D-29. PM Monitoring Sites in the Southeastern U.S. Domain............................................. D-60

Figure D-30. Soccer Plots of Total PM2.5 Mass Model Performance Across the IMPROVE, 

CSN, SEARCH, and FRM Daily Monitoring Networks for Sites in the 

Southeastern U.S. Domain. ....................................................................................... D-61

Figure D-31. Comparisons of Predicted with Observed Daily Average PM at CSN Network 

Sites in the Southeastern U.S. for Q2 and Q4 for Total PM2.5, Other PM2.5, and 

Sodium. ...................................................................................................................... D-62

Figure D-32. Comparisons of Observed vs. Predicted OC and EC at SEARCH and CSN 

Network Sites in the Southeastern U.S. .................................................................... D-63

Figure D-33. Monthly Normalized Mean Bias and Normalized Mean Error for Hourly NO2 and 

Daily NOy at SEARCH Network Sites and AQS Sites in the 4-km Domain.............. D-64

Figure D-34. Monthly Normalized Mean Bias and Normalized Mean Error for NO3 at SEARCH 

Network Monitoring Sites and AQS Sites and NO3 Deposition at NADP Sites 

in the Southeastern U.S............................................................................................. D-65

Figure D-35. Monthly Normalized Mean Bias and Normalized Mean Error at Monitoring Sites 

in the 4-km Domain for SO2, SO4, and SO4 Deposition Measured at NADP Sites... D-67

Figure D-36. Annual Normalized Mean Bias for Hourly SO2 (based on 12-km resolution CAMx 

results)........................................................................................................................ D-68

Figure D-37. Monthly Normalized Mean Bias and Normalized Mean Error for Daily Average 

NH4 at CSN and SEARCH Network Sites in the 4-km Modeling Domain................. D-69

Figure D-38. Monthly Normalized Mean Bias and Normalized Mean Error for Hourly CO at 

SEARCH Network Sites and AQS Sites.................................................................... D-70

Figure D-39. Class I and Sensitive Class II Areas for Which Incremental AQ/AQRV Impacts 

Were Calculated......................................................................................................... D-74

Figure D-40. Base Scenario Ozone Design Values, Future Year Ozone Design Values and 

Their Differences Calculated Using the MATS UAA Tool. ........................................ D-88

Figure D-41. MATS UAA Future Year Ozone Design Values (DFV) Calculated After First 

Removing the Hourly Contributions from a Source Group and the Corresponding 

Contributions of the Source Group to DVF Calculated by Subtracting the DVFs 

Shown in the Left-hand Column from the “All Sources” DVF Shown in the Top 

Right-hand Corner of Figure D-40 ............................................................................. D-89

Figure D-42. Modeled 4th Highest MDA8 Ozone for the Base Year and Future Year Scenarios 

and Their Differences................................................................................................. D-90

Figure D-43. Contributions of Source Groups A, B, C, D, and E to Future Year All-sources 

4th Highest MDA8...................................................................................................... D-92

Figure D-44. Contributions from Source Group F (natural and non-U.S. emission sources 

including boundary conditions) and Boundary Conditions Only, to Future Year 

All-sources 4th Highest MDA8................................................................................... D-93

Figure D-45. Current Year (DVC) and Future Year (DVF) Annual Average PM2.5 Design 

Values from the MATS Unmonitored Area Analysis and the Difference, 

DVF – DVC................................................................................................................. D-99
List of Figures li

Figure D-46. Contributions of Source Groups A, B, C, D, and E to the Future Year All-sources 

Annual Average PM2.5 Concentration Based on the MATS Unmonitored Area 

Analysis .................................................................................................................... D-100

Figure D-47. Modeled 8th Highest Daily Average PM2.5 Concentrations for the Base Year, 

Future Year, and the Future – Base Difference....................................................... D-102

Figure D-48. Contributions of Source Groups A, B, C, D, and E to the Future Year 

All-sources 8th Highest Daily Average PM2.5 Concentration.................................... D-103

Figure D-49. Contributions from Source Group F (natural and non-U.S. emission sources 

including boundary conditions) and Boundary Conditions Only to Future Year 

All-sources 8th Highest 24-hour PM2.5...................................................................... D-104

Figure D-50. Modeled Annual Average PM2.5 Concentrations for the Base Year, Future 

Year, and the Future – Base Difference .................................................................. D-105

Figure D-51. Contributions of Source Group A, B, C, D, and E to the Future Year All-sources 

Annual Average PM2.5 Concentration ...................................................................... D-106

Figure D-52. Contributions from Source Group F (natural and non-U.S. emission sources 

including boundary conditions) and Boundary Conditions Only to Future Year 

All-sources Annual Average PM2.5........................................................................... D-107

Figure D-53. Modeled 2nd Highest 24-hour Average PM10 Concentrations for the Base Year, 

Future Year, and the Future – Base Difference....................................................... D-108

Figure D-54. Contributions of Source Groups A, B, C, D, and E to the Future Year 

All-sources 2nd Highest Daily Average PM10 Concentration................................... D-109

Figure D-55. Contributions from Source Group F (natural and non-U.S. emission sources 

including boundary conditions) and Boundary Conditions Only to Future Year 

All-sources 2nd Highest Daily Average PM10 Concentration................................... D-110

Figure D-56. Modeled 8th Highest 1-hour NO2 Concentrations for the Base Year, Future 

Year, and the Future – Base Difference. ................................................................. D-111

Figure D-57. Contributions of Source Group A, B, C, D, and E to the Future Year All-sources 

8th Highest Daily Average NO2 Concentrations ....................................................... D-112

Figure D-58. Modeled Annual Average NO2 Concentrations for the Base Year, Future Year, 

and the Future – Base Difference............................................................................ D-113

Figure D-59. Contributions of Source Groups A, B, C, D, and E to the Future Year 

All-sources Annual Average NO2 Concentrations. .................................................. D-114

Figure D-60. Modeled 4th Highest Daily Maximum 1-hour SO2 Concentrations for the Base 

Year, Future Year, and the Future – Base Difference............................................. D-116

Figure D-61. Contributions of Source Group A, B, C, D, and E to the Future Year All-sources 

4th Highest Daily Maximum 1-hour SO2 Concentration .......................................... D-117

Figure D-62. Modeled Annual 2nd Highest Block 3-hour SO2 Concentrations for the Base 

Year, Future Year, and the Future – Base Difference............................................. D-118

Figure D-63. Contributions of Source Group A, B, C, D, and E to the Future Year All-sources 

2nd Highest 3-hour Block Average SO2 Concentration........................................... D-119

Figure D-64. Modeled Annual 2nd Highest Non-overlapping Running 8-hour Average 

CO Concentrations for the Base Year, Future Year, and the Future – Base 

Difference................................................................................................................. D-120
lii 2018 Gulf of Mexico Supplemental EIS

Figure D-65. Modeled Annual 2nd Highest 1-hour Average CO Concentrations for the Base 

Year, Future Year, and the Future – Base Difference............................................. D-121
List of Tables liii

LIST OF TABLES

Page

Table 2-1. Applicable Stipulations by Alternative.......................................................................... 2-15

Table 2-2. Alternative Comparison Matrix..................................................................................... 2-20

Table 3-1. Offshore Scenario Activities Related to a Single Proposed Lease Sale for 

Alternative A, B, or C from 2017 through 2066. ........................................................... 3-13

Table 3-2. Percent of Production of Each Alternative of a Single Proposed Lease Sale 

(2017-2066) in Relation to Each Cumulative Production Scenario............................. 3-14

Table 3-3. Exploration and Seismic Survey Activity Leading Up To and Following a Proposed 

Lease Sale in the Gulf of Mexico ................................................................................. 3-15

Table 3-4. Existing Coastal Infrastructure Related to OCS Oil- and Gas-Related Activities 

in the Gulf of Mexico. ................................................................................................... 3-19

Table 3-5. Projected Oil and Gas in the Gulf of Mexico OCS....................................................... 3-21 

Table 3-6. Depth Distributions within the Proposed Regionwide Lease Sale Area...................... 3-22

Table 3-7. Oil Transportation Scenario under Alternative A, B, or C............................................ 3-23

Table 3-8. Summary of the Timing of Impact-Producing Factors Associated with Routine 

Oil and Gas Activities................................................................................................... 3-25

Table 3-9. General Description of Routine Impact-Producing Factors......................................... 3-26

Table 3-10. Mean Number and Sizes of Spills Estimated to Occur in OCS Offshore Waters 

from an Accident Related to Rig/Platform and Pipeline Activities Supporting Each 

Alternative Over a 50-Year Time Period...................................................................... 3-34

Table 3-11. Oil-Spill Occurrence Probability Estimates for Offshore Spills ≥1,000 Barrels 

Resulting from Each Alternative (2017-2066) and the Cumulative OCS Oil and 

Gas Program (2017-2086). .......................................................................................... 3-35

Table 3-12. Oil-Spill Occurrence Probability Estimates for Offshore Spills ≥10,000 Barrels 

Resulting from Each Alternative (2017-2066) and the Cumulative OCS Oil and 

Gas Program (2017-2086). .......................................................................................... 3-35

Table 3-13. Historic Spill Source, Location, and Characteristics of a Maximum Spill for 

Coastal Waters............................................................................................................. 3-37

Table 3-14. Summary of the Timing of Impact-Producing Factors Associated with Accidental 

Oil and Gas Events. ..................................................................................................... 3-40

Table 3-15. General Description of Accidental Event Impact-Producing Factors. ......................... 3-41

Table 3-16 Future Activity Projections Associated with the Cumulative OCS Oil and Gas 

Program (2017-2086), Including All Future Activities that are Projected to Occur 

from Past, Proposed, and Future Lease Sales............................................................ 3-44

Table 3-17. Future Oil Transportation Projections Associated with the Cumulative OCS Oil 

and Gas Program (2017-2086), Including All Future Transportation that is 

Projected to Occur from Past, Proposed, and Future Lease Sales. ........................... 3-46

Table 3-18. General Description of Cumulative Non-OCS Oil- and Gas-Related 

Impact-Producing Factors............................................................................................ 3-47

Table 4-1. Air Quality Impact-Producing Factors That Are Reasonably Foreseeable.................. 4-15
liv 2018 Gulf of Mexico Supplemental EIS

Table 4-2. National Ambient Air Quality Standards. ..................................................................... 4-18

Table 4-3. Nonattainment and Maintenance Areas in the Gulf of Mexico Region........................ 4-20

Table 4-4. Source Categories for Source Apportionment Calculations........................................ 4-38

Table 4-5. NAAQS and PSD Increments. ..................................................................................... 4-39

Table 4-6. Class I and Sensitive Class II Areas in Gulf Coast and Nearby States....................... 4-44

Table 4-7. Source Group for Incremental Impacts Analysis. ........................................................ 4-46

Table 4-8. Water Quality Impact-Producing Factors That Are Reasonably Foreseeable. ........... 4-58

Table 4-9. Estuarine Systems Impact-Producing Factors That Are Reasonably Foreseeable. ... 4-62

Table 4-10. Coastal Barrier Beaches and Associated Dunes Impact-Producing Factors.............. 4-67

Table 4-11. Deepwater Benthic Communities Impact-Producing Factors That Are 

Reasonably Foreseeable. ............................................................................................ 4-74

Table 4-12. Sargassum and Associated Communities Impact-Producing Factors That Are 

Reasonably Foreseeable. ............................................................................................ 4-81

Table 4-13. Topographic Features and Associated Communities Impact-Producing Factors 

That Are Reasonably Foreseeable. ............................................................................. 4-88

Table 4-14. Pinnacles and Low-Relief Features and Associated Communities 

Impact-Producing Factors That Are Reasonably Foreseeable. .................................. 4-96

Table 4-15. Fish and Invertebrate Resources Impact-Producing Factors That Are 

Reasonably Foreseeable. ..........................................................................................4-103

Table 4-16. Birds Impact-Producing Factors That Are Reasonably Foreseeable. .......................4-109

Table 4-17. Species within the Gulf of Mexico That Are Protected Under the Endangered 

Species Act and/or the Marine Mammal Protection Act. ...........................................4-112

Table 4-18. Protected Species Impact-Producing Factors That Are Reasonably 

Foreseeable. ..............................................................................................................4-115

Table 4-19. Commercial Fisheries Impact-Producing Factors That Are Reasonably 

Foreseeable. ..............................................................................................................4-141

Table 4-20. Recreational Fishing Impact-Producing Factors That Are Reasonably 

Foreseeable. ..............................................................................................................4-144

Table 4-21. Recreational Resources Impact-Producing Factors That Are Reasonably 

Foreseeable. ..............................................................................................................4-148

Table 4-22. Archaeological Surveys and Resources Identified, 2009-2014.................................4-151

Table 4-23. Land Use and Coastal Infrastructure Impact-Producing Factors That Are 

Reasonably Foreseeable. ..........................................................................................4-159

Table B-1. Nonattainment and Maintenance Areas in the Southeastern U.S................................ B-3

Table B-2. BOEM’s Gulf of Mexico OCS Region WRF Domain Configuration.............................. B-6

Table B-3. BOEM Gulf of Mexico OCS Region WRF Dataset Model Levels................................. B-8

Table B-4. BOEM Gulf of Mexico OCS Region WRF Physics Options........................................ B-11

Table B-5. Meteorological Model Performance Benchmarks for Simple and Complex 

Conditions. .................................................................................................................. B-12

Table C-1. Nonattainment and Maintenance Areas in the Southeastern U.S................................ C-3

Table C-2. Gulf of Mexico Air Quality Modeling Study Source Categories. ................................... C-7

Table C-3. Base Case Offshore Oil and Gas Production Source Emissions Estimates 

for the GOM Western and Central/Eastern Planning Areas....................................... C-10
List of Tables lv

Table C-4. Future Year Production Platform Emission Factors. .................................................. C-21

Table C-5. Summary of Vessel Characteristics............................................................................ C-23

Table C-6. Load Factors to be Used in the Future Year Projections............................................ C-24

Table C-7. Marine Vessel Emission Factors (g/kW-hr). ............................................................... C-24

Table C-8. Emission Estimates for the Western, Central, and Eastern Planning Areas, 

All Depths, By Year and Pollutant............................................................................... C-25

Table D-1. Nonattainment and Maintenance Areas in the Southeastern U.S................................ D-5

Table D-2. Gulf of Mexico OCS Region Air Quality Modeling Study Source Categories............. D-10

Table D-3. 2012 Fire Criteria Air Pollutant Emissions Summary by Fire Type for BOEM’s 

36-, 12-, and 4-km Domains. ...................................................................................... D-15

Table D-4. 2012 Base Case and Future Year Emissions Summary by State for BOEM’S 

12-km Domain (only Gulf Coast States: Alabama, Florida, Louisiana, Mississippi, 

and Texas). ................................................................................................................. D-19

Table D-5. 2012 Base Case and Future Year Emissions Summary by Source Category 

for BOEM’s 4-km Domain. .......................................................................................... D-27

Table D-6. Changes in Emissions between the 2012 Base Case and Future Year Emissions 

(short tons per year) by Source Category for BOEM’s 4-km Domain. ....................... D-28

Table D-7. Source Categories for Source Apportionment Calculations....................................... D-35

Table D-8. Domain Grid Definitions for the WRF and CAMx/CMAQ Modeling............................ D-36

Table D-9. Vertical Layer Interface Definition for WRF Simulations and the Layer-collapsing 

Scheme for the CAMx/CMAQ Layers ......................................................................... D-37

Table D-10. CAMx Model Configuration. ........................................................................................ D-40

Table D-11. Definitions of Model Performance Evaluation Statistical Metrics. .............................. D-46

Table D-12. Ozone and PM Model Performance Goals and Criteria. ............................................ D-47

Table D-13. Model Performance Statistics at Different Observed Ozone Concentration 

Screening Thresholds Based on All Monitoring Sites in the 4-km Domain................ D-56

Table D-14. NAAQS and PSD Increments. .................................................................................... D-72

Table D-15. Source Group for Incremental Impacts Analysis. ....................................................... D-73

Table D-16. Class I and Sensitive Class II Areas in Gulf Coast and Nearby States...................... D-75

Table D-17. Current Year (DVC) and Future Year (DVF) Ozone Design Values at Ambient 

Air Monitoring Sites within the 4-km Modeling Domain from MATS........................... D-83

Table D-18. Ozone Current (DVC) and Future Year (DVF) Design Values and Reduction 

in DVF with Contributions from Individual Source Groups Removed......................... D-85

Table D-19. MATS Ozone Design Value Results for All Monitoring Sites Where Exclusion 

of Contributions from Source Group A or B is Sufficient to Reduce the Predicted 

Future Design Value (DVF) from Above the NAAQS to Below the NAAQS 

(all values in ppb). ....................................................................................................... D-87

Table D-20. Current Year (DVC) and Future Year (DVF) 24-Hour PM2.5 Design Values for 

Monitoring Sites in the 4-km Modeling Domain from MATS....................................... D-94

Table D-21. 24-Hour PM2.5 Current (DVC) and Future Year (DVF) Design Values and 

Reduction in DVF with Contributions from Individual Source Groups Removed. ...... D-95

Table D-22. Current (DVC) and Projected Future (DVF) Annual Average PM2.5 Design Values 

for Monitoring Sites in the 4-km Modeling Domain..................................................... D-96
lvi 2018 Gulf of Mexico Supplemental EIS

Table D-23. Annual Average PM2.5 Future Year Design Values (DVF) and Change in DVF 

with Contributions from Individual Source Groups Removed..................................... D-97

Table D-24. Maximum Source Group Contributions for PSD Pollutants at Class I and 

Sensitive Class II Areas in the 4-km Modeling Domain............................................ D-122

Table D-25. Source Group Contributions for PSD Pollutants at All Class I and Sensitive 

Class II Areas in the 4-km Modeling Domain............................................................ D-124

Table D-26. Incremental Visibility Impacts Relative to Natural Background Conditions from 

Source Group A......................................................................................................... D-125

Table D-27. Incremental Visibility Impacts Relative to Natural Background Conditions from 

Source Group B......................................................................................................... D-126

Table D-28. Cumulative Visibility Results for 20% Worst Visibility Days (W20%) at Class I 

Areas for Base (2012) Year (BY) and Future Year (FY) Scenarios with All 

Sources Included and with Contributions from Each Source Group Removed. ...... D-129

Table D-29. Differences in Cumulative Visibility Results for 20% Worst Visibility Days 

(W20%) at Class I Areas Between the Future Year (FY) and Base Year (BY) 

Scenarios and Contributions of Each Source Group to the Future Year Scenario 

Visibility...................................................................................................................... D-131

Table D-30. Cumulative Visibility Results for 20% Best Visibility Days (B20%) at Class I 

Areas for Base (2012) Year (BY) and Future Year (FY) Scenarios with All 

Sources Included and with Contributions from Each Source Group Removed. ...... D-133

Table D-31. Differences in Cumulative Visibility Results for 20% Best Visibility Days (B20%) 

at Class I Areas Between the Future Year (FY) and Base Year (BY) Scenarios 

and Contributions of Each Source Group to the Future Year Scenario Visibility..... D-134

Table D-32. Deposition Analysis Threshold Values (kg/ha/yr) as Defined in the Federal 

Land Manager Guidance........................................................................................... D-136

Table D-33. Incremental Deposition Impacts from Source Groups A and B at Class I and 

Sensitive Class II Areas in the 4-km Domain............................................................ D-136

Table D-34. Cumulative Nitrogen (N) and Sulfur (S) Deposition Impacts (kg/ha/yr) under the 

Base and Future Year Scenarios.............................................................................. D-137
Abbreviations and Acronyms lvii

ABBREVIATIONS AND ACRONYMS

°C degree Celsius

°F degree Fahrenheit

μg microgram

μm micrometer

2017-2022 GOM Multisale 

EIS

Gulf of Mexico OCS Oil and Gas Lease Sales: 2017-2022; Gulf of 

Mexico Lease Sales 249, 250, 251, 252, 253, 254, 256, 257, 259, 

and 261—Final Multisale Environmental Impact Statement

2D two dimensional

3D three dimensional

ac acre

Agreement Agreement between the United States of America and the United 

Mexican States Concerning Transboundary Hydrocarbon Reservoirs 

in the Gulf of Mexico

API American Petroleum Institute

Area ID Area Identification

AQRV air quality-related value

bbl barrel

Bbbl billion barrels

Bcf billion cubic feet

BBO billion barrels of oil

BOE billion barrels of oil equivalent

BOEM Bureau of Ocean Energy Management

B.P. Before Present

BSEE Bureau of Safety and Environmental Enforcement

BTEX benzene, toluene, ethylbenzene, and xylene

Call Call for Information

CAMx Comprehensive Air-quality Model with extensions

CD Consistency Determination

CEQ Council on Environmental Quality

CFR Code of Federal Regulations

CG Coast Guard (also: USCG)

CH4 methane

CMAQ Community Multiscale Air Quality

CMP Coastal Management Program

CO carbon monoxide

CO2 carbon dioxide

CO2-e CO2-equivalent

COE Corps of Engineers (U.S. Army)

CPA Central Planning Area

CZMA Coastal Zone Management Act

dB re: 1μPa decibels referenced 1 microPascal
lviii 2018 Gulf of Mexico Supplemental EIS

DOCD development operations coordination document

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

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

DPP development and production plan

EFH essential fish habitat

e.g. for example

EIA Economic Impact Area

EIS environmental impact statement

EP exploration plan

EPA Eastern Planning Area

ESA Endangered Species Act of 1973

et al. and others

et seq. and the following

Five-Year Program 2017-2022 Outer Continental Shelf Oil and Gas Leasing: 

Proposed Final Program (also: 2017-2022 Five-Year Program)

Five-Year Program EIS Outer Continental Shelf Oil and Gas Leasing Program: 2017-2022, 

Final Programmatic Environmental Impact Statement

FPSO floating production, storage, and offloading system

FR Federal Register

ft feet

FWS Fish and Wildlife Service

G&G geological and geophysical

GOADS Gulfwide Offshore Activity Data System

GOM Gulf of Mexico

GWEI Gulfwide Emission Inventory

H2S hydrogen sulfide

ha hectare

HRG high-resolution geophysical

Hz Hertz

i.e. that is

km kilometer

LA Louisiana

LCA Louisiana Coastal Area

LNG liquefied natural gas

LOOP Louisiana Offshore Oil Port

m meter

MAG-PLAN MMS Alaska-GOM Model Using IMPLAN

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

MATS Modeled Attainment Test Software

mg/L milligrams/liter

mi mile

mm millimeter

MMbbl million barrels
Abbreviations and Acronyms lix

MMPA Marine Mammal Protection Act

MMS Minerals Management Service

MODU mobile offshore drilling unit

MOU Memorandum of Understanding

MSCVAFF Mississippi Coalition for Vietnamese-American Fisher Folks and 

Families

N. north

N2O nitrous oxide

NAAQS National Ambient Air Quality Standards

NASA National Aeronautics and Space Administration

NEPA National Environmental Policy Act

NMFS National Marine Fisheries Service

nmi nautical-mile

NO2 nitrogen dioxide

NOx nitrogen oxides

NOAA National Oceanic and Atmospheric Administration

NPDES National Pollutant Discharge Elimination System

NPS National Park Service

NRDA Natural Resource Damage Assessment

NTL Notice to Lessees and Operators

O3 ozone

OCS Outer Continental Shelf

OCSLA Outer Continental Shelf Lands Act

OSAT Operational Science Advisory Team

OSHA Occupational Safety and Health Administration

OSRA Oil Spill Risk Analysis

OSRP oil-spill response plan

OSV offshore supply/service vessel

Pb lead

PBR Potential Biological Removal

PDARP/PEIS Deepwater Horizon Oil Spill: Programmatic Damage Assessment 

and Restoration Plan and Final Programmatic Environmental 

Impact Statement

PM particulate matter

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

PM10 particulate matter less than or equal to 10 μm

ppb parts per billion

ppm parts per million

PSD Prevention of Significant Deterioration

ROD Record of Decision

Secretary Secretary of the Interior

SO2 sulphur dioxide

SOx sulphur oxides
lx 2018 Gulf of Mexico Supplemental EIS

Tcf trillion cubic feet

Trustees Natural Resource Damage Assessment Trustees

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

USDOE U.S. Department of Energy

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

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

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

VGP Vessel General Permit

VOC volatile organic compound

VSP vertical seismic profiling

W. west

WPA Western Planning Area

WRF Weather and Research Forecasting

yr year
Conversion Chart lxi

CONVERSION CHART

To convert from To Multiply by

centimeter (cm) inch (in) 0.3937

millimeter (mm) inch (in) 0.03937

meter (m) foot (ft) 3.281

meter2 (m2) foot2 (ft2) 10.76

meter2 (m2) yard2 (yd2) 1.196

meter2 (m2) acre (ac) 0.0002471

meter3 (m3) foot3 (ft3) 35.31

meter3 (m3) yard3 (yd3) 1.308

kilometer (km) mile (mi) 0.6214

kilometer2 (km2) mile2 (mi2) 0.3861

hectare (ha) acre (ac) 2.47

liter (L) gallons (gal) 0.2642

degree Celsius (°C) degree Fahrenheit (°F) °F = (1.8 x °C) + 32

1 barrel (bbl) = 42 gal = 158.9 L = approximately 0.1428 metric tons

1 nautical mile (nmi) = 1.15 mi (1.85 km) or 6,076 ft (1,852 m)

tonnes = 1 long ton or 2,240 pounds (lb)

CHAPTER 1 

 

THE PROPOSED ACTION

The Proposed Action 1-3 

This Supplemental EIS contains 

analyses of the potential 

environmental impacts that could 

result from a single proposed lease 

sale (e.g., Lease Sale 250), but the 

analyses may be applied and 

supplemented as necessary to inform 

decisions for each of the remaining 

proposed lease sales scheduled in 

the Five-Year Program.

What’s in This Chapter?

• The Bureau of Ocean Energy Management (BOEM) has issued the 2017-2022 Outer 

Continental Shelf Oil and Gas Leasing: Proposed Final Program (Five-Year Program). It 

sets forth a schedule for 10 proposed regionwide Gulf of Mexico lease sales spaced evenly 

throughout the 5-year period.

• The Gulf of Mexico OCS Oil and Gas Lease Sales: 2017-2022; Gulf of Mexico Lease 

Sales 249, 250, 251, 252, 253, 254, 256, 257, 259, and 261—Final Multisale 

Environmental Impact Statement (2017-2022 GOM Multisale EIS) is an EIS that provides 

the environmental review foundation for all 10 proposed GOM lease sales in the Five-Year 

Program schedule.

• This Supplemental EIS has been prepared to inform decisions for the proposed 2018 GOM 

lease sales in the Five-Year Program. It tiers from and updates the 2017-2022 GOM 

Multisale EIS and contains analyses of the potential environmental impacts that could 

result from a proposed regionwide lease sale (e.g., Lease Sale 250), but the analyses may 

be applied and supplemented as necessary to inform decisions for each of the remaining 

proposed lease sales scheduled in the Five-Year Program. 

• The proposed action in this Supplemental EIS is to hold a regionwide lease sale in the 

GOM according to the schedule of proposed lease sales set forth by the Five-Year 

Program.

• The purpose of a proposed lease sale in this Supplemental EIS is to offer for lease those 

areas in the Gulf of Mexico (GOM) that may contain economically recoverable oil and gas 

resources in accordance with the Outer Continental Shelf Lands Act (OCSLA), subject to 

environmental safeguards.

• The need for a proposed lease sale in this Supplemental EIS is to manage the 

development of Outer Continental Shelf (OCS) energy resources in an environmentally and 

economically responsible manner. Oil and gas from the Gulf of Mexico OCS would 

contribute to meeting domestic demand and enhance national economic security.

• This Supplemental EIS explains the environmental considerations used to assess the 

potential environmental consequences of a proposed lease sale and its alternatives, as 

well as the potential mitigations that could minimize or avoid those consequences.

• The decision on whether and how to proceed with proposed Lease Sale 250 will be made 

following the completion of this National Environmental Policy Act (NEPA) analysis. A 

separate decision will be made for proposed Lease Sale 251 and the remaining proposed 

regionwided lease sales scheduled in the Five-Year Program.

1 THE PROPOSED ACTION

1.0 INTRODUCTION

This Supplemental Environmental Impact 

Statement (EIS) addresses a proposed Federal action – 

a regionwide lease sale. This Supplemental EIS is 

expected to be used to inform decisions on proposed 

Outer Continental Shelf (OCS) oil and gas Lease Sales 

250 and 251 in the Gulf of Mexico, as scheduled in the 

2017-2022 Outer Continental Shelf Oil and Gas Leasing: 

Proposed Final Program (Five-Year Program; USDOI, 

BOEM, 2016a). This Supplemental EIS is expected to be 

used to inform decisions for each of the two lease sales 
1-4 2018 Gulf of Mexico Supplemental EIS

This Supplemental EIS tiers from 

and updates the Gulf of Mexico 

OCS Oil and Gas Lease Sales: 

2017-2022; Gulf of Mexico Lease 

Sales 249, 250, 251, 252, 253, 

254, 256, 257, 259, and 261—

Final Multisale Environmental 

Impact Statement (2017-2022 

GOM Multisale EIS).

scheduled in 2018 and to be used and supplemented as necessary for decisions on future Gulf of 

Mexico proposed regionwide lease sales. This Supplemental EIS contains analyses of the potential 

environmental impacts that could result from a proposed regionwide lease sale in the Gulf of Mexico 

as scheduled in the Five-Year Program, but the analyses may be applied and supplemented as 

necessary to inform decisions for each of the remaining proposed lease sales scheduled in the FiveYear Program. This Supplemental EIS tiers from and updates the Gulf of Mexico OCS Oil and Gas 

Lease Sales: 2017-2022; Gulf of Mexico Lease Sales 249, 250, 251, 252, 253, 254, 256, 257, 259, 

and 261—Final Multisale Environmental Impact Statement (2017-2022 GOM Multisale EIS; USDOI, 

BOEM, 2017a) and incorporates by reference all of the 

relevant material in the 2017-2022 GOM Multisale EIS. 

The decision on whether and how to proceed with proposed 

Lease Sale 250 will be made following the completion of 

this National Enviornmental Policy Act (NEPA) analysis. A 

separate decision will be made for the second lease sale of 

2018, i.e., proposed Lease Sale 251. Decisions on the 

remaining proposed GOM lease sales in the Five-Year 

Program will be made based on additional NEPA review 

that may update this Supplemental EIS as necessary.

The Bureau of Ocean Energy Management (BOEM) has issued the Five-Year Program 

(USDOI, BOEM, 2016a). The Five-Year Program proposes 10 regionwide Gulf of Mexico (GOM) oil 

and gas lease sales. Five regionwide lease sales are 

tentatively scheduled in August of each year from 

2017 through 2021 and five regionwide lease sales 

are tentatively scheduled in March of each year from 

2018 through 2022. The lease sales proposed in the 

GOM in the Five-Year Program are regionwide lease 

sales comprised of the Western, Central, and a small 

portion of the Eastern Planning Areas (WPA, CPA, 

and EPA, respectively) not subject to Congressional 

moratorium. These planning areas are located off the 

States of Texas, Louisiana, Mississippi, Alabama, 

and Florida (Figure 1-1).

2017-2022 Schedule of Proposed

Gulf of Mexico OCS Region 

Lease Sales 

Lease Sale Number Year

249 2017

250 and 251 2018

252 and 253 2019

254 and 256 2020

257 and 259 2021

261 2022
The Proposed Action 1-5 

The proposed action is to hold a 

lease sale in the GOM according to 

the schedule of proposed lease sales 

set forth by the Five-Year Program.

Figure 1-1. Proposed Regionwide Lease Sale Area Combining the Western, Central, and Eastern 

Planning Areas.

The development of the Five-Year Program initiates region-specific NEPA reviews for each 

of the proposed lease sales. Region-specific reviews are conducted by Program Area, and this 

Supplemental EIS contains analyses for the Gulf of Mexico OCS Region. Even though the 

Five-Year Program includes regionwide lease sales for the GOM, any individual lease sale could still 

be scaled back during the prelease sale process, including for example, to employ the separate 

planning area model used in the Proposed Final Outer Continental Shelf Oil & Gas Leasing 

Program: 2012-2017 (2012-2017 Five-Year Program; USDOI, BOEM, 2012), should circumstances 

warrant. For more detail on the Five-Year Program and its relationship to the individual lease sale 

consultation and decision process, refer to Chapter 1.3.1 of the 2017-2011 GOM Multisale EIS.

The Proposed Action

The proposed action evaluated in this 

Supplemental EIS is to hold a regionwide lease sale in the 

GOM according to the schedule of proposed lease sales 

set forth by the Five-Year Program. This Supplemental 

EIS has been prepared to inform decisions for the 

proposed 2018 GOM lease sales and analyzes a single 

proposed action (i.e., a single proposed lease sale in the Gulf of Mexico) as scheduled in the FiveYear Program. Since each of the 10 proposed lease sales in the GOM region are very similar and 

occur in close timeframes, BOEM prepared an EIS for a proposed action, looking at the 10 proposed 

lease sales in the Five-Year Program cumulatively (i.e., the 2017-2022 GOM Multisale EIS). The 

analysis in the 2017-2022 GOM Multisale EIS will be used to inform each of the 10 proposed lease 

sale decisions. This Supplemental EIS tiers from and updates the 2017-2022 GOM Multisale EIS 
1-6 2018 Gulf of Mexico Supplemental EIS

“It is hereby declared to be the policy 

of the United States that ... the Outer 

Continental Shelf is a vital national 

resource held by the Federal 

Government for the public, which 

should be made available for 

expeditious and orderly development, 

subject to environmental safeguards, 

in a manner which is consistent with 

the maintenance of competition and 

other national needs."

OCSLA, 43 U.S.C. §§ 1331 et seq.

and contains analyses of the potential environmental impacts that could result from a single 

proposed lease sale (e.g., Lease Sale 250), but the analyses may be applied and supplemented as 

necessary to inform decisions for each of the remaining proposed lease sales scheduled in the 

Five-Year Program. However, pursuant to the OCSLA’s staged leasing process, BOEM must make 

an individual decision on whether and how to proceed with each proposed lease sale. Therefore, in 

order to make an informed decision on a single proposed lease sale, the analyses contained in this 

Supplemental EIS examine impacts from a single proposed lease sale (e.g., Lease Sale 250). The 

decision on whether and how to proceed with proposed Lease Sale 250, which is the first GOM 

lease sale proposed for 2018, will be made following the completion of this NEPA analysis. A 

separate decision will be made for proposed Lease Sale 251, which is the second GOM lease sale 

proposed for 2018. Decisions on the remaining proposed GOM lease sales in the Five-Year 

Program will be made based on additional NEPA review that may update this Supplemental EIS as 

necessary. 

1.1 PURPOSE OF THE PROPOSED ACTION

The Outer Continental Shelf Lands Act of 1953, 

as amended (43 U.S.C. §§ 1331 et seq.), hereafter 

referred to as OCSLA, establishes the Nation’s policy for 

managing the vital energy and mineral resources of the 

OCS. Section 18 of OCSLA requires the Secretary to 

prepare and maintain a schedule of proposed OCS oil 

and gas lease sales determined to “best meet national 

energy needs for the 5-year period following its approval 

or reapproval” (43 U.S.C. § 1344). The Five-Year

Program establishes a schedule that the U.S. Department 

of the Interior (USDOI or DOI) will use as a basis for 

considering where and when leasing might be appropriate 

over a 5-year period.

The purpose of the proposed Federal action addressed in this Supplemental EIS (i.e., a 

proposed regionwide lease sale) is to offer for lease those areas that may contain economically 

recoverable oil and gas resources in accordance with OCSLA, which specifically states that these 

areas “should be made available for expeditious and orderly development, subject to environmental 

safeguards” (OCSLA, 43 U.S.C. §§ 1331 et seq.). Each individual proposed lease sale would 

provide qualified bidders the opportunity to bid upon and lease available acreage in the Gulf of 

Mexico OCS in order to explore, develop, and produce oil and natural gas. This Supplemental EIS 

will determine the potential environmental impacts that could result from a single proposed lease 

sale (e.g., Lease Sale 250) scheduled in the Five-Year Program, but the analyses may be applied 

and supplemented as necessary for each remaining Federal action (lease sale) scheduled in the 

Five-Year Program. 
The Proposed Action 1-7 

1.2 NEED FOR THE PROPOSED ACTION

The need for the proposed action (i.e., a proposed regionwide lease sale) is to manage the 

development of the OCS energy resources in an environmentally and economically responsible 

manner, as required under Section 18 of the OCSLA. Oil serves as the feedstock for liquid 

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

from the Gulf of Mexico OCS contributes to meeting domestic demand and enhances national 

economic security. Since the U.S. is expected to continue to rely on oil and natural gas to meet its 

energy needs, each proposed action would contribute to meeting domestic demand and to reducing

the need for imports of these resources. Refer to Chapter 1.2 of the 2017-2022 GOM Multisale EIS 

for details on petroleum consumption and energy needs in the United States, as well as the Gulf of 

Mexico OCS region’s resource potential.

1.3 OCS OIL AND GAS PROGRAM PLANNING AND DECISION PROCESS

BOEM produces NEPA documents for each of the major stages of energy development 

planning. These documents include an overarching Five-Year Program EIS for the Five-Year 

Program, NEPA review for the individual decisions on oil and gas lease sales, and site-specific 

reviews for the approval of exploration, development and production, and decommissioning plans

and permits (Figure 1-2). This Supplemental EIS is a NEPA review for the individual decision on an 

oil and gas lease sale.

Figure 1-2. OCS Oil and Gas Program Development Process. 
1-8 2018 Gulf of Mexico Supplemental EIS

1.3.1 Prelease Process

BOEM has a two-stage Federal offshore prelease sale planning process: 

(1) develop a Five-Year Program of proposed offshore lease sales for the OCS 

Program; and

(2) conduct an individual lease sale consultation and decision process for each 

lease sale scheduled in the approved Five-Year Program.

Due to the staged decisionmaking process in OCSLA, BOEM does a staged or tiered 

process in which NEPA documents are prepared that cover potential impacts associated with the 

various stages of the OCSLA process. This includes analyses at the Five-Year Program stage, 

proposed lease sale stage, exploration or development and production plan stage, and various 

permitting stages, including, but not limited to, drilling and decommissioning. At the lease sale 

stage, this is typically done through an EIS, which analyzes the potential impacts of postlease 

activities. However, at the lease issuance stage, no activities beyond certain ancillary activities (e.g., 

geological and geophysical operations, data collection, and geotechnical evaluations) are actually 

authorized by the lease; therefore, there are few environmental impacts reasonably expected from 

the lease sale itself. Nonetheless, BOEM has chosen in its discretion to prepare an EIS at this stage

to analyze the potential environmental impacts that could result if exploration, development, 

production, and decommissioning activities eventually occur, in order to provide the context and 

setting of future proposed actions and to better understand the potential impacts associated with 

these types of activities as well as cumulative impacts on GOM resources.

The 2017-2022 GOM Multisale EIS analyzes GOM lease sales included in the Five-Year 

Program’s schedule of proposed lease sales, and its relationship (tiering and supplementing) and 

timing with its respective proposed actions (lease sales) are illustrated in Figure 1-3 below. BOEM 

plans to prepare supplemental EISs on a calendar-year basis as illustrated in Figure 1-3. 

Respective NEPA documents will be completed before decisions are made on the subsequent lease 

sales. This Supplemental EIS is the first of these yearly supplements and will be used to make a 

decision for lease sales proposed for 2018. The analyses in this Supplemental EIS may be applied 

and supplemented as necessary to inform decisions for each of the remaining proposed regionwide 

lease sales scheduled in the Five-Year Program. 

Also, as described in the Five-Year Program, any individual lease sale could still be scaled 

back during the prelease sale process to offer a smaller area should circumstances warrant. For 

example, an individual lease sale could offer an area that conforms more closely to the separate 

planning area model used in the 2012-2017 Five-Year Program. Therefore, the analyses in this 

Supplemental EIS also includes alternatives similar to past WPA, CPA, and EPA lease sale 

environmental reviews.
The Proposed Action 1-9 

Figure 1-3. BOEM’s Planned Supplemental Approach Showing the Tiering Relationships for Proposed 

Gulf of Mexico Lease Sales. 

Each planned subsequent Supplemental EIS from the above figure will update the potential 

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

GOM and will update the cumulative impacts from the most recent NEPA analysis, as necessary. 

The baseline conditions in the GOM will be updated to reflect the most recent technical and scientific 

information available. As shown in Figure 1-3, a new Supplemental EIS cycle is currently planned 

to be prepared every calendar year (e.g., 2019, 2020, 2021, and 2022), and a separate decision 

would be made for each of the remaining proposed lease sales in the Five-Year Program. A 

decision on the remaining proposed GOM lease sales in the Five-Year Program will be made based 

on additional NEPA review that may update the previous Supplemental EIS, as necessary. Using 

this approach allows for subsequent NEPA analyses to focus on potential changes in each of the 

proposed lease sales and on any new issues and information that may have become available since 

the publication of the previous NEPA document.

This Supplemental EIS supplements, tiers from, updates, summarizes, and incorporates by 

reference all of the relevant analyses from the Five-Year Program EIS and 2017-2022 GOM 

Multisale EIS, which are referenced below.
1-10 2018 Gulf of Mexico Supplemental EIS

• November 2016 – Outer Continental Shelf Oil and Gas Leasing Program: 

2017-2022—Final Programmatic Environmental Impact Statement (Five-Year 

Program EIS; USDOI, BOEM, 2016b) 

• March 2017 – Gulf of Mexico OCS Oil and Gas Lease Sales: 2017-2022; Gulf of 

Mexico Lease Sales 249, 250, 251, 252, 253, 254, 256, 257, 259, and 261—

Final Multisale Environmental Impact Statement (2017-2022 GOM Multisale EIS; 

USDOI, BOEM, 2017a) 

This Supplemental EIS will

• update the baseline conditions and potential environmental effects of oil and 

natural gas leasing, exploration, development, and production in the GOM since 

publication of the 2017-2022 GOM Multisale EIS;

• analyze the potential impacts of a proposed action on the marine, coastal, and 

human environments;

• assist decisionmakers in making informed, future decisions regarding the 

approval of operations, as well as leasing; and

• focus on the potential environmental effects of oil and natural gas leasing, 

exploration, development, and production in the areas that were identified 

through the Area Identification (Area ID) procedure for the 2017-2022 GOM 

Multisale EIS as the proposed lease sale area. In addition to the No Action 

Alternative (i.e., cancel a proposed lease sale), other alternatives may be 

considered for the proposed lease sale, such as deferring certain areas from a 

proposed lease sale.

1.3.2 Gulf of Mexico Postlease Activities

BOEM and the Bureau of Safety and Environmental Enforcement (BSEE) are responsible for 

managing, regulating, and monitoring oil and natural gas exploration, development, and production 

operations on the OCS to promote the orderly development of mineral resources in a safe and 

environmentally sound manner. BOEM’s regulations for oil, gas, and sulphur lease operations are 

specified in 30 CFR parts 550, 551, 554, and 556. The BSEE’s regulations for oil, gas, and sulphur 

operations are specified in 30 CFR parts 250 and 254. Refer to Appendix A of the 2017-2022 GOM 

Multisale 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 postlease activities; 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.
The Proposed Action 1-11

The decision on whether and 

how to proceed with proposed 

Lease Sale 250 will be made 

following the completion of this 

NEPA analysis. A separate 

decision will be made for Lease 

Sale 251.

All plans for OCS oil- and gas-related activities (e.g., exploration and development plans) go 

through rigorous BOEM review and approval to ensure compliance with established laws and 

regulations before any project-specific activities can begin on a lease. Mitigating measures are

incorporated and documented in plans submitted to BOEM. These measures may be implemented 

through, among other things, lease stipulations and project-specific requirements or conditions of 

approval. Conditions of approval are based on BOEM’s and BSEE’s technical and environmental 

evaluations of the proposed operations. Conditions may be applied to any OCS plan, permit, 

right-of-use and easement, or pipeline right-of-way grant.

Mitigating measures address concerns such as endangered and threatened species, 

geologic and manmade hazards, military warning and ordnance disposal areas, archaeological sites, 

air quality, oil-spill response planning, deepwater benthic communities, artificial reefs, operations in 

hydrogen sulfide (H2S)-prone areas, and shunting of drill effluents in the vicinity of biologically 

sensitive features. Refer to Appendix B of the 2017-2022 GOM Multisale EIS (“Commonly Applied 

Mitigating Measures”) for more information on the mitigations that BOEM and BSEE often apply to 

permits and approvals. Operational compliance of the mitigating measures is enforced through 

BSEE’s onsite inspection program.

BOEM and BSEE issue Notices to Lessees and Operators (NTLs) to provide clarification, 

description, or interpretation of a regulation; guidelines on the implementation of a special lease 

stipulation or regional requirement; or convey administrative information. A detailed listing of the 

current Gulf of Mexico OCS Region’s NTLs is available through BOEM’s Gulf of Mexico OCS 

Region’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. A detailed listing of BSEE’s Gulf of Mexico OCS Region’s current NTLs is 

available through BSEE’s website at https://www.bsee.gov/guidance-and-regulations/guidance/

notice-to-lessees. 

1.4 THE DECISION TO BE MADE

This Supplemental EIS has been prepared to inform 

decisions for the proposed 2018 GOM lease sales. After 

completion of the NEPA process for this Supplemental EIS, a 

decision will be made for proposed Lease Sale 250, which is 

scheduled for March 2018 (i.e., prepare a Record of Decision 

for proposed Lease Sale 250). A second NEPA review will be 

conducted for proposed Lease Sale 251, which is scheduled for 

August 2018, to consider any relevant new information; a 

second Record of Decision will be prepared for proposed 

Lease Sale 251. As discussed in Chapter 1.4.1, individual decisions will be made on each 

subsequent proposed lease sale in the Five-Year Program after completion of the appropriate NEPA 

review and supplementation of the EIS if necessary. 
1-12 2018 Gulf of Mexico Supplemental EIS

1.5 REGULATORY FRAMEWORK

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

process (e.g., NEPA). These regulations are intended to encourage orderly, safe, and 

environmentally responsible development of oil, natural gas, alternative energy sources, and other 

mineral resources on the OCS. BOEM consults with numerous federally recognized Indian Tribes 

and Federal and State departments and agencies that have authority to govern and maintain ocean 

resources pursuant to other Federal laws. For more information on BOEM’s consultation partners 

for specific Federal regulations, specific consultation and coordination processes with federally

recognized Indian Tribes, and Federal, State, and local agencies, refer to Chapter 1.5 of the 

2017-2022 GOM Multisale EIS. In addition, a detailed description of major Federal laws and 

Executive Orders that are relevant to the OCS leasing process is provided in the OCS Regulatory 

Framework white paper, which can be found on BOEM’s website (Cameron and Matthews, 2016).

1.6 OTHER OCS OIL- AND GAS-RELATED ACTIVITIES

BOEM and BSEE have programs and activities that are OCS-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, and regulatory enforcement. BOEM also participates in industry research 

efforts and forums. The information collected through these efforts is used in support of the BOEM

NEPA documents that inform Agency decisions. Chapter 1.6 of the 2017-2022 GOM Multisale EIS 

contains descriptions of the other OCS oil- and gas-related activities, including the Environmental 

Studies Program, Technology Assessment Program, oil-spill response research, and interagency 

agreements.

1.7 OTHER PERTINENT ENVIRONMENTAL REVIEWS OR DOCUMENTATION

BOEM is aware of other environmental reviews and studies relevant to the resources under 

consideration in this Supplemental EIS. Notices of Availibility were published in the Federal Register

for the following reviews: BOEM’s Gulf of Mexico OCS Proposed Geological and Geophysical 

Activities Programmatic Western, Central, and Eastern Planning Areas Draft Programmatic 

Environmental Impact Statement (USDOI, BOEM, 2016c), NOAA’s Flower Garden Banks National 

Marine Sanctuary Expansion Draft Environmental Impact Statement (USDOC, NOAA, ONMS, 

2016), and the Natural Resource Damage Assessment Trustees’ (Trustees) Deepwater Horizon Oil 

Spill: Final Programmatic Damage Assessment and Restoration Plan and Final Programmatic 

Environmental Impact Statement (PDARP/PEIS; Deepwater Horizon Natural Resource Damage 

Assessment Trustees, 2016). For more details on these documents, refer to Chapter 1.7 of the 

2017-2022 GOM Multisale EIS.

In addition, supporting technical information in previous NEPA reviews have been developed 

as standalone technical reports and are summarized and incorporated by reference as appropriate. 

These include the OCS regulatory framework and improvements since the Deepwater Horizon
The Proposed Action 1-13

explosion, oil spill, and response; the catastrophic spill event analysis (USDOI, BOEM, 2017b); and 

the essential fish habitat assessment (USDOI, BOEM, 2016d). Subsequent updates to this 

information have been minimal and, therefore, BOEM has prepared separate technical reports, 

which will be updated as needed. These reports can be found on BOEM’s website at 

http://www.boem.gov/nepaprocess/. This approach is conducive to reducing the size of this 

Supplemental EIS and future NEPA documents.

1.8 FORMAT AND ORGANIZATION OF THIS SUPPLEMENTAL EIS

In an effort to thoroughly explain all the environmental consideration and mitigations that are 

involved in BOEM’s assessment of the potential environmental consequences of OCS oil- and 

gas-related activities, BOEM recognizes that past NEPA reviews have become encyclopedic in 

nature. To more closely align with CEQ’s guidance regarding EIS format, a major goal in preparing 

this Supplemental EIS includes increasing the readability of the document for decisionmakers and 

the public, and shortening the document by providing relevant and appropriate information needed to 

assess the effects of the proposed actions and alternatives. A major focus for preparing this 

Supplemental EIS has been on clear and concise writing, using graphics to emphasize major 

concepts where appropriate, and referencing more detailed and technical supporting information in 

appendices from the 2017-2022 GOM Multisale EIS and incorporating those appendices by 

reference. The remaining chapters in this Supplemental EIS are described below.

• Chapter 2 describes the proposed action, including the potential lease sale 

options and the alternatives, being analyzed in this Supplemental EIS; discusses 

the potential mitigating measures (pre- and postlease), including the proposed 

stipulations, and the issues considered and not considered in the analysis; and 

discusses the deferred alternatives and provides a broad comparison of impacts 

by alternative.

• Chapter 3 describes all the potentially occurring actions associated with a 

proposed regionwide lease sale in the Five-Year Program and the cumulative 

activities that provide a framework for detailed analyses of the potential impacts 

analyzed in Chapter 4. Exploration and development scenarios describe the 

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

and socioeconomic resources in the GOM. It is a hypothetical framework of 

assumptions based on estimated amounts, timing, and general locations of OCS 

exploration, development, and production activities and facilities, both offshore 

and onshore. It also includes a set of ranges for resource estimates, projected 

exploration and development activities, and impact-producing factors. 

• Chapter 4 describes the affected environment and the potential impacts of a 

proposed regionwide lease sale and each alternative by resource. Analysis of 

the alternatives includes routine activities, accidental events, cumulative impact 

analysis, incomplete or unavailable information, and conclusions for each 

resource. 
1-14 2018 Gulf of Mexico Supplemental EIS

• Chapter 5 describes the consultation and coordination efforts used in preparing 

this Supplemental EIS. This includes a description of the scoping process and 

summary of scoping comments, activities, and results; cooperating agencies; 

distribution of the EIS; consultations with Federal and State agencies under the 

Coastal Zone Management Act, Endangered Species Act, the MagnusonStevens Fishery Conservation and Management Act, and the National Historic 

Preservation Act; and government-to-government consultation and coordination.

• Chapter 6 includes all the citations referred to throughout this Supplemental EIS.

• Chapter 7 is a list of all the preparers of this Supplemental EIS.

• Chapter 8 is a glossary of terms.

• Finally, to improve the readability of this Supplemental EIS, more detailed 

supporting information has been placed in the Appendices. 
CHAPTER 2 

 

ALTERNATIVES INCLUDING THE PROPOSED ACTION

Alternatives Including the Proposed Action 2-3 

Agencies are encouraged to tier 

their environmental impact 

statements to eliminate repetitive 

discussions of the same issues 

and to focus on the actual issues 

appropriate for decision at each 

level of environmental review. 

What’s In This Chapter?

• Alternative A: A single proposed regionwide lease sale offering all available unleased 

blocks within the WPA, CPA, and EPA portions of the proposed lease sale area with 

exceptions as outlined in Chapter 2.2.1.

• Alternative B: A single proposed lease sale offering all available unleased blocks within 

the CPA and EPA, but not within the WPA portion of the proposed lease sale area with 

exceptions.

• Alternative C: A single proposed lease sale offering all available unleased blocks within 

the WPA, but not within the CPA/EPA portions of the proposed lease sale area with one 

exception.

• Alternative D: Alternative A, B, or C with the option to exclude any available unleased 

blocks subject to the Topographic Features Stipulation, Live Bottom (Pinnacle Trend) 

Stipulation, and/or Blocks South of Baldwin County, Alabama, Stipulations.

• Alternative E: Cancellation of a single proposed lease sale.

• The pre- and postlease mitigating measures being analyzed are presented. 

• The issues analyzed and those not considered within this Supplemental EIS are presented.

• A comparison of the potential impacts to each resource by alternative is presented.

2 ALTERNATIVES INCLUDING THE PROPOSED ACTION 

2.0 INTRODUCTION

This Supplemental EIS addresses a proposed Federal action – a regionwide lease sale. 

This Supplemental EIS is expected to be used to inform decisions for proposed oil and gas Lease 

Sales 250 and 251 in the Gulf of Mexico OCS (Figure 1-1), as scheduled in the Five-Year Program 

(USDOI, BOEM, 2016a). This Supplemental EIS is expected to be used to inform decisions for each 

of the two proposed lease sales scheduled in 2018 and to be used and supplemented as necessary 

for decisions for each of the remaining proposed regionwide lease sales scheduled in the Five-Year 

Program. This Supplemental EIS contains analyses of the potential environmental impacts that 

could result from a proposed regionwide lease sale in the Gulf of Mexico as scheduled in the 

Five-Year Program, but the analyses may be applied and supplemented as necessary to inform 

decisions for each of the remaining proposed lease sales scheduled in the Five-Year Program. The 

decision on whether and how to proceed with proposed Lease Sale 250 will be made following the 

completion of this NEPA analysis. A separate decision will be made for the second proposed lease 

sale in 2018, i.e., Lease Sale 251. The proposed action (proposed lease sale) assumes compliance 

with applicable regulations and lease stipulations in place at the time a ROD is signed for a 

proposed action. Four action alternatives (Alternatives A-D) and a No Action Alternative 

(Alternative E) are described, including a comparison of 

impacts by alternative.

2.1 SUPPLEMENTAL EIS NEPA ANALYSIS

The planned supplemental approach for regionwide

lease sales is intended to focus the NEPA/EIS process on 

updating subsequent lease sale NEPA reviews as 
2-4 2018 Gulf of Mexico Supplemental EIS

necessary to address any relevant significant new information and/or issues since publication of the 

previous lease sale NEPA documents from which it tiers (Figure 1-6). Since proposed GOM Lease 

Sales 250, 251, 252, 253, 254, 256, 257, 259, and 261 and their projected activities are very similar, 

the impacts from a single proposed regionwide lease sale (e.g., Lease Sale 250) examined in this 

Supplemental EIS may be applied to the remaining proposed GOM lease sales scheduled in the 

Five-Year Program, as authorized under 40 CFR § 1502.4, which allows related or similar proposals 

to be analyzed in one EIS. Proposed Lease Sales 250, 251, 252, 253, 254, 256, 257, 259, and 261

were also considered in the cumulative analysis of the 2017-2022 GOM Multisale EIS. This 

Supplemental EIS tiers from, updates, summarizes, and incorporates by reference the 2017-2022 

GOM Multisale EIS. Proposed GOM Lease Sales 250, 251, 252, 253, 254, 256, 257, 259, and 261

are expected to be within the scenario ranges summarized in Chapter 3 of this Supplemental EIS 

and as discussed in Chapter 3 of the 2017-2022 GOM Multisale EIS.

This Supplemental EIS is expected to be used to inform decisions for the two proposed lease 

sales scheduled in 2018 and to be used and supplemented as necessary for decisions for each of 

the remaining proposed regionwide lease sales scheduled in the Five-Year Program. At the 

completion of the NEPA process for this Supplemental EIS, a decision will be made on whether and 

how to proceed with proposed GOM Lease Sale 250, which is scheduled for March 2018. A second 

NEPA review will be conducted for proposed Lease Sale 251, which is scheduled for August 2018, 

to consider any relevant new information, and a second Record of Decision will be published for 

proposed Lease Sale 251. A new Supplemental EIS cycle is currently planned to be prepared every 

calendar year (e.g., 2019, 2020, 2021, and 2022), and a separate decision would be made for each 

of the remaining proposed lease sales scheduled in the Five-Year Program. Informal and formal 

consultation with other Federal agencies, the affected States, federally recognized Indian Tribes, 

nongovernmental organizations, and the public is being conducted as appropriate to integrate to the 

fullest extent possible environmental impact analyses with other environmental review laws and 

Executive Orders.

2.2 ALTERNATIVES, MITIGATING MEASURES, AND ISSUES

Through the scoping efforts for this Supplemental EIS and the prior 2017-2022 GOM 

Multisale EIS, numerous issues and topics were identified for consideration. During the scoping 

period for the prior 2017-2022 Multisale EIS, a number of alternatives or deferral options were 

suggested and examined for inclusion in Chapter 2.2.2 of the 2017-2022 GOM Multisale EIS. 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 2017-2022 GOM Multisale EIS 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 2012-2017 GOM Multisale EIS.
Alternatives Including the Proposed Action 2-5 

The analyses of environmental impacts from the proposed alternatives summarized below 

and described in detail in Chapter 4 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 What are the Alternatives that BOEM is Considering for Each Proposed 

Lease Sale?

The discussions below outline the alternatives that are considered for this environmental

analysis. All available unleased blocks within the WPA, CPA, and EPA portions of the proposed 

lease sale area, with the exceptions as outlined for each alternative below, are being offered for 

lease. The mitigating measures (pre- and postlease), including the proposed stipulations, are fully 

described in Chapter 2 and Appendix D of the 2017-2022 GOM Multisale EIS.

2.2.1.1 Alternative A—Regionwide OCS Lease Sale (The Preferred Alternative) 

Alternative A would allow for a proposed regionwide lease sale encompassing all three 

planning areas within the U.S. portion of the Gulf of Mexico OCS. This is BOEM’s preferred 

alternative. This alternative would offer for lease all available unleased blocks within the WPA, CPA, 

and EPA portions of the proposed 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 (discussed in the OCS Regulatory Framework white paper [Cameron 

and Matthews, 2016]); 

(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; and

(3) whole and partial blocks within the current boundary of the Flower Garden 

Banks National Marine Sanctuary.
2-6 2018 Gulf of Mexico Supplemental EIS

Figure 2-1. Proposed Regionwide Lease Sale Area, Encompassing the Available Unleased Blocks 

within All Three Planning Areas (a total of approximately 91.93 million acres with 

approximately 75.7 million acres available for lease as of February 2017).

A proposed regionwide lease sale would include all three BOEM planning areas 

encompassing a total of approximately 91.93 million acres with approximately 75.7 million acres 

available for lease as of February 2017. Leasing information related to all three planning areas is 

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

In general, a regionwide lease sale would represent 1.2-4.2 percent of the total OCS 

Program production in the GOM based on barrels of oil equivalent resource estimates (refer to 

Chapter 3.1.2). The estimated amounts of resources projected to be leased, discovered, 

developed, and produced as a result of a typical proposed regionwide lease sale are 

0.211-1.118 billion barrels of oil (BBO) and 0.547-4.424 trillion cubic feet (Tcf) of gas (refer to

Table 3-5). 
Alternatives Including the Proposed Action 2-7 

2.2.1.2 Alternative B—Regionwide OCS Lease Sale Excluding Available Unleased Blocks in 

the WPA Portion of the Proposed Lease Sale Area

Alternative B would allow for a proposed lease sale encompassing the CPA and EPA within 

the U.S. portion of the Gulf of Mexico OCS (Figure 2-2). Available blocks within the WPA would not

be considered under this alternative. This alternative would offer for lease all available unleased 

blocks within the CPA and EPA portions of the proposed lease sale area for oil and gas operations, 

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. 

 

Figure 2-2. Proposed Lease Sale Area for Alternative B, Excluding the Available Unleased Blocks in 

the WPA (a total of approximately 63.35 million acres with approximately 49.8 million acres

available for lease as of February 2017).

In general, a lease sale that would include all available unleased blocks in the CPA and EPA 

would represent approximately 1.0-3.6 percent of the total OCS Program production in the GOM 
2-8 2018 Gulf of Mexico Supplemental EIS

based on barrels of oil equivalent resource estimates (refer to Table 3-2). The estimated amounts of 

resources projected to be leased, discovered, developed, and produced as a result of a proposed 

lease sale under Alternative B are 0.185-0.970 BBO and 0.441-3.672 Tcf of gas (refer to Table 3-5).

2.2.1.3 Alternative C—Regionwide OCS Lease Sale Excluding Available Unleased Blocks in 

the CPA/EPA Portions of the Proposed Lease Sale Area

Alternative C would allow for a proposed lease sale encompassing the WPA within the U.S. 

portion of the Gulf of Mexico OCS (Figure 2-3). Available blocks within the CPA and EPA would not

be considered under this alternative. This alternative would offer for lease all available unleased

blocks within the WPA portion of the proposed lease sale area for oil and gas operations, with the 

following exception: 

(1) whole and partial blocks within the current boundary of the Flower Garden Banks 

National Marine Sanctuary.

The proposed Alternative C lease sale area encompasses virtually all of the WPA’s 

approximately 28.58 million acres as that planning area is described as a subset of Alternative A. In 

general, a lease sale that would include all available unleased blocks in the WPA would represent 

approximately 0.2-0.6 percent of the total OCS Program production in the GOM based on barrels of 

oil equivalent resource estimates (refer to Table 3-2). The estimated amounts of resources 

projected to be leased, discovered, developed, and produced as a result of a proposed lease sale 

offering only WPA available blocks are 0.026-0.148 BBO and 0.106-0.752 Tcf of gas (refer to 

Table 3-5).
Alternatives Including the Proposed Action 2-9 

 

Figure 2-3. Proposed Lease Sale Area for Alternative C, Excluding the Available Unleased Blocks in 

the CPA and EPA (a total of approximately 28.58 million acres with approximately 

25.9 million acres available for lease as of February 2017).

2.2.1.4 Alternative D—Alternative A, B, or C, with the Option to Exclude Available Unleased 

Blocks Subject to the Topographic Features, Live Bottom (Pinnacle Trend), and/or 

Blocks South of Baldwin County, Alabama, Stipulations

Alternative D could be combined with any of the action alternatives above (i.e., Alternatives 

A, B, or C) and would allow the flexibility to offer leases under any alternative with additional 

exclusions. Under Alternative D, the decisionmaker could exclude from leasing any available 

unleased blocks subject to any one and/or a combination of the following stipulations:

− Topographic Features Stipulation; 

− Live Bottom (Pinnacle Trend) Stipulation; and 

− Blocks South of Baldwin County, Alabama, Stipulation (not applicable to 

Alternative C). 

This alternative considered blocks subject to these stipulations because these areas have 

been emphasized in scoping, can be geographically defined, and adequate information exists 
2-10 2018 Gulf of Mexico Supplemental EIS

regarding their ecological importance and sensitivity to OCS oil- and gas-related activities. 

Figure 2-5 of the 2017-2022 GOM Multisale EIS illustrates one example of the blocks that could be 

excluded under this alternative (shaded in blue).

A total of 207 blocks within the CPA and 160 blocks in the WPA are affected by the 

Topographic Features Stipulation (Figure 2-4). There are currently no identified topographic 

features protected under this stipulation in the EPA. The Live Bottom Stipulation covers the pinnacle 

trend area of the CPA, affecting a total of 74 blocks (Figure 2-4). More details on the blocks 

affected by the Topographic Features Stipulation and the Pinnacle Trend blocks subject to the Live 

Bottom Stipulation can be found at http://www.boem.gov/Biologically-Sensitive-Areas-List/. Maps 

indicating the areas affected by the Topographic Features Stipulation can be found at 

http://www.boem.gov/Topographic-Features-Stipulation-Map-Package/. 

 

Figure 2-4. Identified Topographic Features, Pinnacle Trend, and Blocks South of Baldwin County, 

Alabama, Stipulation Blocks in the Gulf of Mexico.

As of the publication of this Supplemental EIS, the Blocks South of Baldwin County, 

Alabama, Stipulation (herein referred to as the Baldwin County Stipulation Blocks) applies to a total 
Alternatives Including the Proposed Action 2-11

of 32 blocks (Mobile Blocks 826-830, 869-874, 913-918, 957-962, 1001-1006, and Viosca Knoll 

Blocks 33-35) within 15 mi (24 km) of Baldwin County, Alabama (representing less than 1% of the 

total number of blocks to be offered under Alternative A or B). The intent of a proposal excluding 

these blocks would be to mitigate the visual impacts of concern raised by the Governor of Alabama 

on previous EISs, as well as in the 2017-2022 Five-Year Program from which the 2017-2022 GOM 

Multisale EIS and this Supplemental EIS tier. The stipulation, however, has been continually 

adopted in annual CPA lease sales since 1999 and has effectively mitigated visual impact. The 

stipulation specifies requirements for consultation that lessees must follow when developing plans 

for fixed structures (refer to Appendix D of the 2017-2022 GOM Multisale EIS) while still allowing 

leasing and OCS oil- and gas-related operations in the area, which could not occur with the 

no-leasing buffer. If any of the action alternatives are selected, BOEM expects this stipulation to be 

analyzed and decided on at the lease sale stage; therefore, visual impacts would be reduced to the 

greatest extent practicable should the stipulation be applied.

Alternative D, 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 could be conducted within the blocks. 

Under Alternative D, the number of blocks that would become unavailable for lease represents only 

a small percentage of the total number of blocks to be offered under Alternative A, B, or C (<4%, 

even if blocks subject to all three stipulations were excluded). Therefore, Alternative D could reduce 

offshore infrastructure and activities, but Alternative D may (and BOEM believes more reasonable to 

expect) only delay activity or shift the location of offshore infrastructure and activities farther from 

these sensitive zones and not lead to a reduction in overall offshore infrastructure and activities. 

The regional impact levels for all resources, except for the topographic features and live bottoms, 

would be similar to those described under Alternative A, B, or C. All of the assumptions (including 

the proposed stipulations and other potential mitigating measures designed to reduce environmental 

risk) and estimates would remain the same as described for Alternatives A, B, or C. The exclusion 

of this small subset of available unleased blocks could reduce exploration, development, and 

production flexibility and, therefore, could result in adverse economic effects (e.g., reduced 

royalties). A detailed discussion of the development scenario and related impact-producing factors 

is included in Chapter 3. 

2.2.1.5 Alternative E—No Action

Alternative E is the cancellation of a single proposed GOM lease sale within the Five-Year 

Program. The opportunity for development of the estimated oil and gas that could have resulted 

from a proposed action (i.e., a single proposed lease sale) or alternative to the proposed action, as 

described above, would be precluded or postponed to a future lease sale. Any potential 

environmental impacts resulting from a proposed lease sale would not occur. Activities related to 

previously issued leases and permits (as well as those that may be issued in the future under a 

separate decision) related to the OCS oil and gas program would continue. If a lease sale were to

be cancelled, the resulting development of oil and gas would most likely be postponed to a future 

lease sale; therefore, the overall level of OCS oil- and gas-related activity would only be reduced by 
2-12 2018 Gulf of Mexico Supplemental EIS

a small percentage, if any. Therefore, the cancellation of a proposed lease sale would not 

significantly change the environmental impacts of overall OCS oil- and gas-related activity. 

However, the cancellation of a proposed lease sale may result in direct economic impacts to the 

individual companies and revenues collected by the Federal Government (and thus revenue 

disbursements to the States) could also be adversely affected. If future lease sales were to occur, 

the impacts from the cancellation of a single lease sale to individual companies and Federal 

revenues would likely be minor. The Five-Year Program EIS discusses the impacts of cancelling all 

proposed GOM lease sales included in the Five-Year Program.

2.2.2 What Other Alternatives and Deferrals Has BOEM Considered But Not 

Analyzed in Detail?

Chapter 2.2.3 of the 2017-2022 GOM Multisale EIS includes a detailed description of 

alternatives previously considered but not analyzed in detail in this Supplemental EIS, including the 

following: 

• previous multisale approach, which consisted of a total of 12 proposed lease 

sales, including 5 annual proposed lease sales in the WPA, 5 annual proposed 

lease sales in the CPA, and 2 proposed lease sales in the EPA. 

• exclude blocks subject to Flower Garden Banks National Marine Sanctuary 

expansion; 

• additional buffer zones around potential areas of concern (e.g., the blocks 

subject to Congressional moratorium pursuant to the Gulf of Mexico Energy 

Security Act of 2006 and the Gulf Islands National Seashore);

• proposed lease sale offering only available unleased blocks in the EPA;

• proposed lease sale with additional mitigating measures for sperm whale 

high-use areas; 

• regionwide OCS proposed lease sale excluding blocks within the De Soto 

Canyon area;

• regionwide OCS proposed lease sale excluding blocks within loggerhead sea 

turtle critical habitat; and

• delay leasing until the state of the Gulf of Mexico’s environmental baseline since 

the Deepwater Horizon explosion, oil spill, and response is better understood.

The justifications for not engaging in detailed analysis of these alternatives and deferrals is 

provided in the 2017-2022 GOM Multisale EIS, and BOEM has identified no new information that 

changes these conclusions.
Alternatives Including the Proposed Action 2-13

Mitigating measures 

considered in this NEPA 

document rely primarily on 

avoiding an impact altogether 

by not allowing certain actions 

or parts of an action.

Two additional alternatives were identified during scoping for this Supplemental EIS. They 

are listed below:

• stop issuing leases for oil and gas in the Gulf of Mexico; and

• use renewable energy in place of oil and gas.

Both of those issues were addressed in the Five-Year Program EIS, and because this 

Supplemental EIS tiers from the Five-Year Program EIS, the analyses are incorporated by reference 

into this Supplemental EIS. As a result, the full analyses of these alternatives will not be addressed 

in this Supplemental EIS. A brief summary of the alternative analyses is presented below.

BOEM has addressed the alternative to stop issuing leases in the Gulf of Mexico in 

Chapters 2.4, “Reduced Proposed Action (Alternative C),” and 2.5, “No Action (Alternative D)” of the 

Five-Year Program EIS. These alternatives evaluated the environmental effects of having reduced 

areas of leasing or no new lease sales during the 2017-2022 Five-Year Program. The impacts of 

these alternatives are discussed in Chapters 4.4.3.4 “C(4): Exclusion of the Gulf of Mexico Program 

Area” and 4.4.4 “Alternative D – The No Action Alternative” of the Five-Year Program EIS. However, 

it should be noted that oil -and gas-related activities stemming from previous programs would 

continue, and only activity resulting from proposed lease sales in the new Five-Year Program would 

be halted. 

BOEM has addressed the potential for alternative energy on the OCS in Chapters 1.4.6.1 

(“Renewable Energy”) and 2.7.4 (“Develop Alternative or Renewable Energy Sources as a Complete 

or Partial Substitute for Oil and Gas Leasing on the OCS”) of the Five-Year Program EIS. However, 

BOEM determined that an analysis of the potential for alternative energy is outside the scope of this 

Supplemental EIS for a proposed action. The purpose and need identified for this Supplemental EIS 

is to provide an analysis of the environmental impacts of oil and gas leasing. BOEM's Office of 

Renewable Energy is responsible for developing an offshore renewable energy program in the Gulf 

of Mexico. Information on BOEM’s Renewable Energy Program, OCS leases, and renewable 

energy projects is available on BOEM’s website at http://www.boem.gov/Renewable-Energy/. 

2.2.3 What Types of Mitigating Measures Does BOEM Apply?

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.
2-14 2018 Gulf of Mexico Supplemental EIS

• Restoration—Rectifying the impact by repairing, rehabilitating, or restoring the 

affected environment.

• 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.

BOEM considers the use of mitigation at all phases of energy development and planning, 

from the overarching Five-Year Program EIS, through each of the NEPA documents for the lease 

sales, and followed by more site-specific reviews for exploration, development and production, and 

decommissioning plans (Figure 1-3). Mitigations can be applied at the prelease stage, typically 

through applying lease stipulations or at the postlease stage by applying site-specific mitigating 

measures to plans, permits, and/or authorizations (refer to Appendix A of the 2017-2022 GOM 

Multisale EIS). Through this approach, BOEM is able to analyze impacts and mitigations that are 

appropriate for consideration at the appropriate time.

2.2.3.1 Proposed Lease Mitigating Measures (Stipulations)

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. The 10 lease stipulations being considered are as follows: 

• 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

• Stipulation on the Agreement Between the United States of America and the 

United Mexican States Concerning Transboundary Hydrocarbon Reservoirs in 

the Gulf of Mexico (Transboundary Stipulation).

These mitigating measures would be considered for adoption by the decisionmaker, as 

applicable, under authority delegated by the Secretary of the Interior. The Topographic Features 

and Live Bottom (Pinnacle Trend) Stipulations have been applied as programmatic mitigation in the 
Alternatives Including the Proposed Action 2-15

Five-Year Program EIS (USDOI, BOEM, 2016b) and, therefore, would apply to all leases issued 

under the Five-Year Program in the designated lease blocks. The analysis of the other eight

stipulations for any particular alternative does not ensure application of the stipulations to leases that 

may result from any proposed 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 stipulations or mitigation requirements to be included in a lease sale will be described in 

the Record of Decision 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 related to leases issued as a 

result of a lease sale, will undergo a NEPA review, and additional project-specific mitigations applied 

as conditions of plan approval at the postlease stage. The BSEE has the authority to monitor and 

enforce these conditions under 30 CFR part 250 subpart N and may seek remedies and penalties 

from any operator that fails to comply with those conditions, stipulations, and mitigating measures.

2.2.3.2 Prelease Mitigating Measures (Stipulations) by Alternative

Table 2-1 indicates what stipulations could be applied for each alternative. Alternative D 

would consider the same stipulations as Alternative A, B, or C, as applicable, with the exception of 

removing the Topographic Features and Live Bottoms (Pinnacle Trend) Stipulations since all blocks 

subject to these stipulations would not be made available. Since Alternative E is the cancellation of 

a proposed lease sale, no stipulations would apply.

Table 2-1. Applicable Stipulations by Alternative.

Stipulation Alternative A Alternative B Alternative C Alternative D Alternative E1

Topographic 

Features X2 X X –3 – 

Live Bottoms X X – – – 

Military Areas X X X X – 

Evacuation X X – See A, B, or C –

Coordination X X – See A, B, or C – 

Blocks South of 

Baldwin County, 

Alabama

X X – See A, B, or C – 

Protected Species X X X X – 

United Nations 

Convention on the 

Law of the Sea 

Royalty Payment

X X X X – 

Below Seabed 

Operations X X – See A, B, or C – 

Transboundary X X X X – 
2-16 2018 Gulf of Mexico Supplemental EIS

Mitigating measures are a 

standard part of BOEM’s program 

to ensure that operations are 

always conducted in an 

environmentally sound manner.

Stipulation Alternative A Alternative B Alternative C Alternative D Alternative E1

1 Alternative E would cancel a proposed lease sale and no leasing activities would occur; therefore, no 

stipulations would apply. 2 Stipulations that would apply to specific lease blocks under any given alternative are marked with an X.

3 Stipulations that would not apply are marked “–”.

2.2.3.3 Postlease Mitigating Measures

Postlease mitigating measures have been 

implemented for over 40 years in the Gulf of Mexico region, 

as they relate to OCS plans and pipeline applications. 

Following a lease sale, an applicant seeks approvals to 

develop their lease by preparing and submitting OCS 

plans. The OCS plans are reviewed by BOEM and, 

depending on what is proposed to take place in a specific 

place, plans may be denied, approved, or approved with conditions of approval (COA). The COAs 

become part of the approved postlease authorization and include environmental protections, 

requirements that maintain conformance with law, the requirements of other agencies having 

jurisdiction, or safety precautions. Mitigating measures are an integral part of BOEM’s program to 

ensure that operations are conducted in an environmentally sound manner (with an emphasis on 

avoiding or 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 and avoidance of archaeological sites and biologically 

sensitive areas such as pinnacles, topographic features, and chemosynthetic communities.

BOEM analyzes impacts on a finer geographic scale than that analyzed in the 2017-2022 

GOM Multisale EIS and this Supplemental EIS through site-specific environmental reviews, and 

applies mitigations as conditions of approval to permits, as appropriate. Appendix A of the 

2017-2022 GOM Multisale EIS discusses BOEM’s rigorous postlease processes and Appendix B of 

the 2017-2022 GOM Multisale EIS describes over 120 standard mitigations that may be required by 

BOEM or BSEE as a result of plan and permit review processes for the Gulf of Mexico OCS Region.

Mitigating measures have been proposed, identified, evaluated, or developed through 

previous BOEM lease sale and site-specific NEPA reviews and analyses. For example, certain 

measures ensure site clearance, and survey procedures are carried out to determine potential snags 

to commercial fishing and avoidance of archaeological sites and biologically sensitive areas such as 

pinnacles, topographic features, and deepwater benthic communities. Many of these mitigating 

measures have been adopted and incorporated into regulations and/or as guidelines governing OCS 

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.
Alternatives Including the Proposed Action 2-17

Some BOEM-identified mitigating measures are incorporated into OCS oil- and gas-related 

operations through cooperative agreements or efforts with industry and State and Federal agencies. 

These mitigating measures include the National Marine Fisheries Service’s (NMFS) Observer 

Program to protect marine mammals and sea turtles during explosive removals, labeling operational 

supplies to track possible sources of debris or equipment loss, development of methods of pipeline 

landfall to eliminate impacts to beaches or wetlands, and 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 

commonly applied “standard” mitigations. There are currently over 120 standard mitigations that 

could be applied by BOEM during plan and permit reviews. 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). Categories of site-specific mitigations 

include the following: air quality; archaeological resources; artificial reef material; deepwater benthic 

communities; Flower Garden Banks; topographic features; hard bottoms/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 the following: advisories; conditions of approval; 

hazard survey reviews; inspection requirements; notifications; post-approval submittals; and safety 

precautions. In addition to standard mitigations, BOEM may also apply nonrecurring mitigating 

measures that are developed on a case-by-case basis. Refer to Appendix B of the 2017-2022 GOM 

Multisale EIS (“Commonly Applied Mitigating Measures”) 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).

2.2.4 What are the Primary Topics and Resources Being Evaluated?

Issues are defined by CEQ to represent those principal “effects” that an EIS should evaluate 

in-depth. Scoping identifies specific environmental resources and/or activities rather than “causes” 

as significant issues (Council on Environmental Quality, 1981). The analysis in the EIS can then 

show the degree of change from the present conditions for each issue to the actions arising from the 

proposed action.
2-18 2018 Gulf of Mexico Supplemental EIS

Selection of environmental and socioeconomic issues to be analyzed was based on the

following criteria:

• 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

• information that indicates a need to evaluate the potential impacts to a 

resource/activity has become available.

2.2.4.1 Issues to be Analyzed

Chapter 2.2.5.1 of the 2017-2022 GOM 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-related activities, including accidental events, 

drilling fluids and cuttings, visual and aesthetic interference, air emissions, water quality degradation, 

other wastes, structure and pipeline emplacement, platform removals, OCS oil- and gas-related 

support services, activities, and infrastructure, sociocultural and socioeconomic, geological and 

geophysical activities, and other issues. Chapter 4 of this Supplemental EIS and Chapter 4 of the 

2017-2022 GOM Multisale EIS describe the resources and activities that could be affected by the 

impact-producing factors listed above and include the following resource topics:

− Air Quality

− Water Quality (Coastal and Offshore)

− Coastal Habitats (Estuarine Systems and 

Coastal Barrier Beaches and Associated 

Dunes)

− Deepwater Benthic Communities 

(Chemosynthetic and Deepwater Coral) 

− Sargassum and Associated Communities

− Live Bottom Habitats (Topographic 

Features, Pinnacles, and Low-Relief

Features)

− Fishes and Invertebrate Resources

− Birds

− Protected Species (ESA-Listed Marine 

Mammals, Sea Turtles, Beach Mice, 

Protected Birds, and Protected Corals) 

− Commercial Fisheries

− Recreational Fishing

− Recreational Resources

− Archaeological Resources (Historic and 

Prehistoric)

− Human Resources and Land Use 

(Land Use and Coastal Infrastructure, 

Economic Factors, and Social Factors, 

Including Environmental Justice)

2.2.4.2 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 
Alternatives Including the Proposed Action 2-19

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 have been covered by prior environmental review.

Comments received during scoping are summarized in Chapter 5.6.2.2. Many of those 

issues were analyzed in detail in the 2017-2022 GOM Multisale EIS and summarized and/or updated 

as needed in this Supplemental EIS. These issues include the following: 

• cumulative impacts to coastal resources, including wetlands; 

• compensatory mitigation;

• updates and safety improvements implemented by regulators and industry;

• downstream and lifecycle greenhouse gas emissions from lease sales;

• well-stimulation activities and associated environmental impacts; 

• climate change on GOM environmental resources, including warmer oceans, 

increased storms and flood events, and land loss;

• economic impacts as a result of canceling or holding a proposed lease sale;

• substitution effects of renewable energy sources in place;

• oil and chemical spills, including continued effects from past spills and leaking 

wells and pipelines; and

• environmental justice concerns related to those living near petrochemical 

facilities.

2.3 COMPARISON OF IMPACTS BY ALTERNATIVE

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

associated with a proposed action and a proposed action’s incremental contribution to the 

cumulative impacts are described in the individual resource discussions in Chapter 4 of the 

2017-2022 GOM Multisale EIS and summarized in Chapter 4 of this Supplemental EIS. Table 2-2

provides a comparison of expected impact levels by alternative and is derived from the analysis of 

each resource in Chapter 4. The findings for Alternatives A-E represent the incremental contribution

of a proposed lease sale to the cumulative impacts from past, present, and future activities in the 

GOM. These activities include both OCS oil- and gas-related and non-OCS oil- and gas-related 

activities that would be expected regardless of whether or not a lease sale were to occur. The 

impact-level ratings have been specifically tailored and defined for each resource within the 

Chapter 4 impact analysis. Cumulative impacts of current, past, and reasonably foreseeable future 

activities would continue to occur under Alternative E. 
2-20 2018 Gulf of Mexico Supplemental EIS

Table 2-2. Alternative Comparison Matrix.

Impact Level Key1

Beneficial2 Negligible Minor Moderate Major

Alternative

Resource A B C D E

Air Quality Minor Minor Minor Minor None

Water Quality Negligible Negligible Negligible Negligible None

Coastal Habitats

Estuarine Systems Moderate Moderate Minor Moderate Negligible

Coastal Barrier Beaches 

and Associated Dunes Minor Minor Negligible to Negligible to Negligible Minor Minor

Deepwater Benthic 

Communities Negligible Negligible Negligible Negligible None

Sargassum and 

Associated Communities Negligible Negligible Negligible Negligible None

Live Bottoms

Topographic Features Negligible Negligible Negligible Negligible None

Pinnacles and 

Low-Relief Features

Negligible to Negligible to Negligible Negligible None

Minor Minor

Fishes and Invertebrate 

Resources Minor Minor Minor Minor None

Birds Moderate Moderate Moderate Moderate None

Protected Species

Marine Mammals Negligible Negligible Negligible Negligible None

Sea Turtles Negligible Negligible Negligible Negligible None

Beach Mice Negligible Negligible Negligible Negligible None

Protected Birds Negligible Negligible Negligible Negligible None

Protected Corals Negligible Negligible Negligible Negligible None

Commercial Fisheries Beneficial to Beneficial to Beneficial to Beneficial to Negligible Minor Minor Minor Minor

Recreational Fishing Beneficial to Beneficial to Beneficial to Beneficial to Negligible Minor Minor Minor Minor

Recreational Resources Beneficial to Beneficial to Beneficial to Beneficial to Negligible Minor Minor Minor Minor

Archaeological Resources Negligible3 Negligible3 Negligible3 Negligible3 None

Human Resources and 

Land Use

Land Use and Coastal 

Infrastructure

Economic Factors

Minor Minor Minor Minor None

Beneficial to Beneficial to Beneficial to Beneficial to Negligible to

Minor Minor Minor Minor Minor

Social Factors 

(including 

Environmental Justice)

Minor Minor Minor Minor None
Alternatives Including the Proposed Action 2-21

Impact Level Key1

Beneficial2 Negligible Minor Moderate Major

Alternative

Resource A B C D E

Note: Some resources have a range for the impact levels to account for certain variables such as the 

uncertainty of non-OCS oil- or gas-related activities, the level and magnitude of potential 

accidental events, and the minimization of the OCS oil- or gas-related impacts through lease 

stipulations, mitigations, and/or regulations. The impact level ratings have been specifically 

tailored and defined for each resource within the Chapter 4 impact analysis.

1 The findings for Alternatives A-D are the incremental contribution of a proposed action added to what 

would be expected to occur under the No Action Alternative (i.e., no lease sale). Therefore, each 

impact determination under Alternatives A-D assumes that the conditions and impacts (i.e., past, 

present, and future activities as a result of past lease sales) under the No Action Alternative would still 

be present.

2 The level of beneficial impacts is specified in the analysis, which could range from low, medium, or 

high.

3 The level of impacts for archaeological resources ranges between negligible to major and is dependent 

upon whether a survey is performed, mitigation is imposed, mitigation is followed, or a site is identified 

prior to the activity.

2.4 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 2017-2022 GOM Multisale EIS 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.

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 2017-2022 GOM Multisale EIS that is relevant to potential impacts from a 

proposed lease sale. Therefore, the analyses and potential impacts for the resources remain the 

same as those that were presented in the 2017-2022 GOM Multisale EIS. These impact conclusions 

are presented in Chapter 4 of this Supplemental EIS. The analyses and potential impacts detailed 

in that NEPA document remains valid and, as such, apply for the remaining proposed regionwide 

GOM lease sales scheduled in the Five-Year Program. 

In accordance with CEQ guidelines to provide decisionmakers with a robust environmental 

analysis, the Catastrophic Spill Event Analysis white paper (USDOI, BOEM, 2017b) provides an 

analysis of the potential impacts of a low-probability catastrophic oil spill, which is not part of a 

proposed action and not likely expected to occur, to the environmental and cultural resources and 

the socioeconomic conditions analyzed in Chapter 4. In addition, a low-probability catastrophic oil 

spill is analyzed in the Five-Year Program EIS, from which this Supplemental EIS tiers.

CHAPTER 3 

 

IMPACT-PRODUCING FACTORS AND SCENARIO

Impact-Producing Factors and Scenario 3-3 

What’s in This Chapter?

BOEM develops scenarios that describe projected OCS oil- and gas-related routine 

activities and accidental events from a single proposed lease sale, the projected OCS oil and 

gas cumulative activities of multiple lease sales, and the non-OCS oil- and gas-related 

activities and/or events.

• Routine activities for a single proposed lease sale include the following:

− exploration and delineation (geological and geophysical surveys, and drilling 

exploration and delineation wells);

− offshore development and production (drilling production wells, infrastructure 

emplacement, and work-overs and abandonment of wells); and

− decommissioning and removal operations (the removal and/or abandonment of 

platforms and pipelines).

• Accidental events for a single proposed lease sale could include the following: 

− releases into the environment (e.g., oil spills, loss of well control, accidental air 

emissions, pipeline failures, and chemical and drilling fluid spills); 

− collisions (e.g., helicopter, service vessels, and platforms); and

− spill-response activities.

• Cumulative activities include the following:

− Cumulative OCS Oil and Gas Program (all activities, i.e., the routine activities 

and the accidental events that could occur, from past, proposed, and future 

lease sales); and

− non-OCS oil- and gas-related activities (impact-producing factors from the 

broad range of other activities taking place within the proposed lease sale 

area).

3 IMPACT-PRODUCING FACTORS AND SCENARIO

3.0 INTRODUCTION

Chapters 3.1 and 3.2 of the 2017-2022 GOM Multisale EIS describe in detail the routine and 

accidental impact-producing factors and activity scenarios associated with Alternatives A, B, C, 

and D that could potentially affect the biological, physical, and socioeconomic resources of the Gulf 

of Mexico. Chapter 3.3 of the 2017-2022 GOM Multisale EIS describes in detail the cumulative 

impact-producing factors and activity scenarios resulting from past and future lease sales that are 

relevant to Alternatives A, B, C, and D. The following information is a summary of the impactproducing factors and scenario incorporated from the 2017-2022 GOM Multisale EIS.

What is an Impact-Producing Factor?

An impact producing factor is an activity or process, as a result of a proposed lease sale, that 

could cause impacts on the environmental or socioeconomic setting. The impact analyses 

determine the context and intensity of effects caused by any source on environmental resources 

(Chapter 4) including OCS oil- and gas-related activity and other ecological, economic, or social 

effects. Each phase of oil- and gas-related operation has a set of impact-producing factors that may 

affect physical or environmental conditions and/or may affect one or more natural, cultural, or 

socioeconomic resources.
3-4 2018 Gulf of Mexico Supplemental EIS

How are the Impact-Producing Factors Categorized? 

Routine Activities. These activities generally occur on a regular basis during 

the lifetime of a lease. The operations are broken down by phase and include

exploration, development, oil or gas production and transport, and 

decommissioning. Routine operations are evaluated over the 50-year analysis 

period. Routine operations are discussed in Chapter 3.1.

Accidental Events. As a consequence of routine activities, the potential for 

accidental releases exists. Types of accidental events include releases into 

the environment (e.g., oil spills, loss of well control, accidental air emissions, 

pipeline failures, and chemical and drilling fluid spills), collisions (e.g., 

helicopter, service vessels, and platforms) and spill-response activities. 

Reasonably foreseeable accidental events are discussed in Chapter 3.2. 

Cumulative Impacts. The impact-producing factors considered in this chapter 

are defined as other past, present, and reasonably foreseeable future activities 

occurring within the same geographic range and within the same timeframes 

as the aforementioned projected routine activities and potential accidental 

events, including the Cumulative OCS Oil and Gas Program (2017-2086). 

Cumulative activities are discussed in Chapter 3.3. 

3.1 ROUTINE ACTIVITIES

3.1.1 What Activities Routinely Occur as a Result of a Single 

Lease Sale?

The OCS oil and gas operations on a lease generally occur in four 

phases: (1) exploration to locate viable oil or natural gas deposits; 

(2) development well drilling, platform construction, and pipeline infrastructure; (3) operation (oil or 

gas production and transport); and (4) decommissioning of facilities once a reservoir is no longer 

productive or profitable. These phases are illustrated in Figure 3-1, which also illustrates that 

geological and geophysical (G&G) activities can occur during all four phases. Under a proposed 

action, activities would occur on OCS leases only after a lease sale is held. Although unusual cases 

exist where activity on a lease may continue beyond 50 years, our forecasts indicate that the 

significant activities associated with exploration, development, production, and abandonment of 

leases in the GOM occur well within the 50-year analysis period of a single lease sale. For each 

lease sale analyzed within the 50-year analysis period, all activities would be concluded by the 

44th year.
Impact-Producing Factors and Scenario 3-5 

What is a shallow hazard? Buried 

channels up to 4,000 ft (1,219 m) below 

the seafloor filled with permeable 

sediment present hazards to drilling 

operations. Drilling through these 

channels may result in water flowing up 

and around the well casing and may 

deposit sand or silt on the seafloor within 

a few hundred feet of the wellhead and 

could result in hydrate formation if gas is 

present. Unanticipated shallow hazards 

can lead to downhole pressure kicks that 

range from minor and controllable to 

significant and uncontrollable, and up to 

and including a serious blowout condition. 

Figure 3-1. Phases of OCS Activity Resulting from a Single Proposed Lease Sale over 

50 Years.

3.1.1.1 Exploration and Delineation

Geological and Geophysical

The G&G surveys conducted as a result of a 

lease sale typically collect data on surficial or nearsurface geology used to identify on-lease potential 

shallow hazards for engineering and site planning for 

bottom-founded structures. Geological and 

geophysical processes and regulations are discussed 

in greater detail in Appendix A.1 and Chapter 3.1.2.1 

of the 2017-2022 GOM Multisale EIS. The G&G 

activities for oil and gas exploration are authorized on 

the basis of whether or not the proposed activities 

are (1) before leasing takes place (prelease) and 

authorized by permits or (2) on an existing lease 

(postlease or ancillary) and authorized by OCS plan 

approvals, plan revisions, or by a requirement for 

notification of BOEM before certain on-lease 

activities are undertaken. BOEM’s resource 

evaluation program oversees G&G data acquisition 

and permitting activities pursuant to regulations at 30 CFR parts 550 and 551. There are a variety of 

G&G activities that are conducted for oil and gas exploration and development as on-lease activities:
3-6 2018 Gulf of Mexico Supplemental EIS

The term 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 to 

be extracted.

A development well is drilled to 

extract resources from a known 

hydrocarbon reservoir.

• various types of deep-penetration seismic airguns used almost exclusively for oil 

and gas exploration;

• electromagnetic surveys, deep stratigraphic and shallow test drilling, and various 

remote-sensing methods in support of oil and gas exploration;

• high-resolution geophysical (HRG) surveys (airgun and non-airgun) used to 

detect and monitor geohazards, archaeological resources, and certain types of

benthic communities; and

• geological and geotechnical bottom sampling used to assess the suitability of 

seafloor sediments for supporting structures (e.g., platforms, pipelines, and 

cables), as well as to identify environmental resources such as chemosynthetic 

communities, gas hydrates, buried channels and faults, and archaeological 

resources.

Exploration and Delineation Plans and Drilling

Oil and gas operators use drilling terms that 

represent stages in the discovery and development of 

hydrocarbon resources. If a resource is discovered 

during the drilling of an exploration well in quantities 

appearing to be economically viable, one or more 

follow-up delineation wells are drilled. Refer to 

Figure 3-1 above for a relative exploration timeline on

an oil or gas lease. 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. Following a 

discovery, an operator often temporarily plugs and abandons the well to allow time for a 

development plan 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) (i.e., 

jack-up rigs, semisubmersible rigs, submersible rigs, platform rigs, or drill ships). Non-MODUs, such 

as inland barges, are also used. Refer to Chapter 3.1.2.2 of the 2017-2022 GOM Multisale EIS for 

more information on exploration and delineation plans and drilling.

3.1.1.2 Development

Offshore Development

Delineation and production wells are sometimes 

collectively termed development wells. After a development 

well is drilled, the operator must decide whether or not to 

complete the well without delay, to delay completion with the 

rig on station so that additional tests may be conducted, or to 

temporarily abandon the well site and move the rig off station to a new location and drill another well. 

Sometimes an operator may decide to drill a series of development wells, move off location, and 
Impact-Producing Factors and Scenario 3-7 

The production well is completed

for the purpose of extracting 

hydrocarbons from the subsurface.

The process that includes the 

suite of activities that are carried 

out to prepare a development 

well for production is referred to 

as the completion process.

then return with a rig to complete all the wells at one time. If 

an exploration well is clearly a dry hole and contains no oil or 

gas, the operator would typically permanently abandon the 

well without delay but could also convert the well into an 

injection well to store CO2, dispose of waste water, enhance 

oil production and mining, or prevent saltwater intrusion. 

Development well drilling is discussed in greater detail in Chapter 3.1.3.1 of the 2017-2022 GOM

Multisale EIS.

Offshore production systems may be placed over development wells to facilitate production 

from a prospective hydrocarbon reservoir. These structures provide the means to access and 

control wells. They serve as a staging area to process and treat produced hydrocarbons from wells, 

initiate export of 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. Offshore production 

systems are discussed in greater detail in Chapter 3.1.3.2 of the 2017-2022 GOM Multisale EIS.

Pipelines are the primary method used to transport a variety of liquid and gaseous products 

between OCS production sites and onshore facilities around the GOM and are installed during the 

development phase. A mature pipeline network exists in the GOM to transport oil and gas 

production from the OCS to shore. BOEM projects that the majority of new pipelines constructed as 

a result of a proposed action would connect to the existing pipeline infrastructure.

Coastal Infrastructure

Oil and gas exploration, production, and development activities on the OCS are supported by 

an expansive onshore infrastructure industry that includes large and small companies providing an 

array of services from construction facilities, service bases, and waste disposal facilities to crew, 

supply, and product transportation, as well as processing facilities. It is an extensive and mature 

system that provides support for both offshore and onshore oil and gas activities in the GOM region. 

Coastal Infrastructure is discussed in greater detail in Chapter 3.1.7 of the 2017-2022 GOM

Multisale EIS and Chapter 4.14.1 of this Supplemental EIS. 

3.1.1.3 Production

Depending on the information obtained from 

delineation or exploration 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 and are positioned within the reservoir to maximize 

the volume of production. 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.
3-8 2018 Gulf of Mexico Supplemental EIS

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 that the operator may 

decide to move off location and delay the work required to prepare the wells for production; for 

example, additional well tests may be required or the drilling rig may be committed to another 

location. When a decision to delay the work is chosen, each development well would be temporarily 

abandoned before the drilling rig can be moved to another location. It is also common for an 

operator to drill the required number of development wells in stages, leaving sometime between the 

stages to evaluate the information obtained from the wells and, if necessary, use this information to 

modify the development program.

A deepwater operations plan is required for all deepwater development projects in water 

depths ≥1,000 ft (305 m) and for all projects proposing subsea production technology. A deepwater 

operations plan is required initially and is usually followed by a development operations coordination 

document (DOCD). The DOCD is the chief planning document that lays out an operator’s specific 

intentions for development. Production is discussed in greater detail in Chapters 3.1.1 and 3.1.3.2 of 

the 2017-2022 GOM Multisale EIS. Refer to Appendix A.2 of the 2017-2022 GOM Multisale EIS for 

a detailed discussion on regulations, processes, and environmental information requirements for 

lessees and operators related to exploration plans (EPs), deepwater operations plans, and DOCDs.

3.1.1.4 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. Regulations and processes related to structure and site clearance are 

discussed in Appendix A.13 of the 2017-2022 GOM Multisale EIS. The structures are generally 

grouped into two main categories depending upon their relationship to the platform/facilities (i.e., 

piles, jackets, caissons, templates, mooring devises, etc.) or the well (i.e., wellheads, casings, 

casing stubs, etc.).

A varied assortment of severing devices and methodologies has been designed to cut 

structural targets during the course of decommissioning activities. These devices are generally 

grouped and classified as either nonexplosive or explosive, and they can be deployed and operated 

by divers using remotely operated vehicles, or from the surface. Which severing tool the operators 

and contractors use takes into consideration the target size and type, water depth, economics, 

environmental concerns, tool availability, and weather conditions.

Nonexplosive severing tools are used on the OCS for a wide array of structure and well 

decommissioning targets in all water depths. Based on 10 years of historical data (1994-2003), 

nonexplosive severing is employed exclusively on about 58 (~37%) removals per year (USDOI, 

MMS, 2005). Since many decommissionings use both explosive and nonexplosive technologies 

(prearranged or as a backup method), the number of instances may be much greater. Common 

nonexplosive severing tools consist of abrasive cutters (e.g., sand cutters and abrasive water jets), 
Impact-Producing Factors and Scenario 3-9 

Completed and producing wells 

may require periodic reentry that 

is designed to maintain or 

restore a desired flow rate. 

These procedures are referred to 

as a well “workover.”

mechanical (carbide) cutters, diver cutting (e.g., underwater arc cutters and the oxyacetylene/

oxy-hydrogen torches), and diamond wire cutters. Explosive severance tools can be deployed on 

almost all structural and well targets in all water depths. Historically, explosive charges are used in 

about 98 (~63%) decommissioning operations annually (USDOI, MMS, 2005), often as a back-up 

cutter when other methodologies prove unsuccessful. Explosives work to sever their targets by 

using (1) mechanical distortion (ripping), (2) high-velocity jet cutting, and (3) fracturing or “spalling.”

While production structures are removed, it is anticipated that multiple appurtenances or 

types of equipment (e.g., subsea systems, pipelines, umbilical lines, etc.) would not be removed 

from the seafloor if placed in waters exceeding 800 m (2,625 ft), as allowed under certain conditions 

in 30 CFR part 250. For more information on decommissioning, refer to Chapter 3.1.6 of the 

2017-2022 GOM Multisale EIS. 

Workovers and Abandonments

Workover operations are also carried out to evaluate 

or reevaluate a geologic formation or reservoir (including 

recompletion to another stratum) or to permanently abandon 

a part or all of a well. Workovers on subsea completions 

require that a rig be moved on location to provide surface 

support. Workovers can take from 1 day to several months to 

complete depending on the complexity of the operations, with 

a median of 7 days. Current oil-field practices include 

preemptive procedures or treatments that reduce the number of workovers required for each well. 

On the basis of historical data, BOEM projects a producing well may have seven workovers or other 

well activities during its lifetime.

There are two types of well abandonment operations—temporary and permanent. An 

operator may temporarily abandon a well to (1) allow detailed analyses or additional delineation 

wells while deciding if a discovery is economically viable, (2) save the wellbore for a future sidetrack 

to a new geologic bottom-hole location, or (3) wait on design or construction of special production 

equipment or facilities. The operator must meet specific requirements to temporarily abandon a well. 

Permanent abandonment operations are undertaken when a wellbore is of no further use to the 

operator (i.e., the well is a dry hole or the well’s producible hydrocarbon resources have been 

depleted). During permanent abandonment operations, equipment is removed from the well, and 

specific intervals in the well that contain hydrocarbons are plugged with cement. A cement surface 

plug is also required for the abandoned wells. This serves as the final isolation component between 

the wellbore and the environment.
3-10 2018 Gulf of Mexico Supplemental EIS

What is a scenario? Scenario 

development is the process of 

analyzing and projecting future 

activities that could occur as a 

result of each action alternative 

(i.e., Alternative A, B, C, or D).

How are ranges determined? The 

low and high production scenarios, 

and the factors that influence them,

are used to create the range in 

scenario oil and gas activity.

3.1.2 How Much and Where is Activity Expected to Occur as a Result of a 

Proposed Action?

A scenario describes the offshore activities that could 

occur for a single proposed lease sale under each alternative. 

BOEM’s Gulf of Mexico OCS Region developed these 

scenarios to support the detailed analyses of a proposed 

lease sale’s potential impacts whether regionwide or for 

individual planning areas, as defined in the alternatives in 

Chapter 2.2.2. Each scenario is a hypothetical framework of 

assumptions based on estimated amounts, timing, and 

general locations of OCS exploration, development, and production for offshore and onshore 

activities and facilities. The scenario for each alternative is defined as a set of ranges for resource 

estimates, projected exploration and development activities, and impact-producing factors. 

The scenarios do not predict future oil and gas activities with absolute certainty even though 

they were formulated using historical information and current trends in the oil and gas industry. 

These scenarios are only approximate since future factors such as the economic climate, the future 

availability of support facilities, and future pipeline capacities are all unknown. The scenarios used 

in the 2017-2022 GOM Multisale EIS represent the best assumptions and estimates of a set of future 

conditions that are considered reasonably foreseeable and suitable for presale impact analyses 

(refer to Chapter 3 of the 2017-2022 GOM Multisale EIS). The development scenarios do not 

represent a BOEM recommendation, preference, or endorsement of any level of leasing or offshore 

operations or of the types, numbers, and/or locations of any onshore operations or facilities.

How are the Scenarios Developed?

BOEM uses a series of spreadsheet-based data 

analyses tools to develop the forecasts of oil and gas 

exploration, discovery, development, and production 

activity scenario for each action alternative presented in 

the 2017-2022 GOM Multisale EIS and this Supplemental 

EIS. The activity level associated with a proposed lease 

sale could vary based on a number of factors, including 

the price of oil, hydrocarbon resource potential, cost of development, and resource availability (e.g., 

drill rig availability), among other things. The scenario information presented takes into account 

historical oil and gas prices, price trends, oil and gas supply and demand, and related factors that 

influence oil and gas product-price and price volatility. The analyses are compared with actual 

historical activity and infrastructure data to ensure that historical precedent, as well as recent trends, 

is reflected in each activity forecast. Due to the inherent uncertainties associated with an 

assessment of undiscovered resources, probabilistic techniques were employed to develop the 

scenario, and the results are reported as a range of values corresponding to probabilities of 

occurrence.
Impact-Producing Factors and Scenario 3-11

What does a range of activity

mean? A meaningful range 

provides a reasonable expectation 

of the lowest to highest oil and gas 

production and associated activity

anticipated from a single proposed 

lease sale.

BOEM used these analyses to develop a 

reasonable low activity scenario and a reasonable high 

activity scenario for each alternative. BOEM does not 

expect every lease sale to reach the highest high or 

lowest low of the forecasted scenario ranges, but every 

lease sale will fall within the ranges. The range of 

volumes described by these scenarios represents 

BOEM’s best estimate of the range of possible production 

volumes and associated activity that can reasonably be 

expected from the acreage leased during a single proposed lease sale for Alternatives A, B, C, 

and D. Under Alternative D, the number of blocks that would become unavailable for lease 

represents a small percentage (<4%) of the total number of blocks to be offered under Alternative A, 

B, or C. Therefore, Alternative D could reduce offshore infrastructure and activities or may shift the 

location of offshore infrastructure and activities farther from sensitive topographic zones, but though 

this may affect the outcome of activity, the ranges provided for Alternatives A, B, and C are broad 

enough to encompass this change. The location and geologic formation of the oil and gas reserves, 

and the ability to access them, would determine if a reduction in offshore infrastructure and activities 

would occur or not. Since the ranges given for Alternatives A, B, and C are broad and represent the 

low and high levels of forecasted activity, any reduction of activity from choosing Alternative D would 

still fall within those ranges; therefore, the scenarios do not change when considering Alternative D. 

The potential impacts associated with selecting Alternative D are discussed in Chapter 4 under each 

resource. Refer to Chapter 2.2.2.4 for more information on Alternative D.

These scenarios are developed to provide the environmental impact analyses in Chapter 4

the flexibility to develop impact metrics for the full range of potential impacts that could be possible 

from a single proposed lease sale. BOEM is confident that the analysis methodology, with 

adjustments and refinements based on recent activity levels and industry information, adequately 

project Gulf of Mexico OCS oil- and gas-related activities in both the short term and the long term in 

the analyses for the 2017-2022 GOM Multisale EIS and this Supplemental EIS. 

To analyze impact-producing factors for a proposed action and each alternative, the 

geographic ranges of each alternative were divided into offshore subareas based upon ranges in 

water depth. Figure 3-2 depicts the location of the offshore subareas. The water-depth ranges 

reflect 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.
3-12 2018 Gulf of Mexico Supplemental EIS

Figure 3-2. Offshore Subareas in the Gulf of Mexico.

The major impact-producing factors of a single proposed lease sale (including the number of 

exploration and delineation wells, production platforms, and development wells) projected to develop 

and produce the estimated oil and gas resources for Alternatives A, B, and C are given in Table 3-1. 

This table shows the distribution of these factors by offshore subareas for each alternative. 

Table 3-1 also includes estimates of the major impact-producing factors related to the projected 

levels of exploration, development, and production activity. Estimates of resources and facilities are 

distributed into each of the subareas. The activities found in Table 3-1 will occur within the 50-year 

analysis period of 2017-2066. When analyzing hydrocarbon resources by planning area across the 

GOM, the majority of oil and gas resources are located within the boundaries of the CPA; therefore, 

the majority of activity is expected to occur in the CPA.
Impact-Producing Factors and Scenario 3-13

Table 3-1. Offshore Scenario Activities Related to a Single Proposed Lease Sale for Alternative A, B, 

or C from 2017 through 2066. 

Activity Alternative1 Offshore Subareas (m)2Totals3

0-60 60-200 200-800 800-1,600 1,600-2,400 >2,400

Exploration 

and 

Delineation 

Wells

A 24-634 8-300 5-11 6-15 5-8 5-16 53-984

B 20-570 5-293 2-8 2-10 2-2 2-10 33-893

C 4-64 2-7 2-3 3-5 3-6 3-6 17-91

Development 

and 

Production 

Wells4

A Total 14-326 7-220 7-95 13-51 10-37 10-38 61-767

B Total 10-282 4-211 4-78 10-35 9-31 9-34 46-671

C Total 4-44 4-9 4-17 4-16 3-6 3-4 22-96

A Oil 1-35 0-23 3-46 6-22 5-19 4-19 19-164

B Oil 1-32 0-23 2-38 5-18 4-16 4-17 16-144

C Oil 0-5 0-1 2-9 1-5 1-4 1-3 5-27

A Gas 1-35 0-23 3-46 6-22 5-19 4-19 19-164

B Gas 5-169 2-120 0-17 1-7 1-6 1-7 10-326

C Gas 2-27 2-6 0-4 1-7 0-1 0-1 5-46

Installed

Production 

Structures

A 8-183 4-85 1-4 1-3 1-2 1-3 16-280

B 7-158 3-81 1-3 1-2 1 1-2 14-247

C 3-25 2-4 1 1 1 1 9-33

Production 

Structures 

Removed 

Using 

Explosives

A 6-130 3-63 0 0 0 0 9-193

B 5-112 2-60 0 0 0 0 7-172

C 2-18 2-3 0 0 0 0 4-21

Total 

Production 

Structures 

Removed

A 8-183 4-85 1-4 1-3 1-2 1-3 16-280

B 7-158 3-81 1-3 1-2 1 1-2 14-247

C 3-25 2-4 1 1 1 1 9-33

Length of 

Installed 

Pipelines 

(km)5

A 59-527 53-417 53-327 78-358 59-275 53-240 355-2,144

B 40-395 34-336 33-240 55-233 50-227 42-210 254-1,641

C 20-132 20-81 20-88 24-125 10-48 11-31 105-505

ServiceVessel Trips 

(1,000’s round 

trips)

A 9-265 4-126 6-51 7-38 7-26 7-36 43-541

B 8-229 3-120 6-39 6-26 6-15 6-25 38-452

C 3-36 2-6 6-13 6-13 6-12 6-11 30-89

Helicopter 

Operations 

(1,000’s round 

trips) 

A 52-2,131 34-

1,409 8-71 8-53 8-36 8-53 122-3,750

B 43-1,848 26-

1,426 8-53 8-36 8-18 8-36 105-3,415

C 17-299 17-71 8-18 8-18 8-18 8-18 70-440

1 Alternative D could reduce activity values of the combined Alternative A, B, or C. Refer to Chapter 2.2.2.4 for 

more information. Alternative A would be a regionwide lease sale, Alternative B would be the CPA/EPA portions of 

the proposed lease sale area, and Alternative C would be the WPA portion of the proposed lease sale area. 2 Refer to Figure 3-2. 3 Subareas totals may not add up to the planning area total because of rounding. 4 Development and Production Wells includes some exploration wells that were re-entered and completed. These 

wells were removed from the Exploration and Delineation well count. 5

 Projected length of pipelines does not include length in State waters.
3-14 2018 Gulf of Mexico Supplemental EIS

While the activities associated with exploration, development, production, and abandonment 

of leases in the GOM are expected to occur during the 50-year analysis period of 2017-2066, the 

Cumulative OCS Oil and Gas Program scenario has an analysis period of 70 years or 2017-2086. 

The Cumulative OCS Oil and Gas Program scenario includes the 50-year analysis period for a 

single proposed lease sale (e.g., Lease Sale 250). It is important to note that a single proposed 

lease sale, no matter which alternative is selected, would represent only a small proportion of activity 

and a small contribution to the overall Cumulative OCS Oil and Gas Program activity forecasted to 

occur between 2017 and 2086 (refer to Table 3-2). The information in Table 3-2 represents the 

incremental contribution of each alternative of a single proposed lease sale (e.g., Lease Sale 250) to 

the Cumulative OCS Oil and Gas Program scenario (2017-2086). Further information about the 

Cumulative OCS Oil and Gas Program scenario can be found in Chapter 3.3.2.1 below. Specific 

projections for activities associated with a single proposed lease sale under each alternative are 

discussed in the following scenario sections.

Table 3-2. Percent of Production of Each Alternative of a Single Proposed Lease Sale (2017-2066) 

in Relation to Each Cumulative Production Scenario.

Single Proposed 

Lease Sale 

(2017-2066) 

Percent of Production of a Single Proposed Lease Sale in Relation to

Cumulative Production 

Regionwide 

(2017-2086)

Cumulative Production 

in the CPA/EPA 

(2017-2086)

Cumulative Production 

in the WPA 

(2017-2086)

Alternative A 1.2-4.2% – –

Alternative B 1.0-3.6% 1.2-4.4% –

Alternative C 0.2-0.6% – 1.2-3.5%

Note: Alternative D could reduce production values of the combined Alternative A, B, or C. Refer to 

Chapter 2.2.2.4 for more information.

3.1.2.1 Exploration Scenario

Geophysical surveys generally would be the first activities to occur within the Gulf of Mexico. 

For each alternative, G&G surveys are projected to follow the same trend as exploration drilling 

activities, which would peak in the first 20-25 years and then begin declining, with regards to a 

particular lease sale. The HRG surveys generally occur before exploratory drilling, but they can also 

occur before development drilling, platform and pipeline installation, and decommissioning activities. 

It is important to note that the cycling of G&G data acquisition is not driven by the 50-year life cycle 

of a single productive lease but instead would tend to respond to new production or potential new 

production driven by new technology. Consequently, some areas would be resurveyed in 2-year 

cycles, while other areas, considered nonproductive, may not be surveyed for 20 years or more. 

Table 3-3 reflects a reasonable level of G&G surveying activities during 2017-2066 that could be 

expected to occur leading up to and following a scheduled lease sale in the Gulf of Mexico. The 

estimates below far exceed the number of blocks available for leasing in the entire Gulf of Mexico 

OCS. Data collection may be repeated on any one block as technology advances, or multiple 

surveys may be conducted over the same OCS blocks for different purposes (e.g., prelease 

exploratory surveys and shallow hazard surveys). Ancillary permits are postlease operational 
Impact-Producing Factors and Scenario 3-15

permits obtained by lease owners in furtherance of developing oil and gas resources. Ancillary 

activities are defined in 30 CFR § 550.105 and regulated in 30 CFR §§ 550.207-550.210.

Table 3-3. Exploration and Seismic Survey Activity Leading Up To and Following a Proposed Lease 

Sale in the Gulf of Mexico

Following a lease sale, exploratory drilling activity could begin within the 1st year and would 

likely continue to occur over the course of each lease. The majority of the exploratory drilling for all 

blocks leased would likely occur early and would generally be complete by the 25th year for 

Alternative A, B, C, or D. Figure 3-3(A) shows the timeline of drilling exploration and delineation 

wells for a proposed action under Alternative A. Figure 3-3(B, C) depicts the high and low 

production scenario by planning area and water depth. When analyzing both the low and high 

production scenarios for all of the alternatives, most exploration drilling activity is expected to occur

on the continental shelf (0- to 200-m [0- to 656-ft] water depth). Note that exploratory drilling activity 

spans less than 40 years and exploration wells are not all drilled during the same time period. The 

most exploration wells drilled in a given year from a proposed action is 64. The most exploration 

wells drilled in any given 5-year span is 298 (averaging about 32 wells drilled per year during the 

exploration phase), demonstrating that all forecasted exploration wells are drilled over time and not 

consolidated into a narrow timeframe, i.e., a single year. Figure 3-3(B, C) gives the reader an idea 

of which water-depth category the majority of activity within the GOM would occur; however, in 

reality, the activity would not be equally distributed across water-depth categories as depicted and 

would have geographic specificity based on geology.

Survey Area

2D 

Surveys 

(km)

2D 

Permits

3D Lease 

Blocks

3D 

Permits

Ancillary 

Permits

HRG 

Surveys

VSP 

Surveys

Regionwide 77,248-

1,046,073 31-310 13,400-185,000 25-128 19-214 87-709 17-263

CPA/EPA 75,639-

970,434 27-283 18,900-171,300 20-108 16-198 64-576 11-234

WPA 1,448-

6,598 4-9 5,500-25,100 6-21 3-26 30-134 5-29

2D = two-dimensional; 3D = three-dimensional; HRG = high-resolution geophysical; VSP = vertical 

seismic profiling.
3-16 2018 Gulf of Mexico Supplemental EIS

Figure 3-3. (A) Number of Exploration and Delineation Wells Drilled over the Course of a Proposed 

Action under Alternative A for 50 Years. (B, C) Location of Exploration Wells Drilled 

during the Entire 50-Year Period.
Impact-Producing Factors and Scenario 3-17

3.1.2.2 Development Scenario

Offshore Development Scenario

The peak in platform installation would lag behind the peak in exploration drilling. Following 

a lease sale, support infrastructure installation would likely occur over the course of each lease but 

could begin within 1 year. The majority of platforms installed in early years would be caissons and 

small fixed platforms in shallow water. Floating structures installed in deeper water would take many 

years to construct and install. The highest number of platforms operating as a result of a lease sale 

would peak before year 10 in the low production scenario and around year 25 for the high production 

scenario. Figure 3-4(A) depicts the estimated number of operating production structures in the 

GOM, with the exception of subsea systems for a single proposed lease sale. Various single well to 

multi-well structures would be installed and commissioned depending on the water depth. There 

would be a slight temporal lag between peak development drilling and platform installation. 

Platforms that are operated after peak development maximize production from the remaining 

production wells. Table 3-1 and Figure 3-4(B, C) show the estimated range installed production 

structures by water-depth range. Note that the production activity spans 40 years and that 

production structures are not all operational concurrently. Figure 3-4(B, C) gives the reader an idea 

of which water-depth category the majority of activity within the GOM would occur; however, in 

reality, the activity would not be equally distributed across water-depth categories as depicted and 

would have geographic specificity based on geology. Of the possible 280 total high forecasted 

production structures (refer to Table 3-1), the most structures operating in a given year from a 

proposed action would be 108 structures. Laying pipeline is part of the development process and 

must begin before the production phase can begin for most leases. The total estimated length of 

pipeline laid for each alternative can be found in Table 3-1. Regardless of the production scenario 

or alternative, most support structure installation is expected to be on the continental shelf (0- to 

200-m [0- to 656-ft] water depth). 

Coastal Infrastructure Scenario

The extensive presence of coastal infrastructure is not subject to rapid fluctuations and 

results from long-term industry trends. Existing oil and gas infrastructure is expected to be sufficient

to handle development associated with a proposed action. Should there be some expansion at 

current facilities, the land in the analysis area is sufficient to handle such development. The number 

and location of existing coastal infrastructure can be seen in Table 3-4. There are currently 

144 pipeline landfalls (i.e., pipelines that have at one time or another carried hydrocarbon product) in 

the Louisiana Coastal Area (LCA) (Smith, official communication, 2015). The BSEE and DOT share 

responsibility for pipeline regulation on the OCS in the transition between Federal and State waters. 

For more information on the regulation and permitting of pipelines, refer to Appendix A.3 of the 

2017-2022 GOM Multisale EIS.
3-18 2018 Gulf of Mexico Supplemental EIS

Figure 3-4. (A) Number of Production Structures and Service Vessels Operating over the Course of a 

Proposed Action under Alternative A for 50 Years. (B, C) Total Number of Platforms 

Installed in the Low and High Production Scenario by Water Depth. 
Impact-Producing Factors and Scenario 3-19

Table 3-4. Existing Coastal Infrastructure Related to OCS Oil- and Gas-Related Activities in the Gulf 

of Mexico.

Infrastructure Texas Louisiana Mississippi Alabama Florida Total

Pipeline Landfalls1 14 122 3 5 0 144

Platform Fabrication Yards2 12 37 4 1 0 54

Shipyards2 32 64 9 18 14 137

Pipe Coating Facilities2 9 6 0 2 2 19

Supply Bases2 32 55 2 7 0 96

Ports2 11 14 3 1 5 34

Waste Disposal Facilities2 16 29 3 3 2 53

Natural Gas Storage Facilities2 13 8 0 1 0 22

Helicopter Hubs2 118 115 4 4 0 241

Pipeline Shore Facilities2 13 40 0 0 0 53

Barge Terminals2 110 122 6 6 8 252

Tanker Ports2 4 6 0 0 0 10

Gas Processing Plants2 39 44 1 13 1 98

Refineries3 20 16 3 3 0 42

Petrochemical Plants2 126 66 2 9 13 216

1 Source: Smith, 2015.

2 Source: Dismukes, 2011a. 

3 Source: USDOE, Energy Information Administration, 2015.

3.1.2.3 Production Scenario

Development and Production Drilling

Figure 3-5 below depicts the number of development and production wells that may result 

from a low and high scenario case by planning area and water depth. BOEM estimates that 

approximately 63-70 percent of wells drilled as development wells will become producing wells. 

Because there is some overlap, the two types of wells are grouped to prevent double counting. The 

distribution of development and production wells by water depth that could possibly occur as result 

of Alternative A, B, or C can be found in Table 3-1. 

Development and production activity during a proposed action usually takes place over a 

49-year period, beginning with the installation of a production platform on the first lease and ending 

with the drilling of the last development wells. The majority of development well drilling would likely 

occur in the first 25 years of each lease. Production of oil and gas could begin by the 3rd year after 

the lease sale and generally would conclude by the 50th year; refer to Figure 3-5(A) below. In the 

low production scenario, development and production activity is expected to occur fairly evenly 

spread between the continental shelf (0- to 200-m [0- to 656-ft] water depth) and deeper water 

depths (200-1,600 m; 656-5,249 ft) with a majority of activity in the CPA; however, for the high 

production scenario, most development and production drilling activity is expected to occur on the 

continental shelf (0- to 200-m [0- to 656-ft] water depth). Figure 3-5(B, C) gives the reader an idea 

of which water-depth category the majority of activity within the GOM would occur; however, in 
3-20 2018 Gulf of Mexico Supplemental EIS

reality, the activity would not be equally distributed across water-depth categories as depicted and 

would have geographic specificity based on geology. Note that production drilling activity spans 

40 years and that production wells would not all be drilled during the same time period. The most 

wells drilled in a given year would be 34, and the most wells drilled in any given 5-year span would 

be 150 (averaging 30 wells drilled per year), demonstrating that all the forecasted wells are drilled 

over time and not consolidated into a narrow timeframe, i.e., a single year.

Figure 3-5. (A) Number of Production Wells Drilled over the Course of a Proposed Action under 

Alternative A for 50 Years. (B, C) Total Number of Development and Production Wells 

Drilled in the Low and High Production Scenario by Water Depth for Alternative A. 
Impact-Producing Factors and Scenario 3-21

Oil and Gas Production

Table 3-5 presents the projected oil and gas production for a single proposed lease sale 

under each alternative (2017-2066) and for the Cumulative OCS Oil and Gas Program (2017-2086). 

Alternative D could reduce offshore production when chosen in conjunction with Alternative A, B, 

or C. However, it is also possible that Alternative D would only shift the location of offshore 

infrastructure and activities farther from sensitive topographic zones and not lead to a reduction in 

production. Refer to Chapter 2.2.2.4 for more information on Alternative D. Refer to Table 3-1

above for the offshore scenario activities related to a single proposed lease sale for Alternative A, B, 

or C from 2017 through 2066, which are associated with these projected oil and gas volumes in the 

Gulf of Mexico OCS.

Table 3-5. Projected Oil and Gas in the Gulf of Mexico OCS.

Reserve/Resource 

Production

Lease Sale

(2017-2066)

OCS Cumulative

(2017-2086)

Alternative A: Regionwide OCS Lease Sale

Oil (BBO) 0.211-1.118 15.482-25.806

Gas (Tcf) 0.547-4.424 57.875-108.513

Alternative B: Regionwide OCS Proposed Lease Sale 

Excluding Available Unleased Blocks in the WPA Portion

of the Proposed Lease Sale Area 

(or the CPA/EPA Portion of the Proposed Lease Sale Area)

Oil (BBO) 0.185-0.970 13.707-22.152

Gas (Tcf) 0.441-3.672 46.328-84.009

Alternative C: Regionwide OCS Proposed Lease Sale 

Excluding Available Unleased Blocks in the CPA/EPA Portions 

of the Proposed Lease Sale Area 

(or the WPA Portion of the Proposed Lease Sale Area)

Oil (BBO) 0.026-0.148 1.775-3.654

Gas (Tcf) 0.106-0.752 11.547-24.504

BBO = billion barrels of oil.

Tcf = trillion cubic feet.

Regardless of the alternative, the majority of oil and gas resources are located within the 

boundaries of the CPA. Therefore, for a proposed action under Alternative A, which would 

encompass all acreage available for lease within the WPA, CPA, and EPA, the majority of the 

activity would still be located in the CPA. An analysis of the scenario forecast for Alternative A 

suggests that a maximum of 88 percent of the oil production and associated activity and 83 percent 

of the gas production and associated activity is forecasted to occur within the CPA/EPA. A 

maximum of 13 percent of the oil production and associated activity and 19 percent of the gas 

production and associated activity from Alternative A is forecasted to occur within the WPA. For 

Alternatives A, B, C, and D, the majority of production is expected to occur along the slope in both 

the low and high production scenarios (Figure 3-6). Note that production activity spans to just over 
3-22 2018 Gulf of Mexico Supplemental EIS

40 years. Figure 3-6(B, C) gives the reader an idea of which water-depth category the majority of 

activity within the GOM would occur; however, in reality, the activity would not be equally distributed 

across water-depth categories as depicted and would have geographic specificity based on geology. 

The highest production in a given year would be 0.112 billion barrels of oil equivalent (BOE), and the 

highest production in any given 5-year span would be 0.553 BOE (averaging 0.047 BOE per year 

when producing), demonstrating that the forecasted production occurs throughout the 40 years and 

is not consolidated into a narrow timeframe, i.e., a single year.

Figure 3-6. Total Oil and Gas Production (BOE) in the Gulf of Mexico in the Low and High Production 

Scenario by Water Depth. 

Relatively more exploration and development drilling and structure installation would occur 

on the shelf (in depths <200 m [660 ft]) than in deep water, regardless of the production case 

scenario (Table 3-6).

Table 3-6. Depth Distributions within the Proposed Regionwide Lease Sale Area. 

Geographic 

Province

Percent Wells Percent Platforms Percent Gas Percent Oil Production

Low High Low High Low High Low High

Shelf 46.5 85 75 95 13 73 1 6

Slope 53.5 15 25 5 87 27 99 94

3.1.2.4 Decommissioning Scenario

Table 3-1 shows platform removals by water-depth subarea as a result of Alternatives A, B, 

and C. Approximately 70 percent of production structures installed landward of the 800-m (2,625-ft) 

isobath could be removed using explosives. About 30 percent of production structures landward of 

the 800-m (2,625-ft) isobath and all structures in water deeper than the 800-m (2,625-ft) isobath 

would be removed using nonexplosive methods. While the production structure is removed, it is 

anticipated that multiple types of support equipment (e.g., subsea systems, pipelines, umbilical lines, 

etc.) would not be removed from the seafloor if placed in waters exceeding 800 m (2,625 ft) as 
Impact-Producing Factors and Scenario 3-23

allowed under certain conditions in 30 CFR part 250. An estimate of the well stubs and other 

various subsea structures that may be removed using explosives is not possible at this time.

3.1.2.5 Transportation Scenario

Pipelines are the primary method used to transport a variety of liquid and gaseous products 

between OCS production sites and onshore facilities around the GOM (Table 3-7). A mature 

pipeline network exists in the GOM to transport oil and gas production from the OCS to shore. 

Historically, barging in the GOM has remained less than 1 percent. In 2005, barging activity 

temporarily rose to 1.29 percent while pipelines damaged from hurricanes were repaired. The 

average amount of oil barged between 2010 and 2014 was 0.12 percent annually. The number of 

active barging systems has been reduced over time from approximately eight systems in 2005 to 

four systems in 2010 and has remained constant since then. It is assumed that barging would 

continue to account for <1 percent of the oil transported for the entire OCS Program and for any 

single alternative. Table 3-7 provides the percentages of oil barged to shore by subarea for each 

alternative. The floating, production, storage, and offloading (FPSO) systems are suitable for the 

light and intermediate oils of the GOM. The use of FPSOs is only projected in water depths 

>1,600 m (5,250 ft). Shuttle tankers are used to transport crude oil from FPSO production systems 

to Gulf Coast refinery ports or to offshore deepwater ports such as the Louisiana Offshore Oil Port 

(LOOP); the percentage of oil tankered is provided in Table 3-7. 

Table 3-7. Oil Transportation Scenario under Alternative A, B, or C.

Activity Alternative1 Offshore Subareas (m)2Totals3

0-60 60-200 200-800 800-1,600 1,600-2,400 >2,400

Percent 

Oil Piped4

A 72-94% 100% 100% 100% 100% 100-66% 99.8-90.0%

B 70-94% 100% 100% 100% 100% 100-50% 98.8-84.6%

C 100% 100% 100% 100% 100% 100% 100%

Percent 

Oil Barged

A 28-6% 0% 0% 0% 0% 0% 0.2%

B 30-6% 0% 0% 0% 0% 0% 0.2%

C 0% 0% 0% 0% 0% 0% 0%

Percent 

Tankered5

A 0% 0% 0% 0% 0% 0-34% 0-9.8%

B 0% 0% 0% 0% 0% 0-50% 0-15.2%

C 0% 0% 0% 0% 0% 0% 0%

1 Alternative D could reduce activity values of the combined Alternative A, B, or C. Refer to Chapter 2.2.2.4 for 

more information. Percentage values indicated here would not change.

2 Refer to Figure 3-1. Ranges are reported from the low production case scenario to the high production case 

scenario. 3 Subareas totals may not add up to the planning area total because of rounding.

4 100% of gas is assumed to be piped. 5 Tankering is forecasted to occur only in water depths >1,600 m (5,250 ft). 

According to the Helicopter Safety Advisory Conference (2015), from 1996 to 2014, 

helicopter operations (take offs and landings) in support of regionwide OCS operations have 

averaged, annually, about 1.2 million operations, 2.7 million passengers, and 386,000 flight hours. 

There has been a decline in helicopter operations from 1,668,401 in 1996 to 741,201 in 2014
3-24 2018 Gulf of Mexico Supplemental EIS

(Helicopter Safety Advisory Conference, 2015). Future projections are based on a high equal to the 

average number of flights over the last 15 years and a low equal to a continuing forecast of the 

current decline. Table 3-1 shows helicopter trips by water-depth subareas as a result of Alternatives 

A, B, and C.

Service vessels are one of the primary modes of transporting personnel between service 

bases and offshore platforms, drilling rigs, derrick barges, and pipeline construction barges. In 

addition to offshore personnel, service vessels carry cargo (i.e., freshwater, fuel, cement, barite, 

liquid drilling fluids, tubulars, equipment, and food) offshore. Service-vessel operations are most 

closely tied to actual production activities. Visual representation of this can be seen in 

Figure 3-4(A). Table 3-1 shows service-vessel trips by water-depth subareas as a result of 

Alternatives A, B, and C.

3.1.3 Summary of Routine Impact Producing Factors

Table 3-8 below outlines the impact-producing factors and operations assumed to routinely 

occur throughout the lifetime of lease. The impact-producing factors and operations are grouped by 

operational phases that consist of exploration, development, oil or gas production, and 

decommissioning. Refer to Table 3-9, which provides descriptions of the routine impact-producing 

factors and operations that occur during the lifetime of a lease. 
Impact-Producing Factors and Scenario 3-25

Table 3-8. Summary of the Timing of Impact-Producing Factors Associated with Routine Oil and Gas 

Activities.

Impact-Producing Factors 

and Activities

Exploration

Development Production Decommissioning

Geological 

and 

Geophysical 

Survey

Exploration 

and 

Delineation 

Drilling

Operations 

Geological and Geophysical X X X X X

Drilling X X X X -

Bottom Disturbance X X X X X

Infrastructure Emplacement - X X X -

Workovers and Abandonment - X X X -

Decommissioning and Removal - - - - X

Artificial Reefs - - - - X

Transport

Pipelines - X X X X

Barges - X X X X

Oil Tankers - - X X -

Service Vessels X X X X X

Helicopters X X X X X

Navigation Channels X X X X X

Discharges and Wastes

Operational Wastes and 

Discharges Generated by OCS 

Oil- and Gas-Related Facilities

- X X X X 

Operational Wastes and 

Discharges Generated by 

Service Vessels

X X X X X 

Onshore Disposal of Waste and 

Discharge Generated Offshore 

or Onshore

X X X X X 

Coastal Infrastructure

Construction Facilities X X X X -

Support Facilities and 

Transportation X X X X X 

Processing Facilities - - X X -

Other Types of Impact-Producing Factors

Air Emissions X X X X X

Noise X X X X X
Table 3-9. General Description of Routine Impact-Producing Factors. Impact-Producing Factors and Specific Sources Multisale EIS Chapter Reference General Description Exploration and Delineation Geological and Geophysical 3.1.2.1 The Exploration & Development (E&D) scenario considers two types of geophysical sur

surveys, which generally cover a large area of leased and/or unleased acreage; and (2) g

will include side-scan sonar and shallow-penetrating, reflection-seismic profiling conducted resources or seafloor features that might be problematic for operations, such as drilli

platform or pipeline on a more specific site. Geohazard surveys are often accompanied 

which involve sampling or measuring mechanical properties or stability of near-seafloor s

levels are dependent on equipment type and size. Airgun arrays may have so259 dB re 1 μPa-m, with frequencies <120 Hz. Other techniques (e.g., sparkers and boo212 to 221 dB re 1 μPa-m, with frequencies in the 800- to 1,200-Hz range (Richardson et a

and Marine Conservation Biology Institution, 2000). Further detailed information for G&G 

BOEM’s Atlantic OCS Proposed Geological and Geophysical Activities: Mid-Atlantic and 

Areas, Final Programmatic Environmental Impact Statement (Atlantic G&G Activities ProBOEM, 2014). Exploration and Delineation Plans and Drilling 3.1.2.2 Following a lease sale, exploratory drilling activity would likely occur over the course 

begin within 1 year. The majority of the exploratory drilling for all blocks leased would likegenerally be complete by the 25th year. If a resource is discovered during the drilling 

quantities appearing to be economically viable, one or more follow-up delineation wells wells are drilled to specific subsurface targets in order to obtain information about the resethe operator to identify the lateral and vertical extent of a hydrocarbon accumulation. Offshore Development and Production Development and Production Drilling 3.1.3.1 Delineation and production wells are sometimes collectively termed development well

approximately 63-70% of wells drilled as development wells become producing wells. Twell completion techniques performed in the Gulf of Mexico, and the type of well completio

well for production is based on the rock properties of the reservoir, as well as the proper

However, for the vast majority of well completions, the typical process includes installing ocasing; cementing the casing; perforating the casing and surrounding cement; injecting waas carrier fluid for a “frac pack”/sand proppant pack and gravel pack; treating/acidizing the the wellbore; installing production screens; running production tubing; and installing a prod

Infrastructure Emplacement/ Structure Installation 3.1.3.3 Structures may be placed over development wells to facilitate production from a pro

provide the means to access and control wells. They serve as a staging area to proc

hydrocarbons from wells, initiate export of produced hydrocarbons, conduct additio

stimulation, conduct workover activities, and carry out eventual abandonment procedure

offshore infrastructure installed for hydrocarbon production. Among these are pipe

platforms, caissons, well protectors, casing, wellheads, and conductors. Subsea wells may also be completed to produce hydrocarbons from on the shelf and iof the GOM. The subsea completions would require a host structure to control their flow 
Table 3-9. General Description of Routine Impact-Producing Factors. (continued). 

Impact-Producing Factors and Specific Sources Multisale EIS Chapter Reference General Description stream. Control of the subsea well is accomplished via an umbilical from the host. Pipelines are the primary means of transporting produced hydrocarbons from offsho

distribution centers or onshore processing points. Pipelines range from small-diam10-30 cm) gathering lines, sometimes called flowlines, that link individual wells and large-diameter (as large as 36 in; 91 cm) lines, sometimes called trunk lines, for transport ttypically be installed by lay barges that are either anchored or dynamically positioned while 

Production activities can disturb small areas of the sea bottom beneath or adjacent t

If mooring lines of steel, chain, or synthetic polymer are anchored to the sea bottom, or 

around the activity could also be directly affected by their emplacement. This disturcompaction or crushing beneath the structure or mooring lines and the resuspension ancaused by the activities. Offshore Infrastructure Presence 3.1.3.4 Anchoring: Most exploration drilling, platform, and pipeline emplacement operatio

anchors to hold the rig, topside structures, or support vessels in place. Anchors disturb th

in the area where dropped or emplaced. Leasing on the OCS results in operations that temporarily occupy sea bottom and 

dedicated uses. The OCS oil- and gas-related operations include the deployment of 

surveys, and installation of surface or subsurface bottom-founded production structures 

safety zones. While in use, these areas would become unavailable to commercial fisher

any other competing use. Light pollution in the GOM comes from OCS oil- and gas-related structures and sincrease visibility during night hours. The OCS oil- and gas-related structures in the G

incandescent lights and from the glow of burning or flaring natural gas that cannot be shore. Workovers and Abandonment 3.1.3.5 Workovers: Completed and producing wells may require periodic reentry that is design

a desired flow rate. These procedures are referred to as a well “workover.” Workover opout to evaluate or reevaluate a geologic formation or reservoir (including recompletion permanently abandon a part or all of a well. Workovers can take from 1 day to seve

depending on the complexity of the operations, with a median of 7 days. Current opreemptive procedures or treatments that reduce the number of workovers required for eahistorical data, BOEM projects a producing well may expect to have seven workovers or o

its lifetime. Abandonment Operations: There are two types of well abandonment operations—te

Temporary abandonment is described in Chapter 3.1.1.3 above. Permanent aban

undertaken when a wellbore is of no further use to the operator (i.e., the well is a dry hole hydrocarbon resources have been depleted). During permanent abandonment operation

from the well, and specific intervals in the well that contain hydrocarbons are plugged 

surface plug is also required for the abandoned wells. This serves as the final isolation wellbore and the environment. 
Table 3-9. General Description of Routine Impact-Producing Factors. (continued). 3-28 2018 Gulf of Mexico Supplemental EIS

Impact-Producing 

Factors and 

Specific Sources

Multisale EIS 

Chapter 

Reference

General Description

Transport

Barges 3.1.4.1 

The capacity of oil barges used offshore can range from 5,000 to 80,000 bbl. Barges transporting oil may remain 

offshore for as long as 1 week while collecting oil, although the average round trip is assumed to be only 5 days. 

Historically, barging in the GOM has remained less than 1%. In 2005, barging activity temporarily rose 

to 1.29% while pipelines damaged from hurricanes were repaired. In 2014, 0.08% of the total volume 

was transported by barge as compared with 0.13% in 2010. The average amount of oil barged between 

2010 and 2014 was 0.12% annually.

Oil Tankers 3.1.4.2 

The use of FPSOs and shuttle tankering are only projected in water depths >800 m (2,625 ft). Shuttle tankers 

are used to transport crude oil from FPSO production systems to Gulf Coast refinery ports or to offshore deepwater 

ports such as the LOOP. Shuttle tanker design and systems are in compliance with USCG regulations, the Jones 

Act, and OPA requirements. As such, shuttle tankers are required to be double hulled. In the Gulf of Mexico, the 

maximum size of shuttle tankers is limited primarily by the 34- to 47-ft (10- to 14-m) water depths. Because of 

these depth limitations, shuttle tankers are likely to be 500,000-550,000 bbl in cargo capacity.

Service Vessels 3.1.4.3 

Service vessels are one of the primary modes of transporting personnel between service bases and offshore 

platforms, drilling rigs, derrick barges, and pipeline construction barges. In addition to offshore personnel, service 

vessels carry cargo (i.e., freshwater, fuel, cement, barite, liquid drilling fluids, tubulars, equipment, and food) 

offshore.

Helicopters 3.1.4.4 

Helicopters are one of the primary modes of transporting personnel between service bases and offshore 

platforms, drilling rigs, derrick barges, and pipeline construction barges. Helicopters are routinely used for normal 

crew changes and at other times to transport management and special service personnel to offshore exploration 

and production sites. In addition, equipment and supplies are sometimes transported. An operation is considered 

a roundtrip and includes takeoff and landing.

Discharges and Wastes

Operational Wastes 

and Discharges 

Generated by OCS 

Oil- and Gas-Related 

Facilities

3.1.5.1

The primary operational wastes and discharges generated during offshore oil and gas exploration and 

development are drilling fluids, drill cuttings, various waters (e.g., bilge, ballast, fire, and cooling), deck drainage, 

sanitary wastes, and domestic wastes. During production activities, additional waste streams include produced 

water, produced sand, and well-treatment, workover, and completion fluids. Minor additional discharges occur from 

numerous sources. These discharges may include desalination unit discharges, blowout preventer fluids, boiler 

blowdown discharges, excess cement slurry, several fluids used in subsea production, and uncontaminated 

freshwater and saltwater.

The USEPA, through general permits issued by the USEPA Region that has jurisdictional oversight, regulates all 

waste streams generated from offshore oil and gas activities. The USEPA Region 4 has jurisdiction over the 

eastern portion of the Gulf of Mexico OCS, including all of the EPA and a portion of the CPA off the coasts of 

Alabama and Mississippi. The USEPA Region 6 has jurisdiction over the rest of the CPA and all of the WPA. Each 

USEPA Region has promulgated general permits for discharges that incorporate the 1993 effluent guidelines and 

2001 effluent guidelines for synthetic-based, fluids-wetted cuttings as a minimum.

Permits issued under Section 402 of the Clean Water Act for offshore activities must comply with any applicable 

water quality standards and/or Federal water quality criteria, as well as Section 403 of the Clean Water Act. Water 

quality standards consist of the waterbody’s designated uses, water quality criteria to protect those uses and to 
Table 3-9. General Description of Routine Impact-Producing Factors. (continued). 

Impact-Producing Factors and Specific Sources Multisale EIS Chapter Reference General Description determine if they are being attained, and antidegradation policies to help protect h

Discharges from offshore activities near State water boundaries must comply with all applstandards. Operational Wastes and Discharges Generated by Service Vessels 3.1.5.2 Discharges from supply/service vessels equal to or greater than 79 ft (24 m) in length a

Environmental Protection Agency’s NPDES under the Vessel General Permit (VGP). T

issued on March 28, 2013, became effective on December 19, 2013, and expires on Dece

2013a). The Final 2013 VGP regulates 26 specific discharge categories, including numerilimits for most vessels, and ensures that ballast-water treatment systems are functioning co

Onshore Disposal of Waste and Discharge Generated Offshore or Onshore 3.1.5.3 Wastes that are typically transported to shore include produced sand, aqueous fluids s

drilling and production operations, naturally occurring radioactive materials such as tank 

industrial wastes, municipal wastes, and other exploration and production wastes (Dismuke

Operators are prohibited in the GOM from discharging any produced sands offshore

25-bbl capacities), 55-gallon steel drums, and cone-bottom portable tanks are used to tranvia offshore service vessels. Total produced sand from a typical platform is estimated to b

1993). The primary onshore facilities that support offshore oil- and gas-related activities 

helicopter hubs at local ports/service bases, construction facilities (i.e., platform fabricatioshipyards), processing facilities (i.e., refineries, gas processing plants, and petrochemic

(i.e., pipeline shore facilities, barge terminals, and tanker port areas). Water discharges from either point sources, such as a pipe outfall, or nonpoint sources, such as rainfall run-o

Decommissioning and Removal Operations Decommissioning and Removal 3.1.6 During exploration, development, and production operations, the seafloor around activit

lease sale area becomes the repository of temporary and permanent equipment and struprocesses related to structure and site clearance are discussed in Appendix A.13 of the 2EIS. The structures are generally grouped into two main categories depending upon 

platform/facilities (i.e., piles, jackets, caissons, templates, mooring devises, etc.) or tcasings, casing stubs, etc.). A varied assortment of severing devices and methodologies has been designed to cut the course of decommissioning activities. These devices are generally grouped anonexplosive or explosive, and they can be deployed and operated by divers, remotely o

the surface. Which severing tool the operators and contractors use takes into consider

type, water depth, economics, environmental concerns, tool availability, and weather condi

Artificial Reefs 3.1.6.2 Although BSEE supports and encourages the reuse of obsolete oil and gas structures 

cooperating agency in implementing the National Artificial Reef Plan, specific requirem

departure to be granted. More information on these regulations and processes can be fo

the 2017-2022 GOM Multisale EIS. Structure-removal permit applications requesting 

Rigs-to-Reefs Policy undergo technical and environmental reviews. The policy docum

engineering and environmental standards that operators/lessees must meet to be grantstructure as an artificial reef. Conditions of approval are applied as necessary to minimize 
Table 3-9. General Description of Routine Impact-Producing Factors. (continued). 3-30 2018 Gulf of Mexico Supplemental EIS

Impact-Producing 

Factors and 

Specific Sources

Multisale EIS 

Chapter 

Reference

General Description

effects to sensitive habitat and communities in the vicinity of the structure and proposed artificial reef site. 

Additionally, structures deployed as artificial reefs must not threaten nearby structures or prevent access to oil and 

gas, marine mineral, or renewable energy resources.

Coastal Infrastructure

Onshore Facilities 3.1.7

Typical infrastructure (new or currently existing that may be expanded or retrofitted) that would support OCS 

activity and potentially may affect biological, physical, and socioeconomic resources include the following: 

• ports and support facilities (repair and maintenance yards, crew service, and; support sectors);

• construction facilities (platform fabrication yards, shipyards and shipbuilding yards, and pipecoating 

facilities and yards);

• transportation (offshore support vessels, tankers, pipelines, railroads, tank trucks, and navigation 

channels); and

• processing facilities (natural gas processing, natural gas storage, LNG, refineries, petrochemical 

plants, and waste management).

Other Routine Activities

Air Emissions 3.1.8

Activities affecting air quality include vessel operations during geophysical surveys, drilling activities, platform 

construction and emplacement, pipeline laying and burial operations, platform operations, flaring, fugitive 

emissions, support vessel and helicopter operations, and evaporation of volatile organic compounds (VOCs) during 

transfers and spills.

Activities affecting air quality onshore include emissions from new infrastructure constructed onshore and 

offshore activities that occur within 40 km (25 mi) of the State’s boundary.

Noise 3.1.9

Acoustic sources can be described by their sound characteristics. For the regulatory process, they are generally 

divided into two categories: pulsed and continuous noise. Pulsed noises (e.g., explosives, airguns, and impact pile 

drivers) are generally considered powerful sounds with relatively short durations, broadband frequency content, and 

rapid rise times to peak levels. Continuous noises generally include all other noise (e.g., rotary machinery, 

propeller cavitation, and vibratory pile drivers), including vessel noise.

New and Unusual 

Technology 3.1.10

Technologies continue to evolve to meet the technical, environmental, and economic challenges of deepwater 

development. The operator must identify new or unusual technology, as defined in 30 CFR § 550.200, in 

exploration and development plans. Some of the technologies proposed for use by the operators are actually 

extended applications of existing technologies and interface with the environment in essentially the same way as 

well-known or conventional technologies. These technologies are reviewed by BOEM for alternative compliance or 

departures that may trigger additional environmental review.
Impact-Producing Factors and Scenario 3-31

3.2 ACCIDENTAL EVENTS

3.2.1 What Events Might Accidentally Occur as a Result of Operations Following 

a Lease Sale? 

As a consequence of routine activities or operations assumed to 

routinely occur throughout the lifetime of lease, the potential for accidents exist. 

Types of reasonably foreseeable accidental events include releases into the 

environment (e.g., oil spills, loss of well control, accidental air emissions, 

pipeline failures, and chemical and drilling fluid spills), collisions (e.g., 

helicopter, service vessels, and platforms) and spill-response activities. 

Substantial preventative measures and Federal regulatory requirements from prevention to spill 

response, which are summarized below and described in greater detail in Chapter 3.2 of the 

2017-2022 GOM Multisale EIS, are in place to mitigate these events. 

3.2.1.1 Releases into the Environment

Oil Spills: Accidental releases into the environment can be caused by many factors. 

Oil-spill occurrence cannot be predicted, but an estimate of its likelihood can be quantified. BOEM 

has estimated the source and number of accidental oil spills that may occur based on the estimated 

volume of oil production for each program area and the assumed mode of transportation (Anderson 

et al., 2012). Oil-spill data indicate that the vast majority of spills reported in the Gulf of Mexico are 

≤1 bbl. The most common cause of oil spills from both platforms and pipelines are hurricane related, 

since multiple accidental releases into the environment can occur during one hurricane event

(ABS Consulting, Inc., 2016). Platform and pipeline spills include both crude oil and condensate, but 

platform spills may also include refined products such as diesel fuel. Crude oils are a natural 

mixture of hundreds of different compounds, and the chemical composition can vary significantly 

from different producing areas. Once spilled, oil is subject to a number of physical, chemical, and 

biological processes that alter its composition and that can influence spill-response activities and 

determine environmental impacts. Spills from pipelines are assumed to occur within their respective 

routes from production platform to destination. A loss of well control can occur when improperly 

balanced well pressure results in sudden, uncontrolled releases of fluids from a wellhead or wellbore 

(PCCI Marine and Environmental Engineering, 1999; Neal Adams Firefighters, Inc., 1991).

Pipeline Breaks: Substantial sources of damages to OCS pipeline infrastructure can be 

caused by corrosion, physical pipeline stress due to location, mass sediment movements, and 

mudslides that can exhume or push the pipelines into another location and by accidents due to 

weather or impacts from anchor drops or boat collisions.

Other Spills: Chemicals and synthetic-based drilling fluids are used in offshore oil and gas 

drilling and production activities, and may be spilled to the environment due to equipment failure, 

weather (i.e., wind, waves, and lightning), accidental collision, and human error.
3-32 2018 Gulf of Mexico Supplemental EIS

Air Emissions: Accidental events associated with offshore oil- and gas-related activities 

can result in the emission of air pollutants. These OCS oil- and gas-related accidental events could 

include the release of oil, condensate, or natural gas; chemicals used offshore; pollutants from the 

burning of these products; fire; or H2S release.

Trash and Debris: The policy regarding marine debris prevention is outlined in NTL 

2015-BSEE-G03; however, equipment may be accidentally dropped to the seafloor or debris may be 

released accidentally from a platform or service vessel.

3.2.1.2 Collisions

Most collision mishaps are the result of service vessels colliding with platforms or vessel 

collisions with pipeline risers. The leading causes, not all inclusive, of recent helicopter accidents 

were engine related, loss of control or improper procedures, helideck obstacle strikes, controlled 

flight into terrain, and other technical failures (Helicopter Safety Advisory Conference, 2015).

3.2.1.3 Spill Response

In some cases, response efforts can also be an impact-producing factor. Offshore removal 

and spill-containment efforts to respond to an ongoing spill would likely require multiple technologies, 

including source containment, mechanical spill containment and cleanup, in-situ burning of the slick, 

and the use of chemical dispersants. Treatment methods for spills that extend onshore to sand 

beaches and marshes can include manual and mechanical removal, an on-site treatment plant, and 

sediment relocation. In the event of a spill, there is no single method of containment and removal 

that would be 100-percent effective. Refer to Chapter 3.2.3 below for more information.

3.2.2 How Many Oil Spills Could Occur as a Result of a Proposed Lease Sale?

Analysis of Offshore Spills ≥1,000 bbl

BOEM conducts an oil-spill risk analysis prior to conducting lease sales in OCS areas (refer 

to Figure 3-7). The analysis is conducted in three parts:

(1) the trajectories of oil spills from hypothetical spill locations, which are simulated 

using the Oil Spill Risk Analysis (OSRA) model (Smith et al., 1982); 

(2) the probability of oil-spill occurrence, which is based on spill rates derived from 

historical data (Anderson et al., 2012) and on estimated volumes of oil produced 

and transported; and

(3) the combination of results of the first two to estimate the overall oil-spill risk if 

there is oil development.

The OSRA model simulates the trajectory of thousands of spills throughout the Gulf of 

Mexico OCS and calculates the probability of these spills being transported and contacting specified 

geographic areas and features. Using the OSRA model, BOEM estimates the likely trajectories of 
Impact-Producing Factors and Scenario 3-33

hypothetical offshore spills ≥1,000 bbl. Only spills ≥1,000 bbl are addressed because smaller spills 

may not persist long enough to be simulated by trajectory modeling. For this analysis, the OSRA 

model was run for Alternatives A, B, and C, and the Cumulative OCS Oil and Gas Program 

(2017-2086). In the GOM, the Cumulative OCS Oil and Gas Program scenario comprises all future 

operations that would occur over a 70-year time period (2017-2086) from existing leases from 

previous lease sales, currently proposed lease sales within the Five-Year Program, and future 

proposed regionwide lease sales.

Figure 3-7. The Oil Spill Risk Analysis Model Process.

The mean number of spills estimated to occur as a result of each alternative is provided in 

Table 3-10. The range of the mean number of spills reflects the range of oil production volume 

estimated as a result of each alternative. The mean number of future spills ≥1,000 bbl is calculated 

by multiplying the spill rate by the volume of oil estimated to be produced as a result of each 

alternative. Spill rates were calculated based on the assumption that spills occur in direct proportion 

to the volume of oil handled and are expressed as number of spills per billion barrels of oil handled 

(spills/BBO).
3-34 2018 Gulf of Mexico Supplemental EIS

Table 3-10. Mean Number and Sizes of Spills Estimated to Occur in OCS Offshore Waters from an 

Accident Related to Rig/Platform and Pipeline Activities Supporting Each Alternative Over a 

50-Year Time Period.

Spill Size Group Spill Rate

(spills/BBO)1

Number of Spills Estimated Estimated

Median Spill 

Size 

(bbl)1

Alternative A Alternative B Alternative C

0-1.0 bbl 2,020 424-2,258 374-1,959 51-290 <1

1.1-9.9 bbl 57.4 12-64 11-56 2-9 3 10.0-49.9 bbl 17.4 4-20 3-17 1-3

50.0-499.9 bbl 11.3 2-13 2-11 <1-2 126 500.0-999.9 bbl 1.63 <1-2 <1-2 <1

Platforms

>1,000-9,999 bbl 0.25 <1 <1 <1 5,066

>10,000 bbl 0.13 <1 <1 <1 –2

Pipelines

>1,000-9,999 bbl 0.88 <1-1 <1 <1 1,720

>10,000 bbl 0.18 <1 <1 <1 –2

Notes: The number of spills estimated is derived by application of the historical rate of spills 

(1996-2010) per volume of crude oil handled based on the projected production for each 

alternative (Table 3-3). The actual number of spills that may occur in the future could vary 

from the estimated number.

1

The spill rates presented are a sum of rates for United States OCS platforms/rigs and pipelines. The 

average (vs. the median) spill sizes for a larger number of spill size categories can also be found in the 

original source (Anderson et al., 2012).

2

During the last 15 years, the only platform- or pipeline-related spill ≥10,000-bbl was the Deepwater 

Horizon. However, this spill is considered to be a low-probability catastrophic event, which is not 

reasonably foreseeable and is therefore not included.

The probabilities for oil-spill occurrence resulting from each alternative (2017-2066) and the 

Cumulative OCS Oil and Gas Program (2017-2086) for offshore spills ≥1,000 bbl can be found in 

Table 3-11 and for spills ≥10,000 bbl in Table 3-12. The OSRA model estimates the chance of oil 

spills occurring during the production and transportation of a specific volume of oil over the lifetime of 

the scenario being analyzed. The estimation process uses a spill rate constant, based on historical 

accidental spills ≥1,000 bbl and ≥10,000 bbl, expressed as a mean number of spills per billion 

barrels of oil handled. For this analysis, the low estimate and high estimate of projected oil 

production for a single proposed lease sale for each alternative and for the Cumulative OCS Oil and 

Gas Program (2017-2086) are used. For more information on OCS spill-rate methodologies and 

trends, refer to Anderson et al. (2012). A discussion of how the range of resource estimates was 

developed is provided in Chapter 3.1.2 and Table 3-6.
Impact-Producing Factors and Scenario 3-35

Table 3-11. Oil-Spill Occurrence Probability Estimates for Offshore Spills ≥1,000 Barrels Resulting from 

Each Alternative (2017-2066) and the Cumulative OCS Oil and Gas Program (2017-2086).

Forecasted Oil 

Production 

(Bbbl)1

Mean Number of Spills Estimated to Occur Estimates of Probability (% chance) 

of One or More Spills

Platforms Pipelines Tankers Total Platforms Pipelines Tankers Total

Single Proposed Lease Sale Alternatives

Alternative A2 0.210 0.05 0.19 0 0.24 5 17 <0.5 21

1.118 0.28 0.98 0.01 1.27 24 63 <0.5 72

Alternative B3 0.185 0.05 0.16 0 0.21 5 15 <0.5 19

0.970 0.24 0.85 0 1.10 22 57 <0.5 67

Alternative C4 0.026 0.01 0.02 0 0.03 1 2 <0.5 3

0.148 0.04 0.13 0 0.17 4 12 <0.5 15

Cumulative OCS Oil and Gas Program

Regionwide 15.482 3.87 13.62 0.08 17.57 98 >99.5 7 >99.5

25.806 6.45 22.71 0.13 29.29 >99.5 >99.5 12 >99.5

CPA/EPA 13.590 3.40 11.96 0.07 15.42 97 >99.5 7 >99.5

22.381 5.60 19.70 0.11 25.40 >99.5 >99.5 11 >99.5

WPA 1.892 0.47 1.66 0 2.14 38 81 <0.5 88

3.425 0.86 3.01 0 3.87 58 95 <0.5 98

Notes: Bbbl = billion barrels.

“Platforms” refers to facilities used in exploration, development, or production. 1

Values represent the low and high resource estimates. Refer to Table 3-1 for more information on resource estimates. 2

Regionwide proposed lease sale.

3

Regionwide proposed lease sale excluding blocks in the WPA.

4

Regionwide proposed lease sale excluding blocks in the CPA/EPA.

Source: Ji, official communication, 2015.

Table 3-12. Oil-Spill Occurrence Probability Estimates for Offshore Spills ≥10,000 Barrels Resulting from 

Each Alternative (2017-2066) and the Cumulative OCS Oil and Gas Program (2017-2086).

Forecasted Oil 

Production 

(Bbbl)1

Mean Number of Spills Estimated to Occur Estimates of Probability (% chance)

of One or More Spills

Platforms Pipelines Tankers Total Platforms Pipelines Tankers Total

Single Sale Alternatives

Alternative A2 0.210 0.03 0.04 0 0.07 3 4 <0.5 6

1.118 0.15 0.20 0 0.35 14 18 <0.5 29

Alternative B3 0.185 0.02 0.03 0 0.06 2 3 <0.5 6

0.970 0.13 0.17 0 0.30 12 13 <0.5 26

Alternative C4 0.026 0 0 0 0.01 <0.5 <0.5 <0.5 1

0.148 0.02 0.03 0 0.05 2 3 <0.5 4

Cumulative OCS Oil and Gas Program

Regionwide 15.482 2.01 2.79 0.02 4.82 87 94 2 99

25.806 3.35 4.65 0.04 8.04 97 99 4 >99.5

CPA/EPA 13.590 1.77 2.45 0.02 4.23 83 91 2 99

22.381 2.91 4.03 0.04 6.97 95 98 4 >99.5

WPA 1.892 0.25 0.34 0 0.59 22 29 <0.5 44

3.425 0.45 0.62 0 1.06 36 46 <0.5 65
3-36 2018 Gulf of Mexico Supplemental EIS

Forecasted Oil 

Production 

(Bbbl)1

Mean Number of Spills Estimated to Occur Estimates of Probability (% chance)

of One or More Spills

Platforms Pipelines Tankers Total Platforms Pipelines Tankers Total

Notes: Bbbl = billion barrels.

“Platforms” refers to facilities used in exploration, development, or production. 1

Values represent the low and high resource estimates. Refer to Table 3-1 for more information on resource estimates. 2

Regionwide proposed lease sale.

3

Regionwide proposed lease sale excluding blocks in the WPA.

4

Regionwide proposed lease sale excluding blocks in the CPA/EPA.

Source: Ji, official communication, 2015.

Analysis of Offshore Spills <1,000 bbl

The number of spills <1,000 bbl estimated to occur over the next 50 years as a result of each 

alternative is provided in Table 3-10. The number of spills is estimated by multiplying the oil-spill 

rate for each of the different spill size groups by the projected oil production as a result of each 

alternative (Tables 3-1 and 3-7). As spill size increases, the occurrence rate decreases and so the 

number of spills estimated to occur decreases.

Analysis of Coastal Spills

Spills that occur in State offshore waters and/or navigation channels, rivers, and bays 

(coastal waters) from barges and pipelines carrying OCS-produced oil are referred to as coastal 

spills. These spills occur at shoreline storage, processing, and transport facilities supporting the 

OCS oil and gas industry. BOEM projects that most (>90%) oil produced as a result of a proposed 

action under Alternative A would be brought ashore via pipelines to oil pipeline shore bases, stored 

at these facilities, and eventually transferred via pipeline or barge to GOM 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.

According to USCG’s database for the most recent 13 years (i.e., January 2002-July 2015) 

(USDHS, CG, 2016) (Table 3-13) in the waters 0-9 nmi (0-10.36 mi; 16.67 km) off the Texas coast, 

there were a total of 91 spills reported from 2002 to 2015 or about 7 spills <1,000 bbl/yr. In the 

waters 0-3 nmi (0-3.45 mi; 5.56 km) off the Louisiana coast, there were a total of more than 

2,143 spills reported from 2002 to 2015, or about 165 spills <1,000 bbl/yr. In the waters 0-3 nmi 

(0-3.45 mi; 5.56 km) off the Mississippi coast, there were a total of 42 spills reported from all 

sources, or about 3.2 spills <1,000 bbl/yr. In the waters 0-3 nmi (0-3.45 mi; 5.56 km) off the 

Alabama coast, there were a total 2 spills reported from all sources from 2002 to 2015, or about 

0.2 spills <1,000 bbl/yr. In the waters 0-9 nmi (0-10.36 mi; 16.67 km) off the Florida coast, there 

were a total 0 spills reported from all sources from 2002 to 2015. When limited to just oil- and 

gas-related spill sources such as platforms, pipelines, MODUs, and support vessels, 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 energy-related commercial and recreational 

activities remain the same. The coastal waters of Louisiana, Texas, Mississippi, Alabama, and 
Impact-Producing Factors and Scenario 3-37

Florida have had a total of 165, 7, 3.2, 0.2, and 0, spills <1,000 bbl/yr, respectively. Assuming future 

trends would reflect past historical records, it is also predicted that Louisiana will be the state most 

likely to have a spill ≥1,000 bbl occur in water 0-3 mi (0-5 km) offshore. Between 2002 and 2015, 

only two spills ≥1,000 bbl occurred in coastal waters (refer to Table 3-13 below), and those occurred 

in the coastal waters of Louisiana. 

Table 3-13. Historic Spill Source, Location, and Characteristics of a Maximum Spill for Coastal Waters1

(data extracted from USDHS CG records, 2002-July 2015).

Source

Number of Spills Maximum Volume of a Single Incident

Total 

Number of 

Spill Events

Number 

of Spills 

(<1,000 bbl)

Number 

of Spills 

(≥1,000 bbl)

Volume (bbl) of 

Maximum Spill 

from the Source 

Maximum Spill Amount 

Product/Year

Western Planning Area (WPA)2

Fixed Platform 147 147 0 7.62 Crude/2005

Pipeline 0 0 0 N/A N/A

MODU 2 2 0 4 Crude/2002

OSV 1 1 0 0.05 Crude/2014

Tank Ship or 

Barge 5 5 0 23.8 Crude/2009

Total 155 155 0 – –

Central Planning Area (CPA)2

Fixed Platform 2,398 2,398 0 300 Crude/2004

Pipeline 4 4 0 5 Crude/2002

MODU 28 27 1 4,928,100 Crude/2010

OSV 7 7 0 0.07 Crude 2014

Tank Ship or 

Barge 6 6 0 2 Crude/2013

Total 2,443 2,442 1 – –

Eastern Planning Area (EPA)2

Fixed Platform 0 0 0 N/A N/A

Pipeline 0 0 0 N/A N/A

MODU 0 0 0 N/A N/A

OSV 0 0 0 N/A N/A

Tank Ship or 

Barge 0 0 0 N/A N/A

Total 0 0 0 – –
3-38 2018 Gulf of Mexico Supplemental EIS

Source

Number of Spills Maximum Volume of a Single Incident

Total 

Number of 

Spill Events

Number 

of Spills 

(<1,000 bbl)

Number 

of Spills 

(≥1,000 bbl)

Volume (bbl) of 

Maximum Spill 

from the Source 

Maximum Spill Amount 

Product/Year

Coastal Waters: Texas

Fixed Platform 67 67 0 20 Crude/2002

Pipeline 14 14 0 10 Crude/2005

MODU 5 5 0 0.48 Crude/2002

OSV 2 2 0 0.05 Crude/2003

Tank Ship or 

Barge 3 3 0 0.36 Crude/2009

Total 91 91 0 – –

Coastal Waters: Louisiana

Fixed Platform 2,022 2,021 1 1,200 Crude/2008

Pipeline 98 97 1 7,000 Crude/2008

MODU 4 4 0 0.24 Crude/ 2013

OSV 17 17 0 3 Crude/2013

Tank Ship or 

Barge 2 2 0 50 Crude/2002

Total 2,143 2,141 2 – –

Coastal Waters: Mississippi

Fixed Platform 1 1 0 0.001 Crude/2008

Pipeline 0 0 0 N/A NA

MODU 0 0 0 N/A N/A

OSV 0 0 0 N/A N/A

Tank Ship or 

Barge 1 1 0 0.05 Crude/2002

Total 2 2 0 – –

Coastal Waters: Alabama

Fixed Platform 2 2 0 0.024 Crude/2007

Pipeline 0 0 0 N/A N/A

MODU 0 0 0 N/A N/A 

OSV 0 0 0 N/A N/A

Tank Ship or 

Barge 0 0 0 N/A N/A

Total 2 2 0 – –
Impact-Producing Factors and Scenario 3-39

Source

Number of Spills Maximum Volume of a Single Incident

Total 

Number of 

Spill Events

Number 

of Spills 

(<1,000 bbl)

Number 

of Spills 

(≥1,000 bbl)

Volume (bbl) of 

Maximum Spill 

from the Source 

Maximum Spill Amount 

Product/Year

Coastal Waters: Florida

Fixed Platform 0 0 0 N/A N/A

Pipeline 0 0 0 N/A N/A

MODU 0 0 0 N/A N/A

OSV 0 0 0 N/A N/A

Tank Ship or 

Barge 0 0 0 N/A N/A

Total 0 0 0 – –

bbl = barrel; MODU = mobile offshore drilling unit; N/A = not applicable; OSV = offshore support vessel.

Note: The reader should note that the spills are reported to USCG by responsible parties, other private 

parties, and government personnel. The USCG does not verify the source or volume of every 

report.

1

Coastal Waters – the portion of the Gulf of Mexico under State jurisdiction that begins at the coastline 

and ends at the Federal/State boundary 9 nmi (10.36 mi; 16.67 km) offshore Texas; 3 nmi (3.5 mi; 

5.6 km) offshore Louisiana, Mississippi, and Alabama; and 9 nmi (10.36 mi; 16.67 km) offshore West 

Florida. 2

The database included represents spill events from January 2002 until July 2015.

3.2.3 What is the Response to Accidental Events?

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. It is likely that larger spills under the 

right conditions would require the simultaneous use of all available cleanup methods (i.e., source 

containment, mechanical spill containment and cleanup, dispersant application, and in-situ burning). 

There are many situations and environmental conditions that necessitate different approaches. Spill 

cleanup is a complex and evolving technology. Each new tool then becomes part of the 

spill-response tool kit. Each spill-response technique/tool has its specific uses and benefits (Fingas, 

1995). Offshore removal and spill-containment efforts to respond to an ongoing spill offshore would 

likely require multiple technologies, including source containment, mechanical spill containment and 

cleanup, in-situ burning of the slick, and the use of 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 can be contained and removed offshore.

The sensitivity of the contaminated shoreline is the most important factor in the development 

of cleanup recommendations. Shorelines of low productivity and biomass can withstand more 

intrusive cleanup methods such as pressure washing. Shorelines of high productivity and biomass 

are very sensitive to intrusive cleanup methods and, in many cases, the cleanup is more damaging 

than allowing natural recovery. Refer to Chapter 3.2.8 of the 2017-2022 GOM Multisale EIS for 

more information on specific spill-response techniques. For information on the effects of 

spill-response activity, refer to Chapter 4 of the 2017-2022 GOM Multisale EIS.
3-40 2018 Gulf of Mexico Supplemental EIS

Within BSEE, the Oil Spill Preparedness Division addresses all aspects of oil-spill planning 

and preparedness. Additional information about the Oil Spill Preparedness Division can be found on 

BSEE’s website at http://www.bsee.gov/About-BSEE/Divisions/OSPD/index/. BOEM receives and 

reviews the worst-case discharge information submitted for EPs, development and production plans 

(DPPs), and DOCDs on the OCS. BOEM also has regulatory requirements addressing site-specific, 

oil-spill response plans (OSRPs). As required by BOEM at 30 CFR §§ 550.219 and 550.250, 

operators are required to provide BOEM with 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. Refer to Chapter 3.2.8 of the 2017-2022 GOM Multisale EIS for more information.

3.2.4 Summary of Accidental Impact-Producing Factors

Table 3-14 below outlines the impact-producing factors from initial exploration to 

decommissioning for accidental oil and gas events. Table 3-15 provides a general description of all 

accidental events that could occur during the lifetime of a lease.

Table 3-14. Summary of the Timing of Impact-Producing Factors Associated with Accidental Oil and 

Gas Events.

Impact-Producing Factors 

and Activities

Exploration

Development Production Decommissioning

Geological 

and 

Geophysical 

Survey

Exploration 

and 

Delineation 

Drilling

Oil Spills – X X X X

 Offshore Spills ≥1,000 bbl – X X X X

 Offshore Spills <1,000 bbl – X X X X

 Coastal Spills X X X X X

Loss of Well Control - X X X X

Accidental Air Emissions X X X X X

Pipeline Failures - X X X X

Vessel or Helicopter Collisions X X X X X

Chemical and Drilling Fluid 

Spills X X X X X 

Wastes and Debris X X X X X

Spill Response* X X X X X

*Spill response can occur as a result of chemical or fuel spills as well as oil spills.
 

Impact-Producing Factors and Scenario

3-41

Table 3-15. General Description of Accidental Event Impact-Producing Factors.

 

Multisale EIS 

Chapter 

Reference

General Description

Oil Spills 3.2.1

As a consequence of activities related to the exploration, development, production, and transportation of oil and gas, the 

potential for accidental releases exists. Petroleum spills include crude oil, condensate, and refined products such as 

diesel, hydraulic oil, lube oil and mineral oil. Spills from facilities include drilling rigs, drillships, and storage, processing, or 

production operations, while spills from pipelines are those that occur on the OCS and are directly attributable to the 

transportation of OCS oil. BOEM uses the Oil Spill Risk Analysis (OSRA) model to simulate the trajectory of thousands of 

hypothetical spills ≥1,000 bbl throughout the Gulf of Mexico OCS and calculates the probability of these spills being 

transported and contacting specified geographic areas and features. Additionally, the OSRA model calculates combined 

probabilities by multiplying the probability of contact by the probability of a spill occurring as a result of a proposed action. 

A more thorough discussion of oil spills and the OSRA model can be found in the chapters above and in Chapter 3.2.1 of 

the 2012-2022 GOM Multisale EIS.

Loss of Well 

Control 3.2.2

Operators are required to document any loss of well control event, even if temporary, and the cause of the event by mail 

or email to the addressee indicated in NTL 2010-N05. The operator does not have to include kicks that were controlled 

but 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.

Not all loss of well control events would result in a blowout as defined above. A loss of well control is most commonly 

thought of as a release to the human environment. A loss of well control can occur during any phase of development, i.e., 

exploratory drilling, development drilling, well completion, production, or workover operations. A loss of well control can 

occur when improperly balanced well pressure results in sudden, uncontrolled releases of fluids from a wellhead or 

wellbore (PCCI Marine and Environmental Engineering, 1999; Neal Adams Firefighters, Inc., 1991). Of the 48 loss of well 

control events reported in the GOM from 2007 to August 2015, 25 (52%) resulted in loss of fluids at the surface or 

underground (USDOI, BSEE, 2016a).

Accidental Air 

Emissions 3.2.3

Accidental events associated with offshore oil- and gas-related activities can result in the emission of air pollutants. These 

OCS oil- and gas-related accidental events could include the release of oil, condensate, or natural gas; chemicals used 

offshore; pollutants from the burning of these products; fire; or H2S release. The air pollutants could include National Air 

Ambient Quality Standards criteria pollutants, volatile and semi-volatile organic compounds, hydrogen sulfide, and 

methane. Emissions sources related to accidents from OCS operations can include well blowouts, oil spills, pipeline 

breaks, tanker accidents, and tanker explosions.

Pipeline Failures 3.2.4

Significant sources of damages to OCS pipeline infrastructure can be caused by corrosion (Chapters 3.1.3.3.1 and 3.1.6.1

of the 2012-2022 GOM Multisale EIS), physical pipeline stress due to location, mass sediment movements and mudslides 

that can exhume or push the pipelines into another location, and accidents due to weather or impacts from anchor drops 

or boat collisions.

Vessel or 

Helicopter 

Collisions

3.2.5

From 2007 to 2014, there were 137 OCS oil- and gas-related vessel collisions (USDOI, BSEE, 2015). Most collision 

mishaps are the result of service vessels colliding with platforms or vessel collisions with pipeline risers. Approximately 

10% of vessel collisions with platforms in the OCS caused diesel spills. Fires resulted from hydrocarbon releases in 

several of the collision incidents.
Table 3-15. General Description of Accidental Event Impact-Producing Factors. (continued). 3-42 2018 Gulf of Mexico Supplemental EIS

 

Multisale EIS 

Chapter 

Reference

General Description

The average number of helicopter accidents per year in the GOM since 1984 has been 7.9 per year, with the last 10 years 

averaging 4.7 per year and with only 2 in 2014. The 2014 GOM oil industry helicopter accident rate per 100,000 flight 

hours was 0.68, with a total of 2 accidents compared with a 31-year annual average accident rate of 1.74. The fatal 

accident rate per 100,000 flight hours during 2014 was 0.34 compared with a 31-year average of 0.44 (Helicopter Safety 

Advisory Conference, 2015).

Chemical and 

Drilling Fluid 

Spills

3.2.6

Chemicals and synthetic-based drilling fluids are used in offshore oil and gas drilling and production activities, and may be 

spilled to the environment due to equipment failure, weather (i.e., wind, waves, and lightning), accidental collision, and 

human error.

Wastes and 

Debris 3.2.7

The BSEE policy regarding marine debris prevention is outlined in NTL 2015-BSEE-G03, “Marine Trash and Debris 

Awareness and Elimination.” This NTL instructs OCS operators to post informational placards that outline the legal 

consequences and potential ecological harms of discharging marine debris

Spill Response

BSEE-Spill 

Response 

Requirements

3.2.8.1

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, BSEE was tasked with a number of oil-spill response duties and 

planning requirements. Within BSEE, the Oil Spill Preparedness Division addresses all aspects of offshore oil-spill 

planning, preparedness, and response. Additional information about the Oil Spill Preparedness Division can be found on 

BSEE’s website at http://www.bsee.gov/About-BSEE/Divisions/OSPD/index/. The BSEE implements the following 

regulations according to 30 CFR parts 250 and 254:

• requires immediate notification for spills >1 bbl—all spills require notification to USCG, and BSEE receives 

notification from 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;

• sets requirements and reviews and approves OSRPs for offshore facilities (More information on oil-spill response 

plan regulations and processes can be found in Appendix A.5 of the 2017-2022 GOM Multisale EIS.); 

• conducts unannounced drills to ensure compliance with OSRPs;

• requires operators to ensure that their spill-response operating and management teams receive appropriate spillresponse 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.

Offshore 

Response 3.2.8.2 It is likely that larger spills under the right conditions would require the simultaneous use of all available cleanup methods

(i.e., source containment, mechanical spill containment and cleanup, dispersant application, and in-situ burning).

Onshore 

Response 3.2.8.3

Offshore response and cleanup is preferable to shoreline cleanup; however, if an oil slick reaches the coastline, it is 

expected that the specific shoreline cleanup countermeasures identified and prioritized in the appropriate Area 

Contingency Plans for various habitat types would be used. The sensitivity of the contaminated shoreline is the most 

important factor in the development of cleanup recommendations. Shorelines of low productivity and biomass can 

withstand more intrusive cleanup methods such as pressure washing. Shorelines of high productivity and biomass are 

very sensitive to intrusive cleanup methods and, in many cases, the cleanup is more damaging than allowing natural 

recovery.
Impact-Producing Factors and Scenario 3-43

3.3 CUMULATIVE IMPACTS

3.3.1 What Activities, Not Considered a Part of a Proposed Action, has BOEM 

Considered?

A cumulative impact “results from the incremental impact of [an] action 

when added to other past, present, and reasonably foreseeable future actions, 

regardless of what agency (Federal or non-Federal) or person undertakes such 

other actions” (40 CFR § 1508.7). The scope of a proposed action is important 

to consider in a broader context that accounts for the full range of actions and 

associated impacts taking place within the Gulf of Mexico, currently and into the 

foreseeable future. Repeated actions, even minor ones, may produce 

significant impacts over time.

The cumulative impacts assessment focuses on the resources, ecosystems, and human 

communities that may be affected by the incremental impacts associated with a proposed action 

(under any of the action alternatives), in combination with other past, present, and reasonably 

foreseeable future actions. Cumulative impacts on a given resource, ecosystem, or human 

community may result from single actions or a combination of multiple actions over time. They may 

be additive, less than additive (countervailing), or more than additive (synergistic).

Many of the past, present, and reasonably foreseeable future actions and trends that 

would contribute to cumulative impacts under a proposed action’s alternatives also contribute to 

cumulative impacts under the No Action Alternative (Alternative E). Under Alternative E, a 

proposed action (i.e., a single proposed OCS oil and gas lease sale) would not occur and, as a 

result, energy could be obtained from other sources to replace the lost oil and gas production. The 

opportunity for development of the estimated oil and gas that could have resulted from a proposed 

action (i.e., a single proposed lease sale) or alternative to a proposed action, as described above, 

would be precluded or postponed to a future lease sale. As a result, a separate treatment of the 

cumulative effects under Alternative E is not considered here.

3.3.2 Summary of Cumulative Activities

3.3.2.1 Cumulative OCS Oil and Gas Program Scenario

The Cumulative OCS Oil and Gas Program scenario includes all activities (i.e., routine 

activities projected to occur and accidental events that could occur) from past, proposed, and future 

lease sales. This includes projected activity from (1) past lease sales for which exploration or 

development has either not yet begun or is continuing; (2) lease sales that would be held in the 

2017-2022 Five-Year Program; and (3) future lease sales that would be held as a result of future 

Five-Year Programs (4 additional programs are included in this cumulative analysis). This equates 

to a 70-year timeframe or 2017-2086 and includes a 50-year analysis period (2017-2066) for a single 

proposed lease sale (e.g., Lease Sale 250). Activities that take place as a result of Five-Year 

Programs beyond the next four programs are not included in this analysis.
3-44 2018 Gulf of Mexico Supplemental EIS

It is reasonably foreseeable to assume that lease sales would continue to be proposed for 

many years to come in the Gulf of Mexico region based on resource availability, existing 

infrastructure, and projected time lapses required for any other major energy sources to come 

online. For the purposes of conducting cumulative impact analyses here, even though additional 

NEPA reviews would be required, four additional Five-Year Programs are assumed to occur (an 

additional 20 years of proposed lease sales), resulting in activities that could occur over the next 

70 years. However, the level of activities (i.e., exploration wells, production wells, and pipelines) 

becomes more speculative as time is projected into the future. The causes for this are a number of 

things, including uncertainty in oil prices, resource potential, and cost of development and resource 

availability (e.g., drilling rig availability) versus the amount of acreage leased from a lease sale.

Therefore, these scenarios do not predict future OCS oil- and gas-related activities with 

absolute certainty, even though they were formulated using historical information and current trends 

in the oil and gas industry. These scenarios are only approximate since future factors such as the 

contemporary economic marketplace, the availability of support facilities, and pipeline capacities are 

all unknowns. Notwithstanding these unpredictable factors, the scenarios used in this Supplemental 

EIS represent the best assumptions and estimates of a set of future conditions that are considered 

reasonably foreseeable and suitable for presale impact analyses. The development scenarios do 

not represent BOEM’s recommendation, preference, or endorsement of any level of leasing or 

offshore operations, or of the types, numbers, and/or locations of any onshore operations or facilities 

for future programs. Methodologies for the Cumulative OCS Oil and Gas Program scenario are 

similar to those for a regionwide or individual planning area typical lease sale scenario analysis and 

are described in detail in Chapter 3.0 above. Tables 3-16 and 3-17 present projections of the major 

activities and impact-producing factors related to future Cumulative OCS Oil and Gas Program 

activities.

Table 3-16 Future Activity Projections Associated with the Cumulative OCS Oil and Gas Program 

(2017-2086), Including All Future Activities that are Projected to Occur from Past, Proposed, 

and Future Lease Sales.

Activity Planning 

Area

Offshore Subareas (m)1

Totals2

0-60 60-200 200-800 800-

1,600

1,600-

2,400 >2,400

Exploration 

and 

Delineation 

Wells

GOM 939-2,562 253-1,166 110-170 153-240 97-278 119-301 1,671-4,717

CPA/EPA 775-1,999 202-1,007 83-142 88-184 70-142 99-211 1,317-3,685

WPA 164-563 51-159 27-28 65-56 27-136 20-90 354-1,032

Development 

and 

Production 

Wells3

G

O

M

Total 4,050-9,225 1,570-4,324 912-2,034 617-1,127 446-723 633-985 8,238-18,418

Oil 438-987 164-453 446-993 280-487 230-372 310-482 1,868-3,774

Gas 2,440-5,566 894-2,457 186-415 149-288 79-126 126-194 3,874-9,046

C

P

A/

E

P

A

Total 3,170-6,634 1,139-3,558 676-1,557 490-779 405-623 595-899 6,475-14,050

Oil 354-740 122-379 326-750 240-385 207-319 289-437 1,538-3,010

Gas 1,898-3,972 645-2,015 142-327 95-152 72-110 119-179 2,971-6,755
Impact-Producing Factors and Scenario 3-45

Activity Planning 

Area

Offshore Subareas (m)1

Totals2

0-60 60-200 200-800 800-

1,600

1,600-

2,400 >2,400

W

P

A

Total 880-2,591 431-766 236-477 137-348 41-100 38-86 1,763-4,368

Oil 84-247 42-74 120-243 40-102 23-53 21-45 330-764

Gas 542-1,594 249-442 44-88 54-136 7-16 7-15 903-2,291

Installed 

Production 

Structures

GOM 2,168-5,121 558-1,638 36-71 26-38 16-38 23-42 2,827-6,948

CPA/EPA 1,760-3,682 432-1,347 23-54 17-26 14-21 20-30 2,266-5,160

WPA 408-1,439 126-291 13-17 9-12 2-17 3-12 561-1,788

Production 

Structures 

Removed 

Using 

Explosives

GOM 2,435-4,388 568-1,310 0 0 0 0 3,003-5,698

CPA/EPA 2,051-3,315 440-1,065 0-0 0-0 0-0 0-0 2,491-4,380

WPA 384-1,073 128-245 0-0 0-0 0-0 0-0 512-1,318

Total 

Production 

Structures 

Removed

GOM 3,381-6,148 784-1,796 39-69 36-44 20-33 21-31 4,281-8,121

CPA/EPA 2,847-4,639 608-1,459 26-54 25-31 17-22 18-24 3,541-6,229

WPA 534-1,509 176-337 13-15 11-13 3-11 3-7 740-1,892

Length of 

Installed 

Pipelines 

(km)4

GOM 2,181-15,822 1,432-

10,511 1,078-8,037 1,268-8,265 700-7,001 704-7,359 7,363-56,995

CPA/EPA 586-11,799 388-8,355 328-6,390 385-6,381 364-6,168 405-6,750 2,456-45,843

WPA 1,595-4,023 1,044-2,156 750-1,647 883-1,884 336-833 299-609 4,907-11,152

ServiceVessel Trips 

(1,000’s 

round trips)

GOM 2,443-6,998 645-2,300 284-942 213-556 134-498 187-577 3,909-11,873

CPA/EPA 1,978-5,037 496-1,892 186-722 140-389 115-306 163-440 3,079-8,788

WPA 465-1,960 150-408 98-221 72-167 19-192 23-137 830-3,085

Helicopter 

Operations 

(1,000’s 

round trips)

GOM 11,714-55,063 4,511-25,155 270-1,162 183-651 139-422 183-546 17,000-83,000

CPA/EPA 9,614-40,734 3,544-21,159 191-898 148-440 121-352 165-475 13,786-64,059

WPA 2,098-14,329 966-3,996 78-264 34-211 17-70 17-70 3,214-18,941

1

Refer to Figure 3-1. 2

Subareas totals may not add up to the planning area total because of rounding.

3

Development and Production Wells include some exploration wells that were re-entered and completed. These wells 

were removed from the Exploration and Delineation well count.

4

Projected length of pipelines does not include length in State waters.
3-46 2018 Gulf of Mexico Supplemental EIS

Table 3-17. Future Oil Transportation Projections Associated with the Cumulative OCS Oil and Gas 

Program (2017-2086), Including All Future Transportation that is Projected to Occur from 

Past, Proposed, and Future Lease Sales.

Activity Region

Offshore Subareas (m)1

Totals2

0-60 60-200 200-800 800-

1,600

1,600-

2,400 >2,400

Percent 

Oil Piped3

GOM 94-95% 100% 100% 100% 89.6-87.4% 87.4-85.7% 91.6-90.6%

CPA/EPA 94-95% 100% 100% 100% 97.8-96.3% 94.9-95.3% 90.8-91.0%

WPA 100% 100% 100% 100% 100-89% 100-86.4% 100-95.1%

Percent 

Oil Barged

GOM 6-5% 0% 0% 0% 0% 0% 0.2%

CPA/EPA 6-5% 0% 0% 0% 0% 0% 0.2%

WPA 0% 0% 0% 0% 0% 0% 0%

Percent 

Tankered4

GOM 0% 0% 0% 0% 10.4-12.6% 12.6-14.3% 8-9%

CPA/EPA 0% 0% 0% 0% 12.2-13.7% 5.1-4.7% 9-8.75%

WPA 0% 0% 0% 0% 0-11% 0-13.6% 0-4.85% 1

Refer to Figure 3-1. Ranges are reported from the low production case scenario to the high production case 

scenario.

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 (5,249 ft). 

3.3.2.2 Non-OCS Oil- and Gas-Related Impact-Producing Factors

The impact-producing factors considered in this chapter are defined as other past, present, 

and reasonably foreseeable future activities occurring within the same geographic range and within 

the same timeframes as the aforementioned projected routine activities and potential accidental 

events, but they are not related to the Cumulative OCS Oil and Gas Program. Table 3-18 below 

summarizes other impact-producing factors that could potentially affect an environmental or 

socioeconomic resource in addition to OCS oil- and gas-related activity.

While the scenario developed for the Cumulative OCS Oil and Gas Program scenario 

forecasts 70 years of activities, the scenarios developed as part of this chapter vary in the length of 

time projected depending on what would be considered reasonably foreseeable by impact-producing 

factors based on the data available and the ability to predict future actions without being speculative.
Impact-Producing Factors and Scenario

3-47

Table 3-18. General Description of Cumulative Non-OCS Oil- and Gas-Related Impact-Producing Factors.

Impact-Producing 

Factor and 

Specific Sources

Multisale EIS 

Chapter 

Reference

General Description

State Oil and Gas Activity

State Oil and Gas 

Activity 3.3.2.1

All of the five Gulf Coast States have had some historical oil and gas exploration activity and, with the exception of 

Florida and Mississippi, all 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 plants for further processing, and additional 

pipelines that transport finished product to points of storage and final 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.

Pipeline 

Infrastructure 3.3.2.1.1

The existing pipeline network in the Gulf Coast States is the most extensive in the world and has unused capacity 

(Cranswick, 2001). 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. However, there 

is spare capacity in the existing pipeline infrastructure to move oil and gas to market, and deepwater ports can serve 

onshore facilities, including intrastate as well as interstate pipelines.

Artificial Reefs 3.3.2.1.2

The OCSLA and implementing regulations establish decommissioning obligations for lessees, including the removal of 

platforms. The Rigs-to-Reefs Policy provides a means by which lessees may request a waiver to the removal 

requirement. For additional information, refer to Chapter 3.1.6.2 of the 2017-2022 Gulf of Mexico Multisale EIS. Since 

the first Rigs-to-Reefs conversion, approximately 11% of the platforms decommissioned from the Gulf of Mexico OCS 

have been redeployed within designated State artificial reefs. Scientific and public interest in the ecology of offshore 

structures and the potential benefits of contributing hard substrate to a predominantly soft bottom environment have led 

to increased emphasis on the development of artificial reefs. The current paradigm posits oil and gas 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; Dance et al., 2011). However, determination of specific and cumulative impacts 

resulting from the construction of artificial reefs within permitted areas is very difficult. As recommended by the National

Artificial Reef Plan (USDOC, NOAA, 2007), well-defined objectives, clear management strategies, and long-term 

monitoring are critical elements of an artificial reef program and are necessary if managers intend to use artificial reefs 

as a fisheries management tool.

Marine Vessel Activity

Marine 

Transportation 3.3.2.2

Non-OCS oil- and gas-related vessels, other than above, utilize the GOM. These ships include research, recreational,

and commercial vessels. Commercial and recreational fishing in the Gulf of Mexico are regulated by NMFS. For more 

information on recreational fishing vessels, refer to Chapter 4.11 of the 2017-2022 GOM Multisale EIS. For more 

information on commercial fishing vessels, refer to Chapter 4.10 of the 2017-2022 GOM Multisale EIS. Research 

activities, including surveys, genetic research, capture, relocation, or telemetric monitoring, may affect organisms or 

ecosystems in the GOM. The OCS oil- and gas-related vessels are required to survey for undiscovered archaeological 

and biological resources; however, these resources may be damaged by anchors of non-OCS oil- and gas-related 

vessels that do not perform surveys. Non-OCS oil- and gas-related tankering includes ships carrying crude or ships
Table 3-18. General Description of Cumulative Non-OCS Oil- and Gas-Related Impact-Producing Factors. (continued). 3-48 2018 Gulf of Mexico Supplemental EIS

Impact-Producing 

Factor and 

Specific Sources

Multisale EIS 

Chapter 

Reference

General Description

carrying product. Overall, tankering (including U.S. ships and foreign ships) in the U.S. increased by 28% between 2003 

and 2011 (USDOT, MARAD, 2013). While U.S. tankering port of calls declined between 2003 and 2011, foreign ship 

tankering port of calls increased. Due to the double-hulled ships’ ability to reduce or prevent oil spills and as part of the 

OPA requirements, double-hulled ships have replaced almost all single-hulled ships. In 2003, 60-70% of all tankers 

were double hulled, but by 2011, 97-100% of all tankers were double hulled.

Non-OCS Oil- and Gas-Related Wastes

Shipwrecks 3.3.2.3.1

There are thousands of shipwrecks in U.S. waters. Some of the vessels involved in those wrecks are likely to contain 

oil, as fuel and possibly cargo, and may eventually result in pollution to the marine environment. Warships and cargo 

vessels sunk in wartime may also contain munitions, including explosives and chemical warfare agents, which may pose 

a continued threat because of their chemical composition.

Discharges 

Associated with 

Military Activities

3.3.2.3.2

Between the years of 1995 through 1999, Eglin Air Force Base in Florida conducted nearly 39,000 training sorties per 

year in the eastern Gulf. Potential impacts from these activities are discussed in the Eglin Gulf Test and Training 

Range: Final Programmatic Environmental Assessment (Air Force Air Armament Center, 2002). These military 

activities may result in marine impacts from chaff, fuel releases, flares, chemical materials, and debris.

Chemical 

Weapon Disposal 3.3.2.3.3

After World War I, chemical weapons were routinely disposed of in the world’s oceans, including the GOM. In some 

instances, conventional explosives and radiological wastes were dumped along with chemical weapons. Army records 

document several instances of mustard and phosgene bombs being disposed of in the Gulf of Mexico, originating from 

New Orleans, Louisiana, and Mobile, Alabama. Chemical weapons disposed of in other locations, and potentially in the 

Gulf of Mexico, contained hydrogen cyanide, arsenic trichloride, cyanogen chloride, lewisite, tabun, sarin, and VX 

(Bearden, 2007).

Industrial Waste 

Dumping 3.3.2.3.4

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 being large, unrecorded, and unregulated (USDOC, NOAA, 

2004).

Dredged Material 

Disposal 3.3.2.3.5

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 (ODMDSs). 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. The ODMDSs are regulated by the 

USEPA under the Clean Water Act and the Marine Protection, Research, and Sanctuaries Act. BOEM anticipates that, 

over the next 70 years, the amount of dredged material disposed of at ODMDSs would fluctuate, generally within the 

trends established by COE’s district offices.

Land-Based 

Discharges 3.3.2.3.6

As authorized by the Clean Water Act, the NPDES permit program controls water pollution by regulating point sources 

on land that discharge pollutants into waters of the United States. Point sources are discrete conveyances (outfalls) 

such as pipes or manmade ditches that may contain process water flows and/or precipitation from impervious surfaces. 

Industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface waters. In most 

cases, the NPDES permit program is administered by authorized states (USEPA, 2015a).

Trash and Debris 3.3.2.3.7

Marine debris originates from both land-based and ocean-based sources. Forty-nine percent of marine debris originates 

from land-based sources, 18% originates from ocean-based sources, and 33% originates from general sources (sources 

that are a combination of land-based and sea-based activities) (USEPA, 2009a).
Table 3-18. General Description of Cumulative Non-OCS Oil- and Gas-Related Impact-Producing Factors. (continued).

Impact-Producing Factors and Scenario

3-49

Impact-Producing 

Factor and 

Specific Sources

Multisale EIS 

Chapter 

Reference

General Description

Other Non-OCS Oil- and Gas-Related Activities

Non-OCS Oiland Gas-Related 

Spills

3.3.2.4

The National Research Council (2003) computed petroleum hydrocarbon inputs into North American marine waters for 

several major categories. The results show that three activities – extraction, transportation, and consumption – are the 

main sources of anthropogenic petroleum hydrocarbon pollution in the sea.

Air Emissions 3.3.2.5

Air emissions are caused by non-OCS onshore oil and gas activities and offshore State oil and gas activities, including 

combustion sources from power and heat generation, and the use of compressors, pumps, and reciprocating engines 

(i.e., boilers, turbines, and other engines); emissions resulting from flaring and venting of gas; and fugitive emissions.

Non-OCS oil- and gas-related activities can also include emissions from commercial and home heating, naturally 

occurring forest fires, motor vehicles, industrial activities in territorial seas and coastal waters, and industrial and 

transportation activities onshore.

Noise 3.3.2.7

Other noise sources in the GOM are from non-OCS oil- and gas-related activities: vessel propeller cavitation from 

commercial shipping vessels, research vessels, tourism vessels, and commercial and recreational fishing vessels; 

sources from other equipment used on vessels (e.g., pingers used in fisheries to prevent animals getting caught in nets); 

State drilling operations; aircraft; military operations; coastal infrastructure construction (e.g., pile driving); underwater 

explosions; and natural phenomena such as wind, large storms, or lightning strikes. It is not under BOEM’s authority to 

regulate any of these non-OCS oil- and gas-related noise sources, although some do occur on the OCS.

Military Warning 

and Water Test 

Areas 

3.3.2.6.1

The Gulf of Mexico (GOMEX) Range Complex contains four separate operating areas: Panama City and Pensacola, 

Florida; New Orleans, Louisiana, and Corpus Christi, Texas. The operating areas within the GOMEX Range Complex 

are not contiguous but are scattered throughout the GOM. The GOMEX Range Complex includes special-use airspace 

with associated warning areas and restricted airspace, and surface and subsurface sea space of the four operating 

areas. The air space over the GOM is used by the Department of Defense for conducting various military operations. 

Twelve military warning areas and six Eglin Water Test Areas are located within the GOM (Figure 2-7). These military 

warning areas and Eglin Water Test Areas 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.

Offshore 

Deepwater Ports 

and LNG 

Terminals

3.3.2.6.2

Deepwater ports are designed to provide access for tankers and LNG carriers to offshore offloading facilities for 

hydrocarbon products, i.e., crude oil and natural gas. Crude oil passing through an offshore port may be temporarily 

stored and then transported to shore via pipeline. The term “deepwater port” includes all associated components and 

equipment, including pipelines, pumping stations, service platforms, mooring buoys, and similar features or equipment 

to the extent that they are located seaward of the high water mark (USDOT, MARAD, 2015).

The LNG terminal means all natural gas facilities located onshore or nearshore (in State waters) that are used to 

receive, unload, load, store, transport, gasify, liquefy, or process natural gas that is imported to the U.S. from a foreign 

country, exported to a foreign country from the U.S., or transported in interstate commerce by a waterborne vessel.

Gas Hydrates 3.3.2.6.3

Methane hydrates (or gas hydrates) are cage-like lattices of water molecules containing methane, the chief constituent 

of natural gas found under arctic permafrost, as well as beneath the ocean floor. These may represent one of the 

world's largest reservoirs of carbon-based fuel. BOEM anticipates that, over the next 40 years, the Joint Industry 

Project would complete the third leg of its characterization project for GOM gas hydrates in the cumulative impacts area. 

Within 40 years, it is likely that the first U.S. domestic production from hydrates may occur in Alaska, where gas 

obtained from onshore hydrates would 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, it is not possible to discount the 
Table 3-18. General Description of Cumulative Non-OCS Oil- and Gas-Related Impact-Producing Factors. (continued). 3-50 2018 Gulf of Mexico Supplemental EIS

Impact-Producing 

Factor and 

Specific Sources

Multisale EIS 

Chapter 

Reference

General Description

possibility that first U.S. domestic production of gas hydrates could occur in the GOM.

Renewable 

Energy 3.3.2.6.4

The two primary categories of renewable energy that have the potential for development in the coastal and OCS waters 

of the U.S. are wind turbines and marine hydrokinetic systems. The first and most technologically mature renewable 

energy is wind energy, a popular source of clean and renewable energy that has been in use for centuries.

Aquaculture 3.3.2.6.5

Offshore aquaculture is the rearing of aquatic animals in controlled environments (e.g., cages or net pens) in Federal 

waters. The NOAA has published the rule to implement a Fishery Management Plan for regulating offshore aquaculture 

in the Gulf of Mexico (Federal Register, 2016a). The rule establishes a comprehensive regulatory program for 

managing the development of an aquaculture industry in Federal waters of the Gulf of Mexico.

OCS Sand 

Barrowing 3.3.2.6.6

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 51 noncompetitive negotiated agreements but has 

never had 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.

Coastal Environments

Sea-Level Rise 3.3.2.8.1

As part of the Mississippi River’s delta system, both the Delta Plain and the Chenier Plain of the Louisiana Coastal Area 

(LCA) are experiencing relatively high rates of subsidence. An absolute sea-level rise would be caused by the following 

two main contributors to the volume of ocean water on the Earth’s surface: (1) change in the volume of ocean water 

based on temperature; and (2) change in the amount of ice locked in glaciers, mountain ice caps, and the polar ice 

sheets. For the period 1961-2003, thermal expansion of the oceans accounts for only 23 ± 9% of the observed rate of 

sea-level rise (Bindoff et al., 2007); the remainder is water added to the oceans by melting glaciers, ice caps, and the 

polar ice sheets. The lowest rate of rise is found in Panama City, Florida, with a rate of 1.6 mm/yr or 0.53 ft/century. 

Given this range, BOEM anticipates that, over the next 50 years, the northern GOM would likely experience a minimum 

relative sea-level rise of 80.7 mm (3.18 in) and a maximum relative sea-level rise of 482.6 mm (19.0 in). Sea-level rise 

and subsidence together have the potential to affect many important areas, including the OCS oil and gas industry, 

waterborne commerce, commercial fishery landings, and important habitat for biological resources (State of Louisiana, 

Coastal Protection and Restoration Authority, 2012a).

Erosion 3.3.2.8.2

BOEM conservatively estimates that there are approximately 4,850 km (3,013 mi) of Federal navigation channels, 

bayous, and rivers potentially exposed to OCS traffic regionwide (Table 3-7 of the 2017-2022 GOM Multisale EIS) and 

that the average canal is widening at a rate of 0.99 m/year (3.25 ft/year) (Thatcher et al., 2011). Regionwide, this results 

in a total annual land loss of approximately 480 ac/yr (1,186 ha/yr).

Coastal 

Restoration 

Programs 

3.3.2.8.3

Coastal Louisiana wetlands make up the seventh largest delta on Earth and undergo about 90% of the total coastal 

wetland loss in the continental United States. In fact, from 1932 to 2010, coastal Louisiana has undergone a net change 

in land area of about 1.2 million ac (0.48 million ha). The first systematic program authorized for coastal restoration in 

the LCA was the 1990 Coastal Wetlands Planning, Protection and Restoration Act, otherwise known as the “Breaux 

Act.” The projects included in the Louisiana Coastal Master Plan have the potential to build between 580 and 800 mi2

(1,502 and 2,072 km2

) of land over the next 50 years, depending on future coastal conditions. The Coastal Impact 

Assistance Program provides Federal grant funds derived from Federal offshore lease revenues to oil-producing states 

for conservation, protection, or restoration of coastal areas. The Natural Resource Damage Assessment Trustee 

Council has a statutory responsibility to assess natural resource damages from the Deepwater Horizon oil spill, restore 
Table 3-18. General Description of Cumulative Non-OCS Oil- and Gas-Related Impact-Producing Factors. (continued).

Impact-Producing Factors and Scenario

3-51

Impact-Producing 

Factor and 

Specific Sources

Multisale EIS 

Chapter 

Reference

General Description

trust resources, and seek compensation for lost use of those trust resources.

Saltwater 

Intrusion 3.3.2.8.4

Saltwater intrusion is one of many factors that impact coastal environments, contributing to coastal land loss. Such 

impacts can be natural, as when storm surge brings GOM water inland, or anthropogenic, as when navigation or 

pipeline canals allow tides to introduce high salinity water to interior marshes.

Maintenance 

Dredging 3.3.2.8.5

Along the Texas Coast there are eight federally maintained navigation channels in addition to the Gulf Intracoastal 

Waterway. Most of the dredged materials from the Texas channels have high concentrations of silt and clay. Beneficial 

uses of dredged material include beach nourishment for the more sandy materials and storm reduction projects or 

ocean disposal for much of the finer-gained material. Current figures estimate that approximately 38% of that average is 

available for the beneficial use of the dredge materials program (U.S. Dept. of the Army, COE, 2013). The COE 

reported that, over the last 20 years, approximately 12,545 ha (31,000 ac) of wetlands have been created with dredged 

materials, most of which are located on the LCA delta plain (U.S. Dept. of the Army, COE, 2013). The remaining 

material is disposed of in areas described in the dredged material disposal chapter of the 2017-2022 GOM Multisale EIS

(i.e., Chapter 3.3.2.3.5).

Natural Events and Processes

Physical 

Oceanography 3.3.2.9.1

Physical oceanographic processes in the GOM include the Loop Current, Loop Current eddies, and whirlpool-like 

features that appear underneath the Loop Current and Loop Current eddies that interact with the bottom. Infrequently 

observed processes include a limited number of high-speed current events, at times approaching 100 cm/s (39 in/s). 

These events were observed at depths exceeding 1,500 m (4,921 ft) in the northern GOM (Hamilton and LugoFernandez, 2001; Hamilton et al., 2003) and as very high-speed currents in the upper portions of the water column 

observed in deep water by several oil and gas operators.

Natural Seeps 3.3.2.9.2

“Natural seeps” is used here to mean the naturally occurring seepage of crude oil and tar into the GOM. These seeps 

are geographically common and have likely been active throughout history. Natural seeps account for approximately 

47% of the crude oil entering the marine environment (Kvenvolden and Cooper, 2003).

Hurricanes 3.3.2.9.3

Twenty-one hurricanes made landfall in the WPA, CPA and EPA during the 1995-2016 hurricane seasons, disrupting 

OCS oil- and gas-related activity in the GOM (Table 3-31 of the 2017-2022 GOM Multisale EIS). Half of these 

hurricanes reached a maximum strength of Category 1 or 2 while in the CPA or WPA, while the other half were powerful 

hurricanes reaching maximum strengths of Category 4 or 5. The current era of heightened Atlantic hurricane activity 

began in 1995; therefore, the Gulf of Mexico could expect below average hurricanes in the GOM in the near term due to 

a strong El Nino. Increased hurricanes may occur if El Nino wanes during the first half of the 50-year analysis period 

and levels return to below-normal activity during the remaining half to three-quarters of the 50-year analysis period.

Climate Change 3.3.2.9.4 Issues related to climate change, including global warming, sea-level rise, and programmatic aspects of climate change 

relative to the environmental baseline for the GOM are discussed in Chapter 4.2.1 of the Five-Year Program EIS.

Mississippi River-Related Issues

Mississippi River 

Hydromodification 3.3.2.10

The Mississippi River has been anchored in place by engineered structures built in the 20th century and has been 

hydrologically isolated from the delta it built. The natural processes that allowed the river to flood and distribute alluvial 

sediments across the delta platform and channels to meander have been shut down. 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 river flow rate, and (3) channelized channels 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.
Table 3-18. General Description of Cumulative Non-OCS Oil- and Gas-Related Impact-Producing Factors. (continued). 3-52 2018 Gulf of Mexico Supplemental EIS

Impact-Producing 

Factor and 

Specific Sources

Multisale EIS 

Chapter 

Reference

General Description

Mississippi River 

Eutrophication 3.3.2.11

The Mississippi River Basin drains 41 percent of the contiguous United States. The basin covers more than 

1,245,000 mi2 (3,224,535 km2) and includes all or parts of 31 states and 2 Canadian provinces (U.S. Dept. of the Army, 

COE, 2015). Dissolved pollutants, including nutrients, enter surface water within the Mississippi River Basin via 

uncontained runoff and groundwater discharge (nonpoint sources).

Hypoxia 3.3.2.12

The Gulf of Mexico hypoxic zone is a band of oxygen-stratified water that stretches along the Texas-Louisiana shelf 

each summer where the dissolved oxygen concentrations are less than 2 milligrams/liter (USEPA, 2015b). Other small 

hypoxic areas infrequently form at the discharge of smaller rivers along the Gulf Coast; however, in the Gulf of Mexico, 

the hypoxic zone resulting from the Mississippi and Atchafalaya Rivers is by far the predominant feature. The hypoxic 

zone is the result of excess nutrients, primarily nitrogen, carried downstream by rivers to discharge to coastal waters.

Sedimentation 3.3.2.13

The lower Mississippi River, from Cairo, Illinois, to the Gulf of Mexico, transported an average of 150 million tons (with a 

range of 70-230 million tons) of sediment annually between 1963 and 2005. Historically, the quantity of sediment 

derived from catchment erosion has been affected by changes in land use and river management, increasing in the 19th 

and early 20th centuries before decreasing due to soil conservation and improved land management. Seasonal 

analysis shows that, in the spring, the median load is approximately four times the median total load in the fall. The 

median sediment size is mostly silt, but it coarsens during the winter and spring when 10% of the sediment load is 

coarser than fine sand (U.S. Dept. of the Army, European Research Office, 2008).
CHAPTER 4 

 

DESCRIPTION OF THE ENVIRONMENT AND IMPACT ANALYSIS

Description of the Affected Environment and Impact Analysis 4-3 

What’s in This Chapter?

• Chapter 4 describes the affected environment and potential environmental consequences 

of a proposed regionwide lease sale.

• Resources analyzed are as follows:

– Air Quality

– Water Quality

– Coastal Habitats (Estuarine Systems, 

and Coastal Barrier Beaches and 

Associated Dunes)

– Deepwater Benthic Communities

– Sargassum and Associated 

Communities

– Live Bottom Habitats (Topographic 

Features, and Pinnacles and 

Low-Relief Features)

– Fishes and Invertebrate Resources

– Birds

– Protected Species (Marine Mammals, 

Sea Turtles, Beach Mice, Protected 

Birds, and Protected Corals)

– Commercial Fisheries

– Recreational Fishing

– Recreational Resources

– Archaeological Resources

– Socioeconomic Issues (Land Use and 

Coastal Infrastructure, Economic 

Factors, and Social Factors, Including 

Environmental Justice)

• Impact-producing factors and impact-level definitions are identified for each resource.

• The analyses of environmental consequences consider the potential impacts from routine 

activities, accidental events, and cumulative impacts; and incomplete or unavailable 

information.

• Other analyses in this chapter include the following:

– Unavoidable Adverse Impacts of a Proposed Action

– Irreversible and Irretrievable Commitment of Resources

– Relationship Between the Short-Term Use of Man’s Environment and the Maintenance 

and Enhancement of Long-Term Productivity

4 DESCRIPTION OF THE AFFECTED ENVIRONMENT AND IMPACT 

ANALYSIS

4.0 OVERVIEW

The impacts of the 10 regionwide lease sales proposed in the Five-Year Program were 

analyzed in the 2017-2022 GOM Multisale EIS. This Supplemental EIS has been prepared to inform 

decisions for the proposed 2018 GOM lease sales and analyzes a single proposed action (i.e., a 

proposed regionwide lease sale in the Gulf of Mexico) as scheduled in the Five-Year Program. This 

Supplemental EIS contains analyses of the potential environmental impacts that could result from a 

proposed regionwide lease sale in the Gulf of Mexico as scheduled in the Five-Year Program, but 

the analyses may be applied and supplemented as necessary to inform decisions for each of the 

remaining proposed lease sales scheduled in the Five-Year Program. This Supplemental EIS 

supplements, tiers from, updates, summarizes, and incorporates by reference all of the relevant 

analyses from the Five-Year Program EIS and 2017-2022 GOM Multisale EIS, which are referenced 

below:

• November 2016 – Outer Continental Shelf Oil and Gas Leasing Program: 

2017-2022—Final Programmatic Environmental Impact Statement (Five-Year 

Program EIS; USDOI, BOEM, 2016b); and
4-4 2018 Gulf of Mexico Supplemental EIS

Chapter 4 describes the 

affected environment and 

potential environmental 

consequences of a single 

proposed lease sale.

• March 2017 – Gulf of Mexico OCS Oil and Gas Lease Sales: 2017-2022; Gulf of 

Mexico Lease Sales 249, 250, 251, 252, 253, 254, 256, 257, 259, and 261—

Final Multisale Environmental Impact Statement (2017-2022 GOM Multisale EIS; 

(USDOI, BOEM, 2017a).

An analysis of the routine activities, accidental events, and cumulative impacts of a proposed 

action on the environmental, socioeconomic, and cultural resources of the Gulf of Mexico can be 

found in Chapter 4 of the 2017-2022 GOM Multisale EIS, which is hereby incorporated by reference.

The purpose of this Supplemental EIS is to determine if there are significant new 

circumstances or information bearing on a proposed action or its impacts, as previously discussed in 

the 2017-2022 GOM Multisale EIS, and if so, to disclose those changes and conclusions. This 

includes all relevant new information available since publication of the 2017-2022 GOM Multisale 

EIS. As will be demonstrated within each environmental, socioeconomic, and cultural resources 

chapter in this Supplemental EIS, no new circumstances or new information was identified since the 

publication of the 2017-2022 GOM Multisale EIS and the conclusions reached in the 2017-2022 

GOM Multisale EIS remain the same for this Supplemental EIS. 

As discussed in Chapter 1.2, BOEM makes individual 

decisions on whether and how to proceed with each proposed lease 

sale pursuant to the OCSLA’s staged leasing process. The decision 

on whether and how to proceed with proposed Lease Sale 250, 

which is the first lease sale proposed for 2018, will be made 

following the completion of this NEPA analysis. A separate decision 

will be made on whether and how to proceed with the second lease 

sale proposed for 2018, which is Lease Sale 251. Decisions on the remaining proposed GOM lease 

sales in the Five-Year Program will be made based on additional NEPA review that may update this 

Supplemental EIS as necessary. This chapter describes the affected environment and the potential 

impacts of routine activities, reasonably foreseeable accidental events, and cumulative impacts 

caused by a proposed lease sale and the alternatives on these resources.

This chapter is organized by groups of resources. The chapter is divided into the physical 

factors (i.e., air and water quality), biological factors (i.e., habitat resources followed by the fauna 

that are found in or utilize these habitats), and finally the social environment, including commercial 

fisheries, recreational resources, land use, and environmental justice.

• Air Quality (Chapter 4.1) 

• Water Quality (Chapter 4.2) 

• Habitat Resources

− Coastal Habitats (Chapter 4.3) 

− Deepwater Benthic Communities (Chapter 4.4) 
Description of the Affected Environment and Impact Analysis 4-5 

− Sargassum and Associated Communities (Chapter 4.5) 

− Live Bottom Habitats (Chapter 4.6) 

• Faunal Resources

− Fish and Invertebrate Resources (Chapter 4.7) 

− Birds (Chapter 4.8) 

− Protected Species (Chapter 4.9) 

• Social Environment

− Commercial Fisheries (Chapter 4.10) 

− Recreational Fishing (Chapter 4.11) 

− Recreational Resources (Chapter 4.12) 

− Archaeological Resources (Chapter 4.13) 

− Human Resources and Land Use (Chapter 4.14) 

The habitat resource chapters focus on the impact-producing factors that would affect their 

environment while the other chapters concentrate on the biological effects of impact-producing 

factors on fauna and human resources. To decrease repetition, the habitat information is generally 

not restated in the fauna chapters and vice versa.

As discussed above, this Supplemental EIS tiers from and uses information contained in 

both the Five-Year Program EIS (USDOI, BOEM, 2016b) and 2017-2022 GOM Multisale EIS 

(USDOI, BOEM, 2017a). BOEM concentrated on providing a focused analysis by incorporating 

information by reference from these documents. Programmatic aspects of the potential impacts of 

climate change relative to the environmental baseline for the Gulf of Mexico OCS Program are 

discussed within each resource and in Chapter 1 of the Five-Year Program EIS. In addition, the 

potential for alternative energy on the Federal OCS is addressed in the Five-Year Program EIS 

(Chapters 1.4.6.1 and 2.7.4), from which this Supplemental EIS tiers. Furthermore, supporting 

technical information in previous NEPA reviews have been developed as white papers and are 

summarized and incorporated by reference as appropriate. These white papers include the OCS 

Regulatory Framework (Cameron and Matthews, 2016), Catastrophic Spill Event Analysis (USDOI, 

BOEM, 2017b) and Essential Fish Habitat Assessment (USDOI, BOEM, 2016d). BOEM has also 

prepared a technical report on climate change as part of the Five-Year Program EIS, which is 

incorporated by reference into this Supplemental EIS (Wolvovsky and Anderson, 2016).

This Supplemental EIS was prepared with consideration of potential changes to or new 

information about the baseline conditions of the physical, biological, and socioeconomic resources. 

Current baselines (including past and present events) are described for all resources in full detail 

under their respective “Affected Environment” sections in the 2017-2022 GOM Multisale EIS, which 
4-6 2018 Gulf of Mexico Supplemental EIS

is hereby incorporated reference, and are summarized in this Supplemental EIS. Past events such 

as Hurricanes Katrina and Rita and the Deepwater Horizon explosion, oil spill, and response have 

potentially affected multiple resources over a large area. Specific to the Deepwater Horizon, the 

Deepwater Horizon Oil Spill: Final Programmatic Damage Assessment and Restoration Plan and 

Final Programmatic Environmental Impact Statement (PDARP/PEIS; Deepwater Horizon Natural 

Resource Damage Assessment Trustees, 2016), which has the purpose and need of assessing and 

creating restoration plans to relieve injuries from the Deepwater Horizon explosion, oil spill, and 

response to natural resources and services, has been completed. The injuries assessed within the 

PDARP/PEIS do not necessarily equate the baseline as defined in NEPA.

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 

currently be known and some could take years to fully develop (refer to the “Incomplete or 

Unavailable Information” for each resource). The analyses of impacts from the Deepwater Horizon

explosion, oil spill, and response on the physical, biological, and socioeconomic resources in this 

Supplemental EIS, are based on 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, 

BOEM and the Deepwater Horizon Natural Resource Damage Assessment Trustee Council

continue to study, measure, and interpret impacts arising out of that spill. BOEM continues to 

analyze the Deepwater Horizon explosion, oil spill, and response as information becomes available, 

and it was evaluated as part of the baseline for resources in this Supplemental EIS. Thus, there are 

instances in which BOEM is faced with incomplete or unavailable information (refer to Chapter 

4.0.2.4) that may be relevant to evaluating reasonably foreseeable significant adverse impacts on 

the human environment. Further, a low-probability catastrophic event and the resulting analysis of 

potential effects are presented in Catastrophic Spill Event Analysis white paper (USDOI, BOEM, 

2017b).

4.0.1 What Encompasses the Affected Environment for a Gulf of Mexico Lease 

Sale? 

Each resource chapter includes a unique description of the affected environment and an 

analysis of the potential environmental consequences of the alternatives for that particular resource. 

The Federal and State waters of the Gulf of Mexico and the adjacent coastal states are generally the 

affected environment described in each resource chapter. Current baselines are described for all 

resources under their respective “Affected Environment” sections. Specific to the PDARP/PEIS 

(Deepwater Horizon Natural Resource Damage Assessment Trustees, 2016), the altered baseline 

includes individual protected species directly affected by the Deepwater Horizon explosion, oil spill, 

and response, an unexpected unique catastrophic event. BOEM understands that each oil-spill 

event is unique and that its outcome depends on several factors, including time of year and location 

of the release relative to winds, currents, land, and sensitive resources, as well as specifics of the 

well and response effort. BOEM also understands that the severity of impacts from an oil spill 
Description of the Affected Environment and Impact Analysis 4-7 

An impact-producing factor is an 

activity or process, as a result of a 

proposed lease sale, that could 

cause impacts on the 

environmental or socioeconomic 

setting. Chapter 3 provides a 

description of all possible impactproducing factors considered in 

this analysis.

cannot be predicated on volume alone. BOEM has analyzed a low-probability catastrophic event 

(USDOI, BOEM, 2017b) in conjunction with its analysis of potential effects, as requested by CEQ 

pursuant to its regulation at 40 CFR § 1502.22. A low-probability catastrophic spill is, by definition, 

not reasonably certain to occur. Other methods of analysis are neither significantly limited in their 

applicability and availability nor would they provide any meaningful or useful information to be used 

to assess the risk of catastrophic spill occurrence at this programmatic level of oil and gas activities 

in the GOM. The return period of a catastrophic oil spill in OCS areas is estimated to be 165 years, 

with a 95 percent confidence interval between 41 years and more than 500 years (Ji et al., 2014).

4.0.2 How are the Potential Environmental Consequences Determined? 

The analyses of potential impacts to the wide variety of physical, environmental, and 

socioeconomic resources in the vast area of the GOM and adjacent coastal areas is very complex. 

For this Supplemental EIS, a set of assumptions and a scenario were developed, along with 

descriptions of impact-producing factors that could occur from routine OCS oil- and gas-related 

activities, including accidental events. Analysis of the 

various alternatives considers these impact-producing 

factors (described in detail in Chapter 3) within a distinct 

framework that includes frequency, duration, and geographic 

extent. Frequency (whether rare, intermittent, or continuous) 

refers to how often the factor occurs over the entire analysis 

period of 50 years for routine activities and accidental 

events. Duration refers to how long the factor lasts from less 

than a year to many years. Geographic extent covers what 

areas are affected, and depending on the factor, how large of 

an area is affected.

Using this information, the interdisciplinary team of subject-matter experts applied knowledge 

and experience to conduct analyses of the potential effects of a proposed lease sale on resources. 

Specialized education, experience, and technical knowledge are required of these subject-matter

experts, as well as familiarity with the numerous impact-producing factors associated with OCS 

oil- and gas-related activities and other activities that can cause cumulative impacts in the area to 

conduct this analysis. 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), ESA, Marine Mammal Protection Act, Magnuson-Stevens Fishery Conservation and 

Management Act, and others are also required to conduct this analysis. In order to accomplish this 

task, BOEM has assembled an interdisciplinary team with many years of collective experience. The 

vast majority of this team has advanced degrees with a high level of knowledge related to the 

particular resources discussed in this chapter. This team prepares the input to BOEM’s lease sale 

EISs and a variety of subsequent postlease NEPA reviews, and is also involved with ESA, EFH 

Assessment, 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 the Bureau of Ocean Energy Management’s NEPA analyses.
4-8 2018 Gulf of Mexico Supplemental EIS

The potential magnitude of impact 

using these resource-specific 

definitions are provided in most 

resource chapters as a summary 

table to help the reader quickly 

identify the level of potential 

impacts for each impact-producing 

factor.

How Were Impact Levels Defined?

The environmental consequences in each resource chapter include an analysis of applicable 

impact-producing factors from the categories of routine activities, accidental events, and cumulative 

impacts that would occur under any of the action alternatives (i.e., Alternatives A, B, C, and D).

It must be emphasized that, in arriving at the overall conclusions for certain environmental 

resources (e.g., birds, fisheries, and wetlands) for each alternative, the conclusions are based on 

potential impacts to the resources or species population as a whole, not to individuals, small groups 

of animals, or small areas of habitat. BOEM analyzes impacts on a finer geographic scale and 

mitigations that are appropriate for consideration through site-specific environmental reviews (refer 

to Appendix A of the 2017-2022 GOM Multisale EIS). Each resource topic discussion includes a 

threshold effects determination and includes a resource-specific definition of impact level. 

Additionally, potential beneficial effects of a proposed action have also been considered and 

identified in individual resource chapters. For example, implementation of a proposed lease sale is 

anticipated to have beneficial impacts in the Area of Interest for economics due to the direct and 

indirect spending associated with the oil and gas industry. For this Supplemental EIS, effects 

thresholds are defined using four categories of significance.

• Negligible – Impacts may or may not cause observable changes to natural 

conditions; regardless, they do not reduce the integrity of a resource.

• Minor – Impacts cause observable and short-term changes to natural conditions 

but they do not reduce the integrity of a resource.

• Moderate – Impacts cause observable and short-term changes to natural 

conditions and/or they reduce the integrity of a resource.

• Major – Impacts cause observable and long-term changes to natural conditions 

and they reduce the integrity of a resource.

The conclusions developed by BOEM’s subjectmatter experts regarding the potential effects of a proposed 

lease sale for most resources are necessarily qualitative in 

nature; however, they are based on the science-based

judgment of the highly trained subject-matter experts. Staff 

approach this effort utilizing credible scientific information 

and apply it to the subject resources using accepted 

methodologies. It is important to note that, barring another 

catastrophic oil spill, which is a low-probability accidental 

event not expected to occur and therefore not part of a 

proposed action, the adverse impacts associated with a proposed lease sale are expected to be 

small, and beneficial impacts are projected as well for certain activities and species. This is because 

of BOEM’s potential use of lease sale stipulations and mitigations, site-specific mitigations that may 

become conditions of plan or permit approval at the postlease stage, and mitigations required by 
Description of the Affected Environment and Impact Analysis 4-9 

other State and Federal agencies that help to avoid or minimize many of the impacts. Over the 

years, a suite of lease stipulations and mitigating measures has been developed to eliminate or 

ameliorate potential environmental effects, where implemented (refer to Appendix B of the 

2017-2022 GOM Multisale EIS, “Commonly Applied Mitigation Measures”). BOEM’s primary 

mitigative method is the avoidance of impacts, which is primarily implemented during approval of 

postlease activities. In many instances, these were developed in coordination with other natural 

resource agencies such as NMFS and FWS. Informal and formal consultation with other Federal 

agencies and affected States, and commenting opportunities for the public are implemented to assist 

in the development of the information and analyses in this Supplemental EIS. Specifically, 

information requests soliciting input on the proposed lease sales were issued during scoping for this 

Supplemental EIS (refer to Chapter 5). The impact-level conclusions reached in each resource area 

consider the applicable impact-producing factors, the level of activity, and the geographic area of 

each alternative.

Lease sale stipulations considered for a proposed lease sale may include 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 (Transboundary Stipulation). The Topographic 

Features and Live Bottom (Pinnacle Trend) Stipulations have been applied as programmatic 

mitigation in the Five-Year Program EIS (USDOI, BOEM, 2016b) and, therefore, would apply to all 

leases issued under the Five-Year Program in the designated lease blocks. Site-specific postlease 

mitigations may include buffer zones and avoidance criteria to protect sensitive resources such as 

areas of deepwater benthic communities, topographic features, and historic shipwrecks. Mitigations 

may also be required by other agencies (i.e., the U.S. Army Corps of Engineers and State Coastal 

Zone Management agencies) to avoid or reduce impacts from OCS oil- and gas-related activities, 

e.g., boring under beach shorelines and the rerouting of pipelines to reduce or eliminate impacts 

from OCS pipelines that make landfall. These mitigations and their potential effect on reducing or 

eliminating impacts from a proposed lease sale are analyzed in this chapter.

Under all four action alternatives, postlease activities would be reviewed on a case-by-case 

basis and the applicable commonly applied mitigating measures (refer to Appendix B of the 

2017-2022 GOM Multisale EIS) would be identified during site-specific reviews of plans and permits. 

This avoids excessive replication of discussion of similar if not identical impacts throughout the entire 

document, allowing the reader to focus on the differences between the alternatives.

4.0.2.1 Routine Activities

The types of routine activities that could occur from all operations as a result of a single 

proposed lease sale are described in Chapter 3.1. The major types of routine activities include 

geological and geophysical surveys; exploration, development, and production drilling; infrastructure 
4-10 2018 Gulf of Mexico Supplemental EIS

emplacement and presence, including pipelines; transportation, including barges, vessels, and 

helicopters; discharges and wastes; decommissioning and removal; coastal infrastructure; air 

emissions; noise; and safety issues. The time period for postlease activities related to a single 

proposed lease sale is 50 years.

4.0.2.2 Accidental Events

A summary of the information on accidental events that are reasonably foreseeable from all 

operations conducted under the OCS Program, as well as information on the number and sizes of 

spills from non-OCS oil- and gas-related sources is provided in Chapter 3.2. The types of 

accidental events that could reasonably be expected as a result of postlease activities include oil 

spills, losses of well control, accidental air emissions, pipeline failures, vessel and helicopter 

collisions, chemical and drilling-fluid spills, and spill response as a result of a proposed lease sale.

4.0.2.3 Cumulative Impacts

The cumulative analysis considers impacts to physical, biological, and socioeconomic 

resources that may result from the incremental impact of a proposed lease sale when added to all 

past, present, and reasonably foreseeable future human activities and natural processes. However, 

most resources consider the past and present cumulative impacts as part of the baseline 

environmental conditions, and they are covered where relevant in the affected resource description. 

It is reasonably foreseeable to assume that lease sales would continue to occur, as they have 

historically, for many years to come in the Gulf of Mexico region, based on resource availability, 

existing infrastructure, and projected time lapses required for any other major energy sources to 

come online. However, the level of activities (exploration wells, production wells, and pipelines) 

becomes more speculative as time is projected further into the future. The causes for this are 

uncertainty in long-term oil price forecasts, hydrocarbon resource potential, cost of exploration, 

development and production, and various resource constraints (e.g., drilling rig availability versus the 

amount of acreage leased from a lease sale). Furthermore, OCSLA provides for phased 

decisionmaking, each of which is a decision subject to NEPA. The OCSLA stages include the 

Five-Year Program stage to identify a schedule of leases over the period; the lease sale stage; the 

exploration stage; the development and production stage; and ultimately decisions on how a lessee 

may proceed with decommissioning. These reviews require consideration of cumulative impacts 

that would factor in changing environmental baselines, oil and gas price forecasts, and technology 

advancements, among others. Additionally, even though continued consumer demand is likely, new 

advances in technology (both on upstream development and production ends and downstream user 

ends) can potentially change the level of projected activities and how they are conducted. These 

could further minimize environmental risks. Technology advancements and organizational 

effectiveness could also further reduce projected air emissions, wastewater quantities, and other 

impact producing factors such as helicopter and vessel trips and accidental events.

Therefore, cumulative impact assessment for this Supplemental EIS considers existing 

environmental baseline conditions, past OCS oil- and gas-related and non-OCS oil- and gas-related 

activities in the GOM, projected future activities as a result of past lease sales, 50 years of 
Description of the Affected Environment and Impact Analysis 4-11

incremental projected activities as a result of the proposed lease sales during the 2017-2022 FiveYear Program, and reasonably assumes projected activities for future lease sales based on current 

trends. Non-OCS oil- and gas-related activities include, but are not limited to, import tankering; 

marine transportation; State oil and gas activity; recreational, commercial, and military vessel traffic; 

offshore liquefied natural gas activity; recreational and commercial fishing; onshore development; 

and natural processes. The time period for reasonably foreseeable future actions are dependent 

upon the nature of each resource and are therefore defined in each resource chapter. The types of 

cumulative activities that could reasonably occur are described in Chapter 3.3. 

4.0.2.4 Incomplete or Unavailable Information

Throughout this chapter, where information was incomplete or unavailable, BOEM complied 

with its obligations under NEPA to determine if the information was relevant to reasonably 

foreseeable significant adverse impacts; if so, whether it was essential to a reasoned choice among 

alternatives; and, if it was essential, whether it can be obtained and whether the cost of obtaining the 

information is exorbitant, as well as whether scientifically credible information using generally 

accepted scientific methodologies can be applied in its place (40 CFR § 1502.22).

The most notable incomplete or unavailable information relates to some aspects of the 

effects from the Deepwater Horizon explosion, oil spill, and response. Credible scientific data 

regarding the potential short-term and long-term impacts from the Deepwater Horizon explosion, oil 

spill, and response on some GOM resources have become available. However, information relating 

to long-term effects continue to be studied and remain incomplete at this time, and it could be many 

years before this information becomes available. The Trustees have released the PDARP/PEIS 

(Deepwater Horizon Natural Resource Damaage Assessment Trustees, 2016). However, the 

information collected during the Natural Resource Damage Assessment (NRDA) process that the 

assessment, plan, and EIS used as a basis for their determinations are not yet publicly available 

(e.g., NRDA technical working group reports). There remains information being developed through 

the NRDA process, but it is not yet available as a final report. Nonetheless, BOEM’s subject-matter 

experts acquired and used newly available, scientifically credible information; determined that other 

additional information was not available absent exorbitant expenditures or could not be obtained 

regardless of cost in a timely manner; and where gaps remained, exercised their best professional 

judgment to extrapolate baseline conditions and impact analyses using accepted methodologies 

based on credible information. While incomplete or unavailable information could conceivably result 

in potential future shifts in baseline conditions of habitats that could affect BOEM’s decisionmaking, 

BOEM has determined that it can make an informed decision at this time without this incomplete or 

unavailable information. BOEM’s subject-matter experts have applied other scientifically credible 

information using accepted theoretical approaches and research methods, such as information on 

related or surrogate species. Moreover, BOEM will continue to monitor these resources for effects 

caused by the Deepwater Horizon explosion, oil spill, and response, and will ensure that future 

BOEM environmental reviews take into account any new information that may emerge.
4-12 2018 Gulf of Mexico Supplemental EIS

Furthermore, BOEM has considered the reasonably foreseeable impacts of a low-probability 

catastrophic oil spill in a white paper. These types of events, such as the one that resulted from the 

Deepwater Horizon explosion, are not reasonably expected to occur and therefore are not part of a 

proposed action. BOEM has prepared the Catastrophic Spill Event Analysis white paper, which 

provides a summary of existing credible scientific evidence related to this issue and BOEM’s 

evaluation of the potential impacts to the physical, biological, and socioeconomic resources and 

conditions based upon theoretical approaches or research methods generally accepted in the 

scientific community (USDOI, BOEM, 2017b). The white paper was included in previous lease sale 

EISs as an appendix. To avoid repetition and redundancies, the white paper is incorporated by 

reference and is publicly available on BOEM’s website at http://www.boem.gov/nepaprocess/. 

BOEM updated the analysis in the white paper and will update it again should new information

become available relevant to the reasonably foreseeable impacts of a catastrophic spill event.

4.0.2.5 Alternatives

Each resource chapter includes an analysis of the relevant impact-producing factors to that 

specific resource from the routine activities, accidental events, and cumulative impacts that are 

described in Chapter 3. After this general analysis, the scale and location of these activities, events, 

and impacts are considered for each alternative.

Alternative A

In general, Alternative A could potentially result in 1.2-4.2 percent of the forecasted 

cumulative OCS oil and gas activity in the Gulf of Mexico and would occur in the WPA, CPA, and 

EPA portions of the proposed lease sale area (refer to Chapter 3.1.2). Most of the activity (up to 

83%) of a proposed lease sale under Alternative A is expected to occur in the CPA and EPA 

portions of the proposed lease sale area, while up to 19 percent of the activity could occur in the 

WPA portion of the proposed lease sale area. Approximately 75.7 million acres (82%) of the 

regionwide lease sale area would be available for lease under this alternative.

Alternative B

Alternative B could potentially result in 1.0-3.6 percent of the forecasted cumulative OCS oil 

and gas activity in the Gulf of Mexico, or a slightly smaller amount of activity than proposed for 

Alternative A, and would be located geographically in the CPA and EPA portions of the proposed 

lease sale area (refer to Chapter 3.1.2). Approximately 49.8 million acres (54%) of the regionwide 

lease sale area would be available for lease. While all of the leases issued under this alternative 

would occur in the CPA and EPA portions of the proposed lease sale area, activities such as vessel

support and pipeline or coastal infrastructure could occur in the WPA portion of the proposed lease 

sale area.

Alternative C

Alternative C could potentially result in 0.2-0.6 percent of the forecasted cumulative OCS oil 

and gas activity in the Gulf of Mexico, which is much smaller than either Alternative A or B (refer to 
Description of the Affected Environment and Impact Analysis 4-13

Chapter 3.1.2). Approximately 25.9 million acres (28%) of the regionwide lease sale area would be 

available for lease. While all of the leases issued under this alternative would occur in the WPA 

portion of the proposed lease sale area, activities such as vessel support and pipeline or coastal 

infrastructure could occur in the CPA/EPA portion of the proposed lease sale area.

Alternative D

Under Alternative D, the number of blocks that would become unavailable for lease 

represents only a small percentage of the total number of blocks to be offered under Alternative A, 

B, or C (<4%), even if blocks subject to all three stipulations were excluded. However, it is also 

possible (and BOEM believes more reasonable to expect) that Alternative D would only shift the 

location of offshore infrastructure and activities farther from these sensitive zones and not lead to a 

reduction in offshore infrastructure and activities.

Alternative E

Alternative E is the cancellation of a single proposed lease sale. Under Alternative E, there 

would be no routine activities or accidental events as a result of a proposed lease sale. Therefore, 

there would be no associated impacts resulting from a proposed lease sale. Cancellation of a 

proposed lease sale, however, would not stop all OCS oil- and gas-related activities. Activities 

related to previously issued leases and permits (as well as those that may be issued in the future 

under separate decision) related to the OCS oil and gas program would continue and could have 

impacts similar to those described in each resource chapter. However, no new activities related to a 

proposed lease sale would proceed and, therefore, those additional impacts would be avoided.

4.0.2.6 Summary

This chapter has thoroughly examined the existing credible scientific evidence that is 

relevant to evaluating the reasonably foreseeable significant impacts of a proposed lease sale and 

the alternatives on the environment. All reasonably foreseeable impacts, including beneficial ones, 

were considered. Impacts that could have catastrophic consequences, even if their probability of 

occurrence is low, not reasonably expected, and not part of a proposed action are considered in the 

Catastrophic Spill Event Analysis white paper (USDOI, BOEM, 2017b). Throughout this chapter, 

where information was incomplete or unavailable, BOEM complied with its obligations under NEPA 

to determine if the information was relevant to reasonably foreseeable significant adverse impacts; if 

so, whether it was essential to a reasoned choice among alternatives; and, if it was essential, 

whether it can be obtained and whether the cost of obtaining the information is exorbitant, as well as 

whether credible scientific information applied using generally accepted scientific methodologies can 

be used in its place (40 CFR § 1502.22). BOEM has made conscientious efforts to comply with the 

spirit and intent of NEPA and to be comprehensive in its analyses of potential environmental 

impacts. 
4-14 2018 Gulf of Mexico Supplemental EIS

4.1 AIR QUALITY

Typical Supplemental EIS analyses summarize the analyses from which they tier and 

re-analyze the conclusions based on new information. However, since this air quality analysis was 

completed for the Final 2017-2022 GOM Multisale EIS and did not have the benefit of public review, 

the complete analysis is included in this Supplemental EIS for public review and comment. BOEM 

looks forward to receiving relevant comments on the methods used in air quality modeling and the 

resulting analyses.

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

with a GOM proposed lease sale and its incremental contribution to the cumulative impacts to air 

quality are presented in this chapter. The approach of the analysis is to focus on the greatest 

reasonably foreseeable impact-producing factors from OCS oil- and gas-related routine activities 

(from exploration, development, and production), as well as accidental events and cumulative 

impacts, and to define the impact levels for each. The impact-producing factors considered and 

analyzed include (1) OCS oil- and gas-related emissions sources related to drilling and associated 

vessel support, production and the connected action of vessel support, flaring and venting, 

decommissioning, and oil spills; (2) other emissions not caused by OCS oil and gas development 

(i.e., non-OCS oil- and gas-related emissions such as State oil and gas programs, onshore industrial 

and transportation sources, and natural events); and (3) the incremental contribution of all postlease 

activities as a result of a single proposed lease sale. The impact-level definitions and the analyses 

supporting these conclusions are discussed in this chapter.

In order to assess the impacts from these oil- and gas-related activities, BOEM used an 

emissions inventory along with air dispersion and photochemical modeling. While an emissions 

inventory is an accounting of air emissions of criteria pollutants, precursors of criteria pollutants, and 

hazardous air pollutants from a variety of air emission sources, the comprehensive data from the 

inventory can be used to support air quality modeling. Typically, impacts are determined through 

modeling, and concentrations are reported. These impacts are then compared with reference 

measures, such as National Ambient Air Quality Standards (NAAQS), Significant Impact Levels 

(SILs), etc., to support impact conclusions. For the 2017-2022 GOM Multisale EIS and this 

Supplemental EIS analyses, BOEM used the following: (1) the results of the Year 2011 Gulfwide 

Emissions Inventory (GWEI) study, herein incorporated by reference (Wilson et al., 2014); (2) the 

changes in regulations as a result of the 2010 Deepwater Horizon explosion, oil spill, and response 

to determine the impact-producing factors (Table 4-1) that have the greatest impact potential in the 

GOM region; and (3) the results of the “Air Quality Modeling in the Gulf of Mexico Region” study to 

determine impacts. Pollutants included the emissions inventory support analysis of air quality 

impacts in terms of impacts on the attainment of the NAAQS and on air quality-related values 

(AQRVs), including acid deposition and visibility. The results of the emissions inventory study and 

air modeling study are discussed later in this chapter. The “Air Quality Modeling in the Gulf of 

Mexico Region” study includes technical support documents (Appendices B-D) that provide detailed 

descriptions of the emissions data, meteorological and photochemical grid, modeling parameters 

and methodology, and the results of the air quality impact analysis.
Description of the Affected Environment and Impact Analysis 4-15

Table 4-1. Air Quality Impact-Producing Factors That Are Reasonably Foreseeable.

Air Quality Magnitude of Potential Impact1

Impact-Producing Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Drilling Minor Minor Minor Minor None

Production Minor Minor Minor Minor None

Vessel Support during 

Drilling and Production Minor Minor Minor Minor None

Routine Flaring and 

Venting Minor Minor Minor Minor None

Decommissioning Minor Minor Minor Minor None

Accidental Impacts

Emergency Flaring and 

Venting Minor Minor Minor Minor None

Oil Spills Minor Minor Minor Minor None

Cumulative Impacts

Incremental Contribution2 Minor Minor Minor Minor None

OCS Oil and Gas3 Moderate

Non-OCS Oil and Gas4 Moderate

1 The analysis supporting these conclusions is discussed in detail in the environmental consequences 

“Environmental Consequences” chapter below.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

4 This includes other past, present, and reasonably foreseeable future activities occurring within the same 

geographic range and within the same timeframes as a proposed action, but they are not related to the 

OCS Oil and Gas Program.

Impact-Level Definitions

The following impact categories and definitions are used:

• Negligible – No measurable impact(s).

• Minor – Most impacts on the affected resource could be avoided with proper 

mitigation; if impacts occur, the affected resource would recover completely 

without mitigation once the impacting stressor is eliminated.

• Moderate – Impacts on the affected resource are unavoidable. The viability of 

the affected resource is not threatened although some impacts may be 

irreversible, or the affected resource would recover completely if proper 

mitigation is applied or proper remedial action is taken once the impacting 

stressor is eliminated.
4-16 2018 Gulf of Mexico Supplemental EIS

• Major – Impacts on the affected resource are unavoidable. The viability of the 

affected resource may be threatened although some impacts may be irreversible, 

and the affected resource would not fully recover even if proper mitigation is

applied or remedial action is implemented once the impacting stressor is 

eliminated.

BOEM’s Gulf of Mexico OCS Region manages the responsible development of oil, gas, and 

mineral resources for the 430 million ac in the WPA, CPA, and a small portion of the EPA on the 

OCS comprising the GOM region. The Gulf of Mexico OCS area of possible influence includes the 

States of Texas, Louisiana, Mississippi, Alabama, and Florida, and is depicted on Figure 4-1. 

However, the Clean Air Act Amendments of 1990 designated air quality authorities in the GOM, 

giving BOEM air quality jurisdiction westward of 87°30' W. longitude and USEPA air quality 

jurisdiction eastward of 87°30' W. longitude. The USEPA air quality jurisdiction includes part of the 

CPA and all of the EPA, while BOEM’s air quality jurisdiction includes most of the CPA and all of the 

WPA. In 2006, oil and gas leasing operations within 125 mi (201 km) of the Florida coastline were 

placed under moratorium until 2022 under the Gulf of Mexico Energy Security Act (GOMESA). The 

GOMESA moratoria area is depicted in Figure 4-1. 

Figure 4-1. Gulf of Mexico Region with the Planning Areas, Nonattainment Areas, and Class I (dark 

green) and Sensitive Class II (light green) Areas. (Note: The South Atlantic Planning Area 

was removed from the Five-Year Program.) 

BOEM is required under the OCSLA (43 U.S.C. § 1334(a)(8)) to develop regulations to 

ensure compliance with the NAAQS to the extent that OCS offshore oil and gas exploration, 

development, and production sources do not significantly affect the air quality of any state pursuant 

to the NAAQS. Since the primary NAAQS are designed to protect human health, BOEM focuses 
Description of the Affected Environment and Impact Analysis 4-17

this Supplemental EIS analysis on the impact of these activities on the States, where there are 

permanent human populations. However, the potential impacts for the whole Gulf of Mexico region 

were modeled, including the impacts at the State/seaward boundary of Gulf Coast States (3-9 nmi 

[3.45-10.36 mi; 5.56-16.67-km] from shore, depending on the State). Detailed potential impacts from 

the “Air Quality Modeling in the Gulf of Mexico Region” study are included in Appendix D. 

4.1.1 Description of the Affected Environment

For this Supplemental EIS analysis, the affected environment comprises the WPA, CPA, and 

EPA, including the States of Texas, Louisiana, Mississippi, Alabama, and Florida, and the respective 

State waters. This area also includes national parks and Federal wilderness areas where air quality 

and AQRVs (primarily visibility) are protected more stringently than under the NAAQS. These 

protected Class I areas in the GOM region include the following: the Breton Wilderness Area in 

Louisiana; and the Bradwell Bay Wilderness Area, Chassahowitza National Wilderness Area, 

Everglades National Park, and St. Marks Wilderness Area in Florida.

The Clean Air Act Amendments of 1977 designated 156 Class I areas, consisting of national 

parks and wilderness areas that are offered special protection for air quality and the AQRVs. The 

Class I areas, compared to the Class II areas, have lower Prevention of Significant Deterioration 

(PSD) air quality increments that new sources may not exceed and are protected against excessive 

increases in several AQRVs, including visibility impairment, acid (sulfur and nitrogen) deposition, 

and nitrogen eutrophication. The Regional Haze Rule (40 CFR § 51.308) has a goal of natural 

visibility conditions by 2064 at Class I areas, and States must submit Regional Haze Rule State 

Implementation Plans that demonstrate progress towards that goal. Figure 4-1 displays the 

locations of the mandatory Class I areas in the GOM region.

While not included in the Clean Air Act Amendments of 1977 as an area of special 

protection, Federal management agencies have designated certain other areas as sensitive Class II 

areas for tracking PSD increment consumption and AQRV impacts. The sensitive Class II areas, 

designated as such in the GOM region, include the Padre Island National Seashore and Gulf Islands 

National Seashore. Since Class I and sensitive Class II areas are of concern, the areas located in or 

nearby the GOM region are discussed in this Supplemental EIS and are shown in Figure 4-1. 

Clean Air Act and the Clean Air Act Amendments Overview

The Clean Air Act of 1970 established the NAAQS, which include the primary standards to 

protect public health and secondary standards to protect public welfare including visibility and 

vegetation. Under the Clean Air Act, the USEPA is periodically required to review and, as 

appropriate, modify the criteria based on the latest scientific knowledge. Several revisions to the 

NAAQS have occurred in the past few years as more is understood about the effects of the 

pollutants. The current NAAQS, shown in Table 4-2, address six pollutants: carbon monoxide (CO); 

nitrogen dioxide (NO2); particulate matter (PM2.5 and PM10); sulfur dioxide (SO2); lead (Pb); and

ozone (O3).
4-18 2018 Gulf of Mexico Supplemental EIS

Table 4-2. National Ambient Air Quality Standards.

Pollutant

(Final Rule Citation)

Primary/

Secondary

Averaging

Time Level Form

Carbon Monoxide (CO)

(Federal Register, 2011) Primary

8-hour 9 ppm Not to be exceeded more 

1-hour 35 ppm than once per year

Lead (Pb)

(Federal Register, 2008a) 

Primary and 

Secondary

Rolling 

3-month 

average

0.15 μg/m3(1) Not to be exceeded

Nitrogen Dioxide (NO2) 

(Federal Register, 2010a) 

(Federal Register, 1996)

Primary 1-hour 100 ppb 98th percentile, averaged 

over 3 years

Primary and 

Secondary Annual 53 ppb(2) Annual mean

Ozone (O3) 

(Federal Register, 2015b) 

Primary and 

Secondary 8-hour 0.070 ppm(3)

Annual 4th-highest daily 

maximum 8-hour 

concentration, averaged 

over 3 years

Particle Pollution

(Federal Register, 

2013)

(Federal Register, 

2006a) 

PM2.5

Primary Annual 12 μg/m3 Annual mean, averaged 

over 3 years

Secondary Annual 15 μg/m3 Annual mean, averaged 

over 3 years

Primary and 

Secondary 24-hour 35 μg/m3 98th percentile, averaged over 3 years

PM10

Primary and 

Secondary 24-hour 150 μg/m3

Not to be exceeded more 

than once per year on 

average over 3 years

Sulfur Dioxide (SO2) 

(Federal Register, 2010b)

(Federal Register, 1973)

Primary 1-hour 75 ppb(4)

99th percentile of 1-hour 

daily maximum 

concentrations, averaged

over 3 years

Secondary 3-hour 0.5 ppm Not to be exceeded more 

than once per year

(1) The Final Rule was signed on October 15, 2008. The 1978 lead standard (1.5 μg/m3 as a quarterly 

average) remains in effect until 1 year after an area is designated for the 2008 standard. Areas 

designated nonattainment under the 1978 standard remain in effect until implementation plans are 

approved to attain or maintain the 2008 standard.

(2) The official level of the annual NO2 standard is 0.053 ppm, equal to 53 ppb, which is shown here for 

the purpose of clearer comparison to the 1-hour standard.

(3) The final rule was signed on October 1, 2015, and became effective on December 28, 2015. The 

previous (2008) O3 standards additionally remain in effect in some areas. Revocation of the previous 

(2008) O3 standards and transitioning to the current (2015) standards will be addressed in the 

implementation rule for the current standards.

(4) The Final Rule was signed on June 2, 2010. The 1971 annual and 24-hour SO2 standards were 

revoked in that same rulemaking. However, these standards remain in effect until 1 year after an area 

is designated for the 2010 standard, except in areas designated nonattainment for the 1971 

standards, where the 1971 standards remain in effect until implementation plans to attain or maintain 

the 2010 standard are approved.

Notes: PM – particulate matter; ppb – parts per billion; ppm – parts per million.

Source: USEPA, 2017a. 
Description of the Affected Environment and Impact Analysis 4-19

The Clean Air Act establishes classification designations based on regional monitored levels 

of ambient air quality. These designations impose mandated timetables and other requirements 

necessary for attaining and maintaining healthful air quality in the U.S. based on the seriousness of 

the regional air quality problem. These designations are nonattainment, attainment, and 

unclassifiable. Nonattainment is any area that does not meet the national primary or secondary 

ambient air quality standard for the pollutant. When measured concentrations of these regulated 

pollutants exceed the standards established by the NAAQS, the number of exceedances and the 

concentrations determine the nonattainment classification of an area. The Clean Air Act 

Amendments of 1990 established these designations as marginal, moderate, serious, severe, and 

extreme. Attainment is any area that meets the national primary or secondary ambient air quality 

standard for the pollutant. Unclassifiable is any area that cannot be classified on the basis of 

available information as meeting or not meeting the national primary or secondary ambient air quality 

standard for the pollutant. Figure 4-1 depicts all of the current nonattainment areas in the GOM 

region.

The Federal OCS waters are unclassifiable. The OCS areas are not classified because 

there is no regulatory provision for any classification in the Clean Air Act for waters outside of the 

boundaries of State waters. Only areas within State boundaries can be classified as either 

attainment or nonattainment.

Gulf of Mexico OCS Region Attainment Status

After promulgation of a NAAQS, the USEPA designates areas that fail to achieve the 

NAAQS as nonattainment areas, and States are required to submit State Implementation Plans to 

the USEPA; these plans contain emission control plans and a demonstration that the nonattainment 

area would achieve the NAAQS by the required date. After an area comes into attainment of the 

NAAQS, the area can be redesignated as a maintenance area and must continue to demonstrate 

compliance with the NAAQS. Figure 4-1 depicts all the current nonattainment areas in the GOM 

region while Table 4-3 summarizes the nonattainment and maintenance areas in the GOM region. 

Sulfur dioxide (SO2) and lead (Pb) nonattainment areas are focused around specific large industrial 

sources of SO2 or Pb emissions, whereas ozone nonattainment areas are more regional in nature, 

reflecting the formation of ozone as a secondary pollutant from emissions of NOx and VOC 

precursors from a wide range of sources. (Note: As November 1, 2016, the USEPA proposed to

redesignate the Baton Rouge, Louisiana, area as being in attainment of Federal health-based ozone 

standards. The State of Louisiana requested that the redesignation, based on 3 years of air quality 

data showing the metropolitan areas of Ascension, East Baton Rouge, Iberville, Livingston, and 

West Baton Rouge Parishes, meet the 2008 8-hour ozone standard of 0.075 parts per million [ppm]. 

The USEPA also proposes to approve the State’s plan for maintaining the standard.)
4-20 2018 Gulf of Mexico Supplemental EIS

Table 4-3. Nonattainment and Maintenance Areas in the Gulf of Mexico Region.

State Area 8-hr O3

(1997)

8-hr O3

(2008)

SO2

(2010)

Lead

(2008)

Alabama Troy NAA

Florida

Tampa NAA

Hillsborough County NAA

Nassau County NAA

Louisiana Baton Rouge M NAA

St. Bernard Parish NAA

Texas

Beaumont-Port Arthur M

Houston-Galveston-Brazoria NAA NAA

Frisco NAA

M = maintenance area; NAA = nonattainment area; O3 = ozone; SO2 = sulfur dioxide.

Blank cells indicate the area is in attainment of the National Ambient Air Quality Standards. 

As previously mentioned, the USEPA periodically modifies the NAAQS criteria based on new 

scientific knowledge. On October 1, 2015, the USEPA strengthened the 8-hour NAAQS for ozone to 

0.07 ppm (70 parts per billion [ppb]). Under this more stringent ozone NAAQS, there may be more 

areas in the southeastern U.S. designated as nonattainment. The USEPA plans to make attainment 

and nonattainment designations for the revised standards by October 2017, with the designations 

based on 2014-2016 air quality monitoring data.

In February 2010, the USEPA issued a new 1-hour NO2 NAAQS with a threshold of 100 ppb 

(98th percentile daily maximum average over 3 years), and a new 1-hour SO2 NAAQS was 

promulgated in June 2010 with a threshold of 75 ppb (99th percentile averaged over 3 years). The 

USEPA has not yet designated the nonattainment areas for the 1-hour NO2 and 1-hour SO2 NAAQS.

A lead NAAQS was issued in 2008; nonattainment areas for lead are associated with specific 

industrial sources. The USEPA has not yet designated the nonattainment areas for the lead

NAAQS.

The carbon monoxide NAAQS has remained essentially unchanged since it was originally 

promulgated in 1971. As of September 27, 2010, all prior CO nonattainment areas throughout the 

country have been redesignated as maintenance areas.

Emissions Inventories

One of the most accurate methods for estimating air emissions is by developing a 

comprehensive emissions inventory. To develop a calendar year 2011 inventory of criteria 

pollutants, criteria precursors, and greenhouse gas emissions for all OCS oil and gas productionrelated sources in the GOM, BOEM collected activity data from platform operators during the year 

2011. On September 15, 2010, NTL 2010-G06 was published to introduce the “2011 Gulfwide OCS 

Emissions Inventory (Western Gulf of Mexico)” and inform operators about the mandatory data 
Description of the Affected Environment and Impact Analysis 4-21

collection. Affected operators are lessees and operators of Federal oil, gas, and sulfur leases in the 

Gulf of Mexico OCS region west of latitude 87.5°. The USEPA jurisdiction has air quality jurisdiction 

east of latitude 87.5°.

BOEM updated and distributed a Microsoft® Visual Basic® program for platform operators to 

use to collect activity data on a monthly basis and submit to BOEM on an annual basis. The 

program, known as GOADS-2011, was used by operators to submit activity data for a number of 

production platform emission sources. Operators used the GOADS software to collect activity data 

for amine units, boilers/heaters/burners, diesel engines, drilling equipment, fugitives, combustion 

flares, glycol dehydrators, losses from flashing, mud degassing, natural gas engines, natural 

gas/diesel/dual-fuel turbines, pneumatic pumps, pressure/level controllers, storage tanks, and cold 

vents. These activity data were used to calculate CO, NOx, SO2, PM10, PM2.5, and VOC emissions 

estimates, as well as CO2, CH4, and N2O. The Gulfwide Oracle® DBMS calculates and archives the 

activity data and the resulting emissions estimates. Database users can query by pollutant, month, 

equipment type, platform, etc. Emission estimates for non-platform sources on the Gulf of Mexico 

OCS include both oil and natural gas production-related sources, as well as non-oil and natural gas 

sources. Production sources consist of survey vessels, drilling rigs, 

pipe-laying operations, and support vessels and helicopters. 

Non-oil and natural gas sources include commercial marine 

vessels, the Louisiana Offshore Oil Platform (LOOP), and biogenic 

and geogenic sources. Ultimately, State agencies and Regional 

Planning Organizations will use these offshore oil and gas platform 

and non-platform inventories to perform modeling for ozone and 

regional haze for use in their State Implementation Plans, and 

BOEM will use the emission inventory for the cumulative impact 

analysis in NEPA documents.

Emissions estimates calculated in the study were used to support analysis of air quality 

modeling impacts. In this inventory, emissions estimates are provided for directly emitted pollutants. 

While there are national air quality standards for six common air quality pollutants, only four of these 

pollutants (i.e., CO, Pb, NO2, and SO2) are directly emitted. Indirect emissions and the formation of 

other pollutants, as well as pollutants not included in the inventory, are analyzed below.

• Greenhouse Gases. Fluorinated gases, hydrofluorocarbons, and sulfur 

hexafluoride are not covered in this inventory because they are used in trace 

amounts and at no time are deliberately emitted into the atmosphere.

• Lead. Lead (Pb), a NAAQS criteria pollutant, is not covered in this inventory 

because oil and gas sources have negligible lead emissions. Since unleaded 

fuels have been phased out, lead remains a trace contaminant in other fuels 

(USEPA, 2016a).

• Nitrogen Dioxide. Nitrogen dioxide (NO2), a NAAQS criteria pollutant, is one of a 

group of highly reactive gases known as nitrogen oxides (NOx). Nitrogen oxides 

2011 GWEI Pollutants

NAAQS: CO, NOx, PM2.5, 

PM10, SO2

Criteria Precursors: VOC

Greenhouse Gases: CO2, 

CH4, N2O
4-22 2018 Gulf of Mexico Supplemental EIS

are stated as an equivalent mass of NO2; consequently, NOx is used instead of 

NO2. 

• Particulate Matter. Particulate matter (PM), a NAAQS criteria pollutant 

expressed as PM2.5 and PM10, can be emitted directly or it can be formed in the 

atmosphere when emissions of NOx, sulfur oxides (SOx), ammonia, organic 

compounds, and other gases react in the atmosphere. According to USEPA’s 

“Particulate Matter Emissions Report,” coarse PM (PM10) is composed largely of 

primary particles, while a much greater portion of fine PM (PM2.5) contains 

secondary particles. “Primary” particles are those released directly to the 

atmosphere whereas “secondary” particles are formed in the atmosphere from 

chemical reactions involving primary gaseous emissions. While both PM2.5 and 

PM10 are included the inventory, the secondary formation is not included the 

inventory because secondary PM is not directly emitted. Since the USEPA has 

not developed separate PM2.5 and PM10 emissions factors per source, 

particulate-matter emission estimates of PM2.5 and PM10 are similar. Therefore, 

PM10 values have been used in this chapter to represent particulate matter 

emission estimates.

• Ozone. Ozone (O3), an NAAQS pollutant, is not directly emitted into the air but is 

formed by photochemical reactions of NOx and VOCs in the presence of sunlight. 

Since NOx and VOCs are directly emitted pollutants, they are included in the 

emissions inventory, and their resulting emission estimates are used in the air 

quality model to analyze the air quality impacts of O3. 

Summary of Results of the Year 2011 Gulfwide Emissions Inventory

The Year 2011 GWEI results indicate that OCS oil and gas production platform and nonplatform sources emit the majority of NAAQS criteria pollutants, VOCs, and greenhouse gases on 

the Gulf of Mexico OCS, with the exception of SO2 (primarily emitted from commercial marine 

vessels), and N2O (from biological sources) (Wilson et al., 

2014). The total platform and non-platform emission 

estimates for criteria pollutants and the total platform and 

non-platform emission estimates for greenhouse gases 

are depicted in Figures 4-2 and 4-3, respectively. In both 

figures, total emission estimates are subdivided into three 

main categories: total non-OCS oil/gas source emissions; 

total OCS oil/gas non-platform source emissions; and total 

OCS oil/gas platform source emissions.

Total emissions estimates include

• total non-OCS oil and gas 

source emissions,

• total OCS oil and gas 

non-platform source emissions, 

and 

• total OCS oil and gas platform

production source emissions.
Description of the Affected Environment and Impact Analysis 4-23

Figure 4-2. Year 2011 Gulfwide Emission Inventory Results for Total Platform and Non-Platform Criteria 

Pollutant Emissions (TPY).

Figure 4-3. Year 2011 Gulfwide Emission Inventory Results for Total Platform and Non-Platform 

Greenhouse Gas Emissions (TPY). 

OCS Oil and Gas Platform 

Sources

OCS Oil and Gas Non Platform 

Sources

Non-OCS Oil and Gas Sources 

OCS Oil and Gas Platform 

Sources

OCS Oil and Gas Non Platform 

Sources

Non-OCS Oil and Gas Sources 
4-24 2018 Gulf of Mexico Supplemental EIS

Natural gas engines on platforms represented the 

largest CO emission source, and support vessels were the 

highest emitters of both NOx and PM10. Oil and natural gas 

production platform vents account for the highest percentage 

of the VOC emissions. Support vessels; production platform 

natural gas, diesel, and dual-fuel turbines; and commercial 

marine vessels emit the majority of the greenhouse gas 

emissions.

The Year 2011 GWEI results for criteria pollutant and greenhouse gas emissions (in 

tons/year) from platform sources are depicted in Figures 4-4 and 4-5, respectively. In both figures, 

each platform source emission type is represented per pollutant in tons/year.

Figure 4-4. 2011 Criteria Pollutant Emissions (TPY) from Platform Sources.

Figure 4-5. 2011 Greenhouse Gases (TPY) from Platform Sources.

Platform sources include

• criteria pollutants,

• emissions in (TPY),

• greenhouse gases, and

• emissions in (TPY).
Description of the Affected Environment and Impact Analysis 4-25

The Year 2011 GWEI results for criteria pollutant and greenhouse gas emissions (in 

tons/year) from non-platform sources (not pictured) indicate that support vessels emit the majority of 

the greenhouse gas emissions, as well as the highest emitter of both NOx and PM10 criteria 

pollutants.

4.1.2 Environmental Consequences

The impact-producing factors and their potential impacts identified for routine activities, 

accidental events, cumulative impacts, and incomplete or available information would apply, in 

general, to Alternatives A-D. These analyses are then applied to each alternative based on the 

varying degrees of forecasted levels of activities by geographical area and water depth. Following 

this environmental consequences discussion, there will be a summary of the potential impacts as 

they relate to the alternatives.

As discussed in the air quality introduction, the following list of impact-producing factors can 

occur in routine activities, accidental events, and cumulative impacts. The impact-producing factors 

include (1) OCS oil- and gas-related emissions sources related to drilling and associated vessel 

support, production, and the connected action of vessel support, flaring and venting, 

decommissioning, and oil spills; (2) non-OCS oil- and gas-related emissions such as State oil and 

gas programs, onshore industrial and transportation sources, and natural events; and (3) the 

incremental contribution of all postlease activities as a result of a single proposed lease sale. These 

impact-producing factors can produce greenhouse gas and fugitive emissions, which are discussed 

below.

Greenhouse Gases and Fugitive Emissions

Greenhouse Gases Including Downstream Gas

Chief among drivers of climate change are increasing atmospheric concentrations of carbon 

dioxide (CO2) and other greenhouse gases, such as methane (CH4) and nitrous oxide (N2O). These 

greenhouse gases reduce the ability for solar radiation to re-radiate out of the Earth’s atmosphere 

and into space. Although all three have natural sources, these three greenhouse gases comprise 

the majority of greenhouse gases released from anthropogenic sources; CO2 and N2O are released 

in association with combustion and CH4 and N2O are released as a byproduct of agriculture and also 

oil and gas production. Hydrofluorocarbons and sulfur hexafluoride are two fluorinated greenhouse 

gases that are used on the OCS, but they are used in trace amounts and are at no time deliberately 

emitted into the atmosphere.

The activities associated with a proposed action would increase global greenhouse gas 

emissions from the use of vessels, drilling equipment, and other activities that burn fossil fuels. In 

addition, CH4, also known as natural gas, is removed from wells and brought onto OCS facilities 

along with oil being produced. Sometimes CH4 is released as a fugitive gas that can escape 

unintentionally from leaks in equipment used by operators. Operators have the four following 

methods of managing natural gas removed from wells: (1) production – selling the natural gas, 
4-26 2018 Gulf of Mexico Supplemental EIS

provided there is a sufficient quantity, favorable market conditions, and infrastructure (e.g., natural 

gas pipelines) to justify production; (2) reinjection – the natural gas is directed back into the reservoir 

to aid in oil extraction; (3) venting – the deliberate release of natural gas into the atmosphere; and 

(4) flaring – burning the natural gas, converting it to CO2 and water, and in some cases, also 

releasing N2O and black carbon. This practice is rare on the OCS.

Because each greenhouse gas impacts the atmosphere at a different strength and for a 

different period of time, for analytical purposes, they typically are converted to what the strength 

would be if emissions were exclusively CO2; this is referred to as the CO2-equivelent (CO2e) to 

facilitate comparison. CH4 and N2O are much more effective climate forcers than CO2, meaning 

1 ton of CH4 or N2O has a greater impact on climate change than 1 ton of CO2. However, CH4 and 

N2O are removed from the atmosphere through natural processes more efficiently than CO2. 

Accounting for these factors, CO2e conversion for CH4 and N2O are 25 and 298, respectively 

(Brander, 2012). This means that 1 ton of CH4 is estimated to have the same warming potential as 

25 tons of CO2, and 1 ton of N2O would have the same impact as 298 tons of CO2. Because black 

carbon is not a greenhouse gas and functions differently, it is not possible to convert it using the 

CO2e method. However, because black carbon is a specific kind of PM2.5, it is possible to use the 

PM2.5 concentration to estimate the maximum amount of black carbon released. BOEM has 

regulatory authority on the OCS for PM2.5, along with several other air quality pollutants.

As a result of exploration, development, and production of oil and gas on the OCS, the 

activities associated with a proposed action are expected to release greenhouse gases and black 

carbon from the use of combustion engines in vessels, construction, drilling, and other equipment, 

as well as through the deliberate or accidental release of CH4. Emissions estimates for the activities 

associated with a proposed action, and for cumulative BOEM-related OCS emissions, were 

calculated using the Offshore Environmental Cost Model. These estimates are for the high-price 

scenario, which would likely result in the highest level of potential emissions for a proposed action. 

Cumulative numbers include current operations, the activities associated with a proposed action, 

and expected future development beyond a proposed action. Unlike the greenhouse gases, which 

warm the planet generally, black carbon’s potential to contribute to climate change has a spatial 

component. Compared with the 2012-2017 Five-Year Program, the activities associated with a 

proposed action would result in an overall increase in the rate of CO2e emissions from OCS oil- and 

gas-related activities.

In addition to the direct emissions from OCS oil- and gas-related operations presented 

above, BOEM has evaluated greenhouse gas emissions covering the lifecycle of OCS oil and gas 

production and consumption. This includes both the “downstream” consumption and onshore 

processing of oil and gas products, as well as the “upstream” emissions from offshore exploration, 

development, and production.

The expected greenhouse gas emissions for the low- and high-price scenarios include 

numerous assumptions (Wolvovsky and Anderson, 2016); therefore, while being a reasonable 

approximation, these numbers are an estimate and not a forecast. However, because the 
Description of the Affected Environment and Impact Analysis 4-27

methodology used to compare the two price scenarios and the No Action Alternative are the same, 

the analysis can be assumed to provide a relative comparison. There is a significant degree of 

uncertainty in these numbers, and they do not take into account future Federal, State, and/or local 

economic, social, policy, regulatory, and legislative changes that could affect the amount of 

greenhouse gases released. In addition, this analysis is bounded by U.S. consumption and the 

upstream domestic and overseas production supporting American consumption. This means that 

the likely overseas reduction in consumption under the No Action Alternative is not calculated in this 

analysis.

On April 22, 2016, the United States joined the Paris Agreement, a United Nations-brokered 

agreement to keep global temperatures within 2 °C (36 °F) of the pre-industrial climate, and 

preferably within 1.5 °C (35 °F) (United Nations Framework Convention on Climate Change, 2016). 

A recent study (McGlade and Ekins, 2015) states that, to prevent the planet from warming beyond 

2 °C (36 °F), emissions of greenhouse gases must be kept below 1,100 billion tons of CO2e between 

2011 and 2050. McGlade and Elkins (2015) also discuss the need to greatly reduce the amount of 

oil and gas extraction to stay under this threshold, with particular emphasis on not drilling in the 

Arctic. It should be noted that the 2 °C (36 °F) warming threshold would still result in significant 

impacts on the world’s ecosystems and to humanity (Hansen et al., 2016).

The U.S. has pledged to reduce emissions by filing an Intended Nationally Determined 

Contributions with the United Nations. The American Intended Nationally Determined Contributions 

commitment is to reduce net greenhouse gas emissions by 17 percent below 2005 levels by 2020 

and by 26-28 percent by 2025 (United Nations Framework Convention on Climate Change, 2016). 

In addition, the Obama Administration set a target to reduce U.S. greenhouse gas emissions by at 

least 80 percent by 2050 (The White House, 2015). In 2005, the U.S. had net emissions of 

6,680,300,000 metric tons of CO2e (Brander, 2012).

The activities associated with the proposed action’s lifecycle emissions fluctuate over the 

course of the 2017-2022 Five-Year Program in the GOM, with early emissions largely coming from 

OCS sources. The greenhouse gas emissions would peak in the 2030s and 2040s, at the same 

time as production peaks. Overall, the greenhouse gases from the activities associated with the 

proposed action would be similar to but slightly lower than the No Action Alternative in both low- and 

high-price scenarios. This similarity is due to the economic substitution effects from onshore and 

overseas sources expected under the No Action Alternative.

Additional sector-specific goals, such as the United States’ commitment with Canada and 

Mexico to achieve 50 percent of electricity from noncarbon sources (The White House, 2016) and 

other yet-to-be determined measures, could significantly affect how oil and gas products are used 

and the emissions resulting from that consumption. Policies already determined and implemented 

have been included in the lifecycle analysis. The high- and low-price scenarios are intended to 

provide the upper and lower bounds of possible emissions scenarios. Overall, implementation of 

U.S. climate goals through future policies and regulations would be expected to reduce overall oil 
4-28 2018 Gulf of Mexico Supplemental EIS

and gas demand, making it unlikely that the estimated emissions presented for the high-price 

scenario would be realized.

Fugitive Emissions

Fugitive emissions are not intentionally released through a stack, vent, or flare, but they are 

instead caused by leaks or intermittently escapes from pressurized equipment from sealed surfaces 

in various components of the facility. Fugitive emissions are mainly comprised of VOCs and 

methane (CH4). Sources of fugitive emissions typically include valves, flanges, connectors, pumps, 

and compressor seals, but they may also include other platform components such as pneumatic 

controllers. Fugitive emissions can occur during all phases of OCS oil- and gas-related activity.

According to the Year 2011 GWEI study, fugitive emissions constitute one of the largest 

VOCs and CH4 emissions sources from offshore oil and gas platforms, behind only cold vents. The 

BSEE personnel have indicated that the infrared camera surveys, performed to detect hydrocarbon 

leaks during inspections of offshore platforms, show very few, if any, hydrocarbon leaks. This could 

imply that the current emission factors may be overestimating VOC and methane emissions. 

Several State coastal areas have been designated nonattainment for ozone. Since ozone is formed 

by the combination of VOCs and NOx, the OCS emissions inventory for VOCs needs to be as 

accurate as possible. In addition, the Government Accountability Office has published Opportunities 

Exist to Capture Vented and Flared Natural Gas, Which Would Increase Royalty Payments and 

Reduce Greenhouse Gases (U.S. Government Accountability Office, 2010) looking to reduce CH4

emissions by the installation of control technology on platforms. Before control technology is 

required, the OCS emissions inventory for CH4 also needs to be as accurate as possible.

Based on the results of the emission inventory study, as well as correspondence with BSEE, 

and the GAO report, BOEM wants to further assess emissions from fugitive equipment leaks on 

offshore oil and gas platforms operating on the Gulf of Mexico OCS. Under BOEM’s Contract 

Number M16PC00010, “Fugitive Emissions Update in the Outer Continental Shelf,” the objective is 

to visit offshore production platforms to identify and conduct the testing of fugitive equipment leaks in 

order to develop updated VOC, select hazardous air pollutant, and methane emission factors. 

These updated emission factors would be used by BOEM to develop improved and contemporary 

emissions inventories that will be used for a variety of purposes, including future photochemical grid 

modeling conducted by states in the Gulf of Mexico region for State Implementation Plan compliance 

demonstrations. However, if the OCS emissions inventories are overestimating VOC and methane 

emissions, then possibly control technologies would not be required. These study results are 

projected to be available by spring of 2019. Otherwise, BOEM would determine the appropriate use 

of control technologies on the platforms during postlease reviews.

4.1.2.1 Routine Activities

The primary routine impact-producing factors associated with the proposed action that could 

potentially affect air quality and that also could contribute to climate change include (1) drilling and 

production and the associated vessel support, (2) flaring and venting, and (3) decommissioning of 
Description of the Affected Environment and Impact Analysis 4-29

facilities. These routine activities result in pollutant emissions. Emissions of air pollutants from 

these activities would occur during exploration, development, production, and decommissioning 

activities.

Drilling and Production with Associated Vessel Support

Since both drilling and production activities include associated vessel support, the activities 

are analyzed together in this section. Emissions during exploration are higher than emissions during 

development due to power requirements for drilling a deeper wellbore hole. During drilling, diesel 

engines are used to power the drilling (top drive) assembly, draw works, electrical generators, mud 

pumps, vessel propulsion (drillships and support vessels)), and dynamic positioning systems of the 

drilling rig (if a dynamic positioning semisubmersible or dynamic positioning drillship is used). 

Combustion of fuel to run the engines generates NAAQS criteria pollutants, VOCs, and greenhouse 

gases. More information about the pollutants that are generated by specific equipment and activities 

is available in the Year 2011 Gulfwide Emission Inventory Study (Wilson et al., 2014). As illustrated 

in Figure 3-2, during a 50-year analysis period, exploratory drilling mainly occurs during the first 

decade and development drilling extends throughout the first and second decade.

We know from Chapter 3 that, during production, pollutants emitted during routine activities 

may be combustion products of burning fuel to power pumps, compressors, or generators, or they 

may consist of fugitive VOCs, which escape from the un-combusted hydrocarbons. The platform 

emission sources include boilers, turbines, pneumatic pumps, diesel engines, combustion flares, 

fugitives, glycol dehydrators, natural gas engines, pressure/level controllers, storage tanks, cold 

vents, and others. As illustrated in Figure 3-2, during a 50-year analysis, most production occurs 

during the second and third decade. Because the levels of activity in the 2011 GWEI are projected 

to be less than a proposed lease sale, these emission values are used to project potential impacts 

as described below.

The OCS emissions in tons per year for the criteria pollutants and for the greenhouse gases 

from platform sources are indicated in Figures 4-4 and 4-5. The distribution of emissions across 

various platforms sources would be expected to be similar. These figures show the following: 

criteria pollutants – the major pollutant emitted is NOx, while PM10 is the least emitted pollutant; and 

greenhouse gases – the major pollutant emitted is CO2, while N2O is the least emitted pollutant. 

Combustion-intensive operations such as platform operations, well drilling, and service-vessel 

activities contribute mostly NOx and CO2; platform operations are also the major contributors of VOC 

emissions. As a result of a proposed lease sale, multiple platforms would be installed on the leases, 

and platform construction emissions would contribute appreciable amounts of all pollutants over the 

resulting lease sale’s 50-year analysis period. Emissions from a singular platform construction are 

temporary in nature and generally occur for a period of 3-4 months. Typical construction emissions 

result from the derrick barge placing the jacket and various modular components and from various 

service vessels supporting this operation. Drilling operations contribute considerable amounts of all 

pollutants. These emissions are temporary in nature and typically occur over a 90-day per well 

drilling period. Support vessels for OCS oil- and gas-related activities, as described in Chapter 
4-30 2018 Gulf of Mexico Supplemental EIS

3.1.4.4, include emissions of NOx, CO, and CO2. These emissions are directly proportional to the 

number and type of OCS operations requiring support activities. Most emissions from these support 

activities occur during transit between the port and offshore facilities; a smaller percentage of the 

emissions occur during idling at the platform.

Currently, there are minor impacts occurring to air quality from drilling and production with 

associated vessel support impacts as shown in the model. Therefore, because the projected 

activities in this scenario for a proposed lease sale are less than the current 2011 GWEI activities, 

the impacts would be minor. The activities’ impacts would vary in intensity based on the type and 

location of the activity.

Flaring and Venting

Reasonably foreseeable flaring and venting emissions operations occur intermittently for 

short periods of time over the life of the lease. Flaring systems are also used to vent natural gas 

during well testing or during repair/installation of production equipment. The BSEE operating 

regulations at 30 CFR § 250.1160 provide for some limited volume, short-duration flaring, or venting 

of some natural gas volumes upon approval by BSEE. These operations may occur for short 

periods of time (typically 2-14 days) as part of unloading/testing operations that are necessary to 

remove potentially damaging completion fluids from the wellbore, to provide sufficient reservoir data 

for the operator to evaluate a reservoir and development options, and in emergency situations. The 

potential impacts from these emergency operations are described in the “Accidental Events” chapter 

below and in Chapter 3.2.3. 

Flaring may involve the disposal of sweet gas or sour gas. Sweet gas is natural gas that 

does not contain hydrogen sulfide (H2S), while sour gas is natural gas that does contain H2S. During 

the flaring of gas containing H2S, the gas entering the flare would largely combust to SO2. The 

contribution of flaring sour gas to SO2 is regulated in 30 CFR part 250 subpart K. The SO2 levels 

from reasonably foreseeable flaring are evaluated as part of the postlease plans review process.

Hydrogen sulfide released to the air can come from natural sources such as swamps, bogs, 

and volcanoes. Hydrogen sulfide can also be released from industrial sources such as petroleum 

refineries, natural gas plants, kraft paper mills, manure treatment facilities, waste-water treatment 

facilities, and tanneries. The concentration of H2S occurring naturally in crude oil varies from 

formation to formation and even varies to some degree within the same reservoir. The natural gas in 

deepwater reservoirs has been mainly sweet (i.e., low in sulfur content), but the oil averages 

between 1 and 4 percent sulfur content by weight. By far, most of the documented production of 

sour gas (i.e., high sulfur content) lies within 150 km (93 mi) of the Breton Wilderness Area Class I 

area. The BSEE regulations at 30 CFR § 250.490(f) describe safety precautions for employees 

operating in an H2S area. Hydrogen sulfide is a naturally occurring compound that is formed from 

the breakdown of organic matter in low oxygen environments. The effects of H2S depend on the 

magnitude, duration, and frequency of exposure, as well as the susceptibility of the individual 

organism or environment. The human nose is very sensitive and can detect extremely low levels of 

H2S. A rotten egg odor characterizes H2S at very low concentrations. However, prolonged 
Description of the Affected Environment and Impact Analysis 4-31

exposure to low levels of H2S can cause skin irritation and olfactory paralysis. Therefore, relying on 

odor or sense of smell would not be a reliable warning signal to detect H2S presence. Short-term 

exposure to high concentrations of H2S can cause death. Portable monitors worn by workers, as 

well as visual and audible alarms and H2S sensors on platforms to activate when the presence of 

H2S is detected, can help to prevent loss of life. According to the NPS, Gulf Islands National 

Seashore visitors have complained about H2S odors. BOEM expects that concentrations at the 

park, resulting from OCS sources of H2S, to be at very low nuisance levels. The source of odors in 

the park may include releases from the local marsh muds or nearby State oil and gas activity. 

Therefore, several contributing factors could be responsible for the odors at Gulf Islands National 

Seashore.

Impacts to air quality from reasonably foreseeable flaring and venting would be minor

because the activity is short in duration during a 50-year analysis period, and release likely 

dissipates before reaching coastal areas due to distance. The impacts would vary in intensity based 

on the type of flare and location of the activity.

Decommissioning

During a 50-year analysis period, most decommissioning occurs during years 20-40. 

Decommissioning emissions are due mainly to engines on vessels used in the decommissioning 

process for propulsion, electrical power, and ancillary mechanical equipment and activities. These 

emissions include the following pollutants: CO, NO2, PM, SO2, CO2, CH4, N2O, and VOCs. There 

are two primary methodologies used in the GOM for cutting decommissioning targets: nonexplosive 

and explosive severance. Nonexplosive methods include abrasive cutters, mechanical cutters, 

diamond wire cutting devices, and cutting facilitated by commercial divers using arc/gas torches. 

Though a relatively slow process and potentially dangerous for offshore workers, nonexplosiveseverance activities have little to no impact on air quality. Explosive-severance activities use 

specialized charges to achieve target severance. Unlike most nonexplosive methods, severance 

charges can be deployed on multiple targets and detonated nearly simultaneously, effecting rapid 

severances. Though a relatively faster yet safer process for offshore workers with the omission of 

diver cutting, the detonation of cutting charges occurs mainly underwater and, therefore, would have 

little impact on air quality. The impacts would vary in intensity based on the type and location of the 

activity. The main concern of air quality from decommissioning is the exhaust from support 

equipment. The less time that heavy equipment must be employed during decommissioning, the 

less air quality would be negatively impacted. Overall, impacts to air quality from decommissioning 

would be minor. 

4.1.2.2 Accidental Events

The greatest impact-producing factors associated with a proposed action that could 

potentially affect air quality from a reasonably foreseeable accidental event include (1) emergency 

flaring and venting, and (2) oil spills. Accidental air emissions are described in Chapter 3.2.3. 
4-32 2018 Gulf of Mexico Supplemental EIS

Emergency Flaring and Venting

Emergency flaring is distinguished from routine flaring by the magnitude, frequency, and 

duration of flaring events. Emergency flaring events are the result of operating conditions that are 

outside normal process and equipment operations. Emergency flaring is generally characterized by 

infrequent occurrence, high-emission rates, and short durations. Potential impacts to air quality are 

not expected to be significant, except in the rare case of a catastrophic event, which is not part of a 

proposed action and not reasonably foreseeable. Emergency flaring may be conducted to manage 

excess natural gas during an accidental event, such as damage to a pipeline that transports the gas 

to shore, or a process upset. In the absence of safety flares, plants would be at a higher risk for fires

and explosions. The flare is operated temporarily until the emergency situation is resolved. Flaring 

would result in the release of NOx emissions from the flare; SO2 emissions would be dependent on 

the sulfur content of the crude oil; and particulate matter from the flare would affect visibility.

Venting would result in the release of mainly CH4 emissions. Emergency venting may be 

necessary where flaring of the gas is not possible or in situations precluding the use of a flare gas 

system, such as insufficient hydrocarbon content in the gas stream to support combustion or a lack 

of sufficient gas pressure to allow it to enter the flare system. Therefore, the potential impacts of a 

reasonably foreseeable accidental gas release analyzed in this Supplemental EIS would be localized 

and short term, and would have no impact to coastal areas, including the Bradwell Bay Wilderness 

Area, Breton Wilderness Area, Chassahowitza National Wilderness Area, Everglades National Park, 

and St. Marks Wilderness Area, or the Padre Island National Seashore and Gulf Islands National 

Seashore. The accidental event’s impacts on air quality over the OCS and adjacent onshore areas 

on accidental gas releases are expected to be minor. 

The accidental release of hydrocarbons related to a proposed lease sale would result in the 

emission of air pollutants. The OCS accidents would 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 NAAQS pollutants, volatile and semi-volatile organic compounds, hydrogen 

sulfide, and methane. These pollutants are discussed above. These accidental events may 

potentially affect the air quality at the Bradwell Bay Wilderness Area, Breton Wilderness Area, 

Chassahowitza National Wilderness Area, Everglades National Park, and St. Marks Wilderness 

Area, as well as the Padre Island National Seashore and Gulf Islands National Seashore, during a 

50-year analysis period.

Emergency flaring may be conducted to manage excess natural gas during an accidental 

event such as damage to a pipeline that transports the gas to shore or a process upset. In the 

absence of safety flares, plants would be at a higher risk for fires and explosions. The flare is 

operated temporarily until the emergency situation is resolved. Flaring would result in the release of 

NOx emissions from the flare; SO2 emissions would be dependent on the sulfur content of the crude 

oil; and particulate matter from the flare would affect visibility.
Description of the Affected Environment and Impact Analysis 4-33

Oil Spills

Accidental oil spills, though not considered a routine OCS oil- and gas-related activity, have 

the potential to occur during each phase of oil and gas operations. In April 2010, the Deepwater 

Horizon explosion and oil spill was a catastrophic event that occurred on the Gulf of Mexico OCS. 

The impacts on air quality from the Deepwater Horizon explosion and oil spill have been well 

documented. BOEM does not expect accidental events to resemble the Deepwater Horizon

explosion and oil spill. BOEM is not analyzing the rare, catastrophic Deepwater Horizon explosion 

and oil spill as an accidental event in this chapter but rather is using the information to describe the 

potential impacts common to spills and accidental events regardless of size. Additionally, BOEM 

has assessed the potential impacts resulting from a low-probability catastrophic event, and the 

analysis is presented in the Catastrophic Spill Event Analysis white paper (USDOI, BOEM, 2017b). 

To date, air monitoring conducted following the Macondo loss of well control and spill has not found 

any pollutants at levels expected to cause long-term harm (USEPA, 2010). The loss of well control 

and blowouts are rare events and of a short duration. Potential impacts to air quality are not 

expected to be significant, except in the rare case of a catastrophic event, which is not reasonably 

foreseeable and not part of a proposed action. Therefore, potential impacts as a result of the much 

smaller reasonably foreseeable accidental spills analyzed in this Supplemental EIS would be 

localized and short term, and would have no impact to coastal areas, including the Bradwell Bay 

Wilderness Area, Breton Wilderness Area, Chassahowitza National Wilderness Area, Everglades 

National Park, and St. Marks Wilderness Area, as well as the Padre Island National Seashore and 

Gulf Islands National Seashore. The accidental event’s impact on air quality over the OCS and 

adjacent onshore areas on oil spills is therefore expected to be minor. 

In the Gulf of Mexico, evaporation from an oil spill would result in concentrations of VOCs in 

the atmosphere, including chemicals that are classified as being hazardous. Benzene, toluene, 

ethylbenzene and xylene (BTEX) are a category of VOCs that occur naturally in crude oil, as well as 

during the process of making of gasoline and other fuels from crude oil. 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, such as BTEX, would be most abundant in the immediate vicinity of the spill site. The 

heavier compounds would be emitted over a 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. In hazardous 

conditions, the Occupational Safety and Health Administration and USCG regulations require 

workers to use breathing protection. The hazard to workers can also be reduced by limiting 

exposure through limited work shifts, rotating workers in close vicinity of the spill site, and pointing 

vessels into the wind. While the reasonably foreseeable spills analyzed as part of this Supplemental

EIS are significantly smaller than the catastrophic Deepwater Horizon explosion and oil spill, air 

samples collected during that event by individual offshore workers of British Petroleum (BP), the 

Occupational Safety and Health Administration (OSHA), and the USCG showed levels of BTEX that 

were mostly under detection levels. All samples had concentrations below the OSHA permissible 

exposure limits and the more stringent American Conference of Governmental Industrial Hygienists 
4-34 2018 Gulf of Mexico Supplemental EIS

threshold limit values (U.S. Dept. of Labor, OSHA, 2010). Therefore, the reasonably foreseeable oil 

spills would be expected to be even smaller.

The VOC emissions that result from the evaporation of oil contribute to the formation of 

particulate matter (PM2.5) in the atmosphere (Brock et al., 2012). 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. Effects to ozone concentrations would 

depend on distance of the proposed lease sale area from shore and the accidental spill size. If there 

were any effects to onshore ozone concentrations to a state, they would likely be temporary in 

nature and last, at most, the length of time of the spill’s duration.

Removal and containment efforts to respond to an ongoing offshore spill would likely require 

multiple technologies, including source containment, mechanical cleanup, in-situ burning of the slick, 

and chemical dispersants (Chapter 3.2.7). In-situ burning would result in ambient concentrations of 

CO, CO2, NOx, PM10, PM2.5, and SO2 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.

4.1.2.3 Cumulative Impacts

An analysis of the cumulative impacts in the GOM region is described in this chapter. This 

cumulative analysis considers OCS oil- and gas-related and non-OCS oil- and gas-related activities 

that could occur and adversely affect air quality during the 50-year analysis period.

Under BOEM Contract Number M14PC00007, “Air Quality Modeling in the Gulf of Mexico 

Region” study, photochemical grid modeling was conducted to assess the impacts to nearby states 

of existing and proposed future OCS oil and gas exploration, development, and production. 

Preliminary results from the modeling conducted for this study have become available and are being 

included in this Supplemental EIS to disclose potential cumulative and incremental air quality 

impacts of the proposed lease sales. These preliminary results represent the best available science 

at this time and are included in Appendices B-D. At the lease issuance stage, no activities beyond 

certain ancillary activities are actually authorized by the lease; therefore, there are few 

environmental impacts, including air quality, reasonably expected from a proposed lease sale itself 

(refer to Chapter 1.2.1). During postlease activities, BOEM has the authority to disapprove or 

require additional mitigation to reduce impacts from site-specific activities as additional information 

becomes available.

The air quality modeling study examines the potential impacts of the proposed lease sales 

with respect to (1) the NAAQS for the criteria pollutants O3, NO2, SO2, CO, PM2.5, PM10; (2) the 

Class I and Class II PSD increments; and (3) the AQRVs, including visibility and acid deposition 

(sulfur and nitrogen) in the nearby Class I and sensitive Class II areas.
Description of the Affected Environment and Impact Analysis 4-35

Results of each impact analysis are compared with applicable “thresholds of concern,” which 

have typically been used in air quality impact evaluations by other Federal actions, including onshore 

oil and gas leasing programs. The applicable comparison thresholds for criteria pollutant impacts 

are the corresponding NAAQS. For acid (i.e., sulfur and nitrogen) deposition impacts, thresholds are 

based on (1) incremental impacts considered sufficiently small as to have no consequential effect on 

the receiving ecosystems, i.e., Deposition Analysis Thresholds, and (2) critical load levels above 

which cumulative ecosystem effects are likely to or have been observed. For visibility impacts, 

thresholds are based on incremental changes in light extinction below the level at which they would 

be noticeable to the average human observer. Additional information about these various thresholds 

is provided in relevant chapters in the remainder of this Supplemental EIS.

Overview of Modeling Approach

The Comprehensive Air-quality Model with extensions (CAM) and Community Multiscale Air 

Quality (CMAQ) photochemical grid models were used to simulate the dispersion and chemical 

transformation of pollutants over the study area. Similar to other air quality models, CAMx/CMAQ 

require several input datasets, including meteorology and an emissions inventory. Figure 4-6

presents an overview of how these project datasets fit together for the “Air Quality Modeling in the 

Gulf of Mexico Region” study. Photochemical modeling was conducted for two emission scenarios:

(1) a Base Case scenario using the 2012 base year (BY) emissions inventory 

described in Appendix C to evaluate model performance and to define current 

baseline air quality conditions; and

(2) a Future Year development scenario (FY) using an emissions inventory that 

includes potential new sources associated with the lease sales analyzed for the

Supplemental EIS and the projections of emissions to 2017 for all other sources 

as described in Appendix C to estimate the cumulative and incremental air 

quality and AQRV impacts of the lease sales analyzed in this Supplemental

EIS.

NOTE: Both scenarios used the same 2012 meteorological dataset and the same 

photochemical model configuration. (In determining the Base Case [base year] for the “Air Quality 

Modeling in the Gulf of Mexico Region” study emissions inventory, 2011 was initially selected based 

on data availability. Calendar year 2011 emissions data are readily available for most sources from 

the USEPA’s National Emissions Inventory [USEPA, 2017b and 2017c] and the BOEM’s Year 2011 

Gulfwide Emissions Inventory Study [Wilson et al., 2014]. However, 2011 was an unusually hot and 

dry year in the Gulf of Mexico region, particularly in Texas, which experienced record heat and dry 

conditions during the summer of 2011 and which had a very high incidence of wildfires. Therefore, 

2012 was selected as the base year as more representative of “typical” conditions in the Gulf of 

Mexico region.) 
4-36 2018 Gulf of Mexico Supplemental EIS

Figure 4-6. Overview of the Gulf of Mexico Region’s Cumulative 

and Visibility Impacts Assessment.

Modeling Input – Meteorological Modeling

Meteorological datasets required to determine the rate that pollutants disperse and react in 

the atmosphere include spatially and temporally varying parameters such as wind speed, wind 

direction, air temperature, and humidity, among others. Sources of meteorological information 

include datasets of measurements gathered at various locations within the Gulf of Mexico region 

domain, i.e., the area of interest where geographic features influence transport patterns. Results of 

these meteorological models provide the inputs needed to exercise the photochemical grid air quality 

dispersion models used in the “Air Quality Modeling in the Gulf of Mexico Region” study. For this 

study, the Advanced Research version of the Weather and Research Forecasting (WRF) model, as 

described in Appendix B, was applied over a system of nested modeling grids. Figure 4-7 shows 

the WRF modeling grids at horizontal resolutions of 36, 12, and 4 km. All WRF grids were defined 

on a Lambert Conformal Conic (LCC) projection centered at 40° N. latitude, 97° W. longitude with 

true latitudes at 33° N. latitude and 45° N. latitude (the “standard RPO” projection). In Figure 4-7, 

the outermost domain (outer box) with 36-km resolution includes the entire continental U.S. and 

parts of Canada and Mexico, and captures synoptic-scale (storm system-scale) structures in the 

atmosphere. The inner 12-km regional grid (d02) covers the southeastern U.S. and is used to 

ensure that large-scale meteorological patterns across the region are adequately represented and to 

provide boundary conditions to the 4-km domain. The 4-km domain (d03) is centered on the coastal 

areas of the southeastern U.S. and over-water portions of the Gulf of Mexico. The 4-km domain 

area, which includes parts of Alabama, Georgia, Louisiana, Mississippi, and Texas, and all of 

Florida, as well as the WPA, CPA, and EPA, and part of the Atlantic Ocean, was the main focus of 

the emissions inventory efforts. However, the focus of this Supplemental EIS analysis are the 

coastal areas adjacent to the WPA, CPA, and EPA, which include Texas, Louisiana, Mississippi, 

Alabama, and Florida.
Description of the Affected Environment and Impact Analysis 4-37

Figure 4-7. Geographic Domain of the “Air Quality Modeling in the Gulf of Mexico” 

Region Study.

Modeling Input – Emissions Inventories

Analysis of the cumulative air quality impacts of this Supplemental EIS required the 

development of both a contemporary base year emissions inventory for the base case analysis and 

a projected future year inventory that includes emissions from all cumulative sources, as well as 

additional emissions anticipated to occur under this Supplemental EIS’ alternative in which additional 

exploratory drilling and construction of new shallow and deepwater platforms to support oil and gas 

production would occur. Both the base case and future year cumulative source inventories 

represent comprehensive compilations of pollutant emissions from all human activities as well as 

emissions from biogenic and geogenic sources. Specific details on the development of the emission 

inventory are presented in Appendix C. The scope of the air pollutant emissions inventory for the 

“Air Quality Modeling in the Gulf of Mexico Region” study is defined in terms of pollutants, 

representative time periods for the base case and future year analysis, geographical domain, and 

sources to be included.

Pollutants included in the inventories were selected to support analysis of air quality impacts 

in terms of impacts on attainment of the NAAQS and on AQRVs, including acid deposition and 

visibility. The selected pollutants are as follows: the NAAQS criteria pollutants – CO, NOx (which 

includes NO and NO2 and is stated in terms of equivalent mass of NO2), PM2.5, fine plus coarse PM 

(PM10), and SO2; criteria precursors – VOCs (which are precursors to the formation of ozone and 
4-38 2018 Gulf of Mexico Supplemental EIS

organic particulates) and ammonia (NH3) (which is a precursor to particulate matter formation). As 

previously mentioned in Chapter 4.1.1, lead (Pb) was not included in the inventory. While the 

cumulative air quality impact analysis did not focus specifically on air toxics, the compilation of VOC 

emissions by source type, together with VOC speciation profiles by source type, provides a 

mechanism for estimating emissions of individual air toxic species.

Overview of Modeling Results 

The post-processed results for comparison to the NAAQS, PSD increments, and visibility 

and acid deposition thresholds are described below. The results in this section are still preliminary, 

but are being used to disclose the potential cumulative impacts to coastal areas.. Specific 

cumulative impact analysis results from the “Air Quality Modeling in the Gulf of Mexico Region” study 

are presented in Appendix D. 

The CAMx future year scenario model and ozone and particulate matter source 

apportionment modeling outputs were post-processed for comparison against the NAAQS and PSD 

concentration increments, and other thresholds of concern as discussed below. For analyzing the 

NAAQS and AQRV impacts at Class I and sensitive Class II areas, the thresholds of concern used 

were as defined by the Federal Land Manager that manages each Class I/II area.

Source apportionment provides a means of assessing the contributions of specified sources 

or categories of sources to predicted ozone and PM concentrations and their precursors under the 

air quality conditions being simulated. Source contributions were calculated for ozone and PM using 

the Ozone and Particulate Source Apportionment Technology (OSAT and PSAT) routines included 

in CAMx. Source apportionment analyses were applied to the future year scenario in order to 

analyze the pre- and postlease OCS oil- and gas-related impacts to short-term and annual NAAQS, 

AQRVs, and PSD increments. While BOEM selected nine source categories for the CAMx future 

year source apportionment simulation as listed in Table 4-4, only four are appropriate for this 

Supplemental EIS analysis because they apply to the Gulf of Mexico region.

Table 4-4. Source Categories for Source Apportionment Calculations.

Category ID Sources

SC3 Additional BOEM OCS oil and gas production platforms associated with 

this Supplemental EIS (with Action)

SC4 Additional BOEM oil and gas production support vessels and helicopters 

associated with this Supplemental EIS (with Action)

SC5 BOEM’s OCS oil and gas production platforms, support vessels, and 

helicopters under the base case (No Action)

SC6 All other marine vessel activity in the Gulf of Mexico not associated with 

OCS oil and gas development, exploration, or production

SC = source category.
Description of the Affected Environment and Impact Analysis 4-39

4.1.2.3.1 Impacts Assessment

NAAQS Impacts

The impacts for the NAAQS criteria pollutants ozone (O3), nitrogen dioxide (NO2), sulfur 

dioxide (SO2), carbon monoxide (CO), fine particulate matter with aerodynamic diameter less than 

2.5 μm (PM2.5), and fine plus coarse particulate matter with aerodynamic diameters less than 10 μm 

(PM10) are discussed below.

Comparison to the NAAQS

Results of each impact analysis are compared with applicable “thresholds of concern,” which 

have typically been used in air quality impact evaluations by other Federal actions, including onshore 

oil and gas leasing programs. The applicable comparison thresholds for criteria pollutant impacts 

are the corresponding NAAQS (Table 4-5).

The CAMx future year scenario predicted that the total concentrations from all emission 

sources were post-processed for comparison to the applicable NAAQS in two different ways. First, 

the CAMx predictions were compared directly against each NAAQS. This is referred to as the 

“absolute” prediction comparison. These absolute prediction comparisons may be misleading in 

cases in which the model exhibits significant prediction bias. In recognition of this, USEPA modeling 

guidance (USEPA, 2007 and 2014) recommends using the model in a relative sense when 

projecting future year ozone, PM2.5, and regional haze levels, and USEPA has developed the 

Modeled Attainment Test Software (MATS; Abt., 2014) for making such future year projections. This 

approach uses the ratio of future year to current year modeling results to develop Relative Response 

Factors (RRFs) that are applied to observed current year Design Values (abbreviated as either DVC 

or DVB) to make future year Design Value (DVF) projections (i.e., DVF = DVC x RRF). The MATS 

was applied to the prediction of both ozone and PM2.5 DVFs. 

Table 4-5. NAAQS and PSD Increments.

Pollutant Pollutant/Averaging 

Time NAAQS PSD Class I Increment1

PSD Class II 

Increment1

CO 1-hour2 35 ppm

40,000 μg/m3 -- --

CO 8-hour2 9 ppm

10,000 μg/m3 -- --

NO2 1-hour3 100 ppb

188 μg/m3 -- --

NO2 Annual4 53 ppb

100 μg/m3 2.5 μg/m3 25 μg/m3

O3 8-hour5 0.070 ppm

137 μg/m3 -- --

PM10 24-hour6 150 μg/m3 8 μg/m3 30 μg/m3

PM10 Annual7 -- 4 μg/m3 17 μg/m3

PM2.5 24-hour8 35 μg/m3 2 μg/m3 9 μg/m3

PM2.5 Annual9 12 μg/m3 1 μg/m3 4 μg/m3
4-40 2018 Gulf of Mexico Supplemental EIS

Pollutant Pollutant/Averaging 

Time NAAQS PSD Class I Increment1

PSD Class II 

Increment1

SO2 1-hour10 75 ppb

196 μg/m3

SO2 3-hour11 0.5 ppm

1,300 μg/m3 25 μg/m3 512 μg/m3

SO2 24-hour -- 5 μg/m3 91 μg/m3

SO2 Annual4 -- 2 μg/m3 20 μg/m3

μg/m3 = microgram per cubic meter; CO = carbon monoxide; NAAQS = National Ambient Air 

Quality Standards; NO2 = nitrogen dioxide; O3 = ozone; PM2.5 = particulate matter less than or 

equal to 2.5 μm; PM10 = particulate matter less than or equal to 10 μm; ppb = parts per billion; 

ppm = parts per million; PSD = Prevention of Significant Deterioration; SO2 = sulphur dioxide.

1 The PSD demonstrations serve information purposes only and do not constitute a regulatory 

PSD increment consumption analysis.

2 No more than one exceedance per calendar year.

3 98th percentile, averaged over 3 years.

4 Annual mean not to be exceeded.

5 Fourth-highest daily maximum 8-hour ozone concentrations in a year, averaged over 3 years, 

NAAQS promulgated December 28, 2015.

6 Not to be exceeded more than once per calendar year on average over 3 years.

7

 3-year average of the arithmetic means over a calendar year.

8 98th percentile, averaged over 3 years.

9 Annual mean, averaged over 3 years, NAAQS promulgated December 14, 2012.

10 99th percentile of daily maximum 1-hour concentrations in a year, averaged over 3 years.

11 No more than one exceedance per calendar year (secondary NAAQS).

Ozone

The ozone NAAQS is defined as an 8-hour averaging time that is expressed as a 3-year 

average of the 4th highest maximum daily average. Since only one calendar year of modeling results 

are available for the base year and future year outcome, the future year 4th highest maximum daily 

average 8-hour ozone concentration is used as a pseudo-NAAQS comparison metric. The USEPA’s 

Model Attainment Test Software (MATs) was used to make future year ozone future design values 

projections using the CAMx 2012 Base Case and Future Year Scenario modeling results.

The impacts to air quality from ozone for of all proposed and existing oil and gas emissions 

from Gulf of Mexico OCS sources and their support vessels/aircraft (Source Group C) are moderate

because the future year design values were above the current year design value (which was already 

above the NAAQS). The modeling suggests that the maximum contribution of all proposed and 

existing oil and gas emissions from Gulf of Mexico OCS sources and their support vessels/aircraft 

(Source Group C) occur in Galveston, Texas (a nonattainment area).

The impacts to air quality from O3 for Source Group B (new platforms and associated 

support vessels and aircraft under this Supplemental EIS) are minor because the future year design 

values were lower than the current year design values. The modeling suggests that the maximum 

contribution of Source Group B is centered in the GOM offshore of Louisiana; maximum impacts 

from the State seaward boundaries inland along the coast of Cameron Parish, Louisiana. Source 
Description of the Affected Environment and Impact Analysis 4-41

Group A (new platforms under this Supplemental EIS) maximum contributions occur in the same 

location, but the support vessel and helicopter activities (from Source Group B) are responsible for 

the greater impacts landward of the State seaward boundary.

NOTE: For the ozone impacts assessment, please note that the States will not designate 

under the 2015 ozone standard of 70 ppb until 2017, with the earliest attainment date of March 2021 

for marginal areas. For this impacts assessment, the non-OCS source emissions were based on the 

USEPA’s 2017 emission projections, with a future modeled year of 2017 and compared with the 

70-ppb standard. This assessment is assuming the standard will be attained in advance of the 

actual attainment date but wanted to give maximum OCS oil and gas impacts under the new 70-ppb 

ozone standard.

Particulate Matter (PM)

PM2.5

There are two PM2.5 NAAQS: one for the 24-hour averaging time that is expressed as a 

3-year average of the annual 98th percentile in a year and an annual average over 3 years. With 

1 year of photochemical grid modeling, the annual 98th percentile would correspond to the 8th highest 

24-hour PM2.5 concentration in a year. As described for the ozone NAAQS analysis, the MATS was 

used to calculate DVFs for the 24-hour and annual PM2.5 NAAQS.

All future year modeled concentrations for 24-hour and annual PM2.5 are below the NAAQS. 

The impacts to air quality from 24-hour PM2.5 and annual PM2.5 are minor because the future year 

design values were lower than the current year design values at all sites except one. While the 

annual PM2.5 current year modeled concentration exceeded the NAAQS in Harris County, Texas, 

the projected future year design value at this location is below the NAAQS.

24-hour PM2.5: All current and future year design values are below the NAAQS, and 

the future year design values are projected to be lower than the current year design 

values at all sites. The modeling suggests that the highest 24-hour PM2.5 impacts 

occur at the State seaward boundary off the coast of Louisiana. There were no 

monitoring sites with the 24-hour PM2.5 in excess of the NAAQS, with future year 

modeling projecting no design value exceedances. The maximum contributions due 

to emissions from all existing and proposed GOM platform and support equipment to 

the 8th highest 24-hour PM2.5 concentrations occurs right on the State seaward 

boundary off the coast of Houma, Louisiana.

Annual Average PM2.5: The modeling suggests that the highest annual PM2.5

impacts occur right at the State seaward boundary off the coast of Louisiana. There 

was one monitoring site with annual PM2.5 design value concentrations above the 

NAAQS (in Harris County (Houston), Texas) but reduced to below the NAAQS in the 

future year. The maximum contribution to annual PM2.5 future design values due to 
4-42 2018 Gulf of Mexico Supplemental EIS

emissions from all existing and proposed GOM platform and support equipment 

occurs at the State seaward boundary off the coast of Louisiana.

PM10

There is only one PM10 NAAQS: one for the 24-hour averaging time that is expressed as a 

3-year average not to be exceeded more than once per calendar year. With 1 year of photochemical 

grid modeling, the annual 98th percentile will correspond to the 8th highest 24-hour PM2.5

concentration in a year. The impacts to air quality from PM10 are minor because, while there are 

concentrations increases in water farther offshore, no overall standards were exceeded.

24-Hour PM10: The OCS oil- and gas-related impacts for the 24-hour PM10 are 

similar to the 24-hour PM2.5 future year modeling, projecting no future design value 

exceedances. The modeled 2nd highest daily average PM10 concentrations can be 

compared with the 24-hour average PM10 NAAQS for the base and future scenarios 

and the base-future differences. The modeling suggests areas of elevated PM10 are 

evident in urban and port areas and in fire zones along the Gulf Coast of Texas and 

Louisiana (impacts of fires on PM10 are also seen). The PM10 decreases between 

the current and future year are modeled along the Louisiana coast, with increases in 

waters farther offshore associated with new emissions from proposed action sources. 

The maximum contribution of all oil and gas platforms and support vessels and 

helicopters (Source Group C) are below the NAAQS, and the maximum contribution 

of the new platforms and associated support vessels and aircraft under this 

Supplemental EIS (Source Group B) are below the NAAQS.

Nitrogen Dioxide (NO2) 

There are two nitrogen dioxide NAAQS: one for the 1-hour averaging time that is expressed 

as a 3-year average of the annual 98th percentile in a year and an annual average over 3 years. 

With 1 year of photochemical grid modeling, the annual 98th percentile would correspond to the 

8th highest 24-hour NO2 concentration in a year. Results are included below for both the 1-hour NO2

and the annual NO2 averaging times. All modeled concentrations for NO2 are below the NAAQS. 

The impacts to air quality from 1-hour NO2 and annual NO2 are minor because overall, 

concentrations decrease between the base and future year scenarios at most locations. While there 

was in increase between the base and future year scenarios for annual NO2 in Vermilion Parish, 

Louisiana, no standards were exceeded.

1-hour NO2: All modeled 1-hour NO2 concentrations are below the NAAQS. The 

overall, concentrations decrease between the base and future year scenarios at most 

locations. The modeling suggests that the maximum contributions from new 

platforms and support vessels and helicopters associated with this Supplemental EIS 

(Source Group B) are dominated by vessel and possibly helicopter traffic in the port 

areas, most notably in Vermilion Parish, Louisiana; and the maximum combined 
Description of the Affected Environment and Impact Analysis 4-43

contributions from new and existing platforms and support vessels and helicopters 

(Source Group C) are dominant in the area of the LOOP.

Annual NO2: These results are similar to those for 1-hour NO2. The maximum 

impacts of new and existing platforms and support vessels and helicopters 

associated with this Supplemental EIS (Source Group C) showed increases between 

the base and future year scenarios to occur near the entrance to the Freshwater 

Bayou Canal in Vermilion Parish, Louisiana, and somewhat larger increases 

modeled in the Permian Basin of west Texas. However, overall no standards were 

exceeded.

Sulfur Dioxide (SO2) 

There are two sulfur dioxide NAAQS: one for a 1-hour averaging time that is expressed as a 

3-year average of the annual 99th percentile in a year and a 3-hour average not to be exceeded 

more than once per year. All modeled concentrations for SO2 are below the NAAQS. The impacts 

to air quality from 1-hour SO2 and 3-hour SO2 are minor because overall, concentrations decrease 

between the base and future year scenarios at most locations as sources retire or apply control 

equipment.

1-hour SO2: All modeled values are below the NAAQS. While maximum 

contributions are located from sources in areas with deepwater platforms, 

concentrations decrease in most locations in the future year scenario as sources are 

retired or apply control equipment with projected maximum impacts all below the 

NAAQS. 

3-hour SO2: All modeled values are below the NAAQS. These results are similar to 

those for the 1-hour SO2 described above.

Carbon Monoxide (CO)

There are two carbon monoxide NAAQS: a 1-hour averaging time and an 8-hour average 

not to be exceeded more than once per year. All modeled concentrations for SO2 are below the 

NAAQS. The impacts to air quality from 1-hour CO2 and 8-hour CO are minor because overall, 

concentrations decrease between the base and future year scenarios at all locations.

1-hour CO: The modeled 1-hour CO design values (based on the annual 2nd highest 

daily maximum 1-hour average) for the base, future, and future-base scenarios show 

all values are below the NAAQS.

8-hour CO: The modeled 8-hour CO design values (based on the annual 2nd highest 

non-overlapping running 8-hour average) for the base, future, and future-base 

scenarios show the maximum predicted 8-hour design value in the future year occurs 
4-44 2018 Gulf of Mexico Supplemental EIS

at the entrance to the Freshwater Bayou Canal in Vermilion Parish, Louisiana, but no 

over standard was exceeded.

Incremental Impacts of PSD Pollutants with Respect to PSD Class I and Class II Increments

As mentioned in the Chapter 4.1.1, the WPA, CPA, and EPA include national parks and 

Federal wilderness areas where air quality and AQRVs (primarily visibility) are protected more 

stringently than under the NAAQS. The Class I areas, compared with Class II areas, have lower 

PSD increments that new sources may not exceed and that are protected against excessive 

increases in several AQRVs, including visibility impairment. Table 4-6 lists those areas that are 

located along the Gulf Coast and, thus, are of greatest interest to this analysis.

The incremental AQ/AQRV contributions associated with emissions from each source group 

listed in Table 4-4 were calculated for the Class I and sensitive Class II areas listed in Table 4-6. 

The selected areas include all Class I and sensitive Class II areas within the 4-km modeling domain 

plus additional Class I areas within the 12-km modeling domain (Bradwell Bay).

The Class I and sensitive Class II increments analyses results are expressed in terms of the 

maximum increment consumption over all Class I and sensitive Class II areas within the 4-km 

modeling domain. Incremental impacts of each Source Group at Class I and sensitive Class II areas 

were calculated for all pollutants for which PSD increments have been set (NO2, SO2, PM10, and 

PM2.5) and are discussed below.

Table 4-6. Class I and Sensitive Class II Areas in Gulf Coast and Nearby States.

Type Name Agency State Modeling Domain

Class I Breton Wilderness FWS LA 4 km

Class II Breton NWR FWS LA 4 km

Class II Gulf Islands NS NPS MS, FL 4 km

Class II Padre Island NS NPS TX 4 km

Class I Bradwell Bay FS FL 12 km

FL = Florida; FS = Forest Service; FWS = Fish and Wildlife Service; LA = Louisiana; 

MS = Mississippi; NPS = National Park Service; NS = National Seashore; 

NWR = National Wildlife Refuge; TX = Texas. 

Comparison at the Class I and Sensitive Class II Areas

The maximum contribution of new oil and gas production sources under this Supplemental

EIS were reported for each Class I and sensitive Class II area and were compared against the PSD 

increments given in Table 4-5. Comparisons of impacts from a proposed action with maximum 

allowed PSD increments are presented here as an evaluation of a “threshold of concern” for 

potentially significant adverse impacts, but they do not represent a regulatory PSD increment 
Description of the Affected Environment and Impact Analysis 4-45

consumption analysis. (Note: This analysis does not constitute a regulatory PSD increment 

consumption analysis as would be required for major sources subject to the New Source Review 

program requirements of the Clean Air Act. Under the Clean Air Act, a PSD increment consumption 

analysis requires major stationary sources subject to PSD review to demonstrate that emission 

increases from the proposed source, in conjunction with all other emissions increases or reductions 

in the impacted area (typically within 50 km [31 mi]), will not cause or contribute to concentrations of 

air pollutants that exceed PSD increments. The PSD increments have been established for NOx, 

SO2, and PM in Class I and sensitive Class II areas. Actions to be authorized by BOEM under this 

Supplemental EIS do not typically constitute major stationary sources and do not typically trigger 

PSD permits or review. However, a comparison of ambient concentrations from an accumulation of 

new oil and gas sources within the entire study area to PSD increments at specific Class I and 

sensitive Class II areas is included in this analysis for information purposes. This information is 

presented to aid State agencies in tracking potential minor source increment consumption and to aid 

Federal Land Managers or Tribal governments responsible for protecting air resources in Class I 

areas).

The CAMx source apportionment results for individual source categories were used to 

evaluate the incremental impacts of each of a set of hierarchical source groups as defined in 

Table 4-6. Note that Source Group B represents all new direct emissions associated with this 

Supplemental EIS, and Source Group C represents these sources in addition to all existing OCS 

platforms and associated support vessel and aircraft activity.

The impacts to Class I areas from contributions of new platforms and its associated support 

vessels and aircraft are minor because proposed activities exceed the 24-hour PM2.5 Class I PSD 

increments by 10 percent at the Breton Wilderness Area, which are a result of support vessels and 

helicopter traffic associated with the activities. The impacts to Class I areas from contributions of all 

activities from past, present, and future lease sales are moderate because proposed activities 

exceed the annual and 24-hour PM2.5, 24-hour PM10, and annual NO2 Class I PSD increments at the 

Breton Wilderness Area. BOEM has been in consultation with FWS and will be conducting further 

refined modeling. It is anticipated that these air quality results will be updated in a Supplemental EIS 

as soon as these data are available.

The impacts to sensitive Class II areas from contributions of all activities as a result of a 

single proposed lease sale are minor because, while maximum increases occur at the Gulf Islands 

National Seashore for all PSD pollutants and averaging times and increases occur for annual NO2 at 

the Breton Wilderness Area, there are no exceedances of the PSD Class II increment. The impacts 

to sensitive Class II areas from contributions of all activities from past, present, and future lease 

sales are moderate because proposed activities exceed the annual 24-hour PM2.5 Class II PSD 

increments at the Gulf Islands National Seashore.
4-46 2018 Gulf of Mexico Supplemental EIS

Class I Areas

For all source groups described in Table 4-7, the maximum contributions for all PSD 

pollutants and averaging times occur at the Breton Wilderness Area Class I area. Concentration 

increments from Source Groups A and B are less than the maximum allowed PSD increments for all 

pollutants and averaging times, except for the 24-hour PM2.5 increment from Source Group B at the 

Breton Wilderness Class I area where the maximum impact exceeds the Class I PSD increment. 

The difference in the maximum Source Group A 24-hour average PM2.5 increment and the maximum 

Source Group B 24-hour average PM2.5 indicates that support vessels or helicopter traffic associated 

with new offshore platforms, rather than emissions from the platforms themselves, are largely 

responsible for pushing the maximum impact above the Class I PSD increment at Breton Wilderness 

Area. However, when the 24-hour PM2.5 impact from Source Group B is averaged over all grid cells 

covering the Breton Wilderness Class I area, the impact is below the Class PSD increment. The 

maximum impacts from Source Group C exceeds the annual and 24-hour PM2.5, 24-hour PM10, and 

annual NO2 Class I PSD increments at the Breton Wilderness Area.. 

Sensitive Class II Areas

For all source groups described in Table 4-7, the maximum contributions occur at the Gulf 

Islands National Seashore for all PSD pollutants and averaging times except annual NO2, which 

occurs at the Breton Wilderness Area. The cumulative impacts (Source Group C) exceed the annual 

24-hour PM2.5 Class II PSD increments at the Gulf Islands National Seashore.

Table 4-7. Source Group for Incremental Impacts Analysis.

Source 

Group

Included Source 

Categories Comment

A SC3 New oil and gas platform sources under this Supplemental

EIS

B SC3, SC4 Add support vessels and aircraft associated with new 

platform sources

C SC3, SC4, SC5 Add oil and gas platforms and associated support vessels 

and aircraft under the No Action Alternative

D SC3, SC4, SC5, 

SC6 Add all other marine vessel activity in the GOM

AQRV Impacts – Including Visibility and Acid Deposition

While visibility and acid deposition are not directly regulated by BOEM, an analysis of the 

potential impacts is provided below.

Results of each impact analysis are compared with applicable “thresholds of concern,” which 

have typically been used in air quality impact evaluations by other Federal actions, including onshore 

oil and gas leasing programs. The applicable comparison thresholds for visibility impacts are based 

on incremental changes in light extinction below the level at which they would be noticeable to the 

average human observer. The applicable comparison thresholds for acid (i.e., sulfur and nitrogen) 

deposition impacts are based on (1) incremental impacts considered sufficiently small as to have no 
Description of the Affected Environment and Impact Analysis 4-47

consequential effect on the receiving ecosystems, i.e., Deposition Analysis Thresholds, and 

(2) critical load levels above which cumulative ecosystem effects are likely to or have been 

observed.

Comparison to Visibility and Acid Deposition

Visibility impacts were calculated for each source group using incremental concentrations as 

quantified by the CAMx PSAT tool. For each source group, the estimated visibility degradation at 

the Class I areas and sensitive Class II areas due to the source group are presented in terms of the 

number of days that exceed a threshold change in deciview relative to background conditions. The 

number of days with a deciview greater than 0.5 and 1.0 are reported.

The preliminary results of impacts of all activities as a result of a single proposed lease sale 

to visibility impairment from a proposed lease sale is expected to be minor to moderate as modeled 

results show exceedances of the visibility thresholds at several of the Class I and sensitive Class II 

areas in the Gulf of Mexico region. The preliminary results of impacts of all activities as a result of all 

contributions of all activities from past, present, and future lease sales to visibility impairment from a 

proposed lease sale is expected to be minor to moderate as modeled results show exceedances of 

the visibility thresholds at several of the Class I and sensitive Class II areas in the Gulf of Mexico 

region.

The preliminary results of impacts of all activities as a result of a single proposed lease sale 

to acid deposition is expected to be minor to moderate as modeled results show incremental 

nitrogen deposition exceeds the western and eastern Deposition Analysis Thresholds at all three 

locations (i.e., the Breton Wilderness Area, Gulf Islands National Seashore, and Padre Island 

National Seashore). Additionally, incremental sulfur deposition is below the Deposition Analysis 

Thresholds in all cases except the sulfur deposition at the Breton Wilderness Area and Gulf Islands 

National Seashore, which exceed the western Deposition Analysis Thresholds but not the eastern 

Deposition Analysis Thresholds.

The preliminary results of impacts of all from contributions of all activities from past, present, 

and future lease sales to acid deposition is expected to be minor to moderate as modeled results 

show cumulative maximum nitrogen deposition to continue exceeding the critical load thresholds 

under the future year scenario for all areas except the Padre Island National Seashore. Additionally, 

cumulative sulfur deposition values are lower, and larger sulfur emission reductions help to reduce 

sulfur deposition from above the critical load to below the critical load at the Breton Wilderness Area 

and Breton National Wildlife Refuge (based on maximum grid cell values). Nevertheless, the 

maximum grid cell sulfur deposition still exceeds the critical load at the Gulf Islands National 

Seashore by a small margin.

Visibility

For visibility impacts, thresholds are based on incremental changes in light extinction below 

the level at which they would be noticeable to the average human observer. Incremental visibility 
4-48 2018 Gulf of Mexico Supplemental EIS

impacts were calculated for each source group, as well as the cumulative impact of all sources 

combined. The changes in light extinction from CAMx model concentration increments due to 

emissions from each source group were calculated for each day at grid cells that intersect Class I 

and sensitive Class II areas within the 12/4-km modeling domain-km (7/2-mi) modeling domain. For 

Source Group A, the annual 8th highest change in deciview exceed the 1.0 threshold at the Breton 

Wilderness Area, Breton National Wildlife Refuge, and Gulf Islands National Seashore. Incremental 

impacts for Source Group B are larger and include days with the 8th highest change in deciview 

greater than 1.0 at the Padre Island National Seashore in addition to the areas mentioned above, as 

well as values greater than 0.5 at the Chassahowitzka Wilderness Area and St. Marks National 

Wildlife Refuge. For Source Group A, the annual 8th highest deciview exceed the 1.0 threshold at 

the Breton Wilderness Area, Breton National Wildlife Refuge, and Gulf Islands National Seashore. 

Incremental impacts for Source Group B are larger and include days with 8th highest deciview 

greater than 1.0 at Padre Island National Seashore in addition to the areas mentioned above as well 

as values greater than 0.5 at Chassahowitzka Wilderness Area and St. Marks National Wildlife 

Refuge.

Acid Deposition

The CAMx-predicted that wet and dry fluxes of sulfur- and nitrogen-containing species were 

processed to estimate total annual sulfur (S) and nitrogen (N) deposition values at each Class I and 

sensitive Class II area. The maximum annual S and N deposition values from any grid cell that 

intersects a Class I receptor area was used to represent deposition for that area, in addition to the 

average annual deposition values of all grid cells that represent a Class I receptor area. Although 

the convention in the past has been to report just the maximum deposition in any receptor in a Class 

I/II area, since deposition relates to the total amount deposited across an entire watershed, the 

average metric may be considered a more relevant parameter for evaluating potential environmental 

effects. Maximum and average predicted S and N deposition impacts are reported separately for 

each source group.

As a screening analysis, incremental deposition values in Class I and II areas for combined 

Source Groups A (new platforms associated with the highest emissions year of the 10 proposed 

lease sales) and B (new platforms and associated support vessels and helicopters associated with 

the 10 proposed lease sales) were compared to the eastern and western U.S. Deposition Analysis 

Thresholds. Comparison of deposition impacts from cumulative sources to the Deposition Analysis 

Thresholds is not appropriate. Deposition results were also obtained for all other sensitive areas 

throughout the 12-km (7-mi) modeling domain, but the highest deposition values all occurred within 

the 4-km (2-mi) domain. The dividing line between the eastern and western Deposition Analysis 

Thresholds specified in the FLAG guidance is the Mississippi River, which makes sense for most 

locations in the U.S.; however, it is not necessarily clear which Deposition Analysis Threshold would 

be most appropriate for coastal locations along the Gulf Coast, so results are compared here against 

both Deposition Analysis Thresholds. 
Description of the Affected Environment and Impact Analysis 4-49

Incremental nitrogen deposition exceeds the western and eastern Deposition Analysis 

Thresholds at all three locations (i.e., the Breton Wilderness Area, Gulf Islands National Seashore, 

and Padre Island National Seashore). Incremental sulfur deposition is below the Deposition 

Analysis Thresholds in all cases except the sulfur deposition from Source Group B at the Breton 

Wilderness Area and Gulf Islands National Seashore, which exceeds the western Deposition 

Analysis Thresholds but not the eastern Deposition Analysis Thresholds.

Cumulative nitrogen deposition from all sources combined for the base case and future year 

scenarios were compared against applicable critical load levels in each Class I and II area for which 

critical loads were identified. Cumulative nitrogen deposition is projected to decrease in all areas 

between the 2012 base case and the 2017 future year, which is consistent with an overall reduction 

in NOx emissions. Nevertheless, maximum nitrogen deposition is modeled to continue exceeding 

the critical load thresholds under the future year scenario for all areas except the Padre Island 

National Seashore. Sulfur deposition values are lower, and larger sulfur emission reductions help to 

reduce sulfur deposition from above the critical load to below the critical load at the Breton 

Wilderness Area and Breton National Wildlife Refuge (based on maximum grid cell values). 

Nevertheless, the maximum grid cell sulfur deposition still exceeds the critical load at the Gulf 

Islands National Seashore by a small margin.

OCS Oil- and Gas-Related Impacts

This section includes all activities (i.e., routine activities projected to occur and accidental 

events that could occur) from past, proposed, and future lease sales. Emissions contributing to air 

quality degradation come from many sources. Air pollutants on the NAAQS list are commonly 

referred to as criteria pollutants because they are ubiquitous. Although these pollutants occur 

naturally, elevated levels are usually the result of anthropogenic activities. The OCS oil- and gasrelated activities that could impact air quality include the following: platform construction and 

emplacement; platform operations; drilling activities; flaring; service-vessel trips; fugitive emissions; 

the release of oil, condensate, natural gas, and chemicals used offshore, or pollutants from the 

burning of these products; and a low-probability catastrophic spill, which is not part of the proposed 

action and not likely expected to occur. Based on the air quality modeling results from the “Air 

Quality Modeling in the Gulf of Mexico Region” study, cumulative impacts would be moderate

because, while there are exceedances to the thresholds of concern, the impacts are just enough to 

push over the standard.

In the air quality modeling study, Source Group C represents all proposed (new) and existing 

oil- and gas-related emissions from Gulf of Mexico OCS sources and their support vessels/aircraft. 

According to the modeling results, the impacts of criteria pollutants from Source Group C to air 

quality are below the NAAQS for all pollutants, except ozone which shows an increase in the future 

year design values occurring in Galveston, Texas, which is a nonattainment area. At the Galveston, 

Texas, monitor, the contribution of Source Group A (new platforms) alone was sufficient to bump the 

future year design value from just below the NAAQS to just above the NAAQS (recall comparisons 

to the 70-ppb NAAQS are made after truncating design values to the nearest ppb).
4-50 2018 Gulf of Mexico Supplemental EIS

According to the modeling results, the incremental impacts of PSD pollutants from Source 

Group C to the Class I area exceed the annual and 24-hour PM2.5, 24-hour PM10, and annual NO2

Class I PSD increments at the Breton Wilderness Area. The incremental impacts of PSD pollutants 

from Source Group C to the sensitive Class II area exceed the annual 24-hour PM2.5 Class II PSD 

increments at the Gulf Islands National Seashore.

Non-OCS Oil- and Gas-Related Impacts

Non-OCS oil- and gas-related impacts include other past, present, and reasonably 

foreseeable future activities occurring within the same geographic range and within the same 

timeframes as a proposed action, but they are not related to the OCS Oil and Gas Program. 

Onshore emission sources from non-OCS oil- and gas-related activities include power generation, 

industrial processing, manufacturing, refineries, commercial and home heating, and motor vehicles 

(Chapter 3.3.2.6). The total impact from the combined onshore and offshore emissions would have 

an effect on the ozone nonattainment areas in southeast Texas and the parishes near Baton Rouge, 

Louisiana.

State oil and gas programs (Chapter 3.3.2.1) onshore, in territorial seas, and in coastal 

waters also generate emissions that affect the air quality of any state. These emissions are 

regulated by State agencies and/or the USEPA. Reductions in emissions have been achieved 

through the use of low sulfur fuels, catalytic reduction, and other efforts and, as a result, constitute 

minor impacts to the air quality of any state.

Other major factors influencing offshore environments, such as sand borrowing (Chapter 

3.3.2.7.6), commercial transportation (Chapter 3.3.2.3), military vessels, and recreational vessels 

also generate emissions that can affect air quality. These emissions are regulated by State 

agencies and/or the USEPA. Reductions have been achieved through the use of low sulfur fuels 

and catalytic reduction and, as a result, constitute slight impacts to onshore air quality.

Hurricanes (Chapter 3.3.2.10.2) mainly cause damage to offshore infrastructures and 

pipelines, which may result in an oil spill. A hurricane would cause minor effects on the onshore air 

quality since air emissions in the event of a hurricane are temporary sources. For the cumulative 

scenario, the emissions from an oil spill and the associated response activities and infrastructure 

repair activities are expected to be the same as a proposed lease sale and to have lesser effects on 

the onshore air quality.

Additionally, recent information shows that intercontinental dust transport may have impacts 

on the GOM’s air quality. For example, dust from Central America and North Africa has been found 

in the Texas atmosphere. Fine particulates (PM2.5), such as ammonium sulfate, can be suspended 

in the atmosphere and can impair visibility and adversely affect human health. Once in the 

atmosphere, these fine particulates can be transported for long distances. It has been observed that 

a substantial amount of the fine particulates observed in Texas comes from Mexico and Central 

America, and enters into the United States across Texas’ southern border. As a result, it reduces 
Description of the Affected Environment and Impact Analysis 4-51

the visibility at Big Bend and Guadalupe Mountains National Parks, both Class I (pristine with 

respect to visibility) areas. The results of air dispersion modeling indicate that as much as half of the

visibility impairment (occurring on 20% of the most visibility impaired days) at Big Bend comes from 

international transport (State of Texas, Commission on Environmental Quality, 2014). The transAtlantic transport of North African dust by summertime trade winds occasionally increases ambient 

particulate matter (PM) concentrations in Texas above air quality standards (Bozlaker et al., 2013). 

These results indicate that an increase in visibility impairment in Texas is likely due to transport of 

dust rather than OCS oil- and gas-related emission sources.

The activities associated with a proposed action would increase global greenhouse gas 

(GHG) emissions from the use of vessels, drilling equipment, and other activities that burn fossil 

fuels. In addition, methane (CH4,) also known as natural gas, is removed from wells and brought 

onto OCS oil- and gas-related facilities along with oil being produced. Sometimes CH4 is released 

as a fugitive gas that can escape unintentionally from leaks in equipment used by operators. As a 

result of exploration, development, and production of oil and gas on the OCS, the activities 

associated with a proposed action are expected to release GHGs and black carbon from the use of 

combustion engines in vessels, construction, drilling, and other equipment, as well as through 

deliberate or accidental release of CH4. In addition to the direct emissions from OCS oil and gas 

operations presented above, BOEM has evaluated GHG emissions covering the lifecycle of OCS oil 

and gas production and consumption. This includes both the “downstream” consumption and 

onshore processing of oil and gas products, as well as the “upstream” emissions from offshore 

exploration, development, and production. This Supplemental EIS tiers from and updates the 

2017-2022 GOM Multisale EIS, which tiers from the Five-Year Program EIS. In the Five-Year 

Program EIS, the potential impacts of the Program’s activities on climate change were assessed in 

Chapter 4.2.1 (Climate Change), which specifically addressed the GOM proposed lease sales in that 

analysis (USDOI, BOEM, 2016b).

Incremental Contribution of a Single Proposed Lease Sale to Overall Cumulative Impacts

In the air quality modeling study, incremental contributions are categorized as the impacts of 

pollutants from new platforms and their associated support vessels and aircraft. The forecasted data 

used to support modeling analyses include emissions resulting from the 10 proposed lease sales 

annualized by using BOEM’s Resource Evaluation’s mid-case scenario. To understand how these 

results would apply to a single proposed lease sale, the level of projected activity was compared 

between the modeled highest year of the 10 proposed lease sales to a single proposed lease sale. 

A regionwide lease sale has not previously been analyzed, and historic trend data are limited. In the 

scenario in Chapter 3.1, the projected activities of a single regionwide lease sale is based on a 

range of historic observations and provides a reasonable expectation of oil and gas production 

anticipated from a single proposed lease sale. The projected activities of 10 proposed regionwide 

lease sales’ mid-case scenario, which was used in the model, falls within the range of a single 

proposed lease sale. This is conservative because the current price of oil equals the low range of 

the scenario. Using these assumptions, the potential impacts of a single proposed lease sale would 

be minor because the affected resource could be avoided with proper mitigation. The modeling 
4-52 2018 Gulf of Mexico Supplemental EIS

results show that ozone exceeds the NAAQS in Galveston, Texas, and 24-hour PM2.5 exceeds the 

Class I PSD increment at the Breton Wilderness Area. The impacts were sufficient to increase the 

future year design value from just below the NAAQS for ozone and over the Class I PSD increment, 

respectively.

In the air quality modeling study, Source Group B represents new platforms and emissions 

and their support vessels and aircraft. According to the modeling results, the impacts of criteria 

pollutants from Source Group B to air quality are below the NAAQS for all pollutants, except for 

ozone. At the Galveston, Texas, monitor, the contribution of Source Group A (new platforms) alone 

was sufficient to bump the future year design value from just below the NAAQS to just above the 

NAAQS.

The impacts to Class I areas from contributions of new platforms and their associated 

support vessels and aircraft show that proposed activities exceed the 24-hour PM2.5 Class I PSD 

increments by 10 percent at the Breton Wilderness Area, which are a result of support vessels and 

helicopter traffic associated with the activities.

The impacts to sensitive Class II areas from contributions of all activities as a result of a 

single proposed lease sale are minor because, while maximum increases occur at the Gulf Islands 

National Seashore for all PSD pollutants and averaging times and increases occur for annual NO2 at 

the Breton Wilderness Area, there are no exceedance of the PSD Class II increment.

4.1.2.4 Incomplete or Unavailable Information

This chapter discusses the incomplete or unavailable information needed to assess the 

impacts from OCS oil- and gas-related activities. Relevant final air modeling study results are 

unavailable at this time. However, BOEM has used preliminary results, which are provided in 

Appendices B-D in its place. These preliminary results were incorporated into the analysis and is 

the best science available. Furthermore, BOEM relied on data gathered from recent Gulf of Mexico 

OCS emission inventories, along with scenarios or estimates of future production. The scenarios 

provide (1) the assumptions for and estimates of future activities, (2) the rationale for the scenario 

assumptions and estimates, and (3) the type, frequency, and quantity of emissions from offshore

sources associated with a proposed lease sale. Finally, emissions as a result of a proposed lease 

sale would be regulated at the postlease stage under air quality plan reviews. Additional monitoring 

measures and air quality dispersion modeling can be requested of the operator if a further analysis is 

needed and mitigation would be required as necessary.

BOEM determined the projected total emissions that would result from the activities on a 

lease based on estimated emissions from various OCS non-platform and OCS platform equipment 

types, such as diesel engines and generators, and the level of offshore activity projected in 

Chapter 3.1. These same emissions estimates were used as inputs for modeling scenarios to 

predict future impacts. The final study results are not available in time for this Supplemental EIS, but 

BOEM expects that they would be included in future EIS documents. To address data gaps and 
Description of the Affected Environment and Impact Analysis 4-53

current impacts, BOEM used the preliminary results, emissions inventory data, available studies, 

postlease plan information, and current proposed lease sale scenario data, as well as previous 

proposed action scenario data, to reach the impact conclusions.

The air quality in the GOM can be affected by the pollution emitted from OCS oil- and gasrelated sources as well as non-OCS oil- and gas-related sources. These pollution sources can also 

emit a wide variety of pollutants. To improve air quality and reduce air pollution, the Clean Air Act 

Amendments set regulatory limits on pollutants that help to ensure basic health and environmental 

protection from air pollution. To assess the amount of pollution being emitted, pollutants have to be 

measured. To determine impacts from these pollutants, emission-related conditions (e.g., rate of 

emission, height, and distance of sources from coastline) and environmental conditions (e.g., wind 

speed and direction, humidity, temperature, and height of the atmospheric surface layer where 

pollutants are transported) are calculated.

Emissions from activities related to prior lease sales are represented by the 2011 GWEI 

database. Emissions from BOEM’s proposed lease sales are estimated from the exploration and 

development scenario and have been included in the emission inventory that will be used in the 

model to determine routine impacts. The “Air Quality Modeling in the Gulf of Mexico Region” study 

includes development of meteorological datasets appropriate for air quality modeling of the study 

area (which includes a proposed lease sale), comprehensive emissions inventory of all sources in 

the GOM region, and air quality modeling for the cumulative impacts and visibility assessment. 

Given that BOEM does not have the final results from the ongoing air quality modeling study yet, for 

this Supplemental EIS, BOEM relied on emissions inventory data, available studies on OCS oil- and 

gas-related activities, postlease exploration and development plan information, and the preliminary 

modeling results to fill data gaps. This approach was adequate because it assessed a combination 

of pollutants from OCS oil- and gas-related activities, non-OCS oil- and gas-related activities, and 

non-oil and gas activities.

4.1.2.5 Alternative A—Regionwide OCS Lease Sale (The Preferred Alternative)

As mentioned in Chapter 3, for a proposed lease sale under Alternative A, BOEM projects 

that no more activity would occur than has resulted in the past from the highest CPA lease sale 

combined with the highest WPA lease sale. The contribution of routine and accidental events of a

proposed lease sale to air quality would result in minor impacts because most impacts on the 

affected resource could be avoided with proper mitigation. The emission sources would not produce 

emissions sufficient to overwhelm the effects of wind and transport in a single area, causing 

deterioration of air quality over the regionwide OCS. The incremental contribution of a single 

regionwide proposed lease sale would likely have a minor impact on coastal areas because most 

impacts on the affected resource could be avoided with proper mitigation. The support vessels and 

aircraft associated with new platforms are a leading contributor to the increased impacts in the area.
4-54 2018 Gulf of Mexico Supplemental EIS

4.1.2.6 Alternative B—Regionwide OCS Proposed Lease Sale Excluding Available Unleased 

Blocks in the WPA Portion of the Proposed Lease Sale Area

Since this Alternative excludes the available unleased blocks in the WPA, it would result in 

activity concentrated in the CPA/EPA. As mentioned in Chapter 3, for a proposed lease sale under 

Alternative A, BOEM projects that no more activity would occur than has resulted in the past from 

the highest CPA lease sale combined with the highest WPA lease sale. Therefore, because most 

activity is forecast to occur in the CPA/EPA, the impacts as a result of Alternative B would be very 

similar to Alternative A. The incremental contribution of a single CPA/EPA proposed lease sale 

would likely have a minor impact on coastal nonattainment areas because most impacts on the 

affected resource could be avoided with proper mitigation.

4.1.2.7 Alternative C—Regionwide OCS Proposed Lease Sale Excluding Available Unleased 

Blocks in the CPA/EPA Portions of the Proposed Lease Sale Area

Since this Alternative excludes the available unleased blocks in the CPA/EPA, it would result 

in activity concentrated in the WPA. As mentioned in Chapter 3, a maximum of 13 percent of the oil 

production and associated activity and 19 percent of the gas production and associated activity 

would occur in the WPA. While the WPA is a smaller area with less projected activity than is 

proposed for the CPA/EPA under Alterative B, the smaller area could decrease impacts to 

communities from production platforms and also increase total emissions due to travel distances for 

marine vessels; the potential impacts would remain minor. The incremental contribution of a single 

WPA proposed lease sale would likely have a minor impact on coastal areas because most impacts 

on the affected resource could be avoided with proper mitigation.

4.1.2.8 Alternative D—Alternative A, B, or C, with the Option to Exclude Available Unleased 

Blocks Subject to the Topographic Features, Live Bottom (Pinnacle Trend), and/or 

Blocks South of Baldwin County, Alabama, Stipulations

Alternative D would have the same analysis and potential impacts as Alternative A, B, or C 

because there are so few unleased blocks subject to the Topographic Features, Live Bottom 

(Pinnacle Trend), and Blocks South of Baldwin County, Alabama, Stipulations. The difference 

between Alternatives A, B, and C with and without any combination of these stipulations is minor for 

air quality. The impacts under Alternative D would not be much different and likely not even 

measurable when compared with the other alternatives.

4.1.2.9 Alternative E—No Action

For Alternative E, the cancellation of a proposed lease sale would result in no new activities 

associated with a proposed lease sale; therefore, the incremental impacts would be none. There 

could, however, be some incremental increase in impacts caused by a compensatory increase in 

imported oil and gas to offset reduced OCS production, but it would likely be negligible. Cumulative 

impacts of current and past activities (i.e., OCS oil- and gas-related and non-OCS oil- and 

gas-related), however, would continue to occur under this alternative. 
Description of the Affected Environment and Impact Analysis 4-55

4.2 WATER QUALITY

Summary

BOEM has reexamined the analysis for water quality presented in the 2017-2022 GOM 

Multisale EIS based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for water quality presented in the 2017-2022 GOM 

Multisale EIS. Further, the analysis and potential impacts detailed in that document still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of water quality, along with the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with a proposed action are 

presented in Chapter 4.2 of the 2017-2022 GOM Multisale EIS. The following information is a 

summary of the resource description and impact analysis incorporated from the 2017-2022 GOM 

Multisale EIS.

Introduction

Water quality is a term used to describe the condition or environmental health of a waterbody 

or resource, reflecting its particular biological, chemical, and physical characteristics and the ability 

of the waterbody to maintain the ecosystems it supports and influences. It is an important measure 

for both ecological and human health. For the purposes of this analysis, the GOM is divided into 

coastal and offshore waters. Coastal waters are defined to include all bays and estuaries from the 

Rio Grande River in Texas to the Florida Bay. Offshore waters are defined to include those waters 

extending from outside the barrier islands to the Exclusive Economic Zone, located within State 

waters and the Federal OCS. The inland extent is defined by the Coastal Zone Management Act. 

Offshore waters are divided into three regions: the continental shelf west of the Mississippi River; 

the continental shelf east of the Mississippi River; and deep water (>1,000 ft; 305 m).

Protective Measures for Water Quality

The USEPA (Regions 4 and 6) regulates all waste streams generated from offshore oil- and 

gas-related activities. Section 403 of the Clean Water Act requires that National Pollutant Discharge 

Elimination System (NPDES) permits be issued for discharges to the territorial seas (baseline to 3 mi 

[5 km]), the contiguous zone, and the ocean in compliance with USEPA’s regulations for preventing 

unreasonable degradation of the receiving waters.

The authority for the NPDES program is given at 40 CFR part 125 subpart M, “Ocean 

Discharge Criteria.” The purpose of the NPDES program is to prevent the unreasonable 

degradation of the marine environment as described in 40 CFR § 125.122. In accordance with 

definitions stated at 40 CFR § 125.121, “unreasonable degradation of the marine environment” 

means (1) significant adverse changes in ecosystem diversity, productivity, and stability of the 

biological community within the area of discharge and surrounding biological communities; (2) threat 

to human health through direct exposure to pollutants or through consumption of exposed aquatic 
4-56 2018 Gulf of Mexico Supplemental EIS

organisms; or (3) loss of aesthetic, recreational, scientific, or economic values, which is 

unreasonable in relation to the benefit derived from the discharge.

Regulated wastes include drilling fluids, drill cuttings, deck drainage, produced water, 

produced sand, well treatment fluids, well completion fluids, well workover fluids, sanitary wastes, 

domestic wastes, and miscellaneous wastes. The bulk of waste materials produced by offshore 

oil- and gas-related activities are produced water (formation water) and drilling muds and cuttings 

(USEPA, 2009b). There are two general NPDES permits that cover the Gulf of Mexico. Permit 

GMG290000, issued by USEPA Region 6, covers the WPA and most of the CPA; and Permit 

GEG460000, issued by USEPA Region 4, covers the EPA and a small part of the CPA. The USEPA 

Regions’ jurisdictional areas are shown in Figure 3-10 of the 2017-2022 GOM Multisale EIS. 

To meet the goal of preventing unreasonable degradation of the marine environment, 

Section B of the NPDES permits specifies effluent limitations and monitoring requirements for 

offshore oil and gas facilities. Discharged regulated wastes may not contain free oil or cause an oil 

sheen on the water surface, and the oil/grease concentration may not exceed 42 milligrams per liter 

(mg/L) daily maximum or 29 mg/L monthly average. Discharge of drilling fluids containing oil 

additive or formation oil is prohibited, except that which adheres to cuttings and certain small volume 

discharges. Barite used in drilling fluids may not contain mercury or cadmium at levels exceeding 

certain concentrations (1.0 mg/kg mercury and 3.0 mg/kg cadmium). Discharged regulated wastes 

must also be characterized using a whole effluent toxicity test, where a population of mysid shrimp 

or inland silverside minnows are exposed to a certain concentration of the waste stream, and 

mortality of the population must not exceed 50 percent. The NPDES permits allow a mixing zone as 

defined at 40 CFR § 125.121 to meet compliance using an approved plume model. The NPDES 

permits require no discharge within 1,000 m (3,281 ft) of an area of biological concern. Region 4 

also requires no discharge within 1,000 m (3,281 ft) of any federally designated dredged material 

ocean disposal site.

Analysis

Coastal water impacts associated with routine activities include increases in turbidity 

resulting from pipeline installation and navigational canal maintenance, discharges of bilge and 

ballast water from support vessels, and runoff from shore-based facilities. Offshore water impacts 

associated with routine activities result from the discharge of drilling muds and cuttings, produced 

water, and residual chemicals used during workovers. 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. 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 activity associated with a proposed lease sale could contribute a small percentage of 

activity in addition to existing and future OCS oil- and gas-related activities. The specific discharges, 
Description of the Affected Environment and Impact Analysis 4-57

drill muds, cuttings and produced water, and accidents resulting in spills would occur in proportion to 

production and, therefore, would add a small increase to the currently anticipated impacts. 

Furthermore, the vessel traffic and related discharges associated with a proposed lease sale are a 

fraction of the current ongoing commercial shipping and military activity in the Gulf of Mexico. The 

impact of discharges, sediment disturbances, and accidental releases are a small percentage of the 

current overall activity and the overall impacts to coastal and offshore waters.

Impacts on water quality from operational discharges related to a proposed lease sale are 

expected to be minimal because of the following: (1) USEPA regulations to prevent unreasonable 

degradation of the marine environment; (2) prohibitions on discharge of some waste types; 

(3) prohibitions on discharge near sensitive biological communities; (4) monitoring requirements and 

toxicity testing; (5) mixing zone and dilution factors; (6) operational discharges are temporary in 

nature; and (7) any effects from elevated turbidity would be short term, localized, and reversible. As 

such, assuming compliance with applicable regulations, the impacts from the discharge of regulated 

wastes from routine operations would require no additional mitigation.

Impact-Level Definitions

For the purpose of the following discussion, the significance of impact-producing factors on 

water quality is discussed below. The criteria for significance reflect consideration of the context and 

intensity of impact (40 CFR § 1508.27) based on four parameters: detectability (i.e., measurable or 

detectable impact); duration (i.e., short term, long term); spatial extent (i.e., localized, extensive); 

and severity (i.e., severe, less than severe). For water quality, the significance criteria have been 

broadly defined as follows:

• Negligible – Impacts are defined as short-term (less than 1 year), localized 

contaminants and turbidity that present little to no detectable impact.

• Minor – Impacts are defined as detectable, short-term, localized, or extensive 

but less than severe; however, detectable contaminant concentrations may 

exceed regulatory levels. Minor impacts may have little to no effect on marine 

life.

• Moderate – Impacts are defined as detectable, short term, extensive, and 

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

or impacts are detectable, long term, extensive, or localized but less than severe. 

Moderate impacts may result in acute or chronic effects to marine life.

• Major – Impacts are defined as detectable, short term or long term, extensive, 

and severe; however, major impacts may result in acute or chronic effects to 

marine life and may potentially cause human health effects.

The OCS oil- and gas-related, impact-producing factors listed in Table 4-8 below help the 

reader quickly identify the level of potential impacts for each of these factors. This table also 
4-58 2018 Gulf of Mexico Supplemental EIS

illustrates the impact-level conclusions for each impact-producing factor reached in this chapter’s 

impact analysis.

Table 4-8. Water Quality Impact-Producing Factors That Are Reasonably Foreseeable. 

Water Quality Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Geological 

Sampling Negligible Negligible Negligible Negligible None

Bottom Area 

Disturbance Negligible Negligible Negligible Negligible None

Operational 

Discharges and 

Wastes

Negligible to Negligible to Negligible to Negligible to None

Moderate Moderate Moderate Moderate

Pipeline 

Installation Negligible Negligible Negligible Negligible None

Decommissioning 

and Removal 

Operations

Negligible Negligible Negligible Negligible None

Accidental Impacts

Drilling Fluid 

Spills Minor Minor Minor Minor None

Chemical and 

Waste Spills Minor Minor Minor Minor None

Oil Spills

 Without 

 Mitigation Moderate Moderate Moderate Moderate None

 With Mitigation Moderate Moderate Moderate Moderate None

Cumulative Impacts

Incremental 

Contribution2 Negligible Negligible Negligible Negligible None

OCS Oil and Gas 

Program3 Negligible

Non-OCS Oil and 

Gas4 Negligible

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.2 of the 2017-2022 GOM Multisale EIS.

2 This impact level is the incremental contribution of a single proposed lease sale to all cumulative 

impacts in the GOM.

3 This impact level is the cumulative impacts of all past, present, and reasonably forseeable OCS oil- and 

gas-related activities in the GOM.

4 This impact level is the cumulative impacts of all past, present, and reasonably foreseeable activities in 

the GOM.

The impacts of OCS Program-related routine operational discharges (Chapter 3.1.5.1 of the 

2017-2022 GOM Multisale EIS and summarized in Table 4-8 of this Suppplemental EIS) on water 

quality are considered negligible (beyond 1,000 m; 3,281 ft) to moderate (within 1,000 m; 3,281 ft) 
Description of the Affected Environment and Impact Analysis 4-59

of the source. The potential impacts from OCS Program-related oil spills on water quality are 

considered moderate, even with the implementation of mitigating measures. This is because 

activities to address oil spills may cause secondary impacts to water quality, such as the introduction 

of additional hydrocarbons into the dissolved phase through the use of dispersants and the sinking 

of hydrocarbon residuals from burning. The impacts from a proposed action are a small addition to 

the cumulative impacts on water quality when compared with inputs from hypoxia, potentially leaking 

shipwrecks, chemical weapon dumpsites, natural oil seeps, and natural turbidity. The incremental 

contribution of the routine activities and accidental events associated with a proposed action to the 

cumulative impacts on water quality is expected to be negligible for any of the action alternatives. 

For Alternative E, the cancellation of a proposed lease sale would result in no new activities 

associated with a proposed lease sale; therefore, the incremental impacts would be none. 

Cumulative impacts of current and past activities (i.e., OCS oil- and gas-related and non-OCS 

oil- and gas-related), however, would continue to occur under this alternative. A full analysis of

water quality can be found in Chapter 4.2 of the 2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

The level of impacts to water quality from a proposed action would be similar for Alternatives 

A, B, C, and D. Under Alternative E, there would be no new activities associated with a proposed 

lease sale; however, activities associated with past lease sales and non-OCS oil- and gas-related 

activities would continue.

Incomplete or Unavailable Information

In preparation for this Supplemental EIS, BOEM has reviewed the latest information 

available relative to the potential impact-producing factors on water quality, which is presented in 

Chapter 3. Much of the information pertaining to water quality impacts from the Deepwater Horizon

oil spill and response has been discussed in previous NEPA documents, and water quality has 

recovered from the Deepwater Horizon oil spill and response. BOEM has identified incomplete or 

unavailable information that may be relevant to reasonably foreseeable impacts on water quality. 

Much of this information relates to non-OCS oil- and gas-related impacts. Specifically, potentially 

polluting shipwrecks and chemical weapon disposal areas may cause potential impacts to water 

quality and the marine environment. There are no publicly available data regarding these potential 

impacts because no agency has been tasked with this responsibility. It is not foreseen that this 

information would be publicly available to include in this NEPA analysis regardless of the costs or 

resources needed. BOEM has used the best available scientific information to date and believes 

that any additional information would not likely change the ranking of impacts and is not essential to 

a reasoned choice among alternatives.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including Google Scholar Alerts) were examined to 

assess recent information regarding water quality that may be pertinent to a proposed action. No 
4-60 2018 Gulf of Mexico Supplemental EIS

new information that would add to the analyses or change the conclusions was discovered since 

publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for water quality presented in the 2017-2022 GOM 

Multisale EIS with the understanding that no new information on water quality has been published 

since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information was 

discovered that would alter the impact conclusion for water quality presented in that document, and 

the analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still apply for the 

remaining proposed GOM lease sales in the Five-Year Program.

4.3 COASTAL HABITATS

4.3.1 Estuarine Systems (Wetlands and Seagrass/Submerged Vegetation)

Summary

BOEM has reexamined the analysis for estuarine systems presented in the 2017-2022 GOM

Multisale EIS based on the information presented below. No new information was discovered that 

would alter the impact conclusion for estuarine systems presented in the 2017-2022 GOM Multisale 

EIS. Further, the analysis and potential impacts detailed in that document still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of estuarine systems, along with the full analyses of the potential 

impacts of routine activities, accidental events, and cumulative impacts associated with the proposed 

action are presented in Chapter 4.3.1 of the 2017-2022 GOM Multisale EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the 

2017-2022 GOM Multisale EIS.

Introduction

The estuarine system is the transition zone between freshwater and marine environments. It 

can consist of many habitats, including wetlands and submerged vegetation. While some seagrass 

species can be found farther offshore, the majority is within the coastal area of the GOM and will be 

covered in this chapter. The approach of the analysis is to focus on the potential impact-producing 

factors from routine OCS oil- and gas-related activities (i.e., exploration, development, and 

production), as well as accidental events and cumulative impacts impacts. The impact-level 

definitions and the analyses supporting these conclusions are discussed below.

Analysis

In this chapter, BOEM reviewed and analyzed routine OCS oil- and gas-related activities and 

reasonably foreseeable accidental events. Routine activities associated with a proposed lease sale 

that take place on the OCS, where wells are drilled and platforms and pipelines are installed, would 

not impact the wetlands or submerged vegetation that is located miles away. Other routine activities 
Description of the Affected Environment and Impact Analysis 4-61

that support offshore oil and gas exploration, such as increased vessel traffic (Chapter 3.1.2.5), 

maintenance dredging of navigation canals (Chapter 3.1.3.3.4 of the 2017-2022 GOM Multisale 

EIS), pipeline installation (Chapter 3.1.2.2), disposal of OCS oil- and gas-related wastes (Chapter 

3.1.5.1 of the 2017-2022 GOM Multisale EIS), and construction and maintenance of support 

infrastructure in the coastal areas (Chapter 3.1.2.2), could potentially impact wetlands. Of these 

impact-producing factors, vessel traffic was not analyzed with respect to seagrass and submerged 

vegetation because OCS vessels (due to their size and use of commercial ports) are generally not in 

areas shallow enough to have large submerged vegetation beds. An analysis of the potential 

impacts from accidental events, primarily oil spills, associated with a proposed lease sale is 

summarized in this chapter, as is the incremental contribution of a proposed action to the cumulative 

impacts to wetlands and submerged vegetation. Cumulative impacts were analyzed for OCS 

oil- and gas-related activities and for other sources that could affect wetlands and submerged 

vegetation communities (i.e., human impacts, storms, and vessel traffic). Additional factors that 

could affect estuarine systems include subsidence and sea-level rise.

Impact-Level Definitions

For this analysis, the following definitions were used to categorize impacts to wetlands and 

submerged vegetation:

• Negligible – Little to no measurable impacts in the surrounding habitat (i.e., 

wetland segment and seagrass bed).

• Minor – Noticeable but short-term and localized impacts.

• Moderate – Damage to coastal habitats that is noticeable, spatially extensive, 

and long term or permanent.

• Major – Widespread, permanent loss of habitat; changes in species composition 

and abundance and/or altered ecological function well beyond that of normal 

variability. Changes would likely be both long lasting and spatially extensive for 

such an effect.

The potential magnitude for each of these impact-producing factors is provided in Table 4-9

to help the reader quickly identify the level of potential impacts for each of these factors.
4-62 2018 Gulf of Mexico Supplemental EIS

Table 4-9. Estuarine Systems Impact-Producing Factors That Are Reasonably Foreseeable.

Estuarine Systems Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Pipeline Construction 

and Maintenance Negligible Negligible Negligible Negligible None

Navigation Channel 

Maintenance Dredging

Negligible to Negligible to Negligible to Negligible to None

Minor Minor Minor Minor

Vessel Operation 

(support use of 

navigation channels)

Moderate Moderate Minor Moderate None

Construction and Use 

of Coastal Support 

Infrastructure

Negligible Negligible Negligible Negligible None

Accidental Impacts

Oil Spills Minor Minor Minor Minor None

Disposal of OCS Oiland Gas-Related 

Wastes

Negligible Negligible Negligible Negligible None

Cumulative Impacts

Incremental 

Contribution2 Moderate Moderate Minor Moderate None

OCS Oil and Gas3 Major

Non-OCS Oil and Gas4 Major

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.3.1 of the 2017-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as the proposed action, but they are not 

related to the OCS Oil and Gas Program.

The impacts to estuarine systems from routine activities associated with a proposed action 

are expected to be minor to moderate. Minor impacts would be due to the projected low probability 

for any new pipeline landfalls (0-1 projected), the minimal contribution to the need for maintenance 

dredging, the mitigating measures expected to be used to further reduce or avoid these impacts 

(e.g., the use of modern techniques such as directional drilling). However, impacts caused by vessel 

operations related to a proposed action over 50 years would be moderate considering the 

permanent loss of hundreds of acres of wetlands. Overall, impacts to estuarine habitats from oil 

spills associated with activities related to a proposed action would be expected to be minor because 

of the distance of most postlease activities from the coast, the expected weathering of spilled oil over 

that distance, the projected low probability of large spills near the coast, the resiliency of wetland 

vegetation, and the available cleanup techniques.
Description of the Affected Environment and Impact Analysis 4-63

Cumulative impacts to estuarine habitats are caused by a variety of factors, including the 

OCS oil- and gas-related and non-OCS oil- and gas-related activities outlined in Chapter 4.3 of the 

2017-2022 GOM Multisale EIS and human and natural impacts. Development pressures in the 

coastal regions of the GOM have been largely the result of tourism and residential beach-side 

development, and this trend is expected to continue. Storms will continue to impact the coastal 

habitats and have differing impacts. The incremental contribution of a proposed action to the 

cumulative impacts on estuarine habitats is expected to be minor to moderate depending on the 

selected alternative. Under Alternative E, the cancellation of a proposed lease sale would result in 

no new activities associated with a proposed lease sale. There could, however, be some 

incremental increase in impacts caused by a compensatory increase in imported oil and gas to offset 

reduced OCS production, but it would likely be negligible. Cumulative impacts of current and past 

activities (i.e., OCS oil- and gas-related and non-OCS oil- and gas-related), however, would continue 

to occur under this alternative. A full analysis of estuarine habitats can be found in Chapter 4.3 of 

the 2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

The impacts to estuarine systems from routine activities and accidental events associated 

with a proposed action are expected to be minor to moderate, depending on the alternative. The 

impacts of a proposed action on coastal wetlands under Alternative A is expected to be moderate. 

The impacts of Alternative B would be similar to those of Alternative A, except that there would be 

negligible impacts to coastal wetlands and submerged vegetation in Texas because no new OCS 

oil- and gas-related activity is forecasted in the WPA along the Texas coast with this alternative. For 

this reason, the incremental contribution of Alternative B to the cumulative impacts on coastal 

wetlands is expected to be moderate. The impacts of Alternative C would be less than those of 

Alternative A, as only a fraction of the resulting activity forecast for Alternative A is projected under 

Alternative C. For this alternative, there would be negligible impacts to coastal wetlands and 

submerged vegetation in Louisiana; negligible impacts to Mississippi, Alabama, and the panhandle 

of western Florida; and incrementally more impacts to the wetlands and submerged vegetation of 

Texas, compared with Alternative A. Therefore, because the significance of impact-producing 

factors on estuarine habitats would be less for Alternative C than for Alternative A, the incremental 

contribution of Alternative C to the cumulative impacts on coastal wetlands is expected to be minor. 

The impacts of Alternative D would be nearly identical to those of Alternative A because the 

available unleased blocks with topographic features do not contain wetlands or submerged 

vegetation and are too distant (over 25 km; 16 mi) from the coast to have indirect impacts either. If a 

proposed action does not occur (Alternative E), there would be no additional impacts to estuarine 

habitats; however, cumulative impacts from all sources, including OCS oil- and gas-related and 

non-OCS oil- and gas-related sources, would be the same as the cumulative for Alternative A, or 

major. This major impact is due to cumulative OCS oil- and-gas-related spills resulting from all past 

and present leasing activities, including the millions of barrels that entered the Gulf of Mexico from 

the Deepwater Horizon oil spill. There could be some incremental increase in impacts caused by a 

compensatory increase in imported oil and gas to offset reduced OCS production, but it would likely 

be negligible. 
4-64 2018 Gulf of Mexico Supplemental EIS

Incomplete or Unavailable Information

BOEM has identified incomplete or unavailable information regarding estuarine habitat. 

There is incomplete information about impacts resulting from routine activities, as the scenario 

forecast is only an estimate and many global factors can affect OCS oil- and gas-related activity. 

There also remains unavailable information about the future rates of oil spills, as well as spill 

locations and volumes of oil.

There are unknowns regarding the future restoration efforts that are being planned, such as 

what projects would ultimately be constructed and how successful they may be. In addition, the 

future rates of relative sea-level rise are not known with certainty, and thus, resulting impacts to 

wetlands are unknown. Future rates of coastal development are unknown, as is the extent of 

impacts to estuarine systems thereof.

BOEM acknowledges that there remains incomplete or unavailable information that may be 

relevant to reasonably foreseeable significant impacts on estuarine systems. This incomplete or 

unavailable information includes potential data on the Deepwater Horizon, explosion, oil spill, and 

response that may be forthcoming. As there is substantial information available since the 

Deepwater Horizon explosion, oil spill, and response, which is included in the 2017-2022 GOM 

Multisale EIS, BOEM believes that the incomplete or unavailable information regarding the effects of 

the Deepwater Horizon explosion, oil spill, and response on estuarine systems would likely not be 

essential to a reasoned choice among alternatives. Regardless of the costs involved, it is not within 

BOEM’s ability to obtain this information from the NRDA process within the timeline contemplated in 

the NEPA analysis for this Supplemental EIS. BOEM’s subject-matter experts have used what 

scientifically credible information is available in their analyses and applied it using accepted scientific 

methodology.

Many studies have been produced that demonstrate the effects of exposure of wetland 

plants to crude oil, covering a wide range of exposure intensity, longevity, and oil characteristics. 

Much has been learned about the different survival and recovery rates of various plant species. In 

addition, studies have been produced regarding the long-term impacts of canal dredging and 

pipeline installation on wetlands. A proposed lease sale would result in a relatively minor addition to 

existing routine activities and accidental events, and therefore, the incremental contribution to 

wetland impacts from a proposed lease sale would be minor to moderate (depending on the 

alternative), given what is currently known.

The potential for impacts from changes to the affected environment (post-Deepwater 

Horizon) and cumulative impacts remains whether or not the No Action or an action alternative is 

chosen, and therefore, the incremental contribution from a proposed action would be minor relative 

to cumulative impacts. BOEM used reasonably accepted scientific methodologies to extrapolate 

from existing information in completing this analysis and formulating the conclusions presented here.
Description of the Affected Environment and Impact Analysis 4-65

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including the U.S. Department of the Interior, 

Geological Survey; National Wetlands Research Center; Gulf of Mexico Alliance; NOAA; Journal of 

Marine Science and Engineering; Marine Pollution Bulletin; and scientific publication databases 

including Science Direct, Elsevier, and JSTOR) were examined to assess recent information 

regarding estuarine systems that may be pertinent to a proposed action. No new information that 

would add to the analyses or change the conclusions was discovered since publication of the 

2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for estuarine systems presented in the 2017-2022 GOM 

Multisale EIS with the understanding that no new information on estuarine systems has been 

published since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information 

was discovered that would alter the impact conclusion for estuarine systems presented in that 

document, and the analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still 

apply for the remaining proposed GOM lease sales in the Five-Year Program. 

4.3.2 Coastal Barrier Beaches and Associated Dunes

Summary

BOEM has reexamined the analysis for coastal barrier beaches and associated dunes 

presented in the 2017-2022 GOM Multisale EIS based on the information presented below. No new 

information was discovered that would alter the impact conclusion for coastal barrier beaches and 

associated dunes presented in the 2017-2022 GOM Multisale EIS. Further, the analysis and 

potential impacts detailed in that document still apply for the remaining proposed GOM lease sales

in the Five-Year Program. 

A detailed description of coastal barrier beaches and associated dunes, along with the full 

analyses of the potential impacts of routine activities, accidental events, and cumulative impacts 

associated with a proposed action, are presented in Chapter 4.3.2 of the 2017-2022 GOM Multisale 

EIS. The following information is a summary of the resource description and impact analysis 

incorporated from the 2017-2022 GOM Multisale EIS.

Introduction

The coastal barrier beaches and associated dunes are those beaches and dunes that line 

the coast of the northern GOM, including both barrier islands and beaches on the mainland. Barrier 

beaches and associated dune habitats from Texas to the Florida panhandle may be impacted by 

activities resulting from a proposed action. These areas are comprised of the following geologic 

subareas:
4-66 2018 Gulf of Mexico Supplemental EIS

• the barrier island complex of southern Texas;

• the Chenier Plain of eastern Texas and western Louisiana;

• the Mississippi River Delta complex of southeastern Louisiana;

• the barrier-island and Pleistocene Plain complex of Mississippi and Alabama; 

and

• the Florida panhandle.

Barrier islands make up more than two-thirds of the northern GOM shore (Morton et al., 

2004). These shorelines are usually sandy beaches that can be divided into several interrelated 

environments. Generally, beaches consist of a shoreface, foreshore, and backshore. The 

shoreface slopes downward and seaward from the low-tidal water line, under the water. The 

nonvegetated foreshore slopes up from the water to the beach berm-crest. The backshore is found 

between the beach berm-crest and the dunes, and may be sparsely vegetated. The dune zone of a 

barrier landform can consist of a single low dune ridge, several parallel dune ridges, or a number of 

curving dune lines that may be stabilized by vegetation. These elongated, narrow landforms are 

composed of wind-blown sand and other unconsolidated, predominantly coarse sediments.

Analysis

In this chapter, BOEM reviewed and analyzed OCS oil- and gas-related routine activities and 

reasonably foreseeable accidental events. The approach of the analysis is to focus on the potential 

impact-producing factors from OCS oil- and gas-related routine activities (i.e., exploration, 

development, and production), as well as accidental events and cumulative impacts (Table 4-10). 

The impact-level definitions and the analyses supporting these conclusions are discussed below. 

Routine activities associated with a proposed action that take place on the OCS, where wells are 

drilled and platforms and pipelines are installed, would not impact the coastal barrier beaches, which 

are located from 3 to greater than 200 nmi (3.5 to 230.2 mi; 5.6 to 370.4 km) away. Other routine 

activities that support offshore oil and gas exploration, such as increased vessel traffic, maintenance 

dredging of navigation canals, pipeline installation, and construction of support infrastructure in the 

coastal areas, could potentially impact beaches and dunes. An analysis of the potential impacts 

from accidental events, primarily oil spills but also trash and debris, associated with a proposed 

action is summarized in this chapter, as is the incremental contribution of a proposed action to the 

cumulative impacts to beaches and dunes. Cumulative Impacts were analyzed for OCS oil- and 

gas-related activities and for other sources that could affect coastal barrier beaches and dunes (i.e., 

human impacts, storms, vessel traffic, subsidence, and sea-level rise).

Impact-Level Definitions

For this analysis, the following definitions were used to categorize impacts to coastal 

beaches and dunes:
Description of the Affected Environment and Impact Analysis 4-67

• Negligible – Little to no measurable impacts in species composition and 

abundance and/or altering of beach profile or ecological function.

• Minor – Measureable but short-term and localized impacts to species 

composition and abundance and/or altering of beach profile or ecological 

function.

• Moderate – Damage to coastal habitats (impacts to species composition and 

abundance and/or altering of beach profile or ecological function) that is 

detectable, spatially extensive, but temporary and not severe. Can also be used 

to describe localized land loss.

• Major – Severe, bringing about detectable changes in species composition and 

abundance and/or altering of beach profile or ecological function well beyond that 

of normal variability. Changes would likely need to be both long lasting and 

spatially extensive to have such an effect.

The potential magnitude for each of these impact-produring factors is provided in Table 4-10

to help the reader quickly identify the level of potential impacts for each of these factors.

Table 4-10. Coastal Barrier Beaches and Associated Dunes Impact-Producing Factors.

Coastal Barrier 

Beaches and 

Associated Dunes

Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Pipeline Construction 

and Maintenance Negligible Negligible Negligible Negligible None

Navigation Channel 

Maintenance Dredging Minor Minor Minor Minor None

Vessel Operation 

(Support Use of 

Navigation Channels)

Negligible Negligible Negligible Negligible None

Construction and Use 

of Coastal Support 

Infrastructure

Negligible Negligible Negligible Negligible None

Accidental Impacts

Oil Spills Minor Minor Minor Minor None

Disposal of OCS 

Oil- and Gas-Related 

Wastes

Negligible Negligible Negligible Negligible None

Cumulative Impacts

Incremental 

Contribution2 Minor Minor Minor Minor None

OCS Oil and Gas3 Major

Non-OCS Oil and Gas4 Major
4-68 2018 Gulf of Mexico Supplemental EIS

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.3.2 of the 2017-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

The impacts to coastal barrier beaches and dunes from routine activities associated with a 

proposed action are expected to be minor due to the minimal number of projected onshore 

pipelines, the minimal contribution to vessel traffic and to the need for maintenance dredging, and 

the mitigating measures that would be used to further reduce or avoid these impacts. The greater 

threat from an oil spill to coastal beaches is from a coastal spill as a result of a nearshore vessel 

accident or pipeline rupture, and cleanup activities. Overall, impacts to coastal barrier beaches and 

dunes from oil spills associated with OCS oil- and gas-related activities related to a proposed action 

would be expected to be minor because of the distance of most of the resulting activities from the 

coast, expected weathering of spilled oil, projected low probability of large spills near the coast, and 

available cleanup techniques.

Cumulative impacts to coastal barrier beaches and dunes are caused by a variety of factors, 

including the OCS oil- and gas-related and non-OCS oil- and gas-related activities outlined in 

Chapter 4.3.2 of the 2017-2022 GOM Multisale EIS and other human and natural impacts. 

Cumulative OCS oil- and-gas-related spills resulting from all past and present leasing activities, 

including the millions of barrels that entered the Gulf of Mexico from the Deepwater Horizon oil spill, 

are estimated to have had a major impact on coastal barrier beaches and dunes. However, the 

incremental increase in impacts from reasonably foreseeable oil spills related to a proposed action is 

expected to be minor. The incremental contribution of a proposed action to the cumulative impacts 

on coastal barrier beaches and dunes is expected to be minor. Non-OCS oil- and gas-related 

activities, such as development pressures in the coastal regions of the GOM, have been largely the 

result of tourism and residential beach-side development, and this trend is expected to continue. 

Efforts to stabilize the GOM shoreline through the construction of manmade structures can deprive 

natural restoration of barrier beaches through sediment nourishment and sediment transport, which 

have adversely impacted coastal beach landscapes. Storms will continue to impact the coastal 

habitats and have differing impacts. Under Alternative E, the cancellation of a proposed lease sale, 

the resulting additional impacts to coastal barrier beaches and dunes would be negligible; however, 

cumulative impacts from all sources, including OCS oil- and gas-related and non-OCS oil- and 

gas-related sources, would remain. Cumulative impacts of current and past activities (i.e., OCS

oil- and gas-related and non-OCS oil- and gas-related), however, would continue to occur under this 

alternative. A full analysis of coastal barrier beaches and associated dunes can be found in 

Chapter 4.3.2 of the 2017-2022 GOM Multisale EIS. 
Description of the Affected Environment and Impact Analysis 4-69

Comparison of Alternatives

Impacts from most routine activities and accidental events related to a proposed action under 

Alternative A would be expected to be minor since most routine activities are located far from 

coastal beaches. The impacts of Alternative B would be similar to those of Alternative A, except that 

there would be negligible impacts to coastal barrier beaches and dunes in Texas because no OCS 

oil- and gas-related activity is forecast in the WPA along the Texas coast with this alternative. The 

impacts of Alternbative C would be less than those under Alternative A, as only a fraction of the 

resulting activity forecasted for Alternative A is projected for Alternative C. For this alternative, there 

would be negligible incremental impacts to coastal barrier beaches and dunes in Louisiana; and 

zero to negligible impacts to Mississippi, Alabama, and the panhandle of western Florida; and 

incrementally more impacts to the beaches and dunes of Texas. However, Alternative C would have 

less potential for impact than Alternative A or B as the level of projected OCS oil- and gas-related 

activities and impact-producing factors are much less in the WPA. The impacts of Alternative D 

would be nearly identical to those of the alternative it is combined with because the available 

unleased blocks with topographic features do not contain coastal barrier beaches and dunes and are 

too distant (over 25 km; 16 mi) from the coast to have indirect impacts. The incremental contribution 

of Atlernatives A-D to the cumulative impacts to coastal barrier beaches and associated dunes is 

expected to be minor. If a proposed lease sale does not occur (Alternative E), there would be no 

additional impacts to barrier beaches and associated dunes as a result of a proposed lease sale; 

however, cumulative impacts of current and past activities, however, would continue to occur under 

this alternative. There could be some incremental increase in impacts caused by a compensatory 

increase in imported oil and gas to offset reduced OCS production, but it would likely be negligible. 

Incomplete or Unavailable Information

BOEM acknowledges that there remains incomplete or unavailable information regarding 

coastal barrier beaches and associated dunes in the GOM. There is incomplete information about 

routine impacts, as the scenario forecast is only an estimate and many global factors can affect OCS 

oil- and gas-related activity. There also remains unavailable information about future rates of oil 

spills, as well as the locations and volumes of oil. Future rates of coastal development are unknown, 

as is the extent of such impacts to coastal barrier beaches. There are also unknowns regarding the 

future restoration efforts being planned, such as what specific projects would ultimately be 

constructed and how successful they may be. In addition, the future rates of relative sea-level rise 

are not known with certainty (Hausfather, 2013); thus, the resulting impacts to coastal barrier 

beaches and associated dunes are unknown.

A large body of information regarding impacts of the Deepwater Horizon explosion, oil spill, 

and response upon coastal barrier beaches and associated dunes has been developed and 

continues to be developed through the NRDA process, but information remains incomplete. As 

there is substantial information available since the Deepwater Horizon explosion, oil spill, and 

response, which has been analyzed for the 2017-2022 GOM Multisale EIS, BOEM believes that the 

incomplete or unavailable information regarding the effects of the Deepwater Horizon explosion, oil 

spill, and response on coastal barrier beaches and dunes would likely not be essential to a reasoned 
4-70 2018 Gulf of Mexico Supplemental EIS

choice among alternatives. The incomplete information would not be available within the timeframe 

contemplated by the NEPA analysis of this Supplemental EIS. However, much is known about the 

extent of the oiling of beaches and the continuing degradation of the remaining oil.

BOEM has determined that the information is not essential to a reasoned choice among 

alternatives. BOEM’s subject-matter experts have used what scientifically credible information is 

available in their analyses and applied it using accepted scientific methodology. Many studies have 

been produced that demonstrate the effects of exposure of beaches to crude oil, covering a wide 

range of exposure intensity, longevity, and oil characteristics. Much has been learned about the 

effect of oil-spill cleanup on beaches and the degradation rates of oil over time. In addition, studies 

have been produced regarding the long-term impacts of navigation canal dredging on beaches and 

barrier islands. A proposed lease sale would result in a relatively minor addition to existing routine 

activities and accidental events, and therefore, the incremental increase in impacts to coastal barrier 

beaches and dunes from a proposed lease sale would be minor given what is currently known. The 

potential for impacts from changes to the affected environment (post-Deepwater Horizon) and 

cumulative impacts remains whether or not the No Action or an action alternative is chosen.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including the U.S. Department of the Interior, 

Geological Survey; National Wetlands Research Center; Gulf of Mexico Alliance; NOAA;, Louisiana 

State University; and scientific publication databases including Science Direct, Elsevier, and JSTOR) 

were examined to assess recent information regarding coastal barrier beaches and associated 

dunes that may be pertinent to a proposed action. No new information that would add to the 

analyses or change the conclusions was discovered since publication of the 2017-2022 GOM 

Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for coastal barrier beaches and associated dunes 

presented in the 2017-2022 GOM Multisale EIS, with the understanding that no new information on 

coastal barrier beaches and associated dunes has been published since the publication of the 

2017-2022 GOM Multisale EIS. Therefore, no new information was discovered that would alter the 

impact conclusion for coastal barrier beaches and associated dunes presented in that document, 

and the analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still apply for 

the remaining proposed GOM lease sales in the Five-Year Program. 

4.4 DEEPWATER BENTHIC COMMUNITIES

Summary

BOEM has reexamined the analysis for deepwater benthic communities presented in the 

2017-2022 GOM Multisale EIS based on the additional information presented below. No new 

information was discovered that would alter the impact conclusion for deepwater benthic 

communities presented in the 2017-2022 GOM Multisale EIS. Further, the analysis and potential 
Description of the Affected Environment and Impact Analysis 4-71

impacts detailed in that document still apply for the remaining proposed GOM lease sales in the 

Five-Year Program. 

A detailed description of deepwater benthic communities, along with the full analyses of the 

potential impacts of routine activities, accidental events, and cumulative impacts associated with a 

proposed action are presented in Chapter 4.4 of the 2017-2022 GOM Multisale EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the 

2017-2022 GOM Multisale EIS.

Introduction

BOEM defines “deepwater benthic communities” as including both chemosynthetic 

communities (chemosynthetic organisms plus seep-associated fauna) and deepwater coral 

communities (deepwater coral plus associated fauna). These communities are typically found in 

water depths of 984 ft (300 m) or deeper throughout the GOM, although deepwater benthic habitats 

are relatively rare compared with ubiquitous soft bottoms.

Chemosynthetic communities are based on the presence of various organisms that do not 

depend on photosynthetic processes for metabolism. In the GOM, they are formed around natural 

hydrocarbon seepages. Most GOM deepwater corals require exposed hard substrate for attachment 

and growth. They often co-occur on authigenic substrates (substrates that have been generated 

where they are found) created by chemosynthetic processes; however, deepwater coral also 

routinely colonize other natural or artificial hard substrates not associated with hydrocarbon 

seepage.

Protective Measures for Deepwater Benthic Communities

Protective measures have been developed over time based on the nature and sensitivity of 

various benthic habitats and their associated communities, as understood from decades of 

BOEM-funded and other environmental studies. NTL 2009-G40, “Deepwater Benthic Communities,” 

provides operators with relevant information and consolidates guidance for the avoidance and 

protection of the various types of potentially suitable habitat for chemosynthetic organisms and 

deepwater coral. As detailed in NTL 2009-G40, all plans submitted for permitted deepwater (300 m 

[984 ft] or greater) activities are reviewed for the presence of deepwater benthic communities that 

may be impacted by the proposed activity. Lessees must provide site-specific survey and narrative 

information regarding sensitive benthic features with each exploration plan, development operations 

coordination document, and development and production plan. These plans are reviewed by 

subject-matter experts on a case-by-case basis to determine whether a proposed operation could 

impact a benthic community. If an impact from drilling or other seafloor disturbance (e.g., anchors, 

anchor chains, rig emplacement, pipeline emplacement) is judged likely based on site-specific 

information derived from the geohazard survey data, BOEM’s databases and studies, other 

published research, or another creditable source, the operator would be required to relocate the 

proposed operation (i.e., distancing) or undertake other appropriate mitigations to prevent such an 

impact. As detailed above, BOEM’s subject-matter experts make use of the best available datasets 
4-72 2018 Gulf of Mexico Supplemental EIS

to identify probable habitat that could support deepwater chemosynthetic and coral communities, 

including BOEM’s publicly available database of water-bottom anomalies (USDOI, BOEM, 2015). 

This analysis assumes continuation of the protective measures outlined in NTL 2009-G40.

Analysis

This chapter presents an analysis of the potential impacts on deepwater benthic 

communities as a result of routine activities and accidental events associated with a proposed action 

and a proposed action’s incremental contribution to cumulative impacts. The analysis is not 

exhaustive of all possible impacts of routine activities and accidental events; rather, it focuses on 

those most relevant for decisionmakers. Potential impacts from a catastrophic oil spill, including 

long-term impacts and recovery, are detailed in the Catastrophic Spill Event Analysis white paper 

(USDOI, BOEM, 2017b).

Because of the similarity and overlap of the effects of many activities that occur in the OCS, 

the primary, reasonably foreseeable routine and accidental impact-producing factors for deepwater 

benthic habitats can be grouped into three main categories:

(1) bottom-disturbing activities (Chapter 3.1.3.3.2 of the 2017-2022 GOM Mulitsale 

EIS; routine and accidental);

(2) drilling-related sediment and waste discharges (Chapter 3.1.5.1 of the 

2017-2022 GOM Multisale EIS; routine and accidental); and 

(3) oil spills (Chapter 3.2.2; accidental).

Cumulative impacts were also considered in two steps: impacts resulting from OCS oil- and 

gas-related activities (same as routine activities and accidental events); and impacts resulting from 

non-OCS oil- and gas-related sources, namely fishing and climate change.

Some impact-producing factors relevant to deepwater benthic communities are already 

analyzed in greater detail in other chapters. Refer to Chapter 4.7 (“Fishes and Invertebrate 

Resources”) for additional analyses. Several additional impact-producing factors described in 

Chapter 3 were evaluated for potential impacts on deepwater benthic communities. These impactproducing factors were not carried forward for full analysis because any potential effects were 

judged to be either not reasonably foreseeable or having such a miniscule impact that they would 

not rise to even the level of negligible impact. Refer to Chapter 4.4 of the 2017-2022 GOM Multisale 

EIS for discussion on the impact-producing factors not carried forward for full analysis.

The impact significance criteria and resulting conclusions presented in Table 4-11 focus on 

the overall functioning, resilience, and ecosystem level importance of deepwater benthic 

communities throughout U.S. waters of the GOM. The potential magnitude of impact for each of 

these impact-producing factors that are reasonably foreseeable is provided in Table 4-11 to help the 

reader quickly identify the level of potential impacts for each impact-producing factor, shown in the 
Description of the Affected Environment and Impact Analysis 4-73

table both with and without the anticipated BOEM mitigations to make clear the considerable 

difference that results from these mitigations. The impact-level definitions and the analyses 

supporting these conclusions are discussed below. Postlease, site-specific analyses would focus 

more on potential localized impacts of individual development activities (e.g., proposed drilling of a 

well) to individuals, discrete communities, and small patches of benthic habitat. Those analyses 

would also detail site-specific protective mitigations required prior to approval of such activities.

Impact-Level Definitions

For this analysis, the following definitions were used to categorize impacts to deepwater 

benthic communities:

• Negligible – Impacts to deepwater benthic communities are largely 

undetectable. There is some potential for even undetectable impacts to cause 

slight changes to a local community’s species abundance and composition, 

community structure, and/or ecological functioning, but any such changes would 

be spatially localized, short term in duration, and would not alter the overall 

status of GOM deepwater benthic communities.

• Minor – Impacts to deepwater benthic communities are detectable but cannot be 

clearly distinguished from natural variation. Such impacts could result in 

changes to a local community’s species abundance and composition, community 

structure, and/or ecological functioning, but would be spatially localized, short 

term in duration, and would not alter the overall status of GOM deepwater 

benthic communities.

• Moderate – Impacts to deepwater benthic communities detectably cause 

substantial, population-level changes in species composition, community 

structure, and/or ecological functioning. These impacts would be expected to be 

spatially extensive but are expected to only temporarily alter the overall status of 

GOM deepwater benthic communities; long-term recovery to pre-impact levels is 

likely.

• Major – Impacts to deepwater benthic communities detectably cause substantial, 

population-level changes in species composition, community structure, and/or 

ecological functioning. These impacts would be expected to be spatially 

extensive and noticeably alter the overall status of GOM deepwater benthic 

communities such that long-term recovery to pre-impact levels is unlikely.
4-74 2018 Gulf of Mexico Supplemental EIS

Table 4-11. Deepwater Benthic Communities Impact-Producing Factors That Are Reasonably 

Foreseeable.

Deepwater Benthic 

Communities Magnitude of Potential Impact1 

Impact-Producing

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Bottom-Disturbing Activities and Drilling-Related Sediment and Waste Discharges

With Mitigation Negligible Negligible Negligible Negligible None

Without Mitigation

Minor to Minor to Minor to Minor to

None

Major Moderate Moderate Major

Accidental Impacts

Bottom-Disturbing Activities and Drilling-Related Sediment and Operational Waste Discharges

With Mitigation Negligible to Negligible to Negligible to Negligible to None

Minor Minor Minor Minor

Without Mitigation

Minor to Minor to Minor to Minor to

None

Major Moderate Moderate Major

Oil Spills

With Mitigation Negligible to Negligible to Negligible to Negligible to None

Minor Minor Minor Minor

Without Mitigation

Minor to Minor to Minor to Minor to

Major Moderate Moderate Major None

Cumulative Impacts

Incremental 

Contribution2 Negligible Negligible Negligible Negligible None

OCS Oil and Gas 

Program3

Negligible to

Minor

Non-OCS Oil and 

Gas Activities4

Negligible to

Major

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.4 of the 2017-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales. 

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

The OCS oil- and gas-related, impact-producing factors for deepwater benthic communities 

can be grouped into three main categories: (1) bottom-disturbing activities; (2) drilling-related 

sediment and waste discharges; and (3) noncatastrophic oil spills. These impact-producing factors 

have the potential to damage individual deepwater habitats and disrupt associated benthic 

communities if insufficiently distanced or otherwise mitigated. However, impacts from individual 
Description of the Affected Environment and Impact Analysis 4-75 

routine activities and accidental events are usually temporary, highly localized, and expected to 

impact only small numbers of organisms and substrates at a time. Moreover, use of the expected 

site-specific plan reviews/mitigations will distance activities from deepwater benthic communities, 

greatly diminishing the potential effects. Therefore, at the regional, population-level scope of this 

analysis, and assuming adherence to all expected regulations and mitigations, the incremental 

contribution would be expected to be negligible for any of the action alternatives. Impacts from 

accidental events would be expected to be negligible to minor for any of the action alternatives. 

The expected OCS oil- and gas-related activities from a proposed action would also contribute 

incrementally to the overall OCS oil- and gas-related and non-OCS oil- and gas-related cumulative 

effects experienced by deepwater benthic communities, but only by a negligible amount. Under 

Alternative E, the potential for impacts would be none because new impacts to deepwater benthic 

communities related to a cancelled lease sale would be avoided entirely. The overall OCS oil- and 

gas-related cumulative impacts to deepwater benthic communities are estimated to be negligible to 

minor. Non-OCS oil- and gas-related activities such as commercial fishing (currently negligible) and 

shifting baseline environmental conditions related to climate change (currently negligible but likely to 

increase to major over time should current trends continue or worsen) could cause more noticeable 

impacts on deepwater benthic communities over the next 50 years. A full analysis of deepwater 

benthic communities can be found in Chapter 4.4 of the 2017-2022 GOM Multisale EIS.

Comparison of Alternatives 

At the regional, population-level scope of this analysis, and assuming adherence to all 

expected regulations and mitigations, impacts from reasonably foreseeable routine activities would 

be expected to be negligible for any of the action alternatives. For Alternative B, proposed OCS 

oil- and gas-related activities would also contribute incrementally, but only a negligible amount, to 

the overall OCS oil- and gas-related and non-OCS oil- and gas-related cumulative effects 

experienced by deepwater benthic communities, assuming the continuation of expected mitigation 

practices. Alternative C would not fundamentally alter the conclusions reached for Alternative A, but 

it would reduce the potential impacts of a proposed lease sale in the available unleased blocks in the 

CPA/EPA. Although the area proposed for leasing in the WPA is relatively smaller than the 

proposed area of the CPA/EPA and would experience less projected OCS oil- and gas-related 

activity (refer to Chapter 3), deepwater benthic communities are found throughout all deep waters of 

the GOM and, therefore, the impacts associated with Alternative C could still potentially cause some 

population-level effects. Alternative D would do relatively little to reduce the impacts as a result of 

the routine activities, accidental events, or cumulative impacts to deepwater benthic communities. 

Deepwater benthic communities are generally found in depths >300 m (984 ft), and the vast majority 

of lease blocks covered by the exclusion areas in Alternative D are in shallower waters. It is 

believed that existing mitigation practices would continue to be applied to the proposed activities 

under Alternatives A-D, reducing the expected level of impacts from a single proposed lease sale to 

negligible for any of the action alternatives. Under Alternative E, a proposed lease sale would be 

cancelled; therefore, the potential for impacts of that proposed action would be none because new 

impacts to deepwater benthic communities related to a cancelled lease sale would be avoided 

entirely but existing activity would continue. Cumulative impacts of current and past activities (i.e., 
4-76 2018 Gulf of Mexico Supplemental EIS

OCS oil- and gas-related and non-OCS oil- and gas-related), however, would continue to occur 

under this alternative.

Incomplete or Unavailable Information

For decades, BOEM has funded research related to deepwater benthic environments in 

order to further the scientific understanding necessary for informed decisionmaking. However, due 

in part to the inherent difficulty of data collection in deepwater environments, there is (and likely 

always would be) incomplete or unavailable information about deepwater benthic communities. 

BOEM has specifically identified incomplete information for OCS oil- and gas-related impacts related 

to the following: locations of deepwater benthic communities in the GOM; toxicity of oil and 

dispersants to deepwater benthic organisms; long-term effects of the totality of the presence of OCS 

oil- and gas-related infrastructure; long-term effects associated with various climate change-related 

factors; cascading ecological effects and interactions between deepwater benthic communities and 

deepwater fish communities; and long-term impacts from the Deepwater Horizon explosion, oil spill, 

and response (refer to the Catastrophic Spill Events Analysis white paper [USDOI, BOEM, 2017b]).

BOEM’s databases of confirmed deepwater benthic communities and 3D seismic 

water-bottom anomalies are used when reviewing deepwater exploration and development plans. 

As part of postlease, site-specific development plans, operators must provide a variety of 

high-resolution survey data, including assessments of potential habitat for sensitive benthic 

communities. If data are sparse or additional detail is needed, site-specific video or photographic 

surveys can be requested and used to develop appropriate mitigations. While extremely helpful, 

BOEM’s databases and survey data are not comprehensive of all deepwater benthic communities. 

For example, available information may not always be of sufficient resolution to identify small areas 

of scattered hard substrate, such as dead clam shells, that may support small patches of deepwater 

benthic habitat, as discussed by Quattrini et al. (2013).

To help fill data gaps about locations of deepwater benthic communities, BOEM may also be 

able to make use of additional datasets created by other Federal agencies. For example, NOAA’s 

Deep Sea Coral Research and Technology Program and NOAA’s National Centers for Coastal 

Ocean Science have been compiling a database of known observations of deepwater corals and 

sponges (USDOC, NOAA, 2015). This database of confirmed deepwater coral observations could 

be used as an ancillary information source during site-specific plan reviews. However, even with the 

continued additions of observation records over time, it is unlikely that the majority of deepwater 

coral communities would be directly observed and documented because of the inherent logistical 

difficulties involved in deepwater research and data collection. Past research by NOAA (Kinlan 

et al., 2013) has also included efforts to predictively model suitable habitat for deepwater coral and 

sponges based on the best available physical/environmental datasets. Future research may 

improve on these efforts and expand to include chemosynthetic communities. New datasets and 

models such as these, once they are complete, scientifically vetted, and publicly available, could 

provide helpful ancillary information to further assist BOEM’s site-specific evaluations.
Description of the Affected Environment and Impact Analysis 4-77

BOEM will continue to analyze and support the continued collection of the best available 

scientific information related to deepwater benthic communities. However, the best available 

information does not provide all of the data necessary for a complete understanding of these 

communities. For example, there is incomplete information with respect to potential long-term 

effects resulting from exposure to spilled oil, including potential impacts of a catastrophic spill such 

as the Deepwater Horizon oil spill. Known information about the potential impacts of a theoretical 

catastrophic spill is detailed in the Catastrophic Spill Events Analysis white paper (USDOI, BOEM, 

2017b), and further information was made available with the publication of NOAA’s Deepwater 

Horizon Oil Spill: Final Programmatic Damage Assessment and Restoration Plan and Final 

Programmatic Environmental Impact Statement in 2016 (Deepwater Horizon Natural Resource 

Damage Assessment Trustees, 2016). The content of that report was reviewed as part of this 

analysis. Some information related to impacts specific to the Deepwater Horizon explosion, oil, spill, 

and response, such as long-term monitoring results, is still incomplete or unavailable. Impending 

reports are not expected to reveal additional significant effects that would alter the overall 

conclusions about reasonably foreseeable impact-producing factors associated with a proposed 

action. In completing this analysis and in making conclusions, BOEM used the best available 

science to determine the range of reasonably foreseeable impacts, applying accepted scientific 

methodologies to both integrate existing information and extrapolate potential outcomes. Therefore, 

BOEM has determined that the incomplete information is not essential to a reasoned choice among 

alternatives.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including literature from relevant peer-reviewed 

journals and reports) were examined to assess recent information regarding deepwater benthic 

communities that may be pertinent to a proposed action. No new information that would add to the 

analyses or change the conclusions was discovered since publication of the 2017-2022 GOM 

Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for deepwater benthic communities presented in the 

2017-2022 GOM Multisale EIS, with the understanding that no new information on deepwater 

benthic communities has been published since the publication of the 2017-2022 GOM Multisale EIS. 

Therefore, no new information was discovered that would alter the impact conclusion for deepwater 

benthic communities presented in that document, and the analysis and potential impacts detailed in 

the 2017-2022 GOM Multisale EIS still apply for the remaining proposed GOM lease sales in the 

Five-Year Program. 

4.5 SARGASSUM AND ASSOCIATED COMMUNITIES

Summary

BOEM has reexamined the analysis for Sargassum and associated communities presented 

in the 2017-2022 GOM Multisale EIS based on the information presented below. No new 
4-78 2018 Gulf of Mexico Supplemental EIS

information was discovered that would alter the impact conclusion for Sargassum and associated 

communities presented in the 2017-2022 GOM Multisale EIS. Further, the analysis and potential 

impacts detailed in that document still apply for the remaining proposed GOM lease sales in the 

Five-Year Program. 

A detailed description of Sargassum and associated communities, along with the full 

analyses of the potential impacts of routine activities, accidental events, and cumulative impacts 

associated with the proposed action are presented in Chapter 4.5 of the 2017-2022 GOM Multisale 

EIS. The following information is a summary of the resource description and impact analysis 

incorporated from the 2017-2022 GOM Multisale EIS.

Introduction

Sargassum is a genus of large brown seaweed (a type of algae) that floats in island-like 

masses (USDOC, NOAA, Office of Ocean Exploration and Research, 2014). In the Gulf of Mexico, 

Sargassum and the organisms that reside within or around the matrix of plants are some of the most 

widely distributed and easily recognizable species in the GOM. Sargassum, as pelagic algae, is a 

widely distributed resource that is ubiquitous throughout the northern GOM and northwest Atlantic, 

and is part of a cycle that spans most of the Northern Hemisphere of the Atlantic Ocean, including 

the Caribbean Sea. As such, Sargassum might be potentially vulnerable to OCS oil- and gas-related 

activities, and it is necessary to examine the potential impact-producing factors and determine the 

susceptibility to these impacts as they relate to a proposed action.

Sargassum in the GOM is comprised of S. natans and S. fluitans (Lee and Moser, 1998; 

Stoner, 1983; Littler and Littler, 2000) and is characterized by a brushy, highly branched thallus with 

numerous leaf-like blades and berrylike pneumatocysts (Coston-Clements et al., 1991; Lee and 

Moser, 1998; Littler and Littler, 2000). The Sargassum cycle is expansive, encompassing most of 

the western Atlantic Ocean and the Gulf of Mexico with the growth, death, and decay of these plant 

and epiphytic communities, which may play a substantial role in the global carbon cycle (Gower and 

King, 2008). 

To facilitate a discussion on the spatial extent of the Sargassum cycle and to put the impactproducing factors in context, Figure 4-8 depicts how these plants move around the Northern 

Hemisphere. The Sargassum loop system initiates in the Sargasso Sea. Atmospheric conditions 

create wind patterns that push Sargassum south, into the Caribbean Sea where it is pushed west by 

the oceanic and atmospheric currents carrying it into the Gulf of Mexico. There it washes ashore on 

the Gulf Coast or gets swept out the Florida Strait via the Gulf Stream (Gower et al., 2013; Frazier 

et al., 2015). Figure 4-8 represents the spatial extent of Sargassum, demonstrating that there is a 

high degree of connection among the Gulf of Mexico OCS planning areas and other oceanic basins 

and large-scale oceanic features (e.g., Gulf Stream).
Description of the Affected Environment and Impact Analysis 4-79

Figure 4-8. Sargassum Loop System (adapted from Gower et al., 2013, and Frazier et al., 2015).

Analysis

The analysis is focused on the potential impact-producing factors from OCS oil- and gasrelated routine activities (i.e., exploration, development, and production), accidental events, and 

cumulative activities (Table 4-12). The impact-level definitions and the analyses supporting these 

conclusions are discussed below. During this analysis, many potential impact-producing factors 

were identified; however, only several posed enough of a potential threat to carry forward to a full 

analysis. (Refer to Chapter 4.5 of the 2017-2022 GOM Multisale EIS for a discussion of these 

analyses.) As such, only the following impact-producing factors were identified as having the 

potential to impact Sargassum and were carried forward to a full analysis:

• vessel operations (Chapter 3.2.1.5; routine and accidental, including 

discharges);

• chemical and drilling-fluid spills (Chapter 3.2.1.1; accidental only);

• oil spills (Chapter 3.2.2; accidental only); and

• oil-spill cleanup (Chapter 3.2.3; accidental only).
4-80 2018 Gulf of Mexico Supplemental EIS

Impact-Level Definitions

For this analysis, the following criteria were used to categorize the effects of impactproducing factors to Sargassum and associated communities:

• Negligible – Impacts are undetectable or limited in scale to the immediate area 

of the impact-producing factor. This may include mortality of the plants or 

animals associated with Sargassum. Such impacts may result in changes to a 

local community’s species abundance and composition, community structure, 

and/or ecological functioning, but any such changes would be spatially localized, 

short term in duration, and would not alter the overall status of Sargassum or 

associated communities in the GOM.

• Minor – Impacts are detectable and result in changes beyond the immediate 

area of the impact-producing factor. Such impacts could result in noticeable 

changes to a local community’s species abundance and composition, community 

structure, and/or ecological functioning, but would be spatially localized, short 

term in duration, and would not alter the overall status of Sargassum or 

associated communities in the GOM.

• Moderate – Impacts cause substantial, population-level changes in species 

composition, community structure, and/or ecological functioning beyond the 

immediate area of the impact-producing factor. These impacts would be 

expected to be spatially extensive and may impact communities that rely on 

Sargassum for the transportation of larvae, settlement, or food beyond the area 

of the impact-producing factor. However, impacts to Sargassum and associated 

communities are expected to be temporary, and there would be no disruption of 

the global Sargassum cycle. 

• Major – Impacts result in the loss of Sargassum over large sections of the GOM. 

This would result in substantial, population-level changes in species composition, 

community structure, and/or ecological functioning for Sargassum and 

communities that rely on Sargassum for the transportation of larvae, settlement, 

or food beyond the area of the impact-producing factor. These impacts would be 

expected to be spatially extensive and possibly disrupt the global Sargassum

cycle. 

The potential magnitude of impact for each of these impact-producing factors is provided in 

Table 4-12 to help the reader quickly identify the level of potential impacts for Sargassum and its 

associated communities.
Description of the Affected Environment and Impact Analysis 4-81

Table 4-12. Sargassum and Associated Communities Impact-Producing Factors That Are Reasonably 

Foreseeable.

Sargassum and 

Associated Communities Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Vessel Operations Negligible Negligible Negligible Negligible None

Drilling Operations Negligible Negligible Negligible Negligible None

Accidental Impacts

Drilling Operations Negligible Negligible Negligible Negligible None

Vessel Operations Negligible Negligible Negligible Negligible None

Oil Spill and Cleanup Negligible Negligible Negligible Negligible None

Cumulative Impacts

Incremental 

Contribution2 Negligible Negligible Negligible Negligible None

OCS Oil and Gas3 Minor to 

Moderate

Non-OCS Oil and Gas4 Negligible

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.5 of the 2017-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

Several impact-producing factors can affect Sargassum, including vessel-related operations, 

oil and gas drilling discharges, operational discharges, accidental spills, non-OCS oil- and 

gas-related vessel activity, and coastal water quality. Routine vessel operations and accidental 

events that occur during drilling operations or vessel operations, and oiling due to an oil spill were 

the impact-producing factors that could be reasonably expected to impact Sargassum populations in 

the GOM. All of these impact-producing factors would result in the death or injury to the Sargassum 

plants or to the organisms that live within or around the plant matrix. However, the unique and 

transient characteristics of the life history of Sargassum and the globally widespread nature of the 

plants and animals that use the plant matrix buffer against impacts that could occur at any given 

location. Impacts to the overall population of the Sargassum community are therefore expected to 

be negligible from either routine activities or reasonably foreseeable accidental events for any of the 

action alternatives. The incremental impact of a proposed action on the population of Sargassum 

would be negligible when considered in the context of cumulative impacts to the population. Under 

Alternative E, a proposed lease sale would be cancelled and the potential for impacts from routine 

activities and accidental events would be none. Cumulative impacts of current and past activities 

(i.e., OCS oil- and gas-related and non-OCS oil- and gas-related), however, would continue to occur 
4-82 2018 Gulf of Mexico Supplemental EIS

under this alternative. Impacts from changing water quality would be much more influential on 

Sargassum than OCS development and would still occur without the presence of OCS oil- and 

gas-related activities.

Comparison of Alternatives

Sargassum has a yearly cycle that promotes quick recovery from impacts. Therefore, most 

routine and accidental impact-producing factors for Alternatives A-D would be expected to result in 

negligible impacts because they only impact a small percentage of the population and because 

impacts would be limited in size and scope as new plants rapidly replace the impacted plants. 

Under Alternative E, a proposed lease sale would be cancelled and the potential for impacts from 

routine activities and accidental events would be none. Under Alternative E, impacts to Sargassum 

would be limited to cumulative impacts associated with past, present, and future OCS oil- and 

gas-related development and non-OCS oil- and gas-related activities.

Incomplete or Unavailable Information

Although much is known about Sargassum and its life history, incomplete or unavailable 

information still remains. This incomplete or unavailable information includes information on the 

effects of in situ oil exposure and the factors impacting the movement patterns of Sargassum. 

BOEM used existing information and reasonably accepted scientific methodologies to extrapolate in 

completing the analysis above. BOEM has determined that there are few foreseeable significant 

adverse impacts to the Sargassum population associated with a proposed action, 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) built upon these studies and developed a more finite life cycle for Sargassum that links the 

Sargasso Sea Sargassum populations with the GOM populations. With respect to the effects of 

oiling from the Deepwater Horizon oil spill, 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 Sargassum coming into contact with surface oil. Additionally, 

Lindo-Atichati et al. (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. Ultimately, the ephemeral and wide-ranging nature across the northern 

GOM and the reproductive capabilities of Sargassum provide a life history that is resilient towards 

localized or short-term deleterious impacts, such as those expected to be associated with OCS 

oil- and gas-related routine activities and noncatastrophic oil or synthetic-based fluid 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 unavailable 

information is acceptable for this analysis.
Description of the Affected Environment and Impact Analysis 4-83

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including the U.S. Department of the Interior, NOAA, 

Fisheries and Ocean Canada, Texas A&M University, University of Southern Mississippi, and 

scientific publication databases including Science Direct, Elsevier, and JSTOR) were examined to 

assess recent information regarding Sargassum and associated communities that may be pertinent 

to a proposed action. No new information that would add to the analyses or change the conclusions 

was discovered since publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for Sargassum and associated communities presented 

in the 2017-2022 GOM Multisale EIS, with the understanding that no new information on Sargassum

and associated communities has been published since the publication of the 2017-2022 GOM 

Multisale EIS. Therefore, no new information was discovered that would alter the impact conclusion 

for Sargassum and associated communities presented in that document, and the analysis and 

potential impacts detailed in the 2017-2022 GOM Multisale EIS still apply for the remaining proposed 

GOM lease sales in the Five-Year Program. 

4.6 LIVE BOTTOM HABITATS

This chapter describes shallow-water hard/live bottom habitats in Gulf of Mexico OCS 

planning areas. Hard bottoms are naturally occurring, rocky, consolidated substrates that are 

geological (e.g., exposed sedimentary bedrock) or biogenic (e.g., carbonate relic coral reef) in origin. 

These habitats occur throughout the GOM but are relatively rare compared with the soft bottoms that 

are ubiquitous. Hard bottoms, particularly those having measurable vertical relief, can serve as 

important habitat for a wide variety of marine organisms. Encrusting algae and sessile invertebrates 

such as corals, sponges, sea fans, sea whips, hydroids, anemones, ascidians, and bryozoans may 

attach to and cover hard substrates, thereby creating “live bottoms,” a term first coined by Cummins 

et al. (1962). The attached flora and fauna of live bottoms, such as large sponges and structureforming corals, further enhance the structural complexity of the benthic environment. Complex 

structure offers shelter that can be attractive to smaller invertebrates and fishes (Fraser and 

Sedberry, 2008), which, in turn, can provide food for a variety of larger fishes, including some 

commercially important fisheries (Szedlmayer and Lee, 2004; Gallaway et al., 2009). Refer to 

Chapter 4.7 (“Fishes and Invertebrate Resources”) and the Essential Fish Habitat Assessment white 

paper (USDOI, BOEM, 2016d) for more detail. Seagrasses can also be considered a type of live 

bottom, but they have very different physical characteristics and species assemblages than the 

above and are thus analyzed separately in Chapter 4.3.1. 

Defined topographic features (Chapter 4.6.1) are a subset of GOM hard bottom habitats that 

are large enough to have an especially important ecological role, with specific protections defined in 

the Topographic Features Stipulation. In Figure 4-9, the smaller black polygons represent the 

38 named topographic features. Pinnacle features are much smaller in size than these topographic 

features and are found on specific lease blocks in the CPA and EPA (i.e., the areas shown in red in 
4-84 2018 Gulf of Mexico Supplemental EIS

Figure 4-9), with the highest known concentrations of other live bottom features. The Topographic 

Features Stipulation and Live Bottom (Pinnacle Trend) Stipulation are described in Appendix D of 

the 2017-2022 GOM Multisale EIS. The Secretary of the Interior has decided in the Record of 

Decision for the Five-Year Program to include the Protection of Biologically Sensitive Underwater 

Features as landscape mitigation for the 10 proposed lease sales in the GOM (USDOI, BOEM, 

2017c). Live bottom habitats found outside the stipulation lease blocks are not specifically included 

in the stipulations, but they are still given site-specific protections by BOEM during site-specific plan 

reviews (refer to Appendix B of the 2017-2022 GOM Multisale EIS). The GOM live bottoms are not 

limited to the features/areas identified in Figure 4-9. 

Figure 4-9. Lease Blocks Subject to the Topographic Features and Live Bottom (Pinnacle Trend) 

Stipulations.

4.6.1 Topographic Features and Associated Communities

Summary

BOEM has reexamined the analysis for topographic features and associated communities 

presented in the 2017-2022 GOM Multisale EIS based on the additional information presented 

below. No new information was discovered that would alter the impact conclusion for topographic 

features and associated communities presented in the 2017-2022 GOM Multisale EIS. Further, the 

analysis and potential impacts detailed in that document still apply for the remaining proposed GOM 

lease sales in the Five-Year Program. 

A detailed description of topographic features and associated communities, along with the 

full analyses of the potential impacts of routine activities, accidental events, and cumulative impacts 

associated with a proposed action are presented in Chapter 4.6.1 of the 2017-2022 GOM Multisale 

EIS. The following information is a summary of the resource description and impact analysis 
Description of the Affected Environment and Impact Analysis 4-85

incorporated from the 2017-2022 GOM Multisale EIS. Any new information that has become 

available since that document was published is presented below.

Introduction

Topographic features (also called banks) are a subset of hard bottom habitats found in the 

GOM that are large enough in individual size to have a particularly important role in the GOM 

ecosystem. Although large in size, these features (and hard bottom habitats as a whole) are 

relatively rare compared with the expansive soft bottoms found throughout the GOM (Parker et al., 

1983). Topographic features can be created through the uplift of bedrock by underlying salt diapirs 

or by the exposure of fossilized barrier islands, or they can be formed from relic carbonate reefs 

(Rezak and Bright, 1981a and 1981b; Berryhill et al., 1987). Regardless of origin, these subsea 

banks provide areas of hard substrate that support benthic and fish communities with relatively high 

biomass, diversity, and abundance. The structurally complex habitats of these features also provide 

shelter, food, and nursery grounds that support large numbers of commercially and recreationally 

important fishes (Johnston et al., 2015; Nash et al., 2013). Many of these habitats remain relatively 

pristine and have a high aesthetic and scientific value, in part because they represent ecological 

and/or geographic extremes for many species (Rezak and Bright, 1981a; Nash et al., 2013; 

Johnston et al., 2015).

Topographic features and associated communities in the GOM are subject to an array of 

environmental conditions, resulting in a large number of ecological community types. This includes 

a range from the highly productive hermatypic (i.e., reef building) corals found at the Flower Garden 

Banks to habitats such as Dunn Bar that posess less productive and less diverse benthic habitats, 

yet are still known to concentrate fishes (Rezak and Bright, 1981b; Nash et al., 2013).

Protective Measures for Topographic Features

Within the Gulf of Mexico, BOEM has identified 38 topographic features with sufficiently 

unique geography and ecology (Rezak and Bright, 1981a; Rezak et al., 1983) to continue warranting 

some degree of protection from OCS oil- and gas-related activities. There are 22 topographic 

features in the WPA, 16 in the CPA, and 0 in the EPA (Figure 4-9). In the Gulf of Mexico, 

topographic features are known to function as large-sized, hard substrate habitats that enable 

settlement of sensitive benthic organisms, concentrate fishes, and substantially contribute to the 

ecology of the GOM. Many of these features have been identified as locations of particular value 

that may require a greater degree of protection from OCS oil- and gas-related activities. As such, 

beginning in 1973, BOEM’s predecessor agency established and implemented a Topographic 

Features Stipulation (also referred to in this chapter just as “the Stipulation”) that applies conditions 

to OCS oil- and gas-related activities occurring in the vicinity of these features.

Adherence to the provisions of this stipulation helps protect the resources by distancing OCS 

oil- and gas-related activities away from the most sensitive areas of topographic features in order to 

minimize any negative impacts of routine activities and accidental events on associated benthic 

communities. Historically, this stipulation has been applied consistently to all leases in OCS areas 
4-86 2018 Gulf of Mexico Supplemental EIS

with defined topographic features. With the approval of the Five-Year Program, the Topographic 

Features Stipulation is now a required mitigation. The Stipulation establishes a No Activity Zone 

around the most ecologically sensitive core area of each identified topographic feature, within which 

no bottom-disturbing activities are allowed. Additionally, BOEM extends a 500-ft (152-m) buffer 

around each of these No Activity Zone boundaries, further restricting bottom-disturbing activity. The 

additional 500-ft (152-m) buffer policy was developed in consultation with NOAA to further protect 

areas of topographic features that were not originally included in the defined No Activity Zones. In 

addition, for most of the features, the Stipulation also establishes variably sized concentric shunting 

zones surrounding the No Activity Zones, within which BOEM requires that drill cuttings and drilling 

fluids be shunted to near the seafloor to minimize the seafloor area affected by the cuttings and 

fluids.

Refer to Appendix D of the 2017-2022 GOM Multisale EIS for further details of the Stipulation 

and NTL 2009-G39, “Biologically-Sensitive Underwater Features and Areas,” which provides 

information and consolidates guidance to help operators understand BOEM’s requirements related 

to sensitive shallow-water benthic habitats. These requirements are designed to prevent or limit any 

impacts resulting from routine activities and accidental events to topographic features. This analysis 

assumes that these (or functionally equivalent) protections will continue to be a requirement for OCS 

oil- and gas-related activities resulting from a proposed action throughout the 50-year analysis 

period. Furthermore, the Secretary of the Interior has decided in the Record of Decision for the 

Five-Year Program to include the Protection of Biologically Sensitive Underwater Features as 

landscape mitigation for the 10 proposed lease sales in the GOM (USDOI, BOEM, 2017c).

Analysis

This analysis considers the reasonably foreseeable impacts of a proposed action’s routine 

activities, accidental events, and incremental contribution to cumulative impacts on GOM 

topographic features and these physical features’ associated benthic communities (hereafter 

referred to as “topographic features”) over a 50-year period. Because a catastrophic oil spill is not 

considered reasonably foreseeable, those potential impacts (including long-term recovery) are 

addressed in the Catastrophic Spill Event Analysis white paper (USDOI, BOEM, 2017b). The impact 

significance criteria and resulting conclusions presented here (Table 4-13) focus on the overall 

functioning, resilience, and ecosystem level importance of topographic features throughout U.S. 

waters of the GOM.

Because of the similarity and overlap of the effects of many OCS oil- and gas-related 

activities that occur in the OCS, the impact-producing factors considered for topographic features 

can be divided into three broad categories: drilling and exploration operations; vessel operations; 

and oil spill and associated cleanup activities. An in-depth analysis of these potential 

impact-producing factors determined that, although many may occur within the GOM, few could 

occur at an extent sufficient to cause impacts to the topographic features as a whole (Table 4-13), 

partly because these topographic features are spread widely across the GOM. The potential 

magnitude of impact for each of the analyzed impact-producing factors is provided in Table 4-13 to 
Description of the Affected Environment and Impact Analysis 4-87

help the reader quickly identify the level of potential impacts for each impact-producing factor. The 

impact-level definitions and the analyses supporting these conclusions are discussed below. The 

following impact-producing factors were carried forward to a full analysis for routine activities and 

accidental events:

• Routine Activities

− Drilling, exploration, and decommissioning (bottom-disturbing activities)

− Vessel operation (bottom-disturbing activities)

• Accidental Events

− Drilling, exploration, and decommissioning

 Bottom-disturbing activities

 Chemical and drilling-fluid spills

− Vessel operation (bottom-disturbing activities)

− Oil spill and associated cleanup

 Large and small spills resulting from surface or subsea sources

 Cleanup operations not related to vessel operations

Of all the possible impact-producing factors, it was determined that bottom-disturbing 

activities associated with drilling, exploration, and vessel operations were the only impact-producing 

factors from routine activities that could be reasonably expected to substantially impact topographic 

features. The impact-producing factors also include the release of sediments and toxins during 

drilling operations. Oil-spill response-related activities were also considered to be a potential source 

of impacts to topographic features. Refer to Chapter 4.6.1 of the 2017-2022 GOM Multisale EIS for 

further detail on the analyses in this chapter and for the analyses that were not carried forward.

Impact-Level Definitions

For this analysis, the following definitions were used to categorize impacts to topographic 

features and associated communities:

• Negligible – Impacts to topographic feature communities are largely 

undetectable. There is some potential for even undetectable impacts to cause 

slight changes to a local community’s species abundance and composition, 

community structure, and/or ecological functioning, but any such changes would 

be spatially localized, short term in duration, and would not impact other 

topographic features.

• Minor – Impacts to topographic feature communities are detectable but cannot 

be distinguished from natural variation. Such impacts could result in noticeable 
4-88 2018 Gulf of Mexico Supplemental EIS

changes to a local community’s species abundance and composition, community 

structure, and/or ecological functioning, but would be spatially localized, short 

term in duration, and recovery would be expected.

• Moderate – Impacts to topographic feature communities that result in 

substantial, population-level changes in species composition, community 

structure, and/or ecological functioning. These impacts would be expected to be 

spatially extensive, spanning across several topographic features, but impacts 

are expected to result in temporary changes and recovery would be likely.

• Major – Impacts to topographic feature communities that result in substantial, 

population-level changes in species composition, community structure, and/or 

ecological functioning. These impacts would be expected to be spatially 

extensive and noticeably alter the overall status of many topographic features in 

the GOM. Long-term recovery to pre-impact community structure, species 

abundance, or ecological function is unlikely.

Table 4-13. Topographic Features and Associated Communities Impact-Producing Factors That Are 

Reasonably Foreseeable. 

Topographic 

Features Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Bottom-Disturbing Activities Associated with Drilling, Exploration, and Decommissioning

With Mitigation Negligible Negligible Negligible Negligible None

Without Mitigation Moderate Moderate Moderate Negligible None

Bottom-Disturbing Activities Associated with Vessel Operations

With Mitigation Negligible Negligible Negligible Negligible None

Without Mitigation Moderate Moderate Moderate Negligible None

Accidental Impacts

Bottom-Disturbing Activities Associated with Drilling, Exploration, and Decommissioning

With Mitigation Negligible Negligible Negligible Negligible None

Without Mitigation Moderate Moderate Moderate Negligible None

Chemical and Drilling-Fluid Spills

With Mitigation Negligible Negligible Negligible Negligible None

Without Mitigation Moderate Moderate Moderate Negligible None

Vessel Operations 

Bottom-Disturbing Activities Associated with Vessel Operations

With Mitigation Negligible Negligible Negligible Negligible None

Without Mitigation Moderate Moderate Moderate Negligible None
Description of the Affected Environment and Impact Analysis 4-89

Topographic 

Features Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Oil Spills and Associated Cleanup Activities

Large and Small Spills Resulting from Surface or Subsea Sources

With Mitigation Negligible Negligible Negligible Negligible N/A

Without Mitigation Moderate Moderate Moderate Negligible None 

Cleanup Operations Not Related to Vessel Operation

With Mitigation Negligible Negligible Negligible Negligible None

Without Mitigation Moderate Moderate Moderate Negligible None

Cumulative Impacts

Incremental 

Contribution2 Negligible Negligible Negligible Negligible None

OCS Oil and Gas3 Negligible

Non-OCS Oil and 

Gas4

 

Negligible to

Moderate

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.6.1 of the 2017-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales. 

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

Adherence to the Topographic Features Stipulation (a required mitigation as a result of the 

Five-Year Program’s Record of Decision) is analyzed in each action alternative and detailed in 

Appendix D of the 2017-2022 GOM Multisale EIS. Application of the Topographic Features 

Stipulation would assist in preventing or at least minimizing potential impacts to topographic feature 

communities by increasing the distance of OCS oil- and gas-related activities from these features. 

The historical application of this stipulation has resulted in negligible impacts of a proposed action 

to topographic features from routine activities and accidental events. The incremental contribution of 

a proposed action to the overall cumulative impacts is also expected to be negligible, with 

adherence to the required Topographic Features Stipulation. Under Alternative E, the potential for 

new incremental impacts to topographic features from a cancelled lease sale would be none

because they would be avoided entirely. Cumulative impacts of current and past activities (i.e., OCS

oil- and gas-related and non-OCS oil- and gas-related), however, would continue to occur under this 

alternative. Impacts ranging from negligible to moderate may still be expected from non-OCS 

oil- and gas-related activities factors such as fishing, pollution, and climate change; however, the 

incremental impact of the proposed activities should not result in a meaningful augmentation of 

overall expected impacts. A full analysis of topographic features can be found in Chapter 4.6.1 of 

the 2017-2022 GOM Multisale EIS.
4-90 2018 Gulf of Mexico Supplemental EIS

Comparison of Alternatives

Overall, given adherence to the Topographic Features Stipulation (which is a required 

mitigation as a result of the Five-Year Program’s Record of Decision), reasonably foreseeable 

impacts to topographic features from routine activities, accidental events, and the cumulative 

impacts for any of the action alternatives (i.e., Alternatives A-D) are expected to be negligible. 

Alternative B or C would not fundamentally alter the conclusions reached under Alternative A. Many 

OCS lease blocks near the features are already leased, and impacts from non-OCS oil- and 

gas-related activities are not expected to decrease. Under Alternative D, BOEM could hold a lease 

sale excluding leasing of any and/or all blocks subject to the Topographic Features, Live Bottom 

(Pinnacle Trend), and Blocks South of Baldwin County, Alabama, Stipulations. Topographic 

features could experience fewer impacts through the additional distancing of OCS oil- and 

gas-related activities, further reducing the probability of impacts. An accidental spill may still reach a 

topographic feature, but it is expected that the increased distance would provide more dispersal time 

as the spill travels the additional distance across unleased blocks. Alternative D would do little to 

change the overall cumulative impacts to topographic features. Many OCS lease blocks near the 

features are already leased, and impacts from non-OCS oil- and gas-related activities are not 

expected to decrease. Under Alternative E, a proposed lease sale would be cancelled. Therefore, 

the potential for new incremental impacts would be none because new OCS oil- and gas-related 

impacts to topographic features related to the cancelled lease sale would be avoided entirely. 

However, the level of cumulative impacts could still potentially increase over time, even eventually 

rising to moderate, should current trends of these activities continue or worsen, regardless of 

whether or not a single proposed lease sale would be held.

Incomplete or Unavailable Information

BOEM recognizes that there is incomplete or unavailable information related to topographic 

features and associated communities in general and specifically in relation to routine activities, 

accidental events, and cumulative impacts. However, the information that is known is adequate to 

come to a determination with respect to reasonably foreseeable impact-producing factors associated 

with a proposed action.

Research in offshore marine systems is logistically complex and requires substantial 

resources. As such, the total amount of research on these features and their communities is 

relatively limited, although BOEM and its predecessor agencies have funded numerous studies over 

the past 40 years. 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 the physical mixing of surface oil with the known depths of topographic features. 

Even though oil measurements were not collected at every feature under every condition, the 

available results suggest that topographic features exist at depths deeper than lethal concentrations 

of oil would be expected (Lange, 1985; McAuliffe et al., 1975 and 1981; Tkalich and Chan, 2002; 

Rezak et al., 1983; Wyers et al., 1986). Mixing to depth might occur, but it would be limited to 

unusual combinations of conditions such as when tropical storms pass directly over oiled surface 

waters (e.g., Silva et al., 2015). Moreover, the amounts of oil/dispersant mixture involved in that 
Description of the Affected Environment and Impact Analysis 4-91

situation greatly exceeds the amounts considered in the “Accidental Events” analysis in Chapter 

4.6.1 of the of the 2017-2022 GOM Multisale EIS. Given the geographic and temporal scope of a 

proposed action, it is believed that even impacts resulting from that particular situation would still 

only have a slight impact on the overall status of the topographic features and associated 

communities. However, the example demonstrates the point that the body of literature supporting 

impact analysis is still growing and requires continual review by BOEM.

Since the 1970s, BOEM and its predecessor agencies have supported continuous 

monitoring of the Flower Garden Banks for any impacts related to OCS oil- and gas-related 

activities. At the Flower Garden Banks, corals have generally flourished (refer to Johnston et al., 

2015, and references therein) even as OCS oil- and gas-related development has occurred, 

sometimes just outside of the No Activity Zone. Since corals are generally considered to be more 

fragile than most other types of organisms found on topographic features, it is also reasonable to 

conclude that topographic features with more resilient organisms than the Flower Garden Banks 

have not been negatively affected by OCS oil- and gas-related development in the GOM. However, 

given the ecological sensitivity of benthic communities on topographic features, continued research 

and monitoring efforts are necessary to maintain a sufficient understanding of the various potential 

impacts from OCS oil- and gas-related and non-OCS oil- and gas-related activities. A recent 

example illustrates how conditions could potentially change. In August 2017, a routine National 

Marine Sanctuary/BOEM long-term monitoring cruise in the East Flower Garden Bank documented a 

mortality event affecting corals and other benthic organisms in a localized area. At the time of this 

writing, tissue and water quality samples have been collected but not yet analyzed, and no causes 

have been indicated. BOEM will continue cooperating with the Sanctuary and other partners to 

evaluate information as it becomes available and will update future Supplemental EISs as 

necessary.

BOEM has used existing information and reasonably accepted scientific methodologies to 

extrapolate from available information in completing this analysis and formulating the conclusions 

presented here. Known information about potential impacts of a theoretical catastrophic spill is 

detailed in the Catastrophic Spill Events Analysis white paper (USDOI, BOEM, 2017b), and further 

information was made available with the publication of the Trustees’ PDARP/PEIS in 2016 

(Deepwater Horizon Natural Resource Damage Assessment Trustees, 2016). The content of that 

report was reviewed as part of this analysis. Some information related to impacts specific to the 

Deepwater Horizon explosion, oil, spill, and response, such as long-term monitoring results, is still 

incomplete or unavailable. Impending reports are not expected to reveal additional significant 

effects that would alter the overall conclusions about reasonably foreseeable impact-producing 

factors associated with a proposed action. BOEM has determined that such additional information 

could not be timely acquired and incorporated into the current analysis. However, the currently 

available body of evidence supports past analyses and does not indicate severe adverse impacts to 

topographic features linked to the Deepwater Horizon explosion, oil, spill, and response for 

topographic features. Impending reports are not expected to reveal additional significant effects that 

would alter the overall conclusions about reasonably foreseeable impact-producing factors 
4-92 2018 Gulf of Mexico Supplemental EIS

associated with a proposed action. Therefore, BOEM has determined that the incomplete or 

unavailable information is not essential to a reasoned choice among alternatives.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including literature from relevant peer-reviewed 

journals and reports) were examined to assess recent information regarding topographic features 

and associated communitites that may be pertinent to a proposed action. New information relevant 

to an analysis of the potential impacts of OCS oil- and gas-related activities on topographic features 

and associated communities has been released since publication of the 2017-2022 GOM Multisale 

EIS.

In August 2016, a routine National Marine Sanctuary/BOEM long-term monitoring cruise in 

the East Flower Garden Bank documented a mortality event affecting corals and other benthic 

organisms in a localized area. At the time of this writing, tissue and water quality samples have 

been collected and some analyses completed. The Flower Garden Banks National Marine 

Sanctuary is awaiting reports from the participating laboratories; no specific causes have been 

identified. BOEM will continue cooperating with the Sanctuary and other partners to evaluate 

information as it becomes available and will update future Supplemental EISs as necessary.

Conclusion

BOEM has reexamined the analysis for topographic features and associated communities 

presented in the 2017-2022 GOM Multisale EIS based on the additional information presented 

above. No new information was discovered that would alter the impact conclusion for topographic 

features and associated communities presented in the 2017-2022 GOM Multisale EIS, and the 

analysis and potential impacts detailed in that document still apply for the remaining proposed GOM 

lease sales in the Five-Year Program. 

4.6.2 Pinnacles and Low-Relief Features and Associated Communities

Summary

BOEM has reexamined the analysis for Pinnacles and low-relief features and associated 

communities presented in the 2017-2022 GOM Multisale EIS based on the additional information 

presented below. No new information was discovered that would alter the impact conclusion for 

Pinnacles and low-relief features and associated communities presented in the 2017-2022 GOM

Multisale EIS. Further, the analysis and potential impacts detailed in that document still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of Pinnacles and low-relief features and associated communities, 

along with the full analyses of the potential impacts of routine activities, accidental events, and 

cumulative impacts associated with a proposed action are presented in Chapter 4.6.2 of the 

2017-2022 GOM Multisale EIS. The following information is a summary of the resource description 

and impact analysis incorporated from the 2017-2022 GOM Multisale EIS.
Description of the Affected Environment and Impact Analysis 4-93

Introduction

The terms live bottom and hard bottom are often used interchangeably, but they are actually 

distinct, since it is possible to have hard bottom that is not live bottom. Hard substrates can form 

crusts, pavements, pinnacles, ledges, outcrops, and other reefal features (Jenkins, 2011). These 

harder substrates may or may not be covered by a thin veneer of muddy or sandy sediments that 

can be deposited and removed over time by currents and storms. Hard substrates with the lowest 

vertical relief are the most likely to be routinely buried and exposed. Encrusting algae and sessile 

invertebrates regularly attach to and cover exposed hard substrates, creating live bottoms. For the 

purposes of the Live Bottom Stipulation, which is a required mitigation as a result of the Five-Year 

Program’s Record of Decision, “live bottom areas” have been defined as communities or areas that 

contain biological assemblages consisting of sessile invertebrates such as sea fans, sea whips, 

hydroids, anemones, ascidians, sponges, bryozoans, or corals living upon and attached to naturally 

occurring hard or rocky formations with rough, broken, or smooth topography; or areas whose 

lithotope (substrate type) favors the accumulation of turtles, fishes, and other fauna. Large, 

shallow-water coral reefs created via biogenic deposition of calcium carbonate are only known to be 

present at the southern end of the EPA and on a few topographic features in the WPA and CPA 

(refer to Chapter 4.6.1 above). While the general public often thinks of such biogenic coral reefs as 

the only natural habitat for corals, for most of their geological history, corals have existed in less 

extensive epibenthic communities that are not built upon large biogenic reefs. These types of corals 

and associated epibenthic communities are the focus of this chapter on pinnacles and low-relief 

features.

The Pinnacle Trend is an approximately 64 x 16 mi (103 x 26 km) area in water depths 

ranging from approximately 200 to 650 ft (60 to 200 m). It is in the northeastern portion of the CPA 

at the outer edge of the Mississippi-Alabama shelf between the Mississippi River and De Soto 

Canyon (Figures 2-4 and 4-9). Outside of the Pinnacle Trend area, low-relief, live bottom 

epibenthic communities occur in isolated locations in shallow waters (<984 ft; 300 m) throughout the 

GOM wherever there exists suitable hard substrate and other physical conditions (e.g., depth, 

turbidity, etc.), allowing for community development. Hard bottom habitats occur throughout the 

GOM but are relatively rare compared with ubiquitous soft bottoms.

Protective Measures for Pinnacle and Low-Relief Features and Associated Communities

Protective measures have been developed over time based on the nature and sensitivity of 

various live bottom habitats and their associated communities, as understood from decades of 

BOEM-funded and other environmental studies. These protections were developed into stipulations 

historically applied to OCS leases in areas with known concentrations of live bottom features. The 

Pinnacle Trend is a specific series of high- and low-relief hard/live bottom features occurring just 

east of the Mississippi River. BOEM has historically and consistently applied the Live Bottom 

(Pinnacle Trend) Stipulation to 74 OCS lease blocks covering this area. As of the approval of the 

Five-Year Program, the Live Bottom (Pinnacle Trend) Stipulation is a required mitigation. The CPA 

blocks directly adjacent to the stipulation blocks are included in a proposed action and some of the 

alternatives; therefore, potential impacts of routine activities and accidental events originating in 
4-94 2018 Gulf of Mexico Supplemental EIS

those adjoining blocks are analyzed here. A full list of the stipulation blocks with required mitigation 

can be found in Appendix D of the 2017-2022 GOM Multisale EIS.

Live bottom habitats are found outside the blocks where the Topographic Features and Live 

Bottom Stipulations have been historically applied. Such habitats are not specifically included in 

those stipulations (now a required mitigation as a result of the Five-Year Program’s Record of 

Decision), but they are still routinely given protections during site-specific NEPA reviews of permitted 

activities, as described in NTL 2009-G39, “Biologically-Sensitive Underwater Features and Areas.” 

That NTL provides information and consolidates guidance to help operators understand BOEM’s 

requirements related to sensitive benthic habitats both within and outside the required mitigation 

blocks. 

Lessees must provide site-specific seafloor survey data and interpretive information 

(including about hard bottom features) with each EP, DOCD, and DPP. Site-specific NEPA reviews 

are conducted on these plans by BOEM’s subject-matter experts on a case-by-case basis to 

determine whether a proposed operation could impact a live bottom feature. If an impact is judged 

likely based on site-specific information derived from BOEM’s studies/databases, other published 

research, geohazard survey data, or another creditable source, the operator may be required to 

distance/relocate the proposed operation or undertake other mitigations to prevent an impact. This 

analysis assumes continuation of the protective measures outlined in NTL 2009-G39, as they are 

routinely applied (when and where appropriate) during all site-specific plan reviews. The Live 

Bottom Stipulation, which historically was applied to individual lease sales at the discretion of the 

decisionmaker and has been consistently applied to the same lease blocks for decades, is now a 

required mitigation as a result of the Five-Year Program’s Record of Decision. The types of potential 

impacts to pinnacle and low-relief feature communities described in this chapter would become more 

likely and more severe without the continued application of these stipulations.

Analysis

This analysis considers the impacts of routine activities, accidental events, and a proposed 

action’s incremental contribution to cumulative impacts on GOM pinnacle and low-relief features and 

their associated benthic communities (or just “feature communities” for short) over a 50-year period. 

This analysis is not exhaustive of all possible impacts of routine activities and accidental events; 

rather, it focuses on those related to a proposed action. A summary of the potential magnitude of 

impact for each of these impact-producing factors is provided in Table 4-14 to help the reader 

quickly identify the level of potential impacts for each relevant impact-producing factor. The 

impact-level definitions and the analyses supporting these conclusions are discussed below. 

Because a catastrophic oil spill is not considered reasonably foreseeable, those potential impacts 

(including long-term recovery) are addressed in the Catastrophic Spill Event Analysis white paper 

(USDOI, BOEM, 2017b). The impact significance criteria and resulting conclusions presented here 

(Table 4-14) focus on the overall functioning, resilience, and ecosystem level importance of live 

bottom pinnacle and low-relief feature communities throughout U.S. waters of the GOM. Postlease, 

site-specific analyses would focus more on the potential localized impacts of individual development 
Description of the Affected Environment and Impact Analysis 4-95

activities (e.g., proposed drilling of a specific well) to individuals, discrete communities, and small 

patches of live bottom habitat. Those analyses would also detail site-specific protective mitigations 

required prior to approval of such activities. Appendix B of the 2017-2022 GOM Multisale EIS 

provides detail on some of the potential site-specific mitigations that could be applied as necessary.

The primary relevant, reasonably foreseeable impacts of routine activities and accidental 

events to live bottom Pinnacle Trend and low-relief features and associated communities described 

in this chapter can be grouped into the following three general categories:

(1) bottom-disturbing activities (routine and accidental);

(2) drilling-related sediment and waste discharges (routine and accidental); and

(3) oil spills (accidental).

These impacts are analyzed in detail under the “Routine Activities” and “Accidental Events” 

sections in Chapter 4.6 of the 2017-2022 GOM Multisale EIS and are summarized below. 

Cumulative impacts were also considered in two steps: cumulative impacts resulting from OCS 

oil- and gas-related activities and impacts resulting from non-OCS oil- and gas-related activities. 

Some impact-producing factors relevant to live bottom communities (such as anthropogenic sounds) 

are analyzed in detail in Chapter 4.7 (“Fishes and Invertebrate Resources”) of the 2017-2022 GOM

Multisale EIS. Some theoretically possible impact-producing factors were not carried forward for full 

analysis in the 2017-2022 GOM Multisale EIS because any potential effects were judged to be either 

not reasonably foreseeable or having such a miniscule impact that they would not rise to the level of 

negligible impact. Refer to Chapter 4.6.2 of the 2017-2022 GOM Multisale EIS for more detail on 

these analyses.

Impact-Level Definitions

For this analysis, the definitions below were used to categorize impacts to pinnacles and 

low-relief features and associated communities.

• Negligible – Impacts to pinnacle and low-relief feature communities are largely 

undetectable. There is some potential for even undetectable impacts to cause 

slight changes to a local community’s species abundance and composition, 

community structure, and/or ecological functioning, but any such changes would 

be spatially localized, short term in duration, and would not alter the overall 

status of GOM pinnacle and low-relief feature communities.

• Minor – Impacts to pinnacle and low-relief feature communities are detectable 

but cannot be distinguished from natural variation. Such impacts could result in 

noticeable changes to a local community’s species abundance and composition, 

community structure, and/or ecological functioning, but any such changes would 

be spatially localized, short term in duration, and would not alter the overall 

status of GOM pinnacle and low-relief feature communities.
4-96 2018 Gulf of Mexico Supplemental EIS

• Moderate – Impacts to pinnacle and low-relief feature communities detectably 

cause substantial, population-level changes in species composition, community 

structure, and/or ecological functioning. These impacts would be expected to be 

spatially extensive, but they are expected to only temporarily alter the overall 

status of GOM pinnacle and low-relief feature communities such that long-term 

recovery to pre-impact levels is likely.

• Major – Impacts to pinnacle and low-relief feature communities detectably cause 

substantial, population-level changes in species composition, community 

structure, and/or ecological functioning. These impacts would be expected to be 

spatially extensive and to noticeably alter the overall status of GOM pinnacle and 

low-relief feature communities such that long-term recovery to pre-impact levels 

is unlikely.

Table 4-14. Pinnacles and Low-Relief Features and Associated Communities Impact-Producing Factors

That Are Reasonably Foreseeable. 

Pinnacles and

Low-Relief Features Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Bottom-Disturbing Activities and Drilling-Related Sediment and Waste Discharges

With Mitigation Negligible Negligible Negligible Negligible None

Without Mitigation

Minor to Minor to Negligible to Negligible to None

Major Moderate Minor Minor

Accidental Impacts 

Bottom-Disturbing Activities and Drilling-Related Sediment and Operational Waste Discharges

With Mitigation Negligible to Negligible to Negligible Negligible None

Minor Minor

Without Mitigation

Minor to Minor to Negligible to Negligible to None

Major Moderate Minor Minor

Oil Spills

With Mitigation Negligible to Negligible to Negligible Negligible None

Minor Minor

Without Mitigation

Minor to Minor to Negligible to Negligible to None

Major Moderate Minor Minor

Cumulative Impacts

Incremental 

Contribution2 

Negligible to Negligible to Negligible Negligible None Minor Minor

OCS Oil and Gas3 Negligible to

Minor

Non-OCS Oil and Gas4 Minor to

Major
Description of the Affected Environment and Impact Analysis 4-97

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.6.2 of the 2017-2022 GOM Multisale EIS. 2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

The impact-producing factors for pinnacles and low-relief live bottom features and associated 

communities can be grouped into three main categories: (1) bottom-disturbing activities; 

(2) drilling-related sediment and waste discharges; and (3) oil spills. These impact-producing factors 

have the potential to damage individual pinnacle and low-relief features and associated benthic 

communities if insufficiently distanced or otherwise mitigated. The Live Bottom Stipulation (which is 

a required mitigation as a result of the Five-Year Program’s Record of Decision), along with 

site-specific reviews of permit applications and associated distancing requirements, would mitigate 

potential impacts to the communities as a result of both routine activities and accidental 

disturbances. At the broad geographic and temporal scope of this analysis, and assuming 

adherence to all expected lease stipulations and typically applied regulations and mitigations, routine 

activities are expected to have largely localized and temporary effects. Although accidental events 

have the potential to cause severe damage to specific pinnacle and low-relief feature communities, 

the number of such events is expected to be very small. Therefore, at the regional, population-level 

scope of this analysis, the incremental contribution of impacts from reasonably foreseeable routine 

activities and accidental activities to the overall cumulative impacts is expected to be negligible to 

minor. Proposed OCS oil- and gas-related activities would also contribute incrementally to the 

overall OCS oil- and gas-related and non-OCS oil- and gas-related cumulative effects experienced 

by pinnacle and low-relief feature habitats. Under Alternative E, the potential for impacts to pinnacle 

and low-relief feature communities related to a cancelled lease sale would be none because new 

impacts would be avoided entirely. Cumulative impacts of current and past activities (i.e., OCS

oil- and gas-related and non-OCS oil- and gas-related), however, would continue to occur under this

alternative. The OCS oil- and gas-related cumulative impacts to pinnacle and low-relief feature 

communities are estimated to be negligible to minor. A full analysis of pinnacles and low-relief 

features can be found in Chapter 4.6.2 of the 2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

Overall, given adherence to the Live Bottom (Pinnacle Trend) Stipulation (which is a required 

mitigation as a result of the Five-Year Program’s Record of Decision), reasonably foreseeable 

impacts to pinnacle and low-relief feature communities from routine activities, accidental events, and 

the cumulative impacts for any of the action alternatives (i.e., Alternatives A-D) are expected to be 

negligible or negligible to minor, depending on the alternative. Alternative B would not 

fundamentally alter the overall conclusion reached under Alternative A for incremental impacts from 

a lease sale. Many OCS lease blocks near the features are already leased, and non-OCS oil- and 

gas-related activities are not expected to decrease. Under Alternative C, BOEM could hold a lease 
4-98 2018 Gulf of Mexico Supplemental EIS

sale excluding the CPA/EPA available unleased blocks and would only offer all available unleased 

blocks in the WPA. Alternative C would not fundamentally alter the conclusions reached under 

Alternative A or B, but it would reduce the potential impacts of a proposed lease sale of the available 

unleased CPA/EPA blocks, including known high concentrations of pinnacle and low-relief feature 

communities in the Pinnacle Trend blocks and other portions of the northeastern CPA (Figure 4-9). 

Under Alternative D, BOEM could hold a lease sale excluding leasing on any and/or all blocks 

subject to the Topographic Features, Live Bottom (Pinnacle Trend), and Blocks South of Baldwin 

County, Alabama, Stipulations. Known pinnacle and low-relief features in the Pinnacle Trend area 

would be further protected by the increased distancing of OCS oil- and gas-related activities, 

reducing the probability of impacts. An accidental spill may still reach a feature, but it is expected 

that the increased distance would provide more dispersal time as the spill travels the additional 

distance across unleased blocks. Under Alternative E, a proposed lease sale would be cancelled. 

Therefore, the potential for new incremental impacts would be none because new OCS oil- and 

gas-related impacts to pinnacle and low-relief feature communities related to a cancelled lease sale 

would be avoided entirely. Cumulative impacts of current and past activities (i.e., OCS oil- and 

gas-related and non-OCS oil- and gas-related), however, would continue to occur under this 

alternative.

Incomplete or Unavailable Information

BOEM recognizes that there is incomplete or unavailable information related to GOM live 

bottom habitats in general and specifically in relation to routine activities, accidental events, and 

cumulative impacts for OCS oil- and gas-related activities and cumulative non-OCS oil- and 

gas-related activities. However, the information that is known is adequate to come to a 

determination with respect to reasonably foreseeable impact-producing factors associated with a 

proposed action.

Research in offshore marine systems is logistically complex and requires substantial 

resources to conduct. The total amount of research on live bottom habitats has therefore been 

limited, although BOEM and its predecessor agencies have funded numerous studies over the past 

40 years. An example of incomplete knowledge about this resource would be that the exact 

distribution of GOM live bottom habitats at any given time is not perfectly understood. This is due in 

part to limits on data collection but also due to the frequent burial and exposure of low-relief hard 

bottoms. To help address this knowledge gap, BOEM requires operators to provide detailed, 

updated, site-specific survey information about potential live bottom habitats; this information is 

reviewed by subject-matter experts prior to approval of individual proposed activities, and 

appropriate protective mitigations are applied where appropriate.

Although BOEM has acquired and applies a large amount of knowledge about possible 

impacts to live bottom habitats, a perfect understanding of all conceivable impacts is unattainable. 

For example, only recently did a study (Silva et al., 2015) provide compelling evidence that the 

mixing of a surface oil/dispersant mixture to the depths of the Pinnacle Trend live bottom features 

can actually occur, given a very unusual combination of conditions, and could then have a localized 
Description of the Affected Environment and Impact Analysis 4-99

impact. Given the geographic and temporal scope of a proposed action, it is believed that even 

impacts resulting from that particular scenario would still only have a slight impact on the overall 

status of GOM pinnacle and low-relief feature communities. Moreover, the amount of oil/dispersant 

mixture in that catastrophic situation greatly exceeded the amounts considered in the “Accidental 

Events” analysis in Chapter 4.6.2 of the 2017-2022 GOM Multisale EIS. However, the example 

demonstrates the point that the body of literature supporting impact analysis is still growing and 

requires continual review by BOEM.

Known information about potential impacts of a theoretical catastrophic spill is detailed in the 

Catastrophic Spill Events Analysis white paper (USDOI, BOEM, 2017b), and further information was 

made available with the publication of Trustees’ PDARP/PEIS in 2016 (Deepwater Horizon Natural 

Resource Damage Assessment Trustees, 2016). The content of that report was reviewed as part of 

this analysis. Some information related to impacts specific to the Deepwater Horizon explosion, oil, 

spill, and response, such as long-term monitoring results, is still incomplete or unavailable. 

Impending reports are not expected to reveal additional significant effects that would alter the overall 

conclusions about reasonably foreseeable impact-producing factors associated with a proposed 

action. Therefore, BOEM has determined that it is not possible to obtain this information within the 

timeframe contemplated for the NEPA analysis in this Supplemental EIS, regardless of the cost or 

resources needed.

BOEM will continue to analyze and support collection and analysis of the best available 

scientific information related to live bottom habitats. BOEM used reasonably accepted scientific 

methodologies to extrapolate from existing information in completing this analysis and formulating 

the conclusions presented here. BOEM has determined that the incomplete information is not 

essential to a reasoned choice among alternatives.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including literature from relevant peer-reviewed 

journals and reports) were examined to assess recent information regarding Pinnacles and low-relief 

features and associated communities that may be pertinent to a proposed action. No new 

information that would add to the analyses or change the conclusions was discovered since 

publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for Pinnacles and low-relief features presented in the 

2017-2022 GOM Multisale EIS, with the understanding that no new relevant information on 

Pinnacles and low-relief features and associated communities has been published since the 

publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information was discovered 

that would alter the impact conclusion for Pinnacles and low-relief features and associated 

communities presented in that document, and the analysis and potential impacts detailed in the 

2017-2022 GOM Multisale EIS still apply for the remaining proposed GOM lease sales in the 

Five-Year Program. 
4-100 2018 Gulf of Mexico Supplemental EIS

4.7 FISHES AND INVERTEBRATE RESOURCES

Summary

BOEM has reexamined the analysis for fish and invertebrate resources presented in the 

2017-2022 GOM Multisale EIS based on the additional information presented below. No new 

information was discovered that would alter the impact conclusion for fish and invertebrate resources

presented in the 2017-2022 GOM Multisale EIS. Further, the analysis and potential impacts detailed 

in that document still apply for the remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of fish and invertebrate resources, along with the full analyses of the 

potential impacts of routine activities, accidental events, and cumulative impacts associated with the 

proposed action are presented in Chapter 4.7 of the 2017-2022 GOM Multisale EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the 

2017-2022 GOM Multisale EIS. Any new information that has become available since that 

document was published is presented below.

Introduction

Fish and invertebrate resources of the GOM comprise a large and diverse group of species 

(Felder et al., 2009). The distribution of fishes and invertebrates varies widely, and species may be 

associated with different habitats at various life stages. This analysis highlights behaviors and 

habitat preferences, but it does not attempt to provide a comprehensive list of all potentially 

impacted fauna. For purposes of this analysis, habitat preferences can be divided into three broad 

categories: estuarine; coastal; and oceanic. Exposure to specific impact-producing factors 

generated by OCS oil- and gas-related routine activities and accidental events can vary among 

these categories. Coastal and oceanic resources are further broken into benthic and pelagic zones 

to address differences in potential exposure to impact-producing factors within a given habitat 

category. Ichthyoplankton bridges all three categories. Egg and larval stages of most fishes and 

invertebrates can be found in the upper layer of the water column, exposing these species’ early life 

stages to similar impact-producing factors. For these reasons, the description of the affected 

environment for fish and invertebrate resources is broken into estuarine, coastal, and oceanic 

habitats, with ichthyoplankton being treated separately due to the potentially broader distribution of 

egg and larval lifestages across these habitats. A detailed description of the affected environment 

for fish and invertebrate resources can be found in in Chapter 4.7.1 of the 2017-2022 GOM Multisale 

EIS, along with a brief discussion of the federally managed species.

Analysis

This chapter provides a summary of the information detailed in the 2017-2022 GOM 

Multisale EIS regarding the impact-producing factors from routine activities, accidental events, and 

cumulative impacts described in Chapter 3 and their potential effects on fish and invertebrate 

resources that would potentially result from a proposed action or the alternatives. This analysis 

applies to all considered alternatives. While the WPA is a smaller area with less projected activity 

than is proposed for the CPA/EPA (refer to Chapter 3), the distribution of fishes and invertebrate 
Description of the Affected Environment and Impact Analysis 4-101

species is nonrandom; species are associated with habitat preferences. However, within the Gulf of 

Mexico, the distribution of species may generally be considered even throughout their range of 

habitat within the planning areas. As such, the potential for impacts to populations is independent of 

the planning area(s) analyzed. Differences in the specific populations potentially exposed to 

impact-producing factors and the potential impacts may be more easily estimated as specific sites 

and activities become known. Therefore, because of the diversity and distribution of species in the 

Area of Interest, the level of impacts would be the same for Alternatives A, B, C, and D. However, 

Alternative E would have no impacts as a proposed action would not be implemented; therefore, the 

only impacts would be those associated with the continuing effects from past lease sales and 

non-OCS oil- and gas-related activities.

Preliminary analysis of the routine OCS oil- and gas-related activities and reasonably 

foreseeable accidental events identified eight impact-producing factors with the potential to affect 

marine fishes and invertebrates and/or their habitat. Many OCS oil- and gas-related activities affect 

the environment similarly. For example, vessel traffic, exploratory drilling, geophysical activities, and 

offshore construction all produce sound. The impact-producing factor, “anthropogenic sound,” was 

analyzed taking all sound-producing OCS oil- and gas-related activities into consideration. The 

following are impact-producing factors that were considered and analyzed in this resource analysis:

• anthropogenic sound (Chapter 3.3.2.7 of the 2017-2022 GOM Multisale EIS);

• bottom-disturbing activity (Chapter 3.1.3.3.2 of the 2017-2022 GOM Multisale 

EIS);

• habitat modification; and

• oil spills (Chapter 3.2.2).

Two of the eight impact-producing factors that were considered for fishes and invertebrate 

resources were determined to be insignificant under all reasonably foreseeable circumstances due 

to the limited exposure and/or response expected for fish and invertebrate resources and are, 

therefore, not analyzed in this chapter. These impact-producing factors are entrainment (Chapter 

3.1.5.1.6 of the 2017-2022 GOM Multisale EIS) and offshore lighting (Chapter 3.1.3.4.3 of the 

2017-2022 GOM Multisale EIS). A Joint Industry Biological Baseline Study was completed for 

USEPA Region 6 in June 2009 (LGL Ecological Research Associates, Inc., 2009), and an industrywide cooling water intake structure entrainment monitoring study, approved by USEPA Region 6,

was completed in 2014 (Continental Shelf Associates, Inc. and LGL Ecological Research 

Associates, Inc., 2014). The results of these two studies support BOEM’s finding that entrainment is 

insignificant as an impact-producing factor for the purpose of this analysis. Analyses of two 

additional impact-producing factors that could potentially impact resources ecologically important to 

fishes and invertebrates were addressed in earlier chapters. Discussions of onshore construction 

and manufacturing (Chapters 3.1.2.2 and 4.3, “Coastal Habitats”) and regulated discharges 

(Chapter 3.1.5.1 of the 2017-2022 GOM Multisale EIS and Chapter 4.2 of this Supplemental EIS, 
4-102 2018 Gulf of Mexico Supplemental EIS

“Water Quality”) were found to sufficiently address the potential for adverse impacts to fish and 

invertebrate habitats and are not duplicated in this chapter.

Analysis of potential impacts considered the estimated scale of source activities and used 

the best available science to evaluate how specific impact-producing factors could affect resources 

within the expected environment. Cumulative impacts (discussed in detail in Chapter 4.7.3 of the 

2017-2011 GOM Multisale EIS) were analyzed for OCS oil- and gas-related activities and for other 

sources that could affect fishes and invertebrates (e.g., coastal development, commercial shipping, 

fisheries, and environmental). Because of the diversity of fishes and invertebrates, detailed criteria 

for potential impact levels are not reasonable.

Though two protected fish species (Gulf sturgeon [Acipenser oxyrhynchus desotoi] and 

smalltooth sawfish [Pristis pectinata]) are found near the Area of Interest, they inhabit and have 

critical habitat in onshore waters (i.e., shallow waters near the shoreline). A third protected species, 

Nassau grouper (Epinephalus striatus), is a transient or rarely occurring species in the Area of 

Interest. These species are not considered to be impacted by a proposed action because they are 

found away from activities that could cause an impact. The impact-level definitions and analyses 

supporting these conclusions are discussed below.

Impact-Level Definitions

For this analysis, the potential impact-level criteria can be described in terms of populationlevel effects.

• Negligible – localized and temporary impacts that are expected to be 

indistinguishable from natural variations in population distribution and 

abundance.

• Minor – localized and temporary impacts that are expected to be 

indistinguishable from natural variations in population distribution and 

abundance. Community-level variations may be locally detectable, such as 

species mix and relative abundance following the removal of OCS oil- and 

gas-related infrastructure.

• Moderate – Impacts would be expected to exceed natural variations in 

population abundance or distribution, but not result in a long-term decline.

• Major – Impacts would be expected to exceed natural variations and inherently 

result in a long-term decline in populations.

The impact-producing factors analyzed and the impact-level conclusions reached from the 

analysis in this chapter are presented in Table 4-15 to help the reader quickly identify the level of 

potential impacts for fishes and invertebrate resources.
Description of the Affected Environment and Impact Analysis 4-103

Table 4-15. Fish and Invertebrate Resources Impact-Producing Factors That Are Reasonably 

Foreseeable. 

Fish and 

Invertebrate 

Resources

Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Anthropogenic 

Sound Minor Minor Minor Minor None

Bottom-Disturbing 

Activity Negligible Negligible Negligible Negligible None

Habitat 

Modification

Negligible to Negligible to Negligible to Negligible to None

Minor Minor Minor Minor

Accidental Impacts

Oil Spills Negligible Negligible Negligible Negligible None

Cumulative Impacts

Incremental 

Contribution2 Minor Minor Minor Minor None

OCS Oil and Gas3

Anthropogenic 

Sound Minor

Bottom-Disturbing 

Activity Negligible

Habitat 

Modification

Negligible to

Moderate

Non-OCS Oil and Gas4

Anthropogenic 

Sound Moderate

Fisheries Negligible to

Moderate

Habitat 

Modification Minor

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.7 of the 2012-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

The distribution of fishes and invertebrates varies widely and species may be associated with 

different habitats at various life stages, as discussed further in Chapter 4.7 of the 2017-2022 GOM 

Multisale EIS. The impact-producing factors affecting these resources are anthropogenic sound, 

bottom-disturbing activities, habitat modification, and accidental oil spills. The impacts from routine 
4-104 2018 Gulf of Mexico Supplemental EIS

activities, excluding infrastructure emplacement, would be expected to be negligible or minor due 

to short-term localized effects. The installation of OCS oil- and gas-related infrastructure constitutes 

a long-term modification of the local habitat and is hypothesized to have resulted over the life of the 

program in moderate changes in the distribution of some species. Although this effect is not 

necessarily adverse and infrastructure is expected to be decommissioned and sites restored to 

natural habitat, the cumulative impact over the life of the OCS Program is spatiotemporally 

extensive. Accidental spills have been historically low-probability events and are typically small in 

size. The expected impact to fishes and invertebrate resources from accidental oil spills is 

negligible. Commercial and recreational fishing are expected to have the greatest direct effect on 

fishes and invertebrate resources, resulting in impact levels ranging from negligible for most

species to potentially moderate for some targeted species (e.g., hogfish spp., gray triggerfish 

[Balistes capriscus], and greater amber jack [Seriola dumerili]). The analysis of routine activities and 

accidental events indicates that the incremental contribution to the overall cumulative impacts on 

fishes and invertebrate resources as a result of a single proposed lease sale would be minor. 

Under Alternative E, the expected impacts on fish and invertebrate resources would be none. 

Cumulative impacts of current and past activities (i.e., OCS oil- and gas-related and non-OCS 

oil- and gas-related), however, would continue to occur under this alternative. A full analysis of fish 

and invertebrate resources can be found in Chapter 4.7 of the 2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

With respect to fishes and invertebrate resources, the effects associated with the selection of 

any of the proposed action alternatives (i.e., Alternatives A-D) would be equal because of the 

diversity and distribution of fish and invertebrate species throughout the potential area of interest. 

The analyses assume a nonrandom distribution of species (i.e., distribution is associated with habitat 

preference and habitat availability) and consider impacts to fishes and invertebrate resources 

occurring in a wide range of habitats across all planning areas. While the WPA is a smaller area 

with less projected activity than is proposed for the CPA/EPA (refer to Chapter 3), the distribution of 

fishes and invertebrate species is nonrandom; species are associated with habitat preferences. 

However, within the Gulf of Mexico, the distribution of species may generally be considered even 

throughout their range of habitat within the planning areas. As such, the potential for impacts to 

populations is independent of the planning area(s) analyzed. Differences in the specific populations 

potentially exposed to impact-producing factors and the potential impacts may be more easily 

estimated as specific sites and as activities become known. Therefore, at a planning area scale, it is 

expected that a similar mix of species would be exposed to the analyzed impact-producing factors, 

regardless of the specific action alternative selected. The activities proposed under Alternatives A-D 

would directly impact fishes and invertebrate resources within the GOM and would contribute 

incrementally to the cumulative effects on these resources. Therefore, the analysis of routine OCS 

oil- and gas-related activities, accidental events, and the cumulative impacts of OCS oil- and 

gas-related and non-OCS oil- and gas-related activities indicates that the expected overall impact to 

fishes and invertebrate resources, depending upon the impact-producing factor and the affected 

species, would range from negligible to moderate for the period analyzed. For example, muds and 

cuttings discharged at the surface for a well drilled at a water depth of 5,000 ft (1,524 m) would have 
Description of the Affected Environment and Impact Analysis 4-105

a negligible impact on coastal species, such as menhaden, whereas a small spill in coastal waters 

and subsequent response activities could disrupt a spawning event or temporarily displace coastal 

fishes from the affected area (minor). Moderate impacts would only be expected if impact-producing 

factors affected habitat or populations to an extent that would be expected to exceed natural 

variations in population abundance or distribution but not result in a long-term decline. Under 

Alternative E, the incremental impacts on fishes and invertebrate resources within the Gulf of Mexico 

would be none; however, impacts would continue from ongoing OCS oil- and gas-related activity.

Incomplete or Unavailable Information

BOEM identified incomplete or unavailable information related to impacts to fishes and 

invertebrate resources resulting from OCS oil- and gas-related activities and non-OCS oil- and gasrelated activities in the GOM. Anthropogenic sound and habitat modification directly or indirectly 

affect large areas of the GOM and potentially impact thousands of species. However, the response 

of individuals, groups of conspecifics (members of the same species), and communities are highly 

variable and inconsistent. In addition, BOEM recognizes that there is incomplete information with 

respect to potential long-term effects resulting from exposure to spilled oil. Although additional 

information on these impact-producing factors may be relevant to the evaluation of impacts to fishes 

and invertebrate resources, BOEM has determined that the incomplete information is not essential to 

a reasoned choice among alternatives. Analyses of routine activities, accidental events, and 

cumulative impacts drew upon the most current and best available research to assess the potential 

effects on many species and habitats. The findings collectively indicate that impacts are likely, but 

limited, and are not expected to induce a population-level response. BOEM recognizes the potential 

that populations with spatially limited distributions or increased sensitivity to an impact-producing 

factor may be more severely impacted than current research suggests. However, sufficient data to 

conduct a thorough assessment of all potentially affected species are not available or obtainable 

within the timeline contemplated in the NEPA analysis of this Supplemental EIS. BOEM used the 

best available science to determine the range of reasonably foreseeable impacts and applied 

accepted scientific methodologies to integrate existing information and extrapolate potential 

outcomes in completing this analysis and formulating the conclusions presented here.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including Elsevier, PLoS ONE, Taylor and Francis 

Online, NOAA’s NCCOS Publications Explorer, and Wiley Online Library) were examined to assess 

recent information regarding fish and invertebrate resources that may be pertinent to a proposed 

action. No new information that would add to the analyses or change the conclusions was 

discovered since publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for fish and invertebrate resources presented in the 

2017-2022 GOM Multisale EIS, with the understanding that no new information essential to an 

analysis of fish and invertebrate resources has been published since the publication of the 
4-106 2018 Gulf of Mexico Supplemental EIS

2017-2022 GOM Multisale EIS. Therefore, no new information was discovered that would alter the 

impact conclusion for fish and invertebrate resources presented in that document, and the analysis 

and potential impacts detailed in the 2017-2022 GOM Multisale EIS still apply for the remaining 

proposed GOM lease sales in the Five-Year Program. 

4.8 BIRDS

Summary

BOEM has reexamined the analysis for birds presented in the 2017-2022 GOM Multisale EIS 

based on the additional information presented below. No new information was discovered that 

would alter the impact conclusion for birds presented in the 2017-2022 GOM Multisale EIS. Further, 

the analysis and potential impacts detailed in that document still apply for the remaining proposed 

GOM lease sales in the Five-Year Program. 

A detailed description of birds, along with the full analyses of the potential impacts of routine 

activities, accidental events, and cumulative impacts associated with a proposed action are 

presented in Chapter 4.8 of the 2017-2022 GOM Multisale EIS. The following information is a 

summary of the resource description and impact analysis incorporated from the 2017-2022 GOM 

Multisale EIS.

Introduction

This description of birds focuses on the factors that control the relative vulnerability of 

different bird groups to impacts. Passerines, or songbirds, represent many of the breeding and 

wintering birds within the Gulf Coast States. They are only found offshore when migrating across 

the Gulf of Mexico, and they cannot stop and rest or feed on the water. Some species of birds 

(some seabirds) live primarily offshore except when breeding and, therefore, are rarely observed in 

the nearshore environment. The remaining species are found within coastal and inshore habitats 

and may be more susceptible to potential deleterious effects resulting from OCS oil- and gas-related 

activities since many of these species largely overlap spatially and temporally with OCS oil- and 

gas-related activities because of their abundance or density and due to the potential of oil impacting 

their habitat or food resources.

Analysis

This chapter provides a summary of the information detailed in the 2017-2022 GOM 

Multisale EIS regarding the impact-producing factors from the routine activities, accidental events, 

and cumulative impacts described in Chapter 3 and their potential effects on birds that could 

potentially be impacted by a proposed action or the alternatives. This analysis would apply to all 

alternatives considered; however, the level of impacts would be different for each alternative, as 

discussed below. 

The approach of the analysis is to focus on the potential impact-producing factors from OCS 

oil- and gas-related routine activities (i.e., exploration, development, production, and 
Description of the Affected Environment and Impact Analysis 4-107

decommissioning), as well as accidental events and cumulative impacts, and to define the impact 

levels for each impact-producing factor. The impact-producing factors considered and analyzed 

include discharges and wastes, noise, platform severance with explosives, geophysical surveys with 

airguns, platform presence and lighting, emergency air emissions, platform or pipeline oil spills, spill 

response, oil- and gas-related activities in State waters, the hypoxic “dead zone” of the Mississippi 

River, net coastal wetland gain or loss, urbanization, a large tanker spill, military activities, 

recreation, boat traffic, impacts on bird habitat, collisions with vehicles and buildings, predation by 

domestic cats, commercial fishing, climate change, and wetland subsidence. The potential 

magnitude of impact for each of these impact producing factors is provided in Table 4-16 to help the 

reader quickly identify the level of potential impacts for each impact-producing factor. The 

impact-level definitions and the analyses supporting these conclusions are discussed below.

Impact-producing factors considered but not analyzed include obstruction lighting, which is 

under the jurisdiction of USCG. Other impact-producing factors that were not analyzed because 

they do not apply to birds include geological ancillary activities, all onshore infrastructure 

emplacement and presence, offshore platform emplacement, other commissioning activities, and 

onshore waste disposal.

Seven species found in the area of interest are listed under the ESA, and BOEM has initiated 

formal consultation with FWS for those species. Those species have life histories that are similar to 

those of the birds covered in this chapter, but the cumulative impact could be greater. BOEM 

recognizes this, consults on these species, and requires mitigations that would decrease the 

potential for greater impacts due to small population size or limited distribution. For more 

information on the listed bird species, refer to Chapter 4.9.4 of this Supplemental EIS and Chapter 

4.9.4 of the 2017-2022 GOM Multisale EIS.

Impact-Level Definitions

Two concepts important in the impact-level definitions below are populations and population 

sizes. In ecology, a population is often defined as a group of individuals with similar genes (i.e., 

species and subspecies). Such a population lives in one or more natural geographic areas where its 

habitats are located. Human-made areas (e.g., the planning areas) are also important to the 

analysis. Natural areas overlap with the planning areas. Bird species described in this chapter are 

considered to have large populations and to be widely distributed Flock size and population, 

mentioned below in the impact-level definitions, have ranges of impacts that can vary by bird 

species. Examples of flock sizes and population sizes are given in the “Description of the 

Environment” section of Chapter 4.8 of the 2017-2022 GOM Multisale EIS. Abundance, as used in 

this chapter, means the number or biomass (total weight) of a particular species in a general area 

(this definition is taken from Krebs, 2009). Chronic, as used in this chapter, means of indefinitely 

high frequency or of indefinitely long duration.
4-108 2018 Gulf of Mexico Supplemental EIS

The impact-level definitions for birds are as follows:

• Negligible – Impacts would not affect a substantial abundance of birds. Impacts 

would especially not affect species with low abundances prior to impacts. 

Estimates of continued population viability, including predicted annual rates of 

recruitment or survival, would not change. Any impacts would be acute and 

reversible. Further, no injury to or mortality of a small number of individuals or a 

small flock would occur.

• Minor – Impacts would not affect a substantial abundance of birds. Impacts 

would especially not affect species with low abundances prior to impacts. 

Estimates of continued population viability, including predicted annual rates of 

recruitment or survival, would not change. Additionally, one or both of the two 

following conditions must be met: (1) small numbers of individuals or small flocks 

of birds would experience chronic impact-producing factors and would be 

chronically disturbed or affected, resulting in chronic but reversible behavioral 

changes; and/or (2) one or more incidents would occur where small numbers of 

individuals or small flocks of birds would experience injury or mortality, but with 

no measurable impact on a population.

• Moderate – Impacts would affect a substantial abundance of birds. Estimates of 

continued population viability, including predicted annual rates of recruitment or 

survival, would not change. Additionally, one or both of the two following 

conditions must be met: (1) a large flock of birds (e.g., a shorebird flock of 500 or 

1,000 birds) would experience chronic impact-producing factors and would be 

chronically disturbed or affected, resulting in chronic behavioral changes or 

mortality over time; and/or (2) one or more incidents would occur where 

substantial numbers of individuals, including large flocks, would experience 

chronic behavior changes or mortality that would affect a large flock, but with no 

measurable impact on a population.

• Major – Impacts would affect a substantial abundance of birds. Estimates of 

continued population viability, including predicted annual rates of recruitment or 

survival, would change. Additionally, one or both of the two following conditions 

must be met: (1) at least one large population of birds would have a reduction in 

the estimates of continued population viability, including predicted annual rates of 

mortality, recruitment or survival, some or all of which would seriously decline 

(causing sublethal impacts to be irreversible); and/or (2) one or more incidents 

would occur where at least one large population would experience chronic 

behavior changes or mortality that would affect a large population and with 

measurable impact on a population.
Description of the Affected Environment and Impact Analysis 4-109

Table 4-16. Birds Impact-Producing Factors That Are Reasonably Foreseeable.

Birds Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Impacts

Discharges and 

Wastes Negligible Negligible Negligible Negligible None

OCS Oil- and GasRelated Noise and 

Disturbance

Negligible Negligible Negligible Negligible None

Platform Severance 

and Rigs-to-Reefs Minor Minor Minor Minor None

Geophysical Surveys 

with Airguns Minor Minor Minor Minor None

Platform Presence 

and Lighting Minor Minor Minor Minor None

Accidental Impacts

Oil Spills Moderate Moderate Moderate Moderate None

Oil-Spill Response Minor Minor Minor Minor None

Emergency Air 

Emissions Minor Minor Minor Minor None

Cumulative Impacts

Incremental 

Contribution2 Moderate Moderate Moderate Moderate None

OCS Oil- and Gas3 Moderate

Non-OCS Oil- and 

Gas4 Major

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.8 of the 2017-2022 GOM Multisale EIS. Moderate impact levels could be possible, 

only if a large oil spill were to occur.

2 This impact level is the incremental contribution of a single proposed lease sale to all cumulative 

impacts in the GOM.

3 This impact level is the cumulative impacts of all past, present, and reasonably forseeable OCS oil- and 

gas-related activities in the GOM.

4 This impact level is the cumulative impacts of all past, present, and reasonably foreseeable activities in 

the GOM.

The affected species of birds include both terrestrial songbirds and many groups of 

waterbirds. Routine impacts to coastal, marine, and migratory birds that were considered include 

routine discharges and wastes, noise, platform severance with explosives (barotrauma), geophysical 

surveys with airguns, platform presence and lighting, construction of OCS oil- and gas-related 

onshore facilities, and pipeline landfalls. The impacts to birds from routine OCS oil-and gas-related 

activities are similar wherever they may occur in the GOM, and all are considered negligible to 

minor. Negligible to minor impacts would not affect a substantial number of birds. Any impacts 

would be acute and reversible. Further, no injury to or mortality of a small number of individuals or a 

small flock would occur. Accidental impacts to birds are caused by oil spills, spill cleanup activities, 

and emergency air emissions. Seabirds may not always experience the greatest impacts from a spill 
4-110 2018 Gulf of Mexico Supplemental EIS

but may take longer for populations to recover because of their unique population ecology 

(demography). Some species of seabirds, such as gulls, have larger clutches (laughing gulls usually 

have 3 eggs per clutch, except in the tropics) and may recover quite quickly. However, many 

species of seabirds can have a clutch size of just one egg, relatively long life spans, and often have 

delayed age at first breeding. Because of the latter case, impacts on seabirds from overall 

accidental events would be expected to be moderate. Impacts from overall accidental events on 

other waterbirds farther inshore would also be expected to be moderate because of the extensive 

overlap of their distributions with oiled inshore areas and shorelines expected from a large oil spill 

(≥1,000 bbl). Moderate impacts would affect a substantial abundance of birds.

The incremental contribution of a proposed action to the overall cumulative impacts is 

considered moderate, but only because of the potential impacts that could result from a large oil 

spill (≥1,000 bbl). This conclusion is based on the increment of a proposed action compared with all 

cumulative OCS oil- and gas-related and non-OCS oil- and gas-related impacts. Alternative E would 

offer no new lease blocks for exploration and development; therefore, incremental impacts to birds 

would be none. However, there would be continuing impacts associated with the existing oil and 

gas activities from previously permitted activities and previous lease sales. A full analysis of coastal 

and migratory birds can be found in Chapter 4.8 of the 2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

Since Alternative A is regionwide, which includes the WPA, CPA, and EPA portions of the 

proposed lease sale area, it would have more OCS oil- and gas-related activities than the other 

alternatives; therefore, it would have more potential for impacts. Impacts from the other alternatives 

would follow in a graded fashion. However, offshore pelagic seabird habitat is distributed throughout 

the planning areas. Therefore, activities occurring only in specific planning areas pose similar 

potential impacts to offshore pelagic seabird populations as do activities occurring in all planning 

areas. Therefore, because of the diversity and distribution of offshore pelagic seabird species in the 

Area of Interest, the level of impacts would be the same for Alternatives A, B, C, and D. 

Alternative E would offer no new lease blocks for exploration and development; therefore, no 

impacts from a proposed lease sale would occur. However, there would be continuing impacts 

associated with the existing oil and gas activities from previously permitted activities and previous 

lease sales.

Incomplete or Unavailable Information

BOEM has identified incomplete or unavailable information related to impacts on birds 

resulting from OCS oil- and gas-related activities and non-OCS oil- and gas-related activities in the 

GOM. BOEM’s subject-matter experts have used the available scientifically credible evidence 

presented below and applied accepted scientific methodologies to integrate existing information and 

extrapolate potential outcomes in completing this analysis and formulating the conclusions 

presented here.
Description of the Affected Environment and Impact Analysis 4-111

The impact of artificial light along the coast on birds has not been studied,and it is unkown if 

it is relevant to evaluating whether adverse mpacts on the human environment are significant, but it 

is not essential to a reasoned choice of among alternatives. BOEM used available information to fill 

the data gap. Existing information (Longcore and Rich, 2004) shows that outdoor lights at night can 

have both lethal impacts from collisions and sublethal impacts from a variety of mechanisms on 

birds. The impact level of obstruction lighting located on platforms would also need further study. 

The best available information was obtained from a study done by observers on platforms, from a 

model of energy reserves of migratory birds, and from several studies of the effect of light on birds. 

This scientific information presented in the 2017-2022 GOM Multisale EIS was used to conclude that 

platform lighting, in general, has minor impacts. 

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including websites of 5 Federal agencies [i.e., FWS, 

USEPA, USGS, NOAA, and BOEM]; 5 State agencies [i.e., Texas Parks and Wildlife Department; 

Louisiana Department of Wildlife and Fisheries; Mississippi Department of Wildlife, Fisheries, and 

Parks; Alabama Wildlife and Freshwater Fisheries Division; and Florida Fish and Wildlife 

Conservation Commission]; and 5 nonprofit stakeholders (i.e., Sierra Club, National Fish and Wildlife 

Foundation, Nature Conservancy, Barataria-Terrebonne National Estuary Program, and the National 

Audubon Society]) were examined to assess recent information regarding birds that may be 

pertinent to a proposed action. Environmental journal articles were also located online using four 

search engines (i.e., JSTOR, EBSCO, Google Advanced Scholar Search, and Google Advanced 

Book Search). No new information that would add to the analyses or change the conclusions was 

discovered since publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for birds presented in the 2017-2022 GOM Multisale EIS 

with the understanding that no new information on birds has been published since the publication of 

the 2017-2022 GOM Multisale EIS. Therefore, no new information was discovered that would alter 

the impact conclusion for birds presented in that document, and the analysis and potential impacts 

detailed in the 2017-2022 GOM Multisale EIS still apply for the remaining proposed GOM lease 

sales in the Five-Year Program.

4.9 PROTECTED SPECIES

The Endangered Species Act of 1973 (ESA), as amended, establishes a national policy 

designed to protect and conserve threatened and endangered species and the ecosystems upon 

which they depend. In fulfilling these requirements, each agency must use the best scientific and 

commercial data available. The FWS and NMFS share responsibility for implementing the ESA.

The Marine Mammal Protection Act of 1972 (MMPA) prohibits, with certain exceptions, the 

"take" of marine mammals in U.S. waters and by U.S. citizens on the high seas and the importation 
4-112 2018 Gulf of Mexico Supplemental EIS

of marine mammals and marine mammal products into the United States. The NMFS and FWS are 

also responsible for the MMPA.

For the Gulf of Mexico, NMFS is charged with protecting all cetaceans, while manatees are 

under the jurisdiction of FWS. Details on BOEM’s consultations and coordination with NMFS and 

FWS are presented in Chapter 5.2 (“Endangered Species Act”).

Protected species, for the purposes of this Supplemental EIS, include ESA- and 

MMPA-listed species and associated designated critical habitat under the ESA. The species 

considered in this chapter, pursuant to our consultations and coordination, and within Table 4-17 are 

those that could be affected within the Area of Interest and that are subject to the proposed activities 

under the alternatives. For those species not considered further because they are unlikely to be 

affected by the proposed activities, refer to Appendix F of the 2017-2022 GOM Multisale EIS. 

Critical habitats noted within the Area of Interest are shown in Figure 4-10 and are mentioned in this 

chapter, but details on many of these habitats can be found in Chapters 4.3 (“Coastal Habitats”), 

4.5 (“Sargassum and Associated Communities”), and 4.6 (“Live Bottom Habitats”).

Table 4-17. Species within the Gulf of Mexico That Are Protected Under the Endangered Species Act 

and/or the Marine Mammal Protection Act.

Common Name Scientific Name Common Name Scientific Name

Marine Mammals Sea Turtles

Atlantic spotted 

dolphin* Stenella frontalis* Green sea turtle2 Chelonia mydas2

Blainville’s beaked 

whale*

Mesoplodon 

densirostris* Hawksbill sea turtle3 Eretmochelys imbricata3

Bottlenose dolphin* Tursiops truncatus* Kemp’s ridley sea turtle3 Lepidochelys kempii3

Bryde’s whale* Balaenoptera edeni*

Northwest Atlantic 

Ocean loggerhead sea 

turtle2

Caretta caretta2

Clymene dolphin* Stenella clymene* Leatherback sea turtle 

(Atlantic Northwest)3

Dermochelys 

coriacea3

Cuvier’s beaked 

whale* Ziphius cavirostris* Beach Mice

Dwarf sperm whale* Kogia sima* Alabama beach mouse3

Peromyscus 

polionotus 

ammobates3

False killer whale* Pseudorca 

crassidens*

Choctawhatchee beach 

mouse3

Peromyscus 

polionotus allophrys3

Fraser’s dolphin* Lagenodelphis hosei* Perdido Key beach 

mouse3

Peromyscus 

polionotus 

trissyllepsis3

Gervais’ beaked 

whale*

Mesoplodon 

europaeus*

St. Andrew beach 

mouse3

Peromyscus 

polionotus 

peninsularis3

Killer whale* Orcinus orca* Birds

Melon-headed whale* Peponocephala 

electra*

Cape Sable Seaside 

Sparrow3

Ammodramus 

maritimus mirabilis3
Description of the Affected Environment and Impact Analysis 4-113

Pantropical spotted 

dolphin* Stenella attenuate* Mississippi Sandhill Crane3

Grus canadensis 

pulla3

Pygmy killer whale* Feresa attenuata* Piping Plover2 Charadrius melodus2

Pygmy sperm whale* Kogia breviceps* Rufa Red knot2 Calidris canutus rufa2

Risso’s dolphin* Grampus griseus* Roseate Tern2 Sterna dougallii 

dougallii2

Rough-toothed 

dolphin* Steno bredanensis* Whooping Crane3 Grus americana3

Short-finned pilot 

whale*

Globicephala 

macrorhynchus* Wood Stork2 Mycteria americana2

Sperm whale1 Physeter 

macrocephalus1 Corals

Spinner dolphin* Stenella longirostris* Elkhorn coral2 Acropora palmata2

Striped dolphin* Stenella 

coeruleoalba* Staghorn coral2 Acropora cervicornis2

West Indian manatee1 Trichechus manatus1 Boulder star coral2 Orbicella franksi2

Lobed star coral2 Orbicella annularis2

Mountainous star coral2 Orbicella faveolata2

* This species is protected under the Marine Mammal Protection Act (MMPA).

1 This species/subspecies is listed under the Endangered Species Act (ESA) as “endangered” and is 

also protected under the MMPA.

2 This species/subspecies is listed under the ESA as “threatened.”

3 This species/subspecies is listed under the ESA as “endangered.”

The analyses of the reasonably foreseeable potential impacts of routine activities and 

accidental events associated with a proposed action and a proposed action’s incremental 

contribution to the cumulative impacts are presented in the chapters below. The approach of the 

analysis is to focus on the potential impact-producing factors from OCS oil- and gas-related routine 

activities (i.e., exploration, development, and production), as well as accidental events and 

cumulative impacts, and to define impact-levels for each impact-producing factor for protected 

species, as summarized in Table 4-18. The impact-level definitions and the analyses supporting 

these conclusions are discussed below. These impacts are across all action alternatives (i.e., 

Alternatives A, B, C, and D) except for beach mice and protected corals. Beach mice are not found 

in the WPA; therefore, they are not relevant for Alternative B, and the ranges given for potential 

impacts to protected corals are based on whether or not stipulations are placed on leases.
4-114 2018 Gulf of Mexico Supplemental EIS

Figure 4-10. Gulf of Mexico Protected Species’ Critical Habitats.
Description of the Affected Environment and Impact Analysis 4-115

Impact-Level Definitions

As the routine activities, accidental events, and cumulative impacts are considered for 

specific listed species, each is given criteria per level of impact represented below.

• Negligible – An individual or group of animals would be subject to nominal to 

slight measurable impacts. No mortality or injury to any individual would occur, 

and no disruption of behavioral patterns would be expected. The disturbance 

would last only as long as the human-caused stimulus was perceptible to the 

individual or group.

• Minor – An individual or group of animals would be subject to a human-caused 

stimulus and be disturbed, resulting in an acute behavioral change. No mortality 

or injury to an individual or group would occur.

• Moderate – An individual or group of animals would be subject to a humancaused stimulus and be disturbed, resulting in a chronic behavioral change. 

Individuals may be impacted but at levels that do not affect the fitness of the 

population. Some impacts to individual animals may be irreversible.

• Major – An individual or group of animals would be subject to a human-caused 

stimulus, resulting in physical injury or mortality, and would include sufficient 

numbers that the continued viability of the population is diminished, including 

annual rates of recruitment or survival. Impacts would also include permanent 

disruption of behavioral patterns that would affect a species or stock.

The potential magnitude of impact for each of these impact-producing factors is provided in 

Table 4-18 to help the reader quickly identify the level of potential impacts for each impact-producing 

factor.

Table 4-18. Protected Species Impact-Producing Factors That Are Reasonably Foreseeable.

Protected Species Magnitude of Potential Impact1

Impact-Producing 

Factors

Marine 

Mammals Sea Turtles Beach Mice2 Protected Birds

Protected 

Corals3 

Routine Impacts

Geological and 

Geophysical 

Activities

Negligible to Negligible to N/A* N/A N/A

Moderate Moderate

Transportation

(vessel strikes) Negligible Negligible N/A N/A N/A

Discharges

(air and water quality 

degradation)

Negligible Negligible N/A Negligible N/A

Decommissioning 

(explosive 

severance)

Negligible to Negligible to

N/A N/A Negligible Minor Moderate
4-116 2018 Gulf of Mexico Supplemental EIS

Protected Species Magnitude of Potential Impact1

Impact-Producing 

Factors

Marine 

Mammals Sea Turtles Beach Mice2 Protected Birds

Protected 

Corals3 

Noise Negligible to Negligible to N/A Negligible N/A Minor Minor

Drilling and 

Exploration (bottomdisturbing activities)N/A N/A N/A N/A Negligible

Offshore 

Lighting/Platform 

Presence

N/A N/A N/A Negligible N/A

Vessel Operation 

(bottom-disturbing 

activities)

N/A N/A N/A N/A Negligible

Accidental Impacts 

Oil Spills4 Negligible to Negligible to Negligible Negligible to Negligible Moderate Moderate Moderate

Oil-Spill Response 

Activities

Negligible to Negligible to Negligible Negligible to Negligible Minor Minor Minor

Marine Trash and 

Debris Negligible Negligible Negligible Negligible Negligible

Cumulative Impacts

Incremental 

Contribution5 Negligible Negligible Negligible Negligible Negligible

OCS Oil and Gas 6 Negligible to Negligible to Negligible Negligible to Negligible Moderate Moderate Moderate

Non-OCS Oil and 

Gas7

Negligible to Negligible to Negligible to Negligible to Negligible to

Major Major Major Major Major

* N/A represents those impact-producing factors that are not applicable to that protected species group.

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.9 of the 2017-2022 GOM Multisale EIS.

2 Beach mice are not found in the WPA; therefore, they are not likely to be impacted by Alternative B.

3 Ranges for the potential impacts to protected corals are based on whether or not protected stipulations 

are placed on leases.

4 Accidental oil spills are those <10,000 bbl.

5 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

6 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

7 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

For protected coral impact-producing factors, refer to Table 4-13 in Chapter 4.6.1

(“Topographic Features”) since coral impact-producing factors are covered there and would apply to 

protected corals as well. For protected birds impact-producing factors, refer to Table 4-16 in 

Chapter 4.8 (“Birds”) since the impact-producing factors that impact coastal, marine, and migratory 

birds (the listed birds are either found in coastal areas or are migratory and utilize coastal areas as

part of their life history) are covered there. For beach mice, the most relevant impact-producing 
Description of the Affected Environment and Impact Analysis 4-117

factors are those causing harm to the populations by affecting their habitat (i.e., beaches). 

Table 4-10 in Chapter 4.3.2 (“Coastal Barrier Beaches and Associated Dunes”) covers the 

impact-producing factors that affect beaches and dunes, and information on impacts to beach 

mouse habitat that can be found there.

BOEM understands that mitigations greatly reduce the likelihood of an impact-producing 

factor, but mitigations do not guarantee that a protected species would not be impacted. There is a 

very low probability that a protected species may not be sighted despite all of the mitigative 

precautions taken to reduce impact. Unlikely scenarios such as these may cause major impacts to a 

protected species with a very low population because some impact-producing factors may negatively 

impact the reproductive success of an individual and, therefore, the continued viability of the 

population. However, based on credible scientific research and that within the GOM, there is a 

long-standing and well-developed OCS Program (more than 60 years); scenarios such as these are 

highly speculative. There are no data to suggest that activities from the previous OCS Programs are 

significantly impacting protected species populations. Therefore, for purposes of this analysis, 

BOEM has considered the potential affects of impact-producing factors that are reasonably 

foreseeable to occur.

Current baselines (including past and present events) are described for all protected species 

under their respective “Affected Environment” sections in the 2017-2022 GOM Multisale EIS. The 

altered baseline includes individual species directly affected by this unexpected unique catastrophic 

event. BOEM understands that each oil-spill event is unique and that its outcome depends on 

several factors, including time of year and location of the release relative to winds, currents, land, 

and sensitive resources, as well as specifics of the well and response effort. Specific to the 

Deepwater Horizon, the Trustees have completed the PDARP/PEIS (Deepwater Horizon Natural 

Resource Damage Assessment Trustees, 2016), which has the purpose and need of assessing and 

creating restoration plans to relieve injuries from the Deepwater Horizon explosion, oil spill, and 

response to natural resourses and services. The injuries assessed within the PDARP/PEIS do not 

necessarily equate the baseline as defined in NEPA. BOEM continues to analyze the Deepwater 

Horizon explosion, oil spill, and response as information becomes available, and it was evaluated as 

part of the baseline for resources in this Supplemental EIS.

BOEM analyzed a low-probability catastrophic event (USDOI, BOEM 2017b) in conjunction 

with its analysis of potential effects, as requested by the CEQ pursuant to its regulation at 40 CFR § 

1502.22. The CEQ (2010) recommended that BOEM should “ensure that NEPA documents provide 

decision makers 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.” A low-probability catastrophic spill is, by definition, not 

reasonably certain to occur. The return period of a catastrophic oil spill in OCS areas is estimated to 

be 165 years, with a 95-percent confidence interval between 41 years and more than 500 years 

(Ji et al., 2014). The use of other methods of analysis in this evaluation are significantly limited in 

their applicability and availability and they would not provide any meaningful or useful information to 
4-118 2018 Gulf of Mexico Supplemental EIS

be used to assess risk of catastrophic spill occurrence at this programmatic level of OCS oil- and 

gas-related activities in the GOM.

4.9.1 Marine Mammals

Summary

BOEM has reexamined the analysis for marine mammals presented in the 2017-2022 GOM 

Multisale EIS based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for marine mammals presented in the 2017-2022 

GOM Multisale EIS. Further, the analysis and potential impacts detailed in that document still apply 

for the remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of marine mammals, along with the full analyses of the potential 

impacts of routine activities, accidental events, and cumulative impacts associated with a proposed 

action are presented in Chapter 4.9.1 of the 2017-2022 GOM Multisale EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the 

2017-2022 GOM Multisale EIS.

Introduction

The Gulf of Mexico marine mammal community is diverse and distributed throughout the 

GOM, including northern Gulf of Mexico U.S. waters. Twenty-one species of cetaceans and one 

species of sirenian (West Indian manatee) regularly occur in the GOM and are identified in NMFS’ 

Gulf of Mexico Stock Assessment Reports (Jefferson et al., 1992; Davis et al., 2000; Waring et al., 

2016). The GOM’s Cetacea include the suborders Mysticeti (i.e., baleen whales) and Odontoceti 

(i.e., toothed whales), and the order Sirenia, which includes the West Indian manatee. Most marine 

mammal distributions vary widely across the northern GOM with very little known about their 

respective breeding and calving grounds, as well as any potential migratory routes.

Along with stock assessment reports, NMFS also calculates the Potential Biological Removal 

(PBR) for cetaceans, which is defined under the MMPA 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 (U.S. Marine Mammal Commission

and USDOC, NMFS, 2007). The PBR can be used as a conservative tool, most often for 

commercial fisheries, to help with management of the different marine mammal stocks because a 

potential impact-producing factor may have a more serious impact on a marine mammal stock that 

has a lower PBR and a less serious impact to a marine mammal stock with a higher PBR. Here, the 

PBR is used as a conservative enalysis tool.

While all marine mammals are protected under the MMPA, the sperm whale is listed as 

endangered and the West Indian manatee is listed as threatened under the ESA, as described in 

detail in the 2017-2022 GOM Multisale EIS. On December 8, 2016, NMFS announced a 12-month 

finding on a petition to list the GOM Bryde’s whale (Balaenoptera edeni) and proposed that it be 
Description of the Affected Environment and Impact Analysis 4-119

listed as endangered under the ESA (Federal Register, 2016b). If NOAA issues a final rule listing 

the Bryde’s whale as endangered, the species will receive additional protections, and Federal 

agencies will be required to consult under Section 7 for Federal actions that may affect the species.

Refer to Chapter 4.9.1 of the of the 2017-2022 GOM Multisale EIS for the full analyses of 

marine mammals. For the Gulf of Mexico, NMFS is charged with protecting all cetaceans, while 

manatees are under the jurisdiction of FWS. Details on BOEM’s consultations and coordination with 

NMFS and FWS are presented in Chapter 5.2 (“Endangered Species Act”). BOEM’s protective 

measures for marine mammals are described below.

Protective Measures for Marine Mammals

The NTL 2016-BOEM-G02, “Implementation of Seismic Survey Mitigation Measures and 

Protected Species Observer Program,” provides guidance to protect marine mammals and sea 

turtles during seismic operations. This NTL clarifies how operators should implement seismic survey 

mitigating measures, including ramp-up procedures, the use of a minimum sound source, airgun 

testing, shutdowns, and protected species observation and reporting. The Protected Species 

Stipulation, if applied, would make compliance with the guidance identified in the NTL mandatory for 

lessee activities. In addition, NMFS, BOEM, and BSEE collaborated to publish National Standards 

for a Protected Species Observer Program, which provides guidance on how to reduce impacts to 

protected species from G&G activities by standardizing the variation in and improving the 

management of the program (Baker et al., 2013).

More detailed information on Gulf of Mexico G&G activities can be found in the Gulf of 

Mexico Geological and Geophysical Activities: Western, Central, and Eastern Planning Areas—

Draft Programmatic Environmental Impact Statement (USDOI, BOEM, 2016c), which BOEM 

prepared with BSEE and the National Oceanic and Atmospheric Administration’s NMFS as 

cooperating agencies, to evaluate the potential environmental impacts of multiple G&G activities 

within Federal waters of the Gulf of Mexico’s OCS and adjacent State waters. BOEM also prepared 

the Atlantic OCS Proposed Geological and Geophysical Activities: Mid-Atlantic and South Atlantic 

Planning Areas—Final Programmatic Environmental Impact Statement (USDOI, BOEM, 2014), 

which can also be a source for more detailed information on the seismic surveying technology and 

techniques.

BOEM issued NTL 2016-BOEM-G01, “Vessel Strike Avoidance and Injured/Dead Protected 

Species Reporting,” which explains how operators must implement measures to minimize the risk of 

vessel strikes to protected species and to report observations of injured or dead protected species. 

The Protected Species Stipulation, when applied, would make compliance with the guidance 

identified in the NTL mandatory for lessee activities. Adherence to the NTL protocols is expected to 

reduce but not eliminate the risk of potential vessel strikes with marine mammals.

To address the potential impacts of marine debris, BSEE issued NTL 2015-BSEE-G03, 

“Marine Trash and Debris Awareness and Elimination,” which provides information on the marine 
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trash and debris awareness training video and slide show, and both postal and email addresses for 

submitting annual training reports. The information provided is intended to greatly minimize the 

amount of debris that is accidentally lost overboard by offshore personnel; however, these directives 

do not eliminate the accidental release of debris, which could impact an individual or group of 

individuals if they become entangled in or ingest accidentally released debris. The Protected 

Species Stipulation, if applied, would make compliance with the guidance identified in the NTL 

mandatory for lessee activities.

BOEM (then the Bureau of Ocean Energy Management, Regulation and Enforcement) 

issued “Decommissioning Guidance for Wells and Platforms” (NTL 2010- BSEE-G05) to offshore 

operators; it provides clarification and interpretation of regulations regarding decommissioning, as 

well as guidance to operators proposing to use explosives to perform well/casing severance. These 

guidelines specify and reference mitigation, monitoring, and reporting requirements. As noted in 

Chapter 3.1.6 of the 2017-2022 GOM Multisale EIS and as summarized in Chapter 3 of this 

Supplemental EIS, decommissioning for wells and platforms are site specific and are reviewed by 

BSEE and BOEM.

Analysis

The analyses of the reasonably foreseeable potential impacts of routine activities and 

accidental events associated with a proposed lease sale and a proposed lease sale’s incremental 

contribution to the cumulative impacts to marine mammals are presented in this chapter. Potential 

impact-level criteria are defined in Chapter 4.9 (“Protected Species”) and apply to marine mammal 

species described in this chapter. The approach of the analysis is to focus on the potential 

impact-producing factors from OCS oil- and gas-related routine activities (i.e., exploration, 

development, and production), as well as accidental events and cumulative impacts, that are 

reasonably foreseeable and to define the impact levels for each impact-producing factor in relation to 

the best available population estimates (refer to Table 4-18 in Chapter 4.9 [“Protected Species”]). 

The potential magnitude of impact and impact-level definitions for each of these impact-producing 

factors is provided in Table 4-18 to help the reader quickly identify the level of potential impacts for 

each impact-producing factor that is reasonably foreseeable. The analyses supporting these 

conclusions are discussed below. Some impact-producing factors may have different potential 

impact levels to different marine mammal species due to their various population sizes, as well as 

their wide-ranging behavior; thus, some potential impact-producing factors are described in a range. 

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. 

Refer to the “Incomplete or Unavailable Information” section below for a more detailed discussion.

BOEM understands that mitigations greatly reduce the likelihood of an impact-producing 

factor, but mitigations do not guarantee that a protected species (e.g., marine mammal) would not be 

impacted. There is a very low probability where a protected species may not be detected despite all 

of the mitigative precautions taken to reduce impact. Unlikely scenarios such as these may cause 

major impacts to a marine mammal species with a very low population because some 
Description of the Affected Environment and Impact Analysis 4-121

impact-producing factors may negatively impact the reproductive success of an individual and 

therefore the continued viability of the population. However, based on credible scientific research 

and that within the GOM, there is a long-standing and well-developed OCS Program (more than 

60 years); scenarios such as these are highly speculative. There are no data to suggest that routine 

activities from the previous OCS Programs are significantly impacting marine mammal populations. 

Therefore, for purposes of this analysis, BOEM has considered the potential effects of impactproducing factors that are reasonably foreseeable.

This chapter provides a summary of the information detailed in the 2017-2022 GOM 

Multisale EIS regarding the impact-producing factors from routine activities, accidental events, and 

cumulative impacts from activities described in Chapter 3 and their potential impacts that could 

result from a single proposed lease sale. BOEM has considered the potential affects of 

impact-producing factors that are reasonably foreseeable based on credible scientific research and 

past data for the following analysis. This analysis applies to all considered alternatives analyzed in 

Chapter 4. 

As discussed in Chapter 4.9.1.1 of the 2017-2022 GOM Multisale EIS, the Potential 

Biological Removal (PBR) of a marine mammal species plays an important role in marine mammal 

management due to the fact that the same impact-producing factor may have a more serious impact 

on a marine mammal stock that has a lower PBR and a less serious impact to a marine mammal 

stock with a higher PBR. In other words, if an impact-producing factor were to negatively affect a 

number of individuals of a marine mammal stock that exceeds its respective PBR estimate, it could 

possibly diminish the continued viability of the stock, including the annual rates of recruitment or 

survival. BOEM understands that PBR is a very conservative estimate and that the abundance 

estimates used in estimating PBR may not accurately reflect the actual abundances of marine 

mammal stocks. The following evaluation considers how the impact-producing factors from routine 

activities, reasonably foreseeable accidental events, and cumulative impacts from activities 

described in Chapter 3 may potentially impact a marine mammal species based on its respective 

PBR (refer to Table 4-14 of the 2017-2022 GOM Multisale EIS for list of marine mammal species 

and their respective PBR). BOEM has made conscientious efforts to comply with the spirit and 

intent of NEPA and to be comprehensive in its analyses of potential environmental impacts to marine 

mammals, including species that are poorly studied.

The major potential impact-producing factors affecting marine mammals in the GOM as a 

result of cumulative past, present, and reasonably foreseeable OCS energy-related activities are 

decommissioning activities, operational discharges, G&G activities, noise, transportation, marine 

debris, and accidental oil-spill and spill-response activities. Accidental events involving large spills, 

particularly those continuing to flow fresh hydrocarbons into oceanic and/or outer shelf waters for 

extended periods (i.e., days, weeks, or months), pose an increased likelihood of impacting marine 

mammal populations inhabiting GOM waters. While accidental events cannot be predicted and have 

the potential to impact marine mammal species, the number of such events is expected to be very 

small based on OSRA (refer to Appendix E of the 2017-2022 GOM Multisale EIS).
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Proposed OCS oil- and gas-related activities would also contribute incrementally to the 

overall OCS oil- and gas-related and non-OCS oil- and gas-related cumulative impacts experienced 

by marine mammal populations. At the regional, population-level scope of this analysis, impacts 

from reasonably foreseeable routine activities and accidental events could be negligible to 

moderate for any of the action alternatives. However, the incremental contribution of a proposed 

action to the cumulative impacts to marine mammal populations, depending upon the affected 

species and their respective population estimate, even when taking into consideration the potential 

impacts of the Deepwater Horizon explosion, oil spill, and response; non-OCS oil- or gas-related 

factors; and the minimization of the OCS oil- or gas-related impacts through lease stipulations and 

regulations, would be expected to be negligible. Under Alternative E, the cancellation of a 

proposed lease sale, the impacts on marine mammals within the Gulf of Mexico would be none. 

However, cumulative impacts from previous lease sales and non-OCS oil- and gas-related activities 

would remain. A full analysis of marine mammals can be found in Chapter 4.9.1 of the 2017-2022 

GOM Multisale EIS. 

Comparison of Alternatives

The effects associated with selection of any of the alternatives would be equivalent because 

of the diversity and distribution of marine mammal species throughout the potential areas of interest. 

The analyses assumed a wide distribution of species and considered impacts to marine mammal 

species occurring in a wide range of habitats across all planning areas. While a proposed WPA 

lease sale (Alternative C) would be in a smaller area with less projected activity than a regionwide 

(Alternative A) or CPA/EPA lease sale (Alternative B) as described in Chapter 3, marine mammal 

species are widely distributed throughout the planning areas and may travel great distances across 

the GOM. As such, activities isolated to specific planning areas pose similar potential impacts to 

populations as do activities occurring in all planning areas. Therefore, a similar mix of species would 

be exposed to the analyzed impact-producing factors, regardless of the specific action alternative 

selected. For example, if a marine mammal species were to be accidentally struck by an OCS 

vessel, it would have the same impact to that individual and its respective population estimate in the 

WPA as it would in the CPA or EPA. Although it can be speculated that a smaller leased area 

resulting in less projected OCS oil- and gas-related activity would decrease the likelihood of OCS 

oil- and gas-related activities impacting marine mammal populations, there are not enough 

conclusive data on the density, distributions, and migratory behaviors of marine mammal populations 

in the GOM throughout the year to support that speculation. Therefore, because of the diversity and 

wide distribution of species in the Area of Interest, the level of impacts would be the same for 

Alternatives A, B, C, and D. Under Alternative E, there would be no new activities associated with a 

proposed lease sale; however, activities associated with past lease sales and non-OCS oil- and 

gas-related activities would continue.

Incomplete or Unavailable Information

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 
Description of the Affected Environment and Impact Analysis 4-123

alternatives; and, if it was essential, whether it can be obtained and whether the cost of obtaining the 

information is exorbitant, as well as whether credible scientific information applied using generally 

accepted scientific methodologies can be used in its place (40 CFR § 1502.22). BOEM has made 

conscientious efforts to comply with the spirit and intent of NEPA and to be comprehensive in its 

analyses of potential environmental impacts.

BOEM has identified incomplete information regarding impacts of the Deepwater Horizon

explosion, oil spill, and response on marine mammals in the GOM. This incomplete information may 

be relevant to the evaluation of adverse impacts because it could provide changes in the baseline 

environmental conditions for marine mammals in the affected environment from the Deepwater 

Horizon oil spill and response, exacerbating any impacts from a proposed action. In NEPA, the term 

“baseline” usually consists of the pre-project environmental conditions. For the purpose of this 

Supplemental EIS, the baseline is the condition of resources in the vicinity of the project as they 

exist at the time this environmental analysis began. The injuries assessed within the PDARP/PEIS 

do not necessarily equate to the current baseline as defined in NEPA. Quantification of a new 

baseline has several difficulties, including the lack of pre-spill data, the interpretation of post-spill 

data, and other potential parameters that may have contributed to the quantification of the new 

baseline. The difference between the state of the resources in an earlier injury assessment and in a 

current baseline assessment equals any recovery that may have occurred. In addition, the injury 

assessment reviews a worst-case impact scenario while a baseline assessment determines a 

reasonable understanding of the current state of the resource.

On December 13, 2010, NMFS declared an unusual mortality event (UME) for cetaceans 

(whales and dolphins) in the Gulf of Mexico; it was later closed in May 2016. Evidence of the UME 

was first noted by NMFS as early as February 2010, before the Deepwater Horizon explosion, oil 

spill, and response. During this UME, spatial and temporal boundaries of stranded cetaceans were 

defined as far as the Florida Panhandle and west to the Louisiana-Texas border (USDOC, NMFS, 

2015a). However, these boundaries were redefined by NOAA, based upon analysis of stranding 

data, to include all cetaceans that stranded in Alabama, Mississippi, and Louisiana from March 2010 

through July 2014 and all cetaceans other than bottlenose dolphins that stranded in the Florida 

Panhandle (Franklin County through Escambia County) from March 2010 through July 2014. The 

NOAA has claimed that these boundaries could be adjusted in the future based upon the availability 

of new results or analyses (USDOC, NMFS, 2016a). As of May 2016, a total of 1,141 cetaceans 

(5% stranded alive and 95% stranded dead) stranded during the UME between Franklin County, 

Florida, and the Louisiana/Texas border. 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 (USDOC, NMFS, 2016a).

The UME investigation and the Deepwater Horizon Natural Damage Resource Assessment 

(NRDA) determined that the Deepwater Horizon explosion, oil spill, and response resulted in the 

death of marine mammals and is the most likely explanation of the persistent, elevated stranding 

numbers in the northern Gulf of Mexico after the spill. Data have supported that the adrenal and 
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lung disease observed in dolphins was most likely due to exposure to petroleum products from the 

spill. This has resulted in both dolphin mortalities, which peaked from March 2010 through July 

2014, and fetal loss. Research, while ongoing, suggests that the effect on these populations has not 

ended, with evidence of failed pregnancies found in 2015 (USDOC, NMFS, 2016a).

Although data have suggested that exposure to petroleum products may result in 

reproductive failure, other factors have the potential to affect marine mammal reproduction and were 

also observed during the timeframe of this UME. In addition to investigating all other potential 

causes, scientists are still investigating what role Brucella plays in the northern Gulf of Mexico UME. 

Brucella is a gram-negative, intracellular bacterium that has been isolated from many marine 

mammal species globally (Nymo et al., 2011; Guzmán-Verri et al., 2012; Hernández-Mora et al., 

2013) and that may cause placentitis and sporadic late-term abortion (Miller et al. 1999; Dagleish 

et al., 2008; Guzmán-Verri et al., 2012; Hernández-Mora et al., 2013). As of October 27, 2015, 

68 out of 210 dolphins tested were positive or suspected positive for Brucella. More detail on 

Brucella and its role in the UME can be found on NMFS’ website (USDOC, NMFS, 2016a). Future 

investigations on immune function in Gulf of Mexico dolphins are needed to determine whether 

exposure to hydrocarbons during the Deepwater Horizon oil spill or other environmental stressors 

may have caused an increased susceptibility to infectious agents that affect the fetal-placental unit 

or other conditions leading to late-term fetal loss (Colegrove et al., 2016). Furthermore, 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.

Various environmental stressors that are known to cause death to marine mammals were 

also present during the Deepwater Horizon explosion, oil spill, and response, but it is unclear at this 

time what level of impact these stressors contributed to the increase in strandings (Carmichael et al., 

2012). According to NMFS’ website referenced above, evidence of the UME was first documented 

by NMFS as early as March 2010, a month prior to the Deepwater Horizon explosion and oil spill. 

The NMFS has also documented an additional 12 UMEs that have been previously declared in the 

GOM for cetaceans (an additional 7 specific to manatees only) since 1991 (USDOC, NMFS, 2015b). 

However, studies published from the NRDA process evaluating the possible impacts 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., 2013; Venn-Watson et al., 2015). Bacterial pneumonia was also identified from dolphins 

before and during the UME, but it was detected more in the UME dolphins (Venn-Watson et al., 

2015). While this information may ultimately be useful in expanding the available knowledge on 
Description of the Affected Environment and Impact Analysis 4-125

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.

Even with recent publications, such as the Venn-Watson et al. (2015) marine mammal study, 

the best available information on impacts to GOM marine resources does not yet provide a complete 

understanding of the impacts of the oil spill and active response/cleanup activities from the 

Deepwater Horizon explosion and oil spill on marine resources as a whole in the GOM. Relevant 

data on the status of marine mammal populations after the UME and 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. 

For example, even 20 years after the Exxon Valdez spill, the long-term impacts to marine mammal 

populations are still being investigated (Matkin et al., 2008). Therefore, it is not possible for BOEM 

to obtain this information within the timeframe contemplated for the NEPA analysis in this 

Supplemental EIS, regardless of the cost or resources needed.

Unavailable information provides challenges in understanding the baseline conditions and 

changes within marine mammal populations. The impacts of tropical storms and hurricanes in the 

GOM have never been determined and the impacts remain very difficult to quantify. The impacts 

associated with the Deepwater Horizon explosion, oil spill, and response makes an understanding of 

the cumulative impacts less defined. The process, timeline, and determination of NMFS’ proposal to 

list the Bryde’s whale as endangered is unknown, but it is not essential to a reasoned choice among 

alternatives because, if listed, BOEM would need to consult under ESA Section 7 (refer to 

Chapter 5.2). BOEM used existing information and accepted scientific methodologies to extrapolate 

from publicly available information on marine mammals in completing the relevant analysis of marine 

mammal populations. There are existing leases in the GOM with ongoing or the potential for 

exploration, drilling, and production activities. In addition, non-OCS oil- and gas-related activities 

would continue to occur in the GOM irrespective of a proposed action (e.g., fishing, military activities, 

and scientific research). Therefore, BOEM concludes that the unavailable information from these 

events may be relevant to foreseeable significant adverse impacts to marine mammals because the 

full extent of impacts on marine mammals is not known. However, BOEM has determined that the 

information is not essential to a reasoned choice among alternatives for this Supplemental EIS 

(including the No Action and Action Alternatives) because none of the sources reveal reasonably 

foreseeable significant adverse impacts to marine mammals not otherwise considered in this 

Supplemental EIS.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including publications from Federal agencies and 

journal articles) were examined to assess recent information regarding marine mammals that may 

be pertinent to a proposed action. No new information that would add to the analyses or change the 

conclusions was discovered since publication of the 2017-2022 GOM Multisale EIS. 
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Conclusion

BOEM has reexamined the analysis for marine mammals presented in the 2017-2022 GOM 

Multisale EIS, with the understanding that no new information on marine mammals has been 

published since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information 

was discovered that would alter the impact conclusion for marine mammals presented in that 

document, and the analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still 

apply for the remaining proposed GOM lease sales in the Five-Year Program. The incremental 

contribution of a proposed lease sale (i.e., Alternatives A, B, C, and D) to cumulative impacts to 

marine mammal populations, depending upon the affected species and their respective population 

estimate, even when taking into consideration the potential impacts of the Deepwater Horizon

explosion, oil spill, and response; non-OCS oil- or gas-related factors; and the minimization of OCS 

oil- or gas-related impacts through lease stipulations and regulations, would be expected to be 

negligible. 

4.9.2 Sea Turtles

Summary

BOEM has reexamined the analysis for sea turtles presented in the 2017-2022 GOM 

Multisale EIS based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for sea turtles presented in the 2017-2022 GOM

Multisale EIS. Further, the analysis and potential impacts detailed in that document still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of sea turtles, along with the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with a proposed action are 

presented in Chapter 4.9.2 of the 2017-2022 GOM Multisale EIS. The following information is a 

summary of the resource description and impact analysis incorporated from the 2017-2022 GOM 

Multisale EIS.

Introduction

Five sea turtle species are known to inhabit the waters of the GOM (Pritchard, 1997): the 

loggerhead (Caretta caretta); Kemp’s ridley (Lepidochelys kempii); green (Chelonia mydas); 

leatherback (Dermochelys coriacea); and hawksbill (Eretmochelys imbricata). All five species are 

highly migratory with individuals migrating into nearshore waters as well as other areas of the GOM, 

North Atlantic Ocean, and the Caribbean Sea, and they use beaches along these coasts during 

nesting season. These sea turtles are protected under the Endangered Species Act of 1973. The 

FWS and NMFS share Federal jurisdiction for sea turtles. The FWS has responsibility for monitoring 

and managing sea turtles (i.e., nesting turtles, eggs, and hatchlings) on the beaches; and NMFS has 

jurisdiction for sea turtles in the marine environment. Refer to Chapter 4.9.2 of the of the 2017-2022 

GOM Multisale EIS for the full analyses of sea turtles. BOEM’s protective measures for sea turtles 

are provided below.
Description of the Affected Environment and Impact Analysis 4-127

Protective Measures for Sea Turtles

Seismic operations have the potential to harm sea turtles in close proximity to active airgun 

arrays. The Protected Species Stipulation and NTL 2016-BOEM-G02, “Implementation of Seismic 

Survey Mitigation Measures and Protected Species Observer Program,” minimize the potential of 

harm from seismic operations to sea turtles that could be within the exclusion zone. These 

mitigations for sea turtles and marine mammals include, but are not limited to, onboard observers, 

ramp-up procedures, shutdowns, and the use of a minimum sound source. Noise impacts on turtles 

from seismic surveys are described in the “Noise” section in Chapter 4.9.2 of the 2017-2022 GOM 

Multisale EIS. More detailed information on the seismic surveying technology and techniques that 

could be used is provided in BOEM’s Atlantic OCS Proposed Geological and Geophysical Activities: 

Mid-Atlantic and South Atlantic Planning Areas—Final Programmatic Environmental Impact 

Statement (USDOI, BOEM, 2014) and as of the publication of this Supplemental EIS, BOEM, with 

BSEE and the National Oceanic and Atmospheric Administration’s NMFS as cooperating agencies, 

prepared the Gulf of Mexico Geological and Geophysical Activities: Western, Central, and Eastern 

Planning Areas—Draft Programmatic Environmental Impact Statement to evaluate the potential 

environmental impacts of multiple G&G activities within Federal waters of the Gulf of Mexico’s OCS 

and adjacent State waters (USDOI, BOEM, 2016c).

There have been no documented sea turtle strikes with drilling and service vessels in the 

GOM; however, collisions with small or submerged sea turtles may go undetected. Based on sea 

turtle density estimates in the GOM, the encounter rates between sea turtles and vessels would be 

expected to be greater in water depths <200 m (656 ft) (USDOC, NMFS, 2007b). To further 

minimize the potential for vessel strikes, NTL 2016-BOEM-G01, “Vessel Strike Avoidanceand 

Injured/Dead Protected Species Reporting,” was issued; this NTL provides NMFS’ guidelines for 

monitoring procedures related to vessel strike avoidance measures for sea turtles and other 

protected species. In the past, compliance with this NTL and other protective measures has been 

mandatory as a result of the Protected Species Stipulation, which has been applied at the lease sale 

stage. With the implementation of these measures and the avoidance of potential strikes from OCS 

vessels, the risk of collisions between oil- and gas-related vessels (including those for G&G, drilling, 

production, decommissioning, and transport) and sea turtles is appreciably reduced, but strikes may 

still occur. BOEM and BSEE monitor for any takes that have occurred as a result of vessel strikes 

and require that any operator immediately report the striking of any animal (NTL 2016-BOEM-G01).

Operators must comply with the guidelines provided in NTL 2015-BSEE-G03, “Marine Trash 

and Debris Awareness and Elimination.” Should a proposed lease sale be held, the NTLs would 

become mandatory under the expected application of the Protected Species Stipulation. The BSEE 

prohibits the disposal of equipment, containers, and other materials into offshore waters by lessees 

(30 CFR § 250.300).

The NTL, “Decommissioning Guidance for Wells and Platforms” (NTL 2010-G05), provides 

guidelines for offshore operators that specify and reference NMFS’ biological opinion mitigation 

requirements currently in place for protected species, including sea turtles. In addition, terms and 
4-128 2018 Gulf of Mexico Supplemental EIS

conditions, and reasonable and prudent measures identified during consultation for 

decommissioning would be required conditions of approval in any decommissioning authorizations. 

The regulations at 30 CFR part 550 outline the environmental, monitoring, and mitigation information 

that operators must submit with plans for exploration, development, and production. This regulation 

requires OCS energy-related activities to be conducted in a manner that is consistent with the 

provisions of the ESA. Additionally, NMFS has implemented a protected species observer program 

for structure decommissioning.

Analysis

The approach of this analysis is to focus on the potential impact-producing factors for sea 

turtles from OCS oil- and gas-related routine activities (i.e., exploration, development, and 

production), as well as reasonably foreseeable accidental events and cumulative impacts, and to 

define the impact levels for each impact-producing factor under a proposed action (refer to 

Table 4-18 in Chapter 4.9 [“Protected Species”]). The potential magnitude of impact and 

impact-level definitions for each of those impact-producing factors is provided in Table 4-18 to help 

the reader quickly identify the level of potential impacts for each impact-producing factor. The 

analyses supporting these conclusions are discussed below.

This chapter provides a summary of the information detailed in the 2017-2022 GOM 

Multisale EIS regarding the impact-producing factors from routine activities, accidental events, and 

cumulative impacts from activities described in Chapter 3 and their potential impacts on sea turtles 

that would potentially result from a single proposed lease sale. This analysis applies to all 

considered alternatives.

Five ESA-listed sea turtle species are present throughout the northern GOM year-round; 

however, only Kemp’s ridley and loggerhead sea turtles commonly nest on beaches in the GOM 

during the nesting season. Due to the expected implementation of mitigations (e.g., BOEM and 

BSEE proposed compliance with NTLs under the proposed Protected Species Stipulation and 

conditions of approval on postlease activities), routine activities (e.g., noise or transportation) and 

accidental events (e.g., oil spills) related to a proposed action are not expected to have long-term 

adverse effects on the population size or productivity of any sea turtle species or populations in the 

northern GOM. Lethal effects could occur from chance collisions with OCS oil- and gas-related 

service vessels or ingestion of accidentally released plastic materials from OCS oil- and gas-related 

vessels and facilities. Most routine activities and accidental events as a result of a proposed action 

are therefore expected to have negligible to moderate impacts. For example, a minor impact might 

be a behavioral change in response to noise while a moderate impact might be a spill contacting an 

individual and causing injury or mortality.

Historically, intense harvesting of eggs, loss of suitable nesting beaches, and fisheriesrelated mortality led to the rapid decline of sea turtle populations. Anthropogenic actions continue to 

pose the greatest threat to sea turtles since their listing under the ESA, as well as natural threats 

including climate change, disease, and natural disasters. The incremental contribution of a 
Description of the Affected Environment and Impact Analysis 4-129

proposed action to the cumulative impacts on sea turtles would be expected to be negligible. 

Population-level impacts are not anticipated. Under Alternative E, the cancellation of a proposed 

lease sale, impacts on sea turtles within the Gulf of Mexico would be none. However, cumulative 

impacts from previous lease sales and non-OCS oil- and gas-related activities would remain. A full 

analysis of sea turtles can be found in Chapter 4.9.2 of the 2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

The effects associated with selection of any of the action alternatives would be equivalent 

because of the diversity and distribution of sea turtles throughout the potential Area of Interest. The 

analyses assumed a wide distribution of species and considered impacts to sea turtles occurring in a 

wide range of habitats across all planning areas. While a WPA lease sale (Alternative C) would be 

in a smaller area with less projected activity than a regionwide (Alternative A) or CPA/EPA lease 

sale (Alternative B) as described in Chapter 3, sea turtles are distributed throughout the planning 

areas. As such, activities isolated to specific planning areas pose similar potential impacts to 

populations as do activities occurring in all planning areas. Therefore, because of the 

free-swimming ability and wide distribution of species across the Area of Interest, the level of 

impacts would be the same for Alternatives A, B, C, and D. However, Alternative E, No Action, 

would avoid impacts from a proposed lease sale and the related postlease activities as the lease 

sale would not be held; only impacts from past lease sales and associated postlease activities or 

other G&G permits would continue.

Incomplete or Unavailable Information

Unavailable information provides challenges in understanding the baseline conditions and 

changes within sea turtle populations. The impacts associated with the Deepwater Horizon

explosion, oil spill, and response makes an understanding of the cumulative impacts less defined but 

overall changes the baseline as in less numbers of individual species. Not all of the information 

collected during the NRDA process, which was used as a basis for their determinations, is yet 

publicly available. BOEM used existing information and reasonably accepted scientific 

methodologies to extrapolate from publicly available information on sea turtles in completing the 

relevant analysis of sea turtle populations. There are existing leases in the GOM with ongoing or the 

potential for exploration, drilling, and production activities. In addition, non-OCS oil- and gas-related 

activities would continue to occur in the GOM irrespective of a proposed action (e.g., fishing, military 

activities, and scientific research). Also, little is known about the early life history of leatherbacks 

regarding the “lost years” (Carr, 1986). BOEM used available research and presented what is 

known in Chapter 4.9.2.1. 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; however, BOEM has determined that the information is 

not essential to a reasoned choice among alternatives for this Supplemental EIS (including the 

No Action and Action Alternatives).
4-130 2018 Gulf of Mexico Supplemental EIS

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including NOAA/NMFS’ Office of Protected Resources 

website and Sea Turtle Stranding and Salvage Network website, Gulf Spill Restoration site 

(PDARP/PEIS), FWS’ Environmental Conservation Online System, National Park Service, JSTOR, 

and Google Scholar) were examined to assess recent information regarding sea turtles that may be 

pertinent to a proposed action. No new information that would add to the analyses or change the 

conclusions was discovered since publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for sea turtles presented in the 2017-2022 GOM

Multisale EIS, with the understanding that no new information on sea turtles has been published 

since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information was 

discovered that would alter the impact conclusion for sea turtles presented in that document, and the 

analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. The incremental contribution of a 

proposed action to the cumulative impacts on sea turtles would be expected to be negligible. 

4.9.3 Beach Mice (Alabama, Choctawhatchee, Perdido Key, and St. Andrew)

Summary

BOEM has reexamined the analysis for beach mice presented in the 2017-2022 GOM 

Multisale EIS based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for beach mice presented in the 2017-2022 GOM

Multisale EIS. Further, the analysis and potential impacts detailed in that document still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of beach mice, along with the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with a proposed action are 

presented in Chapter 4.9.3 of the 2017-2022 GOM Multisale EIS. The following information is a 

summary of the resource description and impact analysis incorporated from the 2017-2022 GOM 

Multisale EIS.

Introduction

The following four subspecies of beach mouse (Peromyscus polionotus) occupy restricted 

habitats in the mature coastal dunes of Florida and Alabama and are federally listed as endangered: 

Alabama (P.p. ammobates); Perdido Key (P.p. trisyllepsis); and Choctawhatchee (P.p. allophrys) 

(listed June 6, 1985; Federal Register, 2006b); and St. Andrew (P.p. peninsularis) (listed 

December 18, 1998; Federal Register, 1998). Current critical habitat is included in the critical habitat 

map (Figure 4-10). Populations of the listed subspecies have fallen to levels approaching 

extinction. These four subspecies of beach mice are similar in appearance but can be identified by 

pelage color and location (Bowen, 1968).
Description of the Affected Environment and Impact Analysis 4-131

Protective Measures for Beach Mice

Impacts to beach mice may occur directly to the animal or its habitat. Marine trash and 

debris could affect beach mice due to the potential to ingest and/or become entangled. The BSEE 

has taken measures to reduce marine debris by imposing marine debris awareness and prevention 

measures on the oil and gas industry through NTL 2015-BSEE-G03, which provides guidance to 

industry operators regarding the reduction of trash and debris elimination into the marine 

environment and informing operators of regulations set by other regulatory agencies (i.e., USEPA 

and USCG). This mitigation is a binding part of leases through the Protected Species Stipulation. 

The OCS oil- and gas-related proposed activities may contribute minimal marine debris or disruption 

to beach mouse areas, but the impacts would be negligible. Due to the proximity of the beach 

mouse habitat to any OCS oil- and gas-related activity, any accidental loss of debris as a result of 

OCS oil- and gas-related activities would be minimal.

Analysis

The approach of this analysis is to focus on the potential impact-producing factors from OCS 

oil- and gas-related routine activities (i.e., exploration, development, and production), as well as 

accidental events and cumulative impacts, and to define the impact levels for each impact-producing 

factor (refer to Table 4-18 in Chapter 4.9 [“Protected Species”]). The potential magnitude of impact 

and impact-level definitions for each of these impact-producing factors is provided in Table 4-18 to 

help the reader quickly identify the level of potential impacts for each impact-producing factor. The 

analyses supporting these conclusions are discussed below.

This chapter provides a summary of the information detailed in the 2017-2022 GOM 

Multisale EIS regarding the impact-producing factors from routine activities, accidental events, and 

cumulative impacts from the activities described in Chapter 3 that are associated with non-OCS

oil- and gas-related and OCS oil- and gas-related activities. This analysis applies to all considered 

alternatives.

Beach mice rely on dune systems as favorable habitat for foraging and maintaining burrows. 

Due to the distance between beach mouse habitat and OCS oil- and gas-related activities, routine 

activities are not likely to affect beach mouse habitat except under very limited situations. Pipeline 

emplacement or construction, for example, could cause temporary degradation of beach mouse 

habitat; however, these activities are not expected to occur in areas of designated critical habitat. 

Accidental oil spills and associated spill-response efforts are not likely to impact beach mice or their 

critical habitat because the species live above the intertidal zone where contact is less likely. Habitat 

loss from non-OCS oil- and gas-related activities (e.g., beachfront development) and predation have 

the greatest impacts to beach mice. Overall, the incremental contribution of impacts from 

reasonably foreseeable routine activities and accidental events to the overall cumulative impacts on 

beach mice is expected to be negligible. Under Alternative E, the cancellation of a proposed lease 

sale, impacts on beach mice would be none. However, cumulative impacts from previous lease 

sales and other non-OCS oil- and gas-related activities would remain. A full analysis of beach mice 

can be found in Chapter 4.9.3 of the 2017-2022 GOM Multisale EIS. 
4-132 2018 Gulf of Mexico Supplemental EIS

Comparison of Alternatives

Because of the distribution of species in the Area of Interest, the level of impacts would be 

generally the same for Alternatives A, B, and D. Alternative C would have no impacts since no 

beach mice habitat exists near the WPA proposed lease sale area. The WPA is approximately 

380 mi (612 km) from known beach mouse habitat; OSRA modeling calculated a <0.05 to 1 percent 

chance of oil from a catastrophic spill contacting beach mouse habitat 30 days post-spill. 

Alternative E, No Action, would only have impacts associated with ongoing activities from past lease 

sales and non-OCS oil- and gas-related activities.

Incomplete or Unavailable Information

BOEM has determined that there is no incomplete or unavailable information regarding the 

listed beach mice relevant to the potential impacts from a proposed action or alternatives, and no 

such information was essential to a reasoned choice among alternatives. BOEM used existing 

information and reasonably accepted scientific methodologies from available information on beach 

mice in completing the relevant analysis of impacts.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed journal articles and Internet sources were examined to assess recent 

information regarding beach mice that may be pertinent to a proposed action. No new information 

that would add to the analyses or change the conclusions was discovered since publication of the 

2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for beach mice presented in the 2017-2022 GOM

Multisale EIS, with the understanding that no new information on beach mice has been published 

since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information was 

discovered that would alter the impact conclusion for beach mice presented in that document, and 

the analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. 

4.9.4 Protected Birds

Summary

BOEM has reexamined the analysis for protected birds presented in the 2017-2022 GOM 

Multisale EIS based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for protected birds presented in the 2017-2022 

GOM Multisale EIS. Further, the analysis and potential impacts detailed in that document still apply 

for the remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of protected birds, along with the full analyses of the potential impacts 

of routine activities, accidental events, and cumulative impacts associated with a proposed action 
Description of the Affected Environment and Impact Analysis 4-133

are presented in Chapter 4.9.4 of the 2017-2022 GOM Multisale EIS. The following information is a 

summary of the resource description and impact analysis incorporated from the 2017-2022 GOM 

Multisale EIS.

Introduction

Protected birds are species or subspecies listed under the ESA by FWS as threatened or 

endangered due to the decrease in their population sizes or loss of habitat; therefore, a proposed 

action could have a greater impact. BOEM is undergoing consultation with FWS to minimize the 

potential impacts to ESA-listed species. The protected birds analyzed in this Supplemental EIS 

include those species that use the OCS or coastal counties/parishes along the Gulf of Mexico during 

any part of their lifecycle and that are listed under the Endangered Species Act as threatened or 

endangered. Other species that met these criteria were excluded if their habitats were more upland 

or away from the coast (Appendix F of the 2017-2022 GOM Multisale EIS). All of the following 

protected bird species are also protected under the Migratory Bird Treaty Act. The impact-producing 

factors that could affect protected birds are outlined in Table 4-18 in Chapter 4.9 (“Protected 

Species”). A review of a description of associated impact-producing factors for these species is 

discussed and can be referenced from Chapter 4.8 (“Birds”). However, similar impact-producing 

factors that may affect protected species may have greater impacts to protected species and their 

associated critical habitat due to their small population size and ESA-listing status. Those impacts 

are considered in the following analysis.

The habitats of the protected bird species described in this Supplemental EIS vary from 

upland habitat, freshwater wetlands, estuarine, coastal beaches, and tidal flats to offshore migration 

and foraging; impacts to the physical aspects of the coastal habitats are identified in Chapter 4.3

(“Coastal Habitats”). Critical habitat is presented in Figure 4-10. 

Collectively, the bird species included in this analysis are distributed across the GOM region 

from southern Florida to eastern Texas as year-round residents or migratory with a strong seasonal 

component. Many of the migratory bird species are less abundant along the GOM during the 

season when they are on their breeding grounds and have higher densities and/or wider distributions 

during migration and non-breeding season.

Protective Measures for Protected Birds

Marine debris produced by OCS oil- and gas-related activities as a result of accidental 

disposal into the water may affect protected birds by entanglement or ingestion. Regulations 

prohibiting intentional disposal of items, beach-cleaning efforts to remove debris from certain 

locations, and the use of marine debris awareness and prevention measures on the oil and gas 

industry through NTL 2015-BSEE-G03 (formerly NTL 2012-BSEE-G01), which provides guidance to 

industry operators regarding the reduction of trash and debris elimination into the marine 

environment and which informs operators of regulations set by other regulatory agencies (i.e., the 

USEPA and USCG), help reduce impacts to protected birds. Implementation of BSEE’s Marine 
4-134 2018 Gulf of Mexico Supplemental EIS

Trash and Debris NTL is required through ESA consultation with FWS and is expected to be applied 

by the oil and gas industry for associated OCS oil- and gas-related activity.

Analysis

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

with a proposed action and a proposed action’s incremental contribution to the cumulative impacts to 

ESA-listed birds are presented in this chapter. The approach of the analysis is to focus on the 

potential impact-producing factors from OCS oil- and gas-related routine activities (i.e., exploration, 

development, and production), as well as accidental events and cumulative impacts, and to define 

the impact levels for each impact-producing factor (refer to Table 4-18 in Chapter 4.9 [“Protected 

Species”]). The potential magnitude of impact and impact-level definitions for each of these 

impact-producing factors is provided in Table 4-18 to help the reader quickly identify the level of 

potential impacts for each impact-producing factor. The analyses supporting these conclusions are 

discussed below.

This chapter provides a summary of the information detailed in the 2017-2022 GOM 

Multisale EIS regarding the impact-producing factors from routine activities, accidental events, and 

cumulative impacts from activities described in Chapter 3 and their potential effects that could 

potentially result from a single proposed lease sale or the alternatives. This analysis applies to all 

considered alternatives. Because of the distribution of the different protected bird species in the 

Area of Interest, the level of impacts would vary from Alternatives A, B, C, and D. However, 

Alternative E, No Action, would only have impacts associated with continuing effects from past lease 

sales and non-OCS oil- and gas-related activities. This chapter will include a summary of the 

potential impacts as they relate to the action alternatives and the protected bird species. The 

analyses of applicable impact-producing factors are the same as those for birds in general (refer to 

Chapter 4.8, “Birds”); however, the resulting level of impact would differ, as defined under the 

protected species impact criteria.

Impacts from routine activities, which include discharges and wastes affecting air and water 

quality, noise, and possibly artificial lighting, would be negligible to protected birds. The listed bird 

species considered are typically coastal birds and would not be exposed to much of the OCS 

oil- and gas-related activities. Waste discharges to air or water produced as a result of routine 

activities are regulated by USEPA and BOEM and are subject to limits to reduce potential impacts; 

therefore, due to precautionary requirements and monitoring, the impacts to protected birds would 

be negligible for any of the action alternatives. The major impact-producing factors resulting from 

accidental events associated with a proposed action that may affect protected birds include 

accidental oil spills and response efforts. In the case of an accidental oil spill, impacts would be 

negligible to moderate depending on the magnitude and spatiotemporal proximity of such an event. 

Major impacts could occur if a large oil spill occurred with direct contact to a protected bird species 

or if the habitat became contaminated resulting in mortality of a listed species. Marine debris 

produced by OCS oil- and gas-related activities as a result of accidental disposal into the water may 

affect protected birds by entanglement or ingestion. Due to the regulations prohibiting the intentional 
Description of the Affected Environment and Impact Analysis 4-135

disposal of items, impacts would be expected to be negligible; however, impacts may scale up to 

moderate if the accidental release of marine debris caused mortality of a listed bird.

Overall, BOEM would expect negligible to moderate impacts to protected birds considering 

routine activities, accidental events, and cumulative impacts for any of the action alternatives. Due 

to the precautionary requirements and monitoring discussed above, the incremental impacts to 

protected birds would be negligible for any of the action alternatives (i.e., Alternatives A-D). For 

Alternative E, the cancellation of a proposed lease sale, the additional incremental impacts to 

ESA-protected birds or their habitats would be none. Cumulative impacts of current and past 

activities (i.e., OCS oil- and gas-related and non-OCS oil- and gas-related), however, would continue 

to occur under this alternative. A full analysis of protected birds can be found in Chapter 4.9.4 of the 

2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

Due to the precautionary requirements and monitoring discussed above, the impacts to 

protected birds would be negligible for any of the action alternatives (i.e., Alternatives A-D). The 

impacts of Alternative B would be the same as Alternative A for all previously specified protected 

bird species, with the exception of the whooping crane with the listed population in Texas in the 

WPA and which is outside of the CPA or EPA. The Cape Sable seaside sparrow, roseate tern, and 

the Mississippi sandhill crane are not found off Texas; therefore, they would not be impacted by a 

proposed lease sale in the WPA. The impacts of Alternative D would be the same as Alternative A, 

B, or C because the areas of potential exclusion are specific to areas that do not have any impact on 

ESA-protected bird species or their habitats. The impacts of Alternative E would yield no additional 

incremental impacts to ESA-protected birds or their habitats.

Incomplete or Unavailable Information

Refer to Chapter 4.8 (“Birds”) for existing incomplete or unavailable Information related to 

protected birds. The conclusions remain unchanged.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed journal articles and Internet sources were examined to assess recent 

information regarding protected birds that may be pertinent to a proposed action. No new relevant 

information that would add to the analyses or change the conclusions was discovered since 

publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for protected birds presented in the 2017-2022 GOM

Multisale EIS, with the understanding that no new information on protected birds has been published 

since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information was 

discovered that would alter the impact conclusion for protected birds presented in that document, 
4-136 2018 Gulf of Mexico Supplemental EIS

and the analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still apply for 

the remaining proposed GOM lease sales in the Five-Year Program. 

4.9.5 Protected Corals

Summary

BOEM has reexamined the analysis for protected corals presented in the 2017-2022 GOM 

Multisale EIS based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for protected corals presented in the 2017-2022 

GOM Multisale EIS. Further, the analysis and potential impacts detailed in that document still apply 

for the remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of protected corals, along with the full analyses of the potential impacts 

of routine activities, accidental events, and cumulative impacts associated with a proposed action 

are presented in Chapter 4.9.5 of the 2017-2022 GOM Multisale EIS. The following information is a 

summary of the resource description and impact analysis incorporated from the 2017-2022 GOM 

Multisale EIS.

Introduction

Corals in the GOM that are protected under the ESA include those listed in Table 4-17. 

Distribution of those listed species within the U.S. Exclusive Economic Zone ranges from the State 

of Florida to Flower Garden Banks National Marine Sanctuary and the U.S. territories of Puerto Rico, 

U.S. Virgin Islands, and Navassa Island. Critical habitat was designated for the elkhorn (Acropora 

palmata) and staghorn (Acropora cervicornis) coral species by NMFS in 2008 and includes four 

counties in the State of Florida (i.e., Palm Beach, Broward, Miami-Dade, and Monroe Counties), as 

well as the U.S. territories of the U.S. Virgin Islands (St. John/St. Thomas and St. Croix) and Puerto 

Rico (Federal Register, 2008b). However, this designated critical habitat is located outside of the 

GOM and is not expected to be affected by a proposed action, as seen in Figure 4-10. Though the 

listed species are protected, they would experience the same types of potential impact-producing 

factors from a proposed action as other coral species inhabitating live bottom habitats. For a 

detailed description and impact analysis of live bottom habitats in the GOM, refer to Chapter 4.6. 

Protective Measures for Protected Corals

Potential routine impact-producing factors on protected corals are the same as those 

analyzed and described in Chapter 4.6.1. Impacts resulting from both routine activities and 

accidental events are mitigated through the Topographic Features Stipulation. Protective measures 

are detailed in NTL 2009-G39. The site-specific survey information required for postlease reviews of 

permit applications would allow BOEM to identify and protect live bottom features (which protected 

corals may inhabit) from potential harm by proposed OCS oil- and gas-related activities by requiring 

that bottom-disturbing activity be distanced from live bottom features. Further, it is believed that 

most, if not all, of the protected corals occur either within the boundaries of the Flower Garden 

Banks National Marine Sanctuary, which is an area currently excluded from future leasing, or far 
Description of the Affected Environment and Impact Analysis 4-137

from the area of proposed activities in shallow waters in and around the Florida Keys and Dry 

Tortugas in State or Federal waters of the EPA that are subject to the Congressional leasing 

moratorium that is in effect through 2022.

Analysis

This chapter provides information regarding the protected coral species. However, the types 

of impact-producing factors affecting these species are the same as those described in 

Chapter 4.6.1 (“Topographic Features”); therefore, they are briefly summarized here in the context 

of the protected coral species. A wider impact analysis for live bottom habitats (which protected 

corals may inhabit) can be found in Chapter 4.6 (“Live Bottom Habitats”). However, the level of 

impact from OCS oil- and gas-related and non-OCS oil- and gas-related activities does differ from 

those seen in Chapter 4.6.1 because the protected coral species have smaller population sizes, and 

localized impacts could have a magnified effect. Therefore, the impact levels for protected coral 

species are described separately in Table 4-18. The potential magnitude of impact and impact-level 

definitions for each of the impact-producing factors is provided in Table 4-18 to help the reader 

quickly identify the level of potential impacts for each impact-producing factor. The analyses 

supporting these conclusions are discussed below.

Some activities as a result of a proposed lease sale have the potential to directly impact 

protected coral habitat within the GOM. Because of the similarity and overlap of the effects of many 

activities that occur in the OCS, the relevant impact-producing factors can result from 

bottom-disturbing activities (i.e., routine activities and accidental events) and the potential accidental 

release of drilling muds and contaminants.

Elkhorn, staghorn, boulder star, lobed star, and mountainous star corals are listed by NMFS 

as threatened due to the decrease in their population sizes; therefore, the relative impacts from a 

proposed action on a particular group of coral colonies could have disproportionately higher 

population-level impacts than what might be realized by other, non-listed coral species. BOEM 

understands this and therefore performs a consultation with NMFS to minimize any potential impacts 

to these species. Though the listed species are protected (given ESA status), they could experience 

the same types of potential impact-producing factors from a proposed action as other coral species. 

Without effective mitigations, routine activities and accidental events resulting from a proposed 

action could directly impact coral habitats within the GOM. The site-specific survey information 

required for postlease reviews of permit applications would allow BOEM to identify and protect live 

bottom features (which protected corals may inhabit) from potential harm by proposed OCS oil- and 

gas-related activities by requiring that bottom-disturbing activity be distanced from live bottom 

features. Assuming adherence to the expected lease stipulations and other postlease protective 

restrictions and mitigations, the routine activities related to a proposed action could have short-term, 

localized and temporary effects on protected corals, if any. While accidental events have the 

potential to cause severe damage to specific coral communities, the number of such events is 

expected to be small, and any impacts would be reduced or prevented by the lease stipulations and 

postlease distancing requirements. Furthermore, the OCS lease blocks in the EPA that are closest 
4-138 2018 Gulf of Mexico Supplemental EIS

to ESA-defined critical habitat areas for listed corals are not being offered in a proposed lease sale 

due to the current leasing moratorium and are, therefore, too distant to be reasonably affected by 

routine activities or accidental events. In addition, many of the protected corals occur within the 

Flower Garden Banks National Marine Sanctuary, which, under the current boundaries, is not 

proposed for future leasing under any of the alternatives in this Supplemental EIS or in the 

2017-2022 GOM Multisale EIS. Therefore, the incremental contribution of activities resulting from a 

proposed action to the overall cumulative impacts to protected corals is expected to be negligible

for any of the action alternatives. Proposed OCS oil- and gas-related activities would contribute 

incrementally to the overall OCS oil- and gas-related and non-OCS oil- and gas-related cumulative 

impacts experienced by corals. The non-OCS oil- and gas-related cumulative impacts to protected 

corals are expected to be dramatically greater than any impacts related to OCS oil and gas activities. 

Under Alternative E, the cancellation of the proposed action, the impacts on protected corals would 

be none. However, cumulative impacts from previous lease sales and non-OCS oil- and gas-related 

activities would remain. A full analysis of protected corals can be found in Chapter 4.9.5 of the 

2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

Under Alternatives A, B, and C, the proposed activities would have the same impact levels to 

protected corals whether they occur in the WPA, CPA, or EPA. While the WPA is a smaller area 

with less projected activity than is proposed for the CPA/EPA (refer to Chapter 3), many of the 

protected corals either occur in the Flower Garden Banks National Marine Sanctuary, which is not 

proposed for leasing under any alternative, or are far from the area of proposed activities. Additional 

protection is provided through lease stipulations and postlease activity reviews and associated 

site-specific information requirements and (when necessary) mitigations. Because of these 

protective measures and because protected corals occur far from areas of proposed activities, 

impacts from reasonably foreseeable routine activities and accidental events are both expected to 

be negligible. A negligible impact would be largely undetectable and may cause slight, localized 

changes to a protected coral species community in which recovery from the impact is expected. No 

mortality or injury to an individual or group would be expected to occur. Under Alternative B, a 

proposed lease sale would not occur in the WPA, which includes the Flower Garden Banks National 

Marine Sanctuary; therefore, impacts to protected corals as a result of a proposed lease sale would 

not be reasonably foreseeable to occur. There would, however, be ongoing cumulative impacts to 

the resources associated with ongoing OCS oil- and gas-related activities resulting from previous 

lease sales and from non-OCS oil- and gas-related activities and conditions. Development of oil and 

gas would, in all likelihood, be postponed to a future lease sale decision; in that case, the overall 

level of OCS oil- and gas-related activity would be delayed, not reduced, at least in the short term. It 

would take several cancelled lease sales before there would likely be a noticeable decrease in 

postlease activities from previous oil and gas lease sales. Under Alternative D, should the blocks 

subject to the Topographic Features Stipulation be excluded, protected corals would be further 

protected by distancing OCS oil- and gas-related activities farther from these habitats, thereby 

reducing the probability of potential impacts from routine activities or accidental events. Under 

Alternative E, there would be no new activities associated with a proposed lease sale; however, 
Description of the Affected Environment and Impact Analysis 4-139

activities associated with past lease sales and non-OCS oil- and gas-related activities and conditions 

would continue.

Incomplete or Unavailable Information

Refer to Chapter 4.6 (“Live Bottom Habitats”) for incomplete or unavailable information 

related to protected corals.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources, including literature from relevant peer-reviewed 

journals and reports, were examined to assess recent information regarding protected corals that 

may be pertinent to a proposed action. No new information that would add to the analyses or 

change the conclusions was discovered since publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for protected corals presented in the 2017-2022 GOM 

Multisale EIS based on the additional information presented above. No new information was 

discovered that would alter the impact conclusion for protected corals presented in the 2017-2022 

GOM Multisale EIS, and the analysis and potential impacts detailed in that document still apply for 

the remaining proposed GOM lease sales in the Five-Year Program. 

4.10 COMMERCIAL FISHERIES

Summary

BOEM has reexamined the analysis for commercial fisheries presented in the 2017-2022 

GOM Multisale EIS. No new information was discovered that would alter the impact conclusion for 

commercial fisheries presented in the 2017-2022 GOM Multisale EIS. The analysis and potential 

impacts detailed in that document still apply for the remaining proposed GOM lease sales in the 

Five-Year Program. 

A detailed description of commercial fisheries, along with the full analyses of the potential 

impacts of routine activities, accidental events, and cumulative impacts associated with a proposed 

action are presented in Chapter 4.10 of the 2017-2022 GOM Multisale EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the 

2017-2022 GOM Multisale EIS.

Introduction

The Gulf of Mexico is home to a large and complex commercial fishing industry. There were 

$1.027 billion in finfish and shellfish landings in the Gulf of Mexico in 2014, which comprised 

19 percent of total U.S. landings (USDOC, NMFS, 2016b). Some of the most economically 

important commercial fisheries in the Gulf of Mexico are white shrimp (Litopenaeus setiferus), brown 

shrimp (Farfantepenaeus aztecus), eastern oysters (Crassostrea virginica), Gulf menhaden 
4-140 2018 Gulf of Mexico Supplemental EIS

(Brevoortia patronus), blue crab (Callinectes sapidus), red grouper (Epinephelus morio), red snapper 

(Lutjanus campechanus), and tunas (Thunnus spp.). Fisheries are managed by NOAA Fisheries 

(NMFS), as advised by the regional fisheries management councils. Commercial fisheries are 

regulated by various mechanisms, including permitting, closures, quotas, and gear restrictions. 

Some of the most common gear types are trawls (for shrimp), purse seines (for menhaden), dredges 

(for oysters), traps (for blue crab), and longlines (for various finfish). Chapter 4.10.1 of the 

2017-2022 GOM Multisale EIS presents data on landings revenues in each Gulf Coast State and 

data on the economic impacts of these revenues. The biological aspects for the targeted species 

are discussed in Chapter 4.7 (“Fish and Invertebrate Resources”) and in greater detail in the same 

Chapter 4.7 of the 2017-2022 GOM Multisale EIS.

Analysis

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

with a proposed action and a proposed action’s incremental contribution to the cumulative impacts to 

commercial fisheries are presented below. The approach of the analysis is to focus on the potential 

impact-producing factors from OCS oil- and gas-related routine activities (i.e., exploration, 

development, and production), as well as accidental events and cumulative impacts, and to define 

the impact levels for each impact-producing factor (Table 4-19). The potential magnitude of impact 

for each impact-producing factor is provided in Table 4-19 to help the reader quickly identify the 

level of potential impacts for commercial fisheries. The impact-level definitions and the analyses 

supporting these conclusions are summarized in this chapter. The analysis in this chapter relies on 

the analysis and conclusions reached in Chapter 4.7 (“Fish and Invertebrate Resources”). 

Therefore, in general, the impact-producing factors identified in Chapter 4.7 would have the 

potential to impact commercial fisheries as well.

Impact-Level Definitions

In this chapter (and in the analyses of the alternatives), the impact levels are defined in terms 

of the duration, intensity, and geographical extent of the impacts to the human uses of commercial 

fisheries along the Gulf Coast. Long-term impacts are those lasting more than 1 year. Extensive 

impacts are those for which it is difficult to find substitute fishing sources nearby, while severe 

impacts mostly or completely prevent commercial fishing in an area. In particular, the impacts of 

each impact-producing factor are summarized in Table 4-19, using the impact-level definitions 

below.

• Beneficial – Impacts would be positive. The level of benefical impacts are 

specified in the analysis, which could be low, medium, or high.

• Negligible – Little or no detectable adverse impact.

• Minor – Adverse impacts are detectable but less than severe.

• Moderate – Adverse impacts are severe but are short term and/or not extensive.

• Major – Adverse impacts are long term, extensive, and severe.
Description of the Affected Environment and Impact Analysis 4-141

Table 4-19. Commercial Fisheries Impact-Producing Factors That Are Reasonably Foreseeable.

Commercial Fisheries Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Activities

Fish Population Negligible to Negligible to Negligible to Negligible to Negligible

Minor Minor Minor Minor

Space-Use Conflicts Negligible to Negligible to Negligible to Negligible to Negligible

Minor Minor Minor Minor

Production Structure 

Emplacement and 

Removal

Beneficial to Beneficial to Beneficial to Beneficial to

Negligible

Minor Minor Minor Minor

Accidental Events

Oil Spills Negligible to Negligible to Negligible to Negligible to Negligible

Minor Minor Minor Minor

Cumulative Impacts

Incremental 

Contribution2

Beneficial to Beneficial to Beneficial to Beneficial to Negligible Minor Minor Minor Minor

OCS Oil and Gas3 Beneficial to

Moderate

Non-OCS Oil and 

Gas4

Beneficial to

Major

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.10 of the 2017-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

A proposed action could affect commercial fisheries by affecting fish populations or the 

socioeconomic aspects of commercial fishing. The impacts of a proposed action on fish populations 

are presented in Chapter 4.7. Routine activities such as seismic surveys, drilling activities, and 

service-vessel traffic can cause space-use conflicts with fishermen. Structure emplacement could 

have positive or negative impacts, depending on the location and species. For example, structure 

emplacement prevents trawling in the associated area and, thus, could impact the shrimp fishery. 

On the other hand, production platforms can facilitate fishing for reef fish such as red snapper and 

groupers. The eventual removal of production platforms would reverse these positive and negative 

impacts. Accidental events, such as oil spills, could cause fishing closures and have other impacts 

on the supply and demand for seafood. However, accidental events that could arise from a 

proposed action would likely be small and localized. A proposed action would be relatively small 

when compared with the overall OCS Oil and Gas Program, State oil and gas activities, overall 
4-142 2018 Gulf of Mexico Supplemental EIS

vessel traffic, tropical storms/hurricanes, economic factors, Federal and State fisheries management 

strategies, and other non-OCS oil- and gas-related factors. Therefore, the incremental contribution 

of a proposed action to the cumulative impacts to commercial fisheries would range from beneficial 

(low) to minor for any of the action alternatives. A full analysis of commercial fisheries can be found 

in Chapter 4.10 of the 2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

The level of impacts to commercial fisheries would range from beneficial (low) to minor for 

Alternatives A, B, C, and D. While there are some differences in the amount of activities associated 

with the alternatives, many of the impacts associated with the alternatives are similar because the 

types of activities that occur are similar and the differences are not large enough to change the 

range of impact conclusions. The exact impacts would depend on the locations of activities, species 

affected, intensity of commercial fishing activity in the affected area, and substitutability of any lost 

fishing access. Alternative E would prevent these impacts from occurring, except for potential 

negligible impacts arising from adjustments to incomes in the economy. Under Alternative E, 

fisheries would still be subject to the impacts from the OCS Oil and Gas Program, as well as the 

impacts from non-OCS oil- and gas-related activities.

Incomplete or Unavailable Information

BOEM has determined that there is incomplete or unavailable information related to 

commercial fisheries. Some of this incomplete or unavailable information relates to fish populations 

that support commercial fishing, which is discussed in Chapter 4.7. For example, there is 

incomplete or unavailable information regarding the long-term impacts of acute and chronic 

exposure to oil on fish and invertrebrates that support commercial fishing. This information is 

unavailable because these impacts would only become evident through time. In lieu of the 

incomplete or unavailable information, BOEM used various data sources and studies, including the 

most recent NMFS landings data, as well as the information in Carroll et al. (2016), to estimate the 

affected environment and impacts of OCS oil- and gas-related and non-OCS oil- and gas-related 

activities for commercial fishing. BOEM has determined that the incomplete or unavailable 

information is not essential to a reasoned choice among alternatives because existing data sources 

are sufficient for BOEM to reasonably estimate impacts.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various sources (such as NMFS and Internet searches) were examined to assess recent 

information regarding commercial fisheries that may be pertinent to a proposed action. No new 

information that would add to the analyses or change the conclusions was discovered since 

publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for commercial fisheries presented in the 2017-2022 

GOM Multisale EIS, with the understanding that no new information on commercial fisheries has 
Description of the Affected Environment and Impact Analysis 4-143

been published since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new 

information was discovered that would alter the impact conclusion for commercial fisheries 

presented in that document, and the analysis and potential impacts detailed in the 2017-2022 GOM

Multisale EIS still apply for the remaining proposed GOM lease sales in the Five-Year Program. 

4.11 RECREATIONAL FISHING

Summary

BOEM has reexamined the analysis for recreational fishing presented in the 2017-2022 

GOM Multisale EIS based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for recreational fishing presented in the 2017-2022 

GOM Multisale EIS. The analysis and potential impacts detailed in that document still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of recreational fishing, along with the full analyses of the potential 

impacts of routine activities, accidental events, and cumulative impacts associated with a proposed 

action are presented in Chapter 4.11 of the 2017-2022 GOM Multisale EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the 

2017-2022 GOM Multisale EIS.

Introduction

Recreational fishing is a popular pastime in many parts of the Gulf of Mexico. The GOM’s 

extensive estuarine habitats (Chapter 4.3), live bottom habitats (Chapter 4.6), and artificial 

substrates (including artificial reefs, shipwrecks, and oil and gas platforms) support several valuable 

recreational fisheries. Fisheries are managed by NOAA Fisheries (NMFS), as advised by the 

regional fisheries management councils. Recreational landings and effort data for Louisiana, 

Mississippi, Alabama, and Florida are provided by NMFS; recreational fishing data for Texas is 

provided by the Texas Parks and Wildlife Department. These data, along with data on the economic 

impacts of recreational fishing, are presented in the 2017-2022 GOM Multisale EIS. The biological 

aspects of the affected environment are discussed in Chapter 4.7 (“Fishes and Invertebrate 

Resources”) of this Supplemental EIS and Chapter 4.7 of the 2017-2022 GOM Multisale EIS.

Analysis

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

with a proposed lease sale and a proposed lease sale’s incremental contribution to the cumulative 

impacts to recreational fishing are presented below. The approach of the analysis is to focus on the 

potential impact-producing factors from OCS oil- and gas-related routine activities (i.e., exploration, 

development, and production), as well as the accidental events and cumulative impacts, and to 

define the impact levels for each impact-producing factor. The analysis in this chapter relies on the 

analysis and conclusions reached in Chapter 4.7 (“Fish and Invertebrate Resources”). Therefore, in 

general, the impact-producing factors identified in Chapter 4.7 would have the potential to impact 

recreational fishing as well.
4-144 2018 Gulf of Mexico Supplemental EIS

Impact-Level Definitions

In this chapter (and in the analyses of the alternatives), the impact levels are defined in terms 

of the intensity, duration, and geographical extent of the impacts to the human uses of recreational 

fisheries along the Gulf Coast. Long-term impacts are those lasting more than 1 year. Extensive 

impacts are those for which it is difficult to find substitute fishing sources nearby, while severe 

impacts mostly or completely prevent recreational fishing in an area. The impacts of each 

impact-producing factor are summarized in Table 4-20 using the impact-level definitions below to 

help the reader quickly identify the level of potential impacts for recreational fishing. The analyses 

supporting these conclusions are summarized below.

• Beneficial – Impacts would be positive. The level of benefical impacts are 

specified in the analysis, which could be low, medium, or high.

• Negligible – Little or no detectable adverse impact.

• Minor – Adverse impacts are detectable but less than severe.

• Moderate – Adverse impacts are severe but are short term and/or not extensive.

• Major – Adverse impacts are long term, extensive, and severe.

Table 4-20. Recreational Fishing Impact-Producing Factors That Are Reasonably Foreseeable. 

Recreational Fishing Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Activities

Anthropogenic Sound Negligible to Negligible to Negligible to Negligible to Negligible

Minor Minor Minor Minor

Bottom-Disturbing 

Activities Negligible Negligible Negligible Negligible Negligible

Space-Use Conflicts Negligible to Negligible to Negligible to Negligible to Negligible Minor Minor Minor Minor

Production Structure 

Emplacement and 

Removal

Beneficial to Beneficial to Beneficial to Beneficial to

Negligible

Minor Minor Minor Minor

Accidental Events

Oil Spills Negligible to Negligible to Negligible to Negligible to Negligible Minor Minor Minor Minor

Cumulative Impacts

Incremental 

Contribution2

Beneficial to Beneficial to Beneficial to Beneficial to Negligible Minor Minor Minor Minor

OCS Oil and Gas3 Beneficial to

Moderate

Non-OCS Oil and Gas4 Beneficial to

Major
Description of the Affected Environment and Impact Analysis 4-145

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.11 of the 2017-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

Alternatives A-D can affect recreational fishing by affecting fish populations or by affecting 

the socioeconomic aspects of recreational fishing. The impacts of Alternatives A-D on fish 

populations are presented in Chapter 4.7 (“Fishes and Invertebrate Resources”). Vessel traffic

associated with a proposed action can cause space-use conflicts with anglers. Structure 

emplacement generally enhances recreational fishing, although this positive effect will be offset 

during decommissioning unless a structure were maintained as an artificial reef. Accidental events, 

such as oil spills, can cause fishing closures and can affect the aesthetics of fishing in an area. 

However, accidental events that could arise would likely be small and localized. Alternatives A-D 

should also be viewed in light of overall trends in OCS platform decommissioning, State oil and gas 

activities, overall vessel traffic, tropical storms/hurricanes, economic factors, and Federal and State 

fisheries management strategies. The incremental impacts of Alternatives A-D on recreational 

fisheries are expected to be beneficial (low) (due to fish attraction at platforms and the potential use 

of decommissioned platforms as rigs-to-reefs) to minor adverse incremental impacts (due to 

impacts to fish populations, space-use conflicts, and oil spills) on recreational fishing activities 

because of the limited amount of activity and because the positive and negative impacts would 

partially offset each other. Alternative E would cause some economic adjustments (refer to 

Chapter 4.14.2), which could cause negligible impacts to recreational fishing activities. Cumulative 

impacts of current and past activities (i.e., OCS oil- and gas-related and non-OCS oil- and 

gas-related), however, would continue to occur under this alternative. A full analysis of recreational 

fishing can be found in Chapter 4.11 of the 2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

The level of impacts to recreational fishing would range from beneficial (low) to minor for 

Alternatives A, B, C, and D. While there are some differences in the amount of activities associated 

with the alternatives, many of the impacts associated with the alternatives are similar because the 

types of activities that occur are similar and the differences are not large enough to change the 

range of impact conclusions. Alternative E would prevent these impacts from occurring, except for 

negligible changes to recreational fishing due to changes in income patterns in the economy.

Incomplete or Unavailable Information

BOEM has identified incomplete or unavailable information regarding the extent to which 

recreational fishing is dependent upon OCS platforms, as well as on the site-specific determinants of 

this dependency. In lieu of this incomplete or unavailable information, BOEM used existing 

information and reasonably accepted scientific methodologies. For example, BOEM used data on 
4-146 2018 Gulf of Mexico Supplemental EIS

recreational fishing activity provided by the Texas Parks and Wildlife Department and NMFS to 

examine trends in recreational fishing in various areas. BOEM has also used information from Heitt 

and Milon (2002) and Ajemian et al. (2015), which provide some information on the scale and 

location of platform-dependent recreational fishing. BOEM does not expect the incomplete or 

unavailable information to significantly change its estimates of the impacts of the OCS Oil and Gas 

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.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various sources (including NMFS, the Texas Parks and Wildlife Department, and Internet 

searches) were examined to assess recent information regarding recreational fishing that may be 

pertinent to a proposed action. No new information that would add to the analyses or change the 

conclusions was discovered since publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for recreational fishing presented in the 2017-2022 

GOM Multisale EIS, with the understanding that no new information on recreational fishing has been 

published since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information 

was discovered that would alter the impact conclusion for recreational fishing presented in that 

document, and the analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still 

apply for the remaining proposed GOM lease sales in the Five-Year Program. 

4.12 RECREATIONAL RESOURCES

Summary

BOEM has reexamined the analysis for recreational resources presented in the 2017-2022 

GOM Multisale EIS based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for recreational resources presented in the 

2017-2022 GOM Multisale EIS. The analysis and potential impacts detailed in that document still 

apply for the remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of recreational resources, along with the full analyses of the potential 

impacts of routine activities, accidental events, and cumulative impacts associated with a proposed 

action are presented in Chapter 4.12 of the 2017-2022 GOM Multisale EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the 

2017-2022 GOM Multisale EIS.

Introduction

Recreational resources are natural or manmade things that are used as part of activities that 

are primarily for human enjoyment. The GOM is home to various resources that support recreational 
Description of the Affected Environment and Impact Analysis 4-147

activities. These include ocean-based resources as well as resources in the counties and parishes 

along the Gulf of Mexico. Chapter 4.12.1 of the 2017-2022 GOM Multisale EIS provides information 

regarding the affected environment for recreational resources, including data on the scales of 

recreation and tourism in onshore areas, as well as information regarding beaches, wildlife viewing, 

artificial reefs, and marine protected areas in the Gulf of Mexico region.

Analysis

This chapter analyzes the potential impacts of routine activities and accidental events 

associated with a proposed action on recreational resources, as well as a proposed action’s 

incremental contribution to the cumulative impacts to recreational resources. The approach of the 

analysis is to focus on the potential impact-producing factors from OCS oil- and gas-related routine 

activities (i.e., exploration, development, and production), accidental events, and cumulative 

impacts, and to define the impact levels for each impact-producing factor.

Impact-Level Definitions

In this chapter (and in the analyses of the alternatives) the impact levels are defined in terms 

of the intensity, duration, and geographical extent of the impacts to the human uses of recreational 

resources along the Gulf Coast. Long-term impacts are those lasting more than 1 year. Extensive 

impacts are those for which it is difficult to find substitute recreational activities nearby, while severe 

impacts mostly or completely diminish the recreational value of a resource. In particular, the impacts 

of each impact-producing factor are summarized in Table 4-21 using the impact-level definitions 

below to help the reader quickly understand the potential impacts of a proposed lease sale on 

recreational resources. The analyses supporting these conclusions are discussed below.

• Beneficial – Impacts would be positive. The level of benefical impacts are 

specified in the analysis, which could be low, medium, or high.

• Negligible – Little or no detectable adverse impact.

• Minor – Adverse impacts are detectable but less than severe.

• Moderate – Adverse impacts are severe but are short term and/or not extensive.

• Major – Adverse impacts are long term, extensive, and severe.

For Alternatives A-D, space-use conflicts (from vessel traffic) and visual impacts (from the 

visibility of OCS structures) that arise due to the broader OCS Program would be negligible to 

minor. Structure emplacements can have beneficial (low) impacts on recreational fishing and 

diving because platforms often act as artificial reefs, but the eventual removal of these structures 

would lead to negligible to minor negative impacts. Oil spills can have a negligible to minor

negative effect on beaches and other coastal recreational resources. Alternatives A-D should also 

be viewed in light of the overall OCS Program, as well as various non-OCS oil- and gas-related 

factors such as beach/wetlands erosion, beach disruptions, economic factors, and activities that can 

cause space-use conflicts and aesthetic impacts, such as commercial and military activities.
4-148 2018 Gulf of Mexico Supplemental EIS

Table 4-21. Recreational Resources Impact-Producing Factors That Are Reasonably Foreseeable. 

Recreational Resources Magnitude of Potential Impact1

Impact-Producing 

Factors Alternative A Alternative B Alternative C Alternative D Alternative E

Routine Activities

Space-Use Conflicts Negligible to Negligible to Negligible to Negligible to Negligible

Minor Minor Minor Minor

Structure Emplacement 

and Removal

Beneficial to Beneficial to Beneficial to Beneficial to

Negligible 

Minor Minor Minor Minor

Visual Impacts Negligible to Negligible to Negligible Negligible to Negligible

Minor Minor Minor

Indirect Econoic 

Impacts

Beneficial to Beneficial to Beneficial to Beneficial to

Negligible 

Minor Minor Minor Minor

Accidental Events

Oil Spills Negligible to Negligible to Negligible to Negligible to Negligible Minor Minor Minor Minor

Marine Debris Negligible to Negligible to Negligible to Negligible to Negligible

Minor Minor Minor Minor

Cumulative Impacts

Incremental 

Contribution2

Beneficial to Beneficial to Beneficial to Beneficial to Negligible Minor Minor Minor Minor

OCS Oil and Gas3 Beneficial to

Moderate

Non-OCS Oil and Gas4 Beneficial to

Major

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.12 of the 2017-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales. 

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

Comparison of Alternatives

Because of the relatively small contribution of any given lease sale under any of the action 

alternatives (i.e., Alternatives A-D) to the overall OCS Program, in addition to other non-OCS oil- and 

gas-related activities, the incremental impacts are expected to be beneficial (low) to minor adverse 

effects. However, the visual impacts of production structures arising from Alternative C would be 

negligible because of the distances of these structures from shore. There could be negligible

impacts to recreational resources due to the small economic adjustments that would occur in light of 
Description of the Affected Environment and Impact Analysis 4-149

Alternative E. Cumulative impacts of current and past activities (i.e., OCS oil- and gas-related and 

non-OCS oil- and gas-related), however, would continue to occur under this alternative. A full 

analysis of recreational resources can be found in Chapter 4.12 of the 2017-2022 GOM Multisale 

EIS.

Incomplete or Unavailable Information

There is some incomplete or unavailable information regarding the visual impacts from a 

proposed action. In particular, the attitudes of people towards the visibility of structures that could 

arise in certain areas 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 would arise from a 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 a proposed action, including 

literature sources, data sources, and photographic evidence. This evidence suggests that the 

incremental visual impacts of a proposed action would be negligible to minor. In addition, BOEM 

has issued an Information to Lessees and Operators to ensure that visual impacts near the Gulf 

Islands National Seashore are considered at BOEM’s site-specific review stage.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various sources (including Internet searches related to the Gulf Islands National Seashore, 

economic conditions, and oil-spill impacts) were examined to assess recent information regarding 

recreational resources that may be pertinent to a proposed action. No new information that would 

add to the analyses or change the conclusions was discovered since publication of the 2017-2022 

GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for recreational resources presented in the 2017-2022 

GOM Multisale EIS, with the understanding that no new relevant information on recreational 

resources has been published since the publication of the 2017-2022 GOM Multisale EIS. 

Therefore, no new information was discovered that would alter the impact conclusion for recreational 

resources presented in that document, and the analysis and potential impacts detailed in the 

2017-2022 GOM Multisale EIS still apply for the remaining proposed GOM lease sales in the 

Five-Year Program. 

4.13 ARCHAEOLOGICAL RESOURCES

Summary

BOEM has reexamined the analysis for archaeological resources presented in the 

2017-2022 GOM Multisale EIS based on the additional information presented below. No new 

information was discovered that would alter the impact conclusion for archaeological resources
4-150 2018 Gulf of Mexico Supplemental EIS

presented in the 2017-2022 GOM Multisale EIS. Further, the analysis and potential impacts detailed 

in that document still apply for the remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of archaeological resources, along with the full analyses of the 

potential impacts of routine activities, accidental events, and cumulative impacts associated with a 

proposed action are presented in Chapter 4.13 of the 2017-2022 GOM Multisale EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the 

2017-2022 GOM Multisale EIS.

Introduction

Archaeological resources are any material remains of human life or activities that are at least 

50 years of age and that are capable of providing scientific or humanistic understanding of past 

human behavior, cultural adaptation, and related topics through the application of scientific or 

scholarly techniques, such as controlled observation, contextual measurement, controlled collection, 

analysis, interpretation, and explanation (30 CFR § 550.105).

Available evidence suggests that sea level in the northern GOM was at least 90 m (295 ft), 

and possibly as much as 130 m (427 ft), lower than present sea level during the period 

20,000-17,000 years Before Present (B.P.) (Nelson and Bray, 1970). Sea level in the northern GOM 

reached its present stand around 3,500 years B.P. (Pearson et al., 1986). During periods that the 

continental shelf was exposed above sea level, the area was open to habitation by prehistoric 

peoples.

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. Europeans are known to have 

traversed the waters of the western Gulf of Mexico as early as Captain Alonso Alvarez de Piñeda’s 

expedition in 1519. Alvar Nuñez Cabeza de Vaca is likely the first European to be shipwrecked 

along the Texas coast as early as 1528 (Francaviglia, 1998).

Protective Measures for Archaeological Resources

To mitigate potential adverse impacts to archaeological resources, BOEM requires an 

archaeological reconnaissance survey of areas impacted by bottom-disturbing activities and 

avoidance or other actions, up to and including full Phase III excavation, of all potential 

archaeological resources within the identified area of potential effect of the undertaking. Based on 

shallow hazard survey data and shipwreck discoveries since 2008, an archaeological survey may be 

required as a result of site-specific NEPA analysis conducted for new bottom-disturbing activity 

associated with plans (USDOI, BOEM, 2011). Archaeological surveys, where required prior to an 

operator beginning OCS oil- and gas-related activities, are expected to identify possible 

archaeological sites so that they may be avoided. BOEM requires operators to submit an 

archaeological report with their EP, DOCD, DPP, or other permit application for certain OCS lease 
Description of the Affected Environment and Impact Analysis 4-151

blocks. These requirements are posted on BOEM’s website under NTL 2005-G07 and NTL 

2011-JOINT-G01. Table 4-22 illustrates the results of the surveys and archaeological reviews 

between 2009 and 2014. The number of shipwrecks and potential archaeological sites, identified 

each year through archaeological reviews and surveys, are listed in Table 4-22. 

Table 4-22. Archaeological Surveys and Resources Identified, 2009-2014.

Year Blocks 

Surveyed

Identified 

Shipwreck Sites

Potential Archaeological Sites Mitigated by Avoidance

(identified through requisite industry surveys)

2009 118 11 479 magnetic anomalies and 103 sonar targets

2010 74 8 274 magnetic anomalies and 100 sonar targets

2011 120 15 577 magnetic anomalies and 171 sonar targets

2012 115 15 341 magnetic anomalies and 112 sonar targets

2013 166 6 374 magnetic anomalies and 163 sonar targets

2014 144 13 417 magnetic anomalies and 146 sonar targets

As per NTL 2010-G05 (“Decommissioning Guidance for Wells and Platforms”) (idle iron 

initiative), idle and toppled oil and gas industry-related structures embedded in the seafloor, 

including single-leg caissons, multi-legged jacketed fixed platforms, floating platforms secured by 

suction pilings, and subsea well-head and manifold systems, must be decommissioned and 

removed. Depending on water depth, seafloor characteristics, and vessel availability, an anchored 

barge, moored barge, or liftboat may be used. Additionally, the site must be cleared of debris to a 

radius of 600 or 1,320 ft (183 or 402 m) depending on the structure type and use. Clearance may be 

carried out by trawling or by sonar and diving operations. As of 2013, BOEM may require, as a 

condition of approval for a decommissioning permit, an archaeological survey in advance of 

structure-removal activities when no preexisting survey of the area of potential effect exists.

Under 30 CFR § 550.194(c) lessees are required to immediately 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 notify BOEM’s and BSEE’s 

Regional Directors of the discovery of any potential archaeological resources.

Analysis

Impacts to archeological sites occur when proposed activities result in complete or partial 

destruction of the resource and are equivalent to a loss of integrity as defined in the National Historic 

Preservation Act (54 U.S.C. §§ 300101 et seq.). In determining the appropriate impact threshold, 

both the extent to which the proposed activity results in a loss of integrity and the degree to which 

losses can be compensated by mitigating activities, including preservation or data recovery, are 

considered. For the purposes of this analysis, all alternatives may be assumed to have effectively 

similar potential impacts to archaeological resources. Only those resources determined eligible or 

potentially eligible for listing in the National Register of Historic Places are considered under the 

National Historic Preservation Act. Resources are eligible for listing in the National Register of 

Historic Places if they meet one or more eligibility criteria (for archeological sites, generally 
4-152 2018 Gulf of Mexico Supplemental EIS

Criterion D, having the potential to provide information important to history or prehistory) and if they 

possess integrity. For purposes of archaeological mitigation, BOEM/BSEE considers all uninspected 

shipwrecks, sonar targets, and magnetic anomalies to be potentially eligible for the National Register 

of Historic Places.

For the analysis of impacts to archeological resources, the determination of the intensity of 

an impact is based on the foreseeable loss of integrity to known or potential resources. The analysis 

considers only the direct impacts of seafloor disturbance associated with the below-listed, impactproducing factors as there would be no additional impacts upon archeological resources under any 

of the alternatives under consideration upon completion of said activities. As each archaeological 

resource is unique and exists at a specific location on the seafloor, there is a high level of variability 

in how a site may be impacted by any potential impact-producing factor. Therefore, it is impossible 

to evaluate the potential impact to an archaeological site from a proposed action at the 

programmatic level. During postlease activities, each permitted action would be assessed for sitespecific potential impacts during the permit application process, and avoidance buffers would be 

placed around identified resources in order to mitigate potential impacts. 

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

with a proposed action and a proposed action’s incremental contribution to the cumulative impacts 

are presented below. The approach of the analysis is to focus on the potential impact-producing 

factors from routine OCS oil- and gas-related activities (i.e., exploration, development, and 

production), as well as accidental events and cumulative impacts. Archaeological resources are 

primarily impacted by any activity that directly disturbs or has the potential to disturb the seafloor. 

For the OCS Program, this includes the placement of drilling rigs and production systems on the 

seafloor; pile driving associated with platform emplacement; pipeline placement and installation; the 

use of seismic receiver nodes and cables; the dredging of new channels, as well as maintenance 

dredging of existing channels; anchoring activities; post-decommissioning activities including 

trawling clearance; and the masking of archaeological resources from industry-related infrastructure 

and debris. Visual impacts to coastal archaeological and historic sites are not considered, as 

offshore oil and gas infrastructure has existed on the OCS since the 1940s and constitutes a 

seaward historic viewshed in its own right. Additionally, offshore oil and gas infrastructure predates 

the National Historic Preservation Act, and therefore, any coastal historic property currently on the 

National Register of Historic Places would not derive its eligibility from an unobstructed view of the 

GOM.

Impact-Level Definitions

The definition of impact thresholds used in this analysis are listed below.

• Beneficial – An archeological site is stabilized in its current condition to maintain 

its existing level of integrity or an archeological site is preserved in accordance 

with the Secretary of the Interior’s Standards for the Treatment of Historic 

Properties. 
Description of the Affected Environment and Impact Analysis 4-153

• Negligible – The lowest level of detection that would have neither adverse nor 

beneficial impacts.

• Minor – Disturbance of archaeological resources would result in little, if any, loss 

of site integrity.

• Moderate – Site disturbance would result in a loss of integrity and a partial loss 

of the character-defining features and information potential that form the basis of 

the site’s National Register of Historic Places’ eligibility. Mitigation is 

accomplished by a combination of archeological data recovery and in-place 

preservation.

• Major – The disturbances result in a loss of site integrity to the extent that the 

resource is no longer eligible for listing in the National Register of Historic Places. 

The site’s character-defining features and information potential are lost to the 

extent that archeological data recovery is the primary form of mitigation.

Duration: Short-term impacts last for the duration of construction-related activities while 

long-term impacts last beyond the proposed construction activities and are permanent. Generally, 

impacts to archeological sites are considered long-term impacts.

The impact of coastal and marine environmental degradation from OCS oil- and gas-related 

activities is expected to minimally affect cultural resources in comparison to other sources of coastal 

erosion and subsidence. Impacts of routine discharges are localized in time and space, are 

regulated by USEPA permits, and would have minimal impact. Accidental events that could impact 

archaeological resources include blowouts and oil or chemical spills and the associated cleanup 

response activities, and also the loss of debris from an MODU, platform, lay barge, etc. during 

offshore operations. A noncatastrophic oil spill (even one reasonably foreseeable as a result of a 

proposed lease sale) occurring and contacting a submerged archaeological resource is unlikely, 

given that oil released tends to rise quickly to the surface and that the average size of a spill is 

<1 bbl (refer to Chapter 3.2.2 of this Supplemental EIS and Chapter 3.2.1 of the 2017-2022 GOM 

Multisale EIS).

Offshore oil and gas activities resulting from a proposed action could adversely impact an 

archaeological resource because of incomplete knowledge on the location of these sites in the 

GOM. The risk of contact to archaeological resources is greater in instances where archaeological 

survey data are 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 would reduce the potential for adverse impacts on archaeological 

resources. As part of the environmental reviews conducted for postlease activities, available 

information would be evaluated regarding the potential presence of archaeological resources within 

the proposed action area to determine if additional archaeological resource surveys and mitigation is 

warranted.
4-154 2018 Gulf of Mexico Supplemental EIS

Regardless of which planning area a proposed lease sale is held, the greatest potential 

impact to an archaeological resource as a result of a proposed action under any of the action 

alternatives is site-specific and would result from direct contact between an offshore activity or 

accidental event and a site. A proposed action’s postlease activities, including the drilling of wells 

and installation of platforms, installation of pipelines, anchoring, and removal of platforms and other 

structures installed on the seafloor and site clearance activities, as well as accidental events such as 

loss of debris, may result in negligible to major impacts to archaeological sites.

Major impacts could potentially occur if the mitigations described above were not applied to 

postlease activities. With identification, evaluation, and avoidance or mitigation of archeological 

resources, the incremental contribution of a proposed action is expected to result in negligible, 

long-term cumulative impacts to archeological resources; however, if an archaeological site were to 

be impacted, impacts may range from negligible to major. Under Alternative E, the 

impact-producing factors mentioned above would not take place for that proposed lease sale; 

therefore, the impacts would be none. Cumulative impacts of current and past activities (i.e., OCS

oil- and gas-related and non-OCS oil- and gas-related), however, would continue to occur under this 

alternative. A full analysis of archaeological resources can be found in Chapter 4.13 of the 

2017-2022 GOM Multisale EIS. 

Comparison of Alternatives

For the purposes of this analysis, all alternatives may be assumed to have effectively similar 

potential impacts to archaeological resources. Therefore, the level of impacts would be the same for 

Alternatives A, B, C, and D. Under Alternative E, there would be no new activities associated with a 

proposed lease sale; however, activities associated with past lease sales and non-OCS oil- and 

gas-related activities would continue.

Incomplete or Unavailable Information

There is incomplete or unavailable information regarding the long-term impacts of oil, 

dispersant, and/or dispersed oil contamination on, and the location of, archaeological resources in 

the GOM. There are currently no published studies on the long-term impacts to archaeological 

resources exposed to oil, dispersant, or dispersed oil contamination. However, considering the low 

probability of an accidental oil spill contacting an archaeological site as a result of a proposed action, 

BOEM has determined that the information is not essential to a reasoned choice among alternatives.

Additionally, the locations of all archaeological resources in the GOM cannot be determined 

because the overall costs of obtaining that information through survey of the entire GOM are 

exorbitant. This incomplete information may be relevant to adverse impacts because the locations 

and integrity of many 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 archaeological resources, and the status of each, could be investigated, analyzed, and compiled. 

Archaeological sites within the GOM have the potential to be buried, embedded in, or laying on the 
Description of the Affected Environment and Impact Analysis 4-155

seafloor. The seafloor is comprised of highly variable bathymetric and geophysical regimes, which 

differentially affect the ease and ability to identify, ground truth, and evaluate archaeological sites. 

This fact, combined with the scope of the acreage within the GOM, results in the aforementioned 

exorbitant costs and time factors.

BOEM used existing information and reasonably accepted scientific theories on 

archaeological site potential in the Gulf of Mexico to extrapolate from available information in 

completing the relevant analysis. In addition, future site-specific, remote-sensing surveys of the 

seafloor, where required, establish the presence of potential resources (NTL 2005-G07, 

“Archaeological Resource Surveys and Reports”). 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 resources that are a 

part of the human environment. The survey data are analyzed by industry and BOEM’s 

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 effective in identifying resources to allow for mitigation application and protection 

of the resource during OCS oil- and gas-related activities. A 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 resource that could be affected by the proposed activity. 

Therefore, BOEM has determined that the gaps in information on the presence of or status of 

archaeological resources is not essential to a reasoned choice among alternatives at the lease sale 

stage.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including JSTOR, the National Technical Information 

Service’s National Technical Reports Library, and ScienceDirect) were examined to assess recent 

information regarding archaeological resources that may be pertinent to a proposed action. No new 

information that would add to the analyses or change the conclusions was discovered since 

publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for archaeological resources presented in the 

2017-2022 GOM Multisale EIS based on the information presented above. No new information was 

discovered that would alter the impact conclusion for archaeological resources presented in the 

2017-2022 GOM Multisale EIS, and the analysis and potential impacts detailed in that document still 

apply for the remaining proposed GOM lease sales in the Five-Year Program. 
4-156 2018 Gulf of Mexico Supplemental EIS

4.14 HUMAN RESOURCES AND LAND USE

4.14.1 Land Use and Coastal Infrastructure

Summary

BOEM has reexamined the analysis for land use and coastal infrastructure presented in the 

2017-2022 GOM Multisale EIS. No new information was discovered that would alter the impact 

conclusion for land use and coastal infrastructure presented in the 2017-2022 GOM Multisale EIS. 

Further, the analysis and potential impacts detailed in that document still apply for the remaining 

proposed GOM lease sales in the Five-Year Program. 

A detailed description of land use and coastal infrastructure, along with the full analyses of 

the potential impacts of routine activities, accidental events, and cumulative impacts associated with 

a proposed action are presented in Chapter 4.14.1 of the 2017-2022 GOM Multisale EIS. The 

following information is a summary of the resource description and impact analysis incorporated 

from the 2017-2022 GOM Multisale EIS.

Introduction

Along the Gulf Coast, from the southern tip of Cameron County, Texas, to the Florida Keys, 

23 BOEM-defined Economic Impact Areas (EIAs) are identified for the Gulf of Mexico region. The 

counties and parishes that form the EIAs are listed and the EIAs are visually illustrated in 

Figure 4-11. The EIAs geographically link together not only counties and parishes immediately 

adjacent to the GOM but also those tied to coastal counties and parishes as parts of functional 

economic areas. An analysis that encompasses where people live, as well as where they work, 

permits a more meaningful assessment of the impact of offshore oil and gas activities. The OCS 

oil- and gas-related activities draw on existing infrastructural, economic, and labor capacity from 

across the GOM region. BOEM’s analysis considers the potential impacts in all 23 EIAs regardless 

of where a proposed action may take place.
Description of the Affected Environment and Impact Analysis

4-157

Figure 4-11. Economic Land Use Patterns. 
4-158 2018 Gulf of Mexico Supplemental EIS

Analysis

For land use and coastal infrastructure, a proposed action would involve all of the Gulf Coast 

States: Texas; Louisiana; Mississippi; Alabama; and Florida. Particular emphasis is placed on the 

133 counties and parishes that constitute the 23 BOEM-identified EIAs and are located in the coastal 

areas of all five states. This geographic area is broadly diverse in types of land use and distribution 

of coastal infrastructure related to OCS oil- and gas-related activities. Some counties and parishes 

are more closely connected to the offshore oil and gas industry than others, such as Harris County, 

Texas, and Lafourche Parish, Louisiana. Figures 3-9, 3-11, and 3-12 of the 2017-2022 GOM 

Multisale EIS illustrate the analysis area’s key infrastructure.

Impacts to land use and coastal infrastructure may be positive as well as negative. For 

example, increased economic demand for services provided by infrastructure facilities would lead to 

more hiring, and this additional employment would further the positive economic trend as new 

workers spend their wages in the community. The affected environment and analyses supporting 

these conclusions are discussed below. BOEM has concluded that the selection of Alternative E 

would result in negligible impacts. Cumulative impacts of current and past activities, however, would 

continue to occur under Alternative E.

Impact-Level Definitions

• Beneficial – Positive impacts in the form of maintaining current employment 

levels, creating new employment, indirect and induced positive impacts through 

increased spending, and stimulating local and regional economies.

• Negligible – Little or no measureable adverse impact.

• Minor – Small-scale measurable adverse impact, temporary in duration and 

geographically small area (less than county/parish level).

• Moderate – Medium-scale measurable adverse impact and may last from a few 

weeks to 1 year and geographically may affect multiple counties/parishes.

• Major – Large-scale measurable or potentially unmeasurable adverse impact, 

long-lasting (1 year to many years), and may occur over a geographically large 

regional area. 

The impacts of each impact-producing factor for Alternatives A through D are summarized in 

Table 4-23 to help the reader quickly identify the level of potential impacts for each impact-producing 

factor using the impact-level definitions below.
Description of the Affected Environment and Impact Analysis 4-159

Table 4-23. Land Use and Coastal Infrastructure Impact-Producing Factors That Are Reasonably 

Foreseeable. 

Land Use and Coastal 

Infrastructure Magnitude of Potential Impact1

Impact-Producing Factors Alternative A Alternative B Alternative C Alternative D

Routine Activities

Changes in the Level of OCS 

Exploration, Development, and 

Production Activities

Negligible to Negligible to Negligible to Negligible to

Moderate Moderate Moderate Moderate

Expansions of Existing 

Infrastructure

Minor to Minor to Minor to Minor to

Moderate Moderate Moderate Moderate

New Infrastructure Facility 

Construction

Minor to Minor to Minor to Minor to

Moderate Moderate Moderate Moderate

Onshore Waste Disposal Negligible to Negligible to Negligible to Negligible to

Minor Minor Minor Minor

Navigation Channel 

Maintenance Dredging

Negligible to Negligible to Negligible to Negligible to

Minor Minor Minor Minor

Accidental Events

Oil Spills (coastal and offshore) Negligible to Negligible to Negligible to Negligible to

Moderate Moderate Moderate Moderate

Chemical/Drilling-Fluid Spills Negligible to Negligible to Negligible to Negligible to

Moderate Moderate Moderate Moderate

Spill Response Negligible to Negligible to Negligible to Negligible to

Moderate Moderate Moderate Moderate

Vessel Collisions Negligible to Negligible to Negligible to Negligible to

Moderate Moderate Moderate Moderate

Cumulative Impacts

Incremental Contribution2 Minor Minor Minor Minor

OCS Oil and Gas3 Beneficial to

Moderate

Non-OCS Oil and Gas4 Beneficial to

Major

1 The analysis supporting these conclusions is discussed in detail in the “Environmental Consequences” 

section in Chapter 4.14.1 of the 2017-2022 GOM Multisale EIS.

2 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) as a result of a single proposed lease sale in the 2017-2022 Five-Year Program.

3 This includes all activities (i.e., routine activities projected to occur and accidental events that could 

occur) from past, proposed, and future lease sales.

4 This includes other past, present, and reasonably foreseeable future activities occurring within the 

same geographic range and within the same timeframes as a proposed action, but they are not related 

to the OCS Oil and Gas Program.

A current snapshot of land use and coastal infrastructure in the GOM reveals a diverse social 

and economic landscape, with the oil and gas industry playing a substantially larger role in some 

states (i.e., Texas and Louisiana) than in the rest of the GOM. The oil and gas industry has 
4-160 2018 Gulf of Mexico Supplemental EIS

developed across the region over many decades and is intimately intertwined with its socioeconomic 

structure. This complex structure involves both offshore (i.e., Federal OCS and State waters) and 

onshore (i.e., private land, and State and Federal onshore lands) exploration, development, and 

production activities, complicating the environmental impact analysis because it is very difficult, if not 

impossible, to separate the impacts of Federal OCS oil- and gas-related activities from those of oil 

and gas activities in State waters and onshore, or foreign imports.

Oil and gas exploration, production, and development activities on the OCS are supported by 

an expansive onshore network of coastal infrastructure that includes large and small companies 

providing a wealth of services from construction facilities, service bases, and waste disposal facilities 

to crew, supply, and product transportation, as well as processing facilities. Chapter 3.1.2.2

summarizes coastal infrastructure scenario projections, and Chapter 3.1.5.3 of the 2017-2022 GOM 

Multisale EIS describes onshore waste disposal. More detail on coastal infrastructure can be found 

in Chapter 3.1.7 of the 2017-2022 GOM Multisale EIS. A description of the affected environment 

covers land use in the area and different infrastructure categories that support thousands of jobs. 

These jobs represent direct, indirect, and induced economic impacts that ripple through the Gulf 

Coast economy. As a long-standing part of the regional economy that developed over the past 

several decades, the coastal infrastructure network is quite mature in the Gulf of Mexico region.

Because OCS oil- and gas-related activities are supported by a long-lived, expansive 

onshore network of coastal infrastructure that includes hundreds of large and small companies, 

routine operations associated with a proposed action are not expected to produce any major impacts 

to land use and coastal infrastructure. Potential impacts from routine operations could range from 

negligible to moderate, depending on the location, scale, and type of activity. The impacts of 

reasonably foreseeable accidental events such as oil spills, chemical and drilling fluid spills, and 

vessel collisions are not likely to last long enough to adversely affect overall land use or coastal 

infrastructure in the analysis area and would therefore be negligible to moderate. For a detailed 

analysis of a high-impact, low-probability catastrophic oil spill, refer to the Catastrophic Spill Event 

Analysis white paper (USDOI, BOEM, 2017b).

The cumulative analysis includes impacts that could result from a proposed lease sale 

combined with baseline conditions, all past, present, and future Federal OCS oil- and gas-related 

lease sales and activities, as well as all past, present, and reasonably foreseeable future actions that 

are external to Federal OCS oil- and gas-related activities. Activities relating to all past, present, and 

future OCS oil- and gas-related activities are expected to minimally affect the current land use of the 

analysis area because most subareas have strong industrial bases and designated industrial parks. 

Non-OCS oil- and gas-related factors contribute substantially to the cumulative impacts on land use 

and coastal infrastructure, while only a minor incremental contribution is expected for a proposed 

action.
Description of the Affected Environment and Impact Analysis 4-161

Comparison of Alternatives

For any of the action alternatives (i.e., Alternatives A, B, C, and D), the cumulative impacts 

on land use and coastal infrastructure could range from beneficial to moderate for OCS oil- and 

gas-related activities and beneficial to major for non-OCS oil- and gas-related activities, depending 

on the specifics of each situation, whether the impacts are measurable, how long the impacts would 

last, and the size of the affected geographic area as defined in Chapter 4.14.1 of the 2017-2022 

GOM Multisale EIS. Alternative E would result in no lease sale and, thus, the direct impacts as a 

result of a proposed lease sale woud be none, and there would be no incremental contribution of 

impacts to land use and coastal infrastructure beyond a temporary negative economic impact for the 

oil and gas industry and coastal states, such as Louisiana, that are more dependent on oil and gas 

revenues. Cumulative impacts of current and past activities (i.e., OCS oil- and gas-related and 

non-OCS oil- and gas-related), however, would continue to occur under this alternative.

Incomplete or Unavailable Information

BOEM has identified incomplete information regarding the potential impacts of coastal land 

loss on land use and coastal infrastructure. This incomplete information may be relevant to adverse 

impacts because it is not completely known how current subsidence and erosion is affecting industry 

or what plans industry is making to mitigate current or future impacts. Because there are hundreds 

of large and small property-owning businesses spread across the coastal zone, which directly and 

indirectly support the offshore petroleum industry, the identity of these properties and the 

possibilities of losses due to subsidence, sea-level rise, and erosion cannot be quantified at this 

time.

BOEM has employed reasonably accepted scientific methodologies to extrapolate from 

existing information on dredged material and other approaches used to mitigate for land loss in

completing its analysis and formulating the conclusions presented here. For a more detailed 

discussion on deltaic land loss, refer to Chapter 4.3.2 (“Coastal Barrier Beaches and Associated 

Dunes”). In the case of coastal ports, for example, 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). This example shows that, although BOEM does not possess a complete 

understanding of what industrial infrastructure improvements may occur, such as mitigation for land 

loss, industry would most likely mitigate as necessary to protect existing and growing infrastructure. 

With each passing year, the pressure increases to take action and protect critical oil and gas 

infrastructure (Traywick, 2016). Like any industrial infrastructure improvements, future adaptations 

would occur on an as-needed basis or as new technologies become available. Given that coastal 

infrastructure will continue to be subject to the impacts of coastal land loss and routine tropical storm 

activity, there will also continue to be considerable motivation to protect existing infrastructure. 

Therefore, BOEM has determined that the information is not essential to a reasoned choice among 

alternatives. BOEM continues to monitor the industry and its infrastructure footprint over time to 

document short- and long-term impacts of continued land loss.
4-162 2018 Gulf of Mexico Supplemental EIS

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including USDHS, Federal Emergency Management 

Agency; USDOC, Bureau of the Census; USDOC, NOAA; USDOE, Energy Information 

Administration; USDOT, Maritime Administration; USDOI, FWS; RestoreTheGulf.gov website; 

USEPA; Louisiana Department of Environmental Quality; Louisiana Recovery Authority; Louisiana

Office of Community Development; Mississippi Department of Environmental Quality; Alabama 

Department of Environmental Management; State of Florida Department of Environmental 

Protection; 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) were examined to assess recent information 

regarding land use and coastal infrastructure that may be pertinent to a proposed action. No new 

information that would add to the analyses or change the conclusions was discovered since 

publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for land use and coastal infrastructure presented in the 

2017-2022 GOM Multisale EIS, with the understanding that no new information on land use and 

coastal infrastructure has been published since the publication of the 2017-2022 GOM Multisale EIS. 

Therefore, no new information was discovered that would alter the impact conclusion for land use 

and coastal infrastructure presented in that document, and the analysis and potential impacts 

detailed in the 2017-2022 GOM Multisale EIS still apply for the remaining proposed GOM lease 

sales in the Five-Year Program. 

4.14.2 Economic Factors

Summary

BOEM has reexamined the analysis for economic factors presented in the 2017-2022 GOM

Multisale EIS based on the additional information presented below. No new information was 

discovered that would alter the impact conclusion for economic factors presented in the 2017-2022 

GOM Multisale EIS. The analysis and potential impacts detailed in that document still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. 

A detailed description of economic factors, along with the full analyses of the potential 

impacts of routine activities, accidental events, and cumulative impacts associated with a proposed 

action are presented in Chapter 4.14.2 of the 2017-2022 GOM Multisale EIS. The following 

information is a summary of the resource description and impact analysis incorporated from the 

2017-2022 GOM Multisale EIS.

Introduction

Economic factors are factors that explain and quantify the human behaviors that determine 

the positive and negative impacts from the alternatives. Chapter 4.14.2.1 of the 2012-2022 GOM 
Description of the Affected Environment and Impact Analysis 4-163

Multisale EIS provides detailed economic and demographic data for Gulf of Mexico EIAs, provides 

background research regarding the offshore oil and gas industry, and presents data from the Office 

of Natural Resources’ revenue regarding sales volumes, sales values, and revenues received from 

offshore oil and gas activities.

Analysis

This chapter discusses the routine activities, accidental events, and cumulative impacts to 

economic factors that would arise from the alternatives. Many of the economic impacts of the 

alternatives would be beneficial, and these impacts are stated in terms of standard measures of 

economic activity. The negative impacts are measured in terms of the severity, duration, and 

geographical extent of impacts. Long-term impacts are those lasting more than 1 year. Extensive 

impacts are those that affect numerous economic impact areas. Severe impacts cause sizeable 

impacts to economic activity in levels or relative to the size of an economic impact area.

Impact-Level Definitions

In this chapter the impact levels are defined in terms of the intensity, duration, and 

geographical extent of the impacts to the human uses of economic factors along the Gulf Coast.

• Beneficial – Positive impacts stated in levels and percentages of employment 

(number of jobs), labor income (wages, benefits, and sole-proprietor income), 

and/or value-added (contribution to gross regional product).

• Negligible – Little or no detectable adverse impact.

• Minor – Adverse impacts are detectable but less than severe.

• Moderate – Adverse impacts are severe but are short-term and/or not extensive.

• Major – Adverse impacts are long-term (more than 1 year), extensive, and 

severe.

A proposed action would lead to beneficial (low) impacts arising from industry expenditures, 

government revenues, corporate profits, and other market impacts. Some of these impacts would 

be concentrated along the Gulf Coast, while others would be widely distributed. A proposed action 

could also lead to negative economic impacts (negligible to minor) arising from accidental events 

and disruptions to other industries. There would be some differences in economic impacts among 

the alternatives, corresponding to the differences in the scales and distributions of likely activities. 

Chapter 4.14.2 of the 2017-2022 GOM Multisale EIS presents detailed estimates of the economic 

impacts of the alternatives. A full analysis of economic factors can be found in Chapter 4.14.2 of the 

2017-2022 GOM Multisale EIS.
4-164 2018 Gulf of Mexico Supplemental EIS

Comparison of Alternatives

The alternatives should be viewed in light of the OCS Program, as well the numerous forces 

that can affect energy markets and the overall economy. Most of the incremental economic impacts 

of a proposed action are forecast to be beneficial (low), although there would be some minor

adverse impacts that may occur as a result of accidental events. The exact impacts will be roughly 

proportional to the amount of resulting oil and gas industry activity that occurs as a result of a 

proposed action. While there are some differences in the amount of activities associated with the 

alternatives, many of the impacts associated with the alternatives are similar because the types of 

activities that occur are similar and the differences are not large enough to change the range of 

impact conclusions. Alternative E, the cancellation of a proposed lease sale, would negatively 

impact firms and employees that depend on recurring leases; therefore, the impacts of Alternative E 

would be negligible to minor, with some partially offsetting beneficial impacts. Cumulative impacts 

of current and past activities (i.e., OCS oil- and gas-related and non-OCS oil- and gas-related), 

however, would continue to occur under this alternative.

Incomplete or Unavailable Information

Even after evaluating the information above, 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 the impacts 

from routine activities, accidental events, 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. In addition, standard data sources do not trace revenue and corporate profit streams 

to ultimate expenditures. BOEM used reasonably accepted scientific methodologies to extrapolate 

from existing information in completing the relevant analysis and formulating the conclusions 

presented here. For example, BOEM used the model MAG-PLAN to estimate the impacts of the 

alternatives and 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, while relevant, is not essential to a reasoned choice among alternatives.

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various sources (including Internet searches regarding economic developments) were 

examined to assess recent information regarding economic factors that may be pertinent to a 

proposed action. No new information that would add to the analyses or change the conclusions was 

discovered since publication of the 2017-2022 GOM Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for economic factors presented in the 2017-2022 GOM

Multisale EIS, with the understanding that no new information on economic factors has been 

published since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information 

was discovered that would alter the impact conclusion for economic factors presented in that 
Description of the Affected Environment and Impact Analysis 4-165

document, and the analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still 

apply for the remaining proposed GOM lease sales in the Five-Year Program. 

4.14.3 Social Factors (Including Environmental Justice)

Summary

BOEM has reexamined the analysis for social factors presented in the 2017-2022 GOM 

Multisale EIS. No new information was discovered that would alter the impact conclusion for social 

factors presented in the 2017-2022 GOM Multisale EIS. Further, the analysis and potential impacts 

detailed in that document still apply for the remaining proposed GOM lease sales in the Five-Year 

Program. 

A detailed description of social factors, along with the full analyses of the potential impacts of 

routine activities, accidental events, and cumulative impacts associated with a proposed action are 

presented in Chapter 4.14.3 of the 2017-2022 GOM Multisale EIS. The following information is a 

summary of the resource description and impact analysis incorporated from the 2017-2022 GOM 

Multisale EIS. An environmental justice determination follows in Chapter 4.14.3.1. 

Introduction

The affected environment that comprises the baseline for the social factors’ environmental 

impact analysis is geographically distributed across 23 BOEM-identified EIAs in all five Gulf Coast 

States. Figure 4-12 shows the aggregation of 133 counties and parishes that comprise the EIAs. 

Chapter 4.14.2 (“Economic Factors”) discusses the methodology behind the development of the 

EIAs and employment in the analysis area.

Analysis

The petroleum industry as a whole in the Gulf of Mexico region has matured over several 

decades and is well-developed, expansive, extensive, and deeply intertwined in the regional 

communities and economies of the five coastal states, i.e., Texas, Louisiana, Mississippi, Alabama, 

and Florida. An inherent complication in conducting an impact analysis of OCS oil- and gas-related 

activities lies in the fact that the industry involves exploration, development, and production located 

on private and public lands onshore, State waters offshore, and on the Federal OCS. This 

long-lived, well-developed, and extensive industry functions within a much larger context, a 

socioeconomic framework that weaves through the region in a complex, inter-connected grid-like 

manner. Nothing occurs as an isolated event, but rather results from and simultaneously triggers 

other events, all of which are experienced at varying degrees of negative or positive impact. For 

example, when oil prices drop and then gasoline prices drop, this positively impacts individuals and 

businesses who buy fuel. When oil prices remain low for many months, negative impacts begin to 

appear. Oil and gas companies start reducing the number of employees to cut operational costs. 

Laid-off employees no longer have income to make purchases and the businesses where workers 

would normally spend their money began to suffer and, when necessary, people began moving out 

of the area to find other work, leading to a negative impact on the housing market, depressing real 
4-166 2018 Gulf of Mexico Supplemental EIS

estate prices as the number of units available for rent or sale outgrows the demand. A negative 

impact for some (i.e., sellers and landlords) becomes a positive impact for others (i.e., buyers and 

renters). This is just one example of an event leading to dual ripple impacts (negative and positive) 

through communities and illustrates the complexity of the socioeconomic framework.

Within this context, and in the cumulative analysis, a single proposed lease sale is like a blip 

on a radar screen, one tiny piece of a vastly complex social and economic structure. A single 

proposed lease sale’s main impact on communities would be to contribute to the maintenance of 

current employment levels; not to create new jobs; not to cause a notable increase of people to 

move into the region; not to cause new roads, schools, or hospitals to be built; and not to cause 

large public works improvements. A single proposed lease sale would help to maintain what 

decades of economic development have built, the complex Gulf of Mexico region that exists today.

While this chapter is titled “social factors,” the resource discussed here is essentially human 

beings. The list of potential impact-producing factors is, in a sense, nearly limitless because the 

industry involves people at all levels; it simultaneously affects and is affected by people, their 

communities, and their daily lives. Most of the impacts to people are positive, e.g., in the form of 

direct employment in the industry, indirect employment in the extensive support sectors, and 

employees’ spent wages and tax revenues that support community businesses and local 

governments.

Impact-Level Definitions

Impacts to people and communities may be positive as well as negative. For example, 

increased economic demand would lead to more hiring, and this additional employment would 

further the positive economic trend as new workers spend their wages in the community. The 

definitions below define the impact levels for this analysis.

• Beneficial – Positive impacts such as any of the following: measurable 

beneficial effects such as maintaining current employment levels; creating new 

employment; and indirect and induced positive impacts through increased 

spending that stimules local and regional economies.

• Negligible – Little or no measureable adverse impact.

• Minor – Small-scale measurable adverse impact, temporary in duration, and 

geographically small area (less than county/parish level).

• Moderate – Medium-scale measurable adverse impact, may last from a few 

weeks to 1 year, and geographically may affect multiple counties/parishes.

• Major – Large-scale measurable or potentially unmeasurable adverse impact, 

long lasting (1 year to many years), and may occur over a geographically large 

regional area.
Description of the Affected Environment and Impact Analysis

4-167

Figure 4-12. Population of BOEM’s Economic Impact Areas in the Gulf of Mexico.
4-168 2018 Gulf of Mexico Supplemental EIS

A regionwide proposed lease sale is the preferred alternative and, just like planning area 

specific lease sales, involves all of the Gulf Coast States, i.e., Texas, Louisiana, Mississippi, 

Alabama, and Florida because the onshore effects operate independently of the boundaries of 

offshore planning areas. Particular emphasis is placed on the 133 counties and parishes that 

constitute the 23 BOEM-identified EIAs and that are located in the coastal areas of all five states. 

Figure 4-11 shows the aggregation of counties and parishes into the EIAs used for BOEM’s 

socioeconomic analysis. This geographic area possesses a culturally and racially diverse 

population. Some counties and parishes are more closely connected to the offshore oil and gas 

industry than others, particularly Harris County, Texas, and Lafourche Parish, Louisiana.

Analysis of the various alternatives considers impact-producing factors within a distinct

framework that includes frequency, duration, and geographic extent. Frequency (i.e., rare, 

intermittent, and continuous) refers to how often the impact-producing factor occurs over the entire 

analysis period of 50 years for routine activities and accidental events and for an analysis period of 

70 years for cumulative impacts. Duration (i.e., low, medium, and high) refers to how long the 

impact-producing factor lasts (i.e., from less than a year to many years). Geographic extent refers to 

which areas are affected and, depending on the impact-producing factor, the size of an affected 

area.

Potential social impacts resulting from a proposed action would occur within the larger 

socioeconomic context of the GOM region. The affected environment of the analysis area is quite 

large geographically and in terms of population (133 counties and parishes with over 22.7 million 

residents). The impacts from routine activities related to a proposed action are expected to be 

negligible to moderate, widely distributed, and to have little impact because of the existing 

extensive and widespread support system for the petroleum industry and its associated labor force. 

Outside of a low-probability catastrophic oil spill, which is not reasonably foreseeable and not part of 

a proposed action, any potential accidental events are not likely to be of sufficient scale or duration 

to have adverse and disproportionate long-term impacts for people and communities in the analysis 

area and would therefore range from negligible to moderate. In the cumulative analysis, impacts 

from OCS oil- and gas-related activities would range from beneficial to moderate. Non-OCS 

oil- and gas-related factors, which include all human activities, natural events, and processes, 

actually contribute more to cumulative impacts than do factors related to OCS oil- and gas-related 

activities alone and result in beneficial to major impacts. The incremental contribution of a 

proposed action to cumulative impacts would be minor. Alternative E would result in no lease sale 

and, thus, the overall incremental impacts as a result of Alternative E would be none. Cumulative 

impacts of current and past activities (i.e., OCS oil- and gas-related and non-OCS oil- and 

gas-related), however, would continue to occur under this alternative. For a detailed analysis of a 

high-impact, low-probability catastrophic oil spill, refer to the Catastrophic Spill Event Analysis white 

paper (USDOI, BOEM, 2017b).

Coastal populations experience cumulative impacts that include all human activities and 

natural processes and events. The cumulative analysis includes impacts that could result from a 

proposed lease sale combined with baseline conditions, all past, present, and future Federal OCS 
Description of the Affected Environment and Impact Analysis 4-169

oil- and gas-related lease sales and activities, as well as all past, present, and reasonably 

foreseeable future actions that are external to Federal OCS oil- and gas-related activities. Within 

this divided analytical framework of OCS oil- and gas-related and non-OCS oil- and gas-related 

impacts, the largest quantity of impact-producing factors for coastal populations occur as non-OCS 

oil- and gas-related impacts because OCS oil- and gas-related activities form a very small part of the 

greater, complex socioeconomic structure in the GOM. The incremental contribution to cumulative 

impacts of a proposed action, i.e., a single regionwide lease sale, would be minor for communities 

and people in the Gulf Coast region.

Comparison of Alternatives

The impacts for social factors would be similar for Alternatives A, B, C, and D; however, the 

level of impacts would be directly related to the level of OCS oil- and gas-related activity in the Gulf 

of Mexico. Alternative B would produce proportionately smaller OCS oil- and gas-related activity 

than Alternative A, and Alternative C would result in less OCS oil- and gas-related activity than 

Alternative A or B. The impacts of Alternative D could be less than Alternative A, B, or C, but this 

difference would likely be indiscernible. Under Alternative E, there would be no new activities 

associated with a proposed lease sale; however, activities associated with past lease sales and nonOCS oil- and gas-related activities would continue.

Incomplete or Unavailable Information

BOEM has identified unavailable information that is relevant to people and communities 

regarding the impacts of the Deepwater Horizon explosion, oil spill, and response. This information 

cannot be obtained because long-term health impact studies, subsistence studies, and the NRDA 

process are ongoing, and data from these efforts would be unavailable and unobtainable for some 

time. In order to fill this data gap, BOEM has used existing information and reasonably accepted 

scientific methodologies to extrapolate from available information in completing the relevant analysis, 

including 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 a proposed lease sale and not likely expected to occur, may have adverse 

impacts on residents in GOM coastal communities. Research into possible long-term health impacts 

of the Deepwater Horizon explosion, oil spill, and response continues (National Institute of 

Environmental Health Science, 2014; National Center for Disease Preparedness, 2013 and 2014; 

Substance Abuse and Mental Health Services Administration and Centers for Disease Control and 

Prevention, 2013). Because long-term health impacts to coastal populations are unknown, this 

information may be relevant to the evaluation of impacts from the Deepwater Horizon explosion, oil 

spill, and response; therefore, BOEM would continue to seek additional information as it becomes 

available and bases the previous analysis on the best information currently available. Although 

long-term health impacts to people and communities may be relevant to this analysis, BOEM has 

determined that the unavailable information is not essential to a reasoned choice among alternatives 

based on the information discussed above.
4-170 2018 Gulf of Mexico Supplemental EIS

New Information Available Since Publication of the 2017-2022 GOM Multisale EIS

Various printed and Internet sources (including peer-reviewed research publications, 

U.S. Department of Health and Human Services, National Institutes of Health; USEPA; USDOC, 

Bureau of the Census and Bureau of Labor Statistics; USDHS, Federal Emergency Management 

Agency; USDOE, Energy Information Administration; RestoreTheGulf.gov website; 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; and Oil and Gas Journal) were examined to assess recent information regarding social 

factors that may be pertinent to a proposed action. No new information that would add to the 

analyses or change the conclusions was discovered since publication of the 2017-2022 GOM 

Multisale EIS. 

Conclusion

BOEM has reexamined the analysis for social factors presented in the 2017-2022 GOM

Multisale EIS, with the understanding that no new information on social factors has been published 

since the publication of the 2017-2022 GOM Multisale EIS. Therefore, no new information was 

discovered that would alter the impact conclusion for social factors presented in that document, and 

the analysis and potential impacts detailed in the 2017-2022 GOM Multisale EIS still apply for the 

remaining proposed GOM lease sales in the Five-Year Program. 

4.14.3.1 Environmental Justice Determination

Executive Order 12898, “Federal Actions to Address Environmental Justice in Minority 

Populations and Low-Income Populations,” directs Federal agencies to make a determination as to

whether their actions have disproportionate environmental impacts on minority or low- income

people. These environmental impacts encompass human health, and social and economic 

consequences. In 1997, President Clinton issued Executive Order 13045, “Protection of Children 

from Environmental Health Risks and Safety Risks,” directing Federal agencies to identify and 

assess environmental health risks and safety risks of its policies, programs, and activities that

may disproportionately affect children. In accordance with NEPA and the Executive Orders,

BOEM provides opportunities for community input during the NEPA process. 

One example of BOEM’s efforts to foster an inclusive and transparent public process are the 

meetings that BOEM has held with the Vietnamese fisherfolk community in Mississippi at the 

Vietnamese fisherfolk community’s request. BOEM provided Vietnamese translations of relevant 

portions of the 2017-2022 GOM Multisale EIS to maximize participation. Additional avenues of 

public outreach employed by BOEM include specific types of notices that are (1) mailed to public 

libraries; interest groups; industry; ports and docks; 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. The formal scoping process is initiated by the publication of a 
Description of the Affected Environment and Impact Analysis 4-171

Notice of Intent, and public scoping meetings are held in several geographically separate cities to 

allow the public to submit comments and to identify all stakeholders’ concerns. 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 5.3. A summary of the scoping 

comments for this Supplemental EIS can be found in Chapter 5.3.1. 

In accordance with 40 CFR §§ 1508.7 and 1508.8, BOEM has considered potential 

cumulative, direct, and indirect impacts to minority and low-income populations in the analysis area. 

Furthermore, in reaching this considered environmental justice determination, BOEM utilized 

guidance from the Council on Environmental Quality (CEQ, 1997), the U.S. Environmental 

Protection Agency (USEPA, 1998) and the Federal Interagency Working Group on Environmental 

Justice & NEPA Committee (2016). The OCS lease sales occur in Federal waters 3 nmi (3.5 mi;

5.6 km) or 9 nmi (10.4 mi; 16.7 km) from shore. Thus, the permitted activities of petroleum 

exploration, extraction, and production that occur on these leaseholds are distant from human

habitation, and these activities would not have any direct impacts on low-income and minority 

populations. State offshore oil and gas leasing occurs in waters closer to land were petroleumrelated activities are generally viewed as having a greater potential for directly impacting 

coastal communities. Indirect impacts to minority and low-income populations could occur onshore, 

and would result from the operations of the extensive infrastructure system that supports all 

onshore and offshore oil and gas activities. This downstream infrastructure moves hydrocarbon 

product to market and includes gas processing facilities, petrochemical plants, transportation 

corridors, petroleum bulk storage facilities, and gas and petroleum pipelines. These facilities 

comprise a mature, widespread and concentrated infrastructure system (refer to Chapter 4.14.1). 

Much infrastructure is located in coastal Louisiana and Texas, and to a lesser extent in

Mississippi’s Jackson County and Alabama’s Mobile County. While many fabrication and supply 

facilities are concentrated around coastal ports, downstream processing is concentrated in

industrial corridors farther inland (Dismukes, 2011b; Kaplan et al., 2011). The onshore 

downstream infrastructure exists to support all oil- and gas-related activities (i.e., onshore, offshore, 

and imported product), and the proportion of Federal OCS contribution to downstream infrastructure 

use has not yet and, most likely, may never be possible to determine as it is dependent on highly 

unpredictable market demands and prices.

Potential environmental justice impacts that may arise from downstream support activities 

cannot be influenced by BOEM’s decisionmaking because BOEM has no regulatory authority over

any onshore activities, including their location. Many other Federal and State agencies regulate 

onshore oil and gas infrastructure. Therefore, BOEM has determined that a proposed lease sale 

would not adversely affect minority and low-income populations.

4.15 UNAVOIDABLE ADVERSE IMPACTS OF A PROPOSED ACTION

Unavoidable adverse impacts associated with a 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 part of a proposed action and not likely expected to occur, could 
4-172 2018 Gulf of Mexico Supplemental EIS

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. Cumulatively, 

however, a multitude of individual projects results in a major use of OCS space.

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. Mitigation of long-term impacts from 

offshore engine combustion during routine operations would be accomplished through existing 

regulations and the development of new control emission technology. Short-term impacts from spill 

events could occur and are likely to be aggravated or mitigated by the time of year the spills take 

place.

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. Impacts from these activities would be reduced through existing 

NPDES regulations. 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 spill would subject 

the 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 

nonpoint-source 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.

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, and a 

beach could experience several years of small surface residue balls (also called 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 
Description of the Affected Environment and Impact Analysis 4-173

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 (organisms growing) 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 a proposed action.

Offshore Biological Habitats: Unavoidable adverse impacts would take place if an oil spill 

occurred and contacted 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.

Fish and Invertebrate Resources: Unavoidable adverse impacts from routine operations 

would take place from discharges from vessels and platforms. These would be 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 impacts on fish.

Birds: Unavoidable adverse impacts from routine operations on birds could result from 

noise, helicopter and OCS service-vessel traffic, coastal facility and platform lighting, and floating 

trash and debris. Trans-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 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. 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 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 impacts of the spill and also 

disruption from oil-spill cleanup activities. 

Threatened and Endangered Species: Because a proposed 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 
4-174 2018 Gulf of Mexico Supplemental EIS

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, as described in 

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.

Marine Mammals: Unavoidable adverse impacts to 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 calving grounds.

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. If a large oil spill occurs, 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 Resources: 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 resources, 

leading to local or regional economic losses and stigma effects, causing potential users to avoid the 

area after acute impacts have been removed. Some recreational resources become temporarily 

soiled by weathered crude oil, and small surface residue balls (also called tarballs) may come 

ashore long after stranded oil has been cleaned from shoreline areas. Impacts on recreational 

resources 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: 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. It is BOEM’s policy to not approve any EP or DOCD plan with known or potential 

archaeological resources within 500 ft (152 m) of the planned activity or a pipeline application with 

known or potential archaeological resources within the pipeline corridor or right-of-way (the 200-ft 

[61-m] corridor in which the pipeline is to be constructed). For decommissioning activities, all known 

or potential (i.e., side-scan sonar targets) archaeological resources must be investigated before site 

clearance activities take place and, if the presence of archaeological resources is confirmed, 

exceptions to the site clearance requirements at that location would be granted. Complete 
Description of the Affected Environment and Impact Analysis 4-175

archaeological data recovery (excavation) would be required if BOEM decided that a permitted 

activity must take place that would cause an adverse impact to an archaeological resource.

Economic and Social Factors: Net economic, political, and social benefits to the U.S. 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 spill-response 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. 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 

drop-off of activity as operators adjust to new expectations or use the opportunity to move resources 

to other basins where they have interests.

4.16 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.

4.16.1 Coastal Habitats

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 dieback 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. Regulatory requirements of the State and Federal water authorities and some local 

jurisdictions would be applicable to these activities to mitigate these impacts. Ongoing natural and 

anthropogenic processes in the coastal zone, only one of which is an 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.

4.16.2 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, 
4-176 2018 Gulf of Mexico Supplemental EIS

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.

4.16.2.1 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.

4.16.2.2 Fish and Invertebrate Resources, Deepwater Benthic Communities, Commercial 

Fisheries, and Recreational Fishing

Irreversible loss of fish and invertebrate resources, including commercial and recreational 

species, may be caused by structure removals 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. However, the Rigs-to-Reef 

Program would help offset these impacts.

4.16.3 Archaeological Resources

Any loss of undiscovered archaeological resources on or below the seafloor of the OCS in 

developed areas would be an irreversible and irretrievable commitment of resources. 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. An 

archaeological survey, avoidance through development design, documentation, and/or other 

mitigation would be accomplished prior to development, so as to minimize impacts.

4.16.4 Oil and Gas Development

Leasing and subsequent development and extraction of hydrocarbons as a result of a 

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 a proposed action is presented in Chapter 3.1.2. 

4.16.5 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 
Description of the Affected Environment and Impact Analysis 4-177

accidents, accidents caused by human negligence or misinterpretation, human error, 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.

4.17 RELATIONSHIP BETWEEN THE SHORT-TERM USE OF MAN’S ENVIRONMENT AND 

THE MAINTENANCE AND ENHANCEMENT OF LONG-TERM PRODUCTIVITY

The short-term impacts on various components of the environment in the vicinity of the 

proposed action are related to long-term impacts and the maintenance and enhancement of longterm productivity.

4.17.1 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 a proposed action would provide 

short-term 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 up to 0.211-1.118 BBO and 0.547-4.424 Tcf of gas from a proposed action. The 

impact scenario in this Supplemental EIS extends approximately from 2017 to 2066. The 50-year 

time period is used because it is the approximate longest life span of activities conducted on an 

individual lease. The 50 years following a proposed lease sale is the period of time during which the 

activities and impacting factors that follow as a consequence of a proposed lease sale would be 

influencing the environment.

The cumulative impact scenario in this Supplemental EIS extends from approximately 2017 

to 2086. The 70-year timeframe includes projected activity from (1) past lease sales for which 

exploration or development has either not yet begun or is continuing, (2) lease sales that would be 

held in the Five-Year Program, and (3) future lease sales that would be held as a result of future 

Five-Year Programs (four additional programs are included in this cumulative analysis). Activities 

that take place as a result of Five-Year Programs beyond the next four programs are not included in 

this analysis. The 70-year time period following a proposed lease sale is the period of time during 

which the activities and impacting factors that follow as a consequence of the cumulative impact 

scenario would be influencing the environment.

The specific impacts of a 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 
4-178 2018 Gulf of Mexico Supplemental EIS

and exploration drilling, result in short-term, localized impacts. Development drilling and well 

workovers occur sporadically throughout the life of a 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 impacts on physical, biological, and socioeconomic resources discussed in Chapter 4

are considered to be short term (being greatest during the construction, exploration, and early 

production phases). These impacts would be further reduced by the mitigating measures discussed 

in Chapter 2.2.4. 

The OCS development off Texas and Louisiana 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. 

A 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, but this could be offset 

by the Rigs-to-Reef program.

The short-term exploitation of hydrocarbons for the OCS Program in the Gulf of Mexico may 

lead to long-term impacts on biologically sensitive 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 (refer to 

Chapter 4.14).

4.17.2 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 BSEE estimates that oil production in the GOM peaked at 1.6 MMbbl/day in 2002, declined for a 

few years and then peaked again in 2009 and 2010 at 1.6 MMbbl/day before declining again. 

Production rates in 2015 indicate it was another high year (1.5 MMbbl/day), and gas production in 

the GOM peaked at 14.4 Bcf/day in 1997 and has declined since then to 3.6 Bcf/day in 2015 

(USDOI, BSEE, 2016b). Production has shifted from many smaller reserves on the continental shelf 

to fewer larger reserves in deep water. Large deepwater oil discoveries have the potential to alter 

the oil production rate, but the exact effect any one discovery would have or when that discovery 
Description of the Affected Environment and Impact Analysis 4-179

would be made is difficult to project due 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 gChlorophyll 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 be used as site-specific artificial reefs and fish-attracting devices for 

the benefit of commercial and recreational fishermen and for sport divers and spear fishers. 

Approximately 10 percent of the oil and gas structures removed from the OCS are eventually used 

for State artificial reef programs. Additionally, the OCS Program continues to improve the 

knowledge and mitigation practices used in offshore development to enhance the safe and 

environmentally responsible development of OCS oil and gas resources.

CHAPTER 5 

 

CONSULTATION AND COORDINATION

Consultation and Coordination 5-3 

What’s in This Chapter?

• BOEM is conducting consultation and other activities to comply with laws and Executive 

Orders.

• BOEM coordinated the prelease process with key agencies and organizations.

• The prelease and NEPA process has included publication of the Notice of Intent to Prepare 

an EIS (NOI).

• BOEM conducted internal and public scoping to determine the content of this 

Supplemental EIS.

− 441 comments were received during the scoping process.

• The National Park Service is a cooperating agency on this Supplemental EIS.

5 CONSULTATION AND COORDINATION

5.0 INTRODUCTION

BOEM is conducting consultation and other activities to comply with the following laws, 

including but not limited to, the following: the development of consistency determinations (CDs) 

under the Coastal Zone Management Act (CZMA); consultation under the Endangered Species Act 

(ESA) for potential impacts to listed species or designated critical habitat; completion of an Essential 

Fish Habitat assessment pursuant to the Magnuson-Stevens Fishery Conservation and 

Management Act; and a request for comments and consultation with federally recognized Indian 

Tribes pursuant to the National Historic Preservation Act and Executive Order 13175. Pursuant to 

NEPA, BOEM has conducted public involvement activities during scoping for the Draft Supplemental 

EIS. This chapter describes the processes with which BOEM worked with other Federal and State 

agencies, Tribal governments, and the public during the development of this Supplemental EIS.

5.1 COASTAL ZONE MANAGEMENT ACT

The Federal agency performs a consistency review pursuant to the CZMA, and CDs are 

prepared for each coastal State along the Gulf of Mexico with a federally approved Coastal 

Management Program (CMP) prior to each of the proposed lease sales. To prepare the CDs, 

BOEM reviews each State’s approved Coastal Management Plan and analyzes the potential impacts 

as outlined in the 2017-2022 GOM Multisale EIS and this Supplemental EIS, new information, and 

applicable studies as they pertain to the enforceable policies of each CMP. The CZMA requires that 

Federal actions that have reasonably foreseeable coastal effects (i.e., effects to any coastal use or 

resource of the coastal zone) be “consistent to the maximum extent practicable” with relevant 

enforceable policies or guidelines 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 States of Texas, Louisiana, 

Mississippi, Alabama, and Florida for proposed regionwide lease sales; to Texas and Louisiana for 

proposed WPA lease sales; or Louisiana, Mississippi, Alabama, and Florida for proposed CPA 

and/or EPA lease sales. If the State concurs, BOEM proceeds with the proposed lease sale. A 

State’s concurrence may be presumed when a State does not provide a response within the 60-day 
5-4 2018 Gulf of Mexico Supplemental EIS

review period. A 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 State objects, it 

must do the following under the CZMA:

(1) indicate how BOEM’s prelease proposal is inconsistent with the State’s federally 

approved 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 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 CZMA 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 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 CD for prelease activities. In the event that there 

is a serious disagreement between BOEM and a 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 J of the 2017-2022

GOM Multisale EIS. 

5.2 ENDANGERED SPECIES ACT

The Endangered Species Act of 1973 (16 U.S.C. §§ 1531 et seq.) 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, 

which was reinitiated in 2010, 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.
Consultation and Coordination 5-5 

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. 

Refer to Appendix K of the 2017-2011 GOM Multisale EIS for copies of the consultation letters.

5.3 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 oil- and gas-related activities authorized by BOEM may result in 

adverse effects to EFH and therefore require EFH consultation.

BOEM prepared an EFH Assessment white paper that describes the OCS proposed

activities, analyzes the effects of the proposed activities on EFH, and identifies proposed mitigating 

measures (USDOI, BOEM, 2016d). The EFH Assessment was sent to NMFS on June 8, 2016, with 

a letter requesting formal consultation. This regional programmatic EFH consultation will cover 

proposed GOM lease sales analyzed in the 2017-2022 Five-Year Program and related activities (i.e., 

decommissioning and geological and geophysical). The EFH Assessment, the formalized 

conservation recommendations put forth by NMFS and accepted by BOEM/BSEE or NMFS’ 

concurrence will complete the EFH consultation. However, all agencies will continue to 

communicate for the duration of the EFH consultation (2017-2022).

5.4 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 effects of their undertakings on historic properties. 

The implementing regulations for Section 106 of the National Historic Preservation Act, issued by the 

Advisory Council on Historic Preservation (36 CFR part 800), specify the required review process. 

In accordance with 36 CFR § 800.8(c), BOEM intends to use the NEPA substitution process and 

documentation for preparing a prelease EIS and Record of Decision or a postlease environmental 

assessment and Finding of No Significant Impact to comply with Section 106 of the National Historic 

Preservation Act in lieu of 36 CFR §§ 800.3-800.6. Because of the extensive geographic area 

analyzed in this Supplemental EIS and because identification of historic properties will take place 

after leases are issued, BOEM will complete its Section 106 review process once BOEM has 

performed the necessary site-specific analysis of postlease activities prior to issuing a permit or 

approving these 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 4.13 for more information on this 
5-6 2018 Gulf of Mexico Supplemental EIS

review process and Appendix K of the 2017-2022 GOM Multisale EIS for copies of the State Historic 

Preservation Offices’ concurrence letters.

As an early planning effort, BOEM initiated a request for comment on the NOI for the 

2017-2022 GOM Multisale EIS via a formal letter to each of the affected Gulf Coast States on 

April 3, 2015. A 30-day comment period was provided. The State Historic Preservation Officers for 

Alabama, Florida, and Louisiana responded via formal letters, all concurring that no historic 

properties will be affected. The Florida State Historic Preservation Officer further requested to be 

notified and given the opportunity to comment should any cultural resources be identified off the 

Florida coast. No additional responses were received.

BOEM also solicited Tribal comment on the 2017-2022 Outer Continental Shelf Oil and Gas 

Leasing: Draft Proposed Program via a formal letter on March 4, 2015, and on the Gulf of Mexico 

OCS Oil and Gas Lease Sales: 2017-2022; Gulf of Mexico Lease Sales 249, 250, 251, 252, 253, 

254, 256, 257, 259, and 261—Draft Environmental Impact Statement via a formal letter on May 19, 

2016. Those letters were addressed to each of the Gulf Coast State-affiliated 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. The May 2016 letter was also sent to the Muscogee 

(Creek) Nation. No comments or requests to consult have yet been received; however, BOEM 

continues to invite Tribal consultation on all of its activities and will be responsive to any Tribal 

concerns that may arise.

Historic Preservation Fund

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 OCSLA (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’s monies 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). 
Consultation and Coordination 5-7 

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 State 

Historic Preservation Officers. Since the Historic Preservation Fund was implemented in 1977, the 

Historic Tax Credit program nationwide has rehabilitated nearly 39,000 buildings, created 2.4 million 

jobs, created 140,000 low- and moderate-income housing units, and 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 Historical 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).

5.5 GOVERNMENT-TO-GOVERNMENT TRIBAL CONSULTATION

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. On March 4, 2015, BOEM sent a 

formal letter to federally recognized Indian Tribes notifying them of the development of the 

2017-2022 Outer Continental Shelf Oil and Gas Leasing Draft Proposed Program and the Gulf of 

Mexico Proposed Geological and Geophysical Activities: Western, Central, and Eastern Planning 

Areas—Programmatic Environmental Impact Statement. That letter was addressed to each of the 

Gulf Coast State-affiliated 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. The letter was intended to be the 

first step of a long-term and broad consultation effort between BOEM and the Gulf-area Tribes, 

inclusive of all BOEM activities that may occur under the Draft Proposed Program, as well as 

ongoing activities. On May 19, 2016, another formal letter was sent announcing and soliciting 

consultation on the release of the 2017-2022 Proposed Program, Draft Five-Year Program EIS, and 

Draft 2017-2022 GOM Multisale EIS. That letter was sent to each of the above-listed Tribes, as well 

as to the Muscogee (Creek) Nation. As of this writing, no formal responses have been received in 

response to either the March 2015 or May 2016 letters; however, informal discussions with 

designated Tribal representatives are ongoing to determine if any of the individual Tribes desire 

continued consultation on these issues.

The Poarch Band of Creek Indians has indicated that they do not have any specific concerns 

with BOEM’s activities on the OCS, but they would like to continue to receive notifications on 

BOEM’s activities (McCullers, official communication, 2015). Additionally, the Jena Band of 
5-8 2018 Gulf of Mexico Supplemental EIS

Choctaw has indicated a general concern over adverse effects to documented or undocumented 

prehistoric and historic sites in the CPA and requests to be notified should such effects occur, as 

well as to continue being notified on BOEM’s activities (Shively, official communication, 2015a and 

2015b).

BOEM has also analyzed environmental justice issues for minority and low-income 

populations, which is broadly applicable to federally recognized Indian Tribes. Further information 

on that analysis can be found in Chapter 4.14.3.1. 

5.6 NATIONAL ENVIRONMENTAL POLICY ACT

5.6.1 Development of the Proposed Action

This Supplemental EIS addresses a proposed regionwide Federal OCS oil and gas lease 

sale, as tentatively scheduled in the Five-Year Program. This Supplemental EIS is expected to be 

used to inform decisions for each of the two proposed lease sales scheduled in 2018 and to be used 

and supplemented as necessary for decisions for each of the remaining proposed regionwide lease 

sales scheduled in the Five-Year Program. 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 sales and this Supplemental EIS. Key agencies and organizations 

included FWS, NOAA, NOAA’s National Marine Fisheries Service, National Park Service, U.S. Coast 

Guard, U.S. Department of Defense, USEPA, State governors’ offices, federally recognized Indian 

Tribes, industry, and nongovernmental organizations. 

5.6.1.1 Call for Information and Area ID Memorandum

Pursuant to the Outer Continental Shelf Lands Act of 1953, as amended (OCSLA), BOEM 

published a Call for Information (Call) to request and gather information to determine the Area 

Identification (Area ID) for each proposed lease sale. The Call was published in the Federal 

Register (2015) on September 4, 2015. The comment period for the Call closed on October 5, 2015. 

BOEM received one comment letter in response to the Call from the Louisiana Department of 

Natural Resources, which is summarized below: 

• the Louisiana Office of Coastal Management requests that BOEM consider 

secondary and cumulative impacts of OCS lease sales on coastal environments; 

• BOEM should identify, quantify, and mitigate (e.g., compensatory mitigation) 

secondary and cumulative harm that occurs to Louisiana’s coastal wetlands; 

• BOEM should implement plans for validating predictions of social and 

environmental effects on coastal resources; and 

• offshore exploration and development of hydrocarbon resources has been and 

continues to be of significant value to Louisiana and coastal communities.
Consultation and Coordination 5-9 

Using information provided in response to the Call and from scoping comments received for 

the 2017-2022 GOM Multisale EIS, BOEM developed an Area ID recommendation memorandum. 

The Area ID is an administrative prelease step that describes the geographic area for environmental 

analysis and consideration for leasing. All of this information was used to develop a proposed action 

and a reasonable range of alternatives for the 2017-2022 GOM Multisale EIS, and subsequently, this 

Supplemental EIS. On November 20, 2015, the Area ID decision was made. One Area ID was 

prepared for all proposed lease sales. The Area ID memo recommended keeping the entire 

regionwide area of the GOM included in the Proposed Final Program for consideration in the 

2017-2022 GOM Multisale EIS. The area identified for lease includes all of the available unleased 

blocks in the GOM not subject to Congressional moratorium pursuant to the Gulf of Mexico Energy 

Security Act of 2006.

5.6.1.2 Notice of Intent to Prepare a Supplemental EIS

On August 19, 2016, the NOI to prepare a Supplemental EIS for the proposed regionwide 

lease sales was published in the Federal Register (2016c). Additional public notices, including 

individual consultation invitations to federally recognized Indian Tribes, were distributed via the U.S. 

Postal Service, local newspapers, and the Internet. A 30-day comment period was provided; it 

closed on September 19, 2016. Federal, State, and local governments, federally recognized Indian 

Tribes, nongovernmental organizations, other interested parties, and the public at large were invited 

to send written comments on the scope of this Supplement EIS. BOEM received 433 comments in 

response to the NOI. These comments are summarized in Chapter 5.6.2.2. 

5.6.2 Development of the Draft Supplemental EIS

5.6.2.1 Scoping

Scoping for the Draft Supplemental EIS was conducted in accordance with CEQ regulations 

for implementing NEPA. Public scoping provides those with an interest in the OCS Program an 

opportunity to provide comments on the proposed action. Public scoping meetings were held in 

Mississippi, Alabama, Texas, and Louisiana on the following dates and at the times and locations 

indicated below:

Tuesday, September 6, 2016

4:00 p.m. until 7:00 p.m. CDT

Courtyard by Marriott

Gulfport Beachfront MS Hotel

1600 East Beach Boulevard

Gulfport, Mississippi 39501

1 registered attendee

0 verbal comments received

1 written comment received

Wednesday September 7, 2016

4:00 p.m. until 7:00 p.m. CDT

Renaissance Mobile Riverview 

Plaza Hotel

64 South Water Street

Mobile, Alabama 36602

6 registered attendees 

2 verbal comments received

1 written comment received
5-10 2018 Gulf of Mexico Supplemental EIS

Tuesday, September 13, 2016

4:00 p.m. until 7:00 p.m. CDT

Houston Marriott North

255 North Sam Houston Pkwy East

Houston, Texas 77060

4 registered attendees 

2 verbal comments received

0 written comments received

Thursday, September 15, 2016

4:00 p.m. until 7 p.m. CDT

Wyndham Garden New Orleans Airport

6401 Veterans Memorial Blvd.

Metairie, Louisiana 70003

14 registered attendees

0 verbal comments received

2 written comments received

5.6.2.2 Summary of Scoping Comments

In addition to accepting oral and written comments at each public meeting, BOEM accepted 

written comments by mail and through the regulations.gov web portal (http://www.regulations.gov). 

BOEM received 433 comments in response to the NOI and 8 comments from the scoping meetings, 

totaling 441 comments. Of the comments received, 1 was a mailed letter; 3 were emails; 73 were 

received through the regulations.gov web portal; and 356 were form letters received in a bulk 

package. Comments came from Federal and State agencies, interest groups, industry, 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. Each comment was read and 

categorized according to its source and the nature of the information included. All scoping 

comments received that were relevant for a lease sale NEPA document were considered in the 

preparation of the Draft Supplemental EIS. The scope and content of this Supplemental EIS was

formulated to ensure that the relevant issues and concerns expressed by stakeholders during the 

scoping process were fully addressed. Summaries of comments received follow.

Louisiana Department of Natural Resources, Office of Coastal Management

• The Louisiana Office of Coastal Management continues to support the expansion 

of exploration and development of energy resources throughout the OCS waters 

and views these efforts as crucial to our Nation’s economic and energy security.

• The State of Louisiana expressed that indirect and cumulative impacts to 

Louisiana’s coastal resources are not adequately addressed in previous EISs.

• The State of Louisiana is also concerned that Louisiana’s coastal wetlands are 

disproportionately bearing the impacts from OCS oil- and gas-related activities 

and requests compensatory mitigation.

• The Louisiana Office of Coastal Management acknowledges the progress that 

BOEM has continued to make in improving the procedures and techniques used 

in the environmental review process. However, BOEM must better revisit the 

predictions made for previous lease sales and compare these predictions with 

existing environmental conditions and adjust its impact evaluation process 

accordingly. 
Consultation and Coordination 5-11

Consumer Energy Alliance

• In recent years, the domestic energy revolution has provided a major boost to the 

American economy and consumer pocketbooks, while fundamentally 

transforming the global geopolitical landscape to the benefit of U.S. national 

security. At the same time, thanks to continuing improvements in technology, 

practices, and oversight, the United States has demonstrated that offshore 

energy development and environmental stewardship can and do exist. 

• The Consumer Energy Alliance understands that, to meet our long-term energy 

needs, we will need to access all of our resources, including oil and natural gas, 

nuclear, solar, wind, and beyond. We also understand that oil and natural gas 

will continue to be a critical and dominant part of that mix for decades to come.

• Industry and regulators alike have taken a number of actions in recent years that 

have further strengthened the safety of offshore operations in U.S. waters.

• An “all of the above” approach to energy policy is the only sensible solution, and 

that must include the Gulf of Mexico.

• The Consumer Energy Alliance urges the Department of the Interior to include 

valuable offshore opportunities in the Gulf of Mexico and to reject any demands 

to take actions that would in any way delay, restrict, or prohibit proposed Lease 

Sales 250 and 251.

Louisiana Mid-Continent Oil and Gas Association

• The Louisiana Mid-Continent Oil and Gas Association fully supports a continued 

robust OCS leasing program in the Gulf of Mexico.

• Louisiana’s offshore oil and gas industry has a $44 billion economic impact on 

the State of Louisiana. Combining the offshore sector with related pipeline and 

refining activities, the oil and gas industry has $70 billion total annual impact to 

Louisiana. Federal revenue from offshore energy production in the past 10 years 

totaled $80 billion in lease sales and royalties – a major source of revenue for our 

country.

• Louisiana has demonstrated how to balance the development of our Nation’s oil 

and gas resources off its coast and still maintain a robust hunting, fishing, and 

wildlife industry. In Louisiana, commercial fishing provides one-fourth of the 

fisheries catch in the lower 48 states, and our wetlands provide habitat for about 

1.8 million migratory waterfowl. Wildlife recreation has amounted to a $2.2 billion 

industry.

• Since 2010, the oil and gas industry has demonstrated its commitment to ensure 

that people and the environment are protected during all phases of energy 

exploration, development, and production. A robust collaborative effort among 
5-12 2018 Gulf of Mexico Supplemental EIS

industry has resulted in the development of new technology and standards for 

prevention, intervention, and response. Industry has formed the Marine Well 

Containment Company and has developed cutting-edge technology to minimize 

the risk of a catastrophic oil spill. They have also formed the Center for Offshore 

Safety to continuously improve the safety performance of offshore operations.

• As a result of Gulf of Mexico Energy Security Act of 2006, Louisiana, Texas, 

Mississippi, and Alabama will receive 37.5 percent of royalties received from new 

oil and gas developments in Federal waters, and in 2017 that will expand to 

include a portion of all lease sale receipts since December 2006. Beginning in 

2017, Louisiana will receive nearly $200 million per year through OCS revenue 

sharing that is dedicated to the Louisiana coast and projects designed to protect 

it.

Senator Sharon Hewitt, 2016 Regular Session, Louisiana Senate Resolution No. 116

• The Louisiana oil and gas industry and its workers, suppliers, and the entire 

business community have expressed their strong support for offshore energy 

exploration. 

• The American economy is truly dependent on and stimulated by the oil and gas 

production of the Gulf of Mexico. 

• The Gulf of Mexico provides nearly 20 percent of the Nation’s crude oil supply.

• In Fiscal Year 2014 alone, the Gulf of Mexico energy development supported 

over 650,000 jobs, contributed over $64 billion in gross domestic product, and 

provided over $7 billion in revenue to the Federal Government. 

• Offshore energy development and production in the Gulf of Mexico is vital to the 

economic well-being of the Gulf Coast States, coastal communities, and the 

entire Nation. 

• Louisiana has been consistently ranked number two in the Nation in natural gas 

production, ranked in the top five in oil production, and our refining capability is 

second only to Texas. 

• Our Nation’s energy policy is dependent on a thriving oil and natural gas industry 

in the Gulf of Mexico and requires continued and expanded access to all areas of 

the Gulf of Mexico to increase and improve the economic well-being of residents, 

workers, and businesses in the Gulf Coast States’ regions. 

• Our Nation’s energy policy directly affects our trade policy with other countries, 

our workforce, our economy, and our position as a global super-power to protect 

our interests at home.
Consultation and Coordination 5-13

American Petroleum Institute

• The American Petroleum Institute recommends that the Supplemental EIS focus 

on new information that is readily available and limit the Supplemental EIS to an 

analysis of this new information and not speculate on future results from ongoing 

studies. 

• BOEM should consider the extensive safety improvements implemented by 

industry and the new requirements imposed on offshore operations since the 

Deepwater Horizon explosion, oil spill, and response, particularly the formation of 

many well containment companies and their ability to assist in any potential 

future incidents.

• This Supplemental EIS should be designed to serve as a document for future 

environmental reviews.

• Data from the best available peer-reviewed scientific literature, and not 

speculation, should be used.

Center for Biological Diversity; 350 Louisiana; Bold Louisiana; Earth Action, Inc.; Friends of 

the Earth; Greenpeace, USA; Gulf Restoration Network; and Louisiana Bucket Brigade

• BOEM’s proposal will deepen the climate crisis and reverse course on President 

Obama’s commitment to combat climate change. The proposal also threatens 

frontline communities and GOM wildlife with more toxic air and water pollution, 

coastal erosion, extreme weather events, and oil spills. We urge BOEM to halt 

all new oil and gas leases.

• BOEM’s proposal fails to comply with the clear requirements of the OCSLA and 

NEPA to precisely define areas available for leasing and to conduct an analysis 

on a finer geographic scale. BOEM must remedy the numerous faults with its 

Draft Multisale EIS from which this document will tier to; consider new 

information regarding climate impact of offshore oil and gas; and harmful impacts 

of offshore fracking in the Gulf. It is entirely improper for BOEM to be moving 

forward with these 2018 lease sales before the 2017-2022 OCS Oil and Gas 

Leasing Program (“Program”) is finalized. BOEM’s proposal implements an 

inappropriate change to its NEPA procedures that will lead to less environmental 

analysis. BOEM is abandoning its prior approach of conducting a supplemental 

NEPA analysis for each lease sale held in the Gulf of Mexico. Such an approach 

also violates BOEM’s duties under OCSLA to comply with NEPA at every stage 

of the offshore oil and gas authorization process; and ensure offshore 

development is balanced with environmental safeguards and protection of the 

human, marine, and coastal environments. BOEM would offer the entire Gulf of 

Mexico OCS planning area not under moratorium to oil companies. But Section 

18(a) expressly requires BOEM to prepare a leasing program that consists “of a 

schedule of proposed lease sales indicating, as precisely as possible, the size, 
5-14 2018 Gulf of Mexico Supplemental EIS

timing, and location of leasing activity.” Instead of “precisely” defining the 

location of lease sales, BOEM’s proposal takes an areawide approach that 

designates the entire Gulf of Mexico as the area eligible for lease sales. This 

areawide lease sale approach is incompatible with the OCSLA. Indeed, under 

this approach, BOEM is allowing the oil industry to determine which areas are 

explored and developed, thereby abdicating the agency’s responsibility under the 

OCSLA to direct oil activities and assure that they do not cause environmental 

harm. The designation lacks the precision required by law and is therefore 

unlawful.

• BOEM’s Supplemental Analysis Must Remedy Numerous Deficiencies and 

Address New Information. In addition, NEPA regulations recognize that “tiering” 

from one environmental analysis to another may sometimes be appropriate 

where a broad environmental analysis has been conducted and the agency 

wishes to refer back to that assessment at a subsequent stage to avoid 

repetition. BOEM cannot continue to use tiering to avoid the requisite in-depth 

analysis required by NEPA.

• Finally, the Supplemental EIS must address new information revealed since the 

close of the public comment period on the Draft Multisale EIS. This new 

information includes unprecedented flooding in Louisiana; a report indicating the 

potential greenhouse gas emissions from offshore oil and gas drilling in the 

GOM; guidance from the Council on Environmental Quality (“CEQ”) on analyzing 

the lifecycle greenhouse gas emissions from proposed projects; and the scope of 

offshore fracking being permitted in the Gulf of Mexico.

• BOEM’s analysis must consider the final CEQ Guidance on Consideration of 

Greenhouse Gas Emissions and the Effects of Climate Change in NEPA issued 

on August 5, 2016. BOEM’s Supplemental EIS must properly account for the 

downstream and lifecycle greenhouse gas emissions as the result of proposed 

Lease Sales 250 and 251.

• BOEM must also consider new information revealing the scope of inherently 

dangerous offshore fracking permitted in the Gulf of Mexico. New information 

reveals that the Obama administration permitted oil companies to frack offshore 

wells in the Gulf and Mexico more than 1,200 times between 2010 and 2014 

alone. The fracks occurred in at least 630 different wells off the coasts of Texas, 

Louisiana, Mississippi, and Alabama; and many took place in critical habitat for 

imperiled loggerhead sea turtles. New information also reveals that at least one 

of the wells, which was connected to the flow line involved in a nearly 

90,000-gallon oil spill in the Gulf of Mexico discovered on May 12, 2016, was 

fracked.

• Offshore fracking has several significant harmful impacts beyond that of 

conventional offshore oil and gas development. For example, oil companies are 
Consultation and Coordination 5-15

allowed to dump their wastewater — including fracking chemicals — into the Gulf 

of Mexico, which may harm the Gulf of Mexico’s sensitive wildlife. Many fracking 

chemicals are known to be toxic to people and marine animals. Forty percent of 

the chemicals added to fracking fluids have ecological effects, meaning they can 

harm aquatic and other wildlife. An analysis of the chemicals used during 

offshore fracking events in California found that many of the chemicals could kill 

or harm a broad variety of marine organisms, including sea otters, fish, and 

invertebrates. Indeed, scientists list some of the chemicals frequently used in 

offshore fracking as among the most toxic in the world with respect to aquatic life. 

Numerous scientists and reports have also linked fracking to water 

contamination, air contamination, spills, earthquakes and birth defects. BOEM’s 

Supplemental EIS must properly account for the added harms and risks caused 

by offshore fracking in the Gulf of Mexico. 

Terrebonne Port Commission

• Ending energy exploration in the Gulf of Mexico would start the elimination of 

billions of dollars in royalties to the Federal and State governments, and 

eliminate thousands of direct oil field jobs and several thousand spin off jobs. 

The State of Louisiana’s economy would eventually be cut in half. It would force 

the U.S. to depend on importing more oil and gas, where this county needs 

energy independence.

Grow the Gulf

• Grow the Gulf supports the proposed action and continued safe energy 

exploration in the Gulf of Mexico.

Jean Public

• Jean Public opposes the proposed action due to the lack of safety changes since 

the Deepwater Horizon explosion, oil spill, and response.

Public Comments Supporting the Proposed Action

Almost 380 individual comments were received that were in support of the proposed lease 

sales, 356 of which were form letters. Commenters stated that future leases are vital to the national 

economy and security, and integral to the State of Louisiana and local economies and jobs. Several 

noted that oil and gas companies and employees must be good stewards of the environment and 

continue to provide more emphasis on safety. Several commenters stated that the recent downturn 

in oil and gas prices is hurting small towns and southern states in general.
5-16 2018 Gulf of Mexico Supplemental EIS

Public Comments Supporting Alternative E, the No Action Alternative

Twenty-three individual comments were received that opposed future lease sales. 

Commenters stated that renewable energy should be pursued instead of oil and gas, fossil fuels 

should be left in the ground, and new lease sales are not compatible with the Paris Treaty. Issues of 

concern included the impacts of oil and gas on greenhouse gas emission and global climate change, 

the impacts of climate change on the GOM’s environmental resources, warmer oceans, increased 

storms and flooding events, and land loss. Several were also concerned about continuing oil and 

chemical spill risks, continuing effects of past oil and chemical spills, leaking wells and pipelines, and 

a lack of reasonable alternatives. Environmental resources of concern included protected species 

(i.e., marine mammals, sea turtles, beach mice, protected birds, and corals), wetlands, fish 

nurseries, coral reefs, safety of seafood, and environmental justice. There were also comments on 

environmental justice concerns related to those living nearby petrochemical processing facilities.

5.6.2.3 Additional Public Input Opportunities

Although the scoping process is formally initiated by the publication of the NOI, scoping 

efforts and other coordination meetings have proceeded and will continue to proceed throughout the 

NEPA processes for the Five-Year Program. 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:

• request for information and comments on the 2017-2022 Five-Year Program,

• scoping and comments on the 2017-2022 Five-Year Program EIS, and

• scoping and comments on the 2017-2022 GOM Multisale EIS.

5.6.2.4 Cooperating Agencies

According to Part 516 of the DOI Departmental Manual, BOEM must invite eligible 

government 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 must either accept or deny such requests.

The NOI, which was published on August 19, 2016, 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 a letter dated October 28, 2016, NPS requested 

cooperating agency status for this Supplemental EIS. On December 29, 2016, a Memorandum of 

Agreement between BOEM and NPS was initiated, which defines the roles and responsibilities for 

each agency (Appendix A). 
Consultation and Coordination 5-17

5.6.2.5 Distribution of the Draft Supplemental EIS for Review and Comment

BOEM will send copies of the Draft Supplemental EIS to the government, public, and private 

agencies and groups listed below. Local libraries along the Gulf Coast will be provided copies of this 

document; a list of these libraries is available on BOEM’s website at http://www.boem.gov/

nepaprocess/. 

Federal Agencies

Congress

Congressional Budget Office

House Resources Subcommittee on 

Energy and Mineral Resources

Senate Committee on Energy and Natural 

Resources

Department of Commerce

National Oceanic and Atmospheric 

Administration

National Marine Fisheries Service

Department of Defense

Department of the Air Force

Department of the Army

Corps of Engineers

Department of the Navy

Naval Mine and Anti-Submarine 

Warfare Command

Department of Energy

Strategic Petroleum Reserve PMD

Department of Homeland Security

U.S. 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

Pipeline and Hazardous Materials Safety 

Administration

Office of Pipeline Safety

Environmental Protection Agency

Region 4

Region 6

Marine Mammal Commission

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

Franklin County

Gulf County

Hernando County
5-18 2018 Gulf of Mexico Supplemental EIS

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 Grand Isle

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

Houma-Terrebonne Chamber of 

Commerce

Jefferson Parish Director

Jefferson Parish President

Lafourche Parish Coastal Zone 

Management

Lafourche Parish Water District #1

Louisiana Geological Survey

South Lafourche Levee District

St. Bernard Planning Commission

State House of Representatives, Natural 

Resources Committee

State Legislature, Natural Resources 

Committee

State of Louisiana Library

Terrebonne Parish

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

Texas

Governor’s Office

Aransas Pass Public Library

Attorney General of Texas

Chambers County Library System

City of Lake Jackson

General Land Office

Southeast Texas Regional Planning 

Commission

State Legislature Natural Resources 

Committee

State Senate Natural Resources 

Committee

Texas Historical Commission

Texas Legislation Council

Texas Parks and Wildlife Department

Texas Sea Grant

Texas State Library and Archives

Texas Water Development Board

Federally Recognized Indian Tribes

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

Tunica-Biloxi Indian Tribe of Louisiana
Consultation and Coordination 5-19

Industry

Adams and Reese, LLP

Alabama Petroleum Council

American Petroleum Institute

Applied Technology Research Corporation

Area Energy LLC

Associated Gas Distributors of Florida 

Baker Atlas

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 Conservation Association

Coastal Environments, Inc.

Columbia Gulf Transmission

Continental Shelf Associates, Inc.

De Leon & Associates

Ecological Associates, Inc.

Ecology and Environment

Ecosystem Management, Inc.

Energy Partners, Ltd.

EOG Resources, Inc.

Exxon Mobil Production Company

Florida Natural Gas Association

Florida Petroleum Council

Florida Power and Light

Florida Propane Gas Association

Freeport-McMoRan, Inc.

General Insulation, Inc.

Global Industries, Ltd.

Gulf of Mexico Newsletter

Halliburton Corporation

Han & Associates, Inc.

Horizon Marine, Inc.

Industrial Vehicles International, Inc.

J. Connor Consultants

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.

Marine Safety Office

Mid-Continent Oil and Gas Association

Nature’s Way Marine, LLC

Newfield Exploration Company

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

Seneca Resources Corporation

SEOT, Inc.

Shell Exploration & Production Company

Shell Offshore, Inc.

Stone Energy Corporation

Strategic Management Services-USA

T. Baker Smith, Inc.

Texas Geophysical Company, Inc.

The SJI, LLC

The Times-Picayune

The Washington Post

URS Corporation

W & T Offshore, Inc.

Waring & Associates

WEAR-TV

Special Interest Groups

1000 Friends of Florida

Alabama Oil & Gas Board

Alabama Nature Conservancy

Alabama Wildlife Federation

American Cetacean Society

Apalachee Regional Planning Council

Apalachicola Riverkeeper

Audubon Louisiana Nature Center

Audubon of Florida

Barataria-Terrebonne National Estuary 

Program

Bay County Chamber of Commerce

Bay Defense Alliance 

Capital Region Planning Commission

Center for Marine Conservation

Citizens Association of Bonita Beach

Clean Gulf Associates

Coalition to Restore Coastal Louisiana

Coastal Conservation Association

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
5-20 2018 Gulf of Mexico Supplemental EIS

Gulf Coast Fisherman’s Coalition

Gulf Restoration Network

Houma-Terrebonne Chamber of 

Commerce

LA 1 Coalition, Inc.

League of Women Voters of the 

Pensacola Bay Area

Louisiana Wildlife Federation

Manasota-88

Marine Mammal Commission

Mobile Bay National Estuary Program

Natural Resources Defense Council

Nature Conservancy

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

Save the Manatee Club

Sierra Club

South Central Industrial Association

Surfrider Foundation

The Nature Conservancy

The Ocean 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

Grand Isle Port Commission

Greater Baton Rouge Port Commission

Greater Lafourche Port Commission

Lake Charles Harbor and Terminal District

Plaquemines Port, Harbor and Terminal 

District 

Port of Baton Rouge

Port of Iberia District

Port of New Orleans

Twin Parish Port Commission

St. Bernard Port, Harbor and Terminal 

District 

West Cameron Port Commission

Mississippi

Mississippi State Port Authority

Texas

Brownsville Navigation District—Port of 

Brownsville

Port Freeport

Port Mansfield/Willacy County Navigation 

District 

Port of Beaumont

Port of Corpus Christi Authority

Port of Galveston

Port of Houston Authority

Port of Isabel—San Benito Navigation 

District 

Port of Port Arthur Navigation District

Educational Institutions/Research 

Laboratories

Abilene Christian University

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
Consultation and Coordination 5-21

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 Texas at Arlington

University of Texas at Austin

University of Texas Law School

University of Texas Libraries

University of West Florida

CHAPTER 6 

 

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7:23-42.
CHAPTER 7 

 

PREPARERS

Preparers 7-3 

7 PREPARERS

Gary D. Goeke, Chief, Environmental Assessment Section (retired)

Tershara N. Matthews, Acting Chief, Environmental Assessment Section

Lissa Lyncker, Unit Supervisor, Environmental Protection Specialist

Michelle Nannen, NEPA Coordinator, Environmental Scientist

Ariel Kay, NEPA Co-Coordinator, Environmental Scientist

Kimberly Bittler, Headquarters’ Coordinator, Oceanographer

Robert Martinson, Headquarters’ Coordinator, Biologist

Bruce Baird, Biologist

Mark Belter, Marine Biologist

Idrissa Boube, Environmental Scientist

Darice K. Breeding, Environmental Protection Specialist (retired)

Brian Cameron, Senior Environmental Scientist

Alicia Caporaso, Marine Archaeologist

Sindey Chaky, Social Scientist

Nikki Charpentier, Protected Species Biologist

Leonard Coates, Supervisor, Mapping and Automation Section

Thierry DeCort, Chief, Geological and Geophysical Section

Ross Del Rio, Environmental Scientist

Chris DuFore, Oceanographer

Stephanie Gambino, Chief, Biological/Social Sciences Section

Donald (Tre) W. Glenn III, Protected Species Biologist

Stephen Gonzales, Geographer, Mapping and Automation Section

Mike Gravois, Geographer, Mapping and Automation Section

Jose Hernandez, Physical Scientist

Jack Irion, Unit Supervisor, Marine Archaeologist

Mark Jensen, Economist

Douglas Jones, Senior Marine Archaeologist

Agatha-Marie (Arie) Kaller, Unit Supervisor, Marine Biologist

Pedro Levy, Geographer, Mapping and Automation Section

Paula (Kaye) London, Protected Species Biologist

Charles (Jay) McCreery, Physical Scientist

Stacie Merritt, Physical Scientist

Margaret Metcalf, Chief, Physical/Chemical Sciences Section

Deborah Miller, Technical Editor

David P. Moran, Biologist 

Mark Mueller, Marine Ecologist

Trevis Olivier, Environmental Scientist

S. Erin O’Reilly, Physical Scientist

Stephen Pomes, Librarian

Michael Prymula, Geographer, Mapping and Automation Section

Catherine Rosa, Environmental Assessment Program Specialist

Helen Rucker, Environmental Scientist

Shane Stradley, Geographer, Mapping and Automation Section

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, as opposed to chronic. Effects 

associated with acute can vary depending 

on the context of its use (e.g., acute 

[short-term] exposure could be more or less 

problematic than chronic [long-term] 

exposure).

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.

Antipatharian Transitional Zone—The area 

located between 50 and 90 m (164 and 

295 ft), where available light is reduced and 

there is a gradual ecosystem change from 

tropical shallow-water corals that are 

dependent on light to deeper water species, 

such as antipatharian black corals that are 

not.

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 

5,760 ac (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, BOPs are located on 

the seafloor.

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.
8-4 2018 Gulf of Mexico Supplemental EIS

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 50°-120°.

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 0.1°). 

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 3°-6°).

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 
Glossary 8-5 

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 USEPA on 

quantities, rates, and concentrations of 

chemical, physical, 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.
8-6 2018 Gulf of Mexico Supplemental EIS

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.

Hermatypic—Corals in the order Scleractinia 

that build reefs by depositing hard 

calcareous material for their skeletons, 

forming the stony framework of the reef. 

Corals that do not contribute to coral reef 

development are referred to as ahermatypic 

(non-reef-building) species.

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 
Glossary 8-7 

otherwise lawful activity (e.g., fishing) 

conducted by a Federal agency or applicant 

(refer to Taking).

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 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. 

Littoral zone—Marine ecological realm that 

experiences the effects of tidal and 

longshore currents and breaking waves to a 

depth of 5-10 m (16-33 ft) below the low-tide 

level, depending on the intensity of storm 

waves.

Longshore sediment transport—The 

cumulative movement of beach sediment 

along the shore (and nearshore) by waves 

arriving at an angle to the coastline and by 

currents generated by such waves.

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 
8-8 2018 Gulf of Mexico Supplemental EIS

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.

Oceanic zone—Offshore water >200 m (656 ft) 

deep. It is the region of open sea beyond 

the edge of the continental shelf and 

includes 65 percent of the ocean's

completely open water.

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 adjacent to the United 

States and seaward of State offshore lands.

Passerines—Perching birds (members of the 

Order Passeriformes) and songbirds.

Potential Biological Removal (PBR)—Of or 

pertaining to the open sea; associated with 

open water beyond the direct influence of 

coastal systems.

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 
Glossary 8-9 

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.
8-10 2018 Gulf of Mexico Supplemental EIS

Shear ram—The component in a BOP that 

cuts, or shears, through the drill pipe and 

forms a 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.

Site fidelity or philopatry—The tendency to 

return to a previously occupied location.

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 spill-response activity.

State coastal zone boundary—The State 

coastal zone boundaries for each 

CZMA-affected State are defined at 

https://coast.noaa.gov/czm/media/StateCZB

oundaries.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.

Tidal prism—The volume of water in an estuary 

or inlet between mean high tide and mean 

low tide, or the volume of water leaving an 

estuary at ebb tide.

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.
APPENDIX A 

 

COOPERATING AGENCY 

MEMORANDUM OF AGREEMENT

Cooperating Agency Memorandum of Agreement A-3

A COOPERATING AGENCY MEMORANDUM OF AGREEMENT
A-4 2018 Gulf of Mexico Supplemental EIS
Cooperating Agency Memorandum of Agreement A-5
A-6 2018 Gulf of Mexico Supplemental EIS
APPENDIX B 

 

AIR QUALITY: 

WRF MODEL PERFORMANCE

Table of Contents B-iii

TABLE OF CONTENTS

Page

B.1 INTRODUCTION........................................................................................................................ B-1

B.2 WRF MODELING METHODOLOGY......................................................................................... B-5

B.2.1 Gulf of Mexico Region Air Quality Meteorological Modeling........................................... B-5

B.2.2 Model Domain Configuration........................................................................................... B-6

B.2.3 Model Application............................................................................................................ B-7

B.2.3.1 Model Vertical Resolution................................................................................ B-7

B.2.3.2 Topographic Inputs.......................................................................................... B-8

B.2.3.3 Vegetation Type and Land Use Inputs............................................................ B-9

B.2.3.4 Atmospheric Data Inputs ................................................................................. B-9

B.2.3.5 Time Integration............................................................................................... B-9

B.2.3.6 Diffusion Options ............................................................................................. B-9

B.2.3.7 Lateral Boundary Conditions ........................................................................... B-9

B.2.3.8 Top and Bottom Boundary Conditions .......................................................... B-10

B.2.3.9 Sea-Surface Temperature Inputs .................................................................. B-10

B.2.3.10 FDDA Data Assimilation................................................................................ B-10

B.2.3.11 WRF Physics Options.................................................................................... B-11

B.2.3.12 WRF Application Methodology ...................................................................... B-11

B.3 WRF MODEL PERFORMANCE EVALUATION RESULTS.................................................... B-12

B.3.1 Quantitative Evaluation Using Metstat.......................................................................... B-12

B.3.1.1 Quantitative Statistics .................................................................................... B-13

B.3.1.2 METSTAT Evaluation Using Integrated Surface Hourly Observations and 

Offshore Buoy Observations ......................................................................... B-15

B.3.2 Qualitative Evaluation Using Wind Roses..................................................................... B-22

B.3.3 Qualitative Evaluation Using Upper-Air Data................................................................ B-27

B.3.4 Qualitative Evaluation Using Precipitation .................................................................... B-29

B.3.4.1 Evaluation Over Land Using PRISM Precipitation ........................................ B-29

B.3.4.2 Evaluation Over Water Using Satellite Precipitation..................................... B-43

B.3.4.3 Evaluation Using Tropical Cyclone Precipitation Events .............................. B-56

B.4 SUMMARY AND CONCLUSIONS........................................................................................... B-59

B.5 REFERENCES......................................................................................................................... B-59

List of Tables B-v 

LIST OF TABLES

Page

Table B-1. Nonattainment and Maintenance Areas in the Southeastern U.S.................................. B-3

Table B-2. BOEM Gulf of Mexico OCS Region WRF Domain Configuration................................... B-6

Table B-3. BOEM Gulf of Mexico OCS Region WRF Dataset Model Levels................................... B-8

Table B-4. BOEM Gulf of Mexico OCS Region WRF Physics Options.......................................... B-11

Table B-5. Meteorological Model Performance Benchmarks for Simple and Complex 

Conditions...................................................................................................................... B-12

LIST OF FIGURES

Page

Figure B-1. Location of the “Air Quality Modeling in the Gulf of Mexico Region” Study with 

Class I Areas and Platform Locations.......................................................................... B-1

Figure B-2. Ozone Nonattainment Areas in the Southeastern U.S................................................ B-2

Figure B-3. Overview of the “Air Quality Modeling in the Gulf of Mexico Region” Study 

Tasks............................................................................................................................ B-4

Figure B-4. WRF 36-km CONUS (d01), 12-km SE Regional (d02), and 4-km Gulf of Mexico 

Region (d03) Domains ................................................................................................. B-7

Figure B-5. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Wind Direction 

Performance for 2012 ................................................................................................ B-16

Figure B-6. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Wind Speed 

Performance for 2012 ................................................................................................ B-16

Figure B-7. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Temperature 

Performance for 2012 ................................................................................................ B-17

Figure B-8. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Humidity 

Performance for 2012 ................................................................................................ B-17

Figure B-9. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Wind Direction 

Performance for 2012 ................................................................................................ B-18

Figure B-10. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Wind Speed 

Performance for 2012 ................................................................................................ B-18

Figure B-11. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Temperature 

Performance for 2012 ................................................................................................ B-19

Figure B-12. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Humidity 

Performance for 2012 ................................................................................................ B-19

Figure B-13. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Wind Direction 

Performance for 2012 ................................................................................................ B-20

Figure B-14. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Wind Speed 

Performance for 2012 ................................................................................................ B-20
B-vi 2018 Gulf of Mexico Supplemental EIS

Figure B-15. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Temperature 

Performance for 2012 ................................................................................................ B-21

Figure B-16. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Humidity 

Performance for 2012 ................................................................................................ B-21

Figure B-17. Wind Rose Locations for Port Isabel, TX (PTIT), Calcasieu, LA (CAPL), 

Gulfport, MS (KGPT), and Naples, FL (NPSF).......................................................... B-22

Figure B-18. 2012 WRF Wind Rose Compared to 2012 Observation Wind Rose from 

Gulfport, MS in 4-km Domain..................................................................................... B-23

Figure B-19. 2012 WRF Wind Rose Compared to 2012 Observation Wind Rose from 

Naples, FL in 4-km Domain ....................................................................................... B-24

Figure B-20. 2012 WRF Wind Rose Compared to 2012 Observation Wind Rose from 

Port Isabel, TX in 4-km Domain................................................................................. B-25

Figure B-21. 2012 WRF Wind Rose Compared to 2012 Observation Wind Rose from 

Calcasieu, LA in 4-km Domain................................................................................... B-26

Figure B-22. Vertical Profile Soundings Comparing the 4-km WRF to Upper-Air 

Observations Data for Brownsville, TX on August 3, 2012, and Key West, FL 

on January 4, 2012, at 00 UTC.................................................................................. B-28

Figure B-23. January 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain............... B-31

Figure B-24. February 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain ............. B-32

Figure B-25. March 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain.................. B-33

Figure B-26. April 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain .................... B-34

Figure B-27. May 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain..................... B-35

Figure B-28. June 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain.................... B-36

Figure B-29. July 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain ..................... B-37

Figure B-30. August 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain ................ B-38

Figure B-31. September 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain.......... B-39

Figure B-32. October 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain............... B-40

Figure B-33. November 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain........... B-41

Figure B-34. December 2012 PRISM Precipitation and WRF Precipitation, 4-km Domain........... B-42

Figure B-35. January 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain .............................................................. B-44

Figure B-36. February 2012 TRMM Precipitation Average and Corresponding WRF 

precipitation Average in the 12-km Domain............................................................... B-45

Figure B-37. March 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain .............................................................. B-46

Figure B-38. April 2012 TRMM Precipitation Average and Corresponding WRF Precipitation 

Average in the 12-km Domain ................................................................................... B-47

Figure B-39. May 2012 TRMM Precipitation Average and Corresponding WRF Precipitation 

Average in the 12-km Domain ................................................................................... B-48

Figure B-40. June 2012 TRMM Precipitation Average and Corresponding WRF Precipitation 

Average in the 12-km Domain ................................................................................... B-49

Figure B-41. July 2012 TRMM Precipitation Average and Corresponding WRF Precipitation 

Average in the 12-km Domain ................................................................................... B-50
List of Figures B-vii

Figure B-42. August 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain .............................................................. B-51

Figure B-43. September 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain .............................................................. B-52

Figure B-44. October 2012 TRMM Precipitation Average and Corresponding WRF 

Precipitation Average in the 12-km Domain .............................................................. B-53

Figure B-45. November 2012 TRMM precipitation average and Corresponding WRF 

Precipitation Average in the 12-km Domain .............................................................. B-54

Figure B-46. December 2012 TRMM precipitation average and Corresponding WRF 

Precipitation Average in the 12-km Domain .............................................................. B-55

Figure B-47. Daily Precipitation Plots from WRF, PRISM, and TRMM on August 30, 2012 ......... B-57

Figure B-48. Daily Precipitation Plots from WRF, PRISM, and TRMM Databases on June 25, 

2012............................................................................................................................ B-58

Air Quality: WRF Model Performance B-ix

ABBREVIATIONS AND ACRONYMS

ARW Advanced Research WRF

BOEM Bureau of Ocean Energy Management

CAI Climatologically Aided Interpolation

CAAA Clean Air Act Amendments

CAMx Comprehensive Air Quality Model with Extensions

CFL Courant-Friedrichs-Lewy

CFSR Climate Forecast System Reanalysis

CFSv2 Climate Forecast System Version 2

CMAQ Community Multi-scale Air Quality model

ECMWF European Center for Medium-Range Weather Forecasting

EIS Environmental Impact Statement

ERA European Center for Medium-Range Weather Forecasting Re-Analysis

ERG Eastern Research Group, Inc.

ESRL Earth System Research Laboratory

FDDA Four-Dimensional Data Assimilation

FNMOC Fleet Numerical Meteorology and Oceanography Center

IC/BC Initial Conditions/Boundary Conditions

IOA Index of Agreement

ISHO Integrated Surface Hourly Observation

KBRO Meteorological Call Sign for Brownsville

KSIL Meteorological Call Sign for Slidell

KTPA Meteorological Call Sign for Tampa

KEYW Meteorological Call Sign for Key West

LCC Lambert Conformal Conic 

LSM Land-Surface Model

MADIS Meteorological Assimilation Data Ingest System

METSTAT Meteorological Statistical Program

MM5 Mesoscale Meteorological Model version 5

MMIF Mesoscale Model Interface Program 

MPE Model Performance Evaluation

NAAQS National Ambient Air Quality Standards

NAM North American Model

NASA National Aeronautics and Space Administration

NCAR National Center for Atmospheric Research

NCDC National Climatic Data Center

NCEP National Centers for Environmental Prediction

NDBC National Data Buoy Center

NEPA National Environmental Policy Act

NMM Nonhydrostatic Mesoscale Model
B-x 2018 Gulf of Mexico Supplemental EIS

NOAA National Oceanographic Atmospheric Administration 

NWS National Weather Service

OCS Outer Continental Shelf

OCSLA OCS Lands Act 

PBL Planetary Boundary Layer

PGM Photochemical Grid Model

PRISM Parameter-elevation Regressions on Independent Slopes Model

RMSE Root Mean Square Error

RRTMG Rapid Radiative Transfer Model for GCMs

SCAS-OSU Spatial Climate Analysis Service at Oregon State University

SST Sea-Surface Temperature

TRMM Tropical Rainfall Measurement Mission

USEPA United States Environmental Protection Agency

USDOC United States Department of Commerce

USGS United States Geological Survey

UTC Universal Time Coordinate

WPS WRF Pre-processing System

WRAP Western Regional Air Partnership

WRF Weather Research and Forecasting model
Air Quality: WRF Model Performance B-1 

B AIR QUALITY: WRF MODEL PERFORMANCE

B.1 INTRODUCTION

The U.S. Department of the Interior’s Bureau of Ocean Energy Management (BOEM) is 

required under the Outer Continental Shelf Lands Act (OCSLA) (43 U.S.C. § 1334(a)(8)) to comply 

with the National Ambient Air Quality Standards (NAAQS) to the extent that Outer Continental Shelf 

(OCS) offshore oil and gas exploration, development, and production sources do not significantly 

affect the air quality of any state. The Gulf of Mexico OCS Region’s area of possible influence 

includes the States of Texas, Louisiana, Mississippi, Alabama, and Florida. BOEM’s Gulf of Mexico 

Region manages the responsible development of oil, gas, and mineral resources for the 

430 million acres in the Western, Central, and Eastern Planning Areas on the OCS, including the 

areas under moratoria (shown in Figure B-1). The Clean Air Act Amendments (CAAA) of 1990 

designate air quality authorities, giving BOEM air quality jurisdiction westward of 87°30'W. longitude 

and the U.S. Environmental Protection Agency (USEPA) air quality jurisdiction eastward of 87°30'W. 

longitude. In 2006, oil and gas leasing operations within 125 miles (201 kilometers [km]) of the 

Florida coastline were banned until 2022 under the Gulf of Mexico Energy Security Act (GOMESA). 

The GOMESA moratoria area is depicted on Figure B-1. 

Figure B-1. Location of the “Air Quality Modeling in the Gulf of Mexico Region” Study with Class I 

Areas (purple) and Platform Locations (gray dots). 

The USEPA has set NAAQS for six regulated air quality pollutants: ozone; particulate matter 

with an aerodynamic diameter of 2.5 micrometers and smaller (PM2.5); particulate matter with an 
B-2 2018 Gulf of Mexico Supplemental EIS

aerodynamic diameter of 10 micrometers and smaller (PM10); sulfur dioxide (SO2); nitrogen dioxide 

(NO2); carbon monoxide (CO); and lead (Pb). After promulgation of a NAAQS, the USEPA 

designates areas that fail to achieve the NAAQS as nonattainment areas (NAAs) and States are 

required to submit State Implementation Plans (SIPs) to the USEPA that contain emission control 

plans and a demonstration that the NAA will achieve the NAAQS by the required date. After an area 

comes into attainment of the NAAQS, the area can be redesignated as a maintenance area and 

must continue to demonstrate compliance with the NAAQS.

In 1997, the USEPA promulgated the first 8-hour ozone NAAQS with a threshold of 

0.08 parts per million (ppm) (84 parts per billion [ppb]). On March 12, 2008, the USEPA 

promulgated a more stringent 0.075 ppm (75 ppb) 8-hour ozone NAAQS. Figure B-2 presents the 

current ozone nonattainment areas in the southeastern U.S. On October 1, 2015, the USEPA 

strengthened the 8-hour NAAQS for ozone to 0.07 ppm (70 ppb). Under this more stringent ozone 

NAAQS, there may be more areas in the southeastern U.S. that will be in nonattainment. The 

USEPA plans to make attainment and nonattainment designations for the revised standards by 

October 2017, with the designations based on 2014-2016 air quality data.

On December 14, 2012, the USEPA revised the PM2.5 primary NAAQS by lowering the 

annual PM2.5 NAAQS threshold from 15.0 micrograms per cubic meter (μg/m3

) to 12.0 μg/m3. The 

USEPA retained the 24-hour PM2.5 primary NAAQS at 35 μg/m3

. The 24-hour coarse PM NAAQS 

(PM10) was also retained at 150 μg/m3

. 

Figure B-2. Ozone Nonattainment Areas in the Southeastern U.S. (USEPA, 2016a). 

In February 2010, the USEPA issued a new 1-hour NO2 NAAQS with a threshold of 100 ppb 

(98th percentile daily maximum average over three-years) and a new 1-hour SO2 NAAQS was 

promulgated in June 2010 with a threshold of 75 ppb (99th percentile averaged over 3 years). The 

USEPA has not yet designated the nonattainment areas for the 1-hour NO2 and 1 hour SO2 NAAQS.
Air Quality: WRF Model Performance B-3 

A new lead NAAQS was issued in 2008; NAAs for lead are associated with specific industrial 

sources. As oil and gas sources in the Gulf of Mexico OCS region produce negligible amounts of 

lead emissions and to be consistent with onshore oil and gas analysis, which does not include lead, 

lead was not included in the air quality analysis. The NAAQS for carbon monoxide has remained 

essentially unchanged since it was originally promulgated in 1971. As of September 27, 2010, all 

NAAs for carbon monoxide have been redesignated as maintenance areas. Table B-1 summarizes 

the nonattainment and maintenance areas in the southeastern U.S.

Table B-1. Nonattainment and Maintenance Areas in the Southeastern U.S.

State Area 8-hr O3

(1997)

8-hr O3

(2008)

SO2

(2010)

Lead 

(2008)

Alabama Troy, AL NAAa

Florida

Tampa, FL NAA

Hillsborough County, FL NAA

Nassau County, FL NAA

Louisiana Baton Rouge, LA Mb NAA

St. Bernard Parish, LA NAA

Texas

Beaumont-Port Arthur, TX M

Houston-Galveston-Brazoria, 

TX NAA NAA

Frisco, TX NAA a NAA = nonattainment area

b M = maintenance area

Blank cells indicate the area is in attainment of the NAAQS.

The CAAA designated 156 Class I areas consisting of National Parks and Wilderness Areas 

that are offered special protection for air quality and air quality-related values (AQRVs). The Class I 

areas, compared to Class II areas, have lower Prevention of Significant Deterioration (PSD) air 

quality increments that new sources may not exceed and are protected against excessive increases 

in several AQRVs, including visibility impairment, acid (sulfur and nitrogen) deposition, and nitrogen 

eutrophication. The Regional Haze Rule (RHR) has a goal of natural visibility conditions by 2064 at 

Class I areas, and States must submit RHR SIPs that demonstrate progress towards that goal. 

Figure B-1 displays the locations of the mandatory Class I areas (in purple) in the Gulf of Mexico 

OCS region. In addition to the Class I areas, Federal Land Management (FLM) agencies have 

designated certain other areas as sensitive Class II areas for tracking PSD increment consumption 

and AQRV impacts.

On August 26, 2014, BOEM contracted with Eastern Research Group, Inc. (ERG) and team 

members Ramboll Environ US Corporation (Ramboll Environ) and Alpine Geophysics, LLC to 

complete a comprehensive air quality modeling study in the Gulf of Mexico OCS region. Under 

BOEM Contract Number M14PC00007, air quality photochemical grid modeling (PGM) will be 

conducted in the region to assess the impacts to nearby States of OCS oil and gas exploration, 

development, and production as required under OCSLA. This assessment is used by BOEM in the 

cumulative and visibility impacts analyses of the National Environmental Policy Act (NEPA) 
B-4 2018 Gulf of Mexico Supplemental EIS

environmental impact statements (EIS), which are the Gulf of Mexico OCS Oil and Gas Lease Sales: 

2017-2022; Gulf of Mexico Lease Sales 249, 250, 251, 252, 253, 254, 256, 257, 259, and 261—

Final Multisale Environmental Impact Statement (2017-2022 GOM Multisale EIS) and this 

Supplemental EIS. These analyses address both current and proposed NAAQS.

Air quality modeling requires several input datasets, including meteorology, emissions 

inventories, and ambient pollutant concentrations. Figure B-3 presents an overview of how these 

project datasets fit together for the “Air Quality Modeling in the Gulf of Mexico Region” study. 

Figure B-3. Overview of the “Air Quality Modeling in the Gulf of 

Mexico Region” Study Tasks. 

This report details the meteorological modeling performance evaluation (MPE) of a Weather 

and Research Forecast (WRF) model for 2012, the PGM year. A separate report (referred to herein 

as the “full WRF modeling report”) will provide a more comprehensive evaluation of the full 5-year 

WRF dataset.

Meteorological information is needed for air quality modeling. Parameters such as wind 

speed, wind direction, air temperature, and humidity are required by models to determine the rate 

that pollutants disperse and react in the atmosphere. Sources of meteorological information include 

datasets of measurements gathered at various locations within the Gulf of Mexico OCS Region’s

domain. However, the spatial coverage of measurements is insufficient to describe the 

three-dimensional structure of the atmosphere away from measurement locations. Using 

measurement data as inputs, gridded meteorological models capable of simulating the fluid 

dynamics of the atmospheric data can be used to estimate meteorological conditions over a 

complete modeling domain—including regions far from measurement sites—in a physically 

consistent fashion. The results of these models are often used to establish conditions near remote 
Air Quality: WRF Model Performance B-5 

pollutant sources or remote locations downwind of pollutant sources. Within the domain of the Gulf 

of Mexico OCS Region, the WRF meteorological model has been identified and was used to provide 

meteorological inputs for the air quality models.

Ramboll Environ previously evaluated the existing meteorological datasets and concluded 

that enough deficiencies were present in the datasets and there were not enough positive attributes 

to select any of them for air quality modeling in the study area (Brashers et al., official 

communication, 2014) and, therefore, new meteorological modeling was required. One purpose of 

the modeling is to provide the meteorological dataset for the 2012 simulation using PGM modeling in 

the OCS region. 

B.2 WRF MODELING METHODOLOGY

Over the past decade, emergent requirements for numerical simulation of urban and regional 

scale air quality have led to intensified efforts to construct high-resolution emissions, meteorological 

and air quality datasets. It is now possible, for example, to exercise sophisticated mesoscale 

prognostic meteorological models and Eulerian and Lagrangian photochemical/aerosol models for 

multi-seasonal periods over near-continental scale domains in a matter of weeks with the application 

tailored to a specific air quality modeling project.

The WRF model is the current preferred model for atmospheric research and operational 

forecasting needs at mesoscale resolution (approximately 5 to several hundred km). The model is 

the state-of-the-art atmospheric simulation system, commonly used to drive air quality dispersion 

models on the regional level.

The operational version of the model is the Nonhydrostatic Mesoscale Model (NMM) WRF 

core version 3, developed and maintained by the U.S. Department of Commerce’s National Oceanic 

and Atmospheric Administration (NOAA) and the National Centers for Environmental Prediction 

(NCEP). The Advanced Research WRF (ARW) core, currently version WRF 3.7.1, is supported by 

the National Center for Atmospheric Research (NCAR), Mesoscale and Microscale Meteorology 

Division (NCAR, 2015). The modeling described in this report used WRF version 3.7.

The WRF model contains separate modules to compute different physical processes such as 

surface energy budgets and soil interactions, turbulence, cloud microphysics, and atmospheric 

radiation. Within WRF, the user has many options for selecting the different schemes for each type 

of physical process. There is a WRF Pre-processing System (WPS) that generates the initial and 

boundary conditions used by WRF, based on topographic datasets, land use information, and largerscale atmospheric and oceanic models.

B.2.1 Gulf of Mexico Region Air Quality Meteorological Modeling

The USEPA CONUS WRF and Ramboll Environ Training WRF datasets were previously 

examined in detail and evaluated using both quantitative and qualitative techniques. Both datasets 

were identified as being inadequate for the study area, particularly in the offshore portions (Brashers
B-6 2018 Gulf of Mexico Supplemental EIS

et al., official communication, 2014). The development of a new high-resolution dataset was 

necessary to more accurately represent meteorological conditions in the over-water portions of the 

OCS region for use in air quality modeling.

B.2.2 Model Domain Configuration

The WRF domain configuration is comprised of a system of simultaneous nested grids. 

Figure B-3 shows the WRF modeling grids at 36/12/4 km. All WRF grids are defined on a Lambert 

Conformal Conic (LCC) projection centered at 40°N. latitude, 97°W. longitude with true latitudes at 

33°N. and 45°N. (the “standard RPO” projection). The outermost domain (outer box) with 36-km 

resolution includes the entire continental U.S. and parts of Canada and Mexico, and captures 

synoptic-scale (storm system-scale) structures in the atmosphere. The inner 12-km regional grid 

(d02) covers the southeastern U.S. and was used to ensure that large-scale meteorological patterns 

across the region are adequately represented and to provide boundary conditions to the 

4-km domain.

The 4-km domain (d03) shown in Figure B-4 is centered on the coastal areas of the 

southeastern U.S. and over-water portions of the Gulf of Mexico. Table B-2 provides the input 

configurations for this WRF domain. The NX and NY are the number of east-west and north-south 

staggered grid points, respectively, in each domain. I-start and J-start indicate the western and 

southern nested grid starting indices with respect to the parent grid. Geographic resolution relates to 

the geographic datasets employed for each grid in terms of minutes or seconds of degrees. 

The 36-, 12-, and 4-km grids were run simultaneously with one-way nesting, meaning that 

meteorological information flows down-scale via boundary conditions introduced from the coarser to 

finer grids without feedback from the finer to coarser grids. The WRF modeling domain was defined 

to be slightly larger than the CAMx/CMAQ PGM modeling domains to eliminate boundary artifacts in 

the meteorological fields. Such boundary artifacts occur for both numerical reason (the 3:1 grid 

spacing ratio) and because the imposed boundary conditions require some time/space to come into 

dynamic balance with WRF’s atmospheric equations. 

Table B-2. BOEM’s Gulf of Mexico OCS Region WRF Domain Configuration. 

Grid Resolution NX NY I-start J-start Geographic Resolution Coverage

36 km 165 129 1 1 10 minute CONUS

12 km 265 187 55 9 2 minute SE CONUS

4 km 481 211 72 27 30 second OCS Region

 
Air Quality: WRF Model Performance B-7 

Figure B-4. WRF 36-km CONUS (d01), 12-km SE Regional (d02), and 4-km Gulf of Mexico Region 

(d03) Domains. 

B.2.3 Model Application

The publicly available version of WRF, version 3.7, was used in the Gulf of Mexico OCS 

Region’s meteorological modeling. The WRF pre-processor programs, including GEOGRID, 

UNGRIB, METGRID, and OBSGRID, were used to develop model inputs. 

B.2.3.1 Model Vertical Resolution

The dataset was tested using both 33 and 37 vertical layers. Thirty-seven vertical layers 

allowed for higher vertical resolutions near the surface, which enabled the model to more accurately 

capture low-level inversions frequently present during winter. Additional layers in the mid-levels also 

allowed the model to more accurately re-create the convective updraft velocities seen in the summer 

months. The dataset model levels are shown in Table B-3. 
B-8 2018 Gulf of Mexico Supplemental EIS

Table B-3. BOEM Gulf of Mexico OCS Region WRF Dataset Model Levels.

Level eta Pressure (mb) Height (m) Mid Height (m) Thickness (m)

0 1 1,000 0.0

1 0.9985 999 12.2 6.1 12.2

2 0.9970 997 24.5 18.4 12.2

3 0.9950 995 40.8 32.7 16.4

4 0.9930 993 57.2 49.0 16.4

5 0.9910 991 73.6 65.4 16.4

6 0.9880 989 98.3 85.9 24.7

7 0.9850 986 123.0 110.6 24.7

8 0.9800 981 164.3 143.6 41.3

9 0.9700 972 247.4 205.9 83.1

10 0.9600 962 331.2 289.3 83.8

11 0.9500 953 415.7 373.4 84.5

12 0.9400 943 500.8 458.2 85.1

13 0.9300 934 586.6 543.7 85.8

14 0.9100 915 760.5 673.5 173.8

15 0.8900 896 937.2 848.8 176.8

16 0.8700 877 1,117.1 1,027.1 179.8

17 0.8400 848 1,392.8 1,254.9 275.8

18 0.8000 810 1,772.4 1,582.6 379.6

19 0.7600 772 2,166.7 1,969.6 394.3

20 0.7200 734 2,577.0 2,371.9 410.3

21 0.6800 696 3,005.0 2,791.0 427.9

22 0.6400 658 3,452.2 3,228.6 447.3

23 0.6000 620 3,921.0 3,686.6 468.7

24 0.5500 573 4,540.7 4,230.8 619.8

25 0.5000 525 5,203.7 4,872.2 662.9

26 0.4500 478 5,917.1 5,560.4 713.4

27 0.4000 430 6,690.5 6,303.8 773.4

28 0.3500 383 7,536.4 7,113.5 846.0

29 0.3000 335 8,472.3 8,004.4 935.8

30 0.2500 288 9,522.5 8,997.4 1,050.2

31 0.2000 240 10,724.1 10,123.3 1,201.6

32 0.1500 193 12,136.7 11,430.4 1,412.6

33 0.1000 145 13,866.9 13,001.8 1,730.1

34 0.0600 107 15,621.6 14,744.2 1,754.7

35 0.0270 76 17,503.4 16,562.5 1,881.8

36 0.0000 50 19,594.2 18,548.8 2,090.8

B.2.3.2 Topographic Inputs

Topographic information for WRF was developed using the standard WRF terrain databases 

available from NCAR. The 36-km CONUS domain was based on the 10-min (18-km) global data. 

The 12-km southeastern CONUS domain was based on the 2 min (~4-km) data. The 4-km Gulf of 

Mexico OCS region domain was based on the 30-sec (~900-m) data.
Air Quality: WRF Model Performance B-9 

B.2.3.3 Vegetation Type and Land Use Inputs

Vegetation type and land-use information was developed using the U.S. Department of the 

Interior, Geological Survey (USGS) land-use database from the most recently released WRF 

databases provided with the WRF distribution. The number of land categories in input data was the 

USGS default of 24. Standard WRF surface characteristics corresponding to each land-use 

category were employed.

B.2.3.4 Atmospheric Data Inputs

The WRF relies on some other model or re-analysis output to provide initial and boundary 

conditions (IC/BC). Sensitivity tests were performed on several datasets to evaluate their 

effectiveness over the Gulf of Mexico. The datasets tested include the ERA-Interim reanalysis 

product, available from the European Center for Medium-range Weather Forecasting (ECMWF) Data 

Portal website; the Climate Forecast System Reanalysis (CFSR, ended in 2010), and the Climate 

Forecast System model version 2 (CFSv2, after 2010) (Saha et al., 2014); and the 12-km North 

American Model (NAM) archives available from the National Climatic Data Center (NCDC) NOMADS 

server.

The NAM dataset was chosen for the lowest bias and error in model performance and was 

used as first guess fields for WRF. This dataset was objectively re-analyzed using traditional 

observation site data (meteorological towers) to the higher resolution of each WRF grid, using the 

OBSGRID program. These fields are then used both to initialize the model and to conduct analysis 

nudging to guide the model to best match the observations.

B.2.3.5 Time Integration

Adaptive time stepping was used to maximize the time step that the model can use while 

keeping the model numerically stable. The model time step was adjusted based on the domain-wide 

horizontal and vertical stability Courant-Friedrichs-Lewy (CFL) target value of 0.8.

B.2.3.6 Diffusion Options

Horizontal Smagorinsky first-order closure (km_opt = 4) with sixth-order numerical diffusion 

and suppressed up-gradient diffusion (diff_6th_opt = 2) was used.

B.2.3.7 Lateral Boundary Conditions

Lateral boundary conditions were specified from the initialization dataset on the 36-km 

domain with continuous updates nested from the 36-km domain to the 12-km domain and from the 

12-km domain to the 4-km domain, using one-way nesting (feedback = 0).
B-10 2018 Gulf of Mexico Supplemental EIS

B.2.3.8 Top and Bottom Boundary Conditions

The top boundary condition was selected as an implicit Rayleigh dampening for the vertical 

velocity. Consistent with the model application for non-idealized cases, the bottom boundary 

condition was selected as physical, not free-slip.

B.2.3.9 Sea-Surface Temperature Inputs

High-resolution, sea-surface temperature (SST) inputs aid in improving meteorological 

conditions for the over-water portions of the Gulf of Mexico OCS region. The Fleet Numerical 

Meteorology and Oceanography Center (FNMOC) dataset, available from the Global Ocean Data 

Assimilation Experiment (GODAE) archives, was selected after extensive testing of several SST 

databases. The FNMOC high-resolution database is updated every 6 hours using satellite-derived 

(AVHRR) SST and in-situ SST from ships and buoys with resolutions, ranging from 12 km at the 

equator to 9 km at the mid-latitudes. The FNMOC SST database was chosen for the lowest SST 

bias and error in model performance evaluation tests, which used open water observations from the 

National Data Buoy Center (NDBC) archives.

B.2.3.10 FDDA Data Assimilation

The WRF was created as a forecast tool, but it can also be applied in “hindcast” mode. In 

forecast mode, the initial conditions for a run might be the most recent analysis (a gridded version of 

the current state of the atmosphere). In hindcast mode, we know the state of the atmosphere both 

at the beginning and end of (and during) the WRF run. Using these 6-hourly analyses, an extra error 

term is introduced into the WRF equations, nudging the WRF atmosphere toward the real 

atmosphere. This is known as Four Dimensional Data Assimilation (FDDA) or analysis nudging and 

is applied to every grid cell in the domain. It works best at larger grid spacing scales and for larger 

domains.

Observational nudging is the process of nudging just the single grid cell toward a single-point 

observation. The observation could be taken at a traditional meteorological tower or by a weather 

balloon or other non-traditional sources. Observation nudging works best at finer grid spacing 

scales and could have been performed on higher resolution domains using the Meteorological 

Assimilation Data Ingest System (MADIS) observation archive.

The WRF model was run with analysis nudging and no observation nudging. For winds and 

temperature, analysis nudging coefficients of 5x10-4 and 3.0x10-4 were used on the 36- and 12-km 

domains, respectively. For mixing ratio, an analysis nudging coefficient of 1.0x10-5 was used for 

both the 36- and 12-km domains. Analysis nudging of winds was applied both at near the surface 

and aloft, but nudging for temperature and mixing ratio was not performed in the lower atmosphere 

(i.e., within the boundary layer).

Significant sensitivity testing was used to evaluate impacts of observational nudging on the 

4-km domain. The observational nudging coefficients for winds were tested at values set from 0 to 
Air Quality: WRF Model Performance B-11

1.2x10-3 with a radius of influence at 50 km. Ramboll Environ concluded that any observational 

nudging coefficient for winds above zero caused excessive convection in the offshore portions of the 

Gulf of Mexico, resulting in an extreme overstatement of precipitation. Additionally, humidity nudging 

was tested at values ranging from 0 to 1.0x10-5. The lower nudging values also prevented excess 

moisture in the model, primarily through the summer months. Setting wind, temperature, and 

moisture coefficients all to zero produced the most accurate precipitation results and are very similar 

to the nudging used in the USEPA 2011 CONUS WRF dataset (Gilliam and Pleim, 2010).

B.2.3.11 WRF Physics Options

The WRF model contains many different physics options. Model tests for the months of 

January and July 2012 were performed to evaluate various cumulus parameterizations, times 

between radiation physics calls, and land surface models to achieve the best WRF performance in 

the dataset. Table B-4 lists the BOEM Gulf of Mexico OCS Region WRF physics options.

Table B-4. BOEM Gulf of Mexico OCS Region WRF Physics Options. 

Option Scheme Notes

Microphysics Thompson State-of-the-art microphysics model

Longwave Radiation RRTMG

Rapid Radiative Transfer Model for GCMs 

includes random cloud overlap and 

improved efficiency over RRTM.

Shortwave Radiation RRTMG Same as above, but for shortwave 

radiation.

Land Surface Model 

(LSM) Noah Four-layer scheme with vegetation and sub-grid tiling.

Planetary Boundary 

Layer (PBL) scheme YSU

Yonsie University (Korea) Asymmetric 

Convective Model with non-local upward 

mixing and local downward mixing.

Cumulus 

Parameterization

Kain-Fritsch in the 36-km and 

12-km domains.

Deep and shallow convection sub-grid 

scheme using a mass flux approach with 

downdrafts and CAPE removal time scale.

Analysis Nudging

Nudging applied to winds, 

temperature and moisture in the

36-km and 12-km domains.

Temperature and moisture nudged above 

PBL only.

Observation Nudging No nudging applied

Surface wind and moisture observational 

nudging can induce excessive convection, 

leading to increased rainfall.

Surface Layer Revised MM5 Monin-Obukhov 

scheme In conjunction with YSU PBL scheme.

B.2.3.12 WRF Application Methodology

The WRF model was executed in 5-day blocks initialized at 12Z every 5 days for calendar 

year 2012. Model results are output every 60 minutes and output files are split at 12-hour intervals. 

Twelve (12) hours of spin-up were included in each 5-day block before the data were used in the 

subsequent evaluation. 
B-12 2018 Gulf of Mexico Supplemental EIS

B.3 WRF MODEL PERFORMANCE EVALUATION RESULTS

A quantitative and qualitative evaluation of the BOEM Gulf of Mexico OCS Region WRF 

simulation was conducted. The quantitative evaluation compared integrated surface hourly 

meteorological observations and offshore buoy observations with WRF predictions matched by time 

and location. The qualitative evaluation compared twice daily vertical profiles with upper-air data 

with WRF predictions matched by time and location and wind roses of coastal sites. Additionally, 

monthly and daily total spatial precipitation fields based on observations and satellite were compared 

with the WRF gridded monthly and daily total precipitation fields. Below, we summarize the main 

features of the WRF simulation model performance evaluation.

B.3.1 Quantitative Evaluation Using Metstat

A quantitative model performance evaluation of the BOEM Gulf of Mexico OCS Region WRF 

simulation was performed using integrated hourly surface and on-site meteorological measurements 

and the publicly available METSTAT software (Ramboll Environ, 2015) evaluation tool. METSTAT 

calculates statistical performance metrics for bias, error and correlation for surface winds, 

temperature, and mixing ratio (i.e., water vapor or humidity). To evaluate the performance of a 

meteorological model simulation for air quality model applications, a number of performance 

benchmarks for comparison are typically used. Table B-5 lists the meteorological model 

performance benchmarks for simple (Emery et al., 2001) and complex (Kemball-Cook et al., 2005) 

situations. The simple benchmarks were developed by analyzing well-performing meteorological 

model evaluation results for simple, mostly flat terrain conditions and simple meteorological 

conditions (e.g., stationary high pressure) that were mostly conducted to support air quality modeling 

studies (e.g., ozone SIP modeling). The complex benchmarks were developed during the Western 

Regional Air Partnership (WRAP) regional haze modeling and are performance benchmarks for 

more complex conditions, such as the complex terrain of the Rocky Mountains and Alaska 

(Kemball-Cook et al., 2005). McNally (2009) analyzed multiple annual runs that included complex 

terrain conditions and suggested an alternative set of benchmarks for temperature under more 

complex conditions. The purpose of the benchmarks is to understand how good or poor the results 

are relative to other model applications run for the U.S. 

In this section, Ramboll Environ compare the WRF meteorological variables to the 

benchmarks as an indication of the BOEM Gulf of Mexico OCS Region WRF model performance. 

These benchmarks include bias and error in temperature, wind direction, and mixing ratio, as well as 

the wind speed bias and Root Mean Squared Error (RMSE) between the models and databases.

Table B-5. Meteorological Model Performance Benchmarks for Simple and Complex Conditions. 

Parameter Emery et al. (2001) Kemball-Cook et al. (2005) McNally (2009)

Conditions Simple Complex Both

Temperature Bias ≤ ±0.5 K ≤ ±2.0 K ≤ ±1.0 K

Temperature Error ≤ 2.0 K ≤ 3.5 K ≤ 3.0 K

Temperature IOA ≥ 0.8 (not addressed) (not addressed)

Humidity Bias ≤ ±1.0 g/kg ≤ ±0.8 g/kg ≤ ±1.0 g/kg
Air Quality: WRF Model Performance B-13

Parameter Emery et al. (2001) Kemball-Cook et al. (2005) McNally (2009)

Humidity Error ≤ 2.0 g/kg ≤ 2.0 g/kg ≤ 2.0 g/kg

Humidity IOA ≥ 0.6 (not addressed) (not addressed)

Wind Speed Bias ≤ ±0.5 m/s ≤ ±1.5 m/s (not addressed)

Wind Speed RMSE ≤ 2.0 m/s ≤ 2.5 m/s (not addressed)

Wind Speed IOA ≥ 0.6 (not addressed) (not addressed)

Wind Dir. Bias ≤ ±10 degrees (not addressed) (not addressed)

Wind Dir. Error ≤ 30 degrees ≤ 55 degrees (not addressed)

The output from the BOEM Gulf of Mexico OCS Region WRF simulation was compared 

against the NCDC’s global-scale, quality-controlled DS3505 integrated surface hourly observational 

(ISHO) data (USDOC, NOAA, NCDC, 2015) and the NDBC’s buoy database (USDOC, NOAA, 

NDBC, 2015) as verification data. Global hourly and synoptic observations are compiled from 

numerous sources into a single common ASCII format and common data model. The DS3505 

database contains records of most official surface meteorological stations from airports, military 

bases, reservoirs/dams, agricultural sites, and other sources dating from 1901 to the present, and 

quality control has corrected well over 99% of the errors present in the original data. The NDBC 

database contains records of moored buoys, coastal-marine automated network stations, and other 

sources dating from 1970 to the present.

B.3.1.1 Quantitative Statistics

Several statistical measures are calculated as part of the meteorological model evaluation. 

Additional plots and graphs are used to present these statistics on both hourly and daily timeframes. 

These measures are calculated for wind speed, wind direction, temperature, and humidity at the 

surface. The various statistical measures used for this evaluation are described below. 

The statistics used to evaluate meteorological model performance are all given in absolute 

terms (e.g., wind speed error in meters per second [m/s]) rather than in relative terms (percent error) 

as is commonly shown for air quality assessments. The major reason for this is that a very different 

significance is associated with a given relative error for different meteorological parameters. For 

example, a 10 percent error for wind speed measured at 10 m/s is an absolute error of 1 m/s, a 

minor error. Yet a 10 percent error for temperature at 300 K is an absolute error of 30 K, an 

unacceptably large error. On the other hand, pollutant concentration errors of 10 percent at 1 ppb or 

10 ppm carry practically the same significance.

Statistical Measures

Mean Observation (Mo): Calculated from all sites with valid data within a given analysis region and 

for a given time period (hourly or daily):
B-14 2018 Gulf of Mexico Supplemental EIS

∑∑= =

=

J

j

I

i

i

o Oj IJ

M

1 1

1

where Oi

j is the individual observed quantity at site i and time j, and the summations are over all 

sites (I) and over time periods (J).

Mean Prediction (Mp): Calculated from simulation results that are interpolated to each observation 

used to calculate the mean observation (hourly or daily):

∑∑= =

=

J

j

I

i

i

p Pj IJ

M

1 1

1

where Pi

j is the individual predicted quantity at site i and time j. Note that mean observed and 

predicted winds are vector-averaged (for east-west component u and north-south component v), 

from which the mean wind speed and mean resultant direction are derived. 

Least Square Regression: Performed to fit the prediction set to a linear model that describes the 

observation set for all sites with valid data within a given analysis region and for a given time 

period (daily or episode). The y-intercept a and slope b of the resulting straight line fit is 

calculated to describe the regressed prediction for each observation:

i

j

i

j += bOaP

The goal is for a 1:1 slope and a “0” y-intercept (no net bias over the entire range of 

observations), and a regression coefficient of 1 (a perfect regression). The slope and intercept 

facilitate the calculation of several error and skill statistics described below.

Bias Error (B): Calculated as the mean difference in prediction-observation pairings with valid data 

within a given analysis region and for a given time period (hourly or daily):

∑∑( ) = =

= −

J

j

I

i

i

j

i

j OP

IJ

B

1 1

1

Gross Error (E): Calculated as the mean absolute difference in prediction-observation pairings with 

valid data within a given analysis region and for a given time period (hourly or daily):

∑∑= =

= −

J

j

I

i

i

j

i

j OP

IJ

E

1 1

1

Note that the bias and gross error for winds are calculated from the predicted-observed residuals 

in speed and direction (not from vector components u and v). The direction error for a given 

prediction-observation pairing is limited to range from 0 to 180.

Root Mean Square Error (RMSE): Calculated as the square root of the mean squared difference in 

prediction-observation pairings with valid data within a given analysis region and for a given time 

period (hourly or daily):
Air Quality: WRF Model Performance B-15

( )

2/1

1 1

1 2





 



 = ∑∑ − = =

J

j

I

i

i

j

i

j OP

IJ

RMSE

The RMSE, as with the gross error, is a good overall measure of model performance. However, 

since large errors are weighted heavily (due to squaring), large errors in a small sub-region may 

produce a large RMSE even though the errors may be small and quite acceptable elsewhere.

It is important that RMSE is analyzed. For example, if only RMSE is estimated (and it 

appears acceptable), it could consist largely of the systemat¬ic component. This error might be 

removed through improvements in the model inputs or use of more appropriate options, thereby 

reducing the error transferred to the photochemical model. On the other hand, if the RMSE consists 

largely of the unsystematic component, this indicates that further error reduction may require model 

refinement (new algorithms, higher resolution grids, etc.) or that the phenomena to be replicated 

cannot be fully addressed by the model. It also provides error bars that may be used with the inputs 

in subsequent sensitivity analyses.

B.3.1.2 METSTAT Evaluation Using Integrated Surface Hourly Observations and Offshore 

Buoy Observations

The METSTAT results for 2012 are presented in Figures B-5 through B-16. The WRF wind 

direction performed very well, with the majority of months falling within the simple conditions 

threshold for all spatial domains (36, 12, and 4 km). For all domains, WRF wind speed, temperature, 

and humidity also performed very well. For most months, there are slight positive biases in wind 

speed and humidity in all three spatial domains. Overall, the WRF model performed exceptionally 

well in the 36- and 12-km domains and well in the 4-km domain for onshore surface wind direction, 

wind speed, humidity and temperature observation comparisons.

METSTAT was also used to evaluate WRF performance in the innermost 4-km domain using 

observations from meteorological buoys throughout the Gulf of Mexico for 2012. Overall, WRF wind 

direction performed well with over half of all months falling with the simple conditions benchmark. 

Wind speed performance was acceptable with all months falling within the complex conditions 

benchmark. Temperature bias and error is slightly higher (warmer) in the winter months compared 

to the summer months, suggesting that the model is over-forecasting surface temperatures, or is an 

influence from the SST database input to WRF. Humidity performed well with a majority of months, 

falling within the simple conditions benchmark. In general, the offshore METSTAT evaluation is very 

similar to the onshore evaluation, suggesting consistent performance over both the land and sea 

portions of the Gulf of Mexico OCS region. 
B-16 2018 Gulf of Mexico Supplemental EIS

Figure B-5. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Wind Direction 

Performance for 2012. 

Figure B-6. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Wind Speed 

Performance for 2012. 
Air Quality: WRF Model Performance B-17

Figure B-7. BOEM Gulfof Mexico OCS Region WRF 36-km METSTAT Temperature 

Performance for 2012. 

Figure B-8. BOEM Gulf of Mexico OCS Region WRF 36-km METSTAT Humidity Performance 

for 2012. 
B-18 2018 Gulf of Mexico Supplemental EIS

Figure B-9. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Wind Direction 

Performance for 2012. 

Figure B-10. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Wind Speed 

Performance for 2012. 
Air Quality: WRF Model Performance B-19

Figure B-11. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Temperature 

Performance for 2012. 

Figure B-12. BOEM Gulf of Mexico OCS Region WRF 12-km METSTAT Humidity Performance 

for 2012. 
B-20 2018 Gulf of Mexico Supplemental EIS

Figure B-13. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Wind Direction 

Performance for 2012. 

Figure B-14. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Wind Speed Performance 

for 2012. 
Air Quality: WRF Model Performance B-21

Figure B-15. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Temperature 

Performance for 2012. 

Figure B-16. BOEM Gulf of Mexico OCS Region WRF 4-km METSTAT Humidity Performance for 

2012. 
B-22 2018 Gulf of Mexico Supplemental EIS

B.3.2 Qualitative Evaluation Using Wind Roses

The coastal sites of Gulfport, MS (KGPT); Naples, FL (NPSF); Port Isabel, TX (PTIT); and 

Calcasieu, LA (CAPL) were chosen to evaluate the frequency and intensity of onshore and offshore 

wind flow and WRF’s performance at the land-sea interface. The locations of these sites are shown 

in Figure B-17. The 5-year comparisons of observed and modeled wind direction at each coastal 

site will be provided in the full WRF modeling report. Below, in Figures B-17 through B-21, the 

comparisons are made for only 2012. Wind direction observations were obtained from the DS3505 

meteorological dataset, and modeled surface wind speed and wind direction were extracted from the 

4-km WRF domain dataset using the Mesoscale Model Interface (MMIF) program (Brashers and 

Emery, 2015). Overall, WRF performs just satisfactorily at forecasting the frequency and intensity of 

onshore and offshore wind flow at the coastal sites. The WRF simulates the predominant NE wind 

direction at NPSF, as well as the strong SE winds at port PTIT and CAPL. However, WRF wind 

direction does not compare particularly well to KGPT in 2012 and does not replicate much of the NW 

wind at PTIT, or the SW wind at NPSF. The decline in apparent wind direction performance for 

2012, compared to the 5-year analysis, is largely due to the shorter evaluation period.

Figure B-17. Wind Rose Locations for Port Isabel, TX (PTIT), Calcasieu, LA (CAPL), Gulfport, MS 

(KGPT), and Naples, FL (NPSF). 
Air Quality: WRF Model Performance

B-23

Figure B-18. 2012 WRF Wind Rose (left) Compared to 2012 Observation Wind Rose from Gulfport, MS (right) in 4-km Domain. 
B-24 2018 Gulf of Mexico Supplemental EIS

Figure B-19. 2012 WRF Wind Rose (left) Compared to 2012 Observation Wind Rose from Naples, FL (right) in 4-km Domain. 
Air Quality: WRF Model Performance

B-25

Figure B-20. 2012 WRF Wind Rose (left) Compared to 2012 Observation Wind Rose from Port Isabel, TX (right) in 4-km Domain. 
B-26 2018 Gulf of Mexico Supplemental EIS

Figure B-21. 2012 WRF Wind Rose (left) Compared to 2012 Observation Wind Rose from Calcasieu, LA (right) in 4-km Domain. 
Air Quality: WRF Model Performance B-27

B.3.3 Qualitative Evaluation Using Upper-Air Data

Plots of the sounding profiles of temperature and dew point for the vertical atmosphere were 

created using observational data from the Brownsville, TX (KBRO) and Key West, FL (KEYW) 

airports and the corresponding WRF data points. A random selection of upper air profiles was taken 

from the year-long dataset for a sampling of several different atmospheric situations. These are 

qualitatively compared, paying particular attention to how well the WRF model reproduces the 

observed near-surface inversion layers.

The KBRO and KEYW radiosonde datasets are collected by and maintained by the National 

Weather Service (NWS). Radiosondes are launched twice per day, at approximately 00 and 

12 UTC. Radiosondes provide high-resolution vertical profiles of temperature, humidity, wind speed, 

and wind direction throughout the troposphere. The data are made publicly available by NOAA’s 

Earth System Research Laboratory (USDOC, NOAA, ESRL, 2015). Ramboll Environ downloaded 

and stored the radiosonde data twice daily for 2012 for each upper air station in FSL format for use 

in WRF model dataset comparisons. 

For the qualitative analysis, Figure B-22 shows the vertical profiles of temperature and 

humidity from the observational and 4 km WRF datasets for Brownsville, TX and Key West, FL. The 

analysis focuses on how well the WRF model reproduces the vertical atmosphere structure using 

upper air observations from the selected sites within the 4-km domain, which have timeframes that 

overlap with the WRF model. The left panel in Figure B-22 shows an evening sounding in August 

for Brownville, TX, which contains a weak elevated subsidence inversion. The WRF forecasts the 

base of the inversion well at around 900 meters. The right panel of Figure B-22 shows observed 

and modeled vertical profiles for January in Key West, FL. The WRF forecasts the elevated 

subsidence inversion well, with a mixing height top at around 1,000 meters on the left panel. The 

dry air above the inversion is also represented well in the evening sounding at Key West, FL.
B-28 2018 Gulf of Mexico Supplemental EIS

Figure B-22. Vertical Profile Soundings Comparing the 4-km WRF (blue lines) to Upper-Air Observations Data (red lines) for 

Brownsville, TX on August 3, 2012, and Key West, FL on January 4, 2012, at 00 UTC. 
Air Quality: WRF Model Performance B-29

B.3.4 Qualitative Evaluation Using Precipitation

Precipitation removes chemicals and particulates from the air via wet deposition, and thus is 

an important parameter for high-quality dispersion modeling. Several precipitation datasets were 

evaluated for use in model comparisons. Ramboll Environ has used the Parameter-elevation 

Regressions on Independent Slopes Model (PRISM) dataset for rainfall extensively in the past, but it 

only covers the over-land portion of the modeling domain. Land-based RADAR retrievals of 

precipitation typically have larger uncertainty and are limited in geographic coverage to the area 

relatively near the coast and, as a result, were not chosen for this performance evaluation. Satellitebased retrievals are typically lower resolution and also feature larger uncertainty, but cover the entire 

Gulf of Mexico OCS region. Ramboll Environ performed comparisons between the BOEM Gulf of 

Mexico OCS Region WRF modeled precipitation output with the PRISM and Tropical Rainfall 

Measurements Mission (TRMM) satellite datasets.

The Oregon State University PRISM Climate Group gathers temperature and precipitation 

data from a range of monitoring networks, applies sophisticated quality control methods, and uses 

the data to produce spatial grids of climate parameters (Daly et al., 2008). The time series datasets 

are modeled using climatologically-aided interpolation (CAI), which uses the long-term average 

pattern as first-guess of the spatial pattern of climatic conditions. Both a daily product and a monthly 

product are available. The precipitation observations used in the daily PRISM product includes 

radar measurements, which the monthly product does not take into account. This may cause 

dramatic local differences between the two datasets in monthly totals.

TRMM was a joint mission being flown by the National Aeronautics and Space 

Administration (NASA, U.S.) and the Japan Aerospace Exploration Agency (JAXA, Japan) to 

improve our quantitative knowledge of the 3-dimensional distribution of precipitation in the tropics. 

TRMM had a passive microwave radiometer (TRMM Microwave Imager, TMI), the first active spaceborne Precipitation Radar (PR), a Visible-Infrared Scanner (VIRS), and other instruments. 

Coordinated observations are intended to result in a "flying raingauge" capability. The TRMM 

dataset is coarser than the PRISM data (0.5 degrees, or about 55 km, vs. 4 km) but is available 

every 3 hours.

B.3.4.1 Evaluation Over Land Using PRISM Precipitation

High-resolution (4 km) PRISM datasets cover the contiguous U.S. in both monthly and daily 

output versions (Daly et al., 2008). Here WRF precipitation output is compared to the PRISM 

over-land portions of the Gulf of Mexico. Ramboll Environ re-projected and aggregated the PRISM 

data to the WRF projection’s grid cell locations, and the resulting gridded data was plotted and the 

gridded fields saved. This allows for consistent visual qualitative comparison.

The full WRF modeling report will display 5-year average (2010-2014) monthly precipitation 

plots constructed from BOEM Gulf of Mexico OCS Region WRF output, masked to only display 

over-land measurements, and compared to PRISM 5-year average (2010-2014) monthly plots for 

January through December in the 4-km domain. Below, WRF monthly precipitation totals are 
B-30 2018 Gulf of Mexico Supplemental EIS

compared to corresponding PRISM totals for 2012 only. The results are mostly representative of the 

5-year monthly averages and are briefly summarized in the following paragraph.

For the months of January through March, shown in Figures B-23 through B-25, WRF 

represents the spatial extent of the precipitation well, recreating the comparatively drier areas of 

central Texas and southern Florida. However, the model does under-estimate the total amount of 

average monthly rainfall across a small portion of southern Mississippi and south central Louisiana 

during this period. In April and May, Figures B-26 and B-27, the model shifts to overestimating 

rainfall in the same region, but otherwise depicts both the spatial distribution and amount of 

precipitation well over land, compared to PRISM. During the summer months of June through 

August, shown in Figures B-28 through B-30, WRF performs exceptionally well in re-creating the 

precipitation extent across the land portions of the domain, including the convergence zones across 

the east and west coasts of Florida. The model does slightly over-predict the amount of rainfall 

accumulations in the southern Georgia and southern Alabama areas. This is likely due to the higher 

humidity rates in the model during the summertime period. In September, shown in Figure B-31, 

WRF slightly under-predicts averaged precipitation rates over the land portion of the domain but 

over-forecasts the extent of rainfall over the northern Florida area. The WRF performed 

exceptionally well from October through December, shown in Figures B-32 through B-34, 

reproducing the extent and amount of rainfall very accurately, compared to PRISM totals. Overall, 

WRF performed very well in reproducing the spatial extent of precipitation over the land portions of 

Gulf of Mexico OCS region throughout 2012.
Air Quality: WRF Model Performance B-31

Figure B-23. January 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
B-32 2018 Gulf of Mexico Supplemental EIS

Figure B-24. February 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
Air Quality: WRF Model Performance B-33

Figure B-25. March 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
B-34 2018 Gulf of Mexico Supplemental EIS

Figure B-26. April 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
Air Quality: WRF Model Performance B-35

Figure B-27. May 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
B-36 2018 Gulf of Mexico Supplemental EIS

Figure B-28. June 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
Air Quality: WRF Model Performance B-37

Figure B-29. July 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
B-38 2018 Gulf of Mexico Supplemental EIS

Figure B-30. August 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
Air Quality: WRF Model Performance B-39

Figure B-31. September 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
B-40 2018 Gulf of Mexico Supplemental EIS

Figure B-32. October 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
Air Quality: WRF Model Performance B-41

Figure B-33. November 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
B-42 2018 Gulf of Mexico Supplemental EIS

Figure B-34. December 2012 PRISM Precipitation (top) and WRF Precipitation (bottom), 4-km Domain. 
Air Quality: WRF Model Performance B-43

B.3.4.2 Evaluation Over Water Using Satellite Precipitation

In this analysis, WRF precipitation data are also compared to TRMM satellite precipitation 

data to assess the accuracy of the WRF precipitation. Ramboll Environ re-projected and aggregated 

the TRMM data to the WRF projection’s grid cell locations, and the resulting gridded data was 

plotted and the gridded fields saved. This allows for a consistent visual qualitative comparison, 

although the 0.5-degree (~55-km) TRMM dataset is at a lower resolution than the 4-km PRISM 

dataset and as a result, the satellite precipitation fields appear much coarser in the 4-km domain. 

Additionally, near the end of the WRF modeling period, the satellite hosting the TRMM sensor ran 

out of propellant. This caused its orbit to slowly decay, casting into doubt the validity of the derived 

rainfall quantities and is the reason only a qualitative comparison is presented below. Below, 

Figures B-35 through B-46 show monthly WRF precipitation averages compared to TRMM 

precipitation averages throughout 2012 in the 12-km domain.

The WRF under-predicts precipitation over the offshore portions of the domain, compared to 

TRMM for the averaging months of January through May, as shown in Figures B-35 through B-39. 

From June through October, WRF performs well at predicting precipitation spatially and numerically, 

shown in Figures B-40 through B-44. The increased amount of rainfall over the southeast Gulf 

Coast States, stretching out over the coastlines, is well represented through the summertime 

months. The WRF slightly under-predicts the amount of rainfall in the offshore portions of the Gulf, 

compared to the TRMM precipitation averages for November and December, shown in Figures 

B-45 and B-46. Even with the coarse TRMM resolution, it appears the model has a slight dry bias in 

the over-water portions of the domain in the colder months.

Given the coarser resolution of the TRMM plots, WRF tends to under-forecast precipitation 

intensity overall in the offshore portions of the Gulf throughout the winter and spring months and 

does a satisfactory job at forecasting the amount of rainfall over water in the summer and fall months 

in the 4-km domain.
B-44 2018 Gulf of Mexico Supplemental EIS

Figure B-35. January 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
Air Quality: WRF Model Performance B-45

Figure B-36. February 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
B-46 2018 Gulf of Mexico Supplemental EIS

Figure B-37. March 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
Air Quality: WRF Model Performance B-47

Figure B-38. April 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
B-48 2018 Gulf of Mexico Supplemental EIS

Figure B-39. May 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
Air Quality: WRF Model Performance B-49

Figure B-40. June 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
B-50 2018 Gulf of Mexico Supplemental EIS

Figure B-41. July 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
Air Quality: WRF Model Performance B-51

Figure B-42. August 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
B-52 2018 Gulf of Mexico Supplemental EIS

Figure B-43. September 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
Air Quality: WRF Model Performance B-53

Figure B-44. October 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
B-54 2018 Gulf of Mexico Supplemental EIS

Figure B-45. November 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
Air Quality: WRF Model Performance B-55

Figure B-46. December 2012 TRMM Precipitation Average (top) and 

Corresponding WRF Precipitation Average (bottom) in the 

12-km Domain. 
B-56 2018 Gulf of Mexico Supplemental EIS

B.3.4.3 Evaluation Using Tropical Cyclone Precipitation Events

In order to evaluate the accuracy of the WRF model for precipitation performance, short-term 

rainfall events were also analyzed for local and regional scale impacts. Daily precipitation plots were 

created for every 24-hour period from the WRF, PRISM, and TRMM databases. Tropical cyclone 

events were chosen as each storm system typically produces a wide area of enhanced rainfall for 

both onshore and offshore areas.

A tropical cyclone is a warm-core, non-frontal synoptic-scale cyclone, originating over 

tropical or subtropical waters, with organized deep convection and a closed surface wind circulation 

about a well-defined center (NHC, 2015). Increased rainfall events from two cyclones, Hurricane 

Isaac and Tropical Storm Debby, are presented in a qualitative comparison.

Hurricane Isaac made landfall along the coast of southern Louisiana on August 29, 2012, 

and moved northward, where it was downgraded to a tropical storm on August 30th. Daily 

precipitation plots from each dataset on August 30th are shown in Figure B-47. The WRF depicts 

the large cyclonic rotation and enhanced precipitation bands from Isaac over southeast Louisiana 

very well, compared to the PRISM dataset. Compared to TRMM, the model does appear to overforecast the rainfall intensity for this 24-hour period.

Figure B-48 shows daily precipitation plots as Tropical Storm Debby’s outer rain bands 

begin to impact Florida’s west coast on June 25, 2012. The WRF performed very well in comparison 

to both PRISM and TRMM, forecasting the spatial extent of the large storm throughout the eastern 

Gulf of Mexico. The model did slightly under-predict the rainfall accumulations in this 24-hour 

period, compared to the observational and satellite databases.

Overall, WRF performed very well in recreating the daily precipitation events in these two 

scenarios. The daily precipitation plots from each WRF, PRISM, and TRMM dataset are available 

by request from Ramboll Environ.
Air Quality: WRF Model Performance B-57

Figure B-47. Daily Precipitation Plots from WRF, PRISM, and TRMM on August 30, 2012. 
B-58 2018 Gulf of Mexico Supplemental EIS

Figure B-48. Daily Precipitation Plots from WRF, PRISM, and TRMM Databases on June 25, 

2012. 
Air Quality: WRF Model Performance B-59

B.4 SUMMARY AND CONCLUSIONS

The BOEM Gulf of Mexico OCS Region WRF meteorological model simulation for January 

through December 2012 reproduced the observed surface and upper-air meteorological variables 

very well. The WRF performed exceptionally well in the onshore METSTAT analysis for the 36-km 

and 12-km domains and well in the onshore and offshore analysis for the 4-km domain, with a small 

bias in wind direction. This performance shows a very strong agreement overall between the model 

and surface observations.

Comparisons of selected wind roses along the Gulf Coast, which will be presented in the full 

WRF model evaluation, show WRF was able to forecast the offshore and onshore wind speed and 

wind direction very well in the 4-km domain. This suggests the model was able to accurately 

reproduce the land-sea breeze circulation.

Upper air performance in the 4-km (d03) domain for the two selected locations throughout 

the Gulf of Mexico reflects accurate predictions of the vertical atmosphere, as shown in comparisons 

between WRF and radiosonde data, especially in mixing layer heights and cases of surface-based 

temperature inversions.

The monthly precipitation analysis for the 4-km (d03) domain indicates there is a strong 

agreement between the model and observation-based precipitation measurements over land, 

including convergence zone and enhanced rainfall areas. The comparison with the 12-km (d02) 

WRF and satellite-based precipitation accumulations does indicate some understatement of 

precipitation over water, most notably in the winter months.

Based on our experience, the BOEM Gulf of Mexico OCS Region WRF modeling’s superior 

performance throughout 2012 provides a substantial basis for developing meteorological inputs for 

air quality modeling in the Gulf of Mexico region.

B.5 REFERENCES

Brashers, B. and C. Emery. 2015. The Mesoscale Model Interface Program (MMIF), Version 3.2, 

2015-07-24, Draft User’s Manual. Prepared for USEPA, Office of Air Quality Planning and 

Standards. Ramboll Environ US Corporation (Ramboll Environ). Internet website: 

http://www.epa.gov/ttn/scram/models/relat/mmif/MMIFv3.2_Users_Manual.pdf. 

Brashers, B., J. Knapik, and R. Morris. 2014. Official communication. Technical memorandum 

concerning BOEM Contract No. M14PC00007, Task 2 WRF Meteorological Model Dataset 

Assessment for the Air Quality Modeling in the Gulf of Mexico Region to Holli Ensz, Bureau of 

Ocean Energy Management, Gulf of Mexico Region. Prepared by ENVIRON International

Corporation, Lynnwood, WA.

Daly, C., M. Halbleib, J.I. Smith, W.P. Gibson, M.K. Doggett, G.H. Taylor, J. Curtis, and 

P.P. Pasteris. 2008. Physiographically sensitive mapping of climatological temperature and 
B-60 2018 Gulf of Mexico Supplemental EIS

precipitation across the conterminous United States. Int. J. Climatol. Internet website: 

http://prism.nacse.org/documents/Daly2008_PhysiographicMapping_IntJnlClim.pdf. 

Emery, C.A., E. Tai, and G. Yarwood. 2001. Enhanced Meteorological Modeling and Performance 

Evaluation for Two Texas Ozone Episodes. Prepared for the Texas Natural Resource 

Conservation Commission (now TCEQ) by ENVIRON International Corp, Novato, CA. Internet 

website: http://www.tceq.texas.gov/assets/public/implementation/air/am/contracts/reports/mm/

EnhancedMetModelingAndPerformanceEvaluation.pdf. 

Gilliam, R.C. and J.E. Pleim. 2010. Performance assessment of new land-surface and planetary 

boundary layer physics in the WRF-ARW. Journal of Applied Meteorology and Climatology 49, 

760-774.

Kemball-Cook, S., Y. Jia, C. Emery, and R. Morris. 2005. Alaska MM5 Modeling for the 2002 

Annual Period to Support Visibility Modeling. Prepared for the Western Regional Air Partnership, 

by ENVIRON International Corp., Novato, CA. Internet website: http://pah.cert.ucr.edu/

aqm/308/docs/alaska/Alaska_MM5_DraftReport_Sept05.pdf. 

McNally, D.E. 2009. 12 km MM5 Performance Goals. Presentation to the Ad-Hoc Meteorology 

Group. June 25, 2009. Internet website: http://www.epa.gov/scram001/adhoc/mcnally2009.pdf. 

NCAR. 2015. National Center for Atmospheric Research. Internet website: 

http://www2.mmm.ucar.edu/wrf/users/download/get_source.html. 

Ramboll Environ US Corp. 2015. METSTAT. Internet website: http://www.camx.com/download/

support-software.aspx. 

Saha, S., S. Moorthi, X. Wu, J. Wang, S. Nadiga, P. Tripp, D. Behringer, Y-T. Hou, H-y. Chuang, 

M. Iredell, M. Ek, J. Meng, R. Yang, M. Peña Mendez, H. van den Dool, Q. Zhang, W. Wang, 

M. Chen, and E. Becker. 2014. The NCEP Climate Forecast System Version 2. Journal of 

Climate 27, 2185-2208. doi:http://dx.doi.org/10.1175/JCLI-D-12-00823.1.

SCAS-OSU. 2001. Climate Mapping with PRISM. Oregon State University (OSU)

U.S.Dept. of Commerce, National Oceanic and Atmospheric Administration, Earth System Research 

Laboratory. 2015. NOAA/ESRL Radiosonde Database. Internet website: www.esrl.noaa.gov/

raobs. 

USDOC, NOAA, NCDC. 2014. NOAA NCDC Integrated Surface Database. Internet website: 

www.ncdc.noaa.gov/isd. 
APPENDIX C 

 

AIR QUALITY: 

EMISSIONS FOR THE CUMULATIVE AND VISIBILITY IMPACTS

Table of Contents C-iii

TABLE OF CONTENTS

Page

C.1 INTRODUCTION........................................................................................................................ C-1

C.2 DEVELOPMENT OF EMISSION INVENTORIES ..................................................................... C-4

C.2.1 Pollutants......................................................................................................................... C-5

C.2.2 Base Case Year .............................................................................................................. C-5

C.2.3 Geographical Domain...................................................................................................... C-5

C.2.4 Inventory Sources ........................................................................................................... C-6

C.2.5 Spatial Resolution ........................................................................................................... C-8

C.2.6 Temporal Resolution ....................................................................................................... C-8

C.2.7 Speciation........................................................................................................................ C-8

C.3 BASE CASE EMISSION ESTIMATES ...................................................................................... C-8

C.3.1 Point Sources .................................................................................................................. C-8

C.3.2 Nonpoint Area Sources ................................................................................................... C-9

C.3.3 Mobile Sources................................................................................................................ C-9

C.3.4 Offshore Helicopters...................................................................................................... C-10

C.3.5 Offshore Oil and Gas Production Sources—Western and Central/Eastern 

Planning Areas in the Gulf of Mexico............................................................................ C-10

C.3.6 Offshore Vessels........................................................................................................... C-13

C.3.6.1 Oil and Gas Production Support Vessels ....................................................... C-14

C.3.6.2 Non-Oil and Gas Production Offshore Vessels .............................................. C-17

C.3.7 Biogenic and Geogenic Sources................................................................................... C-19

C.3.8 Sources in Mexico......................................................................................................... C-19

C.3.9 Sources in Canada........................................................................................................ C-19

C.4 FUTURE YEAR MODELING SCENARIO EMISSION ESTIMATES....................................... C-19

C.4.1 Western, Central, and Eastern Planning Areas OCS Offshore Oil and Gas 

Production Sources....................................................................................................... C-20

C.4.1.1 Oil and Natural Gas Offshore Production Platforms....................................... C-21

C.4.1.2 Offshore Support Helicopters.......................................................................... C-22

C.4.1.3 Oil and Gas Production Offshore Support Vessels ........................................ C-22

C.4.1.4 Future Year Emission Estimates and Selection of Future Modeling Year ..... C-24

C.4.1.5 Spatial Allocation............................................................................................. C-28

C.4.2 Onshore Sources and Marine Vessels ......................................................................... C-30

C.4.3 Other Sources ............................................................................................................... C-30

C.5 SOURCE APPORTIONMENT ................................................................................................. C-31

C.6 REFERENCES......................................................................................................................... C-32

List of Tables C-v 

LIST OF TABLES

Page

Table C-1. Nonattainment and Maintenance Areas in the Southeastern U.S. ............................... C-3

Table C-2. Gulf of Mexico Air Quality Modeling Study Source Categories..................................... C-7

Table C-3. Base Case Offshore Oil and Gas Production Source Emissions Estimates for 

the GOM Western and Central/Eastern Planning Areas............................................. C-10

Table C-4. Future Year Production Platform Emission Factors.................................................... C-21

Table C-5. Summary of Vessel Characteristics. ........................................................................... C-23

Table C-6. Load Factors to be Used in the Future Year Projections............................................ C-24

Table C-7. Marine Vessel Emission Factors (g/kW-hr)................................................................. C-24

Table C-8. Emission Estimates for the Western, Central, and Eastern Planning Areas, All 

Depths, By Year and Pollutant. ................................................................................... C-25

LIST OF FIGURES

Page

Figure C-1. Location of the “Air Quality Modeling in the Gulf of Mexico Region” Study, with 

Class I Areas (purple) and Platform Locations (gray dots).......................................... C-1

Figure C-2. Ozone Nonattainment Areas in the Southeastern U.S. (USEPA, 2016a)................... C-2

Figure C-3. Overview of the “Air Quality Modeling in the Gulf of Mexico Region” Study 

Tasks. ........................................................................................................................... C-4

Figure C-4. WRF 36-km CONUS (d01), 12-km SE Regional (d02), and 4-km Gulf 

of Mexico Region (d03) Domains Along With the PGM Grids..................................... C-6

Figure C-5. 2012 Platform NOx Emissions Aggregated by Lease Block ...................................... C-11

Figure C-6. 2012 Platform VOC Emissions Aggregated by Lease Block..................................... C-12

Figure C-7. 2012 Platform PM2.5 Emissions Aggregated by Lease Block.................................... C-13

Figure C-8. 2012 Non-platform NOx Emissions ............................................................................ C-15

Figure C-9. 2012 Non-platform VOC Emissions........................................................................... C-16

Figure C-10. 2012 Non-platform PM2.5 Emissions.......................................................................... C-17

Figure C-11. Emission Estimates for all Planning Areas and Future Activities.............................. C-27

Figure C-12. Combined Annual NOx Emissions. ............................................................................ C-27

Figure C-13. Combined Annual VOC Emissions. ........................................................................... C-28

Figure C-14. Combined Annual PM2.5 Emissions. .......................................................................... C-28

Figure C-15. BOEM OCS Planning Areas and Water Depths........................................................ C-29

Air Quality: Emissions for the Cumulative and Visibility Impacts C-1 

C AIR QUALITY: EMISSIONS FOR THE CUMULATIVE AND 

VISIBILITY IMPACTS

C.1 INTRODUCTION

The U.S. Department of the Interior’s Bureau of Ocean Energy Management (BOEM) is 

required under the Outer Continental Shelf Lands Act (OCSLA) (43 U.S.C. § 1334(a)(8)) to comply 

with the National Ambient Air Quality Standards (NAAQS) to the extent that Outer Continental Shelf 

(OCS) offshore oil and gas exploration, development, and production sources do not significantly 

affect the air quality of any state. The Gulf of Mexico OCS Region’s OCS area of possible influence 

includes the States of Texas, Louisiana, Mississippi, Alabama, and Florida. BOEM’s Gulf of Mexico 

OCS Region manages the responsible development of oil, gas, and mineral resources for the 

430 million acres in the Western, Central, and Eastern Planning Areas on the OCS comprising the 

Gulf of Mexico OCS Region, including the areas under moratoria (shown in Figure C-1). The Clean 

Air Act Amendments (CAAA) of 1990 designate air quality authorities in the Gulf of Mexico OCS 

Region, giving BOEM air quality jurisdiction westward of 87°30'W. longitude and the U.S. 

Environmental Protection Agency (USEPA) air quality jurisdiction eastward of 87°30'W. longitude. In 

2006, oil and gas leasing operations within 125 miles (201 kilometers [km]) of the Florida coastline 

were banned until 2022 under the Gulf of Mexico Energy Security Act (GOMESA). The GOMESA 

moratoria area is depicted on Figure C-1. 

Figure C-1. Location of the “Air Quality Modeling in the Gulf of Mexico Region” Study, with Class I 

Areas (purple) and Platform Locations (gray dots). 
C-2 2018 Gulf of Mexico Supplemental EIS

The USEPA has set NAAQS for six regulated air quality pollutants: ozone; particulate matter 

with an aerodynamic diameter of 2.5 micrometers and smaller (PM2.5); particulate matter with an 

aerodynamic diameter of 10 micrometers and smaller (PM10); sulfur dioxide (SO2); nitrogen dioxide 

(NO2); carbon monoxide (CO); and lead (Pb). After promulgation of a NAAQS, the USEPA 

designates areas that fail to achieve the NAAQS as nonattainment areas (NAAs) and States are 

required to submit State Implementation Plans (SIPs) to the USEPA that contain emission control 

plans and a demonstration that the NAA will achieve the NAAQS by the required date. After an area 

comes into attainment of the NAAQS, the area can be redesignated as a maintenance area and 

must continue to demonstrate compliance with the NAAQS.

In 1997, the USEPA promulgated the first 8-hour ozone NAAQS with a threshold of 

0.08 parts per million (ppm) (84 parts per billion [ppb]). On March 12, 2008, the USEPA 

promulgated a more stringent 0.075 ppm (75 ppb) 8-hour ozone NAAQS. Figure C-2 presents the 

current ozone nonattainment areas in the southeastern U.S. On October 1, 2015, the USEPA 

strengthened the 8-hour NAAQS for ozone to 0.07 ppm (70 ppb). Under this more stringent ozone 

NAAQS, there may be more areas in the southeastern U.S. that will be in nonattainment. The 

USEPA plans to make attainment and nonattainment designations for the revised standards by late 

2017, with the designations based on 2014-2016 air quality data.

Figure C-2. Ozone Nonattainment Areas in the Southeastern U.S. (USEPA, 2016a). 

On December 14, 2012, the USEPA revised the PM2.5 primary NAAQS by lowering the 

annual PM2.5 NAAQS threshold from 15.0 micrograms per cubic meter (μg/m3

) to 12.0 μg/m3. The 

USEPA retained the 24-hour PM2.5 primary NAAQS at 35 μg/m3

. The 24-hour coarse PM NAAQS 

(PM10) was also retained at 150 μg/m3

. 

In February 2010, the USEPA issued a new 1-hour NO2 NAAQS with a threshold of 100 ppb 

(98th percentile daily maximum average over 3 years) and a new 1-hour SO2 NAAQS was 
Air Quality: Emissions for the Cumulative and Visibility Impacts C-3 

promulgated in June 2010 with a threshold of 75 ppb (99th percentile averaged over 3 years). The 

USEPA has not yet designated the nonattainment areas for the 1-hour NO2 and 1 hour SO2 NAAQS.

A new lead NAAQS was issued in 2008; NAAs for lead are associated with specific industrial 

sources. The NAAQS for carbon monoxide has remained essentially unchanged since it was 

originally promulgated in 1971. As of September 27, 2010, all NAAs for carbon monoxide have been 

redesignated as maintenance areas. Table C-1 summarizes the nonattainment and maintenance 

areas in the southeastern U.S.

Table C-1. Nonattainment and Maintenance Areas in the Southeastern U.S.

State Area 8-hr O3

(1997)

8-hr O3

(2008)

SO2

(2010)

Lead 

(2008)

Alabama Troy, AL NAAa

Florida

Tampa, FL NAA

Hillsborough County, FL NAA

Nassau County, FL NAA

Louisiana Baton Rouge, LA Mb NAA

St. Bernard Parish, LA NAA

Texas

Beaumont-Port Arthur, TX M

Houston-Galveston-Brazoria, 

TX NAA NAA

Frisco, TX NAA a NAA = nonattainment area

b M = maintenance area

Blank cells indicate the area is in attainment of the NAAQS.

The CAAA designated 156 Class I areas consisting of National Parks and Wilderness Areas 

that are offered special protection for air quality and air quality-related values (AQRVs). The Class I 

areas, compared to Class II areas, have lower Prevention of Significant Deterioration (PSD) air 

quality increments that new sources may not exceed and are protected against excessive increases 

in several AQRVs including visibility impairment, acid (sulfur and nitrogen) deposition, and nitrogen 

eutrophication. The Regional Haze Rule (RHR) has a goal of natural visibility conditions by 2064 at 

Class I areas, and States must submit RHR SIPs that demonstrate progress towards that goal. 

Figure C-1 displays the locations of the mandatory Class I areas (in purple) in the Gulf of Mexico 

OCS Region. In addition to Class I areas, Federal Land Management (FLM) agencies have 

designated certain other areas as sensitive Class II areas for tracking PSD increment consumption 

and AQRV impacts.

On August 26, 2014, BOEM contracted with Eastern Research Group, Inc. (ERG) and team 

members Ramboll Environ US Corporation (Ramboll Environ) and Alpine Geophysics, LLC to 

complete a comprehensive air quality modeling study in the Gulf of Mexico OCS Region. Under 

BOEM Contract Number M14PC00007, air quality photochemical grid modeling (PGM) will be 

conducted in the Gulf of Mexico OCS Region to assess the impacts to nearby States of OCS oil and 

gas exploration, development, and production as required under OCSLA. This assessment is used 
C-4 2018 Gulf of Mexico Supplemental EIS

by BOEM in the cumulative and visibility impacts analyses of the National Environmental Policy Act 

(NEPA) environmental impact statements (EISs), which are the Gulf of Mexico OCSOil and Gas 

Lease Sales: 2017-2022; Gulf of Mexico Lease Sales 249, 250, 251, 252, 253, 254, 256, 257, 259, 

and 261—Final Multisale Environmental Impact Statement (2017-2022 GOM Multisale EIS) and this 

Supplemental EIS. These analyses address both current and proposed NAAQS.

Air quality modeling requires several input datasets, including meteorology, emissions 

inventories, and ambient pollutant concentrations. Figure C-3 presents an overview of how these 

project datasets fit together for the “Air Quality Modeling in the Gulf of Mexico Region” study.

Figure C-3. Overview of the “Air Quality Modeling in the Gulf of 

Mexico Region” Study Tasks. 

C.2 DEVELOPMENT OF EMISSION INVENTORIES

A key step in performing the “Air Quality Modeling in the Gulf of Mexico Region” study in 

support of the subsequent cumulative and visibility impacts analyses is development of 

comprehensive air emission inventories that accurately depict the base case emissions within the 

study area, and emissions associated with the scenario (the future year) for the 2017-2022 GOM 

Multisale EIS and this Supplemental EIS. 

The scope of the air pollutant emissions inventory development effort for the “Air Quality 

Modeling in the Gulf of Mexico Region” study includes selection of: pollutants, base case year, 

geographical domain, sources, spatial resolution, temporal resolution, speciation, and development 

of the base case and future year emission estimates. These elements are described below.
Air Quality: Emissions for the Cumulative and Visibility Impacts C-5 

C.2.1 Pollutants

Pollutants for the “Air Quality Modeling in the Gulf of Mexico Region” study consist of criteria 

air pollutants as defined by CAA Title I: CO; lead; NOx (stated as equivalent mass of nitrogen 

dioxide [NO2]); PM2.5; PM10; and SO2, as well as volatile organic compounds (VOCs, which are 

precursors to ozone formation) and ammonia (NH3, a precursor to PM formation).

C.2.2 Base Case Year

In determining the base case year for the “Air Quality Modeling in the Gulf of Mexico Region” 

study emissions inventory, 2011 was initially selected based on data availability. Calendar year 

2011 emissions data are readily available for most sources from the USEPA National Emissions 

Inventory (NEI) (USEPA, 2015a), and BOEM’s Year 2011 Gulfwide Emissions Inventory Study

(Wilson et al., 2014), hereby called the “2011 Gulfwide Inventory.” However, 2011 was an unusually 

hot and dry year in the Gulf of Mexico OCS Region, particularly in Texas, which experienced record 

heat and dry conditions during the summer of 2011 and had a very high incidence of wildfires. 

Therefore, 2012 was selected as the base case year as more representative of “typical” conditions in 

the Gulf of Mexico OCS Region. 

C.2.3 Geographical Domain

The domain of the “Air Quality Modeling in the Gulf of Mexico Region” study emissions 

inventory is the area depicted in Figure C-4, particularly the 4-kilometer (km) domain encompassing 

the Gulf of Mexico OCS. This area, which includes parts of Alabama, Georgia, Louisiana, 

Mississippi, and Texas; all of Florida; as well as the Western, Central, and Eastern Planning Areas in 

the Gulf of Mexico and part of the Atlantic Ocean, are the main focus of the emissions inventory 

efforts. Emissions data were also required for the 36- and 12-km expanded domains depicted in 

Figure C-4, which include parts of Mexico and Canada. The outermost domain with 

36-km resolution includes the entire continental U.S. and parts of Canada and Mexico, and captures 

synoptic-scale (storm system-scale) structures in the atmosphere. The inner 12-km regional grid 

covers the southeastern U.S. and is used to ensure that large-scale meteorological patterns across 

the region are adequately represented and to provide boundary conditions to the 4-km domain.
C-6 2018 Gulf of Mexico Supplemental EIS

Figure C-4. WRF 36-km CONUS (d01), 12-km SE Regional (d02), and 4-km Gulf of Mexico Region 

(d03) Domains Along With the PGM Grids. 

C.2.4 Inventory Sources

Emissions from anthropogenic (i.e., human caused) sources, including stationary point and 

nonpoint area sources located both onshore and offshore, onroad motor vehicles, nonroad 

equipment, locomotives, marine vessels and other offshore sources, and airports, were compiled for 

the “Air Quality Modeling in the Gulf of Mexico Region” study emissions inventory. Table C-2 lists 

the source groups and categories included in the emissions inventory, along with the pollutants 

applicable to each source, and the spatial and temporal resolution. Note that emissions from nonanthropogenic sources (i.e., biogenic and geogenic sources) are also included as part of the “Air 

Quality Modeling in the Gulf of Mexico Region” study cumulative and visibility analyses.
Air Quality: Emissions for the Cumulative and Visibility Impacts C-7 

Table C-2. Gulf of Mexico Air Quality Modeling Study Source Categories. 

Group and Source Category CO NOx SO2 VOC Pb PM2.5 PM10 NH3

Spatial 

Resolutiona

NEI 

Onshore 

Sources

Point Sources         P

Nonpoint Area 

Sources         A 

Onroad Mobile 

Sources        A 

Commercial Marine 

Vessels         P, Ab

Locomotives         P, Ac

Aircraft and Airports         P

Other Nonroad Mobile 

Sources        A 

Offshore Oil & Gas Sources

Platforms in State 

Waters       P 

Platforms in Central 

and Western GOM 

OCS Planning Areas

        P 

Drilling Rigs         LB

Pipe-Laying Vessels         LB

Support Helicopters       LB

Support Vessels         LB

Survey Vessels         LB

Non-oil and Gas 

Offshore Vessels and Activities

Commercial Fishing 

Vessels         LB

Commercial Marine 

Vessels         LB

Louisiana Offshore Oil 

Port         P 

Military Vessels         LB

Recreational Vessels        LB

Vessel Lightering         P

Biogenic and Geogenic Sources

Subsurface Oil Seeps  LB

Mud Volcanoes  LB

Onshore Vegetation   A

Wildfires and 

Prescribed Burning        P 

Windblown Dust   A

Lightning  A

Sea Salt Emissions   A 

Sources in Mexico and Canada

Point Sources        P

Nonpoint Area 

Sources       A 

Mobile Sources       A 

a

 A = Area source (modeling grid cell, spatial surrogate); P = Point source (UTM coordinates, stack 

parameters); LB = Offshore lease block (modeling grid cell, spatial surrogate) 

b Larger ports and shipping will be represented as shape files; smaller ports as point sources.

c Rail yards will be represented as point sources; railway segments as area sources.
C-8 2018 Gulf of Mexico Supplemental EIS

C.2.5 Spatial Resolution

The spatial resolution of the emissions inventory is source-specific. For example, sources 

such as power plants are identified based on their geographic coordinates (i.e., latitude and 

longitude), while other sources such as nonroad mobile sources (e.g., construction equipment) are 

spatially distributed using surrogates within the county in which they are reported and that are 

typically related to the activity distribution of the category (e.g., construction sites).

The resolution of the geographical area covered by the emissions inventory is based on the 

grid cell size needed for photochemical modeling. Furthermore, the photochemical model grid 

resolution is dependent on the grid resolution of the WRF meteorological model output used.

C.2.6 Temporal Resolution

Emissions for all sources were estimated on an annual basis (i.e., emissions generated 

during 2012). For electric generating units (EGUs), emissions were allocated on a sub-annual basis 

to reflect variations in activity using data from the USEPA.

Emissions were allocated on an hourly, daily, and seasonal basis using default temporal 

allocation factors provided with the Sparse Matrix Operator Kernel Emissions (SMOKE) emissions 

model for some sources; other temporal allocations were source-specific, and profiles were 

developed and applied within the SMOKE model.

C.2.7 Speciation

When applying the PGM modeling, PM emissions were allocated to individual PM species as 

part of the SMOKE emissions processing using PM speciation factors obtained from the USEPA’s 

SPECIATE database (USEPA, 2014a) for each source category (as defined by the Source 

Classification Code). This resulted in the PM mass being broken into the mass associated with 

elemental carbon (EC), organic carbon (OC), and other elements, and particle-bound VOCs, such as 

polycyclic aromatic hydrocarbons (PAHs). The model predictions of EC will undergo further analysis 

and will be discussed in the “Air Quality Modeling in the Gulf of Mexico Region” study final report.

SMOKE was also used to convert VOC emissions into the photochemical mechanismspecific (e.g., CB05 or CB6r2h) model species used in air quality models.

C.3 BASE CASE EMISSION ESTIMATES

This section presents an overview of the methodologies used to compile the base case 2012 

emission estimates for all source categories in the emissions inventory.

C.3.1 Point Sources

Calendar year 2011 emissions data are available for onshore point sources from the USEPA 

NEI (USEPA, 2015a). In a separate modeling effort, the USEPA prepared a criteria pollutant 
Air Quality: Emissions for the Cumulative and Visibility Impacts C-9 

calendar 2012 year emissions inventory for some sectors, including onshore point sources (USEPA, 

2015b). The ERG obtained the USEPA 2012 point sources emissions inventory, conducted quality 

assurance/quality control (QA/QC) on the data, and supplemented and revised the criteria pollutant 

estimates, as needed. The USEPA prepared the 2012 point source emissions inventory as follows:

(1) 2012 data compiled by the USEPA from annual criteria pollutant reporting of 

Type A (large) sources that are submitted by responsible State and local air 

agencies;

(2) 2012 EGU emissions from the USEPA Clean Air Markets Division (CAMD) 

hourly emissions data;

(3) 2011 NEI data for other, smaller point sources that are not identified above; and

(4) 2011 airport and aircraft emission estimates developed by the USEPA updated 

to 2012 as needed.

Although the emissions data are likely complete for most point sources, ERG confirmed that 

offshore platforms within State boundaries are included in the NEI. Data from the USEPA’s 2012 

Toxics Release Inventory (TRI) for lead and ammonia were also used to supplement the inventory 

as needed (USEPA, 2015c).

C.3.2 Nonpoint Area Sources

The starting point for the 2012 nonpoint area source inventory was the data submitted by 

State and local agencies for the 2011 NEI. In addition, for completeness, the USEPA develops 

emission estimates for a number of nonpoint source categories (up to 165) for inclusion in the NEI if 

agencies do not provide estimates. The USEPA did not develop 2012 emission estimates for 

nonpoint area sources. The ERG prioritized key top-emitting source categories of NOx, PM, SO2, 

and VOCs in AL, FL, GA, LA, MS, and TX, and developed 2012 emission estimates using the 

USEPA nonpoint area source category tools (USEPA, 2014b). These categories are as follows: 

consumer products, architectural surface coatings, industrial maintenance coatings, open burning: 

municipal solid waste (MSW), residential and institutional/commercial/industrial (ICI) heating, 

upstream oil and gas, open burning, land clearing debris, paved and unpaved roads, and gasoline 

distribution Stage I. The ERG also conducted point source reconciliation for ICI heating, oil and gas, 

and gasoline distribution Stage I to verify that there are no gasoline distribution Stage II records in 

USEPA’s nonpoint file (now reported with onroad mobile sources).

C.3.3 Mobile Sources

The onroad mobile source category includes exhaust and evaporative emissions from 

onroad motor vehicles (e.g., automobiles, light-duty trucks, heavy-duty trucks) and exhaust and 

evaporative emissions from nonroad mobile sources. The ERG team ran the MOVES2014 model 

for onroad sources (USEPA, 2014c), and the USEPA ran the NONROAD model for nonroad sources 

to develop 2012 emission estimates for these categories. Locomotive emissions in the 2011 NEI 
C-10 2018 Gulf of Mexico Supplemental EIS

were not adjusted to represent 2012 activities because it was confirmed that the 2011 and 2012 fuel 

usage data from the Surface Transportation Board’s R-1 Class 1 railroad annual reporting data 

(Surface Transportation Board, 2015) show only a slight (2%) reduction in 2012 levels from 2011 

levels.

C.3.4 Offshore Helicopters

The Gulf of Mexico has more helicopter traffic than any other region of the U.S., primarily 

associated with offshore oil and gas support. Offshore support helicopter emission estimates were 

obtained from the 2011 Gulfwide inventory (Wilson et al., 2014). The estimates were supplemented 

with 2011 NEI helicopter data for onshore airports. The two datasets map out the full route between 

offshore platforms equipped with helipads and the closest onshore support facility; the NEI 

addresses emissions only at each airport and only for operations up to 3,000 feet of elevation (i.e., 

local mixing height). The two datasets were evaluated to ensure that the helicopter traffic data 

between the two are comparable and that there is no double counting of emissions.

C.3.5 Offshore Oil and Gas Production Sources—Western and Central/Eastern 

Planning Areas in the Gulf of Mexico

The starting point for offshore oil and gas production platforms in the Western and 

Central/Eastern Planning Areas (WPA and CPA/EPA) was the 2011 Gulfwide inventory. The ERG 

team supplemented the 2011 Gulfwide inventory with NH3 and Pb emission estimates for all 

applicable emission sources using USEPA emission factors. The ERG team conducted research to 

determine if the 2011 emissions values for platform sources should be adjusted to be more 

representative of 2012 emissions values. Offshore oil and gas production values for 2011 and 2012 

were obtained from the BOEM Part A Oil and Gas Operations Reports (OGOR) (USDOI, BOEM, 

2015). The OGOR data are presented at the lease level. Production of both oil and gas (including 

deepwater production) decreased from 2011 to 2012; thus, the 2011 emission estimates were 

modeled without adjustment in order to be conservative. Table C-3 presents the base case 

emission estimates for offshore oil and gas production sources in the WPA and CPA/EPA. Figures 

C-5 through C-7 show the NOx, VOC, and PM2.5 emissions from platform sources. Platform 

sources include the following emission source types: amine units, boilers/heater/burners, diesel and 

gasoline engines, drilling equipment, combustion flares, fugitives, glycol dehydrators, losses from 

flashing, mud degassing, natural gas engines, natural gas turbines, pneumatic pumps, 

pressure/level controllers, storage tanks, and cold vents.

Table C-3. Base Case Offshore Oil and Gas Production Source Emissions Estimates for the GOM 

Western and Central/Eastern Planning Areas. 

NOX

(TPY)

SO2

(TPY)

PM10

(TPY)

PM2.5

(TPY)

VOC 

(TPY)

CO 

(TPY)

Pb 

(TPY)

NH3

(TPY)

Platform 

Sources 84,128 3,197 838 835 54,724 70,339 <1 40

Non-platform 

Sources 232,765 22,977 8,632 8,225 7,937 41,880 701 70,139

Total 316,893 26,174 9,470 9,060 62,661 112,219 701 70,179
Air Quality: Emissions for the Cumulative and Visibility Impacts C-11

Figure C-5. 2012 Platform NOx Emissions Aggregated by Lease Block. (Note: This figure does not 

indicate the platform source count, location, or emissions at the time of publication of 

the 2017-2022 GOM Multisale EIS, from which this Supplemental EIS tiers.)
C-12 2018 Gulf of Mexico Supplemental EIS

Figure C-6. 2012 Platform VOC Emissions Aggregated by Lease Block. (Note: This figure does not 

indicate the platform source count, location, or emissions at the time of publication of the 

2017-2022 GOM Multisale EIS, from which this Supplemental EIS tiers.)
Air Quality: Emissions for the Cumulative and Visibility Impacts C-13

Figure C-7. 2012 Platform PM2.5 Emissions Aggregated by Lease Block. (Note: This figure does not 

indicate the platform source count, location, or emissions at the time of publication of the 

2017-2022 GOM Multisale EIS, from which this Supplemental EIS tiers.)

C.3.6 Offshore Vessels

Offshore vessels can be grouped into vessels that support the construction, operation, and 

decommissioning of oil and gas platforms; and vessels involved in other commercial, recreational, 

and military operations. All marine vessels included in this study operate using diesel engines. 

These include very large propulsion engines as well as smaller auxiliary diesel engines that provide 

power for electricity generation, winches, pumps, and other onboard equipment. Smaller engines 

tend to use distillate grade diesel fuel, while large engines are able to combust heavier residual 

blends.

40 CFR § 1043.109(b) created the North American Emission Control Area (ECA), which 

includes the Gulf of Mexico (USEPA, 2010). This regulation limits marine fuel sulfur content to 1% 

after August 1, 2012, for any vessel with a gross tonnage greater than 400. Vessels below this 

threshold tend to use distillate fuels, which are already at or below the 1% limit.
C-14 2018 Gulf of Mexico Supplemental EIS

C.3.6.1 Oil and Gas Production Support Vessels

The offshore oil and gas production sector requires a wide variety of vessels to support the 

exploration, development, and extraction of oil and gas, including the following: 

• seismic survey vessels; 

• drilling vessels; 

• pipe-laying vessels; 

• crewboats; and

• supply vessels. 

For the 2011 Gulfwide inventory, Automatic Identification System (AIS) data from PortVision 

were used to map spatial aspects of vessel movements (PortVision, 2012). The AIS is an 

automated tracking system that allows exchanges of location and contact data with other nearby 

ships, offshore platforms, satellites, and AIS base stations, enhancing navigation and reducing 

at-sea collisions.

On October 22, 2003, the U.S. harmonized the AIS mandates of the Safety of Life at Sea 

Convention with the Maritime Transportation Security Act of 2002 (MTSA), which requires the 

following vessels, including offshore support vessels, to participate in the AIS program:

(1) passenger vessels of 150 gross tonnage or more;

(2) tankers, regardless of tonnage; and

(3) vessels other than passenger vessels or tankers of 300 gross tonnage or more.

Vessels that do not meet these thresholds, such as crew boats and smaller support vessels, 

can still participate in AIS on a voluntary basis. The Offshore Marine Service Association (OMSA) is 

encouraging its membership to equip their vessels with AIS transponders, allowing for more efficient 

and safer ship movements in the highly congested central and western areas of the Gulf of Mexico.

The ERG team used the spatially distributed support vessel emission estimates from 

BOEM’s 2011 Gulfwide inventory. While the USEPA 2011 NEI also includes marine vessel emission 

estimates for the Gulf of Mexico, the emission estimates were derived from national vessel activity 

data. During QA/QC of the 2011 BOEM Gulfwide estimates, ERG found and corrected an error in 

the vessel power rating for a number of smaller vessels.

As discussed above for offshore oil and gas production platforms, the 2011 emission 

estimates for these vessels were not adjusted to reflect 2012 production levels. SOx and PM 

(associated with sulfates) were not adjusted to account for the introduction of low sulfur ECA 

compliant fuel in the last 5 months of 2012 because it was determined that most support vessels are 
Air Quality: Emissions for the Cumulative and Visibility Impacts C-15

Category 1 or 2, which already use ECA compliant fuels. Emission estimates for NH3 and Pb were 

also developed for vessels. Table C-3 presents the base case emission estimates for drilling rigs, 

pipe-laying operations, support helicopters, support vessels, and survey vessels. Figures C-8 

through C-10 show the NOx, VOC, and PM2.5 emissions from non-platform sources.

Figure C-8. 2012 Non-platform NOx Emissions. (Note: This figure does not indicate the non-platform 

source count, location, or emissions at the time of publication of the 2017-2022 GOM 

Multisale EIS, from which this Supplemental EIS tiers.)
C-16 2018 Gulf of Mexico Supplemental EIS

Figure C-9. 2012 Non-platform VOC Emissions. (Note: This figure does not indicate the 

non-platform source count, location, or emissions at the time of publication of the 

2017-2022 GOM Multisale EIS, from which this Supplemental EIS tiers.)
Air Quality: Emissions for the Cumulative and Visibility Impacts C-17

Figure C-10. 2012 Non-platform PM2.5 Emissions. (Note: This figure does not indicate the 

non-platform source count, location, or emissions at the time of publication of the 

2017-2022 GOM Multisale EIS, from which this Supplemental EIS tiers.)

The ERG team obtained drilling vessel data from BSEE to confirm that there was no drilling 

activity in the eastern Gulf of Mexico OCS region in 2012, and reviewed the permits granted by the 

USEPA for offshore platforms in the eastern Gulf of Mexico OCS region to confirm there were no 

active production platform activities in 2012.

C.3.6.2 Non-Oil and Gas Production Offshore Vessels

Vessels not directly associated with the offshore oil and gas activities include the following: 

• commercial marine vessels; 

• Louisiana Offshore Oil Port-associated vessels; 

• commercial and recreational fishing vessels; 

• ferries; 

• research vessels; 
C-18 2018 Gulf of Mexico Supplemental EIS

• harbor craft; and

• military vessels. 

Commercial marine vessels (CMVs) include large ships involved in international trade that 

visit coastal ports and operate in deep waters, as well as smaller general cargo ships and tugs that 

move barges along waterways and rivers. For the Federal waters of the central and western of the 

Gulf of Mexico, the ERG team used the commercial marine vessel data from the 2011 Gulfwide 

inventory. For completeness, for all other areas of the Gulf of Mexico, Atlantic Ocean, and State 

waters, the USEPA’s NEI data were used (which were developed from national vessel activity data 

as noted above). These inventories cover different geographical areas than the BOEM inventory, as 

well as different vessel types. BOEM’s data include large deepwater vessels as does the USEPA 

data beyond the Federal/State boundary, but they also include vessels such as ferries, dredging 

vessels, tugs, towboats, and harbor craft that tend to operate only in State waters.

The Louisiana Offshore Oil Port (LOOP) is a pumping platform for tankers to discharge 

imported crude oil to the mainland without having to maneuver through port traffic. Similarly, there 

are four offshore lightering zones in the Gulf of Mexico (i.e., Southtex, Gulfmex No. 2, Offshore 

Pascagoula No. 2, and South Sabine Point) where smaller shuttle tankers can move product from 

very large crude carriers, bringing the oil to port while the large tankers remain off the coast. 

Tankers that visit the LOOP or the lightering zones along with the shuttle tankers were identified in 

the 2011 Gulfwide inventory. The inventory also accounts for evaporative emissions from unloading 

and loading activities, and emissions from the operation of generators and pumps at the LOOP; 

adjustments were made to the 2011 LOOP emission estimates to reflect the 18% decline in crude 

imports in 2012.

Emissions from the operation of commercial and recreational fishing vessels are also 

included in the 2011 Gulfwide inventory for Federal waters. These were supplemented with the 

USEPA’s 2011 NEI data for these fishing vessels for operations in the Eastern Planning Area in the 

Gulf of Mexico, Atlantic Ocean, and State waters. For military vessels, the ERG team used the 2011 

Gulfwide inventory Navy and Coast Guard vessel emission estimates and the NEI’s Coast Guard 

emission estimates for State waters, as well as Federal waters in the eastern part of the Gulf of 

Mexico and the Atlantic Coast. The ERG team conducted research to determine that activity levels 

from 2011 to 2012 were similar for the other non-oil and gas vessels (e.g., tankers, container ships, 

bulk, and general cargo). Based on the most recent International Maritime Organization data 

(IMO, 2015), fuel combustion is projected to remain constant from 2010 to 2015. Thus, no 

adjustments were needed to approximate activities in 2012.

The SO2 and PM (associated with sulfates) emission estimates were adjusted for Category 3 

vessels to account for the introduction of low sulfur ECA-compliant fuel in the last 5 months of 2012.
Air Quality: Emissions for the Cumulative and Visibility Impacts C-19

C.3.7 Biogenic and Geogenic Sources

For completeness, it is important to include non-anthropogenic emission sources in the 

inventory. The ERG team also estimated emissions for the sources listed below.

• Onshore vegetation (biogenic): MEGAN (version 2.1) biogenic emission model

• Wildfires, prescribed burns, and agricultural burning: USEPA’s SMARTFIRE 

emissions inventory for the U.S.

• Windblown dust: Windblown dust (WBD) modeling using the WRF meteorological 

dataset

• Lightning: WRF data (preprocessor)

• Subsurface oil seeps: 2011 Gulfwide inventory

• Mud volcanoes: 2011 Gulfwide inventory

• Sea salt emissions: WRF data (preprocessor)

The ERG team used fire emission estimates from the National Center for Atmospheric 

Research (NCAR) Fire INventory (FINN) for Mexico and Canada.

C.3.8 Sources in Mexico

The ERG team developed the 2012 emission inventories for the portions of Mexico within the 

36-km modeling inventory domain using the municipality-level emission files from the 2008 Mexico 

National Emissions Inventory (MNEI) (SEMARNAT, 2014) combined with projection factors for point, 

nonpoint area, and nonroad mobile sources. Mexico onroad motor vehicle emissions were 

generated using a version of the USEPA vehicle emissions model MOVES, updated to reflect 

conditions in Mexico. MOVES2014 was the most recent version of the model available at the time of 

the analysis and reflects USEPA’s latest estimate of vehicle emissions and default U.S. activity data 

(USEPA, 2014c). The ERG also conducted research on the offshore oil production activities off the 

coast of Mexico. Based on a report published by the Congressional Research Service, it was 

determined that there was no offshore production within the 36-km modeling domain in 2012 (Seelke 

et al., 2015).

C.3.9 Sources in Canada

Emissions from the USEPA’s most recent modeling platform (2010) were used for sources in 

Canada.

C.4 FUTURE YEAR MODELING SCENARIO EMISSION ESTIMATES

Emission estimates were also needed as inputs for additional modeling scenarios that will 

predict future impacts from implementation of the 2017-2022 GOM Multisale EIS, from which this 

Supplemental EIS tiers. For modeling the future year impacts, the ERG team forecast emissions 
C-20 2018 Gulf of Mexico Supplemental EIS

estimates based on information provided by BOEM, combined with USEPA projected emission 

estimates and other data for onshore sources and marine vessels and other sources outside of the 

GOM region. The ERG team confirmed that offshore drilling in the EPA under USEPA air quality 

jurisdiction is included in BOEM’s 2017-2022 Outer Continental Shelf Oil and Gas Leasing: 

Proposed Final Program (Five-Year Program) spreadsheets. The ERG also reviewed the USEPA’s

offshore oil and gas production permits to confirm that no production platforms were permitted to be 

constructed prior to or during 2017. Projected emission estimates were developed for anticipated 

offshore drilling off the coast of Mexico.

C.4.1 Western, Central, and Eastern Planning Areas OCS Offshore Oil and Gas 

Production Sources

The ERG team developed annual emission estimates for all categories and pollutants for 

each year of activity for OCS offshore oil and gas production sources associated with the Five-Year 

Program using BOEM’s spreadsheet-based data analyses tools. BOEM provided information on the 

predicted levels of activity, sources, and locations (by planning area and water depth) to depict 

offshore oil and gas activities in the future scenario. The emissions estimates are based on a 

mid-price oil case scenario and cover the WPA, CPA, and EPA, which are under BOEM’s

jurisdiction.

After completion of the OCS offshore oil and gas production source emission estimates, the 

resulting cumulative emissions for each pollutant were assessed to determine which emission 

estimates should be selected for PGM modeling to support the cumulative and visibility impacts 

analyses.

Based on information provided by BOEM, it was assumed that emissions for the following 

sources occur during the total period of proposed activity based on the 2017-2022 GOM Multisale 

EIS scenario (2017-2056)1

, from which this Supplemental EIS tiers: 

• exploration and delineation well drilling activities (1,671 wells drilled); 

• development and production well drilling activities (1,135 wells drilled); 

• platform installation activities (535 platforms installed); 

• FPSO installation (1 FPSO installed); 

• FPSO operation (1 FPSO operating); 

• FPSO removal (1 FPSO removed); 

• pipeline installation excluding State waters (7,251 km of pipeline installed); 

 

1 Excluding the Gulf of Mexico Energy Security Act (GOMESA) moratorium area.
Air Quality: Emissions for the Cumulative and Visibility Impacts C-21

• platform oil and gas production (535 platforms in operation); 

• platform removal (535 platforms removed); 

• support helicopters (642,000 round trips); and

• support vessels (1,062,000 operations). 

The BOEM data analyses tools provide information on each of these anticipated activities by 

year, as well as water depth. The anticipated water depths by planning area were used to spatially 

allocate the emissions.

The ERG used this information to develop emission estimates for each source category 

based on emission estimation methods used in past Gulfwide emissions inventory studies and other 

data compiled for BOEM in order to determine which estimates should be selected for 

photochemical modeling to support the cumulative and visibility impacts analyses.

The following sections discuss the emission estimation methods that the ERG team used to 

estimate emissions for the BOEM oil and gas production sources in the future scenario.

C.4.1.1 Oil and Natural Gas Offshore Production Platforms

In order to develop reasonably foreseeable emission estimates for projected oil and natural 

gas production platforms, the emission factors presented in Table C-4 were developed based on the 

2011 Gulfwide inventory (Wilson et al., 2014). Because deepwater operations may significantly 

differ from conventional operations in shallower waters, are technologically more sophisticated, and 

produce at much higher rates, two sets of emission factors were developed and assigned to each 

projected platform based on water depth. Depths below 200 meters (656 feet) were assigned the 

shallow-water emission factors, and depths above were assigned deepwater emission factors.

Emission estimates for platform sources were developed based on platform installation and 

carried forward until the projected platform removal dates (provided by planning area and water 

depth).

Table C-4. Future Year Production Platform Emission Factors. 

Pollutant

Shallow Water 

Emission Factors (<200 m) 

(tons/platform/yr)

Deepwater 

Emission Factors (>200 m) 

(tons/platform/yr)

CO 56 192

NOx 46 582

PM10-PRI 0.5 5.17

PM2.5-PRI 0.50 5.15

SO2 0.51 44

VOC 22 96

Pb 2.38E-05 3.79E-03

NH3 0.0349 0.49

Source: Developed from the Year 2011 Gulfwide Emissions Inventory (Wilson et al., 2014).
C-22 2018 Gulf of Mexico Supplemental EIS

C.4.1.2 Offshore Support Helicopters

The ERG team obtained helicopter emission factors from the Switzerland Federal Office of 

Civil Aviation (FOCA) Guidance on Determination of Helicopter Emissions (FOCA, 2009). However, 

the landing and takeoff (LTO) cycle used by FOCA was determined to be too short for typical trips 

taken in the Gulf of Mexico. The time-in-mode values were therefore adjusted based on the 

International Civil Aviation Organization (ICAO) test cycles, which are considered to be appropriate 

for offshore operations in the Gulf of Mexico. Because the future fleet mix is unknown, ERG 

weighted the emission factors using fleet profile data from the Helicopter Safety Advisory 

Conference (HSAC, 2015). The VOC emission factors were developed by converting the 

hydrocarbon (HC) emission factors using data from the USEPA’s Procedures for Emission Inventory 

Preparation Volume IV: Mobile Sources (USEPA, 1992). The aggregated general aviation 

conversion factor of 1.0631 for turbine engines was used because the GOM support helicopter fleet 

is primarily equipped with turbine engines. The PM2.5 emission factors were speciated from PM10

factors using USEPA aircraft speciation data, and the SO2 emission factors were developed based 

on a typical jet fuel sulfur concentration of 0.05% (UNEP, 2012).

C.4.1.3 Oil and Gas Production Offshore Support Vessels

Four components are needed to estimate future offshore vessel emissions:

• vessel characteristics (engine power and speed); 

• engine operating load (percent of maximum engine power); 

• hours of operation (typically determined by the distance the vessel travels divided 

by the vessel speed); and

• appropriate emission factors (grams per kW-hr). 

Because there is uncertainty about the location of future activities, it was assumed that a 

typical vessel trip is 200 nautical miles, which is the round-trip distance from shore to the mid-point 

of Federal waters.

In projecting future year activity, it is not always possible to identify specific vessels that will 

be used. Therefore, the use of larger vessels that represent the upper bound of each vessel type 

was assumed, such that actual future year emissions should be similar to or lower than emission 

estimates developed using this fleet profile. These vessels were identified based on data compiled 

from the Information Handling Service (IHS) Register of Ships (IHS, 2015). Vessels from the global 

fleet were used because these larger ships move internationally based on local demand. It should 

also be noted that these larger vessels tend to be involved in deepwater activities because they are 

designed for extended open-water operations. As trends to develop deeper water locations in the 

Gulf of Mexico continue into the future, it is likely that these larger or similar vessels will support 

future year activities.
Air Quality: Emissions for the Cumulative and Visibility Impacts C-23

The selected vessels and their characteristics are presented in Table C-5. In order to 

correctly match the vessel to the appropriate emission factors, the vessel engine category is 

required. The USEPA vessel category was determined by calculating the cylinder volume based on 

the stroke length and diameter of the cylinder. The USEPA categories are defined by the following 

cylinder volumes:

• Category 1: Cylinder displacement less than 5 liters; 

• Category 2: Cylinder displacement from 5 to 30 liters; and

• Category 3: Cylinder displacement greater than 30 liters.

If a vessel’s cylinder volume was unknown, it was assumed that the vessel was powered by 

a Category 3 propulsion engine. It should also be noted that all of the selected vessels are foreign 

flagged, but it is assumed that they refuel using U.S.-regulated marine fuels as they shift equipment 

and supplies from nearby U.S. ports.

Table C-5. Summary of Vessel Characteristics. 

Vessel Type Total Main Power 

(kW) Vessel Name Propulsion Engine Category

Speed 

(knots)

Drillship 48,666 Rowan 

Renaissance 3 12

Jackup 12,485 Bob Palmer 2

(auxiliary) Not self-propelled

Platform Rig 8,100 Nabors Mods 087 2

(auxiliary) Not self-propelled

Semisubmersible 22,371 ENSCO 7500 2 3.5

Submersible 3,691 Hercules 78 2

(auxiliary) Not self-propelled

FPSO 14,1101 Terra Nova FPSO 2 12.0

FSO 51,519 Africa 3 16.5

Stimulation Vessel 15,840 Norshore Atlantic 2 14

Oil Tanker 13,369 SPT Explorer 3 15

Anchor Handling 

Vessel 27,000 KL Sandefjord 3 17

Crew Boat 11,520 R. J. Coco 

Mccall 3 23

Supply Vessel 18,000 Aleksey Chirikov 3 15

Tug Boat 19,990 Yury Topchev 3 15

Pipe-Laying Vessel 67,200 Castorone 3 14

1 Only distillate oil main engine kW included (430 kW & 2 x 6840 kW). Topside emissions are 

included in the deepwater production platform estimates. 

A vessel’s engine power varies relative to the type of operation that is implemented. While 

cruising in open waters, the propulsion engine load is typically 84% of maximum load; during 

maneuvering, it can be 60% or lower; and when stationary,. it can be 10% or lower. Table C-6
C-24 2018 Gulf of Mexico Supplemental EIS

presents the aggregated load factors that will be used in this Study for propulsion and auxiliary 

engines.

Table C-6. Load Factors to be Used in the Future Year Projections. 

Vessel Type Load Factor

Propulsion Cruising 0.8-0.85

Propulsion Idle 0.1

Propulsion Crew/Supply Boat 0.45

Propulsion Drill Ship and Semi-Submersible 0.83

Propulsion Pipe-Laying Vessel 0.16

Propulsion Tug 0.68

Auxiliary Emergency Generator 0.75

Drilling Equipment 1

The future year emission factors were developed in terms of grams of pollutant emitted per 

load-adjusted engine kW-hours based on the emission factors used in the USEPA’s 2014 NEI 

(Table C-7). The factors presented below are applicable for foreign-flagged vessels that are not 

required to comply with USEPA exhaust standards but that must comply with international Emission 

Control Area (ECA) standards. These future year factors account for the reduction in fuel sulfur level 

associated with the ECA. Because Category 2 foreign-flagged offshore support vessels will be 

refueling at U.S. ports, it was anticipated that these vessels will use low sulfur compliant U.S. fuels. 

Also, the NOx emission factors were adjusted to account for the 2016 ECA Tier III standard that 

requires high efficiency, after-treatment technology, and is applicable for U.S. and foreign-flagged 

vessels. The Category 3 PM emission factors were not adjusted to account for reductions in PM as 

sulfate compounds because the USEPA’s adjustment equation provided a PM factor lower than the 

PM emission factor for Category 2 powered vessels.

Table C-7. Marine Vessel Emission Factors (g/kW-hr). 

Engine Category NOx SO2 PM10 PM2.5 VOC CO HC NH3 Pb

2 3.4 0.006 0.320 0.310 0.141 2.48 0.13 0.005 0.00003

3 3.4 0.362 0.450 0.437 0.632 1.40 0.60 0.003 0.00003

Source: USEPA, 2016b.

C.4.1.4 Future Year Emission Estimates and Selection of Future Modeling Year

The emission estimates developed for the future BOEM oil and gas production sources were 

reviewed to determine the most suitable future year emissions to model. The PGM modeling for the 

cumulative and visibility impacts analysis was conducted based on the emissions anticipated to have 

the greatest impact on the air quality of any state. This was determined based on the estimated 

annual emission trends. The future highest NOx emission year for all activities in all planning areas 

coincided with the highest PM, CO, NH3, and Pb emissions. These emissions are driven by support 

vessel activity for the most part. The future highest VOC emission year for all activities in all

planning areas coincided with the highest SO2 emissions and is driven by production platform 

emissions. Table C-8 presents the resulting emission estimates, and Figure C-11 presents a 
Air Quality: Emissions for the Cumulative and Visibility Impacts C-25

graphical depiction of the annual emission estimates for all pollutants. Figures C-12 through C-14

present graphical depictions of the annual emission estimates for NOx, VOC, and PM2.5 by source 

category.

It was concluded that BOEM would model the activity data and resulting emission estimates 

for year 2033 for non-platform sources, and year 2036 activity data and resulting emission estimates 

for platform sources.

Table C-8. Emission Estimates for the Western, Central, and Eastern Planning Areas, All Depths, By 

Year and Pollutant.

Year NOx 

(TPY)

SO2

(TPY)

PM10

(TPY)

PM2.5

(TPY)

VOC 

(TPY)

CO 

(TPY)

Pb 

(TPY)

NH3

(TPY)

2017 3,693 40 360 349 200 2,591 0.03 10

2018 19,328 118 1,813 1,759 1,213 14,058 0.17 80

2019 34,958 158 3,199 3,104 2,150 25,462 0.30 98

2020 46,119 268 4,124 4,001 3,042 33,293 0.39 111

2021 50,126 379 4,368 4,238 3,807 35,937 0.42 125

2022 54,328 446 4,605 4,469 4,535 38,906 0.45 139

2023 57,639 527 4,888 4,743 5,311 41,426 0.48 154

2024 59,979 484 5,030 4,881 5,872 43,637 0.49 170

2025 64,527 523 5,413 5,252 6,543 47,198 0.53 189

2026 70,601 598 5,870 5,696 7,510 51,762 0.57 209

2027 76,146 704 6,305 6,118 8,419 55,747 0.61 228

2028 79,863 742 6,609 6,414 9,125 58,701 0.64 244

2029 85,277 803 7,012 6,805 10,034 62,750 0.68 262

2030 90,332 876 7,381 7,163 11,010 66,523 0.72 280

2031 97,123 984 7,860 7,628 12,185 71,365 0.77 298

2032 100,564 1,022 8,057 7,820 13,228 74,107 0.79 315

2033 108,4471 1,199 8,590 8,338 14,709 79,486 0.85 334

2034 101,673 1,193 7,919 7,687 14,939 74,742 0.79 329

2035 102,443 1,253 7,923 7,691 15,484 75,167 0.79 327

2036 103,354 1,395 7,865 7,635 15,940 75,096 0.79 318

2037 96,715 1,343 7,274 7,062 15,254 70,088 0.74 298

2038 92,539 1,327 6,935 6,732 14,560 66,732 0.71 283

2039 84,787 1,280 6,269 6,087 13,443 60,725 0.65 247

2040 79,475 1,235 5,841 5,672 12,317 56,455 0.61 226

2041 77,705 1,294 5,652 5,488 11,544 54,267 0.60 209

2042 71,710 1,292 5,110 4,962 10,485 49,266 0.55 187
C-26 2018 Gulf of Mexico Supplemental EIS

Table C-8. Emission Estimates for the Western, Central, and Eastern Planning Areas, All Depths, By 

Year and Pollutant (continued). 

Year NOx 

(TPY)

SO2

(TPY)

PM10

(TPY)

PM2.5

(TPY)

VOC 

(TPY)

CO 

(TPY)

Pb 

(TPY)

NH3

(TPY)

2043 51,254 1,094 3,390 3,293 8,643 34,736 0.38 157

2044 46,692 1,077 3,018 2,932 7,842 31,076 0.35 143

2045 42,933 1,009 2,752 2,673 7,115 28,358 0.32 128

2046 39,227 974 2,433 2,364 6,492 25,503 0.29 117

2047 37,540 965 2,313 2,247 6,006 24,050 0.28 108

2048 34,738 954 2,083 2,024 5,495 21,808 0.26 98

2049 32,995 904 1,995 1,939 5,020 20,615 0.25 90

2050 28,873 849 1,688 1,640 4,403 17,665 0.22 82

2051 26,286 796 1,524 1,481 3,872 15,834 0.20 73

2052 24,303 747 1,406 1,367 3,475 14,510 0.18 67

2053 15,585 598 757 737 2,610 8,716 0.11 23

2054 13,131 592 542 527 2,333 6,838 0.09 17

2055 12,062 502 548 533 2,010 6,479 0.09 16

2056 10,119 453 434 422 1,615 5,185 0.07 12

2057 9,083 450 340 331 1,528 4,407 0.06 9

2058 8,519 405 344 335 1,321 4,185 0.06 8

2059 7,182 316 321 313 1,031 3,653 0.05 7

2060 6,052 314 215 209 984 2,829 0.04 5

2061 5,765 270 237 231 877 2,852 0.04 5

2062 5,075 268 180 176 760 2,305 0.04 4

2063 4,614 224 186 181 646 2,201 0.03 3

2064 3,524 136 183 178 433 1,872 0.03 2

2065 1,906 46 130 126 175 1,157 0.02 1

2066 1,392 46 81 79 153 782 0.01 1

1 Bold numbers are the highest emissions per year per pollutant. These were the amounts modeled.
Air Quality: Emissions for the Cumulative and Visibility Impacts C-27

Figure C-11. Emission Estimates for all Planning Areas and Future Activities. 

Figure C-12. Combined Annual NOx Emissions. 
C-28 2018 Gulf of Mexico Supplemental EIS

Figure C-13. Combined Annual VOC Emissions. 

Figure C-14. Combined Annual PM2.5 Emissions. 

C.4.1.5 Spatial Allocation

The estimated emissions were allocated by planning area (WPA vs. CPA/EPA) and water 

depth (i.e., 0-60 m, 60-200 m, 200-800 m, 800-1,600 m, 1,600-2,400 m, and >2,400 m). 

Figure C-15 depicts the planning area boundaries and water depth contours. (Note that the 

GOMESA Congressional Moratoria Area is not indicated in Figure C-15.) Emissions were not 

allocated to the GOMESA. The emission estimates were allocated spatially based on the 

anticipated future year activities provided by BOEM. Because helicopters, support vessels, and 
Air Quality: Emissions for the Cumulative and Visibility Impacts C-29

tankers transit multiple water depths, their emissions were allocated across multiple water depth 

contours based on assumed installed platform locations.

For some sources, emissions were assigned to unleased blocks in each area (i.e., WPA and 

CPA/EPA) relative to the water depth where the activity is anticipated to occur. These categories 

include the following: 

• exploratory drilling vessels; 

• development/production drilling vessels; and

• production platforms. 

Figure C-15. BOEM OCS Planning Areas and Water Depths. 

Production platforms were located as point sources with randomly selected locations. Using 

GIS, each lease block in the Gulf of Mexico was assigned to a water depth bin. Blocks with an 

active lease and that have contained a platform were then removed. Blocks that have had a 

platform suggest that they were leased at some point in time, and therefore are less desirable for 

future exploration. Once the inactive blocks with no history of production were identified, random 

blocks were selected throughout each water depth for each future platform as depicted in 

Figure C-15. Each platform was placed in a separate block at the centroid. Pipe-laying vessel 
C-30 2018 Gulf of Mexico Supplemental EIS

activities were assigned to leased and unleased blocks as their operations were not limited to just 

the unleased blocks.

Emissions associated with BOEM’s existing OCS oil and gas production sources were held 

constant at 2012 levels.

C.4.2 Onshore Sources and Marine Vessels

In support of the proposed ozone NAAQS revisions, the USEPA released the 2011 air quality 

modeling platform (2011v6.1), with projections to 2018 and 2025, for point, nonpoint area, and 

mobile sources in the United States (USEPA, 2014d). In addition, the USEPA released the 2011 air 

quality modeling platform (2011v6.2), with projections to 2017, to support ozone transport modeling 

for the 2008 NAAQS as well as the 2015 ozone NAAQS (USEPA, 2015d). In early October, 2015, 

the USEPA also released the 2011v6.2 calendar year 2025 projected inventory (USEPA, 2015d). 

The ERG team used the 2011v6.2 platform for calendar year 2017, primarily because the platform is 

based on the most recent version of the NEI (2011v.2). Calendar year 2017 data were selected 

rather than 2025 data because there is less uncertainty associated with the 2017 estimated 

emissions because most of the controls factored in by the USEPA are already “on the books” and 

not speculative. The Technical Support Document (TSD) Preparation of Emissions Inventories for 

the Version 6.2, 2011 Emissions Modeling Platform (USEPA, 2015d) provides details on the 

development of the 2011v6.2 future year modeling platforms.

C.4.3 Other Sources

For sources in Mexico, the USEPA air quality modeling platform 2011v6.2 includes projected 

2018 emissions for onshore sources. The USEPA held emissions constant for sources in Canada.

For completeness, projected emissions estimates were also developed for platforms off the 

coast of Mexico; the ERG team researched the impacts of the restructuring of the energy sector in 

Mexico, which is predicted to include deepwater drilling within the modeling domain. Emissions 

were estimated based on projected deepwater production (PEMEX, 2012) and using productionbased emission factors developed from the 2011 Gulfwide Inventory (Wilson et al., 2014).

For the LOOP and vessel lightering, emissions were held at 2012 levels because of 

uncertainties in future crude oil imports, which involve the very large crude carriers that visit the 

LOOP and lightering zones. The ERG team also investigated the need to include a liquefied natural 

gas (LNG) port to be located in Federal waters and originally expected to be operational in 2019. On 

September 18, 2015, however, the Maritime Administration (MARAD) and the U.S. Coast Guard 

stopped the permit application process, as Delphin LNG, LLC is amending the application. This 

potential source was not included in the future scenario given this uncertainty.
Air Quality: Emissions for the Cumulative and Visibility Impacts C-31

C.5 SOURCE APPORTIONMENT

Source apportionment, as applied in PGM modeling, provides a means of assessing the 

contributions of specified sources or source groups to predicted ozone and PM concentrations under 

the air quality conditions being simulated. Source contributions can be calculated for ozone and for 

PM using ozone or PM source apportionment routines included in the CAMx PGM modeling. In this 

Study, the primary receptor locations of interest for examining source contributions lie both along the 

shoreline and the State seaward boundary, although the PGM source apportionment output is for the 

entire modeling domain. Source apportionment analyses with the PGM will be applied to the future 

year scenario in order to analyze the pre- and postlease OCS oil and gas impacts to short-term and 

annual NAAQS. This will afford BOEM the opportunity to discern which source groups have the 

largest impacts and potentially need to be examined for control strategies. BOEM selected the 

following source groups for source apportionment:

• fires (U.S., Canada, and Mexico); 

• biogenic and other natural sources (e.g., lighting NOx and sea salt); 

• additional BOEM OCS oil and gas production platforms associated with the FiveYear Program; 

• additional BOEM oil and gas production support vessels and helicopters 

associated with the Five-Year Program; 

• BOEM OCS oil and gas production platforms, support vessels, and helicopters 

under No Action (base case) alternative; 

• all other marine vessel activity in the Gulf of Mexico; 

• other anthropogenic U.S. sources; 

• Mexican and Canadian anthropogenic sources; and

• initial and boundary conditions (IC and BC). 

These source groups aggregate similar sources based on jurisdiction (i.e., sources under 

BOEM control versus other Federal agencies) and sources beyond control (e.g., natural emission 

sources and foreign sources). This is helpful in showing whether BOEM’s sources are significantly 

contributing to any modeled air quality issues onshore and at the State seaward boundary, or if a 

source category regulated by another Federal agency is the more likely the problem source.

Having the additional OCS oil and gas production platforms, support vessels, and helicopters 

associated with the scenarios for the 2017-2022 GOM Multisale EIS and this Supplemental EIS as 

separate source groups allows BOEM to quantify the impact of these sources on the onshore air 

quality and at the State seaward boundary.
C-32 2018 Gulf of Mexico Supplemental EIS

C.6 REFERENCES

Helicopter Safety Advisory Conference (HSAC). 2015. 2014 Gulf of Mexico Offshore Helicopter 

Operations and Safety Review. HSAC Helicopter Safety Advisory Committee. Internet website: 

http://www.hsac.org. 

Information Handling Service (IHS). 2015. IHS Vessel Database. Internet website: 

http://www.ihs.com. 

International Maritime Organization (IMO). 2015. Third IMO Greenhouse Gas Study 2014. Internet 

website: http://www.imo.org/en/OurWork/Environment/PollutionPrevention/AirPollution/

Documents/Third%20Greenhouse%20Gas%20Study/GHG3%20Executive%20Summary%20

and%20Report.pdf. 

Petróleos Mexicanos (PEMEX). 2012. Investor Presentation. April 2012. Internet website: 

http://www.pemex.com/ri/Publicaciones/Presentaciones%20Archivos/201205_p_inv_e_120508_

LA.pdf. 

PortVision. 2012. AIS 2011 data provided to the U.S. Bureau of Ocean Energy.

Seelke, C.R., M. Ratner, M.A. Villarreal, P. Brown. 2015. Mexico’s Oil and Gas Sector: 

Background, Reform Efforts, and Implications for the United States. Congressional Research 

Service. 7-5700. Internet website: https://www.fas.org/sgp/crs/row/R43313.pdf. 

SEMARNAT. 2014. Inventario Nacional de Emisiones de México, 2008. Secretaría del Medio 

Ambiente y Recursos Naturales (Secretariat of the Environment and Natural Resources). 

Detailed municipality-level emission files provided by David Alejandro Parra Romero. 

January 31.

Surface Transportation Board. 2015. R-1 Class 1 Railroad Annual Reporting Data. Internet 

website: http://www.stb.dot.gov/econdata.nsf/f039526076cc0f8e8525660b006870c9?

OpenView. 

Switzerland Federal Office of Civil Aviation (FOCA). 2009. Guidance on Determination of Helicopter 

Emissions. March 2009 Reference: 0/3/33/33-05-20.

United Nations Environment Programme (UNEP). 2012. Intergovernmental Panel on Climate 

Change, Chapter 7. Aircraft Technology and Its Relation to Emissions. Internet website: 

http://www.grida.no/publications/other/ipcc_sr/?src=/climate/ipcc/aviation/111.htm. 

U.S. Dept of the Interior. Bureau of Ocean Energy Management. 2015. Oil and Gas Operations 

Reports – Part A (OGOR-A) Well Production (1996-2015). Internet website: 

https://www.data.boem.gov/homepg/pubinfo/freeasci/product/freeprod_ogora.asp. 

U.S. Environmental Protection Agency (USEPA). 1992. Procedures for Emission Inventory 

Preparation, Volume IV: Mobile Sources. EPA 420-R-92-009. Internet website: 

http://www3.epa.gov/otaq/models/nonrdmdl/r92009.pdf. 
Air Quality: Emissions for the Cumulative and Visibility Impacts C-33

U.S. Environmental Protection Agency (USEPA). 2010. Designation of North American Emission. 

Control Area to Reduce Emissions from Ships. U.S. Environmental Protection Agency, Office of 

Transportation and Air Quality. EPA-420-F-10-015. Internet website: http://www.epa.gov/

otaq/regs/nonroad/marine/ci/420f10015.pdf. 

U.S. Environmental Protection Agency (USEPA). 2014a. SPECIATE Version 4.4. U.S. 

Environmental Protection Agency, Office of Air Quality Planning and Standards. Internet 

website: http://www.epa.gov/ttn/chief/software/speciate/index.html. 

U.S. Environmental Protection Agency (USEPA). 2014b. 2011 NEI Nonpoint Emission Estimation 

Tools and Methods. U.S. Environmental Protection Agency, Office of Air Quality Planning and 

Standards. Internet website: http://www.epa.gov/ttn/chief/net/2011inventory.html#inventorydoc. 

U.S. Environmental Protection Agency (USEPA). 2014c. MOVES2014. U.S. Environmental 

Protection Agency. Internet website: http://pubweb.epa.gov/otaq/models/moves/. 

U.S. Environmental Protection Agency (USEPA). 2014d. Ozone NAAQS Emissions Modeling 

Platform (2011 v6.1). 2011, 2018, and 2025 Emissions Modeling Platform Technical Support 

Document. Internet website: http://www3.epa.gov/ttn/chief/emch/index.html. 

U.S. Environmental Protection Agency (USEPA). 2015a. 2011 National Emissions Inventory (NEI), 

Version 2. U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, 

Air Quality Assessment Division, Emission Inventory and Analysis Group, Research Triangle 

Park, NC. Internet website: http://www.epa.gov/ttn/chief/eiinformation.html. 

U.S. Environmental Protection Agency (USEPA). 2015b. 2012 National Emissions Inventory (NEI). 

Provided by the U.S. Environmental Protection Agency, Office of Air Quality Planning and 

Standards, Air Quality Assessment Division, Emission Inventory and Analysis Group, Research 

Triangle Park, NC. Internet website: http://www.epa.gov/ttn/chief/eiinformation.html. 

U.S. Environmental Protection Agency (USEPA). 2015c. Toxics Release Inventory (TRI) Program. 

U.S. Environmental Protection Agency, Office of Environmental Information, Washington, DC. 

Internet website: http://www2.epa.gov/toxics-release-inventory-tri-program. 

U.S. Environmental Protection Agency (USEPA). 2015d. Technical Support Document (TSD) 

Preparation of Emissions Inventories for the Version 6.2, 2011 Emissions Modeling Platform. 

Internet website: https://www.epa.gov/air-emissions-modeling/2011-version-62-platform. 

U.S. Environmental Protection Agency (USEPA). 2016a. Green Book Nonattainment Areas, 8 Hour 

Ozone Nonattainment Areas (2008 Standard). Internet website: https://www3.epa.gov/

airquality/greenbook/map8hr_2008.html. 

U.S. Environmental Protection Agency (USEPA). 2016b. 2014 National Emissions Inventory (NEI) 

Documentation. U.S. Environmental Protection Agency, Office of Air Quality Planning and 

Standards, Research Triangle Park, NC. Internet website: https://www.epa.gov/air-emissionsinventories/2014-national-emissions-inventory-nei-documentation. 
C-34 2018 Gulf of Mexico Supplemental EIS

Wilson, D., R. Billings, R. Chang, H. Perez, and J. Sellers. 2014. Year 2011 Gulfwide Emissions 

Inventory Study. U.S. Department of the Interior, Bureau of Ocean Energy Management, Gulf of 

Mexico OCS Region, New Orleans, LA. OCS Study BOEM 2014-666. 182 pp.
APPENDIX D 

 

AIR QUALITY: 

CUMULATIVE AND VISIBILITY IMPACTS

Table of Contents D-iii

TABLE OF CONTENTS

Page

D.1 Introduction.............................................................................................................................. D-1

D.1.1 Background on Air Quality Impact Analyses and Thresholds.................................... D-2

D.1.1.1 Ambient Air Quality Standards.................................................................... D-3

D.1.1.2 Air Quality-Related Values.......................................................................... D-5

D.1.2 Overview of Approach ................................................................................................ D-6

D.2 Meteorology............................................................................................................................. D-7

D.3 Emissions ................................................................................................................................ D-9

D.3.1 Pollutants .................................................................................................................... D-9

D.3.2 Base Year................................................................................................................... D-9

D.3.3 Geographical Domain............................................................................................... D-10

D.3.4 Inventory Sources..................................................................................................... D-10

D.3.5 Spatial Resolution..................................................................................................... D-11

D.3.6 Temporal Resolution ................................................................................................ D-12

D.3.7 Speciation................................................................................................................. D-12

D.3.8 Base Year and Future Year Emission Estimates..................................................... D-12

D.3.9 Emissions Processing for Preparation of Model-Ready Emissions......................... D-12

D.3.9.1 Smoke Processing.................................................................................... D-12

D.3.9.2 Biogenic Emissions................................................................................... D-14

D.3.9.3 Fire Emissions........................................................................................... D-14

D.3.9.4 Sea Salt and Halogen Emissions ............................................................. D-16

D.3.9.5 Lightning NOx Emissions .......................................................................... D-16

D.3.9.6 Windblown Dust ........................................................................................ D-17

D.3.9.7 QA/QC of Processed Emissions............................................................... D-17

D.3.9.8 Development of Model-Ready Emissions................................................. D-17

D.3.9.9 Summary of Processed Emissions........................................................... D-18

D.3.10 Source Apportionment Design ................................................................................. D-34

D.4 Base Case Photochemical Grid Modeling............................................................................. D-35

D.4.1 Overview................................................................................................................... D-35

D.4.2 Model Grid Configuration.......................................................................................... D-36

D.4.3 Meteorology.............................................................................................................. D-38

D.4.4 Configuration of Model Input Parameters ................................................................ D-39

D.5 Model Performance Evaluation ............................................................................................. D-42

D.5.1 Implications of WRF Model Performance on PGM Simulations .............................. D-42

D.5.2 Ambient Data Used In the Model Performance Evaluation ..................................... D-42

D.5.3 Model Performance Statistics................................................................................... D-46

D.5.4 Approach .................................................................................................................. D-48
D-iv 2018 Gulf of Mexico Supplemental EIS

D.5.5 Initial Model Performance Results............................................................................ D-50

D.5.6 Final Model Performance Results ............................................................................ D-50

D.5.6.1 Ozone........................................................................................................ D-51

D.5.6.2 Particulate Matter...................................................................................... D-58

D.6 Air Resource Assessment Approach .................................................................................... D-70

D.6.1 Future Year Modeling............................................................................................... D-70

D.6.1.1 Source Apportionment Design.................................................................. D-70

D.6.1.2 Future Year Source Apportionment Simulation........................................ D-71

D.6.2 Post-Processing of Future Year Source Apportionment Modeling Results............. D-72

D.6.2.1 Overview ................................................................................................... D-72

D.6.2.2 Comparison against NAAQS .................................................................... D-73

D.6.2.3 Impacts at Class I and Sensitive Class II Areas....................................... D-74

D.6.2.4 PSD Increments........................................................................................ D-81

D.7 Air Resource Assessment Results........................................................................................ D-81

D.7.1 NAAQS Impacts........................................................................................................ D-81

D.7.1.1 Ozone NAAQS Analysis using Relative Model Results ........................... D-81

D.7.1.2 Ozone NAAQS Analysis Using Absolute Modeling Results..................... D-90

D.7.1.3 PM2.5 NAAQS Analysis using Relative Model Results ........................... D-93

D.7.1.4 PM2.5 NAAQS Analysis using Absolute Model Predictions................... D-100

D.7.1.5 NAAQS Analysis for other Criteria Air Pollutants ................................... D-107

D.7.2 PSD Increments...................................................................................................... D-121

D.7.3 AQRV Impacts........................................................................................................ D-123

D.7.3.1 Visibility ................................................................................................... D-123

D.7.3.2 Acid Deposition ....................................................................................... D-135

D.8 References .......................................................................................................................... D-138
List of Tables D-v 

LIST OF TABLES

Page

Table D-1. Nonattainment and Maintenance Areas in the Southeastern U.S.............................. D-5

Table D-2. Gulf of Mexico OCS Region Air Quality Modeling Study Source Categories........... D-10

Table D-3. 2012 Fire Criteria Air Pollutant Emissions Summary by Fire Type for BOEM’s 

36-, 12-, and 4-km Domains. .................................................................................... D-15

Table D-4. 2012 Base Case and Future Year Emissions Summary by State for BOEM’S 

12-km Domain (only Gulf Coast States: Alabama, Florida, Louisiana, 

Mississippi, and Texas)............................................................................................. D-19

Table D-5. 2012 Base Case and Future Year Emissions Summary by Source Category for 

BOEM’s 4-km Domain............................................................................................... D-27

Table D-6. Changes in Emissions between the 2012 Base Case and Future Year 

Emissions (short tons per year) by Source Category for BOEM’s 4-km Domain..... D-28

Table D-7. Source Categories for Source Apportionment Calculations..................................... D-35

Table D-8. Domain Grid Definitions for the WRF and CAMx/CMAQ Modeling.......................... D-36

Table D-9. Vertical Layer Interface Definition for WRF Simulations (left-most columns) 

and the Layer-collapsing Scheme for the CAMx/CMAQ Layers (right columns). .... D-37

Table D-10. CAMx Model Configuration....................................................................................... D-41

Table D-11. Definitions of Model Performance Evaluation Statistical Metrics. ............................ D-46

Table D-12. Ozone and PM Model Performance Goals and Criteria........................................... D-47

Table D-13. Model Performance Statistics at Different Observed Ozone Concentration 

Screening Thresholds Based on All Monitoring Sites in the 4-km Domain 

(shaded cells indicate values exceeding USEPA performance goals)..................... D-56

Table D-14. NAAQS and PSD Increments. .................................................................................. D-72

Table D-15. Source Group for Incremental Impacts Analysis. ..................................................... D-73

Table D-16. Class I and Sensitive Class II Areas in Gulf Coast and Nearby States.................... D-75

Table D-17. Current Year (DVC) and Future Year (DVF) Ozone Design Values at Ambient 

Air Monitoring Sites within the 4-km Modeling Domain from MATS......................... D-83

Table D-18. Ozone Current (DVC) and Future Year (DVF) Design Values and Reduction in

DVF with Contributions from Individual Source Groups Removed. ......................... D-85

Table D-19. MATS Ozone Design Value Results for All Monitoring Sites Where Exclusion 

of Contributions from Source Group A or B is Sufficient to Reduce the 

Predicted Future Design Value (DVF) from Above the NAAQS to Below the 

NAAQS (all values in ppb). ....................................................................................... D-87

Table D-20. Current Year (DVC) and Future Year (DVF) 24-Hour PM2.5 Design Values for 

Monitoring Sites in the 4-km Modeling Domain from MATS..................................... D-94

Table D-21. 24-Hour PM2.5 Current (DVC) and Future Year (DVF) Design Values and 

Reduction in DVF with Contributions from Individual Source Groups Removed. .... D-95

Table D-22. Current (DVC) and Projected Future (DVF) Annual Average PM2.5 Design 

Values for Monitoring Sites in the 4-km Modeling Domain (highlighted values 

exceed the 12 μg/m3 NAAQS). ................................................................................. D-96
D-vi 2018 Gulf of Mexico Supplemental EIS

Table D-23. Annual Average PM2.5 Future Year Design Values (DVF) and Change in DVF 

with Contributions from Individual Source Groups Removed (highlighted 

values exceed the 12 μg/m3 NAAQS)....................................................................... D-97

Table D-24. Maximum Source Group Contributions for PSD Pollutants at Class I and 

Sensitive Class II Areas in the 4-km Modeling Domain.......................................... D-122

Table D-25. Source Group Contributions for PSD Pollutants at All Class I and Sensitive 

Class II Areas in the 4-km Modeling Domain. ........................................................ D-124

Table D-26. Incremental Visibility Impacts Relative to Natural Background Conditions from 

Source Group A. ..................................................................................................... D-125

Table D-27. Incremental Visibility Impacts Relative to Natural Background Conditions from 

Source Group B. ..................................................................................................... D-126

Table D-28. Cumulative Visibility Results for 20% Worst Visibility Days (W20%) at Class I 

Areas for Base (2012) Year (BY) and Future Year (FY) Scenarios with All 

Sources Included and with Contributions from Each Source Group Removed. .... D-129

Table D-29. Differences in Cumulative Visibility Results for 20% Worst Visibility Days 

(W20%) at Class I Areas Between the Future Year (FY) and Base Year (BY) 

Scenarios and Contributions of Each Source Group to the Future Year 

Scenario Visibility.................................................................................................... D-131

Table D-30. Cumulative Visibility Results for 20% Best Visibility Days (B20%) at Class I 

Areas for Base (2012) Year (BY) and Future Year (FY) Scenarios with All 

Sources Included and with Contributions from Each Source Group Removed. .... D-133

Table D-31. Differences in Cumulative Visibility Results for 20% Best Visibility Days 

(B20%) at Class I Areas Between the Future Year (FY) and Base Year (BY) 

Scenarios and Contributions of Each Source Group to the Future Year 

Scenario Visibility.................................................................................................... D-134

Table D-32. Deposition Analysis Threshold Values (kg/ha/yr) as Defined in the Federal 

Land Manager Guidance (FLAG, 2010). ................................................................ D-136

Table D-33. Incremental Deposition Impacts from Source Groups A and B at Class I and 

Sensitive Class II Areas in the 4-km Domain. ........................................................ D-136

Table D-34. Cumulative Nitrogen (N) and Sulfur (S) Deposition Impacts (kg/ha/yr) under 

the Base and Future Year Scenarios (shading indicates values exceeding the 

Critical Load threshold). .......................................................................................... D-137
List of Figures D-vii

LIST OF FIGURES

Page

Figure D-1. Location of the “Air Quality Modeling in the Gulf of Mexico Region” Study, with 

Class I Areas (purple). ................................................................................................ D-1

Figure D-2. Ozone Nonattainment Areas in the Southeastern U.S............................................... D-4

Figure D-3. Class I and Sensitive Class II Areas in the Study Region.......................................... D-6

Figure D-4. Overview of the “Air Quality Modeling in the Gulf of Mexico Region” Study 

Tasks (note that the meteorological model takes meteorological observations 

as inputs)..................................................................................................................... D-7

Figure D-5. Meteorological (WRF model) and PGM Modeling Domains Including the 36-km 

Horizontal Grid Resolution CONUS WRF Domain (outer box), 12-km 

Resolution Southeast Regional WRF (white) and PGM (blue) Domains (d02), 

and 4-km Resolution Gulf of Mexico OCS Region WRF (black) and PGM 

(blue) Domains (d03). ................................................................................................. D-8

Figure D-6. BOEM’s 12-km 2012 Base Case NOx Emissions Summary in Tons per Year 

by Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ...................................................................................................................... D-20

Figure D-7. BOEM 12-km 2012 Base Case VOC Emissions Summary in Tons per Year by 

Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ...................................................................................................................... D-21

Figure D-8. BOEM 12-km 2012 Base Case PM2.5 Emissions Summary in Tons per Year by 

Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ...................................................................................................................... D-22

Figure D-9. BOEM 12-km 2012 Base Case SO2 Emissions Summary in Tons per Year by 

Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ...................................................................................................................... D-23

Figure D-10. BOEM 12-km Future Year NOx Emissions Summary in Tons per Year by 

Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ...................................................................................................................... D-24

Figure D-11. BOEM 12-km Future Year VOC Emissions Summary in Tons per Year by 

Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ...................................................................................................................... D-25

Figure D-12. BOEM 12-km Future Year PM2.5 Emissions Summary in Tons per Year by 

Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ...................................................................................................................... D-26

Figure D-13. BOEM 12-km Future Year SO2 Emissions Summary in Tons per Year by 

Source Category and State (Alabama, Florida, Louisiana, Mississippi, and 

Texas). ...................................................................................................................... D-27

Figure D-14. Spatial Distribution of (clockwise starting from top left) NOx, VOC, SO2, and 

PM2.5 Emissions (tons per year) from New OCS Oil and Gas Production 

Platforms under the Proposed Action....................................................................... D-30
D-viii 2018 Gulf of Mexico Supplemental EIS

Figure D-15. Spatial Distribution of Emissions (tons per year) of (clockwise starting from top 

left) NOx, VOC, SO2, and PM2.5 from BOEM’s OCS Additional Oil and Gas 

Support Vessels and Helicopters under the Proposed Action Scenario.................. D-31

Figure D-16. Spatial Distribution of (clockwise starting from top left) NOx, VOC, SO2, and 

PM2.5 Emissions (tons per year) from BOEM’s OCS Oil and Gas Platforms, 

Support Vessels, and Helicopters under the No Action Alternative in BOEM’s 

4-km Domain............................................................................................................. D-32

Figure D-17. Spatial Distribution of (clockwise starting from top left) NOx, VOC, SO2, and 

PM2.5 Emissions (tons per year) from All Other Marine Vessel Activity in the 

Gulf of Mexico under the Future Year Scenario in BOEM’s 4-km Domain. ............. D-33

Figure D-18. Spatial Distribution of (clockwise starting from top left) NOx, VOC, SO2, and 

PM2.5 Emissions (tons per year) from Other Anthropogenic U.S. Sources for 

the Future Year Scenario within BOEM’s 4-km Domain. ......................................... D-34

Figure D-19. Ozone Monitoring Sites Used in the Model Performance Evaluation: CASTNet 

Sites in the Southeastern U.S. (top) and AQS Sites within the 4-km Modeling 

Domain (bottom) (color coding of AQS monitor locations is arbitrary)..................... D-43

Figure D-20. Speciated PM Monitoring Sites Used in the Model Performance Evaluation: 

CSN Network (top), IMPROVE Network (bottom left), and SEARCH Network 

(bottom right)............................................................................................................. D-45

Figure D-21. Monthly Normalized Mean Bias and Normalized Mean Error for Daily 

Maximum 8-hour Average Ozone at AQS (left) and CASTNet (right) Monitoring 

Sites Located within the 4-km Modeling Domain (top) and the 12-km Domain 

(bottom)..................................................................................................................... D-51

Figure D-22. Fraction of Site-days during Each Month of 2012 with Observed Daily 

Maximum 8-hour Ozone Exceeding 60 (top), 65 (middle), or 70 (bottom) ppb 

Over All Monitoring Sites in the 4-km Domain.......................................................... D-52

Figure D-23. Observed (blue) and Predicted (red) Monthly Mean Daily Maximum 8-hour 

Average Ozone Over All Sites in the 4-km Modeling Domain.................................. D-53

Figure D-24. Scatter (left) and Scatter Density (right) Plots for Observed vs. Predicted Daily 

Maximum 8-hour Ozone in Q2 (top) and Q3 (bottom) for All AQS Monitoring 

Sites in the 4-km Modeling Domain.......................................................................... D-54

Figure D-25. Normalized Mean Bias (NMB) for Daily Maximum 8-hour Ozone for Q2 (top) 

and Q3 (bottom)........................................................................................................ D-55

Figure D-26. Time Series of Daily Maximum 8-hour Ozone at Monitoring Sites with Highest 

Design Values in Harris (top), Brazoria (middle), and Galveston (bottom) 

Counties, Texas, for Q2 (left) and Q3 (right). ........................................................... D-57

Figure D-27. Time Series of Daily Maximum 8-hour Ozone at Monitoring Sites in the Baton 

Rouge Nonattainment Area: LSU (top) and Carville (bottom) for Q2 (left) and 

Q3 (right). .................................................................................................................. D-57

Figure D-28. Time Series of Daily Maximum 8-hour Ozone at the ALC188 (AlabamaCoushatta, Texas) CASTNet Monitoring Site for Q2 (top) and Q3 (bottom)............ D-58

Figure D-29. PM Monitoring Sites in the Southeastern U.S. Domain (triangles – AQS hourly, 

square – IMPROVE, diamond – CSN, circles – AQS FRM daily). ........................... D-60
List of Figures D-ix

Figure D-30. Soccer Plots of Total PM2.5 Mass Model Performance Across the IMPROVE 

(top left), CSN (top right), SEARCH (bottom left), and FRM Daily (bottom right) 

Monitoring Networks for Sites in the Southeastern U.S. Domain............................. D-61

Figure D-31. Comparisons of Predicted with Observed Daily Average PM at CSN Network 

Sites in the Southeastern U.S. for Q2 (left) and Q4 (right) for Total PM2.5 (top), 

Other PM2.5 (middle), and Sodium (bottom). ............................................................ D-62

Figure D-32. Comparisons of Observed vs. Predicted OC (top) and EC (bottom) at 

SEARCH (left) and CSN (right) Network Sites in the Southeastern U.S.................. D-63

Figure D-33. Monthly Normalized Mean Bias and Normalized Mean Error for Hourly NO2

(top) and Daily NOy (bottom) at SEARCH Network Sites (left) and AQS Sites 

(right) in the 4-km Domain. ....................................................................................... D-64

Figure D-34. Monthly Normalized Mean Bias and Normalized Mean Error for NO3 at 

SEARCH Network Monitoring Sites (top left) and AQS Sites (top right) and 

NO3 Deposition at NADP Sites (bottom) in the Southeastern U.S. (Note: 

Additional months for SEARCH NO3 not shown as the NMB and NME exceed 

the upper axis limits.)................................................................................................ D-65

Figure D-35. Monthly Normalized Mean Bias and Normalized Mean Error at Monitoring 

Sites in the 4-km Domain for SO2 (top row, AQS sites left panel, SEARCH 

sites right panel), SO4 (middle row, CSN sites left panel, SEARCH sites right 

panel), and SO4 Deposition Measured at NADP Sites (bottom row). ...................... D-67

Figure D-36. Annual Normalized Mean Bias for Hourly SO2 (based on 12-km resolution 

CAMx results)............................................................................................................ D-68

Figure D-37. Monthly Normalized Mean Bias and Normalized Mean Error for Daily Average 

NH4 at CSN (top) and SEARCH (bottom) Network Sites in the 4-km Modeling 

Domain...................................................................................................................... D-69

Figure D-38. Monthly Normalized Mean Bias and Normalized Mean Error for Hourly CO at 

SEARCH Network Sites (left) and AQS Sites (right). ............................................... D-70

Figure D-39. Class I and Sensitive Class II Areas for Which Incremental AQ/AQRV Impacts 

Were Calculated........................................................................................................ D-74

Figure D-40. Base Scenario Ozone Design Values (DVC, top left), Future Year Ozone 

Design Values (DVF, top right) and Their Differences (DVF – DVC; bottom) 

Calculated Using the MATS UAA Tool. .................................................................... D-88

Figure D-41. MATS UAA Future Year Ozone Design Values (DFV) Calculated After First 

Removing the Hourly Contributions from a Source Group (left column) and the 

Corresponding Contributions of the Source Group to DVF (right column) 

Calculated by Subtracting the DVFs Shown in the Left-hand Column from the 

“All Sources” DVF Shown in the Top Right-hand Corner of Figure D-40. Top 

row – source group B; middle row – source group D. .............................................. D-89

Figure D-42. Modeled 4th Highest MDA8 Ozone for the Base Year (upper left) and Future 

Year (upper right) Scenarios and Their Differences (bottom center). ...................... D-90

Figure D-43. Contributions of Source Groups A (top left), B (top right), C (middle left), D 

(middle right), and E (bottom) to Future Year All-sources 4th Highest MDA8

(note different color scales in each panel)................................................................ D-92
D-x 2018 Gulf of Mexico Supplemental EIS

Figure D-44. Contributions from (left) Source Group F (natural and non-U.S. emission 

sources including boundary conditions) and (right) Boundary Conditions Only, 

to Future Year All-sources 4th Highest MDA8. .......................................................... D-93

Figure D-45. Current Year (DVC) and Future Year (DVF) Annual Average PM2.5 Design 

Values from the MATS Unmonitored Area Analysis (top left and top right, 

respectively) and the Difference, DVF – DVC (bottom)............................................ D-99

Figure D-46. Contributions of Source Groups A (top left), B (top right), C (middle left), D 

(middle right), and E (bottom) to the Future Year All-sources Annual Average 

PM2.5 Concentration Based on the MATS Unmonitored Area Analysis (note 

different color scales used in each panel). ............................................................. D-100

Figure D-47. Modeled 8th Highest Daily Average PM2.5 Concentrations for the Base Year 

(top left), Future Year (top right), and the Future – Base Difference (bottom)....... D-102

Figure D-48. Contributions of Source Groups A (top left), B (top right), C (middle left), D 

(middle right), and E (bottom) to the Future Year All-sources 8th Highest Daily 

Average PM2.5 Concentration (note different color scales used in each panel)..... D-103

Figure D-49. Contributions from (left) Source Group F (natural and non-U.S. emission 

sources including boundary conditions) and (right) Boundary Conditions Only 

to Future Year All-sources 8th Highest 24-hour PM2.5 (note use of different 

color scale in each panel). ...................................................................................... D-104

Figure D-50. Modeled Annual Average PM2.5 Concentrations for the Base Year (top left), 

Future Year (top right), and the Future – Base Difference (bottom). ..................... D-105

Figure D-51. Contributions of Source Group A (top left), B (top right), C (middle left), D 

(middle right), and E (bottom) to the Future Year All-sources Annual Average 

PM2.5 Concentration (note use of different color scales in each panel). ................ D-106

Figure D-52. Contributions from (left) Source Group F (natural and non-U.S. emission 

sources including boundary conditions) and (right) Boundary Conditions Only 

to Future Year All-sources Annual Average PM2.5 (note use of different color 

scale in each panel). ............................................................................................... D-107

Figure D-53. Modeled 2nd Highest 24-hour Average PM10 Concentrations for the Base Year 

(top left), Future Year (top right), and the Future – Base Difference (bottom)....... D-108

Figure D-54. Contributions of Source Groups A (top left), B (top right), C (middle left), D 

(middle right), and E (bottom) to the Future Year All-sources 2nd Highest Daily 

Average PM10 Concentration (note use of different color scales in each panel). .. D-109

Figure D-55. Contributions from (left) Source Group F (natural and non-U.S. emission 

sources including boundary conditions) and (right) Boundary Conditions Only 

to Future Year All-sources 2nd Highest Daily Average PM10 Concentration 

(note use of different color scale in each panel)..................................................... D-110

Figure D-56. Modeled 8th Highest 1-hour NO2 Concentrations for the Base Year (top left), 

Future Year (top right), and the Future – Base Difference (bottom). ..................... D-111

Figure D-57. Contributions of Source Group A (top left), B (top right), C (middle left), D 

(middle right) and E (bottom) to the Future Year All-sources 8th Highest Daily 

Average NO2 Concentrations (note use of different color scales in each panel)... D-112
List of Figures D-xi

Figure D-58. Modeled Annual Average NO2 Concentrations for the Base Year (top left), 

Future Year (top right), and the Future – Base Difference (bottom). ..................... D-113

Figure D-59. Contributions of Source Groups A (top left), B (top right), C (middle left), D 

(middle right), and E (bottom) to the Future Year All-sources Annual Average 

NO2 Concentrations. ............................................................................................... D-114

Figure D-60. Modeled 4th Highest Daily Maximum 1-hour SO2 Concentrations for the Base 

Year (top left), Future Year (top right), and the Future – Base Difference 

(bottom)................................................................................................................... D-116

Figure D-61. Contributions of Source Group A (top left), B (top right), C (middle left), D 

(middle right), and E (bottom) to the Future Year All-sources 4th Highest Daily 

Maximum 1-hour SO2 Concentration (note different color scales used in each 

panel). ..................................................................................................................... D-117

Figure D-62. Modeled Annual 2nd Highest Block 3-hour SO2 Concentrations for the Base 

Year (top left), Future Year (top right), and the Future – Base Difference 

(bottom)................................................................................................................... D-118

Figure D-63. Contributions of Source Group A (top left), B (top right), C (middle left), D

(middle right), and E (bottom) to the Future Year All-sources 2nd Highest 3-

hour Block Average SO2 Concentration (note different color scales used in 

each panel).............................................................................................................. D-119

Figure D-64. Modeled Annual 2nd Highest Non-overlapping Running 8-hour Average CO 

Concentrations for the Base Year (top left), Future Year (top right), and the 

Future – Base Difference (bottom). ........................................................................ D-120

Figure D-65. Modeled Annual 2nd Highest 1-hour Average CO Concentrations for the Base 

Year (top left), Future Year (top right), and the Future – Base Difference 

(bottom)................................................................................................................... D-121

Air Quality: Cumulative and Visibility Impacts D-xiii

ABBREVIATIONS AND ACRONYMS

ANC acid neutralizing capacity

AQRV air quality related value(s)

BLM Bureau of Land Management (U.S. Department of the Interior)

CAMx Comprehensive Air quality Model with eXtensions

CH4 methane

CO carbon monoxide

CO2 carbon dioxide

DAT Deposition Analysis Threshold

dv deciview

DVB design value for base year

DVC design value for current (base) year

DVF design value for future year

FLAG Federal Land Managers’ Air Quality Related Values Workgroup

GHG greenhouse gas

HAP(s) hazardous air pollutant(s)

hp horsepower

hr hour(s)

IMPROVE Interagency Monitoring of Protected Visual Environments

kg/ha-yr kilogram(s) per hectare - year

km kilometer(s)

m meter(s)

MATS Modeled Attainment Test Software

mcf Thousand cubic feet

MDA8 Annual 4th highest daily maximum running 8-hour average (concentration)

Mm-1 inverse megameters

N2O Nitrous oxide

NAAQS National Ambient Air Quality Standards

NO2 nitrogen dioxide 

NOx total oxides of nitrogen

O3 ozone

PM2.5 fine particulate matter (less than 2.5 microns in effective diameter)

PM10 inhalable particulate matter (less than 10 microns in effective diameter)

ppb parts per billion

ppm parts per million

PSD Prevention of Significant Deterioration

RRF Relative Reduction Factor

SO2 sulfur dioxide

tpy tons per year

UAA Unmonitored Area Analysis
D-xiv 2018 Gulf of Mexico Supplemental EIS

USDOI United States Department of the Interior

USEPA United States Environmental Protection Agency

VOC volatile organic compounds

WRF Weather Research and Forecasting model

yr year

μeq/l microequivalent(s) per liter

μg/m3 microgram(s) per cubic meter
Air Quality: Cumulative and Visibility Impacts D-1 

D AIR QUALITY: CUMULATIVE AND VISIBILITY IMPACTS

D.1 INTRODUCTION

The U.S. Department of the Interior’s Bureau of Ocean Energy Management (BOEM) is 

required under the Outer Continental Shelf Lands Act (OCSLA) (43 U.S.C. § 1334(a)(8)) to comply 

with the National Ambient Air Quality Standards (NAAQS) to the extent that Outer Continental Shelf 

(OCS) offshore oil and gas exploration, development, and production sources do not significantly 

affect the air quality of any state. The Gulf of Mexico OCS Region’s area of possible influence 

includes the States of Texas, Louisiana, Mississippi, Alabama, and Florida. BOEM’s Gulf of Mexico 

OCS Region manages the responsible development of oil, gas, and mineral resources for the 

430 million acres in the Western, Central, and Eastern Planning Areas (WPA, CPA, and EPA) on the 

OCS comprising the Gulf of Mexico region, including the areas under moratoria (shown in 

Figure D-1). The Clean Air Act Amendments (CAAA) of 1990 designate air quality authorities in the 

Gulf of Mexico OCS Region, giving BOEM air quality jurisdiction westward of 87°30'W. longitude and 

the U.S. Environmental Protection Agency (USEPA) air quality jurisdiction eastward of 87°30'W. 

longitude. In 2006, oil and gas leasing operations within 125 miles (201 kilometers [km]) off the 

Florida coastline were placed under moratoria until 2022 under the Gulf of Mexico Energy Security 

Act (GOMESA). The GOMESA moratoria area is depicted on Figure D-1. 

Figure D-1. Location of the “Air Quality Modeling in the Gulf of Mexico Region” Study, 

with Class I Areas (purple). 

BOEM published the Gulf of Mexico OCS Oil and Gas Lease Sales: 2017-2022; Gulf of 

Mexico Lease Sales 249, 250, 251, 252, 253, 254, 256, 257, 259, and 261—Final Multisale 

Environmental Impact Statement (2017-2022 GOM Multisale EIS) and is currently developing the 

Gulf of Mexico OCS Oil and Gas Lease Sales: 2018-2022; Gulf of Mexico Lease Sales 250, 251, 
D-2 2018 Gulf of Mexico Supplemental EIS

252, 253, 254, 256, 257, 259, and 261—Draft Supplemental Environmental Impact Statement

(2018-2022 GOM Supplemental EIS) for oil and gas resources under its jurisdiction within the Gulf of 

Mexico’s WPA, CPA, and EPA (the Proposed Action).

On August 26, 2014, BOEM contracted with Eastern Research Group, Inc. (ERG) and team 

members Ramboll Environ US Corporation (Ramboll Environ) and Alpine Geophysics, LLC (Alpine) 

to complete a comprehensive air quality modeling study in the Gulf of Mexico OCS region. Under 

BOEM Contract Number M14PC00007, “Air Quality Modeling in the Gulf of Mexico Region,”

photochemical air quality modeling was conducted to assess impacts to nearby states of OCS oil 

and gas exploration, development, and production as required under OCSLA. This assessment was

used by BOEM to disclose potential incremental and cumulative air quality impacts of a proposed 

action in the 2017-2022 GOM Multisale EIS, from which this Supplemental EIS tiers. This Technical 

Support Document (TSD) provides a detailed description of the data, modeling procedures, and 

results of the Air Quality Impact Analysis (AQIA). BOEM used this information to complete its 

analysis of potential impacts of a proposed action on air quality in the 2017-2022 GOM Multisale 

EIS, from which this Supplemental EIS tiers. 

D.1.1 Background on Air Quality Impact Analyses and Thresholds

This analysis examines the potential impacts of the 2017-2022 GOM Multisale EIS scenario, 

from which this Supplemental EIS tiers, with respect to the following: 

• the NAAQS for the criteria pollutants ozone (O3), nitrogen dioxide (NO2), sulfur 

dioxide (SO2), carbon monoxide (CO), fine particulate matter with aerodynamic 

diameter less than 2.5 μm (PM2.5) and fine plus coarse particulate matter with 

aerodynamic diameters less than 10 μm (PM10);

• air quality related values (AQRV), including visibility and acid deposition (sulfur 

and nitrogen) in nearby Class I and sensitive Class II areas (as defined below); 

and

• incremental impacts of Prevention of Significant Deterioration (PSD) pollutants 

(NO2, PM10, PM2.5) with respect to PSD Class I and Class II increments.

Note that the PSD increments are provided here for information purposes, but this analysis 

does not constitute a regulatory PSD increment consumption analysis as would be required for 

major sources subject to the New Source Review (NSR) program requirements of the Clean Air Act.

Results of each impact analysis are compared with applicable “thresholds of concern,” which 

have typically been used in air quality impact evaluations of other Federal actions, including onshore 

oil and gas leasing programs. The applicable comparison thresholds for criteria pollutant impacts 

are the corresponding NAAQS. For acid (i.e., sulfur and nitrogen) deposition impacts, thresholds are 

based on (a) incremental impacts considered sufficiently small as to have no consequential effect on 

the receiving ecosystems, i.e., Deposition Analysis Thresholds, and (b) critical load levels above 
Air Quality: Cumulative and Visibility Impacts D-3 

which cumulative ecosystem effects are likely to or have been observed. For visibility impacts, 

thresholds are based on incremental changes in light extinction below the level at which they would 

be noticeable to the average human observer. Additional information about these various thresholds 

is provided in relevant sections in the remainder of this appendix. 

D.1.1.1 Ambient Air Quality Standards

The USEPA has set NAAQS for six regulated air quality pollutants: ozone, particle pollution 

(PM2.5 and PM10), SO2, NO2, CO, and lead (Pb). After promulgation of a NAAQS, the USEPA 

designates areas that fail to achieve the NAAQS as nonattainment areas (NAAs), and States are 

required to submit State Implementation Plans (SIPs) to the USEPA that contain emission control 

plans and a demonstration that the NAA will achieve the NAAQS by the required date. After an area 

comes into attainment of the NAAQS, the area can be redesignated as a maintenance area and 

must continue to demonstrate compliance with the NAAQS.

In 1997, the USEPA promulgated the first 8-hour ozone NAAQS with a threshold of 

0.08 parts per million (ppm) (84 parts per billion [ppb]). On March 12, 2008, the USEPA 

promulgated a more stringent 0.075 ppm (75 ppb) 8-hour ozone NAAQS. Figure D-2 presents the 

current ozone nonattainment areas in the southeastern U.S. On October 1, 2015, the USEPA 

strengthened the 8-hour NAAQS for ozone to 0.07 ppm (70 ppb). Under this more stringent ozone 

NAAQS, there may be more areas in the southeastern U.S. that will be in nonattainment. The 

USEPA plans to make attainment and nonattainment designations for the revised standards by 

October 2017, with the designations based on 2014-2016 air quality data.

On December 14, 2012, the USEPA revised the PM2.5 primary NAAQS by lowering the 

annual PM2.5 NAAQS threshold from 15.0 micrograms per cubic meter (μg/m3

) to 12.0 μg/m3. The 

USEPA retained the 24-hour PM2.5 primary NAAQS at 35 μg/m3

. The 24-hour course PM NAAQS 

(PM10) was also retained at 150 μg/m3

. 
D-4 2018 Gulf of Mexico Supplemental EIS

Figure D-2. Ozone Nonattainment Areas in the Southeastern U.S. (Source: USEPA, 2016; 

https://www3.epa.gov/airquality/greenbook/map8hr_2008.html).

In February 2010, the USEPA issued a new 1-hour NO2 NAAQS with a threshold of 100 ppb 

(98th percentile daily maximum 1-hour average averaged over 3 years) and a new 1-hour SO2

NAAQS was promulgated in June 2010 with a threshold of 75 ppb (99th percentile daily maximum 

1-hour average averaged over 3 years). No areas are currently in nonattainment of either the 

annual or 1-hour NO2 NAAQS. On July 25, 2013, the USEPA designated 29 areas in 16 states as 

nonattainment for the 1-hour SO2 standard.1

 In June 2016, four additional areas were designated as 

nonattainment (Madison and Williamson Counties in southern Illinois, Anne Arundel-Baltimore 

Counties in Maryland and St. Clair County in Michigan).2

 The USEPA is currently in the process of 

gathering more information needed to complete designation of remaining unclassifiable areas with 

respect to the 1-hour SO2 NAAQS.

A new lead NAAQS was issued in 2008; NAAs for lead are associated with specific industrial 

sources. As oil and gas sources in the Gulf of Mexico OCS region produce negligible amounts of 

lead emissions and to be consistent with onshore oil and gas analysis, which does not include lead, 

lead emissions were calculated but lead was not included in the air quality analysis. The NAAQS for 

carbon monoxide has remained essentially unchanged since it was originally promulgated in 1971. 

As of September 27, 2010, all NAAs for carbon monoxide have been redesignated as maintenance 

areas.

Table D-1 summarizes the nonattainment and maintenance areas in the southeastern U.S. 

SO2 and lead NAAs are focused around specific large industrial sources of SO2 or lead emissions, 

 

1 https://www.epa.gov/sites/production/files/2016-03/documents/20130725fs.pdf 2 https://www.epa.gov/sites/production/files/2016-06/documents/so2d-r2-area-list.pdf
Air Quality: Cumulative and Visibility Impacts D-5 

whereas ozone nonattainment areas are more regional in nature, reflecting the formation of ozone 

as a secondary pollutant from emissions of NOx and VOC precursors from a wide range of sources.

Table D-1. Nonattainment and Maintenance Areas in the Southeastern U.S.

State Area 8-hr O3 

(1997)

8-hr O3 

(2008)

SO2

(2010)

CO 

(1971)

Lead 

(2008)

Alabama Troy, AL NAAa

Florida

Tampa, FL NAA

Hillsborough County, FL NAA

Nassau County, FL NAA

Louisiana Baton Rouge, LA Mb NAA

St. Bernard Parish, LA NAA

Texas

Beaumont-Port Arthur, TX M

Houston-GalvestonBrazoria, TX NAA NAA

Frisco, TX NAA a NAA = nonattainment area. b

 M = maintenance area. 

Blank cells indicate the area is in attainment of the NAAQS. 

D.1.1.2 Air Quality-Related Values

The CAAA designated 156 Class I areas consisting of National Parks and Wilderness Areas 

that are offered special protection for air quality and AQRVs. The Class I areas, compared to Class 

II areas, have lower PSD increments that new sources may not exceed and are protected against 

excessive increases in several AQRVs including visibility impairment, acid (sulfur and nitrogen) 

deposition, and nitrogen eutrophication. The Regional Haze Rule (RHR) specifies a goal of 

achieving “natural” visibility conditions by 2064 in Class I areas, and States must submit RHR SIPs 

that demonstrate progress towards that goal. Figure D-1 displays the locations of the mandatory 

Class I areas (in purple) in the Gulf of Mexico OCS region. 

In addition to the Class I areas described above, Federal Land Management (FLM) agencies 

have designated certain other areas as Class II sensitive areas for tracking PSD increment 

consumption and AQRV impacts. Sensitive Class II areas in the southeastern U.S. study region are 

shown in Figure D-3. 
D-6 2018 Gulf of Mexico Supplemental EIS

Figure D-3. Class I and Sensitive Class II Areas in the Study Region. (Note: The South Atlantic 

Planning Area was removed from the Five-Year Program.)

D.1.2 Overview of Approach

The Comprehensive Air-quality Model with extensions (CAMx; www.camx.com) and 

Community Multiscale Air Quality (CMAQ; https://www.cmascenter.org/cmaq/) Photochemical Grid 

Models (PGMs) were used to simulate the dispersion and chemical transformation of pollutants over 

the Study area. Similar to other air quality models, CAMx/CMAQ require several input datasets, 

including meteorology and an emissions inventory. Figure D-4 presents an overview of how these 

project datasets fit together for the “Air Quality Modeling in the Gulf of Mexico OCS Region” study. 

Preparation of the required meteorological and emissions data is described briefly in this TSD, along 

with references to more detailed reports.

Photochemical modeling was conducted for two emission scenarios:

• a base case scenario using the 2012 base year (BY) emissions inventory 

described in Section D.3 was used to evaluate model performance and to define 

current baseline air quality conditions; and

• a future year development scenario (FY) using an emissions inventory that 

includes potential new sources associated with the 2017-2022 GOM Multisale 
Air Quality: Cumulative and Visibility Impacts D-7 

EIS, from which this Supplemental EIS tiers, and projections of emissions to 

2017 for all other sources as described in Section D.3 was used to estimate the 

cumulative and incremental air quality and AQRV impacts of the 2017-2022

GOM Multisale EIS scenario, from which this Supplemental EIS tiers. 

Note that both scenarios used the same meteorological dataset and the same photochemical 

model configuration. 

Figure D-4. Overview of the “Air Quality Modeling in the 

Gulf of Mexico Region” Study Tasks (note 

that the meteorological model takes 

meteorological observations as inputs).

D.2 METEOROLOGY

Meteorological datasets required to determine the rate that pollutants disperse and react in 

the atmosphere include spatially and temporally varying parameters such as wind speed, wind 

direction, air temperature, and humidity, among others. Sources of meteorological information 

include datasets of measurements gathered at various locations within the Gulf of Mexico OCS 

Region domain. However, the spatial coverage of measurements is insufficient to describe the 

three-dimensional structure of the atmosphere away from measurement locations. Using 

measurement data as inputs, gridded meteorological models capable of simulating the fluid 

dynamics of the atmospheric can be used to estimate meteorological conditions over a complete 

modeling domain—including regions far from measurement sites—in a physically consistent fashion. 

Results of these meteorological models provide the inputs needed to exercise the photochemical 

grid air quality dispersion models used in this Study. For this “Air Quality Modeling in the Gulf of 

Mexico Region” study, the Advanced Research version of the Weather and Research Forecasting 

(WRF) model (version 3.7) was applied over a system of nested modeling grids. Figure D-5 shows 

the WRF modeling grids at horizontal resolutions of 36, 12, and 4 km. All WRF grids were defined 

on a Lambert Conformal Conic (LCC) projection centered at 40°N. latitude, 97°W. longitude with true 

latitudes at 33°N. and 45°N. (the “standard RPO” projection). The outermost domain (outer box) 
D-8 2018 Gulf of Mexico Supplemental EIS

with 36-km resolution includes the entire continental U.S. and parts of Canada and Mexico, and 

captures synoptic-scale (storm system-scale) structures in the atmosphere. The inner 

12-km regional grid (d02) covers the southeastern U.S. and is used to ensure that large-scale 

meteorological patterns across the region are adequately represented and to provide boundary 

conditions to the 4-km domain. The 4-km domain (d03) is centered on the coastal areas of the 

southeastern U.S. and over-water portions of the Gulf of Mexico.

Figure D-5. Meteorological (WRF model) and PGM Modeling Domains 

Including the 36-km Horizontal Grid Resolution CONUS WRF 

Domain (outer box), 12-km Resolution Southeast Regional WRF 

(white) and PGM (blue) Domains (d02), and 4-km Resolution 

Gulf of Mexico OCS Region WRF (black) and PGM (blue) 

Domains (d03).

The WRF ran the 36-, 12- and 4-km grids simultaneously with one-way nesting, meaning that 

meteorological information flows down-scale via boundary conditions introduced from the respective 

coarser to finer grids without feedback from the finer to coarser grids. The WRF modeling domain 

was defined to be slightly larger than the CAMx/CMAQ PGM modeling domains to eliminate 

boundary artifacts in the meteorological fields. Such boundary artifacts occur for both numerical 

reason (the 3:1 grid spacing ratio) and because the imposed boundary conditions require some 

time/space to come into dynamic balance with WRF’s atmospheric equations. All meteorological 

modeling domains, techniques, inputs, vertical resolution, parameters, nudging, physics options, and 

application strategy, along with quantitative and qualitative evaluation procedures and statistical 

benchmarks, are discussed in Appendix B. 
Air Quality: Cumulative and Visibility Impacts D-9 

D.3 EMISSIONS

Analysis of the cumulative air quality impacts of the 2017-2022 GOM Multisale EIS scenario

required development of both a contemporary base year emissions inventory for the base case 

analysis and a projected future year inventory that includes emissions from all cumulative sources, 

as well as additional emissions anticipated to occur under the 2017-2022 GOM OCS Multisale EIS 

alternatives in which additional exploratory drilling and construction of new shallow-water and 

deepwater platforms to support oil and gas production would occur. Both the base case and future 

year cumulative source inventories represent comprehensive compilations of pollutant emissions 

from all human activities, as well as emissions from biogenic and geogenic sources. This 

Supplemental EIS tiers from the 2017-2022 GOM Multisale EIS and uses the scenario and 

alternatives analyzed in the 2017-2022 GOM Multisale EIS.

The scope of the air pollutant emissions inventory for the “Air Quality Modeling in the Gulf of 

Mexico Region” study is defined in terms of: pollutants, representative time periods for the base case 

and future year analysis, geographical domain, and sources to be included.

D.3.1 Pollutants

Pollutants included in the inventories were selected to support analysis of air quality impacts 

in terms of impacts on attainment of NAAQS and on AQRVs, including acid deposition and visibility. 

The selected pollutants are: CO, NOx (which includes NO and NO2 and is stated in terms of 

equivalent mass of NO2), PM2.5, fine plus coarse PM (PM10), SO2, volatile organic compounds 

(VOCs, which are precursors to formation of ozone and organic particulates), and ammonia (NH3, a 

precursor to particulate matter formation). Note that lead emissions were calculated since lead is a 

criteria pollutant, but since oil and gas sources have negligible lead emissions, it was not modeled 

in the air quality analysis.

While the cumulative air quality impact analysis did not focus specifically on air toxics, 

compilation of VOC emissions by source type together with VOC speciation profiles by source type 

provides a mechanism for estimating emissions of individual air toxic species. 

D.3.2 Base Year

In determining the base case (base year) for the “Air Quality Modeling in the Gulf of Mexico 

Region” study emissions inventory, 2011 was initially selected based on data availability. Calendar 

year 2011 emissions data are readily available for most sources from the USEPA’s National 

Emissions Inventory (NEI) (USEPA, 2015a) and BOEM’s Year 2011 Gulfwide Emissions Inventory 

Study (Wilson et al., 2014). However, 2011 was an unusually hot and dry year in the Gulf of Mexico 

OCS region, particularly in Texas, which experienced record heat and dry conditions during the 

summer of 2011 and had a very high incidence of wildfires. Therefore, 2012 was selected as the 

base year as more representative of “typical” conditions in the Gulf of Mexico OCS region. 
D-10 2018 Gulf of Mexico Supplemental EIS

D.3.3 Geographical Domain

Modeling domains used for the “Air Quality Modeling in the Gulf of Mexico Region” study

emissions inventory are depicted in Figure D-5. Emissions were spatially allocated over the three 

PGM modeling domains: an outer 36-km horizontal grid resolution domain covering all of the U.S. 

and parts of Mexico and Canada; a regional 12-km resolution domain covering the southeastern 

U.S.; and an inner 4-km domain encompassing the CPA and WPA. The influences of global 

emissions on the study area are accounted for by the use of a global air quality model to specify 

domain boundary conditions. 

D.3.4 Inventory Sources

A comprehensive inventory of emissions from anthropogenic (i.e., human caused) sources, 

including stationary point and nonpoint area sources located both onshore and offshore, on-road 

motor vehicles, nonroad equipment, locomotives, marine vessels and other offshore sources, and 

airports, were compiled for the “Air Quality Modeling in the Gulf of Mexico Region” study emissions 

inventory. Table D-2 lists the source categories included in the emissions inventory, along with the 

pollutants applicable to each category, and the source type (area source, point source, offshore 

lease block). Note that emissions from non-anthropogenic sources (biogenic and geogenic sources) 

were developed in conjunction with the emissions modeling procedures described in Section D.3.9. 

Table D-2. Gulf of Mexico OCS Region Air Quality Modeling Study Source Categories. 

Group and Source Category CO NOx SO2 VOC Pb PM2.5 PM10 NH3 Source Typea NEI Onshore Sources

Point Sources         P 

Nonpoint Area 

Sources         A 

Onroad Mobile 

Sources        A 

Commercial Marine 

Vessels         P, Ab

Locomotives         P, Ac

Aircraft and Airports         P

Other Nonroad 

Mobile Sources        A 

Offshore Oil and Gas 

Sources

Platforms in State 

Waters       P 

Platforms in the CPA 

and WPA         P 

Drilling Rigs         LB

Pipelaying Vessels         LB

Support Helicopters        LB
Air Quality: Cumulative and Visibility Impacts D-11

Group and Source Category CO NOx SO2 VOC Pb PM2.5 PM10 NH3 Source Typea

Support Vessels         LB

Survey Vessels         LB

Non-oil and Gas Offshore 

Vessels and Activities

Commercial Fishing 

Vessels         LB

Commercial Marine 

Vessels         LB

Louisiana Offshore Oil 

Port         P 

Military Vessels         LB

Recreational Vessels        LB

Vessel Lightering         P

Biogenic and 

Geogenic Sources

Subsurface Oil Seeps  LB

Mud Volcanoes  LB

Onshore Vegetation   A

Wildfires and 

Prescribed Burning        P 

Windblown Dust   A

Lightning  A

Sea Salt Emissions   A

Sources in Mexico 

and Canada

Point Sources        P 

Nonpoint Area 

Sources       A 

Mobile Sources       A 

a A = area source (requires spatial surrogate); P = point source (requires UTM coordinates, stack 

parameters); LB = offshore lease block (requires GIS shape file). b Larger ports and shipping represented as shape files; smaller ports as point sources.

c Rail yards represented as point sources; railway segments as area sources.

D.3.5 Spatial Resolution

The spatial resolution of the emissions inventory is source specific. For example, sources 

such as power plants are identified based on their geographic coordinates (i.e., latitude and 

longitude), while other sources such as nonroad mobile sources (e.g., construction equipment) are 

spatially distributed using surrogates within the county in which they are reported and that are 

typically related to the activity distribution of the category (e.g., construction sites).

The resolution of the geographical area covered by the emissions inventory is based on the 

grid cell size needed for photochemical and dispersion modeling. Furthermore, the photochemical 

model grid resolution is dependent on the grid resolution of the WRF meteorological model output 

used. This is described further in Section D.3.9. 
D-12 2018 Gulf of Mexico Supplemental EIS

D.3.6 Temporal Resolution

Emissions for all sources were estimated on an annual basis (i.e., emissions generated 

during 2012). For electric generating units (EGUs), emissions were allocated on a sub-annual basis 

to reflect variations in activity using data from the USEPA. Emissions were allocated on an hourly, 

daily, and seasonal basis during the emissions modeling process (Section D.3.9) using default 

temporal allocation factors provided with the Sparse Matrix Operator Kernel Emissions model 

(SMOKE) emissions model for some sources; other temporal allocations were source specific; and 

profiles were developed and applied within the SMOKE model. 

D.3.7 Speciation

When applying the photochemical grid modeling, PM emissions were allocated to individual 

PM species as part of the SMOKE emissions processing using PM speciation factors obtained from 

the USEPA’s SPECIATE database for each source category (as defined by the Source Classification 

Code). This resulted in the PM mass being broken into the mass associated with elemental carbon 

(EC), organic aerosol (OA), primary sulfate (SO4) and nitrate (NO3) and other elements, and particlebound VOCs, such as polycyclic aromatic hydrocarbon (PAHs). The model predictions of EC will 

undergo for further analysis and discussed in the “Air Quality Modeling in the Gulf of Mexico Region” 

study final report. 

SMOKE was also used to convert VOC emissions into the photochemical mechanismspecific (e.g., CB05 or CB6r2h) model species used in air quality models as described in 

Section D.3.9. The CB6r2h chemical mechanism used in CAMx also models excess methane 

(ECH4) from local sources that is added to the background methane value (1.75 ppm) in the 

chemical mechanism. The excess methane species is calculated as part of the speciation of the 

VOC emissions that are first adjusted to total organic gases (TOG) before calculating the CB6 

chemical species. Thus, the excess methane species only includes methane emissions from local 

VOC sources (e.g., oil and gas) and will not include methane emissions not associated with VOC 

sources. 

D.3.8 Base Year and Future Year Emission Estimates

Details on the development of the base year and future year emission estimates are 

presented in Appendix C. 

D.3.9 Emissions Processing for Preparation of Model-Ready Emissions

D.3.9.1 Smoke Processing

Anthropogenic emissions inventories discussed in the previous section and other data were 

used to prepare PGM model-ready emission files using the Sparse Matrix Operator Kernel 

Emissions (SMOKE) system version 3.6 and other methods as described below. The inventories 

were processed through SMOKE to develop hourly, gridded, and speciated emissions required for 

input to the PGM models at 36-, 12-, and 4-km grid resolutions. During emissions processing, 
Air Quality: Cumulative and Visibility Impacts D-13

annual emissions inventories were speciated to model species, temporally allocated to hourly 

emissions, and spatially allocated to grid cells. 

The latest Carbon Bond 6 revision 2h (CB6r2h) photochemical mechanism with active local 

methane emissions and halogen chemistry was used for the CAMx modeling, whereas the Carbon 

Bond 5 (CB05) with updated toluene and chlorine chemistry photochemical mechanism was used for 

the CMAQ modeling, and emissions were processed accordingly. CMAQ versions 5.0 and later 

contain a thermodynamic equilibrium aerosol mechanism (ISORRPIA v2) that requires detailed 

speciation of PM2.5. This involves splitting PMFINE into additional elemental components. 

The SMOKE emissions model was used to perform the following tasks: 

• Spatial Allocation: Spatial surrogates contained in the USEPA 2011v6.2 

modeling platform3 were used to spatially distribute emissions to modeling grid 

cells. Spatial surrogates are generated by overlaying the PGM modeling grid on 

maps of geospatial indicators appropriate to each source category (e.g., housing 

units). The Surrogate Tool4

, a component of USEPA’s Spatial Allocator system, 

is used to calculate the fraction of geospatial indicator coverage in each model 

grid cell. 

• Temporal Allocation: Air quality modeling systems, such as CMAQ and CAMx, 

require hourly emissions input data. With the exception of a few source types 

(i.e., Continuous Emissions Monitoring data, biogenic emissions, and some fire 

inventories), most inventory data are estimated in the form of annual or daily 

emissions. SMOKE was used to allocate annual emissions to months and 

across the diurnal cycle to account for seasonal, day-of-week and hour-of-day 

effects. Temporal profiles and SCC cross references from the 2011v6.2 

modeling platform were used to incorporate seasonal and monthly variations into 

the development of the PGM model-ready emissions. 

• Chemical Speciation: The emissions inventories for the “Air Quality Modeling in 

the Gulf of Mexico OCS Region” study included the following pollutants: CO, 

NOx, VOC, NH3, SO2, PM10, and PM2.5. Ramboll Environ used SMOKE to 

convert inventoried VOC emissions into the CB6r2 photochemical mechanism 

model species. Chemical speciation profiles were assigned to inventory sources 

using cross-referencing data that match the profiles and inventory sources using

country/state/county (FIPS) and source classification codes (SCCs). Ramboll 

Environ used NOx, VOC, and PM speciation profiles from the 2011v6.2 platform 

for SMOKE processing. In the 2011v6.2 platform, USEPA-generated emissions 

 

3 http://www.epa.gov/ttn/chief/emch/index.html#2011

4 https://www.cmascenter.org/sa-tools/documentation/4.2/html/srgtool/SurrogateToolUserGuide_4_2.pdf
D-14 2018 Gulf of Mexico Supplemental EIS

for Carbon Bond version 6 revision 2 (CB6r2) chemical mechanism used by 

CAMx. In addition, this platform generates the PM2.5 model species associated 

with the CMAQ Aerosol Module, version 6 (AE6). SMOKE also applied sourcespecific speciation profiles to convert inventoried NOx emissions to NO, NO2, and 

HONO components. After SMOKE processing, Ramboll Environ applied 

necessary species mapping to prepare CMAQ-ready emissions in CB05/AE6 

terms and CAMx-ready emissions in CB6r2/CF terms. Note that CB6r2 

chemistry also models local excess methane (ECH4) above background 

concentrations. Sea salt and halogen emissions from the Gulf of Mexico and 

other ocean portions of the modeling domain were also generated for CAMx as 

described below.

D.3.9.2 Biogenic Emissions

Biogenic emissions were generated using the MEGAN version 2.1 biogenics model 

developed at the National Center for Atmospheric Research (Guenther et al., 2012; 

Sakulyanontvittaya et al., 2008).

Biogenic emissions depend critically upon landuse/landcover input data. Biogenic VOC and 

NO emissions vary considerably on spatial scales ranging from a few meters to thousands of 

kilometers. The MEGAN model accounts for this variability with high-resolution estimates of 

vegetation type and quantity. The MEGAN landcover variables include total Leaf Area Index (LAI), 

tree fraction, and plant species composition. These variables are determined based primarily on 

satellite observations, such as 2003 1 km2 Moderate Resolution Imaging Spectroradiometer 

(MODIS) and 30-m resolution LANDSAT data (Guenther et al., 2006; Sakulyanontvittaya et al., 

2008). MEGAN driving variables include weather data, LAI, plant functional type (PFT) cover, and 

compound-specific emission factors that are based on plant species composition. All of these 

variables are available at various temporal scales and are provided in a geo-referenced gridded 

database in several formats (e.g., netcdf, ESRI GRID). The MEGAN database has global coverage 

at 30 sec (approximately 1 km) spatial resolution.

The MEGAN model was applied using the specific daily meteorology (e.g., temperature and 

solar radiation) extracted from the 2012 WRF model outputs to generate day-specific biogenic 

emissions for the 2012 calendar year in the 36-, 12-, and 4-km PGM modeling domains.

D.3.9.3 Fire Emissions

Forest fire emissions are highly episodic and very location specific. Using annual average 

fire emissions and temporally and spatially allocating these emissions using generic allocation 

schemes would result in significant inaccuracies. In this modeling study, Ramboll Environ used 

day-specific wild and prescribed fire (together called wildland fires [WLFs]) emission estimates 
Air Quality: Cumulative and Visibility Impacts D-15

developed by the USEPA for calendar year 2012.

5 The emission estimates are based on the 

SMARTFIRE2 (SF2) framework and the BlueSky models.6

 The USEPA fire inventory was 

processed through SMOKE in separate processing streams for CMAQ and CAMx. The CMAQ 

model-ready emissions were developed in “in-line” point format. The term “in-line” means that the 

plume rise calculations are done inside the CMAQ model instead of being computed by SMOKE. To 

prepare CAMx model-ready emissions using a plume rise algorithm that is consistent with the 

algorithms in CMAQ, plume rise calculation was done in SMOKE and 3-D emissions files were 

prepared that were converted into a CAMx “PTSOURCE” type file where each grid cell centroid 

represents one virtual stack. The cmaq2uam program was used to convert 3-D fire emissions from 

SMOKE into CAMx format. Table D-3 shows total annual criteria air pollutant emissions by fire type 

for all U.S. wildland fires within each of BOEM’s PGM modeling domains.

Table D-3. 2012 Fire Criteria Air Pollutant Emissions Summary by Fire Type for BOEM’s 36-, 12-, and 

4-km Domains.

Fire Type 

(SCC) Domain CO (TPY)

NOx

(TPY)

PM10

(TPY)

PM2.5

(TPY)

SO2

(TPY)

VOC 

(TPY)

Wildfires 

(2810001000)

36 km 59,794 613 5,901 5,001 387 14,050

12 km 6,568 74 654 554 44 1,545

4 km 1,087 6 103 87 6 254

Prescribed fires 

(2810015000)

36 km 27,331 391 2,796 2,370 211 6,453

12 km 20,126 308 2,077 1,760 161 4,757

4 km 7,020 58 680 577 41 1,646

Total

36 km 87,125 1,003 8,698 7,371 598 20,503

12 km 26,694 382 2,731 2,314 206 6,302

4 km 8,107 64 783 664 47 1,900

As noted above, the USEPA wildland fires inventory is restricted to fire sources within the 

lower 48 states and thus does not cover the portions of Canada and Mexico lying within the 36-, 12-, 

and 4-km PGM domains. To fill this gap, we used 2012 day-specific Fire INventory from NCAR 

(FINN) for Canada and Mexico. The FINN provides daily, 1-km resolution, global estimates of the 

trace gas and particle emissions from open burning of biomass, which includes wildfire, agricultural 

fires, and prescribed burning exclusive of biofuel combustion and trash burning. Each fire record 

was treated as a point source and emissions were distributed vertically into multiple model layers to 

better represent each fire plume. The day-specific FINN fire emissions in Canada and Mexico were 

processed to develop elevated "point sources" of fire emissions using plume rise estimates as a 

function of fire size based on the Western Regional Air Partnership (WRAP) 2002 fire plume rise 

approach (Mavko and Morris, 2013). The chemical speciation profile for the MODIS fire emissions 

were derived from a study on biomass burning (Karl et al., 2007). 

 

5 ftp://ftp.epa.gov/EmisInventory/fires/

6 http://www.airfire.org/smartfire/
D-16 2018 Gulf of Mexico Supplemental EIS

D.3.9.4 Sea Salt and Halogen Emissions

Ramboll Environ used an emissions processor that integrates published sea spray flux 

algorithms to estimate sea salt PM emissions for input to CAMx. The gridded data for input to the 

sea salt emissions model is a land-water mask file that identifies each modeling domain grid cell as 

open ocean, surf zone, or land. Additional details on the development and evaluation of the sea salt 

emissions processor that was used for the “Air Quality Modeling in the Gulf of Mexico Region” study

are available in the WestJumpAQMS Sea Salt and Lightning memo (Morris et al., 2012). The CAMx 

sea salt emissions processor was used with the 2012 WRF data to generate sea salt emissions for 

the 36-, 12-, and 4-km modeling domains. The sea salt emissions processor has recently been 

updated to also generate emissions for halogen compounds from the ocean (Yarwood et al., 2014). 

Gridded chlorophyll data is obtained from satellite data is used as input and the processor generated 

gridded hourly emissions of chlorine, bromine, and iodine. Halogen chemistry over the ocean 

depletes ozone concentrations near the surface so is especially important in the Gulf of Mexico OCS 

region. 

The CMAQ model includes inline calculation of sea-salt emissions from the open ocean and 

coastal surf zone so no pre-processing of sea salt emissions is needed. The CMAQ does not treat 

halogen chemistry except for chlorine.

D.3.9.5 Lightning NOx Emissions

The NOx is formed in lightning channels as the heat released by the electrical discharge 

causes the conversion of nitrogen (N2) and oxygen (O2) to NO. Modeling of lightning and its 

emissions is an area of active research. For example, the mechanism for the buildup of electric 

potential within clouds is not well understood, and modeling the production, transport, and fate of 

emissions from lighting is complicated by the fact that the cumulus towers where lightning occurs 

may be sub-grid scale depending on the resolution of the model. Given the importance of lightning 

NOx in the tropospheric NOx budget and in understanding its effect on upper tropospheric ozone and 

OH-, lightning NOx is typically incorporated in global modeling (e.g., Tost et al., 2007; Sauvage et al., 

2007; Emmons et al., 2010) and has also been integrated into many regional modeling studies (e.g., 

Allen et al., 2012; Koo et al., 2010).

For the CMAQ modeling, Ramboll Environ used in-line lightning NOx emissions derived from 

the convective precipitation rate provided in the MCIP files. Since the CMAQ model includes inline 

calculation of lightening NOx emissions, no pre-processing of lightening NOx is needed. The CAMx 

model requires pre-calculated lightening emissions for input. To better facilitate comparisons with 

CMAQ, lightening NOx emissions from the CMAQ modeling were output and converted into a format 

suitable for use in CAMx.
Air Quality: Cumulative and Visibility Impacts D-17

D.3.9.6 Windblown Dust

Windblown dust emissions are calculated in-line in the CMAQ model based on wind speed 

and soil moisture parameters passed to CMAQ from the WRF model. Spatially and temporally 

resolved CMAQ windblown dust emissions were output for use in CAMx.

D.3.9.7 QA/QC of Processed Emissions

Emissions were processed by major source category in several different processing 

“streams” to simplify the emissions modeling process and facilitate the QA/QC of results. SMOKE 

includes QA and reporting features to keep track of the adjustments at each step of emissions 

processing and to ensure that data integrity is not compromised. Ramboll Environ carefully 

reviewed the SMOKE log files for significant error messages and ensure that appropriate source 

profiles are being used. In addition, SMOKE output summary reports were reviewed and compared 

with input emission totals.

D.3.9.8 Development of Model-Ready Emissions

Since the “Air Quality Modeling in the Gulf of Mexico Region” study involved application of 

both the CAMx and CMAQ photochemical grid models, the emissions processing procedure 

included development of emissions ready for input to CMAQ, as well as for input to CAMx. Each 

SMOKE processing stream generates a set of pre-merged model-ready emissions in CMAQ input 

format (netCDF). As specified in the chemical speciation section, species mapping was applied to 

convert SMOKE generated model species to the appropriate input for CMAQ. SMOKE modeling 

generated VOC model species for CB6 chemical mechanism, which were converted into CB05 

model species for CMAQ. All pre-merged gridded emissions inputs were merged together to 

generate the final CMAQ-ready, two-dimensional gridded low-level (layer 1) and point source 

emissions inputs. Since CMAQ provides the option to specify point source emissions separately 

from the gridded emissions from other sources, only distributed sources (mobile sources, area 

sources, natural emissions) were merged in developing the CMAQ-ready emissions files.

The CAMx requires two types of emissions files, as described below, for every episode day; 

both of the emission files are UAM-based Fortran binary files.

(1) Surface-level 2D emissions: This file contains two-dimensional gridded fields of 

low-level (i.e., surface) emissions rates for all emitted species to be modeled.

(2) Elevated point source emissions: The elevated point source emissions file 

contains stack parameters and emissions rates for all elevated point sources 

and emitted species to be modeled. 
D-18 2018 Gulf of Mexico Supplemental EIS

The merged two-dimensional gridded anthropogenic emissions, which were originally output 

in CMAQ format, were converted into CAMx format using the CMAQ2CAMX program7

. Ramboll 

Environ then merged natural source categories – sea salt, biogenic, fires, lightning and windblown 

dust with the surface-level emissions using the MRGUAM processor to develop CAMx model-ready 

emissions. Ramboll Environ first converted model species from CMAQ to CAMx compatible form 

and then converted CMAQ 2-D and in-line point emissions files to CAMx area-/point-source 

emissions files using the CMAQ2CAMx interface program. The point source emissions files in 

UAM-based binary format were merged together to develop the final CAMx-ready point-source 

emissions. The elevated point source file is independent of the modeling grid because it contains 

horizontal (X, Y) coordinates for each point source, and so one file includes all point sources in the 

12- and 4-km BOEM modeling grids. In addition, CAMx requires separate emissions inputs for 

source groups being tracked in the source apportionment modeling performed for the future year 

scenario.

D.3.9.9 Summary of Processed Emissions

This section presents 2012 base case and future year scenario emissions summaries for the 

BOEM 12- and 4-km domains. The summary is organized by state and by source category.

Table D-4 summarizes NOx, VOC, SO2, and PM2.5 air pollutant emissions in short tons per 

year for the states that border the Gulf of Mexico (i.e., Texas, Louisiana, Alabama, Mississippi, and 

Florida). The summary data are based on 12-km SMOKE processing of 2012 base case and future 

year inventories as described above. With the exception of fugitive dust and biogenic sources, 

emissions are summarized from the SMOKE reports generated by the SMKMRG program. Fugitive 

dust emissions were adjusted after SMOKE processing to account for fugitive dust correction factors 

derived from the Biogenic Emission Landuse Database version 3 (BELD3). Application of these dust 

transport correction factors accounts for suppression of grid-scale dust emissions via deposition on 

proximate vegetation surfaces such as roadside trees and bushes. As noted above, biogenic 

emissions were generated using the MEGAN model outside of SMOKE and so are generated 

directly on the 36/12/4-km grids rather than by state/county. Across the 5-state region, NOx

emissions were projected to go down 4% but VOC emissions are expected to increase by 3%, with 

PM2.5 emissions increasing by 10%. The largest change in emissions between the current and 

future year is for SO2 that is projected to go down by 39%.

 

7 http://www.camx.com/download/support-software.aspx
Air Quality: Cumulative and Visibility Impacts D-19

Table D-4. 2012 Base Case and Future Year Emissions Summary by State for BOEM’S 12-km 

Domain (only Gulf Coast States: Alabama, Florida, Louisiana, Mississippi, and Texas). 

States 2012 Base Year Future Year Scenario

NOx

(TPY)

PM2.5

(TPY)

SO2

(TPY)

VOC 

(TPY)

NOX

(TPY)

PM2.5

(TPY)

SO2

(TPY)

VOC 

(TPY)

Alabama 210,701 183,321 201,810 1,763,216 178,015 208,531 104,688 1,744,057

Florida 299,738 182,492 144,640 1,754,031 263,778 201,117 127,170 1,690,680

Louisiana 464,962 299,510 203,154 2,030,042 406,421 301,052 127,260 2,007,720

Mississippi 119,430 216,950 57,466 1,622,369 98,334 277,025 32,403 1,610,893

Texas 911,470 683,209 451,018 5,155,944 970,493 739,791 257,073 5,588,049

Figures D-6 through D-9 present stacked bar chart summaries for the 2012 base case 

emissions that show BOEM 12-km domain anthropogenic, fire, and biogenic emissions by source 

category and pollutants for Alabama, Florida, Louisiana, Mississippi, and Texas. Note that these 

emission summaries are only for the states (and State waters) that border the Gulf of Mexico. 

Similarly, Figures D-10 through D-13 present stacked bar chart summaries for the future year 

scenario in short tons per year for the Gulf Coast States. Emission categories used in these 

summaries are defined below:

Source Category Description

ALM Aircraft, locomotive and smaller commercial marine vessels

Fugitive Dust Anthropogenic fugitive dust from paved and unpaved roads, agricultural, 

construction, and mining sources

C3 CMV Commercial marine vessels with Category 3 (C3) main engines

Nonpoint Stationary non-point sources

Area Oil and Gas Non-point oil and gas sector onshore sources

Point Oil and Gas Point oil and gas sector onshore sources

Onroad Motorized vehicles that are normally operated on public roadways (passenger 

cars, motorcycles, minivans, sport-utility vehicles, light-duty trucks, heavy-duty 

trucks, and buses

Nonroad Off-road equipment included in USEPA's nonroad model

EGU Point Electric Generating Unit point sources

NonEGU Point NEI point sources that are not in the EGU or Point oil and gas sectors 

Fires Agricultural fires, wildfires and prescribed burning

Biogenic Vegetation and soils throughout domain

BOEM OCS Support

Vessel with Action 

(State waters only)

All BOEM OCS oil and gas support vessels and helicopter under the 2017-2022 

GOM Multisale EIS’s "Proposed Action" scenario, from which this Supplemental 

EIS tiers
D-20 2018 Gulf of Mexico Supplemental EIS

Figure D-6. BOEM’s 12-km 2012 Base Case NOx Emissions Summary in Tons per Year by Source 

Category and State (Alabama, Florida, Louisiana, Mississippi, and Texas).
Air Quality: Cumulative and Visibility Impacts D-21

Figure D-7. BOEM 12-km 2012 Base Case VOC Emissions Summary in Tons per Year by Source 

Category and State (Alabama, Florida, Louisiana, Mississippi, and Texas).
D-22 2018 Gulf of Mexico Supplemental EIS

Figure D-8. BOEM 12-km 2012 Base Case PM2.5 Emissions Summary in Tons per Year by Source 

Category and State (Alabama, Florida, Louisiana, Mississippi, and Texas).
Air Quality: Cumulative and Visibility Impacts D-23

Figure D-9. BOEM 12-km 2012 Base Case SO2 Emissions Summary in Tons per Year by Source 

Category and State (Alabama, Florida, Louisiana, Mississippi, and Texas).
D-24 2018 Gulf of Mexico Supplemental EIS

Figure D-10. BOEM 12-km Future Year NOx Emissions Summary in Tons per Year by Source Category 

and State (Alabama, Florida, Louisiana, Mississippi, and Texas).
Air Quality: Cumulative and Visibility Impacts D-25

Figure D-11. BOEM 12-km Future Year VOC Emissions Summary in Tons per Year by Source Category 

and State (Alabama, Florida, Louisiana, Mississippi, and Texas).
D-26 2018 Gulf of Mexico Supplemental EIS

Figure D-12. BOEM 12-km Future Year PM2.5 Emissions Summary in Tons per Year by Source Category 

and State (Alabama, Florida, Louisiana, Mississippi, and Texas).
Air Quality: Cumulative and Visibility Impacts D-27

Figure D-13. BOEM 12-km Future Year SO2 Emissions Summary in Tons per Year by Source Category 

and State (Alabama, Florida, Louisiana, Mississippi, and Texas).

Table D-5 summarizes NOx, VOC, SO2, and PM2.5 emissions within the 4-km domain in 

short tons for the 2012 base year and the 2017 future year scenario, and Table D-6 summarizes the 

changes in emissions between the base and future year scenarios by major source category. 

Table D-5. 2012 Base Case and Future Year Emissions Summary by Source Category for BOEM’s

4-km Domain.

Sectors 2012 Base Year (TPY) Future Year Scenario (TPY)

NOx PM2.5 SO2 VOC NOx PM2.5 SO2 VOC

Fugitive Dust 0 70,526 0 0 0 78,179 0 0

Agricultural 0 0 0 0 0 0 0 0

Fires 50,781 493,750 34,939 1,112,486 50,781 493,750 34,939 1,112,486

ALM 171,436 5,416 2,039 4,896 278,052 7,752 560 7,520

C3 CMV 68,857 3,650 36,339 2,466 108,654 2,666 25,892 4,769

Biogenic 19,015 0 0 3,140,424 19,015 0 0 3,140,424

Nonpoint 81,918 54,561 7,390 296,267 86,014 58,937 3,165 294,728

Nonroad 76,345 6,994 153 112,683 105,272 9,653 159 157,559

Area Oil and 

Gas 69,331 1,991 530 506,972 148,131 5,535 2,134 1,283,385

Onroad 270,364 8,467 1,731 145,061 183,305 7,124 940 106,904
D-28 2018 Gulf of Mexico Supplemental EIS

Sectors 2012 Base Year (TPY) Future Year Scenario (TPY)

NOx PM2.5 SO2 VOC NOx PM2.5 SO2 VOC

Non-U.S. 

Fugitive Dust 0 0 0 0 0 0 0 0 

Non-U.S. 

Area 38,832 4,361 719 15,208 35,625 4,429 502 16,787

BOEM 

Gulfwide 186,636 6,337 26,968 7,310 129,814 4,117 31,839 36,109

Non-U.S. 

Onroad 13,894 438 73 6,217 9,097 447 27 4,041

Non-U.S. 

Point (with 

GOM offshore 

platforms)

106,344 2,663 7,795 57,361 32,045 2,181 4,646 11,337

Point Oil and 

Gas 101,530 4,587 50,861 39,192 95,052 4,961 47,086 42,884

EGU Point 137,932 17,943 306,031 3,545 117,518 21,802 136,784 4,371

Non-EGU 

Point 319,924 105,264 271,961 208,773 344,080 120,826 269,191 240,212

BOEM OCS 

Platform No 

Action

0 0 0 0 84,351 837 3,205 54,449

BOEM OCS 

Platform 

w/Action

0 0 0 0 22,973 223 1,037 7,015

BOEM OCS 

Support

Vessel No 

Action

0 0 0 0 234,796 8,296 23,089 8,093

BOEM OCS 

Support

Vessel 

w/Action

0 0 0 0 106,163 9,749 396 10,238

Table D-6. Changes in Emissions between the 2012 Base Case and Future Year Emissions (short tons 

per year) by Source Category for BOEM’s 4-km Domain.

Sector Future Year - Base Year (TPY) Future Year - Base Year (%)

NOx PM2.5 SO2 VOC NOx PM2.5 SO2 VOC

Fugitive Dust 0 7,653 0 0 -- 11% -- --

Agricultural 0 0 0 0 -- -- -- --

Fires 0 0 0 0 0% 0% 0% 0%

ALM 106,616 2,336 (1,479) 2,624 62% 43% -73% 54%

C3 CMV 39,797 (984) (10,447) 2,303 58% -27% -29% 93%

Biogenic 0 0 0 0 0% -- -- 0%

Nonpoint 4,096 4,376 (4,225) (1,539) 5% 8% -57% -1%

Nonroad 28,927 2,659 6 44,876 38% 38% 4% 40%

Area Oil and Gas 78,800 3,544 1,604 776,413 114% 178% 303% 153%

Onroad (87,059) (1,343) (791) (38,157) -32% -16% -46% -26%
Air Quality: Cumulative and Visibility Impacts D-29

Sector Future Year - Base Year (TPY) Future Year - Base Year (%)

NOx PM2.5 SO2 VOC NOx PM2.5 SO2 VOC

Non-U.S. Fugitive 

Dust 0 0 0 0 -- -- -- --

Non-U.S. Area (3,207) 68 (217) 1,579 -8% 2% -30% 10%

BOEM Gulfwide (56,822) (2,220) 4,871 28,799 -30% -35% 18% 394%

Non-U.S. Onroad (4,797) 9 (46) (2,176) -35% 2% -63% -35%

Non-U.S. Point 

(with GOM 

offshore platforms)

(74,299) (482) (3,149) (46,024) -70% -18% -40% -80%

Point Oil and Gas (6,478) 374 (3,775) 3,692 -6% 8% -7% 9%

EGU Point (20,414) 3,859 (169,247) 826 -15% 22% -55% 23%

Non-EGU Point 24,156 15,562 (2,770) 31,439 8% 15% -1% 15%

Figure D-14 presents spatial plots of future year scenario NOx, VOC, PM2.5, and SO2

emissions in short tons per year within the 4-km domain for the Bureau of Ocean Energy 

Management’s OCS oil and gas production platforms under the 2017-2022 GOM Multisale EIS, from 

which this Supplemental EIS tiers. Note that the deepwater platforms have higher annual emissions 

than the shallow-water platforms. Figure D-15 presents 4-km spatial plots for the same pollutants 

and future year scenario in short tons per year for BOEM’s OCS oil and gas support vessels and 

helicopters under the 2017-2022 GOM Multisale EIS, from which this Supplemental EIS tiers. 

Figure D-16 shows emissions for the Bureau of Ocean Energy Management’s OCS oil and gas 

platforms, support vessels, and helicopters under the No Action alternative, which are the existing 

sources. Figure D-17 shows emissions for all other marine vessel activity in the Gulf of Mexico. 

Figure D-18 shows emissions for all other anthropogenic U.S. sources. 
D-30 2018 Gulf of Mexico Supplemental EIS

Figure D-14. Spatial Distribution of (clockwise starting from top left) NOx, VOC, SO2, and PM2.5

Emissions (tons per year) from New OCS Oil and Gas Production Platforms under the 

Proposed Action.
Air Quality: Cumulative and Visibility Impacts D-31

Figure D-15. Spatial Distribution of Emissions (tons per year) of (clockwise starting from top left) NOx, 

VOC, SO2, and PM2.5 from BOEM’s OCS Additional Oil and Gas Support Vessels and 

Helicopters under the Proposed Action Scenario.
D-32 2018 Gulf of Mexico Supplemental EIS

Figure D-16. Spatial Distribution of (clockwise starting from top left) NOx, VOC, SO2, and PM2.5

Emissions (tons per year) from BOEM’s OCS Oil and Gas Platforms, Support Vessels, and 

Helicopters under the No Action Alternative in BOEM’s 4-km Domain.
Air Quality: Cumulative and Visibility Impacts D-33

Figure D-17. Spatial Distribution of (clockwise starting from top left) NOx, VOC, SO2, and PM2.5

Emissions (tons per year) from All Other Marine Vessel Activity in the Gulf of Mexico under 

the Future Year Scenario in BOEM’s 4-km Domain.
D-34 2018 Gulf of Mexico Supplemental EIS

Figure D-18. Spatial Distribution of (clockwise starting from top left) NOx, VOC, SO2, and PM2.5

Emissions (tons per year) from Other Anthropogenic U.S. Sources for the Future Year 

Scenario within BOEM’s 4-km Domain.

D.3.10 Source Apportionment Design

Source apportionment, as applied in CAMx, provides a means of assessing the contributions 

of specified sources or categories of sources to predicted ozone and PM concentrations under the 

air quality conditions being simulated. Source contributions can be calculated for ozone and for PM 

using ozone or PM source apportionment routines included in CAMx. Source apportionment 

analyses were applied to the future year scenario in order to analyze the pre- and postlease OCS oil 

and gas impacts to short-term and annual NAAQS, AQRVs, and PSD increments. BOEM selected a 

set of nine source categories for source apportionment as listed in Table D-7.
Air Quality: Cumulative and Visibility Impacts D-35

Table D-7. Source Categories for Source Apportionment Calculations.

Category ID Sources

SC1 Fires (U.S., Canada, and Mexico)

SC2 Biogenic and other natural sources (e.g., lighting NOx and sea salt)

SC3

Additional BOEM OCS oil and gas production platforms associated with the 

2017-2022 GOM Multisale EIS scenario, from which this Supplemental EIS 

tiers (w/Action)

SC4

Additional BOEM oil and gas production support vessels and helicopters 

associated with the 2017-2022 GOM Multisale EIS scenario, from which this 

Supplemental EIS tiers (w/Action)

SC5 BOEM’s OCS oil and gas production platforms, support vessels, and 

helicopters under the base case (No Action) alternative

SC6 All other marine vessel activity in the Gulf of Mexico, not associated with OCS 

oil and gas activities

SC7 Other anthropogenic U.S. sources8

SC8 Mexican and Canadian anthropogenic sources9

SC9 Initial Conditions (IC)

SC10 Boundary Conditions (BC)

These source categories aggregate similar sources based on jurisdiction (i.e., sources under 

BOEM’s jurisdiction versus other Federal agencies) and sources beyond direct domestic regulatory 

control (e.g., natural emission sources and foreign sources). Additional OCS oil and gas production 

platforms and additional support vessel and helicopter trips associated with the 2017-2022 GOM 

Multisale EIS are included as a separate source category, thus providing estimates of the impacts of 

these new sources, which are projected to occur under the future year scenario associated with the 

2017-2022 GOM Multisale EIS. Platforms and support vessels and helicopters projected for the 

future year scenario under the base case (No Action) scenario are also included as a separate 

source apportionment category. This Supplemental EIS tiers from the 2017-2022 GOM Multisale 

EIS and uses the scenario and alternatives analyzed in the 2017-2022 GOM Multisale EIS.

Isolating fires and biogenic emissions shows the component of the air quality concentrations 

that are typically beyond the control of Federal agencies and states. Similarly, the Mexican and 

Canadian anthropogenic emissions are beyond the control of U.S. regulators. 

D.4 BASE CASE PHOTOCHEMICAL GRID MODELING

D.4.1 Overview

The CAMx Photochemical Grid Model (PGM) was applied on a set of nested domains with 

horizontal resolutions of 36, 12 and 4 km centered on the Gulf of Mexico OCS Region (Figure D-5). 

For the 2012 base case analysis, CAMx was run with the 2012 base case emissions described in 

 

8 Includes onshore oil and gas production sources and oil and gas production sources in State waters.

9 Also includes oil and gas production sources.
D-36 2018 Gulf of Mexico Supplemental EIS

Section D.3. Meteorological fields required by CAMx were obtained from the WRF meteorological 

model results for 2012, which were developed as described in Section D.2. Modeling procedures 

were based on the USEPA’s current and revised draft modeling guidance procedures (USEPA, 2007

and 2014). Additional features of the modeling approach are listed below.

• Anthropogenic and non-anthropogenic model-ready emissions for the 2012 base 

case were developed as described in the emission inventory TSD.

• Photochemical grid modeling was based on CAMx version 6.20 with the Carbon 

Bond 6 revision 2h (CB6r2h) photochemical mechanism, including active excess 

methane emissions and halogen chemistry. 

• Day-specific boundary conditions (BCs) for the lateral boundaries of the 36-km 

modeling domain were based on 2012 GEOS-Chem global chemistry model 

(GCM) output. 

• A model performance evaluation was conducted for the initial 2012 base case 

simulation using all available aerometric data within the modeling domain. Based 

on these initial results, a number of potential issues with model inputs were 

identified and appropriate modifications tested to confirm that the extent to which 

the modifications resolved the identified issues and resulted in improved model 

performance. These initial results and test results are described in Section D.5. 

Revised inputs were then used in the final model simulations and revised model 

performance metrics based on the final model runs were prepared. Results of 

the final model performance evaluation are also presented in Section D.5. 

D.4.2 Model Grid Configuration

The PGM domain configuration is comprised of a system of nested grids with 36-, 12-, and 

4-km horizontal resolution as shown in Figure D-5. Table D-8 provides the modeling grid definitions 

for the WRF and CAMx simulations. Since a large portion of the eastern GOM is under 

Congressional moratoria (GOMESA), the 4-km PGM domain excluded this area to limit the grid 

dimension to allow for a more manageable size for computation efficiency.

Table D-8. Domain Grid Definitions for the WRF and CAMx/CMAQ Modeling. 

Modeling 

Grid

WRF CAMx

Origin1 Coordinates 

(x, y) (km)

Grid Dimension 

(column × row)

Origin1 Coordinates 

(x, y) (km)

Grid Dimension 

(column × row)

36-km grid (-2592, -2304) (164 × 128) (-2736, -2088) (148 × 112)

12-km grid (-1008, -2016) (264 × 186) (-948, -1956) (254 × 176)

4-km grid (-156, -1704) (480 × 210) (-136, -1684) (299 × 200)

1 Southwest corner of each domain grid.

For CAMx, BCs for the 12-km domain were extracted from the 36-km simulation results, and 

the 12-and 4-km grids were modeled using 2-way nesting (allowing interactions between the two 
Air Quality: Cumulative and Visibility Impacts D-37

grids in both directions). Specification of the CAMx vertical domain structure depends on the 

definition of the WRF vertical layers structure. The WRF simulation was run with 33 vertical layer 

interfaces (which is equivalent to 32 vertical layers) from the surface up to 50 mbar (approximately 

20 km above mean sea level [AMSL]). The WRF model employs a terrain following coordinate 

system called eta (η) coordinate, which is defined by relative pressure differences between layers. 

As shown in Table D-9, the WRF levels are more finely stratified near the surface in an attempt to 

improve simulation of the atmospheric boundary layer structure and processes. A layer collapsing 

scheme is adopted for the CAMx simulations whereby multiple WRF layers are combined into single 

CAMx layers to improve the PGM computational efficiency. Table D-9 also shows the layer 

collapsing from the 32 WRF layers to 28 PGM layers. The mixing heights over the study domain are 

typically below 2 km. Therefore, the WRF modeling layers up to the 16th layer (approximately 2 km) 

are directly mapped to the PGM layers (no layer-collapsing) to better simulate the stable thermal 

stratification of the boundary layer and avoid errors potentially introduced by layer collapsing. Above 

the 20th WRF layer, two WRF layers were combined into a single PGM layer up to the 50 hPa region 

top.

Table D-9. Vertical Layer Interface Definition for WRF Simulations (left-most columns) and the 

Layer-collapsing Scheme for the CAMx/CMAQ Layers (right columns). 

WRF CAMx/CMAQ

Layer 

Interface Eta (η) Pressure (mbar)

Height 

(m)

Thickness 

(m) Layer Layer Top Height (m)

Thickness 

(m)

33 0.0 50 19,594.2 2,090.8 24 19,594.2 3,972.6

32 0.027 76 17,503.4 1,881.8

31 0.06 107 15,621.6 1,754.7 23 15,621.6 3,484.9

30 0.1 145 13,866.9 1,730.1

29 0.15 193 12,136.7 1,412.6 22 12,136.7 2,614.2

28 0.2 240 10,724.1 1,201.6

27 0.25 288 9,522.5 1,050.2 21 9,522.5 1,986.1

26 0.3 335 8,472.3 935.8

25 0.35 383 7,536.4 846 20 7,536.4 1,693.2

24 0.4 430 6,690.5 847.3

23 0.455 482 5,843.2 910.3 19 5,843.2 1,679.1

22 0.52 544 4,932.9 768.8

21 0.58 601 4,164.1 711.8 18 4,164.1 1,375.4

20 0.64 658 3,452.2 663.5

19 0.7 715 2,788.7 418.9 17 2,788.7 821.1

18 0.74 753 2,369.8 402.1

17 0.78 791 1,967.6 386.8 16 1,967.6 386.8

16 0.82 829 1,580.8 280.8 15 1,580.8 280.7

15 0.85 858 1,300.1 273.3 14 1,300.1 273.4

14 0.88 886 1,026.7 178.3 13 1,026.7 178.2

13 0.9 905 848.5 131.7 12 848.5 131.8

12 0.915 919 716.7 130.1 11 716.7 130.1

11 0.93 934 586.6 85.8 10 586.6 85.8

10 0.94 943 500.8 85.1 9 500.8 85.1
D-38 2018 Gulf of Mexico Supplemental EIS

WRF CAMx/CMAQ

Layer 

Interface Eta (η) Pressure (mbar)

Height 

(m)

Thickness 

(m) Layer Layer Top Height (m)

Thickness 

(m)

9 0.95 953 415.7 84.5 8 415.7 84.5

8 0.96 962 331.2 83.8 7 331.2 83.8

7 0.97 972 247.4 83.1 6 247.4 83.1

6 0.98 981 164.3 57.8 5 164.3 57.8

5 0.987 988 106.5 41.1 4 106.5 41.1

4 0.992 992 65.4 24.6 3 65.4 24.6

3 0.995 995 40.8 20.4 2 40.8 20.4

2 0.9975 998 20.4 20.4 1 20.4 20.4

1 1.0 1,000 0 -- -- -- --

D.4.3 Meteorology

Given the objectives of the air quality analysis and the availability of full annual WRF 

simulations for 2009 through 2013, the CAMx model was exercised for a full calendar year. The 

decision to model for an entire calendar year rather than just a single season is consistent with the 

need to address ozone, PM2.5, visibility and annual deposition. Given the extremely hot, dry, and 

smoky conditions during 2011, the 2012 calendar year was selected for the base year, base case 

modeling. 

Meteorological inputs for CAMx were generated by processing the WRF outputs using 

appropriate meteorological input preprocessors. The WRFCAMx Version 4.3 was used to translate 

WRF output meteorological fields to daily CAMx meteorological inputs. For a single day, 25 hours of 

meteorology must be present (midnight through midnight, inclusive) as these fields represent hourly 

instantaneous conditions and CAMx internally time-interpolates these fields to each model time step. 

Precipitation fields are not time-interpolated but rather time-accumulated, so cloud/precipitation files 

contain one less hour than other meteorological files (e.g., 24 hours of clouds/precipitation vs. 

25 hours for other meteorology fields). 

Several methodologies are available in WRFCAMx to derive vertical diffusivity (Kv) fields 

from WRF output. For this modeling, a method consistent with the Yonsei University (YSU) bulk 

boundary layer scheme (Hong and Noh, 2006; this is the default option in WRF) was used to 

generate the Kv profile. The lower bound Kv value is set based on the land-use type for each grid 

cell. Another issue is deep cumulus convection, which is difficult to simulate in a grid model because 

of the small horizontal spatial scale of the cumulus tower. Inadequate characterization of this 

convective mixing can cause ozone and precursor species to be overestimated in the boundary 

layer. To address this issue, a patch was developed that increases transport of air from the 

planetary boundary layer into the free troposphere and up to the cloud top within cloudy grid cells 

(ENVIRON, 2012). This patch was shown to improve surface layer ozone in a recent modeling 

study in Texas (Kemball-Cook et al., 2015), and thus was also employed in this modeling study. 
Air Quality: Cumulative and Visibility Impacts D-39

The WRFCAMx provides an option to process sub-grid cloud data from WRF fields. 

Selecting the “DIAG” sub-grid cloud method diagnoses sub-grid cloud fields from WRF gridded 

thermodynamic fields. The DIAG option is generally selected for the 36- and 12-km WRF output 

extraction but not for grid spacing less than about 10 km. However, a recent modeling study showed 

that, without the sub-grid cloud, the 4-km grid produced too much ozone over the Houston area due 

to enhanced photochemistry (Nopmongcol et al., 2014). Therefore, the DIAG option was used for 

the 4-km grid as well as the 36- and 12-km grids. 

D.4.4 Configuration of Model Input Parameters

Configuration of the CAMx model is summarized in Table D-10. Additional key configuration 

selections include the following: 

Chemical Mechanism: Gas phase chemistry using the Carbon Bond 6 revision 2h (CB6r2h) 

photochemical mechanism including active local excess methane emissions and halogen chemistry. 

For particles, CAMx was configured to use the Coarse-Fine (CF) aerosol scheme in which primary 

species are modeled using two static modes (coarse and fine), while all secondary species are 

modeled as fine particles only. 

Photolysis Rates: The CAMx requires a lookup table of photolysis rates as well as gridded 

albedo/haze/ozone/snow as input. Day-specific ozone column data are based on the Total Ozone 

Mapping Spectrometer (TOMS) data measured using the satellite-based Ozone Monitoring 

Instrument (OMI). Albedo is based on land use data, which includes enhanced albedo values when 

snow cover is present. For CAMx, there is an ancillary snow cover input that is based on WRF 

output that overrides the land use-based albedo input to use an enhanced snow cover albedo value. 

The Tropospheric Ultraviolet and Visible (TUV) Radiation Model photolysis rate processor was used. 

The CAMx is configured to use the in-line TUV to adjust for cloud cover and account for the effects 

aerosol loadings have on photolysis rates; this latter effect on photolysis may be especially important 

in adjusting the photolysis rates due to the occurrence of PM concentrations associated with 

emissions from fires. Note that the same photolysis rates are used in the 2012 base case and future 

year scenario model runs. 

Landuse: Landuse fields were generated based on U.S. Geological Survey (USGS) 

Geographic Information Retrieval and Analysis System (GIRAS) data10. The WRF 

estimated snow cover data is used to override the USGS land cover categories when 

snow cover is present.

Meteorological Inputs: The WRF-derived meteorological fields were processed to 

generate CAMx meteorological inputs for the using the WRFCAMx processor. 

 

10 http://pubs.usgs.gov/ds/2006/240/
D-40 2018 Gulf of Mexico Supplemental EIS

Plume in Grid: The subgrid-scale Plum-in-Grid module was not used to avoid 

unacceptably long model run times and given the fact that most sources in the OCS 

are far upwind of the receptor sites of interest. 

Boundary Conditions: Boundary conditions (BCs) for the 36-km domain were derived 

from a GEOS-Chem global chemistry model run for 2012 as described bove. The 

BCs for the 12/4-km model runs were based on BCs extracted from the 36-km 

simulations. 

Advection/Diffusion Methods: The piecewise parabolic method (PPM) advection 

solver was used for horizontal transport (Colella and Woodward, 1984), along with 

the spatially varying (Smagorinsky) horizontal diffusion approach. The CAMx used 

K-theory for vertical diffusion, using the CMAQ-like vertical diffusivities from 

WRFCAMx. 

Initial Conditions: The 36-km simulation used default initial conditions (ICs) that 

represent clean remote conditions. A 10-day spin-up period was then used to

eliminate any significant influence of the ICs. The ICs and BCs for the nested 

(12/4-km) grid simulations were extracted from the parent grid simulation outputs 

with a shorter (3 day) spin-up period.

Boundary Conditions: The lateral boundary conditions (BCs) for the 36-km grid were 

based on results from a GEOS-Chem GCM simulation for year 2012. The 

GEOS2CAMx processor was used to interpolate from the GEOS-Chem horizontal 

and vertical coordinate system to the CAMx coordinate system and to map the 

GEOS-Chem chemical species to the chemical mechanisms being used by CAMx. 

The use of an alternative global model (MOZART-4/GEOS5; available at 

http://www.acd.ucar.edu/wrf-chem/mozart.shtml) as a source for the BCs was 

explored via a test simulation on the 36-km domain with BCs derived from MOZART 

and subsequent comparison of model predictions with observations at rural 

monitoring sites. Results of this comparison indicated slightly worse model 

performance for ozone when using the MOZART BCs as compared to GEOS-Chem 

with mixed results for PM depending on species and monitoring network used for 

evaluation. Based on these results and the fact that, in contrast to GEOS-Chem, 

MOZART does not use day-specific values for dust emissions, resulted in the 

selection of BCs based on the GEOS-Chem model. 
Air Quality: Cumulative and Visibility Impacts D-41

Table D-10. CAMx Model Configuration.

Science Options Configuration Notes

Model Codes CAMx V6.20

Horizontal Grid 36/12/4 km Refer to Section D.2

36-km grid 148 x 112 cells

12-km grid 254 x 176 cells

4-km grid 299 x 200 cells

Vertical Grid

19 vertical layers (layercollapsed from 23 WRF 

layers)

Grid Interaction 36/12 km one-way nesting 

12/4 km two-way nesting

Initial Conditions Clean initial conditions Use 10-day spin-up for the 36-km grid; 3-day 

spin-up for the nested (12/4 km) grids

Boundary 

Conditions 36 km from GCM simulation GEOS-Chem GCM 2012 output data

Land-use Data Land-use fields based on 

USGS GIRAS data

Photolysis Rate 

Preprocessor TUV V4.8 Clear-sky photolysis rates based on day-specific Total Ozone Mapping Spectrometer (TOMS) data

Chemistry

Gas-phase CB6r2h

Updated isoprene chemistry; heterogeneous 

hydrolysis of organic nitrates; active methane 

chemistry and ECH4 tracer species (Hildebrandt 

Ruiz and Yarwood, 2013); halogen chemistry 

(Yarwood et al., 2014)

Aerosol-phase CF Coarse and fine mode aerosols

Meteorological 

Input 

Preprocessor

WRFCAMx V4.3 Compatible with CAMx V6.20

Diffusion Scheme

Horizontal-grid Explicit horizontal diffusion Spatially varying horizontal diffusivities determined 

based on the methods of Smagorinsky (1963)

Vertical-grid K-theory 1st-order closure

WRFCAMx-derived vertical diffusivities based on 

the Yonsei University (YSU) planetary boundary 

layer (PBL) scheme (Hong and Noh, 2006); landuse dependent minimum diffusivity (minimum Kv = 

0.1 to 1.0 m2

/s) with a cloud Kv patch recently 

developed to address deep convective mixing 

(ENVIRON, 2012)

Deposition Scheme

Dry deposition ZHANG03 Dry deposition scheme by Zhang et al. (2001; 2003)

Wet deposition CAMx-specific formulation Scavenging model for gases and aerosols (Seinfeld 

and Pandis, 1998)

Numerical Solvers

Gas-phase 

chemistry

Euler Backward Iterative 

(EBI) solver Hertel et al., 1993

Horizontal 

advection

Piecewise Parabolic 

Method (PPM) Colella and Woodward, 1984

Vertical 

advection

Implicit scheme w/ vertical 

velocity update 
D-42 2018 Gulf of Mexico Supplemental EIS

D.5 MODEL PERFORMANCE EVALUATION

Results from the CAMx base case model runs were compared with available air quality 

observations within the 12/4-km domain to evaluate the ability of the model to accurately reproduce 

observed conditions. Evaluation of CAMx model performance focused on ozone and PM species as 

these predictions play the primary role in the air quality impact analysis. Evaluation of the CAMx 

2012 base case simulation followed USEPA’s current (USEPA, 2007) and new draft (USEPA, 2014) 

PGM modeling guidance. The model performance evaluation (MPE) used the Atmospheric Model 

Evaluation Tool (AMET11), which is the evaluation tool discussed in USEPA’s latest PGM guidance 

(USEPA, 2014). Note that AMET requires that a monitoring site have at least 75% valid data 

capture in order to be used in the MPE, which eliminated observed data from some sites for use in 

the MPE.

D.5.1 Implications of WRF Model Performance on PGM Simulations

The WRF model performance evaluation results are presented in Appendix B. The effects 

of the meteorological model performance on PGM modeled concentrations, visibility and deposition 

is difficult to predict given the multiple effects the meteorological model can have. As described in 

Appendix B, overall WRF model performance was found to be good and significant impediments to 

PGM model performance due to errors in meteorology are not anticipated.

D.5.2 Ambient Data Used In the Model Performance Evaluation

Ozone model performance was evaluated using observed hourly and daily maximum 8-hour 

(DMAX8) ozone concentrations from the USEPA’s Air Qu ality System (AQS12) and the Clean Air 

Status and Trends Network (CASTNet13). Figure D-19 displays the locations of the AQS and 

CASTNet ozone monitoring sites used in the ozone model performance evaluation. Historically, 

CASTNet ozone monitoring sites operated by the U.S. Dept. of the Interior’s National Park Service 

(NPS) were included as part of AQS (i.e., ozone compliance monitors), while those operated by the 

USEPA were not. This has recently been changed and now all CASTNet ozone data are also 

reported in AQS. Thus, CASTNet ozone monitoring sites operated by the NPS are included in both 

the AQS and CASTNet monitoring databases. Apart from this overlap, most AQS monitoring sites 

tend to be more urban-oriented, while CASTNet sites tend to be more rural. Ramboll Environ 

therefore provides separate performance results for the AQS and CASTNet monitoring sites in order 

to provide insight into ozone performance at urban vs. rural sites.

 

11 https://www.cmascenter.org/help/documentation.cfm?MODEL=amet&VERSION=1.1

12 http://www.epa.gov/ttn/airs/airsaqs/aqsweb/

13 http://java.epa.gov/castnet/
Air Quality: Cumulative and Visibility Impacts D-43

CASTNET

AQS

Figure D-19. Ozone Monitoring Sites Used in the Model Performance 

Evaluation: CASTNet Sites in the Southeastern U.S. (top) and 

AQS Sites within the 4-km Modeling Domain (bottom) (color 

coding of AQS monitor locations is arbitrary). 

45-

A

I

S
D-44 2018 Gulf of Mexico Supplemental EIS

The PM2.5 model performance was evaluated using observed speciated PM data from CSN, 

IMPROVE, and SEARCH monitoring sites in the southeastern U.S. as shown in Figure D-20. This 

was augmented by 24-hour integrated total PM2.5 mass measurements using Federal Reference 

Method (FRM) or equivalent method monitoring sites reporting to the AQS. Most of these FRM sites 

collect samples on a 1-in-3 day schedule, although some collect data every day. The CSN data 

consist of 24-hour integrated particulate samples analyzed for SO4, NO3, NH4, EC, OC, and 

elements using a 1:3 or 1:6 day sampling frequency. The Interagency Monitoring of Protected 

Visual Environments (IMPROVE14) network collects 24-hour average PM2.5 and PM10 mass and 

speciated PM2.5 concentrations (with the exception of ammonium) using a 1:3 day sampling 

frequency. The SEARCH network data consist of hourly and 24-hour PM2.5 mass and speciated 

PM2.5 data (including ammonia). The FRM and CSN monitoring sites tend to be more urban, 

whereas the IMPROVE sites are mostly located at national parks and wilderness areas and so are 

more rural. 

There are additional monitoring sites within the modeling domain that collect hourly PM2.5

and PM10 total mass. However, automated hourly PM measurements are in some cases subject to 

additional measurement artifacts and uncertainties relative to data collected on filters and do not 

include speciated PM measurements. Although MPE results were generated using hourly PM data, 

they are not shown here to maintain consistency with the 24-hour PM NAAQS and the speciated PM 

results, as well as for the sake of brevity. Some hourly PM data, including speciated PM data, are 

available at SEARCH network sites. Comparison of MPE results for model bias and error did not 

show large overall differences between the hourly and daily SEARCH network comparisons. 

 

14 http://vista.cira.colostate.edu/IMPROVE/
Air Quality: Cumulative and Visibility Impacts D-45

CSN

IMPROVE

SEARCH (source: EPRI, 2011) 

Figure D-20. Speciated PM Monitoring Sites Used in the Model Performance Evaluation: CSN Network 

(top), IMPROVE Network (bottom left), and SEARCH Network (bottom right).

482030002

220330009

220150008 481130069

482011039

120111002

280670002 13215001

130210007

130690002

120730012

121030026

120573002

CHAS

EVER1

OKEF1

SAMA1

ROMA1
D-46 2018 Gulf of Mexico Supplemental EIS

D.5.3 Model Performance Statistics

Statistical performance measures applicable to air quality model evaluation are defined in 

Table D-11. 

Table D-11. Definitions of Model Performance Evaluation Statistical Metrics. 

Statistical Measure Mathematical 

Expression Notes

Ap: Accuracy of paired 

peak

Comparison of the peak observed value (Opeak) 

with the predicted value at same time and location

NME: Normalized Mean 

Error Reported as %

RMSE: Root Mean 

Square Error Reported as %

FE: Fractional Gross 

Error Reported as % and bounded by 0% to 200%

MAGE: Mean Absolute 

Gross Error Reported as concentration (e.g., μg/m3

) 

MNGE: Mean 

Normalized Gross Error Reported as %

MB: Mean Bias Reported as concentration (e.g., μg/m3) 

MNB: Mean Normalized 

Bias Reported as %

FB: Mean 

Fractionalized Bias Reported as %, bounded by -200% to +200%

NMB: Normalized Mean 

Bias Reported as %

For over two decades, ozone model performance for bias and error has been compared 

against the USEPA’s 1991 ozone modeling guidance model performance goals as follows (USEPA, 

1991):

• Mean Normalized Bias (MNB) ≤ ±15%

• Mean Normalized Gross Error (MNGE) ≤ 35%

peak

peak

O

− OP

∑

∑

=

=

−

N

i

i

N

i

ii

O

OP

1

1

( ) 2

1

1

1 2





 



 ∑ − =

N

i

OP ii N

∑= +

− N

i ii

ii

OP

OP

N 1

2

∑=

−

N

i

OP ii N 1

1

∑=

− N

i i

ii

O

OP

N 1

1

∑( ) =

−

N

i

OP ii N 1

1

( ) ∑=

− N

i i

ii

O

OP

N 1

1

∑= 















+

− N

i ii

ii

OP

OP

N 1

2

∑

∑

=

=

−

N

i

i

N

i

ii

O

OP

1

1

)(
Air Quality: Cumulative and Visibility Impacts D-47

In the USEPA’s 1991 ozone modeling guidance, these performance metrics were for hourly 

ozone concentrations that were consistent with the form of the ozone NAAQS in those days. The 

MNB performance statistic uses hourly predicted and observed ozone concentrations paired by time 

and location and is defined as the difference between the predicted and the observed hourly ozone 

divided by the observed hourly ozone concentrations averaged over all predicted/observed pairs 

within a given region and for a given time period (e.g., by day, month or modeling period). The 

MNGE is defined similarly only it uses the absolute value of the difference between the predicted 

and observed hourly ozone concentrations, so it is an unsigned metric. Note that, because the MNB 

and MNGE performance metrics divide by the observed ozone concentrations, they weigh 

performance for low ozone concentrations highly and can become unstable as the observed ozone 

approaches zero. Consequently, they are no longer recommended. Instead, the Fractional Bias 

and Error (FB/FE) and Normalized Mean Bias and Error (NMB/NME) are the preferred bias and error 

statistical performance measures.

For PM species, a separate set of model performance statistics and performance goals and 

criteria have been developed as part of the regional haze modeling performed by several Regional 

Planning Organizations (RPOs). The USEPA’s modeling guidance notes that PM models might not 

be able to achieve the same level of model performance as ozone models. Indeed, PM2.5 species 

definitions are defined by the measurement technology used to measure them, and different 

measurement technologies can produce very different PM2.5 concentrations. Given this, several 

researchers have developed PM model performance goals and criteria that are less stringent than 

the ozone goals that are shown in Table D-12 (Boylan, 2004; Boylan and Russell, 2006; Morris 

et al., 2009a and 2009b). However, unlike the 1991 ozone model performance goals that use the 

MNB and MNGE performance metrics, the Fractional Bias (FB) and Fractional Error (FE) are 

typically used for PM species with no observed concentration threshold screening. The FB/FE 

differs from the MNB/MNGE in that the difference in the predicted and observed concentrations are 

divided by the average of the predicted and observed values, rather than just the observed value as 

in the MNB/MNGE. This results in the FB being bounded by -200% to +200%, and the FE being 

bounded by 0% to +200%. There are additional statistical performance metrics that evaluate 

correlation, scatter, and normalized mean bias and error (NMB/NME), as shown in Table D-12. 

Table D-12. Ozone and PM Model Performance Goals and Criteria. 

Bias 

(FB/NMB)

Error 

(FE/NME) Comment

≤±15% ≤35% Ozone model performance goal that would be considered very good 

model performance for PM species

≤±30% ≤50% PM model performance Goal, considered good PM performance

≤±60% ≤75% PM model performance Criteria, considered average PM performance

More recently, the USEPA compiled and interpreted the model performance from 69 PGM 

modeling studies in the peer-reviewed literature between 2006 and March 2012 and developed 

recommendations on what should be reported in a model performance evaluation (Simon et al., 
D-48 2018 Gulf of Mexico Supplemental EIS

2012). Although these recommendations are not official USEPA guidance, their recommendations 

were integrated in this CAMx MPE.

• The PGM MPE studies should, at a minimum, report the Mean Bias (MB) and 

Error (ME or RMSE), and Normalized Mean Bias (NMB) and Error (NME) and/or 

Fractional Bias (FB) and Error (FE). Both the MNB and FB are symmetric 

around zero with the FB bounded by -200% to +200%.

• Use of the Mean Normalized Bias (MNB) and Gross Error (MNGE) is not 

encouraged because they are skewed toward low observed concentrations and 

can be misinterpreted due to the lack of symmetry around zero.

• The model evaluation statistics should be calculated for the highest resolution 

temporal resolution available (e.g., hourly ozone) and for important regulatory 

averaging times (e.g., daily maximum 8-hour ozone). 

• It is important to report processing steps in the model evaluation and how the 

predicted and observed data were paired and whether data are 

spatially/temporally averaged before the statistics are calculated.

• Predicted values should be taken from the grid cell that contains the monitoring 

site, although bilinear interpolation to the monitoring site point can be used for 

higher resolution modeling (<12 km).

• The PM2.5 should also be evaluated separately for each major component 

species (e.g., SO4, NO3, NH4, EC, OA, and remainder other PM2.5 [OPM2.5]).

• Evaluation should be performed for subsets of the data, including high observed 

concentrations (e.g., ozone >60 ppb) by subregion and by season or month.

• Spatial displays should be used in the model evaluation to evaluate model 

predictions away from the monitoring sites. Time series of predicted and 

observed concentrations at a monitoring site should also be used.

• It is necessary to understand measurement artifacts in order to make meaningful 

interpretation of the model performance evaluation.

D.5.4 Approach

The PGM evaluation focused on ozone, both hourly and daily maximum 8-hour (DMAX8) 

ozone concentrations; total PM2.5 mass and speciated PM2.5 concentrations; gaseous NO2, SO2, and 

CO concentrations; and visibility. The evaluation was performed across all monitoring sites within 

either the southeastern U.S. as shown in the top panel of Figure D-20 (in order to capture the 

regional CSN and IMPROVE network sites) or the 4-km modeling domain (Figure D-5), as well as at 

each individual site on an annual, seasonal (quarterly), and monthly basis. In addition to generating 

numerous statistical performance metrics (refer to Table D-11), graphical representation of model 

performance used three main types of displays. 
Air Quality: Cumulative and Visibility Impacts D-49

• Soccer Plots of monthly bias and error that are compared against the ozone 

performance goals and the PM performance goals and criteria (refer to 

Table D-11). Monthly soccer plots allow the easy identification of when 

performance goals/criteria are achieved and an evaluation of performance across 

seasons. 

• Spatial statistical performance maps that display bias/error on a map at the 

locations of the monitoring sites in order to better understand spatial attributes of 

model performance, along with tabular summaries of statistical performance 

metrics. 

• Time series plots that compare predicted and observed concentrations at a 

monitoring site as a function of days.

• Scatter plots of predicted and observed concentrations.

All performance statistics and displays are performed matching the predicted and observed 

concentrations by time and location using the modeled prediction in the 12/4-km grid cell containing 

the monitoring site. 

The CAMx model performance for PM was evaluated using total PM2.5 mass and speciated 

PM2.5 measurements compared against the PM performance goals and criteria given in Table D-12. 

Note that the PM goals and criteria are not as stringent as those for ozone because the 

measurements themselves, as well as the PM emissions, are much more uncertain and there are 

more processes involved in PM (e.g., dispersion, transformation and deposition of primary PM and 

formation of secondary PM from gaseous precursors). Each PM measurement technique has its 

own artifacts; different measurement technology could produce different observed PM2.5 values that 

differ by as much as 30 percent. The USEPA’s latest PGM modeling guidance includes a section on 

PM measurement artifacts for the monitoring technologies used in routine networks in the U.S. 

(USEPA, 2014). Thus, the PM model performance needs to recognize these measurement 

uncertainties and artifacts and take them into account in the interpretation of model performance, as 

even a “perfect” model may not achieve the PM performance goals and criteria.

The PM10 consists of particles with a mean aerodynamic diameter of 10 microns or less and 

consists of fine (PM2.5, i.e., particles with a diameter of 2.5 microns or less) and coarse (PMC, i.e., 

particles with a diameter between 2.5 and 10 microns) modes. The PM2.5 is composed of the 

following component species:

• sulfate (SO4) that is typically in the form of ammonium sulfate;

• nitrate (NO3) that is typically in the form of ammonium nitrate;

• ammonium (NH4) that is associated with SO4 and NO3; 

• elemental carbon (EC) that is also called black carbon (BC) and light-absorbing 

carbon (LAC);
D-50 2018 Gulf of Mexico Supplemental EIS

• organic aerosol (OA) that includes primary (POA) and secondary organic aerosol 

(SOA) and is composed or organic carbon (OC) and other atoms (e.g., oxygen) 

that are adhered to the OC; and

• other PM2.5 (OPM2.5) that is primarily crustal in nature (SOIL) but can also include 

other compounds as well as measurement artifacts.

Model performance statistics were calculated for total PM mass using observations from the 

FRM, CSN, SEARCH, and IMPROVE networks and then evaluated for PM10 and PM2.5 component 

species using data from the CSN, SEARCH, and IMPROVE sites. 

D.5.5 Initial Model Performance Results

Results of initial CAMx runs for the 36- and 12-km domains configured as described in 

Section D.4 were evaluated in terms of the MPE statistics described above to determine if any 

corrections or adjustments to model inputs were needed. In some cases, results from CAMx were 

compared with results from CMAQ to determine potential underlying causes of poor model 

performance. Results of these analyses indicated ozone and PM2.5 over prediction biases, which 

were especially pronounced along the Gulf Coast. Evaluation of results for individual PM 

components showed that much of the PM2.5 over prediction in coastal areas was associated with 

over prediction of sea salt emissions as evidenced by over prediction of sodium (Na) and 

consequently over prediction of nitrate PM as a result of nitrate substitution of chloride ions. This 

was confirmed by sensitivity tests in which sea salt emissions were reduced by a factor of five as 

suggested by regressions of predicted vs. observe Na at IMPROVE and CSN monitoring sites. 

Consistent with results of other modeling studies in the southeastern U.S., the ozone over 

prediction bias was judged to likely be associated at least in part with known over prediction biases 

of ozone over the Gulf of Mexico in many different global models, including GEOS-Chem resulting in 

over estimates of boundary condition ozone and over prediction of isoprene by the MEGAN biogenic 

model (Johnson et al., 2015). A series of sensitivity tests based on CAMx performance over the 

36-km domain with reduced ozone and ozone precursor BCs and reduced sea salt emissions 

confirmed that these modifications resulted in generally improved model performance. To this were 

added two additional modifications: the application of a commonly used adjustment to vertical 

diffusivity coefficients (Kv patch), which has been shown to improve model performance overnight 

and in urban areas (ibid); and a reduction in residential wood combustion (RWC) emissions following 

results of Adelman et al. (2014). A set of final 36-km and 12/4-km model runs were then completed 

with these modifications in place. 

D.5.6 Final Model Performance Results

After making the model input and configuration revisions described in the previous section, 

CAMx was rerun on the 36-km grid and boundary conditions extracted for the 12/4-km, two-way 

nested grid run. Results of the MPE for the 12/4-km grid run are presented in this section. 
Air Quality: Cumulative and Visibility Impacts D-51

D.5.6.1 Ozone

Model performance results for ozone are summarized in terms of monthly NMB and NME in 

soccer plots for AQS and CASTNet network monitors within the 4-km and 12-km domains in 

Figure D-21. Model performance for nearly all months is within the ±15% NMB and <35% NME 

ozone performance goals listed in Table D-12 (which corresponds to the innermost “goal” box 

shown in the figure), with the principal exceptions being performance during July and August for 

sites in the 4-km domain (note only one CASTNet site – site ALC188, Alabama-Coushatta – is 

located within the 4-km domain). 

Figure D-21. Monthly Normalized Mean Bias and Normalized Mean Error for Daily Maximum 8-hour 

Average Ozone at AQS (left) and CASTNet (right) Monitoring Sites Located within the 

4-km Modeling Domain (top) and the 12-km Domain (bottom).

As illustrated by the threshold exceedance counts in Figure D-22, the ozone season in the 

far South generally follows a bimodal distribution with a pronounced ozone peak in spring and a 

secondary peak in late summer to early fall. There is a noticeable lack of high ozone events during 

July. This seasonal pattern is reproduced in the model results as shown in Figure D-23. Model 

performance statistics generated using the AMET tool are summarized by calendar quarter. We 
D-52 2018 Gulf of Mexico Supplemental EIS

therefore focus further attention on ozone model performance results for Q2 (April-June) and Q3 

(July-September), as these roughly coincide with the seasonal ozone peaks.

Figure D-22. Fraction of Site-days during Each Month of 2012 with Observed Daily Maximum 

8-hour Ozone Exceeding 60 (top), 65 (middle), or 70 (bottom) ppb Over All Monitoring Sites 

in the 4-km Domain.
Air Quality: Cumulative and Visibility Impacts D-53

Figure D-23. Observed (blue) and Predicted (red) Monthly Mean Daily Maximum 8-hour Average Ozone 

Over All Sites in the 4-km Modeling Domain.

Ozone model performance for Q2 (April-May) and Q3 (July-September) over sites in the 

4-km domain is illustrated by the scatter plots in Figure D-24. Standard scatter plots are shown in 

the left-hand column and corresponding scatter density plots are shown in the right-hand column. 

Colors in the scatter density plot indicate the fraction of data in each 2 ppb bin, thus revealing the 

data density variations that are otherwise obscured in regions with numerous overlapping points in 

the standard scatter plots. Model performance in Q2 is better than in Q3 primarily due to a lower 

bias (NMB of 5.2% in Q2 as compared to 20.1% in Q3). The scatter density plots show that the Q3 

bias is primarily associated with over prediction of mid- and low-range values with less bias for 

values exceeding 60 ppb. Summaries of ozone performance statistics with a 60 ppb observed 

ozone cutoff applied are further discussed below. 
D-54 2018 Gulf of Mexico Supplemental EIS

Figure D-24. Scatter (left) and Scatter Density (right) Plots for Observed vs. Predicted Daily Maximum 

8-hour Ozone in Q2 (top) and Q3 (bottom) for All AQS Monitoring Sites in the 4-km Modeling 

Domain.

The spatial distribution of NMB over the full 12-km domain is shown in Figure D-25. Note 

that these results are based on the 12-km gridded model resolution for all sites shown. The NMB is 

within ±15% at most sites during Q2 but exceeds +15% at most sites along the Gulf Coast and 

throughout the southern tier and southeast Atlantic States in Q3. 
Air Quality: Cumulative and Visibility Impacts D-55

Figure D-25. Normalized Mean Bias (NMB) for Daily Maximum 8-hour Ozone for Q2 (top) and Q3 

(bottom).

The USEPA recommends that ozone model performance statistics be calculated using a 

60-ppb observed ozone concentration cut-off value (Simon et al., 2012; USEPA 2014). That is, the 

model performance statistics are calculated for all predicted and observed ozone pairs matched by 

time and location for which the observed value is 60 ppb or higher. Table D-13 lists model 

performance summary statistics derived from the 4-km resolution model output for hourly and 8-hour 

daily maximum ozone with no concentration cut-off applied and with cut-offs of 40 or 60 ppb applied 
D-56 2018 Gulf of Mexico Supplemental EIS

for Q2 and Q3. Values of NMB and NME exceeding USEPA’s performance goals as listed in 

Table D-12 are highlighted. Biases trend from positive to slightly negative as the threshold 

concentration increases but are always within the Performance Goal for Q2 and also under 

application of the 40- and 60-ppb thresholds in Q3. The NME is always within the USEPA 

Performance Goal except for hourly values in Q3 when no cut-off is applied. 

Table D-13. Model Performance Statistics at Different Observed Ozone Concentration Screening 

Thresholds Based on All Monitoring Sites in the 4-km Domain (shaded cells indicate values 

exceeding USEPA performance goals).

Monitor Site Q2 (April – June) Q3 (July – September)

N NMB (%) NME (%) NMB (%) NME (%)

USEPA Performance Goal ≤±15% ≤35% ≤±15% ≤35%

Ozone Cut-Off Concentrations DMAX8 Ozone

0 6399 5.2 14.1 6217 20.1 25.6

40 4326 2.1 11.6 3218 7.9 15.9

60 1246 -5.7 9.9 375 -9.2 12.6

Ozone Cut-Off Concentrations Hourly Ozone

0 152327 10.9 30.5 149676 30.6 46.7

40 53213 -3.5 16.7 22751 1.5 19.6

60 11229 -10.6 14.7 3498 -13.9 17.8

Time series of observed and predicted daily maximum 8-hour ozone are plotted in 

Figure D-26 for the monitoring site in each county in the Houston-Galveston-Brazoria ozone 

nonattainment area with the highest ozone design values during the 2010-2014 design value periods 

(2010-2012, 2011-2013, 2012-2014): Northwest Harris County site (AQS ID 48-201-0029)15, Manvel 

Croix Park – Brazoria County (AQS ID 48-039-1004), and Galveston 99th St. – Galveston County

(AQS ID 48-167-1034). 

Time series of observed and predicted daily maximum 8-hour ozone are plotted in 

Figure D-27 for two monitoring sites in the Baton Rouge ozone nonattainment area: LSU (AQS ID 

22-033-0003) and Carville (AQS ID 22-047-0012). These sites typically had the highest ozone 

design values in the Baton Rouge area during the 2010-2014 design value periods. 

The time series for the ALC188 (Alabama-Coushatta, Texas) CASTNet site (the only 

CASTNet site in the 4-km domain) are shown in Figure D-28. 

Overall model performance as seen in these time series is good, especially in Q2 and 

especially in the Houston-Galveston area. There is a tendency towards over prediction in Q3 at 

 

15 This site recorded either the maximum or was within 1 ppb of the maximum ozone design value of all 

sites in Harris County during this period.
Air Quality: Cumulative and Visibility Impacts D-57

Galveston and more noticeably at the Baton Rouge sites, consistent with the results for all sites 

presented above. 

Figure D-26. Time Series of Daily Maximum 8-hour Ozone at Monitoring Sites with Highest Design 

Values in Harris (top), Brazoria (middle), and Galveston (bottom) Counties, Texas, for Q2 

(left) and Q3 (right).

Figure D-27. Time Series of Daily Maximum 8-hour Ozone at Monitoring Sites in the Baton Rouge 

Nonattainment Area: LSU (top) and Carville (bottom) for Q2 (left) and Q3 (right).
D-58 2018 Gulf of Mexico Supplemental EIS

Figure D-28. Time Series of Daily Maximum 8-hour Ozone at the ALC188 (Alabama-Coushatta, Texas) 

CASTNet Monitoring Site for Q2 (top) and Q3 (bottom).

D.5.6.2 Particulate Matter

The CAMx model performance for particulate matter (PM) was evaluated for total PM2.5

mass and speciated PM2.5 measurements. The PM performance was compared against the 

performance goals and criteria given in Table D-12. Note that the PM goals and criteria are not as 

stringent as those for ozone because both PM measurements and PM emissions are subject to 

greater uncertainties and PM formation and transformation processes are more complex and difficult 

to model. Each PM measurement technique has its own artifacts; different measurement 

technologies can produce different observed PM2.5 values that differ by as much as 30 percent. The 

USEPA’s latest PGM modeling guidance includes a section on PM measurement artifacts for the 

monitoring technologies used in routine networks in the U.S. (USEPA, 2014). The PM model 

performance results must be evaluated in light of these measurement uncertainties and artifacts as 

even a “perfect” model may not achieve the PM performance goals and criteria relative to the 

imperfect measurements.
Air Quality: Cumulative and Visibility Impacts D-59

The PM10 consists of particles with a mean aerodynamic diameter of 10 microns or less and 

consists of fine (PM2.5, i.e., particles with a diameter of 2.5 microns or less) and coarse (PMC, i.e., 

particles with diameter between 2.5 and 10 microns) modes. The PM2.5 is composed of the following 

component species:

• sulfate (SO4) that is typically in the form of ammonium sulfate;

• nitrate (NO3) that is typically in the form of ammonium nitrate;

• ammonium (NH4) that is associated with SO4 and NO3; 

• elemental carbon (EC) that is also called black carbon (BC) and light-absorbing 

carbon (LAC);

• organic aerosol (OA) that includes primary (POA) and secondary organic aerosol 

(SOA) and is composed or organic carbon (OC) and other atoms (e.g., oxygen) 

that are adhered to the OC; and

• other PM2.5 (OPM2.5) that is primarily crustal in nature (SOIL) but can also include 

other compounds such as sea salt and may include measurement artifacts as it 

is determined by subtraction of the sum of individual measured species from the 

measured total PM2.5. 

In the following subsections, we first evaluate the CAMx 2012 base case simulation for total 

PM2.5 mass using observations from the FRM, CSN, and IMPROVE monitoring networks and then 

evaluate results for PM10 and PM2.5 component species. There are also numerous hourly PM2.5 and 

PM10 monitoring sites in the region that are also used in the MPE, but results for these are not 

presented here as they may suffer from additional measurement artifacts and uncertainties and are 

not directly comparable to the speciated PM data. 

D.5.6.2.1 Total PM2.5 Mass

Daily total PM2.5 mass is measured at FRM, IMPROVE, and CSN network monitors, and 

hourly PM2.5 is measured at FRM equivalent and non-FRM monitoring sites. Because only three 

CSN sites and no IMPROVE network sites are located within the 4-km CAMx modeling domain, 

some performance statistics are presented here for all monitors within the southeastern U.S. domain 

shown in Figure D-29.

16

 

16 This area corresponds to the high-resolution domain used for the meteorological (WRF) modeling 

described in Section D.2. 
D-60 2018 Gulf of Mexico Supplemental EIS

Figure D-29. PM Monitoring Sites in the Southeastern U.S. Domain (triangles – AQS hourly, 

square – IMPROVE, diamond – CSN, circles – AQS FRM daily).

Figure D-30 displays soccer plots of total PM2.5 mass model performance across the FRM, 

CSN, and IMPROVE monitoring networks in the southeastern U.S. domain. Note that these results 

are based on 12-km resolution CAMx output. Also shown in the soccer plots are boxes that 

represent the performance goals for ozone (most inner) and PM (middle), and the PM performance 

criteria (most outer). Performance for the late fall and winter months (October-February) is 

characterized by larger positive NMB and higher NME in each network. This bias is somewhat more 

extreme in the FRM data. Performance results are within or nearly within the PM performance goals 

except for January and October-December for all networks and within the PM performance criteria 

for all months at all networks.

As illustrated in Figure D-31, over prediction in Q4 appears to be primarily associated with 

“other PM2.5” (OPM2.5). Measured OPM likely consists mostly of crustal material (dust) in addition to 

sea salt. Modeled OPM2.5 is defined as the sum of unspeciated PM, crustal material, and sea salt. 

Comparisons of particulate OC and EC performance statistics are presented in Figure D-32. 

The NMB and NME are within the PM performance goals with the exception of July and August EC 

predictions at CSN sites; the over prediction bias is smaller at SEARCH sites. Note that both the 

SEARCH and CSN networks use the Thermal Optical Reflectance (TOR) method to determine OC 

and EC.
Air Quality: Cumulative and Visibility Impacts D-61

Figure D-30. Soccer Plots of Total PM2.5 Mass Model Performance Across the IMPROVE (top left), CSN 

(top right), SEARCH (bottom left), and FRM Daily (bottom right) Monitoring Networks for 

Sites in the Southeastern U.S. Domain.
D-62 2018 Gulf of Mexico Supplemental EIS

Figure D-31. Comparisons of Predicted with Observed Daily Average PM at CSN Network Sites in the 

Southeastern U.S. for Q2 (left) and Q4 (right) for Total PM2.5 (top), Other PM2.5 (middle), 

and Sodium (bottom).
Air Quality: Cumulative and Visibility Impacts D-63

Figure D-32. Comparisons of Observed vs. redicted OC (top) and EC (bottom) at SEARCH (left) and 

CSN (right) Network Sites in the Southeastern U.S.

D.5.6.2.2 Nitrogen Species (NO2, NOy, and NO3) 

Soccer plot summaries of NMB and NME for nitrogen species are shown in Figures D-33

and D-34 for monitoring sites in the 4-km domain. The NO2, NOy, and particulate NO3 are over 

predicted, especially in the summer months. The NO3 over prediction at coastal sites could be at 

least partially due to over prediction of sea salt emissions as a result of Cl- ion substitution. This is 

consistent with under prediction of particulate Cl at some sites despite over prediction of Na. Nitrate 

deposition biases fall within the performance criteria in all but one month, but errors are large 

indicating a lack of model precision. Measurement uncertainties may also be contributing to the 

large errors. 
D-64 2018 Gulf of Mexico Supplemental EIS

N/A

Figure D-33. Monthly Normalized Mean Bias and Normalized Mean Error for Hourly NO2 (top) and Daily 

NOy (bottom) at SEARCH Network Sites (left) and AQS Sites (right) in the 4-km Domain.
Air Quality: Cumulative and Visibility Impacts D-65

Figure D-34. Monthly Normalized Mean Bias and Normalized Mean Error for NO3 at SEARCH Network 

Monitoring Sites (top left) and AQS Sites (top right) and NO3 Deposition at NADP Sites 

(bottom) in the Southeastern U.S. (Note: Additional months for SEARCH NO3 not shown as 

the NMB and NME exceed the upper axis limits.) 
D-66 2018 Gulf of Mexico Supplemental EIS

D.5.6.2.3 Sulfur Species (SO2 and SO4) 

Model performance for hourly SO2 within the 4-km domain is summarized in terms of 

monthly NME and NMB in Figure D-35. The AQS network SO2 monitors are typically cited to 

represent the influence of major utility or industrial SO2 sources and thus may measure short-term 

peaks associated with plume impacts from a discrete source. As a result, the timing, location, and 

magnitudes of peak SO2 concentrations are not well represented within the 4-km grid modeling 

results. In addition, monitors near large ports may be influenced by discrete plumes from passing 

marine vessels, which could be sufficient to cause 1-hour peaks in the monitoring data. Since 

marine vessel emission inputs to the model are temporally averaged, these discrete events cannot 

be properly simulated by the model. Given these characteristics of the SO2 monitoring data, we 

would expect large 1-hour SO2 modeling errors as shown in Figure D-35, although we would not 

necessarily expect the positive normalized mean biases that occur in every month. 

Over prediction bias of hourly SO2 at SEARCH network sites seen in the top row of 

Figure D-35 is in contrast to lower SO4 bias shown in the next row. Good performance for SO4 is 

also evident at CSN network sites. The SO4 deposition is under predicted in most months. Reasons 

for the overall SO2 over prediction bias at sites in the 4-km domain (top row of Figure D-33) are not 

immediately apparent. Examination of results over all sites in the 12-km domain (Figure D-36) 

shows wide variations in bias from site-to-site, including between sites in the 4-km domain, 

suggesting that the lower bias in the network average performance statistics in Figure D-33 are 

partly the result of over- and under-predictions cancelling each other out. 
Air Quality: Cumulative and Visibility Impacts D-67 SO2 SO4 SO4 Deposition

Figure D-35. Monthly Normalized Mean Bias and Normalized Mean Error at Monitoring Sites in the 

4-km Domain for SO2 (top row, AQS sites left panel, SEARCH sites right panel), SO4

(middle row, CSN sites left panel, SEARCH sites right panel), and SO4 Deposition 

Measured at NADP Sites (bottom row). 
D-68 2018 Gulf of Mexico Supplemental EIS

Figure D-36. Annual Normalized Mean Bias for Hourly SO2 (based on 12-km resolution CAMx 

results).

D.5.6.2.4 Ammonium (NH4) 

Model performance for particulate ammonium at monitors within the 4-km domain is 

summarized in terms of monthly NME and NMB in Figure D-37. Performance at the two SEARCH 

network sites falls within the PM criteria bounds, but positive biases and large errors are seen at the 

three CSN sites. Note that results based on all sites in the southeastern U.S. domain (at 

12-km resolution) are very similar. The NH4 overestimation bias at the CSN sites is likely due to NO3

over-prediction (Figure D-34), as SO4 is showing biases closer to zero (Figure D-35). Examination 

of individual CSN site results shows acceptable performance at the Houston site (NMB=20%, 

NME=59%), but large positive biases and errors at the Baton Rouge, Louisiana, and Laurel, 

Mississippi, monitors. 
Air Quality: Cumulative and Visibility Impacts D-69

Figure D-37. Monthly Normalized Mean Bias and Normalized Mean Error for Daily Average NH4 at CSN 

(top) and SEARCH (bottom) Network Sites in the 4-km Modeling Domain.
D-70 2018 Gulf of Mexico Supplemental EIS

D.5.6.2.5 Carbon Monoxide (CO)

Model performance for hourly CO within the 4-km domain is summarized in terms of monthly 

NME and NMB in Figure D-38. Hourly CO is under predicted on average at AQS sites where the 

influenced of local mobile sources at sub-grid scales is not adequately resolved by the model’s 4-km 

grid resolution; model performance is better at the SEARCH sites, several of which are in rural 

locations. 

Figure D-38. Monthly Normalized Mean Bias and Normalized Mean Error for Hourly CO at SEARCH 

Network Sites (left) and AQS Sites (right).

D.6 AIR RESOURCE ASSESSMENT APPROACH

D.6.1 Future Year Modeling

The CAMx was run with the Future Year scenario emissions inventory, including emissions 

from the 2017-2022 GOM Multisale EIS sources described in Appendix C; this Supplemental EIS 

tiers from the 2017-2022 GOM Multisale EIS. Model results were post-processed for analysis of air 

quality impacts with respect to the NAAQS and AQRVs; PSD increments were also calculated for 

information purposes. Source apportionment technology was used to provide estimates of source 

group impacts, including impacts of potential new sources associated with the 2017-2022 GOM 

Multisale EIS, from which this Supplemental EIS tiers. Details of the source apportionment and 

post-processing procedures are presented in this section. 

D.6.1.1 Source Apportionment Design

The CAMx Ozone Source Apportionment Technology (OSAT) and Particulate Source 

Apportionment Technology (PSAT) tools were used to obtain the separate air quality, deposition, 

and visibility impacts associated with existing and new (2017-2022 GOM Multisale EIS, from which 

this Supplemental EIS tiers) OCS oil and gas development in the GOM, as well as from other 

emission sources in the GOM and several other source categories as described in Appendix C. 

The CAMx OSAT and PSAT source apportionment tools use reactive tracers that operate in parallel 

to the host PGM to provide air quality and deposition contributions due to user-selected source 
Air Quality: Cumulative and Visibility Impacts D-71

groups. The CAMx determines the contributions of emissions from each source category to the total 

CAMx model concentrations and depositions during the course of the simulation. A detailed 

description of the CAMx source apportionment tools is available in the CAMx user’s guide 

(ENVIRON, 2014).

The Anthropogenic Precursor Culpability Assessment (APCA) version of the CAMx Ozone 

Source Apportionment Technology (OSAT) was used in the future year scenario modeling. The 

APCA differs from OSAT in that it distinguishes between natural and anthropogenic emissions; when 

ozone is formed due to the interaction of biogenic VOC and anthropogenic NOx under VOC-limited 

conditions, a case OSAT would assign the ozone formed to the biogenic VOC, APCA recognizes 

that biogenic VOC is uncontrollable and re-directs the ozone formed to the anthropogenic NOx. 

Thus, APCA only assigns ozone formed to natural emissions when it is due to natural VOC 

interacting with natural NOx emissions. The APCA requires that the first source category is always 

natural emissions. Like OSAT, APCA uses four reactive tracers to track the ozone contributions of 

each source group: NOx emissions (Ni); VOC emissions (Vi);and ozone formed under VOC-limited 

(O3Vi) and NOx-limited (O3Ni) conditions.

For PM, three families of Particulate Source Apportionment Technology (PSAT) source 

apportionment tracers were used to track contributions of SO4, NO3/NH4, and primary PM that 

require, respectively, 2, 7, and 6 reactive tracers for each family. Thus, combined APCA/PSAT 

source apportionment uses 19 reactive tracers to track the contribution of each source category. 

The Secondary Organic Aerosol (SOA) family of PSAT tracers was not used in the future year 

scenario source apportionment modeling because (1) only a few specific kinds of VOC species form 

SOA (i.e., isoprene, terpenes, sesquiterpenes, and aromatics), and these VOCs are mainly emitted 

by biogenic sources with some aromatic species (e.g., toluene and xylene) emitted by anthropogenic 

sources (e.g., gasoline combustion) (emissions from oil and gas exploration and production has 

negligible aromatic VOC emissions); and (2) the chemistry of SOA is quite complex, involving 

numerous gaseous, semi-volatile, and particulate species so that PSAT requires 21 tracers to track 

the SOA contributions of each source group (Morris et al., 2015). As a result, including SOA would 

more than double the number of reactive tracers, resulting in doubling of the computer time needed 

for the CAMx source apportionment run. 

D.6.1.2 Future Year Source Apportionment Simulation

The CAMx 2017 source apportionment simulation was conducted for 1 January to 

31 December calendar year over the 12-km southeastern U.S. modeling domain shown in 

Figure D-5. The boundary conditions (BCs) defining inflow concentrations around the lateral 

boundaries of the 12-km domain were obtained from a future year CAMx simulation of the 36-km 

continental U.S. (CONUS) domain shown in Figure D-5. Both the 36-km and 12-km simulations 

made use of the same 2012 WRF meteorology and model configuration used in the base case 

simulation. 
D-72 2018 Gulf of Mexico Supplemental EIS

D.6.2 Post-Processing of Future Year Source Apportionment Modeling Results

D.6.2.1 Overview

The CAMx future year scenario model and ozone and particulate matter source 

apportionment modeling outputs were post-processed for comparison against the NAAQS and PSD 

concentration increments listed in Table D-14 and other thresholds of concern (TOC), as discussed 

below. For analyzing NAAQS and AQRV impacts at Class I and sensitive Class II areas, the 

Thresholds of Concern (TOCs) used were as defined by the Federal Land Manager (FLM) that 

manages each Class I/II area as prescribed in the June 23, 2011, Memorandum of Understanding 

(MOU) for evaluating onshore oil and gas AQ/AQRV impacts.17

The CAMx source apportionment results for individual source categories were used to 

evaluate the incremental impacts of each of a set of hierarchical source groups as defined in 

Table D-15. Note that Source Group B represents all new direct emissions associated with the 

2017-2022 GOM Multisale EIS, from which this Supplemental EIS tiers, and Source Group C 

represents these sources in addition to all existing OCS platforms and associated support vessel 

and aircraft activity. Also note that Source Group E includes Source Groups A-D, along with all 

other anthropogenic sources, but excludes fires and other natural sources (biogenics, lightning NOx, 

sea salt) and the contribution of boundary conditions. 

Table D-14. NAAQS and PSD Increments. 

Pollutant Pollutant/Averaging 

Time NAAQS PSD Class I Increment1

PSD Class II 

Increment1

CO 1-hour2 35 ppm 40,000 

μg/m3 -- --

CO 8-hour2 9 ppm 10,000 μg/m3 -- --

NO2 1-hour3 100 ppb 188 μg/m3 -- --

NO2 Annual4 53 ppb 100 μg/m3 2.5 μg/m3 25 μg/m3

O3 8-hour5 0.070 ppm 137 

μg/m3 -- --

PM10 24-hour6 150 μg/m3 8 μg/m3 30 μg/m3

PM10 Annual7 -- 4 μg/m3 17 μg/m3

PM2.5 24-hour8 35 μg/m3 2 μg/m3 9 μg/m3

PM2.5 Annual9 12 μg/m3 1 μg/m3 4 μg/m3

SO2 1-hour10 75 ppb 196 μg/m3

SO2 3-hour11 0.5 ppm 1,300 μg/m3 25 μg/m3 512 μg/m3

SO2 24-hour -- 5 μg/m3 91 μg/m3

SO2 Annual4 -- 2 μg/m3 20 μg/m3

 

17 http://www.epa.gov/compliance/resources/policies/nepa/air-quality-analyses-mou-2011.pdf
Air Quality: Cumulative and Visibility Impacts D-73

Pollutant Pollutant/Averaging 

Time NAAQS PSD Class I Increment1

PSD Class II 

Increment1

1 The PSD demonstrations serve information purposes only and do not constitute a regulatory PSD 

increment consumption analysis.

2 No more than one exceedance per calendar year. 3

 98th percentile, averaged over 3 years. 4 Annual mean not to be exceeded. 5 Fourth-highest daily maximum 8-hour ozone concentrations in a year, averaged over 3 years, 

NAAQS promulgated December 28, 2015. 6 Not to be exceeded more than once per calendar year on average over 3 years. 7

 3-year average of the arithmetic means over a calendar year. 8

 98th percentile, averaged over 3 years. 9 Annual mean, averaged over 3 years, NAAQS promulgated December 14, 2012. 10 99th percentile of daily maximum 1-hour concentrations in a year, averaged over 3 years. 11 No more than one exceedance per calendar year (secondary NAAQS). 

Table D-15. Source Group for Incremental Impacts Analysis. 

Source 

Group 

Included Source 

Categoriesa Comment

A SC3

New oil and gas platform sources under the 2017-2022 GOM 

Multisale EIS scenario, from which this Supplemental EIS tiers

(w/Action)

B SC3, SC4 Add support vessels and aircraft associated with new platform 

sources (w/Action)

C SC3, SC4, SC5

Add oil and gas platforms and associated support vessels and 

aircraft under the No Action alternative (existing base case 

sources)

D SC3, SC4, SC5, 

SC6

Add all other marine vessel activity in the GOM, not associated 

with OCS oil and gas activities

E SC3, SC4, SC5, 

SC6, SC7, SC8 Add all other U.S. and non-U.S. anthropogenic sources

F SC1, SC2, SC8, 

SC10

Natural and non-U.S. sources (including U.S. sources outside of 

the 12-km modeling domain) a Refer to Table D-6.

D.6.2.2 Comparison against NAAQS

The CAMx future year scenario predicted total concentrations from all emission sources 

were post-processed for comparison to the applicable NAAQS, as listed in Table D-14, in two 

different ways. First, the CAMx predictions were compared directly against each NAAQS. This is 

referred to as the “absolute” prediction comparison. These absolute prediction comparisons may be 

misleading in cases in which the model exhibits significant prediction bias. In recognition of this, 

USEPA modeling guidance (USEPA, 2007 and 2014) recommends using the model in a relative 

sense when projecting future year ozone, PM2.5, and regional haze levels; and the USEPA has 

developed the Modeled Attainment Test Software (MATS; Abt., 2014) for making such future year 

projections. This approach uses the ratio of future year to current year modeling results to develop 

Relative Response Factors (RRFs) that are applied to observed current year Design Values 

(abbreviated as either DVC or DVB) to make future year Design Value (DVF) projections (i.e., 
D-74 2018 Gulf of Mexico Supplemental EIS

DVF = DVC x RRF). The MATS was applied to the prediction of both ozone and PM2.5 DVFs. The 

MATS was also used for assessing the cumulative visibility impacts at IMPROVE monitoring sites in 

the 12-km domain, as discussed in more detail below.

D.6.2.3 Impacts at Class I and Sensitive Class II Areas

The incremental AQ/AQRV contributions associated with emissions from each source group 

listed in Table D-15 were calculated at the Class I and sensitive Class II areas shown in 

Figure D-39. The selected areas include all Class I and sensitive Class II areas within the 

4-km modeling domain plus additional Class I areas within the 12-km modeling domain. 

Table D-16 lists those areas that are located in Gulf Coast or nearby states and thus are of 

greatest interest to this analysis. Refer to Section D.7.3.1 for a complete list of all areas shown in 

Figure D-39, along with the results of the visibility analyses. 

Receptors for each Class I and sensitive Class II area were defined based on the spatial 

extent of the Class I/II area defined using shapefiles obtained from the applicable Federal Land 

Management Agency. A GIS was used to determine the set of grid cells overlapping each area by at 

least 5%. Model results for the identified grid cells were then used to represent predicted ambient 

concentrations and deposition in each area. 

Figure D-39. Class I and Sensitive Class II Areas for Which Incremental AQ/AQRV Impacts 

Were Calculated.
Air Quality: Cumulative and Visibility Impacts D-75

Table D-16. Class I and Sensitive Class II Areas in Gulf Coast and Nearby States.

Type Name Agency1 State Modeling Domain

Class I Breton Wilderness FWS LA 4 km

Class II Breton NWR FWS LA 4 km

Class II Gulf Islands NS NPS MS, FL 4 km

Class II Padre Island NS NPS TX 4 km

Class I Bradwell Bay FS FL 12 km

Class I St. Marks FWS FL 12 km

Class I Chassahowitzka FWS FL 12 km

Class I Everglades NP NPS FL 12 km

Class I Okefenokee FWS GA 12 km

Class I Wolf Island FWS GA 12 km

Class I Cohutta FS GA 12 km

Class I Sipsey FS AL 12 km

Class I Guadalupe Mountains NPS TX 12 km

Class I Big Bend NPS TX 12 km

Class I Wichita Mountains FWS OK 12 km

Class I Caney Creek FS AR 12 km

Class I Upper Buffalo FS AR 12 km

1 FWS = U.S. Dept. of the Interior, Fish and Wildlife Service; FS = U.S. Dept. of Agriculture, 

Forest Service; NPS = U.S. Dept. of the Interior, National Park Service; NS = National 

Seashore; NWR = National Wildlife Refuge.

D.6.2.3.1 Incremental Visibility Impacts

Visibility impacts were calculated for each source group using incremental concentrations as 

quantified by the CAMx PSAT tool. Changes in light extinction from CAMx model concentration 

increments due to emissions from each source group were calculated for each day at grid cells 

representing each Class I and sensitive Class II area. The FLAG (2010) procedures were used in 

the incremental visibility assessment analysis.

The visibility evaluation metric used in this analysis is based on the haze index (HI), which is 

measured in deciview (dv) units and is defined as follows:

HI = 10 × ln[bext/10]

Where bext is the atmospheric light extinction measured in inverse megameters (Mm-1) and is 

calculated primarily from atmospheric concentrations of particulates.

A more intuitive measure of haze is visual range (VR), which is defined as the distance at 

which a large black object just disappears from view, and is measured in km. Visual range is related 

to bext by the formula VR = 3912/bext. The advantage of using the HI rather than VR is that a given 

change in HI is approximately associated with the same degree of perceived change in visibility 

regardless of the baseline conditions whereas small changes in VR are much more noticeable under 

clean conditions as compared to hazy conditions.
D-76 2018 Gulf of Mexico Supplemental EIS

The incremental concentrations due to each source group were added to natural background 

extinction in the extinction equation (bext) and the difference between the haze index with the source 

group concentrations included and the haze index based solely on natural background 

concentrations is calculated. This quantity is the change in haze index, which is referred to as “delta 

deciview” (Δdv):

Δdv = 10 × ln[bext(SC+background)/10] - 10 × ln[bext(background)/10]

Δdv = 10 × ln[bext(SC+background)/bext(background)] 

Here bext(SCi+background) refers to atmospheric light extinction due to impacts from the source 

category plus background concentrations, and bext(background) refers to atmospheric light extinction due 

to natural background concentrations only.

For each source group, the estimated visibility degradation at the Class I areas and sensitive 

Class II areas due to the source group are presented in terms of the number of days that exceed a 

threshold change in deciview (Δdv) relative to background conditions. The number of days with a 

deciview greater than 0.5 and 1.0 are reported.

IMPROVE Reconstructed Mass Extinction Equations

The FLAG (2010) procedures for evaluating visibility impacts at Class I areas use the revised 

IMPROVE reconstructed mass extinction equation to convert PM species in μg/m3 to light extinction 

(bext) in inverse megameters (Mm-1) as follows:

bext = bSO4 + bNO3 + bEC + bOCM + bSoil + bPMC+ bSeaSalt+ bRayleigh+ bNO2

where

bSO4 = 2.2 × fS(RH) × [Small Sulfate] + 4.8 × fL(RH) × [Large Sulfate]

bNO3 = 2.4 × fS(RH) × [Small Nitrate] + 5.1 × fL(RH) × [Large Nitrate]

bOCM = 2.8 × [Small Organic Mass] + 6.1 × [Large Organic Mass]

bEC = 10 × [Elemental Carbon]

bSoil = 1 × [Fine Soil]

bCM = 0.6 × [Coarse Mass]

bSeaSalt = 1.7 × fSS(RH) × [Sea Salt]

bRayleigh = Rayleigh Scattering (Site-specific)

bNO2 = 0.33 × [NO2 (ppb)] {or as: 0.1755 × [NO2 (μg/m3

)]}.

f(RH) are relative humidity adjustment factors that account for the fact that sulfate, nitrate, 

and sea salt aerosols are hygroscopic and are more effective at scattering solar radiation at higher 
Air Quality: Cumulative and Visibility Impacts D-77

relative humidity. FLAG (2010) recommends using monthly average f(RH) values rather than the 

hourly averages recommended in the previous FLAG (2000) guidance document in order to 

moderate the effects of extreme weather events on the visibility results. 

The revised IMPROVE equation treats “large sulfate” and “small sulfate” separately because 

large and small aerosols affect an incoming beam of light differently. However, the IMPROVE 

measurements do not separately measure large and small sulfate; they measure only the total PM2.5

sulfate. Similarly, CAMx writes out a single concentration of particulate sulfate for each grid cell. 

Part of the definition of the new IMPROVE equation is a procedure for calculating the large and 

small sulfate contributions based on the magnitude of the model output sulfate concentrations; the 

procedure is documented in FLAG (2010).18 The sulfate concentration magnitude is used as a 

surrogate for distinguishing between large and small sulfate concentrations. For a given grid cell, 

the large and small sulfate contributions are calculated from the model output sulfate (which is the 

“Total Sulfate” referred to in the FLAG [2010] guidance) as

For Total Sulfate <20 μg/m3

: 

[Large Sulfate] = ([Total Sulfate] / 20 μg/m3

) × [Total Sulfate]

For Total Sulfate ≥20 μg/m3

: 

[Large Sulfate] = [Total Sulfate]

For all values of Total Sulfate:

[Small Sulfate] = [Total Sulfate] – [Large Sulfate]

The procedure is identical for nitrate and organic mass. 

The PSAT source apportionment algorithm does not separately track NO2 concentrations but 

instead tracks total reactive nitrogen (RGN) that consists of NO, NO2, and other reactive nitrogen 

compounds (e.g., N2O5, HONO, etc.). Thus, for each hour and each grid cell representing a 

Class I/II area, a source group’s incremental PSAT RGN contribution is converted to NO2 by 

multiplying by the total (all emissions) CAMx model NO2/RGN concentration ratio. Note that this 

same procedure is also used for contributions to NO2 concentrations.

Although sodium and particulate chloride are treated in the CAMx core model, these species 

are not carried in the CAMx PSAT tool. This does not affect the calculations of visibility impacts from 

individual source groups other than impacts from the natural source category (SC2). 

 

18 http://www.nature.nps.gov/air/Pubs/pdf/flag/FLAG_2010.pdf
D-78 2018 Gulf of Mexico Supplemental EIS

Predicted daily average modeled concentrations due to each source group for receptor grid 

cells containing Class I and sensitive Class II areas were processed using the revised IMPROVE 

reconstructed mass extinction equation FLAG (2010) to obtain changes in bext at each sensitive 

receptor area that are converted to deciview and reported.

Annual average natural conditions for each Class I area were obtained from Table 6 in FLAG 

(2010) and monthly relative humidity factors for each Class I area from Tables 7-9 in FLAG (2010). 

The ∆dv was calculated for each grid cell that overlaps a Class I or sensitive Class II area by 5% or 

more for each day of the annual CAMx run. The highest ∆dv across all grid cells overlapping a 

Class I or sensitive Class II area by at least 5% was selected to represent the daily value at that 

Class I/II area. Visibility impacts due to emissions from each source group that exceed the 0.5 and 

1.0 Δdv thresholds are noted. 

Cumulative Visibility Impacts

The cumulative visibility impacts of the 2017-2022 GOM Multisale EIS, from which this 

Supplemental EIS tiers, were assessed following the recommendations from the U.S. Dept. of the 

Interior’s Fish and Wildlife Service (FWS) and NPS (USDOI, FWS and USDOI, NPS, official 

communication, 2012). This approach is based on an abbreviated regional haze rule method that 

estimates the future year visibility at Class I and sensitive Class II areas for the average of the Worst 

20% (W20%) and Best 20% (B20%) visibility days with and without the effects of the source group 

emissions on visibility impairment. The cumulative visibility impacts used CAMx model output from 

the 2012 Base Year and 2017 Future Year emissions scenarios in conjunction with monitoring data 

to produce cumulative visibility impacts at each Class I and sensitive Class II area. The USEPA’s 

Modeled Attainment Test Software (MATS19) was used to make the 2017 visibility projections for the 

W20% and B20% days. The basic steps in the recommended cumulative visibility method are as 

follows (USDOI, FWS and USDOI, NPS, official communication, 2012):

(1) Calculate the observed average 2012 current year cumulative visibility impact 

using the haze index (HI, in deciviews) at each Class I area using 

representative IMPROVE measurement data to determine the 20% of days with 

the worst and 20% of days with the best visibility. The MATS is designed to use 

5 years of monitoring data centered on the base case year, which for 2012 

would include 2010-2014. However, MATS only includes IMPROVE monitoring 

data through 2012, so the 2008-2012 5-year period was used to define the 

visibility baseline conditions in the MATS visibility projections. 

(2) Estimate the relative response factors (RRFs) for each component of PM2.5 and 

for coarse mass (CM) corresponding to the new IMPROVE visibility algorithm 

using the CAMx 2012 and 2017 model output. The RRFs are based on the 

 

19 http://www.epa.gov/ttn/scram/modelingapps_mats.htm
Air Quality: Cumulative and Visibility Impacts D-79

average concentrations across a 3 x 3 array of 4-km grid cells centered on the 

IMPROVE monitoring site location.

(3) Using the RRFs and ambient data, calculate 2017 future year daily 

concentration data for the B20% and W20% days using the CAMx 2012 base 

case and 2017 standard model concentration estimates and PSAT source 

apportionment modeling results two ways: 

(a) 2017 Total Emissions: Use total 2017 CAMx concentration results due to all 

emissions;

(b) 2017 No Cumulative Emissions: Use PSAT source apportionment results to 

eliminate contributions of PM concentrations associated with each source 

group. 

(4) Use the information in Step 3 to calculate the average 2017 visibility for the 20% 

Best and 20% Worst visibility days and the 2017 emissions.

5. Assess the average differences in cumulative visibility impacts for each source 

group and also compare with the future and current observed Baseline visibility 

conditions.

Because of the need for IMPROVE observations, monitoring data from nearby Class I areas 

were used to represent areas without any IMPROVE monitors. 

D.6.2.3.2 Sulfur and Nitrogen Deposition

The CAMx-predicted wet and dry fluxes of sulfur- and nitrogen-containing species were 

processed to estimate total annual sulfur and nitrogen deposition values at each Class I and 

sensitive Class II area. The maximum annual sulfur and nitrogen deposition values from any grid 

cell that intersects a Class I receptor area was used to represent deposition for that area, in addition 

to the average annual deposition values of all grid cells that represent a Class I receptor area. 

Although the convention in the past has been to report just the maximum deposition in any receptor 

in a Class I/II area, since deposition relates to the total amount deposited across an entire 

watershed, the average metric may be considered a more relevant parameter for evaluating 

potential environmental effects. Maximum and average predicted sulfur and nitrogen deposition 

impacts are reported separately for each source group. 

Nitrogen deposition impacts were calculated by taking the sum of the nitrogen contained in 

the fluxes of all nitrogen species modeled by the CAMx PSAT source apportionment tool. The 

CAMx species used in the nitrogen deposition flux calculation are reactive gaseous nitrate species, 

RGN (NO, NO2, NO3 radical, HONO, N2O5), TPN (PAN, PANX, PNA), organic nitrates (NTR), 

particulate nitrate formed from primary emissions plus secondarily formed particulate nitrate (NO3), 

gaseous nitric acid (HNO3), gaseous ammonia (NH3), and particulate ammonium (NH4). The CAMx 

species used in the sulfur deposition calculation are primarily sulfur dioxide emissions (SO2) and 

particulate sulfate ion from primary emissions plus secondarily formed sulfate (SO4). 
D-80 2018 Gulf of Mexico Supplemental EIS

FLAG (2010) recommends that applicable sources assess impacts of nitrogen and sulfur 

deposition at Class I areas. This guidance recognizes the importance of establishing critical 

deposition loading values (“critical loads”) for each specific Class I area as these critical loads are 

completely dependent on local atmospheric, aquatic, and terrestrial conditions and chemistry. 

Critical load thresholds are essentially a level of atmospheric pollutant deposition below which 

negative ecosystem effects are not likely to occur. FLAG (2010) does not include any critical load 

levels for specific Class I areas and refers to site-specific critical load information on FLM websites 

for each area of concern. This guidance does, however recommend the use of deposition analysis 

thresholds (DATs 20) developed by the NPS and FWS. The DATs represent screening level values 

for nitrogen and sulfur deposition for individual projects with deposition impacts below the DATS 

considered negligible. A DAT of 0.005 kilograms per hectare per year (kg/ha/yr) for both nitrogen 

and sulfur deposition has been established for both nitrogen and sulfur deposition in western Class I 

areas. A DAT of 0.01 kg/ha/yr has been established for both nitrogen and sulfur deposition for areas 

in the eastern U.S. As a screening analysis, results for Source Group B (new platforms and 

associated support vessels and aircraft associated with the 2017-2022 GOM Multisale EIS scenario, 

from which this Supplemental EIS tiers) were compared to the DATs. Comparison of deposition 

impacts from cumulative sources to the DAT is not appropriate.

For the 2012 base case and the combined source groups and total 2012 and future year 

emissions, the annual nitrogen and sulfur deposition were compared against critical load values 

established by the Federal Land Management agencies. Published nitrogen critical load values for 

areas managed by the NPS21 include minimum critical loads of 3 kg/ha/yr at the Gulf Islands 

National Seashore, as well as at Guadalupe Mountains and Big Bend, and 5 kg/ha/yr at Padre Island

National Seashore and Everglades National Park. These values represent the minimum of the 

critical loads for each biological community type (i.e., forests, herbaceous plants, lichen, mycorrhizal 

fungi, and nitrate leaching). Nitrogen and sulfur critical load values for areas managed by the U.S. 

Dept. of Agriculture’s Forest Service (USFS) include 5 kg/ha/yr at Bradwell Bay, Cohutta, Sipsey,

Caney Creek and Upper Buffalo. The 5 kg/ha/yr critical load value for these areas applies 

separately to nitrogen and to sulfur deposition. As no separate critical load values for sulfur are 

available from the NPS areas, the sulfur critical loads were set equal to the values for nitrogen. No 

published critical load values were found for areas managed by the FWS; critical loads for these 

areas were set by reference to the NPS and USFS critical loads based on proximity and similarity of 

ecoregion types. Using this approach, both nitrogen and sulfur critical loads for the Breton 

Wilderness, Breton National Wildlife Refuge, St. Marks, Chassahowitzka, Okefenoke, and Wolf 

Island were set at 3 kg/ha/yr based on the Gulf Islands National Seashore value for Eastern 

Temperate Forests. The values for Wichita Mountains was set at 5 kg/ha/yr based on the NPS’ 

Chickasaw National Recreation Area Great Plains ecoregion value.

 

20 http://www.nature.nps.gov/air/Pubs/pdf/flag/nsDATGuidance.pdf

21 http://www.nature.nps.gov/air/Studies/criticalloads/Ecoregions/index.cfm
Air Quality: Cumulative and Visibility Impacts D-81

D.6.2.4 PSD Increments

The maximum contribution of new oil and gas emissions in the Gulf of Mexico under the 

2017-2022 GOM Multisale EIS scenario were reported for each Class I and sensitive Class II area 

and were compared against the PSD increments given in Table D-14. Under the Clean Air Act, a 

PSD increment consumption analysis requires major stationary sources subject to PSD review to 

demonstrate that emission increases from the proposed source, in conjunction with all other 

emissions increases or reductions in the impacted area (typically within 50 kilometers), will not cause 

or contribute to concentrations of air pollutants that exceed PSD increments. The PSD increments 

have been established for NOx, SO2, and PM in Class I and Class II areas. Actions to be authorized 

by BOEM under the 2017-2022 GOM Multisale EIS scenario do not typically constitute major 

stationary sources and do not typically trigger PSD permits or review. However, a comparison of 

ambient concentrations from an accumulation of new oil and gas sources within the entire study area 

to PSD increments at specific Class I and Class II areas is included in this analysis for information 

purposes. This information is presented to aid State agencies in tracking the potential minor source 

increment consumption and to aid Federal Land Managers or Tribal governments responsible for 

protecting air resources in Class I areas. This Supplemental EIS tiers from the 2017-2022 GOM 

Multisale EIS and uses the scenario and alternatives analyzed in the 2017-2022 GOM Multisale EIS.

D.7 AIR RESOURCE ASSESSMENT RESULTS

D.7.1 NAAQS Impacts

Future year CAMx modeling results were used to examine future air quality relative to the 

NAAQS and the individual contributions of each source group relative to the NAAQS. For the ozone 

and PM2.5 NAAQS, comparisons are presented both in terms of the “absolute” CAMx results and in 

terms of using the base case and future year CAMx results in a relative sense to scale the observed 

base (“current” or “base”) year design value (DVC or DVB) to obtain the projected future year design 

value (DVF) as recommended by the USEPA’s modeling guideline (USEPA, 2007 and 2014) and as 

described in Section D.6.2.2.

D.7.1.1 Ozone NAAQS Analysis using Relative Model Results

The USEPA’s Model Attainment Test Software (MATS) was used to make future year ozone 

DVF projections using the CAMx 2012 base case and future year scenario modeling results as 

described in Section D.6.2.2. The MATS was used to make DVF projections at the locations of 

ambient air monitoring sites as well as throughout the 4-km modeling domain using the MATS 

Unmonitored Area Analysis (UAA) procedures.
D-82 2018 Gulf of Mexico Supplemental EIS

D.7.1.1.1 Monitored Ozone Design Value Projections using MATS

The MATS results for the future year ozone design values (DVFs) at individual ambient air 

monitoring sites in the 4-km domain are listed in Tables D-17 and D-18. Updated MATS data files 

containing ozone design values up through 2014 were obtained from the USEPA.22 To make future 

year projections, MATS starts with a current year design value (DVC) that is based on an average of 

three ozone design values from the 5-year period centered on the base case modeling year, which

was 2012 for this analysis. Thus, MATS DVCs are based on ozone design values from the 

2010-2012, 2011-2013, and 2012-2014 periods. The MATS makes ozone DVF projections using the 

changes in daily maximum 8-hour ozone concentrations near (3 x 3 array of 4-km grid cells) a 

monitor using the ratio of future year to current year modeling results to scale the observed DVCs. 

These modeled derived scaling factors are called Relative Response Factors (RRFs; DVF = DVC x 

RRF). The RRFs are based on the 10 highest modeled ozone days above a threshold ozone 

concentration. A lower bound observed ozone threshold value of 50 ppb was used in MATS.

Of the 74 monitors with valid DVCs as calculated by MATS, 39 have DVCs exceeding the 

NAAQS (70 ppb). The DVFs are less than DVCs at all 74 sites. A total of 22 sites have predicted 

DVFs exceeding the MATS, all of which are among the sites with DVCs above the NAAQS. 

Contributions of each source group to the DVFs were calculated as the difference between 

the DVF calculated from the CAMx results with all sources included and a revised DVF calculated 

after first subtracting out the individual hourly contributions of each source group in the future year 

model run. These source group contributions are tabulated in Table D-18. The maximum 

contribution from Source Group A (new platforms associated with the 2017-2022 GOM Multisale EIS 

scenario, from which this Supplemental EIS tiers) is 0.5 ppb. The maximum contribution from 

Source Group B (new platforms and support vessels and helicopters associated with the 2017-2022 

GOM Multisale EIS scenario, from which this Supplemental EIS tiers) is 5.1 ppb.

Five sites in Texas and one in Louisiana were identified where the contribution of the new 

platforms and associated support vessels and aircraft under the 2017-2022 GOM Multisale EIS 

(from which this Supplemental EIS tiers) scenario (Source Group B) to the DVF was enough to push 

the DVF from just below the 70-ppb NAAQS (with Source Group B contributions removed) to just 

above the NAAQS when all sources were included (Table D-19). In each case, the “contribution” 

from Source Group B is less than 5 ppb. At each of these sites, the DVCs are all also greater than 

70 ppb as noted above. At the Galveston, Texas, monitor, the 0.3-ppb contribution of Source Group 

A (new platforms) alone was sufficient to bump the future year design value from just below the 

NAAQS to just above the NAAQS (recall comparisons to the 70 ppb NAAQS are made after 

truncating design values to the nearest ppb). 

 

22 https://www3.epa.gov/scram001/modelingapps_mats.htm
Air Quality: Cumulative and Visibility Impacts D-83

For the ozone impacts assessment, please note that the states will not designate under the 

2015 ozone standard of 70 ppb until 2017, with the earliest attainment date of March 2021 for 

marginal areas. For this impacts assessment, the non-OCS source emissions were based on the 

USEPA’s 2017 emission projections, with a future modeled year of 2017 and compared to the 

70-ppb standard. This assessment is assuming the standard will be attained way before the actual 

attainment date, but it wanted to give maximum OCS oil and gas impacts under the new 70 ppb 

ozone standard. 

Table D-17. Current Year (DVC) and Future Year (DVF) Ozone Design Values at Ambient Air Monitoring 

Sites within the 4-km Modeling Domain from MATS.

Site ID Site Name State County DVC DVF

10030010 FAIRHOPE HIGH SCHOOL, FAIRHOPE, 

ALABAMA AL Baldwin County 68 66.2

10970003 CHICKASAW, MOBILE CO., ALABAMA AL Mobile County 67.3 64.4

10972005 BAY RD. ,MOBILE AL. AL Mobile County 72 66.5

120330004 ELLYSON INDUSTRIAL PARK-COPTER 

ROAD FL Escambia County 67.7 65.1

120330018 NAS PENSACOLA FL Escambia County 70.7 68.1

120910002 720 Lovejoy Rd FL Okaloosa County 65 62.9

121130015 1500 WOODLAWN WAY FL Santa Rosa County 69.3 67.4

220050004 11153 Kling Road LA Ascension Parish 71.3 67.8

220190002 HIGHWAY 27 AND HIGHWAY 108 LA Calcasieu Parish 70.7 68.9

220190008 2646 John Stine Road LA Calcasieu Parish 66.7 64.7

220190009 2284 Paul Bellow Road LA Calcasieu Parish 70 67.3

220330003 EAST END OF ASTER LANE LA East Baton Rouge 

Parish 75.3 71.3

220330009 1061-A Leesville Ave LA East Baton Rouge 

Parish 72.3 68.3

220330013 11245 Port Hudson-Pride Rd. Zachary, La LA East Baton Rouge 

Parish 69 65.1

220470009 65180 Belleview Road LA Iberville Parish 70.3 64.6

220470012 HIGHWAY 171, CARVILLE LA Iberville Parish 73.3 68.6

220511001 West Temple Pl LA Jefferson Parish 71.3 68.4

220550007 646 Cajundome LA Lafayette Parish 69.7 67.2

220570004 Nicholls University Farm Highway 1 LA Lafourche Parish 71 65.7

220630002 Highway 16, French Settlement LA Livingston Parish 72.3 68.6

220710012 Corner of Florida Ave & Orleans Ave LA Orleans Parish 68.3 66.5

220770001 TED DAVIS RESIDENCE. HIGHWAY 415 LA Pointe Coupee Parish 74 68.2

220870004 4101 Mistrot Dr. Meraux, LA 70075 LA St. Bernard Parish 68 64.4

220890003 1 RIVER PARK DRIVE LA St. Charles Parish 67.7 65.2

220930002 ST. JAMES COURTHOUSE, HWY 44 @ 

CANAPELLA LA St. James Parish 66.3 62.7

220950002 Anthony F. Monica Street LA St. John the Baptist 

Parish 72 69.3

221030002 1421 Hwy 22 W, Madison Ville, LA 70447 LA St. Tammany Parish 72.3 68.7
D-84 2018 Gulf of Mexico Supplemental EIS

Site ID Site Name State County DVC DVF

221210001 1005 Northwest Drive, Port Allen LA West Baton Rouge 

Parish 68 63.8

280450003 400 Baltic St MS Hancock County 66.3 63.4

280470008 47 Maple Street MS Harrison County 70.3 67

280590006 Hospital Road at Co. Health Dept. MS Jackson County 71.3 69.2

480271047 1605 Stone Tree Drive TX Bell County 73.7 71

80.3 78

68.7 66.3

480391004 4503 CROIX PKWY TX Brazoria County 85 81.9

480391016 109 B BRAZORIA HWY 332 WEST TX Brazoria County 69.3 66.8

480610006 344 PORTER DRIVE TX Cameron County 60.7 59.2

69.3 66.6

481671034 9511 AVENUE V 1⁄2 TX Galveston County 75.3 71.2

482010024 4510 1/2 ALDINE MAIL RD. TX Harris County 76.7 75.1

482010026 1405 SHELDON ROAD TX Harris County 73 71.2

482010029 16822 KITZMAN TX Harris County 80 76.3

482010046 7330 1/2 NORTH WAYSIDE TX Harris County 73.7 71.6

482010047 4401 1/2 LANG RD. TX Harris County 77 74.8

482010051 13826 1/2 CROQUET TX Harris County 78.7 76.3

482010055 6400 BISSONNET STREET TX Harris County 78.7 77.3

482010062 9726 1/2 MONROE TX Harris County 76.7 74.4

482010066 3333 1/2 HWY 6 SOUTH TX Harris County 77.7 75.2

482010070 5425 POLK AVE., SUITE H TX Harris County 75 73.5

482010416 7421 PARK PLACE BLVD TX Harris County 77.3 74.8

482011015 1001 B LYNCHBURG ROAD TX Harris County 71 68.5

482011034 1262 1/2 MAE DRIVE TX Harris County 78 76.1

482011035 9525 CLINTON DR TX Harris County 74.7 72.5

482011039 4514 1/2 DURANT ST. TX Harris County 78.3 75.5

482011050 4522 PARK RD. TX Harris County 76.3 74

482151048 325 Golf Course Road TX Hidalgo County 60 58.1

482450009 1086 Vermont Avenue TX Jefferson County 71.7 68.3

482450011 800 EL VISTA ROAD & 53RD STREET TX Jefferson County 74 70.5

482450022 12552 SECOND ST. TX Jefferson County 70.3 66.7

482450101 6019 MECHANIC TX Jefferson County 75 72.3

482450102 SETRPC 43 Jefferson Co Airport TX Jefferson County 67 64.4

482450628 UNAVAILABLE TX Jefferson County 69.3 66.4

482451035 Seattle Street TX Jefferson County 69.3 66.9

483091037 4472 MAZANEC RD TX McLennan County 71.7 69.1

483390078 9472 A HWY 1484 TX Montgomery County 78 74.7

483491051 Corsicana Airport TX Navarro County 70 68.2

483550025 CORPUS CHRISTI STATE SCHOOL, 

AIRPORT RD TX Nueces County 69.3 68.2

483550026 9860 LA BRANCH TX Nueces County 68.3 66.2

483611001 2700 AUSTIN AVE TX Orange County 69.3 66.5
Air Quality: Cumulative and Visibility Impacts D-85

Site ID Site Name State County DVC DVF

483611100 INTERSECTION OF TX HWYS 62 AND 

12 TX Orange County 68 65.4

484530014 3724 NORTH HILLS DR, AUSTIN, TX 

78758 TX Travis County 71.3 67.7

484530020 12200 LIME CREEK RD. TX Travis County 71.7 68.3

484690003 106 MOCKINGBIRD LANE TX Victoria County 66.3 64.2

Table D-18. Ozone Current (DVC) and Future Year (DVF) Design Values and Reduction in DVF with 

Contributions from Individual Source Groups Removed.

Site ID State County DVC DVF

Change in DVF with Source Group 

Removed

A B C D E

10030010 AL Baldwin County 68 66.2 0.3 4.7 7.6 10.2 42.6

10970003 AL Mobile County 67.3 64.4 0.1 2.3 4.2 5.4 40.4

10972005 AL Mobile County 72 66.5 0.1 5.1 6.5 7.9 44.7

120330004 FL Escambia County 67.7 65.1 0.3 1.7 5.5 7.4 35.3

120330018 FL Escambia County 70.7 68.1 0.4 2.6 7.8 10.9 37.8

120910002 FL Okaloosa County 65 62.9 0.3 1.9 6.8 9.5 33.6

121130015 FL Santa Rosa County 69.3 67.4 0.5 2.6 9.3 12.7 37.5

220050004 LA Ascension Parish 71.3 67.8 0.1 0.7 2.3 3.1 43.6

220190002 LA Calcasieu Parish 70.7 68.9 0.3 2 5.6 8.3 40.2

220190008 LA Calcasieu Parish 66.7 64.7 0.3 1.7 4.9 7.4 37.6

220190009 LA Calcasieu Parish 70 67.3 0.2 1.5 4.2 6.1 39.7

220330003 LA East Baton Rouge Parish 75.3 71.3 0.1 0.7 2.9 4 45.3

220330009 LA East Baton Rouge Parish 72.3 68.3 0.1 0.7 2.6 3.7 43.3

220330013 LA East Baton Rouge Parish 69 65.1 0.2 1 3.2 4.3 37.7

220470009 LA Iberville Parish 70.3 64.6 0 0.2 0.7 1.1 41.2

220470012 LA Iberville Parish 73.3 68.6 0 0.4 1.5 2.3 45.7

220511001 LA Jefferson Parish 71.3 68.4 0.2 1.1 5.2 6.6 45

220550007 LA Lafayette Parish 69.7 67.2 0.1 1.4 3.9 5.6 41.5

220570004 LA Lafourche Parish 71 65.7 0.1 0.5 1.7 2.4 40.9

220630002 LA Livingston Parish 72.3 68.6 0.2 1.1 4.4 5.9 44.3

220710012 LA Orleans Parish 68.3 66.5 0.3 1.2 5.6 7.2 42

220770001 LA Pointe Coupee Parish 74 68.2 0 0.5 2 3 43.7

220870004 LA St. Bernard Parish 68 64.4 0.3 1.4 5.5 7.2 41.1

220890003 LA St. Charles Parish 67.7 65.2 0.1 0.6 2.5 3.3 44.7

220930002 LA St. James Parish 66.3 62.7 0.1 0.5 2.1 2.8 39.3

220950002 LA St. John the Baptist 

Parish 72 69.3 0.2 0.9 3.5 4.6 45

221030002 LA St. Tammany Parish 72.3 68.7 0.2 1.1 5 6.3 42.9

221210001 LA West Baton Rouge 

Parish 68 63.8 0 0.5 2.1 2.9 40

280450003 MS Hancock County 66.3 63.4 0.3 1.6 5.3 7.1 39.9

280470008 MS Harrison County 70.3 67 0.3 1.7 5.4 7.3 42.8

280590006 MS Jackson County 71.3 69.2 0.4 2.7 6 8.9 44.9
D-86 2018 Gulf of Mexico Supplemental EIS

Site ID State County DVC DVF

Change in DVF with Source Group 

Removed

A B C D E

480271047 TX Bell County 73.7 71 0 0.3 0.9 1.2 30.9

80.3 78 0 0.3 0.9 1.3 37.4

68.7 66.3 0.1 0.2 0.4 0.5 33.3

480391004 TX Brazoria County 85 81.9 0.1 0.7 2.2 3.1 49.5

480391016 TX Brazoria County 69.3 66.8 0.2 1.3 3.4 4.8 37.4

480610006 TX Cameron County 60.7 59.2 0.2 1.3 2.4 3.3 29.2

69.3 66.6 0.1 0.2 0.3 0.5 29.9

481671034 TX Galveston County 75.3 71.2 0.3 3.6 9.8 16.6 46.6

482010024 TX Harris County 76.7 75.1 0.2 1.5 4 5.8 44.1

482010026 TX Harris County 73 71.2 0.2 1.6 4.1 5.9 42.1

482010029 TX Harris County 80 76.3 0.2 1.1 3.3 4.8 48

482010046 TX Harris County 73.7 71.6 0.2 1.3 3.4 4.9 41.8

482010047 TX Harris County 77 74.8 0.2 1 3 4.4 46

482010051 TX Harris County 78.7 76.3 0.1 0.6 1.8 2.6 47.5

482010055 TX Harris County 78.7 77.3 0.1 0.8 2.4 3.3 46.9

482010062 TX Harris County 76.7 74.4 0.2 1.1 3.1 4.5 45.3

482010066 TX Harris County 77.7 75.2 0.1 0.7 2.2 3.1 46.6

482010070 TX Harris County 75 73.5 0.2 1.3 3.4 5 41.6

482010416 TX Harris County 77.3 74.8 0.1 1.2 3.1 4.6 44.4

482011015 TX Harris County 71 68.5 0.2 1.3 3.7 5.3 39.1

482011034 TX Harris County 78 76.1 0.3 1.7 4.1 5.9 44.3

482011035 TX Harris County 74.7 72.5 0.2 1.3 3.3 5 41.7

482011039 TX Harris County 78.3 75.5 0.2 1.3 3.4 5.1 42.8

482011050 TX Harris County 76.3 74 0.3 2.2 5.8 9.1 43.5

0.1 0.6 1.5 2.2 27.5

482151048 TX Hidalgo County 60 58.1 0.1 0.6 1.4 2 24.3

482450009 TX Jefferson County 71.7 68.3 0.1 0.7 2 2.9 42.2

482450011 TX Jefferson County 74 70.5 0.2 1.9 4.9 7.2 43.9

482450022 TX Jefferson County 70.3 66.7 0.1 0.8 2.4 3.5 40.3

482450101 TX Jefferson County 75 72.3 0.3 3 8.2 12.4 45.9

482450102 TX Jefferson County 67 64.4 0.2 1.3 4.1 6 40

482450628 TX Jefferson County 69.3 66.4 0.2 2 5.3 7.8 41.8

482451035 TX Jefferson County 69.3 66.9 0.2 1.5 4.5 6.7 41.9

483091037 TX McLennan County 71.7 69.1 0 0.2 0.5 0.7 31.3

483390078 TX Montgomery County 78 74.7 0.2 1 3.1 4.5 45.8

483491051 TX Navarro County 70 68.2 0.1 0.2 0.6 0.8 33.5

483550025 TX Nueces County 69.3 68.2 0.3 1.9 5.4 7.4 35

483550026 TX Nueces County 68.3 66.2 0.3 1.3 3.6 4.9 32.7

483611001 TX Orange County 69.3 66.5 0.1 1.4 4.8 6.9 41.3

483611100 TX Orange County 68 65.4 0.1 1.5 4.6 6.9 40

484530014 TX Travis County 71.3 67.7 0 0.2 0.9 1.3 37.5

484530020 TX Travis County 71.7 68.3 0.1 0.3 1 1.4 35.8

484690003 TX Victoria County 66.3 64.2 0.2 1 3 4.2 32.6
Air Quality: Cumulative and Visibility Impacts D-87

Table D-19. MATS Ozone Design Value Results for All Monitoring Sites Where Exclusion of 

Contributions from Source Group A or B is Sufficient to Reduce the Predicted Future Design 

Value (DVF) from Above the NAAQS to Below the NAAQS (all values in ppb).

Site ID Location State DVC1 DVF2 DVF_A3 DVF –

DVF_A DVF_B3 DVF –DVF_B

220330003 East Baton 

Rouge Parish LA 75.3 71.3 71.2 0.1 70.6 0.7

480271047 Bell County TX 73.7 71.0 71.0 0.0 70.7 0.3

481671034 Galveston TX 75.3 71.2 70.9 0.3 69.1 4.9

482010026 Houston TX 73 71.2 71.0 0.2 69.6 1.6

482010046 Houston TX 73.7 71.6 71.4 0.2 70.3 1.3

482450101 Port Arthur TX 75 72.3 72.0 0.3 69.3 3.0

1 The MATS base period ozone design value (ppb) representing combined contributions of all sources.

2 The MATS future year ozone design value (ppb) representing combined contributions of all sources. 3 The MATS future year ozone design value (ppb) calculated after removing source apportionment 

contributions of Source Group A or B. 

Figure D-40 displays the MATS Unmonitored Area Analysis (UAA) results, which were 

generated using the observed ozone data in MATS and the base year and future year scenario 

CAMx results. The MATS UAA spatially interpolates the DVCs obtained from observations across 

the modeling domain and then calculates the DVF for each model grid cell by multiplying the 

interpolated DVC by the RRF value (i.e., the ratio of the modeled future year to base year design 

values) in each grid cell. Future year design values calculated using the MATS UAA procedure are 

lower than base year design values throughout most of the 4-km modeling domain with the 

exception of a maximum 1.6-ppb increase of less than 3 ppb off the Louisiana coast.
D-88 2018 Gulf of Mexico Supplemental EIS

Figure D-40. Base Scenario Ozone Design Values (DVC, top left), Future Year Ozone Design Values 

(DVF, top right) and Their Differences (DVF – DVC; bottom) Calculated Using the MATS 

UAA Tool.

D.7.1.1.2 Ozone MATS Unmonitored Area Analysis

The MATS UAA DVF values calculated after first removing the hourly contributions from 

Source Groups A (new platforms), B (new platforms and associated support vessels and aircraft), 

and D (all Gulf of Mexico sources) are shown in the left column of Figure D-41. The contributions of 

Source Groups A, B, and D calculated as the difference between these DVF values and the DVF 

values from all sources (as shown in the upper right-hand corner of Figure D-40) are shown in the 

right column of Figure D-41. Source Group A contributions are centered in the Gulf of Mexico 

offshore of Louisiana, with a peak impact of 2.2 ppb; maximum impacts from the State seaward 

boundaries inland are in the 1- to 1.2-ppb range along the coast of Cameron Parish. For Source 

Group B, the maximum contribution (10.8 ppb) is in approximately the same location, but the support 

vessel and helicopter activities result in greater impacts landward of the State seaward boundary, 

with maximum contributions in the 6- to 7-ppb range.
Air Quality: Cumulative and Visibility Impacts D-89

Source 

Group1

DVF with Source Group Contribution 

Removed Source Group Contribution2

A 

B 

D 

1 As defined in Table D-14. 2 Source group contributions are calculated by subtracting the DVF values calculated after removing 

the hourly source group contributions from the DVF values calculated when all sources are 

included.

Figure D-41. MATS UAA Future Year Ozone Design Values (DFV) Calculated After First Removing the 

Hourly Contributions from a Source Group (left column) and the Corresponding 

Contributions of the Source Group to DVF (right column) Calculated by Subtracting the 

DVFs Shown in the Left-hand Column from the “All Sources” DVF Shown in the Top 

Right-hand Corner of Figure D-40. Top row – source group B; middle row – source 

group D. 
D-90 2018 Gulf of Mexico Supplemental EIS

D.7.1.2 Ozone NAAQS Analysis Using Absolute Modeling Results

The CAMx source apportionment absolute modeling results from the future year scenario are 

analyzed and compared with the ozone NAAQS in this section. The ozone NAAQS is defined as the 

3-year average of the 4th highest maximum daily average 8-hour (MDA8) ozone concentration. Since 

only one calendar year of modeling results are available for the base year and future year scenarios, 

the future year 4th highest MDA8 ozone concentration is used as a pseudo-NAAQS comparison 

metric. 

Modeled 4th highest MDA8 values in each model grid cell for the base and future year 

scenarios and the corresponding differences are shown in Figure D-42. Similar to the MATS results 

presented in Figure D-40, the 4th highest MDA8 is lower under the future year scenario throughout 

most of the 4-km domain, with isolated areas of increases of less than 4 ppb located off the coasts of 

Louisiana and Texas and onshore in Cameron Parish, Louisiana. 

Figure D-42. Modeled 4th Highest MDA8 Ozone for the Base Year (upper left) and Future Year (upper 

right) Scenarios and Their Differences (bottom center). 
Air Quality: Cumulative and Visibility Impacts D-91

Contributions of each source group to the all sources future year 4th highest MDA8 values 

shown in the upper right-hand panel of Figure D-42 are shown in Figures D-43 and D-44. These 

contributions are matched in time to the all sources 4th highest MDA8 values; contributions may be 

different during other periods with elevated MDA8 values. As shown in Figure D-43, new platform 

sources under the 2017-2022 GOM Multisale EIS (from which this Supplemental EIS tiers) scenario 

(Source Group A) are estimated to contribute as much as 7.4 ppb to design values out over the Gulf

of Mexico. Within the states out to the State Seaward Boundary (SSB), the contributions range from 

near zero to approximately 3 ppb, with the maximum contributions occurring along the coast of 

Cameron Parish, Louisiana. Contributions increase by about 10 ppb when contributions from 

support vessels and helicopters associated with the 2017-2022 GOM Multisale EIS scenario, from 

which this Supplemental EIS tiers, are added in (Source Group B). Also, adding in all existing 

platforms and support vessels and helicopters (Source Group C) raises the maximum contribution 

out over the Gulf of Mexico to nearly 38 ppb. Contributions landward of the SSB are generally below 

15 ppb but with some areas along the Louisiana coast reaching maximum contributions up to 

35 ppb. Adding in all other marine vessel activity in the Gulf of Mexico (Source Group D) only 

increases the contributions by a few ppb. The addition of land-based and Mexican and Canadian 

anthropogenic sources (Source Group E) results in source contributions that are typically about 

30 ppb higher than the contributions from Gulf of Mexico sources alone (Source Group D). 

Contributions over the land areas are higher than for Source Group D although the highest 

contributions remain out over the Gulf of Mexico where biogenic emissions have minimal influence. 

In other words, to the extent that elevated ozone levels are predicted over the Gulf of Mexico, they 

are nearly entirely attributable to anthropogenic sources. 

Contributions from natural sources (including biogenics and fires) and non-U.S. emissions, 

including 12-km domain boundary conditions (Source Group F), are shown in the left panel of 

Figure D-44; contributions from just the boundary conditions (BCs) are shown in the right panel. 

These results show an area south of Galveston where ozone design values were almost entirely 

driven by U.S. or Mexican anthropogenic BCs; however, over the rest of the Gulf of Mexico, 

including the near coastal areas, contributions are generally between 20 and 30 ppb and are 

overwhelmingly attributable to the BCs. Higher contributions are seen inland where biogenic 

sources play a larger role in ozone formation.
D-92 2018 Gulf of Mexico Supplemental EIS

Figure D-43. Contributions of Source Groups A (top left), B (top right), C (middle left), D (middle right), 

and E (bottom) to Future Year All-sources 4th Highest MDA8 (note different color scales in 

each panel).
Air Quality: Cumulative and Visibility Impacts D-93

Figure D-44. Contributions from (left) Source Group F (natural and non-U.S. emission sources 

including boundary conditions) and (right) Boundary Conditions Only, to Future 

Year All-sources 4th Highest MDA8. 

D.7.1.3 PM2.5 NAAQS Analysis using Relative Model Results

There are two PM2.5 NAAQS, one for 24-hour averaging time that is expressed as a 3-year 

average of the annual 98th percentile in a year with a threshold of 35 μg/m3 and an annual average 

over 3 years with a threshold of 12 μg/m3

. With 1 year of complete everyday modeling, the annual 

98th percentile will correspond to the 8th highest 24-hour PM2.5 concentration in a year. 

Predictions of future year 24-hour and annual average PM2.5 design values were made 

based on the use of model results in a relative sense as was done for ozone design values in 

Section D.7.1.1. The MATS software was used to generate predicted future year design values 

(DVFs) from current (base year) design values (DVB or DVC). The MATS was configured to use 

ambient measurements of total PM2.5 for the period 2008-2012 to generate DVCs based on an 

average of three overlapping 3-year average DVs as recommended in the USEPA’s guidance 

(USEPA, 2014) and speciated PM2.5 monitoring data for the period 2010-2012 to generate the 

projected DVFs based on model predicted species RRFs. 

D.7.1.3.1 24-Hour PM2.5

As described for the ozone NAAQS analysis in Section D.7.1.1, the MATS was used to 

calculate DVFs for the 24-hour and annual PM2.5 NAAQS. Observational data for use in the MATS 

were provided by the USEPA23 for use in calculating the DVCs. For total PM2.5, observational data 

covered the period 2008-2012; for the speciated PM2.5 calculations, observational data covered the 

period 2010-2012.

 

23 https://www3.epa.gov/scram001/modelingapps_mats.htm
D-94 2018 Gulf of Mexico Supplemental EIS

Results of the MATS analysis are shown in Table D-20. All current and future year design 

values are below the 35 μg/m3 NAAQS, and the future year design values are projected to be lower 

than the current year design values at all sites. The reductions in the projected DVFs calculated 

after removing source contributions from each Source Group A, B, C, D, and E (i.e., DVF from 

Table D-20 minus DVF calculated with hourly source group contributions removed) are listed in 

Table D-21. The largest of the Source Group A, B, C, or D contributions calculated in this manner 

occur at the Bay Rd. monitor in Mobile County, Alabama. New platforms and associated support 

vessels and helicopters (Source Group B) are calculated to contribute 1.2 μg/m3 or 6.4% of the 

18.9 μg/m3 DVF at this location. 

Table D-20. Current Year (DVC) and Future Year (DVF) 24-Hour PM2.5 Design Values for Monitoring 

Sites in the 4-km Modeling Domain from MATS.

Site ID Site Name State County DVC DVF 

10030010 FAIRHOPE HIGH SCHOOL, FAIRHOPE, 

ALABAMA AL Baldwin County 19.5 17.7

10970003 CHICKASAW, MOBILE CO., ALABAMA AL Mobile County 19.1 17.2

10972005 BAY RD., MOBILE AL. AL Mobile County 20 18.9

120330004 ELLYSON INDUSTRIAL PARK-COPTER 

ROAD FL Escambia County 19.2 17.6

220190009 2284 Paul Bellow Road LA Calcasieu Parish 18.6 17

220190010 Common and East McNeese LA Calcasieu Parish 20.5 18.4

220330009 1061-A Leesville Ave LA East Baton Rouge 

Parish 21 19.2

220331001 Highway 964 LA East Baton Rouge 

Parish 16.7 14.2

220470005 St Gabriel Agricultural Exp. Station LA Iberville Parish 21 19.9

220470009 65180 Belleview Road LA Iberville Parish 18.6 17.5

220511001 West Temple Pl LA Jefferson Parish 18.7 17.1

220512001 Patriot St. and Allo St. LA Jefferson Parish 18.5 16.6

220550006 121 East Point Des Mouton LA Lafayette Parish 18.8 17.5

220550007 646 Cajundome LA Lafayette Parish 20.2 18.1

220790002 8105 Tom Bowman Drive LA Rapides Parish 19.6 17.7

220870007 24 E. CHALMETTE CIRCLE LA St. Bernard Parish 20.2 17.4

221050001 21549 Old Hammond Hwy, Hammond, LA 

70403 LA Tangipahoa Parish 18.8 17.2

221090001 4047 Highway 24 North Gray LA Terrebonne Parish 17.6 16.2

221210001 1005 Northwest Drive, Port Allen LA West Baton Rouge 

Parish 21.7 20.2

280010004 Natchez Municipal Water Works,

Brenham St. MS Adams County 20.3 17.7

280350004 205 Bay Street MS Forrest County 22.4 21

280450003 400 Baltic St. MS Hancock County 20 18.3

280470008 47 Maple Street MS Harrison County 18.3 16

280590006 Hospital Road at Co. Health Dept. MS Jackson County 20.8 19.6

280670002 26 Mason St. MS Jones County 23 21.7
Air Quality: Cumulative and Visibility Impacts D-95

Site ID Site Name State County DVC DVF 

480290059 14620 LAGUNA RD. TX Bexar County 21.4 20.9

480612004 LOT B 69 1⁄2 TX Cameron County 22.7 22.4

482010058 7210 1/2 BAYWAY DRIVE TX Harris County 20.8 20.2

482011035 9525 CLINTON DR TX Harris County 24 22.7

483550032 3810 HUISACHE STREET TX Nueces County 24.3 23.3

484530020 12200 LIME CREEK RD. TX Travis County 20.7 19.1

484530021 2600 B WEBBERVILLE RD. TX Travis County 21.8 20.5

Table D-21. 24-Hour PM2.5 Current (DVC) and Future Year (DVF) Design Values and Reduction in DVF 

with Contributions from Individual Source Groups Removed. 

Site ID State County DVC DVF

Change in DVF with Source Group 

Removed

A B C D E

10030010 AL Baldwin County 19.5 17.7 0.0 0.2 0.3 0.4 8.8

10970003 AL Mobile County 19.1 17.2 0.0 0.1 0.1 0.2 10.2

10972005 AL Mobile County 20 18.9 0.0 1.2 1.2 1.3 12.0

120330004 FL Escambia County 19.2 17.6 0.0 0.0 0.1 0.1 9.2

220190009 LA Calcasieu Parish 18.6 17 0.0 0.1 0.2 0.5 9.9

220190010 LA Calcasieu Parish 20.5 18.4 0.0 0.0 0.1 0.3 12.1

220330009 LA East Baton Rouge 

Parish 21 19.2 0.0 0.1 0.2 0.3 12.3

220331001 LA East Baton Rouge 

Parish 16.7 14.2 0.0 0.1 0.2 0.4 9.1

220470005 LA Iberville Parish 21 19.9 0.0 0.0 0.2 0.4 14.2

220470009 LA Iberville Parish 18.6 17.5 0.0 0.0 0.1 0.3 10.2

220511001 LA Jefferson Parish 18.7 17.1 0.0 0.0 0.2 0.3 12.0

220512001 LA Jefferson Parish 18.5 16.6 0.0 0.1 0.2 0.4 13.1

220550006 LA Lafayette Parish 18.8 17.5 0.1 0.2 0.5 1.0 12.1

220550007 LA Lafayette Parish 20.2 18.1 0.0 0.0 0.2 0.3 12.3

220790002 LA Rapides Parish 19.6 17.7 0.0 0.0 0.2 0.4 8.1

220870007 LA St. Bernard Parish 20.2 17.4 0.0 0.0 0.2 0.4 12.0

221050001 LA Tangipahoa Parish 18.8 17.2 0.1 0.1 0.3 0.5 9.1

221090001 LA Terrebonne Parish 17.6 16.2 0.0 0.1 0.3 0.4 10.8

221210001 LA West Baton Rouge 

Parish 21.7 20.2 0.0 0.0 0.2 0.3 13.8

280010004 MS Adams County 20.3 17.7 0.0 0.1 0.1 0.2 7.8

280350004 MS Forrest County 22.4 21 0.0 0.1 0.1 0.2 11.4

280450003 MS Hancock County 20 18.3 0.0 0.1 0.6 1.1 11.4

280470008 MS Harrison County 18.3 16 0.0 0.0 0.3 0.4 8.8

280590006 MS Jackson County 20.8 19.6 0.1 0.1 0.4 1.1 14.3

280670002 MS Jones County 23 21.7 0.0 0.1 0.1 0.1 11.0

480290059 TX Bexar County 21.4 20.9 0.0 0.0 0.0 0.0 11.8

480612004 TX Cameron County 22.7 22.4 0.0 0.7 0.7 0.8 5.4

482010058 TX Harris County 20.8 20.2 0.0 0.0 0.2 0.5 13.1
D-96 2018 Gulf of Mexico Supplemental EIS

Site ID State County DVC DVF

Change in DVF with Source Group 

Removed

A B C D E

482011035 TX Harris County 24 22.7 0.0 0.0 0.1 0.2 14.9

483550032 TX Nueces County 24.3 23.3 0.0 0.1 0.1 0.2 12.3

484530020 TX Travis County 20.7 19.1 0.0 0.0 0.0 0.1 9.4

484530021 TX Travis County 21.8 20.5 0.0 0.0 0.0 0.1 12.1

D.7.1.3.2 Annual Average PM2.5

The MATS projections of DVF for the annual average PM2.5 design values are shown in 

Table D-22. The only design value exceeding the 12 μg/m3 annual average NAAQS is the current 

year design value at the Clinton Dr. monitor in Houston, Texas. The projected future year design 

value at this location is below the NAAQS. Future year design values are projected to be less than 

the current year design values at all monitoring sites except for a 0.3 μg/m3 increase at the Hidalgo 

County monitoring site just west of Brownsville, Texas. 

Reductions in the projected annual average DVFs calculated after removing source 

contributions from each Source Group A, B, C, D, and E (i.e., DVF from Table D-22 minus DVF 

calculated with hourly source group contributions removed) are shown in Table D-23. The largest of 

the Source Group A, B, C, or D contributions calculated in this manner occur at the Bay Rd. monitor 

in Mobile County, Alabama. New platforms and associated support vessels and helicopters (Source 

Group B) are calculated to contribute 0.7 μg/m3 or 7.7% of the 9.1 μg/m3 DVF at this location. 

Source Group B contributions at the Clinton Dr. monitor are calculated to be less than 0.05 μg/m3

. 

Source Group B contributions at the Hidalgo County monitoring site are calculated to be 0.1 μg/m3

. 

Table D-22. Current (DVC) and Projected Future (DVF) Annual Average PM2.5 Design Values for 

Monitoring Sites in the 4-km Modeling Domain (highlighted values exceed the 12 μg/m3

NAAQS). 

Site ID Site Name State DVC DVF 

10030010 FAIRHOPE HIGH SCHOOL, FAIRHOPE, ALABAMA AL 9.8 9.1

10970003 CHICKASAW, MOBILE CO., ALABAMA AL 9.7 8.9

10972005 BAY RD., MOBILE AL. AL 9.2 9.1

120330004 ELLYSON INDUSTRIAL PARK-COPTER ROAD FL 8.9 8.3

220190009 2284 Paul Bellow Road LA 8.6 7.9

220190010 Common and East McNeese LA 9.1 8.5

220330009 1061-A Leesville Ave LA 10.3 9.6

220331001 Highway 964 LA 9.3 8.3

220470005 St Gabriel Agricultural Exp. Station LA 10.2 9.5

220470009 65180 Belleview Road LA 8.9 8.1

220511001 West Temple Pl LA 9 8.2

220512001 Patriot St. and Allo St. LA 9.2 8.3

220550006 121 East Point Des Mouton LA 8.9 8.2

220550007 646 Cajundome LA 9.1 8.4

220790002 8105 Tom Bowman Drive LA 8.8 8
Air Quality: Cumulative and Visibility Impacts D-97

Site ID Site Name State DVC DVF 

220870007 24 E. CHALMETTE CIRCLE LA 10.5 9.7

221050001 21549 Old Hammond Hwy, Hammond, LA 70403 LA 9 8.1

221090001 4047 Highway 24 North Gray LA 8.5 7.8

221210001 1005 Northwest Drive, Port Allen LA 10.8 10.1

280010004 Natchez Municipal Water Works Brenham St MS 10.2 9.3

280350004 205 Bay Street MS 11.7 10.9

280450003 400 Baltic St MS 9.9 9.1

280470008 47 Maple Street MS 9.6 8.7

280590006 Hospital Road at Co. Health Dept. MS 9.5 9

280670002 26 Mason St. MS 11.8 11.3

480290059 14620 LAGUNA RD. TX 9 8.8

480612004 LOT B 69 1⁄2 TX 11 10.9

482010058 7210 1/2 BAYWAY DRIVE TX 11.1 10.9

482011035 9525 CLINTON DR TX 12.4 11.6

482150043 2300 NORTH GLASSCOCK TX 10.4 10.7

483550032 3810 HUISACHE STREET TX 10.3 10

484530020 12200 LIME CREEK RD. TX 8.4 7.9

484530021 2600 B WEBBERVILLE RD. TX 10.2 9.8

Table D-23. Annual Average PM2.5 Future Year Design Values (DVF) and Change in DVF with 

Contributions from Individual Source Groups Removed (highlighted values exceed the 

12 μg/m3 NAAQS). 

Site ID State County DVC DVF 

Change in DVF with Source Group 

Removed

A B C D E

10030010 AL Baldwin County 9.8 9.1 0.0 0.1 0.2 0.3 5.5

10970003 AL Mobile County 9.7 8.9 0.0 0.1 0.1 0.2 6.2

10972005 AL Mobile County 9.2 9.1 0.0 0.7 0.8 0.9 6.1

120330004 FL Escambia County 8.9 8.3 0.0 0.1 0.1 0.2 5.2

220190009 LA Calcasieu Parish 8.6 7.9 0.0 0.1 0.2 0.4 5.0

220190010 LA Calcasieu Parish 9.1 8.5 0.0 0.0 0.2 0.4 6.3

220330009 LA East Baton Rouge 

Parish 10.3 9.6 0.0 0.1 0.2 0.3 7.2

220331001 LA East Baton Rouge 

Parish 9.3 8.3 0.0 0.0 0.1 0.2 6.0

220470005 LA Iberville Parish 10.2 9.5 0.0 0.0 0.1 0.2 7.4

220470009 LA Iberville Parish 8.9 8.1 0.0 0.0 0.1 0.3 5.5

220511001 LA Jefferson Parish 9 8.2 0.0 0.1 0.2 0.3 6.0

220512001 LA Jefferson Parish 9.2 8.3 0.0 0.0 0.1 0.2 6.6

220550006 LA Lafayette Parish 8.9 8.2 0.0 0.0 0.2 0.4 5.9

220550007 LA Lafayette Parish 9.1 8.4 0.0 0.1 0.2 0.4 6.1

220790002 LA Rapides Parish 8.8 8 0.0 0.0 0.1 0.2 4.7

220870007 LA St. Bernard Parish 10.5 9.7 0.0 0.1 0.2 0.3 7.3

221050001 LA Tangipahoa Parish 9 8.1 0.0 0.1 0.2 0.3 5.0

221090001 LA Terrebonne Parish 8.5 7.8 0.0 0.0 0.2 0.4 5.5
D-98 2018 Gulf of Mexico Supplemental EIS

Site ID State County DVC DVF 

Change in DVF with Source Group 

Removed

A B C D E

221210001 LA West Baton Rouge 

Parish 10.8 10.1 0.0 0.0 0.1 0.2 7.9

280010004 MS Adams County 10.2 9.3 0.0 0.0 0.1 0.2 5.4

280350004 MS Forrest County 11.7 10.9 0.0 0.0 0.1 0.2 7.2

280450003 MS Hancock County 9.9 9.1 0.0 0.0 0.2 0.4 6.1

280470008 MS Harrison County 9.6 8.7 0.0 0.0 0.2 0.3 5.6

280590006 MS Jackson County 9.5 9 0.0 0.1 0.2 0.3 6.9

280670002 MS Jones County 11.8 11.3 0.0 0.0 0.1 0.1 7.4

480290059 TX Bexar County 9 8.8 0.0 0.0 0.1 0.1 5.0

480612004 TX Cameron County 11 10.9 0.0 0.3 0.4 0.5 4.9

482010058 TX Harris County 11.1 10.9 0.0 0.0 0.1 0.3 8.0

482011035 TX Harris County 12.4 11.6 0.0 0.0 0.0 0.2 8.8

482150043 TX Hidalgo County 10.4 10.7 0.0 0.1 0.1 0.1 6.4

483550032 TX Nueces County 10.3 10 0.0 0.0 0.1 0.1 6.0

484530020 TX Travis County 8.4 7.9 0.0 0.0 0.0 0.1 4.4

484530021 TX Travis County 10.2 9.8 0.0 0.0 0.0 0.1 6.1

Figure D-45 displays the MATS UAA results for the annual average PM2.5 DVC, DVF, and 

the difference, DVF - DVC.24 Reductions in annual average PM2.5 design values associated with 

emission reductions from all sources combined are projected throughout nearly the entire domain, 

with the exception of increases near the Freshwater Bayou Canal in Vermilion Parish, Louisiana,

and Brownsville, Texas, in addition to a few additional areas in Texas and southern Louisiana. 

Some of the isolated areas of increases may represent artifacts of the MATS UAA spatial 

interpolation procedure and are not necessarily physically meaningful. Increases in the coastal ports 

are associated with new platforms and support vessel and helicopter traffic (Source Group B), as 

shown by the unmonitored area source group contributions in Figure D-46. Source Group B 

contributes as much as 1.8 μg/m3 in these areas. 

 

24 The UAA analysis could only be performed for the annual average PM2.5 NAAQS as the MATS 

software cannot calculate UAA results for the 24-hour average PM2.5 NAAQS.
Air Quality: Cumulative and Visibility Impacts D-99

Figure D-45. Current Year (DVC) and Future Year (DVF) Annual Average PM2.5 Design Values from 

the MATS Unmonitored Area Analysis (top left and top right, respectively) and the 

Difference, DVF – DVC (bottom).
D-100 2018 Gulf of Mexico Supplemental EIS

Figure D-46. Contributions of Source Groups A (top left), B (top right), C (middle left), D (middle right), 

and E (bottom) to the Future Year All-sources Annual Average PM2.5 Concentration Based 

on the MATS Unmonitored Area Analysis (note different color scales used in each panel). 

D.7.1.4 PM2.5 NAAQS Analysis using Absolute Model Predictions

The CAMx source apportionment absolute modeling results from the future year scenario are 

analyzed and compared with the PM2.5 24-hour and annual NAAQS in this section.
Air Quality: Cumulative and Visibility Impacts D-101

D.7.1.4.1 24-Hour PM2.5

The 24-hour PM2.5 NAAQS is defined as the three-year average of the annual 98th percentile 

daily average which corresponds to the 8th highest daily average in each year assuming complete 

data. Since only one calendar year of modeling results are available for the base year and future 

year scenarios, the future year 8th highest daily average PM2.5 concentration is selected for 

comparison with the NAAQS.

Modeled 8th highest daily PM2.5 concentrations in each model grid cell for the base and future 

year scenarios and the corresponding differences are shown in Figure D-47. Areas of high 

predicted PM2.5 occur along the Alabama, Louisiana and east Texas Gulf coasts in both the base 

and future year scenarios. Although predicted 8th highest daily PM2.5 concentrations in these areas 

exceed the 35 μg/m3 NAAQS, both base-year monitored design values (DVCs) and projected future 

year design values (DVFs) are below the NAAQS at monitoring sites in these areas as noted in 

Section D.7.1.3.1 above. A tendency towards over prediction of daily PM2.5 noted in the model 

performance evaluation results presented in Section D.5. The difference plot at the bottom of 

Figure D-47 shows PM2.5 reductions in the majority of the domain with some areas of increases in 

PM2.5 along portions of the immediate shoreline and offshore in the western Gulf where additional 

activities are anticipated under the 2017-2022 GOM Multisale EIS scenario, from which this 

Supplemental EIS tiers. Where PM2.5 increases are predicted, they are limited to less than 15 μg/m3

for nearly all grid cells.

Source group contributions to the annual 8th highest daily average PM2.5 concentrations 

under the future year scenario are shown in Figure D-48. These contributions are matched in time 

to the all sources 8th highest daily average PM2.5 concentrations; contributions may be different 

during other periods with elevated daily average PM2.5 values. Impacts of the new sources 

associated with the 2017-2022 GOM Multisale EIS scenario (Source Groups A and B) are largely 

focused on the area offshore of western Louisiana. Impacts from new platforms associated with the 

2017-2022 GOM Multisale EIS scenario (Source Group A) are less than 1 μg/m3

; adding in support 

vessels and helicopters (Source Group B) increases the near-shore impacts up to a maximum of 

7 μg/m3 as compared to a combined maximum impact of all Gulf of Mexico sources (Source 

Group D) of 44 μg/m3

. This Supplemental EIS tiers from the 2017-2022 GOM Multisale EIS and 

uses the scenario and alternatives analyzed in the 2017-2022 GOM Multisale EIS.

Contributions from Source Group E, which includes Source Group D plus all other U.S. and 

non-U.S. anthropogenic sources, shows the influence of inland urban areas on PM2.5 levels, 

especially in Baton Rouge and Lake Charles, Louisiana. 

Contributions from Source Group F (natural and non-U.S. emission sources including 

boundary conditions) shown in the left panel of Figure D-49 are dominated by fire emissions near 

Beaumont, Texas, and in Vermilion and Lafourche Parishes, Louisiana. Boundary condition 

contributions are less than 4 μg/m3 in the coastal areas as shown in the right panel of Figure D-49. 
D-102 2018 Gulf of Mexico Supplemental EIS

Figure D-47. Modeled 8th Highest Daily Average PM2.5 Concentrations for the Base Year (top left), 

Future Year (top right), and the Future – Base Difference (bottom). 

 
Air Quality: Cumulative and Visibility Impacts D-103

Figure D-48. Contributions of Source Groups A (top left), B (top right), C (middle left), D (middle right), 

and E (bottom) to the Future Year All-sources 8th Highest Daily Average PM2.5

Concentration (note different color scales used in each panel). 
D-104 2018 Gulf of Mexico Supplemental EIS

Figure D-49. Contributions from (left) Source Group F (natural and non-U.S. emission sources including 

boundary conditions) and (right) Boundary Conditions Only to Future Year All-sources 

8th Highest 24-hour PM2.5 (note use of different color scale in each panel).

D.7.1.4.2 Annual Average PM2.5

Modeled annual average PM2.5 for the base year, future year, and the future – base 

differences are shown in Figure D-50. Average PM2.5 concentrations decrease on most locations 

between the base and future year scenarios with changes over the western GOM between 

± 0.5 μg/m3

. Increases of up to 2.5 μg/m3 are calculated to occur in coastal Vermilion Parish, 

Louisiana. 

Source group contributions to the annual average PM2.5 concentrations under the future year 

scenario are shown in Figure D-51. Impacts of the new sources associated with the 2017-2022 

GOM Multisale EIS (from which this Supplemental EIS tiers) scenario (Source Group B) are largely 

focused on the area offshore of western Louisiana with a maximum impact of 2.2 μg/m3 as 

compared to a combined maximum impact of all GOM sources (Source Group D) of 9.3 μg/m3

. 

Source Group F contributions (natural and non-U.S. emission sources including boundary 

conditions) shown in the left panel of Figure D-52 are dominated by fire emissions near Beaumont, 

Texas, and in Vermilion and Lafourche Parishes, Louisiana. Boundary condition contributions are 

less than 2 μg/m3 in the coastal areas as shown in the right panel of Figure D-52. 
Air Quality: Cumulative and Visibility Impacts D-105

Figure D-50. Modeled Annual Average PM2.5 Concentrations for the Base Year (top left), Future Year 

(top right), and the Future – Base Difference (bottom). 
D-106 2018 Gulf of Mexico Supplemental EIS

Figure D-51. Contributions of Source Group A (top left), B (top right), C (middle left), D (middle right), 

and E (bottom) to the Future Year All-sources Annual Average PM2.5 Concentration (note 

use of different color scales in each panel).
Air Quality: Cumulative and Visibility Impacts D-107

Figure D-52. Contributions from (left) Source Group F (natural and non-U.S. emission sources including 

boundary conditions) and (right) Boundary Conditions Only to Future Year All-sources 

Annual Average PM2.5 (note use of different color scale in each panel).

D.7.1.5 NAAQS Analysis for other Criteria Air Pollutants

D.7.1.5.1 PM10

Figure D-53 displays modeled 2nd highest daily average PM10 concentrations than can be 

compared with the 24-hour average PM10 NAAQS (150 μg/m3

) for the base and future scenarios and 

the base-future differences. Areas of elevated PM10 are evident in urban and port areas and in fire 

zones along the Gulf Coasts of Texas and Louisiana (impacts of fires on PM10 can be discerned 

from the left panel of Figure D-55 described below). The PM10 decreases are modeled along the 

Louisiana coast with increases of between 2 and 5 μg/m3 in waters farther offshore associated with 

new emissions from the 2017-2022 GOM Multisale EIS scenario sources, from which this 

Supplemental EIS tiers. 

Source group contributions to the 2nd highest daily average PM10 concentrations are shown 

in Figure D-54. The maximum contribution of the new platforms and associated support vessels 

and aircraft under the 2017-2022 GOM Multisale EIS (from which this Supplemental EIS tiers) 

scenario (Source Group B) is predicted to be 10.7 μg/m3 or 7% of the NAAQS. The maximum 

contribution of all oil and gas platforms and support vessels and helicopters (Source Group C) is 

41 μg/m3 (28% of the NAAQS). Fires dominate contributions from natural and non-U.S. sources 

(Figure D-55).
D-108 2018 Gulf of Mexico Supplemental EIS

Figure D-53. Modeled 2nd Highest 24-hour Average PM10 Concentrations for the Base Year (top left), 

Future Year (top right), and the Future – Base Difference (bottom). 
Air Quality: Cumulative and Visibility Impacts D-109

Figure D-54. Contributions of Source Groups A (top left), B (top right), C (middle left), D (middle right), 

and E (bottom) to the Future Year All-sources 2nd Highest Daily Average PM10

Concentration (note use of different color scales in each panel).
D-110 2018 Gulf of Mexico Supplemental EIS

Figure D-55. Contributions from (left) Source Group F (natural and non-U.S. emission sources including 

boundary conditions) and (right) Boundary Conditions Only to Future Year All-sources 

2nd Highest Daily Average PM10 Concentration (note use of different color scale in each 

panel).

D.7.1.5.2 NO2

Results are presented here for both the 1-hour average NO2 NAAQS (100 ppb) and the 

annual average NO2 NAAQS (53 ppb). Figures D-56 and D-57 display modeled 1-hour average 

NO2 design values (based on the 8th highest daily average) for the base and future year scenarios 

along with source group contributions to the future year design values. All modeled 1-hour NO2

concentrations are below the NAAQS (100 ppb); concentrations in the immediate vicinity of the 

Louisiana Offshore Oil Port (LOOP) peak at 98.5 ppb. Concentrations decrease between the base 

and future year scenarios at most locations except for of as much as a 32-ppb increase in coastal 

Vermilion Parish, Louisiana. Increases are also projected offshore of Texas and Alabama and in 

some interior portions of Texas.

Source Group contributions to the 8th highest daily average NO2 concentrations are shown in 

Figure D-57. Contributions from new platforms and support vessels and helicopters associated with 

the 2017-2022 GOM Multisale EIS (from which this Supplemental EIS tiers) scenario (Source Group 

B) are dominated by vessel and possibly helicopter traffic in the port areas, most notably in Vermilion 

Parish, Louisiana, where the maximum contribution is 55.6 ppb. Combined contributions from new 

and existing platforms and support vessels and helicopters (Source Group C) are dominant in the 

area of the LOOP. Contributions from natural and foreign sources are less than 10 ppb (not shown).
Air Quality: Cumulative and Visibility Impacts D-111

Figure D-56. Modeled 8th Highest 1-hour NO2 Concentrations for the Base Year (top left), Future Year 

(top right), and the Future – Base Difference (bottom). 
D-112 2018 Gulf of Mexico Supplemental EIS

Figure D-57. Contributions of Source Group A (top left), B (top right), C (middle left), D (middle right), 

and E (bottom) to the Future Year All-sources 8th Highest Daily Average NO2

Concentrations (note use of different color scales in each panel).

Figures D-58 and D-59 display modeled annual average NO2 concentrations for the base 

case and future year scenarios, along with source group contributions to the future year annual 
Air Quality: Cumulative and Visibility Impacts D-113

averages. All modeled concentrations are below the NAAQS. Increases between the base case 

and future year scenarios of as much as 8 ppb are modeled to occur near the entrance to the 

Freshwater Bayou Canal in Vermilion Parish, Louisiana. Somewhat larger increases are modeled in 

the Permian Basin of west Texas. 

Contributions of Source Groups to the annual average NO2 concentrations are shown in 

Figure D-59. These results are similar to those for 1-hour NO2 shown above. Maximum impacts 

from new platforms and support vessels and helicopters associated with the 2017-2022 GOM 

Multisale EIS (from which this Supplemental EIS tiers) scenario are as much as 8.6 ppb (16% of the 

NAAQS).

Figure D-58. Modeled Annual Average NO2 Concentrations for the Base Year (top left), Future Year (top 

right), and the Future – Base Difference (bottom). 
D-114 2018 Gulf of Mexico Supplemental EIS

Figure D-59. Contributions of Source Groups A (top left), B (top right), C (middle left), D (middle right), 

and E (bottom) to the Future Year All-sources Annual Average NO2 Concentrations.
Air Quality: Cumulative and Visibility Impacts D-115

D.7.1.5.3 SO2

Results are presented here for both the 1-hour average primary SO2 NAAQS (75 ppb) and 

the 3-hour average secondary SO2 NAAQS (0.5 ppm). 

Figure D-60 displays modeled 1-hour SO2 design values (based on the 4th highest daily 

maximum 1-hour average SO2 concentration) for the base, future, and future-base scenarios. 

Modeled values for the base year are generally below the NAAQS except in the immediate vicinity of 

some major point sources. Sources in areas with deepwater platforms are evident with maximum 

values up to 50 ppb. Concentrations decrease in most locations in the future year scenario as 

sources are retired or apply control equipment with projected maximum impacts all below the 

NAAQS. No increases in excess of 5 ppb are modeled along the Gulf Coast or over the open 

ocean.

Contributions of source groups to the modeled 1-hour SO2 concentrations are shown in 

Figure D-61. New sources associated with the 2017-2022 GOM Multisale EIS (from which this 

Supplemental EIS tiers) scenario (Source Group B) are modeled to contribute less than 1 ppb.

Figure D-62 displays modeled 3-hour SO2 design values (based on the annual 2nd highest 

block, 3-hour average SO2 concentration) for the base, future, and future-base scenarios. All 

modeled values are below the NAAQS (500 ppb). These results are similar to those for the 1-hour 

SO2 described above.

Contributions of source groups to the modeled 3-hour SO2 concentrations are shown in 

Figure D-63. Results are similar to those for the 1-hour SO2 concentrations described above.
D-116 2018 Gulf of Mexico Supplemental EIS

Figure D-60. Modeled 4th Highest Daily Maximum 1-hour SO2 Concentrations for the Base Year (top 

left), Future Year (top right), and the Future – Base Difference (bottom). 
Air Quality: Cumulative and Visibility Impacts D-117

Figure D-61. Contributions of Source Group A (top left), B (top right), C (middle left), D (middle right), and 

E (bottom) to the Future Year All-sources 4th Highest Daily Maximum 1-hour SO2

Concentration (note different color scales used in each panel).
D-118 2018 Gulf of Mexico Supplemental EIS

Figure D-62. Modeled Annual 2nd Highest Block 3-hour SO2 Concentrations for the Base Year (top left), 

Future Year (top right), and the Future – Base Difference (bottom).
Air Quality: Cumulative and Visibility Impacts D-119

Figure D-63. Contributions of Source Group A (top left), B (top right), C (middle left), D (middle right), 

and E (bottom) to the Future Year All-sources 2nd Highest 3-hour Block Average SO2

Concentration (note different color scales used in each panel). 
D-120 2018 Gulf of Mexico Supplemental EIS

D.7.1.5.4 CO

Results are presented here for both the 8-hour average (9 ppm) and 1-hour average 

(35 ppm) CO NAAQS. 

Figure D-64 displays modeled 8-hour CO design values (based on the annual 2nd highest 

nonoverlapping running 8-hour average) for the base, future, and future-base scenarios. Similarly, 

Figure D-65 displays modeled 1-hour CO design values (based on the annual 2nd highest daily 

maximum 1-hour average) for the base, future, and future-base scenarios. All values are below the 

NAAQS. The maximum predicted 8-hour design value in the future year is predicted to be 8.3 ppb at 

the entrance to the Freshwater Bayou Canal in Vermilion Parish, Louisiana. Differences between 

the base and future year scenarios are less than 3 ppm. 

Individual source group contributions to CO design values were not calculated as the CAMx

source apportionment methods do not include tracers for CO. 

Figure D-64. Modeled Annual 2nd Highest Non-overlapping Running 8-hour Average CO 

Concentrations for the Base Year (top left), Future Year (top right), and the 

Future – Base Difference (bottom).
Air Quality: Cumulative and Visibility Impacts D-121

Figure D-65. Modeled Annual 2nd Highest 1-hour Average CO Concentrations for the Base Year (top 

left), Future Year (top right), and the Future – Base Difference (bottom).

D.7.2 PSD Increments

Incremental impacts of each source group at Class I and sensitive Class II areas were 

calculated for all pollutants for which PSD increments have been set (NO2, SO2, PM10, PM2.5). 

Increment consumption is based on the source group contribution calculated from the CAMx source 

contribution results. Increment consumption for 24-hour averages and the 3-hour average SO2 are 

based on the annual second highest values. Comparisons of impacts from the 2017-2022 GOM 

Multisale EIS (from which this Supplemental EIS tiers) scenario with maximum allowed PSD 

increments are presented here as an evaluation of a “threshold of concern” for potentially significant 

adverse impacts, but they do not represent a regulatory PSD increment consumption analysis. 

Results of the PSD increments analysis are summarized in Table D-24 in terms of the 

maximum increment consumption over all Class I/II areas within the 4-km modeling domain. 

Maximum impacts occur at the Breton Wilderness Class I area for all PSD pollutants and averaging 

times. Concentration increments from Source Groups A and B are less than the maximum allowed 
D-122 2018 Gulf of Mexico Supplemental EIS

PSD increments for all pollutants and averaging times except for the 24-hour PM2.5 increment from 

Source Group B at the Breton Wilderness Class I area where the maximum impact (2.19 μg/m3

) 

exceeds the Class I PSD increment (2 μg/m3

) by just under 10%. The maximum Source Group A 

24-hour average PM2.5 increment is 0.53 μg/m3

, indicating that support vessels or helicopter traffic 

associated with new offshore platforms, rather than emissions from the platforms themselves, are 

largely responsible for pushing the maximum impact above the Class I PSD increment at Breton 

Wilderness. The 24-hour PM2.5 impact from Source Group B averaged over all grid cells covering 

the Breton Wilderness Class I area is 1.79 μg/m3

. Maximum impacts from Source Group C exceed 

the annual and 24-hour PM2.5, the 24-hour PM10, and the annual NO2 Class I PSD increments at 

Breton Wilderness. A summary of impacts from Source Groups A, B, and C for all Class I/II areas is 

provided in Table D-25. 

Table D-24. Maximum Source Group Contributions for PSD Pollutants at Class I and Sensitive Class II 

Areas in the 4-km Modeling Domain. 

Group Max @ Any 

Class I Area 

Percent of PSD 

Class I 

Increment

Class I Area 

Where Max 

Occurred

Max @ Any 

Class II Area

Percent of 

PSD Class II 

Increment

Class II Area 

Where Max 

Occurred

PM10 Annual (Increment = 4 μg/m3, 17 μg/m3)

A 0.04449 1.1% Breton Wilderness 0.04196 0.2% Gulf Islands NS

B 0.29475 7.4% Breton Wilderness 0.35482 2.1% Gulf Islands NS

C 1.44391 36.1% Breton Wilderness 1.24095 7.3% Gulf Islands NS

PM10 24-Hour (Class I, II Increment = 8 μg/m3, 30 μg/m3)

A 0.53529 6.7% Breton Wilderness 0.61362 2.0% Gulf Islands NS

B 2.19999 27.5% Breton Wilderness 2.45061 8.2% Gulf Islands NS

C 14.4191 180.2% Breton Wilderness 13.9928 46.6% Gulf Islands NS

PM2.5 Annual (Class I, II Increment = 1 μg/m3, 4 μg/m3)

A 0.04449 4.4% Breton Wilderness 0.04196 1.0% Gulf Islands NS

B 0.29152 29.2% Breton Wilderness 0.34969 8.7% Gulf Islands NS

C 1.43641 143.6% Breton Wilderness 1.23711 30.9% Gulf Islands NS

PM2.5 24-Hour (Class I, II Increment = 2 μg/m3, 9 μg/m3)

A 0.53527 26.8% Breton Wilderness 0.6136 6.8% Gulf Islands NS

B 2.19194 109.6% Breton Wilderness 2.44002 27.1% Gulf Islands NS

C 14.3964 719.8% Breton Wilderness 13.9795 155.3% Gulf Islands NS

NO2 Annual (Class I, II Increment = 2.5 μg/m3, 25 μg/m3)

A 0.12789 5.1% Breton Wilderness 0.14467 0.6% Gulf Islands NS

B 0.65768 26.3% Breton Wilderness 0.93535 3.7% Gulf Islands NS

C 2.61628 104.7% Breton Wilderness 1.95517 7.8% Breton NWR

SO2 Annual (Class I, II Increment = 2 μg/m3, 20 μg/m3)

A 0.00113 0.1% Breton Wilderness 0.00121 0.0% Gulf Islands NS

B 0.00271 0.1% Breton Wilderness 0.00178 0.0% Gulf Islands NS

C 0.0684 3.4% Breton Wilderness 0.05601 0.3% Breton NWR

SO2 24-Hour (Class I, II Increment = 5 μg/m3, 91 μg/m3)

A 0.01009 0.2% Breton Wilderness 0.01104 0.0% Breton NWR

B 0.01891 0.4% Breton Wilderness 0.0156 0.0% Breton NWR

C 0.53913 10.8% Breton Wilderness 0.41742 0.5% Breton NWR

SO2 3-Hour (Class I, II Increment = 25 μg/m3, 512 μg/m3)

A 0.02228 0.1% Breton Wilderness 0.01655 0.0% Breton NWR
Air Quality: Cumulative and Visibility Impacts D-123

Group Max @ Any 

Class I Area 

Percent of PSD 

Class I 

Increment

Class I Area 

Where Max 

Occurred

Max @ Any 

Class II Area

Percent of 

PSD Class II 

Increment

Class II Area 

Where Max 

Occurred

B 0.03451 0.1% Breton Wilderness 0.02296 0.0% Breton NWR

C 1.17783 4.7% Breton Wilderness 1.03688 0.2% Breton NWR

NS = National Seashore; NWR = National Wildlife Refuge.

D.7.3 AQRV Impacts

D.7.3.1 Visibility

Incremental visibility impacts were calculated for each source group as well as the 

cumulative impact of all sources combined. The approach used the incremental concentrations as 

quantified by the CAMx PSAT source apportionment tool simulation for each source group. 

Changes in light extinction from CAMx model concentration increments due to emissions from each 

source group were calculated for each day at grid cells that intersect Class I and sensitive Class II 

areas within the 12-km modeling domain. 

Calculation of incremental visibility impacts followed procedures recommended by the 

Federal Land Managers (FLAG, 2010) as described in Section D.6.2.3.1. 

For each individual source group, the estimated visibility degradation at each Class I and 

sensitive Class II area in the 12-km modeling domain due to emissions from the source group are 

presented in terms of the number of days that exceed a threshold change in deciview (∆dv) relative 

to background conditions. The number of days with a ∆dv greater than 0.5 and 1.0 are reported.

Results of the FLAG (2010) incremental visibility impact assessment for Source Groups A 

and B are presented in Tables D-26 and D-27, respectively. For Source Group A, the annual

8th highest ∆dv exceed the 1.0 threshold at Breton Wilderness, Breton National Wildlife Refuge, and 

Gulf Islands National Seashore. Incremental impacts for Source Group B are larger and include 

days with the 8th highest ∆dv greater than 1.0 at Padre Island National Seashore in addition to the 

areas mentioned above, as well as values greater than 0.5 at Chassahowitzka Wilderness and 

St. Marks National Wildlife Refuge. 
D-124 2018 Gulf of Mexico Supplemental EIS

Table D-25. Source Group Contributions for PSD Pollutants at All Class I and Sensitive Class II Areas in the 4-km Modeling Domain.

Source Group A

Pollutant NO2 (μg/m3) PM10 (μg/m3) PM25 (μg/m3) SO2 (μg/m3)

Averaging Time Annual3 24-hour2 Annual3 24-hour4 Annual3 3-hour2 24-hour2 Annual3

Class I State Owner PSD Class I Increment1

2.5 8 4 2 1 25 5 2

Breton Wilderness LA FWS 0.128 0.535 0.044 0.535 0.044 0.022 0.010 0.001

Class II State Owner PSD Class II Increment1

25 30 17 9 4 512 91 20

Breton NWR LA FWS 0.063 0.436 0.036 0.436 0.036 0.017 0.011 0.001

Gulf Islands NS FL,MS NPS 0.145 0.614 0.042 0.614 0.042 0.014 0.007 0.001

Padre Island NS TX NPS 0.014 0.169 0.014 0.169 0.014 0.006 0.002 0.000

Source Group B

Pollutant NO2 (μg/m3) PM10 (μg/m3) PM25 (μg/m3) SO2 (μg/m3)

Averaging Time Annual3 24-hour2 Annual3 24-hour4 Annual3 3-hour2 24-hour2 Annual3

Class I State Owner PSD Class I Increment1

2.5 8 4 2 1 25 5 2

Breton Wilderness LA FWS 0.658 2.200 0.295 2.192 0.292 0.035 0.019 0.003

Class II State Owner PSD Class II Increment1

25 30 17 9 4 512 91 20

Breton NWR LA FWS 0.321 1.752 0.182 1.748 0.181 0.023 0.016 0.002

Gulf Islands NS FL,MS NPS 0.935 2.451 0.355 2.440 0.350 0.017 0.008 0.002

Padre Island NS TX NPS 0.181 1.013 0.166 1.012 0.165 0.006 0.003 0.001

Source Group C

Pollutant NO2 (μg/m3) PM10 (μg/m3) PM25 (μg/m3) SO2 (μg/m3)

Averaging Time Annual3 24-hour2 Annual3 24-hour4 Annual3 3-hour2 24-hour2 Annual3

Class I State Owner PSD Class I Increment1

2.5 8 4 2 1 25 5 2

Breton Wilderness LA FWS 2.616 14.419 1.444 14.396 1.436 1.178 0.539 0.068

Class II State Owner PSD Class II Increment1

25 30 17 9 4 512 91 20

Breton NWR LA FWS 1.955 12.577 1.127 12.559 1.122 1.037 0.417 0.056

Gulf Islands NS FL,MS NPS 1.521 13.993 1.241 13.979 1.237 0.410 0.196 0.016

Padre Island NS TX NPS 0.198 2.031 0.225 2.030 0.224 0.044 0.022 0.002

NS = National Seashore; NWR = National Wildlife Refuge.

1 The PSD demonstrations serve information purposes only and do not constitute a regulatory PSD increment consumption analysis.

2 Based on 2nd highest 24-hour average. 3 Annual arithmetic mean.

4 Based on 2ndhighest 24-hour average.
Air Quality: Cumulative and Visibility Impacts D-125

Table D-26. Incremental Visibility Impacts Relative to Natural Background Conditions from Source 

Group A.

Area Max ∆dv 8th High ∆dv

No. of Days

>1.0 >0.5

Class I Areas

Bandelier National Monument 0.00067 0.00016 0 0

Black Canyon of the Gunnison National Park 0.00002 0.00000 0 0

Bosque del Apache National Wildlife Refuge 0.00050 0.00018 0 0

Bosque del Apache (Chupadera Unit) Wilderness 0.00036 0.00013 0 0

Bosque del Apache (Indian Well Unit) Wilderness 0.00036 0.00014 0 0

Bosque del Apache (Little San Pascual Unit) Wilderness 0.00072 0.00023 0 0

Big Bend National Park 0.00746 0.00286 0 0

Bradwell Bay Wilderness 0.08487 0.05269 0 0

Breton Wilderness 2.65806 1.54415 22 57

Caney Creek Wilderness 0.21478 0.07569 0 0

Cape Romain Wilderness 0.08319 0.01800 0 0

Carlsbad Caverns National Park 0.00337 0.00163 0 0

Chassahowitzka Wilderness 0.26500 0.11299 0 0

Cohutta Wilderness 0.07214 0.02483 0 0

Dolly Sods Wilderness 0.01130 0.00424 0 0

Eagles Nest Wilderness 0.00009 0.00001 0 0

Everglades National Park 0.13374 0.04721 0 0

Flat Tops Wilderness 0.00002 0.00000 0 0

Great Sand Dunes National Monument 0.00020 0.00006 0 0

Great Smoky Mountains National Park 0.02866 0.01263 0 0

Guadalupe Mountains National Park 0.00283 0.00094 0 0

Hercules-Glades Wilderness 0.05899 0.02394 0 0

James River Face Wilderness 0.00768 0.00391 0 0

Joyce-Kilmer-Slickrock Wilderness 0.02655 0.00881 0 0

La Garita Wilderness 0.00013 0.00001 0 0

Linville Gorge Wilderness 0.01892 0.00436 0 0

Mammoth Cave National Park 0.04330 0.01815 0 0

Maroon Bells-Snowmass Wilderness 0.00007 0.00001 0 0

Mingo National Wildlife Refuge 0.07764 0.04615 0 0

Mount_Zirkel Wilderness 0.00002 0.00000 0 0

Okefenokee National Wildlife Refuge 0.06476 0.03510 0 0

Otter Creek Wilderness 0.01108 0.00356 0 0

Pecos Wilderness 0.00091 0.00023 0 0

Rawah Wilderness 0.00005 0.00001 0 0

Rocky Mountain National Park 0.00023 0.00003 0 0

Saint Marks National Wildlife Refuge 0.24139 0.19294 0 0

Salt Creek Wilderness 0.00278 0.00149 0 0

San Pedro Parks Wilderness 0.00038 0.00010 0 0

Shenandoah National Park 0.02361 0.00945 0 0

Shining Rock Wilderness 0.02231 0.01030 0 0

Sipsey Wilderness 0.09946 0.02484 0 0
D-126 2018 Gulf of Mexico Supplemental EIS

Area Max ∆dv 8th High ∆dv No. of Days

>1.0 >0.5

Swanquarter National Wildlife Refuge 0.01852 0.00864 0 0

Upper Buffalo Wilderness 0.05460 0.02255 0 0

Weminuche Wilderness 0.00018 0.00002 0 0

West Elk Wilderness 0.00006 0.00001 0 0

Wheeler Peak Wilderness 0.00037 0.00012 0 0

White Mountain Wilderness 0.00085 0.00042 0 0

Wichita Mountains National Wildlife Refuge 0.02963 0.01625 0 0

Wichita Mountains (Charons Garden Unit) Wilderness 0.02932 0.01390 0 0

Wichita Mountains (North Mountain Unit) Wilderness 0.02983 0.01408 0 0

Wolf Island Wilderness 0.10444 0.02825 0 0

Class II Areas

Breton National Wildlife Refuge 2.51391 1.44000 13 41

Gulf Islands National Seashore 3.59820 1.79194 26 64

Padre Island National Seashore 1.28497 0.44893 2 5

Table D-27. Incremental Visibility Impacts Relative to Natural Background Conditions from Source 

Group B.

Area Max ∆dv 8th High ∆dv No. of Days

>1.0 >0.5

Class I Areas

Bandelier NM 0.00588 0.00225 0 0

Black Canyon of the Gunnison National Park 0.00027 0.00003 0 0

Bosque del Apache National Wildlife Refuge 0.00927 0.00254 0 0

Bosque del Apache (Chupadera Unit) Wilderness 0.00674 0.00173 0 0

Bosque del Apache (Indian Well Unit) Wilderness 0.00692 0.00183 0 0

Bosque del Apache (Little San Pascual Unit) Wilderness 0.01274 0.00311 0 0

Big Bend National Park 0.06000 0.03458 0 0

Bradwell Bay Wilderness 0.43077 0.29328 0 0

Breton Wilderness 7.77098 6.27094 155 256

Caney Creek Wilderness 1.37302 0.48258 1 7

Cape Romain Wilderness 0.31147 0.08130 0 0

Carlsbad Caverns National Park 0.03024 0.01639 0 0

Chassahowitzka Wilderness 1.35442 0.55791 3 9

Cohutta Wilderness 0.37888 0.12203 0 0

Dolly Sods Wilderness 0.06063 0.03063 0 0

Eagles Nest Wilderness 0.00128 0.00016 0 0

Everglades National Park 0.72032 0.18655 0 2

Flat Tops Wilderness 0.00022 0.00003 0 0

Great Sand Dunes National Monument 0.00329 0.00067 0 0

Great Smoky Mountains National Park 0.15002 0.07991 0 0

Guadalupe Mountains National Park 0.02529 0.01502 0 0

Hercules-Glades Wilderness 0.41027 0.16105 0 0

James River Face Wilderness 0.05739 0.02478 0 0
Air Quality: Cumulative and Visibility Impacts D-127

Joyce-Kilmer-Slickrock Wilderness 0.15156 0.07538 0 0

La Garita Wilderness 0.00252 0.00019 0 0

Linville Gorge Wilderness 0.10346 0.03554 0 0

Mammoth Cave National Park 0.23624 0.09683 0 0

Maroon Bells-Snowmass Wilderness 0.00103 0.00006 0 0

Mingo National Wildlife Refuge 0.44782 0.25368 0 0

Mount_Zirkel Wilderness 0.00019 0.00003 0 0

Okefenokee National Wildlife Refuge 0.40346 0.21507 0 0

Otter Creek Wilderness 0.06577 0.02996 0 0

Pecos Wilderness 0.00863 0.00303 0 0

Rawah Wilderness 0.00062 0.00016 0 0

Rocky Mountain National Park 0.00128 0.00028 0 0

Saint Marks National Wildlife Refuge 1.04546 0.79486 2 23

Salt Creek Wilderness 0.03543 0.01558 0 0

San Pedro Parks Wilderness 0.00562 0.00171 0 0

Shenandoah National Park 0.13636 0.05190 0 0

Shining Rock Wilderness 0.12422 0.06132 0 0

Sipsey Wilderness 0.47703 0.15148 0 0

Swanquarter National Wildlife Refuge 0.09369 0.04563 0 0

Upper Buffalo Wilderness 0.42865 0.16699 0 0

Weminuche Wilderness 0.00268 0.00031 0 0

West Elk Wilderness 0.00100 0.00006 0 0

Wheeler Peak Wilderness 0.00491 0.00148 0 0

White Mountain Wilderness 0.01424 0.00635 0 0

Wichita Mountains National Wildlife Refuge 0.19286 0.10693 0 0

Wichita Mountains (Charons Garden Unit) Wilderness 0.18960 0.08842 0 0

Wichita Mountains (North Mountain Unit) Wilderness 0.19390 0.09435 0 0

Wolf Island Wilderness 0.39934 0.13342 0 0

Class II Areas

Breton National Wildlife Refuge 7.10912 4.34015 104 193

Gulf Islands National Seashore 10.54646 6.33562 198 311

Padre Island National Seashore 5.10452 3.05326 115 204

D.7.3.1.2 Cumulative Visibility Analysis

For the cumulative visibility impacts analysis, the MATS software was applied with observed 

PM species concentrations and monthly average relative humidity from IMPROVE monitoring sites 

to calculate daily visibility impairment at Class I areas from which the W20% and B20% visibility 

days metrics are determined as described in Section D.7.2.3.1. Since not all Class I areas have a 

co-located IMPROVE monitoring site, IMPROVE observations were mapped to nearby Class I areas 

that did not include an IMPROVE monitor. In Table D-28, the Class I area of interest is shown in the 

first column and the IMPROVE site used to represent observed visibility at the Class I area is shown 

in the third column. For example, the IMPROVE data from Dolly Sods Wilderness was used to 

represent observed visibility for both Dolly Sods Wilderness and Otter Creek Wilderness. The MATS 

includes mappings of IMPROVE site to Class I areas. However, MATS does not include a mapping 
D-128 2018 Gulf of Mexico Supplemental EIS

for the Breton Wilderness or Bradwell Bay Class I areas and, therefore, cumulative visibility results 

for these areas are not included in this analysis.

Tables D-28 and D-29 resent results for the W20% visibility days, and Tables D-30

and D-31 present results for the B20% visibility days. Visibility improvement between the base and 

future year scenarios (i.e., positive BY-FY results in Tables D-29 and D-31) are seen at most Class I 

areas, with eight areas experiencing reductions in visibility on the W20% days. All of these areas 

are in New Mexico and Colorado, and Gulf of Mexico sources (Source Group D) contribute less than 

0.02 dv to visibility impairment in these areas. The maximum contribution from new platforms and 

support vessels and helicopters associated with the 2017-2022 GOM Multisale EIS (from which this 

Supplemental EIS tiers) scenario (Source Group B) to any area on the W20% days is 0.04 dv at 

Caney Creek, Arkansas. Contributions from all Gulf of Mexico sources (Source Group D) are the 

greatest (0.34 dv) at St. Marks National Wildlife Refuge, Florida. 

For the B20% visibility days, 11 areas experience reductions in visibility. All but one of these 

areas are located in New Mexico and Colorado; the lone exception is Big Bend National Park in 

Texas. Contributions from Gulf of Mexico sources to these 11 areas are all less than 0.01 dv. The 

maximum contribution from new platforms and support vessels and helicopters associated with the 

2017-2022 GOM Multisale EIS (from which this Supplemental EIS tiers) (Source Group B) to any 

area on the B20% days is 0.01 dv, which occurs at several sites. Contributions from all Gulf of 

Mexico sources (Source Group D) are the greatest (0.08 dv) at St. Marks Wilderness in Florida. 
 

Air Quality: Cumulative and Visibility Impacts

D-129

Table D-28. Cumulative Visibility Results for 20% Worst Visibility Days (W20%) at Class I Areas for Base (2012) Year (BY) and Future Year 

(FY) Scenarios with All Sources Included and with Contributions from Each Source Group Removed.

FY DV without Source Group

Class I Name State IMPROVE Site BY DV FY DV A B C D E

Bandelier NM NM BAND1 11.79 11.93 11.93 11.93 11.93 11.93 7.56

Big Bend NP TX BIBE1 16.40 16.11 16.11 16.11 16.10 16.09 11.13

Black Canyon of the Gunnison NM CO WEMI1 10.11 10.05 10.05 10.05 10.05 10.05 9.34

Bosque del Apache NM BOAP1 13.65 13.90 13.90 13.90 13.90 13.90 10.69

Caney Creek Wilderness AR CACR1 22.66 20.59 20.58 20.55 20.45 20.36 13.36

Carlsbad Caverns NP TX GUMO1 15.17 15.14 15.14 15.14 15.14 15.14 9.33

Chassahowitzka FL CHAS1 21.77 20.43 20.43 20.41 20.35 20.18 11.45

Cohutta Wilderness GA COHU1 23.94 21.11 21.11 21.11 21.09 21.06 12.89

Dolly Sods Wilderness WV DOSO1 23.45 19.52 19.52 19.52 19.52 19.51 14.64

Eagles Nest Wilderness CO WHRI1 8.81 8.72 8.72 8.72 8.72 8.72 7.84

Everglades NP FL EVER1 18.33 17.63 17.63 17.63 17.63 17.51 15.00

Flat Tops Wilderness CO WHRI1 8.81 8.72 8.72 8.72 8.72 8.72 7.84

Great Sand Dunes NM CO GRSA1 11.52 11.62 11.62 11.62 11.62 11.62 8.94

Great Smoky Mountains NP TN GRSM1 23.75 20.30 20.30 20.29 20.29 20.28 13.84

Guadalupe Mountains NP TX GUMO1 15.17 15.14 15.14 15.14 15.14 15.14 9.33

Hercules-Glades Wilderness MO HEGL1 23.50 21.48 21.47 21.46 21.42 21.37 13.21

James River Face Wilderness VA JARI1 23.50 20.75 20.75 20.74 20.74 20.73 16.07

Joyce-Kilmer-Slickrock Wilderness TN GRSM1 23.75 20.30 20.30 20.29 20.29 20.28 13.84

La Garita Wilderness CO WEMI1 10.11 10.05 10.05 10.05 10.05 10.05 9.34

Linville Gorge Wilderness NC LIGO1 22.61 19.38 19.38 19.37 19.37 19.36 13.29

Maroon Bells-Snowmass Wilderness CO WHRI1 8.81 8.72 8.72 8.72 8.72 8.72 7.84

Mammoth Cave NP KY MACA1 26.11 22.68 22.68 22.68 22.67 22.66 14.97

Mount Zirkel Wilderness CO MOZI1 9.33 9.20 9.20 9.20 9.20 9.20 7.25

Okefenokee GA OKEF1 23.31 21.99 21.99 21.98 21.93 21.87 12.62

Otter Creek Wilderness WV DOSO1 23.45 19.52 19.52 19.52 19.52 19.51 14.64

Pecos Wilderness NM WHPE1 10.04 10.10 10.10 10.10 10.10 10.10 6.73

Rawah Wilderness CO MOZI1 9.33 9.20 9.20 9.20 9.20 9.20 7.25

Cape Romain SC ROMA1 23.40 21.77 21.77 21.77 21.73 21.68 13.12

Rocky Mountain NP CO ROMO1 12.02 11.86 11.86 11.86 11.86 11.86 9.19
Table D-28. Cumulative Visibility Results for 20% Worst Visibility Days (W20%) at Class I Areas for Base (2012) Year (BY) and Future Year 

(FY) Scenarios with All Sources Included and with Contributions from Each Source Group Removed. (continued)

D-130 2018 Gulf of Mexico Supplemental EIS

FY DV without Source Group

Class I Name State IMPROVE Site BY DV FY DV A B C D E

Salt Creek NM SACR1 17.22 17.79 17.79 17.79 17.79 17.78 7.30

St. Marks FL SAMA1 23.01 21.18 21.18 21.16 21.06 20.84 13.43

San Pedro Parks Wilderness NM SAPE1 9.94 9.98 9.98 9.98 9.98 9.98 7.15

Shenandoah NP VA SHEN1 22.95 19.42 19.42 19.42 19.41 19.39 14.90

Shining Rock Wilderness NC SHRO1 21.90 18.78 18.78 18.77 18.77 18.76 12.25

Sipsey Wilderness AL SIPS1 23.98 21.48 21.48 21.47 21.46 21.44 13.01

Swanquarter NC SWAN1 22.29 20.39 20.39 20.39 20.38 20.37 13.42

Upper Buffalo Wilderness AR UPBU1 22.93 20.90 20.89 20.87 20.79 20.71 12.97

West Elk Wilderness CO WHRI1 8.81 8.72 8.72 8.72 8.72 8.72 7.84

Weminuche Wilderness CO WEMI1 10.11 10.05 10.05 10.05 10.05 10.05 9.34

White Mountain Wilderness NM WHIT1 14.24 14.60 14.60 14.60 14.59 14.59 8.15

Wheeler Peak Wilderness NM WHPE1 10.04 10.10 10.10 10.10 10.10 10.10 6.73

Wichita Mountains OK WIMO1 21.55 20.33 20.33 20.32 20.31 20.30 10.33

Wolf Island GA OKEF1 23.31 21.99 21.99 21.98 21.93 21.87 12.62

NM = National Monument; NP = National Park.
 

Air Quality: Cumulative and Visibility Impacts

D-131

Table D-29. Differences in Cumulative Visibility Results for 20% Worst Visibility Days (W20%) at Class I Areas Between the Future Year (FY) 

and Base Year (BY) Scenarios and Contributions of Each Source Group to the Future Year Scenario Visibility. 

FY DV without Source Group

Class I Name State IMPROVE Site BYFY DV A B C D E

Bandelier NM NM BAND1 -0.14 0.00 0.00 0.00 0.00 4.37

Big Bend NP TX BIBE1 0.29 0.00 0.00 0.01 0.02 4.98

Black Canyon of the Gunnison NM CO WEMI1 0.06 0.00 0.00 0.00 0.00 0.71

Bosque del Apache NM BOAP1 -0.25 0.00 0.00 0.00 0.00 3.21

Caney Creek Wilderness AR CACR1 2.07 0.01 0.04 0.14 0.23 7.23

Carlsbad Caverns NP TX GUMO1 0.03 0.00 0.00 0.00 0.00 5.81

Chassahowitzka FL CHAS1 1.34 0.00 0.02 0.08 0.25 8.98

Cohutta Wilderness GA COHU1 2.83 0.00 0.00 0.02 0.05 8.22

Dolly Sods Wilderness WV DOSO1 3.93 0.00 0.00 0.00 0.01 4.88

Eagles Nest Wilderness CO WHRI1 0.09 0.00 0.00 0.00 0.00 0.88

Everglades NP FL EVER1 0.70 0.00 0.00 0.00 0.12 2.63

Flat Tops Wilderness CO WHRI1 0.09 0.00 0.00 0.00 0.00 0.88

Great Sand Dunes NM CO GRSA1 -0.10 0.00 0.00 0.00 0.00 2.68

Great Smoky Mountains NP TN GRSM1 3.45 0.00 0.01 0.01 0.02 6.46

Guadalupe Mountains NP TX GUMO1 0.03 0.00 0.00 0.00 0.00 5.81

Hercules-Glades Wilderness MO HEGL1 2.02 0.01 0.02 0.06 0.11 8.27

James River Face Wilderness VA JARI1 2.75 0.00 0.01 0.01 0.02 4.68

Joyce-Kilmer-Slickrock Wilderness TN GRSM1 3.45 0.00 0.01 0.01 0.02 6.46

La Garita Wilderness CO WEMI1 0.06 0.00 0.00 0.00 0.00 0.71

Linville Gorge Wilderness NC LIGO1 3.23 0.00 0.01 0.01 0.02 6.09

Maroon Bells-Snowmass Wilderness CO WHRI1 0.09 0.00 0.00 0.00 0.00 0.88

Mammoth Cave NP KY MACA1 3.43 0.00 0.00 0.01 0.02 7.71

Mount Zirkel Wilderness CO MOZI1 0.13 0.00 0.00 0.00 0.00 1.95

Okefenokee GA OKEF1 1.32 0.00 0.01 0.06 0.12 9.37

Otter Creek Wilderness WV DOSO1 3.93 0.00 0.00 0.00 0.01 4.88

Pecos Wilderness NM WHPE1 -0.06 0.00 0.00 0.00 0.00 3.37

Rawah Wilderness CO MOZI1 0.13 0.00 0.00 0.00 0.00 1.95

Cape Romain SC ROMA1 1.63 0.00 0.00 0.04 0.09 8.65

Rocky Mountain NP CO ROMO1 0.16 0.00 0.00 0.00 0.00 2.67
Table D-29. Differences in Cumulative Visibility Results for 20% Worst Visibility Days (W20%) at Class I Areas Between the Future Year (FY) 

and Base Year (BY) Scenarios and Contributions of Each Source Group to the Future Year Scenario Visibility (continued).

D-132 2018 Gulf of Mexico Supplemental EIS

FY DV without Source Group

Class I Name State IMPROVE Site BYFY DV A B C D E

Salt Creek NM SACR1 -0.57 0.00 0.00 0.00 0.01 10.49

St. Marks FL SAMA1 1.83 0.00 0.02 0.12 0.34 7.75

San Pedro Parks Wilderness NM SAPE1 -0.04 0.00 0.00 0.00 0.00 2.83

Shenandoah NP VA SHEN1 3.53 0.00 0.00 0.01 0.03 4.52

Shining Rock Wilderness NC SHRO1 3.12 0.00 0.01 0.01 0.02 6.53

Sipsey Wilderness AL SIPS1 2.50 0.00 0.01 0.02 0.04 8.47

Swanquarter NC SWAN1 1.90 0.00 0.00 0.01 0.02 6.97

Upper Buffalo Wilderness AR UPBU1 2.03 0.01 0.03 0.11 0.19 7.93

West Elk Wilderness CO WHRI1 0.09 0.00 0.00 0.00 0.00 0.88

Weminuche Wilderness CO WEMI1 0.06 0.00 0.00 0.00 0.00 0.71

White Mountain Wilderness NM WHIT1 -0.36 0.00 0.00 0.01 0.01 6.45

Wheeler Peak Wilderness NM WHPE1 -0.06 0.00 0.00 0.00 0.00 3.37

Wichita Mountains OK WIMO1 1.22 0.00 0.01 0.02 0.03 10.00

Wolf Island GA OKEF1 1.32 0.00 0.01 0.06 0.12 9.37

NM = National Monument; NP = National Park.
Air Quality: Cumulative and Visibility Impacts D-133

Table D-30. Cumulative Visibility Results for 20% Best Visibility Days (B20%) at Class I Areas for Base 

(2012) Year (BY) and Future Year (FY) Scenarios with All Sources Included and with 

Contributions from Each Source Group Removed. 

FY DV without Source Group

Class I Name State IMPROVE 

Site

BY 

DV

FY 

DV A B C D E 

Bandelier NM NM BAND1 3.81 3.96 3.96 3.96 3.96 3.96 1.51

Big Bend NP TX BIBE1 5.76 5.86 5.86 5.86 5.86 5.86 3.50

Black Canyon of the 

Gunnison NM CO WEMI1 2.04 2.18 2.18 2.18 2.18 2.18 1.55

Bosque del Apache NM BOAP1 5.57 5.60 5.60 5.60 5.60 5.60 3.60

Caney Creek 

Wilderness AR CACR1 9.82 9.25 9.25 9.24 9.22 9.20 5.15

Carlsbad Caverns NP TX GUMO1 5.08 5.03 5.03 5.03 5.03 5.03 2.39

Chassahowitzka FL CHAS1 14.05 13.55 13.55 13.54 13.52 13.34 8.22

Cohutta Wilderness GA COHU1 11.47 10.59 10.59 10.59 10.59 10.58 4.62

Dolly Sods Wilderness WV DOSO1 9.18 8.38 8.38 8.38 8.38 8.37 5.63

Eagles Nest Wilderness CO WHRI1 0.48 0.39 0.39 0.39 0.39 0.39 0.00

Everglades NP FL EVER1 11.29 11.08 11.08 11.07 11.06 10.99 8.01

Flat Tops Wilderness CO WHRI1 0.48 0.39 0.39 0.39 0.39 0.39 0.00

Great Sand Dunes NM CO GRSA1 3.57 3.56 3.56 3.56 3.56 3.56 2.20

Great Smoky Mountains 

NP TN GRSM1 11.10 9.78 9.78 9.78 9.78 9.77 4.22

Guadalupe Mountains 

NP TX GUMO1 5.08 5.03 5.03 5.03 5.03 5.03 2.39

Hercules-Glades 

Wilderness MO HEGL1 11.29 10.84 10.84 10.84 10.83 10.82 5.94

James River Face 

Wilderness VA JARI1 12.36 11.26 11.26 11.26 11.25 11.25 7.13

Joyce-Kilmer-Slickrock

Wilderness TN GRSM1 11.10 9.78 9.78 9.78 9.78 9.77 4.22

La Garita Wilderness CO WEMI1 2.04 2.18 2.18 2.18 2.18 2.18 1.55

Linville Gorge 

Wilderness NC LIGO1 9.96 9.21 9.21 9.21 9.20 9.19 4.85

Maroon BellsSnowmass Wilderness CO WHRI1 0.48 0.39 0.39 0.39 0.39 0.39 0.00

Mammoth Cave NP KY MACA1 14.20 13.04 13.04 13.04 13.03 13.02 7.41

Mount Zirkel Wilderness CO MOZI1 0.89 0.79 0.79 0.79 0.79 0.79 0.00

Okefenokee GA OKEF1 13.40 12.89 12.89 12.89 12.88 12.85 7.58

Otter Creek Wilderness WV DOSO1 9.18 8.38 8.38 8.38 8.38 8.37 5.63

Pecos Wilderness NM WHPE1 1.09 1.24 1.24 1.24 1.24 1.24 0.00

Rawah Wilderness CO MOZI1 0.89 0.79 0.79 0.79 0.79 0.79 0.00

Cape Romain SC ROMA1 13.79 13.09 13.09 13.09 13.09 13.08 8.48

Rocky Mountain NP CO ROMO1 1.64 1.62 1.62 1.62 1.62 1.62 0.53

Salt Creek NM SACR1 7.11 7.42 7.42 7.42 7.42 7.42 2.89

St. Marks FL SAMA1 13.73 13.00 12.99 12.99 12.92 12.75 8.31

San Pedro Parks 

Wilderness NM SAPE1 1.30 1.37 1.37 1.37 1.37 1.37 0.61
D-134 2018 Gulf of Mexico Supplemental EIS

FY DV without Source Group

Class I Name State IMPROVE 

Site

BY 

DV

FY 

DV A B C D E 

Shenandoah NP VA SHEN1 8.68 7.66 7.66 7.66 7.65 7.65 4.56

Shining Rock 

Wilderness NC SHRO1 6.58 5.81 5.80 5.80 5.79 5.79 2.03

Sipsey Wilderness AL SIPS1 13.10 12.20 12.20 12.19 12.16 12.13 6.79

Swanquarter NC SWAN1 11.76 11.09 11.09 11.08 11.08 11.08 7.45

Upper Buffalo 

Wilderness AR UPBU1 10.35 9.80 9.80 9.79 9.77 9.76 5.03

West Elk Wilderness CO WHRI1 0.48 0.39 0.39 0.39 0.39 0.39 0.00

Weminuche Wilderness CO WEMI1 2.04 2.18 2.18 2.18 2.18 2.18 1.55

White Mountain 

Wilderness NM WHIT1 3.24 3.45 3.45 3.45 3.45 3.45 1.41

Wheeler Peak 

Wilderness NM WHPE1 1.09 1.24 1.24 1.24 1.24 1.24 0.00

Wichita Mountains OK WIMO1 9.53 9.24 9.24 9.24 9.24 9.24 5.36

Wolf Island GA OKEF1 13.40 12.89 12.89 12.89 12.88 12.85 7.58

NM = National Monument; NP = National Park.

Table D-31. Differences in Cumulative Visibility Results for 20% Best Visibility Days (B20%) at Class I 

Areas Between the Future Year (FY) and Base Year (BY) Scenarios and Contributions of 

Each Source Group to the Future Year Scenario Visibility. 

Source Group Contribution to FY 

DV

Class I Name State IMPROVE 

Site

BY - FY 

DV A B C D E 

Bandelier NM NM BAND1 -0.15 0.00 0.00 0.00 0.00 2.45

Big Bend NP TX BIBE1 -0.10 0.00 0.00 0.00 0.00 2.36

Black Canyon of the Gunnison 

NM CO WEMI1 -0.14 0.00 0.00 0.00 0.00 0.63

Bosque del Apache NM BOAP1 -0.03 0.00 0.00 0.00 0.00 2.00

Caney Creek Wilderness AR CACR1 0.57 0.00 0.01 0.03 0.05 4.10

Carlsbad Caverns NP TX GUMO1 0.05 0.00 0.00 0.00 0.00 2.64

Chassahowitzka FL CHAS1 0.50 0.00 0.01 0.03 0.21 5.33

Cohutta Wilderness GA COHU1 0.88 0.00 0.00 0.00 0.01 5.97

Dolly Sods Wilderness WV DOSO1 0.80 0.00 0.00 0.00 0.01 2.75

Eagles Nest Wilderness CO WHRI1 0.09 0.00 0.00 0.00 0.00 0.39

Everglades NP FL EVER1 0.21 0.00 0.01 0.02 0.09 3.07

Flat Tops Wilderness CO WHRI1 0.09 0.00 0.00 0.00 0.00 0.39

Great Sand Dunes NM CO GRSA1 0.01 0.00 0.00 0.00 0.00 1.36

Great Smoky Mountains NP TN GRSM1 1.32 0.00 0.00 0.00 0.01 5.56

Guadalupe Mountains NP TX GUMO1 0.05 0.00 0.00 0.00 0.00 2.64

Hercules-Glades Wilderness MO HEGL1 0.45 0.00 0.00 0.01 0.02 4.90

James River Face Wilderness VA JARI1 1.10 0.00 0.00 0.01 0.01 4.13

Joyce-Kilmer-Slickrock 

Wilderness TN GRSM1 1.32 0.00 0.00 0.00 0.01 5.56
Air Quality: Cumulative and Visibility Impacts D-135

Source Group Contribution to FY 

DV

Class I Name State IMPROVE 

Site

BY - FY 

DV A B C D E 

La Garita Wilderness CO WEMI1 -0.14 0.00 0.00 0.00 0.00 0.63

Linville Gorge Wilderness NC LIGO1 0.75 0.00 0.00 0.01 0.02 4.36

Maroon Bells-Snowmass 

Wilderness CO WHRI1 0.09 0.00 0.00 0.00 0.00 0.39

Mammoth Cave NP KY MACA1 1.16 0.00 0.00 0.01 0.02 5.63

Mount Zirkel Wilderness CO MOZI1 0.10 0.00 0.00 0.00 0.00 0.79

Okefenokee GA OKEF1 0.51 0.00 0.00 0.01 0.04 5.31

Otter Creek Wilderness WV DOSO1 0.80 0.00 0.00 0.00 0.01 2.75

Pecos Wilderness NM WHPE1 -0.15 0.00 0.00 0.00 0.00 1.24

Rawah Wilderness CO MOZI1 0.10 0.00 0.00 0.00 0.00 0.79

Cape Romain SC ROMA1 0.70 0.00 0.00 0.00 0.01 4.61

Rocky Mountain NP CO ROMO1 0.02 0.00 0.00 0.00 0.00 1.09

Salt Creek NM SACR1 -0.31 0.00 0.00 0.00 0.00 4.53

St. Marks FL SAMA1 0.73 0.01 0.01 0.08 0.25 4.69

San Pedro Parks Wilderness NM SAPE1 -0.07 0.00 0.00 0.00 0.00 0.76

Shenandoah NP VA SHEN1 1.02 0.00 0.00 0.01 0.01 3.10

Shining Rock Wilderness NC SHRO1 0.77 0.01 0.01 0.02 0.02 3.78

Sipsey Wilderness AL SIPS1 0.90 0.00 0.01 0.04 0.07 5.41

Swanquarter NC SWAN1 0.67 0.00 0.01 0.01 0.01 3.64

Upper Buffalo Wilderness AR UPBU1 0.55 0.00 0.01 0.03 0.04 4.77

West Elk Wilderness CO WHRI1 0.09 0.00 0.00 0.00 0.00 0.39

Weminuche Wilderness CO WEMI1 -0.14 0.00 0.00 0.00 0.00 0.63

White Mountain Wilderness NM WHIT1 -0.21 0.00 0.00 0.00 0.00 2.04

Wheeler Peak Wilderness NM WHPE1 -0.15 0.00 0.00 0.00 0.00 1.24

Wichita Mountains OK WIMO1 0.29 0.00 0.00 0.00 0.00 3.88

Wolf Island GA OKEF1 0.51 0.00 0.00 0.01 0.04 5.31

NM = National Monument; NP = National Park.

D.7.3.2 Acid Deposition

The CAMx-predicted wet and dry fluxes of sulfur- and nitrogen-containing species were 

processed to estimate total annual sulfur and nitrogen deposition values at each Class I and 

sensitive Class II area in the 12/4-km modeling domain. As described in Section D.6.2.3.2, the 

maximum annual sulfur and nitrogen deposition values from any grid cell that intersects a Class I or 

sensitive Class II receptor area was used to represent deposition for that area, in addition to the 

average annual deposition values of all grid cells that intersect a Class I or sensitive Class II 

receptor area. Maximum and average predicted sulfur and nitrogen deposition impacts were 

estimated separately for each source group and together across all source groups. 

As a screening analysis, incremental deposition values in Class I/II areas for combined 

Source Groups A (new platforms associated with the 2017-2022 GOM Multisale EIS scenario, from 

which this Supplemental EIS tiers) and B (new platforms and associated support vessels and 
D-136 2018 Gulf of Mexico Supplemental EIS

helicopters associated with the 2017-2022 GOM Multisale EIS scenario, from which this 

Supplemental EIS tiers) were compared to the eastern and western U.S. Deposition Analysis 

Thresholds (DATs) listed in Table D-32. These DATs are specified in the FLAG guidance25 and are 

further described in Section D.6.2.3.2 above. Results of the incremental deposition analysis are 

summarized in Table D-33 for Class I/II areas in the 4-km modeling domain. Deposition results 

were also obtained for all other sensitive areas throughout the 12 km-modeling domain, but the 

highest deposition values all occurred within the 4-km domain. The dividing line between the 

eastern and western DATs specified in the FLAG guidance is the Mississippi River, which makes 

sense for most locations in the U.S. but it is not necessarily clear which DAT would be most 

appropriate for coastal locations along the Gulf of Mexico so results are compared here against both 

DATs. Note that comparisons of deposition impacts from cumulative sources as represented by 

Source Groups C, D, E, and F to the DAT are not appropriate. Incremental nitrogen deposition 

exceeds the western and eastern DATs at all three locations. Incremental sulfur deposition is below 

the DATs in all cases except the sulfur deposition from Source Group B at Breton Wilderness and 

Gulf Islands National Seashore, which exceeds the western DAT but not the eastern DAT. 

Table D-32. Deposition Analysis Threshold Values (kg/ha/yr) as 

Defined in the Federal Land Manager Guidance 

(FLAG, 2010).

Nitrogen Sulfur

East 0.010 0.010

West 0.005 0.005

Table D-33. Incremental Deposition Impacts from Source Groups A and B at Class I and Sensitive 

Class II Areas in the 4-km Domain.

Area

Source Group A Source Group B

Nitrogen Sulfur Nitrogen Sulfur

Max Avg Max Avg Max Avg Max Avg

Breton 

Wilderness 

Annual 

Deposition 0.0589 0.0501 0.0045 0.0039 0.3496 0.2701 0.0079 0.0061

Exceeds 

Eastern DAT? Yes Yes No No Yes Yes No No

Exceeds 

Western DAT? Yes Yes No No Yes Yes Yes Yes

Gulf Islands 

National 

Seashore

Annual 

Deposition 0.0909 0.0383 0.0046 0.0025 0.4560 0.2151 0.0064 0.0039

Exceeds 

Eastern DAT? Yes Yes No No Yes Yes No No

Exceeds 

Western 

DAT?

Yes Yes No No Yes Yes Yes No

 

25 Guidance on Nitrogen and Sulfur Deposition Analysis Thresholds (http://www.nature.nps.gov/air/Pubs/

pdf/flag/nsDATGuidance.pdf).
Air Quality: Cumulative and Visibility Impacts D-137

Area

Source Group A Source Group B

Nitrogen Sulfur Nitrogen Sulfur

Max Avg Max Avg Max Avg Max Avg

Padre 

Island 

National 

Seashore

Annual 

Deposition 0.0458 0.0190 0.0012 0.0010 0.2410 0.1044 0.0019 0.0015

Exceeds 

Eastern DAT? Yes Yes No No Yes Yes No No

Exceeds 

Western DAT? Yes Yes No No Yes Yes No No

Cumulative deposition from all sources combined for the base case and future year 

scenarios were compared against applicable critical load levels in each Class I/II area for which 

critical loads were identified as described in Section D.6.2.3.2. Results are summarized in 

Table D-34. Cumulative nitrogen deposition is projected to decrease in all areas between the 2012 

base case and the 2017 future year, consistent with an overall reduction in NOx emissions. 

Nevertheless, maximum nitrogen deposition is modeled to continue exceeding the critical load 

thresholds under the future year scenario for all areas except the Padre Island National Seashore. 

Sulfur deposition values are lower, and larger sulfur emission reductions help to reduce sulfur 

deposition from above the critical load to below the critical load at Breton Wilderness, Breton 

National Wildlife Refuge, and Cohutta Wilderness (based on maximum grid cell values). 

Nevertheless, the maximum grid cell sulfur deposition still exceeds the critical load at the Gulf 

Islands National Seashore by a small margin.

Table D-34. Cumulative Nitrogen (N) and Sulfur (S) Deposition Impacts (kg/ha/yr) under the Base and 

Future Year Scenarios (shading indicates values exceeding the Critical Load threshold).

Class I/II Area Critical Load 

Threshold

2012 Base Case 2017 Future Year

NMaxNAvgSMaxSAvgNMaxNAvgSMaxSAvg

Big Bend National Park 3 3.6 2.5 2.3 1.1 3.6 2.5 2.2 1.0

Breton Wilderness 3 7.8 7.1 4.1 3.6 7.7 6.9 2.8 2.5

Breton National Wildlife 

Refuge 3 7.2 6.9 3.7 3.5 7.0 6.7 2.6 2.4

Gulf Islands National 

Seashore 3 13.8 7.0 5.3 4.4 13.0 6.7 3.6 2.9

Padre Island National 

Seashore 5 4.5 2.2 1.5 1.2 4.6 2.2 1.1 0.9

Bradwell Bay Wilderness 5 6.5 6.2 2.5 2.3 6.0 5.8 1.8 1.7

Saint Marks National 

Wildlife Refuge 3 6.8 5.2 2.5 2.0 6.2 4.7 1.8 1.5

Saint Marks Wilderness 3 6.1 4.9 2.0 1.9 5.6 4.5 1.5 1.4

Chassahowitzka 

Wilderness 3 6.8 6.1 2.5 2.5 6.0 5.4 1.9 1.9

Everglades National Park 5 7.5 4.7 3.9 2.2 6.9 4.5 2.4 1.7

Okefenokee National 

Wildlife Refuge 3 6.0 5.7 2.3 2.1 5.6 5.3 1.8 1.7

Okefenokee Wilderness 3 6.5 5.5 2.6 2.1 6.1 5.1 2.1 1.7

Wolf Island Wilderness 3 3.3 3.1 2.1 2.0 3.0 2.8 1.5 1.4
D-138 2018 Gulf of Mexico Supplemental EIS

Class I/II Area Critical Load 

Threshold

2012 Base Case 2017 Future Year

NMaxNAvgSMaxSAvgNMaxNAvgSMaxSAvg

Cohutta Wilderness 5 11.5 10.2 5.4 4.3 10.6 9.3 3.6 2.9

Sipsey Wilderness 5 9.4 9.0 3.2 3.2 9.1 8.6 2.1 2.1

Guadalupe Mountains 

National Park 3 3.3 2.6 1.1 0.7 3.2 2.5 0.9 0.6

Wichita Mountains 

(Charons Garden Unit) 

Wilderness

5 5.6 5.6 1.7 1.7 5.4 5.4 1.5 1.5

Wichita Mountains (North 

Mountain Unit) Wilderness 5 6.3 6.3 1.8 1.8 6.1 6.1 1.5 1.5

Wichita Mountains National 

Wildlife Refuge 5 6.5 6.0 1.8 1.7 6.2 5.8 1.5 1.5

Caney Creek Wilderness 5 9.3 9.2 3.7 3.6 9.1 9.0 2.3 2.3

Upper Buffalo Wilderness 5 7.4 7.4 2.5 2.5 7.1 7.1 1.7 1.7

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USEPA. 1991. Guidance for Regulatory Application of the Urban Airshed Model (UAM). U.S. 

Environmental Protection Agency, Office of Air Quality Planning and Standards, Research 

Triangle Park, NC. July. Internet website: http://www.epa.gov/ttn/scram/guidance/guide/

uamreg.pdf. 

USEPA. 2007. Guidance on the Use of Models and Other Analyses for Demonstrating Attainment 

of Air Quality Goals for Ozone, PM2.5, and Regional Haze. EPA-454/B-07-002, U.S. 

Environmental Protection Agency, Research Triangle Park, NC, April.

USEPA. 2014. Draft Modeling Guidance for Demonstrating Attainment of Air Quality Goals for 

Ozone, PM2.5 and Regional Haze. U.S. Environmental Protection Agency, Research Triangle 

Park, NC. December. Internet website: http://www.epa.gov/ttn/scram/guidance/guide/Draft_O3-

PM-RH_Modeling_Guidance-2014.pdf. 

U.S. Environmental Protection Agency. 2016. Ozone designations guidance and data. Internet 

website: https://www3.epa.gov/airquality/greenbook/map8hr_2008.html. Accessed June 2016.

Wilson, D., R. Billings, R. Chang, H. Perez, and J. Sellers. 2014. Year 2011 Gulfwide Emissions 

Inventory Study. U.S. Dept. of the Interior, Bureau of Ocean Energy Management, Gulf of 

Mexico OCS Region, New Orleans, LA. OCS Study BOEM 2014-666.

Yarwood, G., T. Sakulyanontvittaya, O. Nopmongcol, and B. Koo. 2014. Ozone Depletion by 

Bromine and Iodine over the Gulf of Mexico. Final Report prepared for Jocelyn Mellberg, TCEQ. 

November.

Zhang, L., S. Gong, J. Padro, and L Barrie. 2001. A Size-segregated Particle Dry Deposition 

Scheme for an Atmospheric Aerosol Module. Atmos. Environ., 35, 549-560.

Zhang, L., J.R. Brook, and R. Vet. 2003. A Revised Parameterization for Gaseous Dry Deposition 

in Air-quality Models. Atmos. Chem. Phys., 3, 2067-2082.

 

KEYWORD INDEX

Keyword Index Keywords-3 

KEYWORD INDEX

Air Quality, xvii, xviii, xx, xxi, xxviii, xxxvi, xxxvii, 1-10, 1-11, 2-17, 2-18, 2-20, 3-3, 3-4, 3-26, 3-31, 

3-32, 3-33, 3-41, 3-42, 3-50, 4-3, 4-4, 4-10, 4-14, 4-15, 4-16, 4-17, 4-18, 4-19, 4-20, 4-21, 4-22, 

4-25, 4-26, 4-28, 4-30, 4-31, 4-32, 4-33, 4-34, 4-35, 4-36, 4-37, 4-38, 4-39, 4-40, 4-41, 4-42, 4-43, 

4-44, 4-45, 4-46, 4-49, 4-50, 4-51, 4-52, 4-53, 4-54, 4-107, 4-109, 4-172

Alternative Energy, 1-12, 2-13, 4-5 

Archaeological Resources, xvii, xix, xx, xxxiii, 1-10, 2-17, 2-18, 2-20, 2-21, 3-6, 3-27, 4-3, 4-5, 4-149, 

4-150, 4-151, 4-152, 4-153, 4-154, 4-155, 4-174, 4-176

Artificial Reefs, xxxii, xxxiii, 1-10, 1-11, 2-17, 3-25, 3-30, 3-48, 4-109, 4-143, 4-145, 4-147, 4-179

Beach Mice, xi, xvii, xix, xxix, 2-18, 2-20, 4-3, 4-112, 4-113, 4-115, 4-116, 4-130, 4-131, 4-132, 5-16

Blowout Preventer, 3-29

Blowouts, 3-5, 3-29, 3-42, 4-33, 4-153

Catastrophic Spill, xxxv, 1-12, 2-21, 3-35, 4-5, 4-6, 4-8, 4-12, 4-13, 4-32, 4-33, 4-49, 4-72, 4-76, 

4-77, 4-86, 4-91, 4-94, 4-99, 4-117, 4-132, 4-160, 4-168, 4-169, 4-171, 5-12

Chemosynthetic Communities, xxiv, 2-16, 3-6, 4-71, 4-76

Coastal and Marine Birds, xxviii, xxx, 2-21, 4-106, 4-110, 4-134

Coastal Barrier Beaches, xviii, xxiii, 2-18, 2-20, 4-3, 4-65, 4-66, 4-67, 4-68, 4-69, 4-70, 4-117, 4-161

Coastal Zone Management, xvii, 1-10, 1-14, 4-7, 4-9, 4-55, 5-3, 5-18

Collisions, xxix, xxxiv, 3-3, 3-4, 3-32, 3-33, 3-41, 3-42, 3-43, 4-10, 4-107, 4-111, 4-127, 4-128, 4-159, 

4-160, 4-172, 4-174

Commercial Fisheries, xvii, xix, xxxi, 2-18, 2-20, 4-3, 4-4, 4-5, 4-118, 4-139, 4-140, 4-141, 4-142, 

4-174, 4-176

Commercial Fishing, xvii, xix, xxxi, 2-18, 2-20, 4-3, 4-4, 4-5, 4-118, 4-139, 4-140, 4-141, 4-142, 

4-174, 4-176

Consultation and Coordination, 1-12, 1-13, 5-7 

Cumulative Activities, xvi, 1-13, 3-3, 3-4, 3-44, 4-11, 4-79

Cumulative Impacts, xviii, xxi, xxii, xxiii, xxiv, xxv, xxvi, xxvii, xxviii, xxix, xxx, xxxi, xxxii, xxxiii, xxxiv, 

xxxv, 1-8, 1-9, 2-19, 3-4, 3-44, 3-48, 3-50, 4-3, 4-4, 4-7, 4-8, 4-10, 4-12, 4-14, 4-15, 4-25, 4-34, 

4-38, 4-46, 4-49, 4-51, 4-53, 4-54, 4-55, 4-58, 4-59, 4-60, 4-61, 4-62, 4-63, 4-64, 4-65, 4-66, 4-67, 

4-68, 4-69, 4-70, 4-71, 4-72, 4-74, 4-75, 4-78, 4-81, 4-82, 4-84, 4-86, 4-89, 4-90, 4-92, 4-94, 4-95, 

4-96, 4-97, 4-98, 4-100, 4-102, 4-103, 4-104, 4-105, 4-106, 4-107, 4-109, 4-110, 4-113, 4-115, 

4-116, 4-118, 4-120, 4-121, 4-122, 4-125, 4-126, 4-128, 4-129, 4-130, 4-131, 4-132, 4-134, 4-135, 

4-136, 4-138, 4-139, 4-140, 4-141, 4-142, 4-143, 4-144, 4-145, 4-146, 4-147, 4-148, 4-149, 4-150, 

4-152, 4-154, 4-156, 4-158, 4-159, 4-160, 4-161, 4-162, 4-163, 4-164, 4-165, 4-168, 5-8, 5-10
Keywords-4 2018 Gulf of Mexico Supplemental EIS

Decommissioning, xx, xxvii, xxviii, xxxii, xxxiii, 1-7, 1-8, 1-10, 2-14, 2-17, 3-3, 3-4, 3-8, 3-9, 3-14, 

3-23, 3-25, 3-30, 3-41, 3-48, 4-10, 4-14, 4-15, 4-25, 4-28, 4-31, 4-58, 4-87, 4-88, 4-104, 4-115, 

4-120, 4-121, 4-127, 4-145, 4-151, 4-152, 4-174, 4-176, 4-177, 5-4, 5-5 

Deepwater, xvii, xviii, xxiii, xxiv, xxix, 1-11, 1-12, 2-12, 2-16, 2-17, 2-18, 2-20, 2-21, 3-8, 3-23, 3-24, 

3-27, 3-29, 3-31, 3-35, 3-48, 3-50, 3-51, 3-52, 4-3, 4-4, 4-6, 4-9, 4-11, 4-12, 4-14, 4-30, 4-33, 4-37, 

4-43, 4-55, 4-59, 4-63, 4-64, 4-68, 4-69, 4-70, 4-71, 4-72, 4-73, 4-74, 4-75, 4-76, 4-77, 4-82, 4-91, 

4-99, 4-117, 4-122, 4-123, 4-124, 4-125, 4-126, 4-129, 4-169, 4-170, 4-176, 4-178, 5-4, 5-13, 5-15

Deepwater Horizon, xviii, xxiii, xxix, 1-12, 2-12, 2-21, 3-35, 3-51, 4-6, 4-11, 4-12, 4-14, 4-33, 4-59, 

4-63, 4-64, 4-68, 4-69, 4-70, 4-76, 4-77, 4-82, 4-91, 4-99, 4-117, 4-122, 4-123, 4-124, 4-125, 

4-126, 4-129, 4-169, 4-170, 5-4, 5-13, 5-15

Discharges, xvii, xxii, xxiv, xxv, xxvi, xxvii, xxviii, xxx, 3-25, 3-29, 3-30, 3-30, 3-49, 4-10, 4-55, 4-56, 

4-57, 4-58, 4-72, 4-74, 4-79, 4-81, 4-95, 4-96, 4-97, 4-101, 4-107, 4-109, 4-115, 4-121, 4-134, 

4-153, 4-172, 4-173

Dispersants, xxii, 3-33, 3-40, 3-43, 4-34, 4-59, 4-76, 4-90, 4-98, 4-154, 4-172, 4-173, 4-174

Dunes, xvii, xviii, xxiii, xxix, 2-18, 2-20, 4-3, 4-65, 4-66, 4-67, 4-68, 4-69, 4-70, 4-117, 4-130, 4-131, 

4-161

Economic Factors, xix, xxxii, xxxiii, xxxv, 2-18, 2-20, 4-3, 4-142, 4-145, 4-147, 4-162, 4-163, 4-164, 

4-165

Employment, 4-158, 4-163, 4-165, 4-166

Environmental Justice, xi, xvii, xix, xxxiv, xxxv, xxxvi, 2-18, 2-19, 2-20, 4-3, 4-4, 4-165, 4-170, 4-171, 

5-8, 5-16

Essential Fish Habitat, 1-12, 4-5, 4-7, 4-83, 4-147, 5-3, 5-5 

Explosive Removals, 2-17

Fisheries, xxix, xxxi, xxxii, 2-17, 2-21, 3-48, 3-50, 4-8, 4-83, 4-102, 4-103, 4-111, 4-128, 4-139, 

4-140, 4-142, 4-143, 4-145, 5-5, 5-8, 5-11, 5-17, 5-18, 5-19

Flaring, xx, 1-10, 3-28, 3-31, 3-50, 4-14, 4-15, 4-25, 4-26, 4-28, 4-30, 4-31, 4-32, 4-49

Flower Garden Banks, xi, xiii, xxxi, 1-12, 2-5, 2-8, 2-12, 2-17, 4-85, 4-91, 4-92, 4-136, 4-138

Gulf Sturgeon, 4-102

Human Resources, xix, xxxiv, 2-18, 2-20, 4-5, 4-156

Hurricanes, xvii, xviii, xxxii, 3-24, 3-29, 3-32, 3-52, 4-6, 4-50, 4-125, 4-142, 4-145

Income, xxxvi, 4-145, 4-163, 4-165, 4-170, 4-171, 5-7, 5-8 

Infrastructure, xvi, xviii, xix, xxvii, xxxiii, xxxiv, xxxvi, 1-13, 2-11, 2-18, 2-20, 3-3, 3-4, 3-7, 3-11, 3-17, 

3-18, 3-19, 3-21, 3-25, 3-26, 3-27, 3-28, 3-31, 3-32, 3-42, 3-45, 3-48, 3-50, 4-3, 4-9, 4-10, 4-12, 
Keyword Index Keywords-5 

4-13, 4-26, 4-50, 4-61, 4-62, 4-66, 4-67, 4-76, 4-102, 4-104, 4-107, 4-152, 4-156, 4-158, 4-159, 

4-160, 4-161, 4-162, 4-171, 4-172, 4-178

Land Use, xvii, xix, xxxiv, 2-18, 2-20, 3-53, 4-3, 4-4, 4-5, 4-156, 4-157, 4-158, 4-159, 4-160, 4-161, 

4-162

Live Bottoms, xi, xiv, xvi, xvii, xix, xxiv, xxv, xxvi, xxxi, xxxii, 2-3, 2-9, 2-10, 2-11, 2-14, 2-15, 2-18, 

2-20, 4-3, 4-5, 4-9, 4-54, 4-71, 4-76, 4-83, 4-84, 4-85, 4-90, 4-91, 4-92, 4-93, 4-94, 4-95, 4-97, 

4-98, 4-99, 4-112, 4-113, 4-116, 4-136, 4-137, 4-138, 4-139, 4-143, 5-16

Loss of Well Control, 3-3, 3-4, 3-32, 3-40, 3-42, 4-10, 4-33

Low Relief, xix, xxvi, 2-18, 2-20, 4-3, 4-92, 4-93, 4-94, 4-95, 4-96, 4-97, 4-98, 4-99

Macondo, 4-33

Marine Mammals, xi, xvii, xix, xxviii, 2-17, 2-18, 2-20, 4-3, 4-7, 4-111, 4-112, 4-113, 4-115, 4-118, 

4-119, 4-120, 4-121, 4-122, 4-123, 4-124, 4-125, 4-126, 4-127, 4-173, 4-174, 5-16, 5-17, 5-19, 

5-20

Mercury, 4-56

Mitigating Measures, xi, xv, xvi, xxii, xxiii, 1-10, 1-11, 1-13, 2-3, 2-4, 2-5, 2-11, 2-12, 2-13, 2-14, 2-15, 

2-16, 2-17, 4-9, 4-59, 4-62, 4-68, 4-119, 4-178, 5-5, 5-10

Mitigation, xvi, xx, xxi, xxiv, xxvi, xxix, xxxi, xxxiii, 1-3, 1-11, 1-13, 2-13, 2-14, 2-15, 2-16, 2-17, 2-19, 

2-21, 4-8, 4-9, 4-15, 4-16, 4-34, 4-51, 4-52, 4-53, 4-54, 4-57, 4-58, 4-71, 4-73, 4-74, 4-75, 4-76, 

4-84, 4-86, 4-88, 4-89, 4-90, 4-93, 4-94, 4-95, 4-96, 4-97, 4-98, 4-107, 4-117, 4-119, 4-120, 4-127, 

4-128, 4-131, 4-137, 4-138, 4-152, 4-153, 4-154, 4-155, 4-161, 4-172, 4-176, 4-179, 5-5, 5-8, 5-10

NEPA, vii, viii, x, xxi, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-9, 1-11, 1-12, 1-13, 2-3, 2-4, 2-14, 2-15, 2-16, 

2-18, 2-21, 3-45, 4-4, 4-5, 4-6, 4-7, 4-10, 4-11, 4-13, 4-21, 4-59, 4-64, 4-70, 4-94, 4-99, 4-105, 

4-117, 4-120, 4-121, 4-122, 4-123, 4-125, 4-150, 4-154, 4-170, 4-171, 5-3, 5-5, 5-9, 5-10, 5-13, 

5-14, 5-16

Noise, xxvii, xxviii, xxix, xxx, 3-26, 3-31, 3-50, 4-10, 4-107, 4-109, 4-116, 4-121, 4-127, 4-128, 4-134, 

4-173

NRDA, 4-11, 4-64, 4-69, 4-123, 4-124, 4-129, 4-169

Oil Spills, xvii, xviii, xx, xxii, xxiii, xxiv, xxv, xxvi, xxvii, xxviii, xxix, xxx, xxxii, xxxiii, xxxiv, xxxv, 1-12, 

2-12, 2-21, 3-3, 3-4, 3-32, 3-33, 3-34, 3-35, 3-36, 3-37, 3-41, 3-42, 3-43, 3-49, 3-51, 4-6, 4-8, 4-10, 

4-11, 4-12, 4-14, 4-15, 4-25, 4-31, 4-33, 4-34, 4-50, 4-58, 4-59, 4-61, 4-62, 4-63, 4-64, 4-66, 4-67, 

4-68, 4-69, 4-72, 4-74, 4-76, 4-77, 4-79, 4-81, 4-82, 4-86, 4-87, 4-89, 4-90, 4-94, 4-95, 4-96, 4-97, 

4-101, 4-103, 4-107, 4-109, 4-110, 4-116, 4-117, 4-122, 4-123, 4-124, 4-125, 4-126, 4-128, 4-129, 

4-131, 4-134, 4-141, 4-144, 4-145, 4-147, 4-148, 4-153, 4-154, 4-159, 4-160, 4-168, 4-169, 4-170, 

4-172, 4-173, 4-174, 4-175, 4-176, 4-178, 5-4, 5-12, 5-13, 5-14, 5-15

OSRA, 3-33, 3-35, 3-42, 4-121, 4-132
Keywords-6 2018 Gulf of Mexico Supplemental EIS

PDARP/PEIS, 1-12, 4-6, 4-11, 4-91, 4-99, 4-117, 4-123, 4-130

Physical Oceanography, 3-52, 4-155

Pinnacle Trend, xiv, xv, xvi, xvii, xxvi, 2-3, 2-9, 2-10, 2-14, 2-15, 4-9, 4-54, 4-84, 4-90, 4-93, 4-95, 

4-97, 4-98

Pipelines, xi, xvii, xxii, xxiii, xxvii, xxix, xxxiii, xxxvi, 1-11, 2-15, 2-16, 2-17, 2-18, 2-19, 3-3, 3-4, 3-6, 

3-7, 3-9, 3-10, 3-13, 3-14, 3-17, 3-19, 3-23, 3-24, 3-25, 3-27, 3-28, 3-28, 3-29, 3-30, 3-31, 3-32, 

3-33, 3-35, 3-36, 3-37, 3-38, 3-39, 3-40, 3-41, 3-42, 3-45, 3-46, 3-48, 3-50, 3-51, 4-9, 4-10, 4-12, 

4-13, 4-26, 4-32, 4-50, 4-56, 4-58, 4-60, 4-62, 4-64, 4-66, 4-67, 4-68, 4-71, 4-107, 4-109, 4-131, 

4-152, 4-154, 4-171, 4-173, 4-174, 4-175, 4-176, 5-11, 5-16, 5-17

Produced Waters, 4-172

Recreational Fishing, xvii, xix, xxvii, xxxii, xxxiii, 2-18, 2-20, 3-48, 3-50, 4-3, 4-5, 4-104, 4-143, 4-144, 

4-145, 4-146, 4-147, 4-174, 4-176, 4-178

Recreational Resources, xvii, xix, xxxii, xxxiii, 2-18, 2-20, 4-3, 4-4, 4-5, 4-146, 4-147, 4-148, 4-149, 

4-174

Renewable Energy, xi, 2-13, 2-19, 3-31, 3-50, 4-177, 5-16

Resource Estimates, xvi, 1-13, 2-6, 2-8, 3-10, 3-35, 3-36, 3-37

Sargassum, xvii, xviii, xxv, 2-18, 2-20, 4-3, 4-5, 4-77, 4-78, 4-79, 4-80, 4-81, 4-82, 4-83, 4-112, 

4-173

Sea Turtles, xi, xvii, xix, xxix, 2-12, 2-17, 2-18, 2-20, 4-3, 4-112, 4-115, 4-119, 4-126, 4-127, 4-128, 

4-129, 4-130, 5-14, 5-16

Seagrass Communities, 4-60, 4-61

Service Base, 3-7, 3-24, 3-29, 3-30, 4-160

Site Clearance, xxxiii, 1-10, 2-16, 3-8, 3-30, 4-154, 4-174

Smalltooth Sawfish, 4-102

Soft Bottoms, xxiv, xxvi, 3-48, 4-71, 4-83, 4-85, 4-93

Stipulation, xi, xiv, xv, xvi, xx, xxv, xxvi, xxix, xxxi, 1-11, 1-13, 2-3, 2-5, 2-9, 2-10, 2-11, 2-14, 2-15, 

2-16, 2-21, 3-50, 4-8, 4-9, 4-13, 4-54, 4-83, 4-84, 4-85, 4-86, 4-89, 4-90, 4-93, 4-94, 4-97, 4-113, 

4-116, 4-119, 4-120, 4-122, 4-126, 4-127, 4-128, 4-131, 4-136, 4-137, 4-138, 4-176

Submerged Vegetation, xxii, 4-60, 4-61, 4-63

Synthetic-Based Drilling Fluids, 3-32, 3-43

Topographic Features, xiv, xv, xvi, xvii, xix, xxv, xxvi, 2-3, 2-9, 2-10, 2-11, 2-14, 2-15, 2-16, 2-17, 

2-18, 2-20, 4-3, 4-9, 4-54, 4-63, 4-69, 4-83, 4-84, 4-85, 4-86, 4-87, 4-88, 4-89, 4-90, 4-91, 4-92, 

4-93, 4-94, 4-98, 4-116, 4-136, 4-137, 4-138
Keyword Index Keywords-7 

Tourism, xxiii, 3-50, 4-63, 4-68, 4-147, 4-178, 5-7, 5-18

Trash, xvii, 3-33, 3-43, 3-49, 4-66, 4-116, 4-119, 4-127, 4-131, 4-133, 4-173, 4-174

Waste Disposal, 3-7, 3-19, 4-107, 4-159, 4-160

Wastes, xxii, xxvii, xxx, 2-18, 3-25, 3-29, 3-30, 3-41, 3-43, 3-49, 4-10, 4-56, 4-57, 4-58, 4-61, 4-62, 

4-67, 4-107, 4-109, 4-134

Water Quality, xvii, xviii, xxii, xxv, xxx, 2-18, 2-20, 3-29, 4-3, 4-4, 4-55, 4-57, 4-58, 4-59, 4-60, 4-81, 

4-91, 4-92, 4-102, 4-115, 4-134, 4-172, 4-174, 4-179

Wetlands, xi, xvii, xxii, xxxiii, 2-17, 2-19, 2-21, 3-51, 3-52, 4-8, 4-60, 4-61, 4-62, 4-63, 4-64, 4-65, 

4-70, 4-107, 4-133, 4-147, 4-173, 4-175, 4-179, 5-8, 5-10, 5-11, 5-16


The Department of the Interior Mission

The Department of the Interior protects and manages the Nation’s natural 

resources and cultural heritage; provides scientific and other information 

about those resources; and honors the Nation’s trust responsibilities or 

special commitments to American Indians, Alaska Natives, and affiliated 

island communities.

The Bureau of Ocean Energy Management Mission

The Bureau of Ocean Energy Management (BOEM) is responsible for 

managing development of U.S. Outer Continental Shelf energy and mineral 

resources in an environmentally and economically responsible way.